“Integral systems block the passage of water from both the positive and negative sides by working from within the concrete.
Concrete by its very nature is porous. Any water absorbed into unprotected concrete can cause reinforcing steel corrosion and concrete spalling – Idevastating long-term effects to both the durability and structural integrity of a structure. The answer to designers, engineers and contractors perpetual headache is simple: keep the water out of the concrete. The solution is not as complicated as some may fear.” – Gary Penk, Kryton International
There are three options. Concrete can be waterproofed from the positive (wet/exterior) side, negative (dry/ interior) side or from within the concrete itself (integral systems). The oldest and most widely used method is positive-side waterproofing using sheet membranes but its failures and limitations are common and costly. Integral systems block the passage of water from both the positive and negative sides by working from within the concrete. This technology, which dates back to the early 1900s, has undergone many improvements and developments over the last 30 years. It is now a highly effective, time-saving and cost-saving technology to use in place of traditional membrane systems.
Integral crystalline waterproofing is most often a dry powder mix of Portland cement, fine silica sand and a specific (and usually proprietary) blend of chemicals. It is either an admixture added to ready-mixed concrete at the time of batching for in-situ pours or sprayed concrete applications, or a surface-applied mixture used for existing structures. Surface-applied crystalline waterproofing formulas are brushed or sprayed onto existing structures as a slurry coating or spread over and trowelled into freshly poured concrete slabs as a dry-shake treatment.
When the blend of chemicals comes into contact with water, as it inevitably does, long narrow crystals grow within the concrete. These block the movement of water by filling the natural pores, capillaries and hairline cracks in concrete. Instead of forming a barrier on the positive or negative side of your concrete, they turn the concrete itself into a water harrier.
The advantages of this solution:
Two types of integral crystalline waterproofing
Close-up of Krystol grout, part of the Krystol KWS system being installed at five blocks high.Most integral waterproofing systems are compounds that either increase the density of the concrete or increase its ability to repel water. As these systems work to repel water, they are ‗hydrophobic‘. Although hydrophobic systems may perform satisfactorily for damp-proofing, they can‘t reliably resist liquid under hydrostatic pressure and have limited to no ability to reactivate and self-seal f u t w cracks and leaks. In contrast, hydrophilic systems actually use available water to grow crystals within the concrete – effectively shutting off pathways for moisture that can damage concrete.
Hydrophilic technology, such as Kryton International‘s Krystol Waterproofing System, has distinct advantages over other crystalline products:
Kryton‘s Krystol line includes Krystol Internal Membrane (KIM), an admixture for new concrete. It also includes Krystol T1 and T2 surface-applied slurry system for existing concrete and Krystol Broadcast dry-shake system for concrete flatwork. Krystol systems have also been developed for repairing cracks, holes and water-proofing concrete construction joints, tie-holes and pipe penetrations.
KIM has received an Agrément Certificate from the British Board of Agrément stating that KIM provides watertight concrete, enhances concrete durability, improves protection against corrosion of reinforcing steel and is safe for use in potable water applications such as reservoirs, culverts and other similar structures. It was approved by the British Drinking Water Inspectorate to ensure the product does not contain or produce toxic materials that would make water unsafe for human consumption.
Many traditional waterproofing methods use petroleum- based membranes or coatings on the concrete surface that require adhesives with highly volatile organic compounds. Oil from membranes can leach out and contaminate ground water. Vapour from the compounds can cause respiratory problems and contribute to ‗sick building syndrome‘. However, hydrophilic and hydrophobic crystalline waterproofing is environmentally friendly. Crystalline waterproofing is a non-toxic, non-flammable, odourless product, and crystalline-treated concrete can also be recycled, unlike membrane-coated concrete.
London City Hall
Located on the south bank of the River Thames and next to Tower Bridge, London City Hall is a state-of-the-art building with a series of underground concrete tunnels and transformers room that were constructed using conventional membrane waterproofing systems. Leaks soon occurred through the concrete to allow room for service pipes, also leaked due to the high water pressure of the River Thames. In 2001, before City Hall opened, the Krystol concrete waterproofing system was chosen for repairing cracks, joints and holes in concrete. It was applied from the inside against the water pressure to eliminate water entry. The drilled holes for the service pipes were filled with Krystol Bari-cote, followed by a slurry application of Krystol T1 and T2 to stop all water from entering the service rooms. By the time City Hall opened in 2002, the building was watertight.
Manchester contractor Westshield chose KIM for its latest private residential development at Bowdon near Altrincham. The team needed a product that would be suitable for a below-grade structure that was to be built using the Amvic ICF (insulating concrete formwork) wall system and specifications outlined by the purchaser. KIM was chosen to treat the concrete for the lift pit, car lift, ground floor slab (split pour), walls of the basement and the attached ground floor level swimming pool retaining structure. In total, around 170 cu m of KIM treated concrete was placed in conjunction with approximately 200m of Krystol Waterstop System. Using Kryton in the basement meant that Westshield did not have to over-excavate the site in order to apply an external tanking membrane – they could take advantage of all the space available to them. In addition, once the ground floor was in place, they could backfill with confidence that their structure was 100% waterproof. Completion on the home is expected before the end of 2009.
Protecting Structure………… Naturally!!
Hydronil International is the branded manufacturer for cutting edge crystalline waterproofing systems, with a focus on a unique ―Multiguard In-depth Crystalline Therapy‖ commonly referred to as ―MICT‖. The name of Hydronil is synonymous with watertight concrete! Concrete structures treated with Hydronil’s MICT based products are healthier, more sound and resistant to corrosive chemicals including water and waterborne contaminants. In the end, what we get is a highly durable structure.
What Hydronil is all about? Hydronil is about quality hydrophilic crystalline technologies that assure a watertight concrete. Treatments with Hydronil technologies begin as a surface applied slurry, dry shake, or as an admixture and work as a catalyst to create a reaction between un-hydrated cement particles and water within the concrete. This reaction over time creates billions of pin like crystals to fill the pores and capillaries. The process will continue as long as water and cement particles are present.
Multiguard In-depth Crystalline Therapy (MICT)
Hydronil’s MICT concrete therapy is an excellent remediation procedure for revitalizing water-damaged concrete and to provide an effective protection against the deterioration of healthy concrete due to water ingress.
It is a physical treatment to the entire concrete structure to create a catalytic reaction within the concrete matrix resulting in a stronger, more durable and waterproof concrete. Hydronil´s therapy can be used as a preventative safeguard or as a cure. It will increase the durability of the concrete, autogenously heal micro cracking, and eliminate the need for any other waterproofing system.
There is no need to allocate extra time for Multiguard In-depth Crystalline Therapy, hence projects are completed much in advance and there is a complete savings in waterproofing cost. As the Multiguard In-depth Crystalline Therapy occurs within the body of concrete, treatment can be done from negative or positive side of water pressure.
There is no need to provide extra space for application of MICT outside the structure, which ultimately saves excavation cost.
What Hydronil is all about?
Hydronil is about quality hydrophilic crystalline technologies that assure a watertight concrete. Treatments withHydronil technologies begin as surface applied slurry, dry shake, or as an admixture and work as a catalyst to create a reaction between un-hydrated cement particles and water within the concrete. This reaction over time creates billions of pin like crystals to fill the pores and capillaries. The process will continue as long as water and cement particles are present.
What is Multiguard In-depth System?
Multiguard In-depth System is a revolutionized protection system for concrete structures, concrete blocks and cement-sand rendered brickwork. It is a blend of special Portland cement, a group of active ingredients and surface treated quartz. The system is either applied by brush, spray, sprinkled or directly added into green concrete. Multiguard In-depth System thrives on moisture for migrating into the body of the concrete and generating billions of pin like crystals (see photo 1) sealing all capillaries and voids.
Multiguard In-depth System offers many other benefits to concrete structures:
There are many ways to benefit by treating concrete with Multiguard In-depth System and MICT.
Need of Waterproofing
Contrary to common belief, concrete itself is a complex composite material. It has low strength when loaded in tension and hence it is common practice to reinforce concrete with steel, for improved tensile mechanical properties. Concrete structures such as bridges, buildings, elevated highways, tunnels, parking garages, offshore oil platforms, piers and dam walls all contain reinforcing steel (rebar). The principal cause of degradation of steel reinforced structures is corrosion damage to the rebar embedded in the concrete.
POROSITY IN CONCRETE
When most of us think about concrete, we consider it to be an impenetrable barrier. What most of us don’t realize, however, is that concrete is actually a very porous material by nature that will allow moisture to pass through it readily. Or we may call it ‗Hard Sponge‘.
Imagine: Average pore size in concrete is 1,000 -10,000 nm where as the diameter of water molecule is only 0.28 nm! The average pore in concrete is at least 3,571.42 times larger than the diameter of a water molecule!
Concrete‘s porosity has a strong correlation with the water/cement ratio (W/C) but also depends on curing practice, the rheology characteristics of fresh concrete, the mix design etc. It‘s not only the pores percentage that counts but also pores sizes, pores distribution and the interconnections between the pores. It‘s logical to observe that concrete durability is closely linked to water intrusion and movement rates. Furthermore, water inside concrete‘s mass plays the role of the carrier for harmful substances that can potentially have deleterious effects on the concrete and its steel reinforcements.
Water movement inside the concrete has to do with its permeability which is closely related to the total porosity and its distribution in the cementitious matrix of concrete. The building envelope when in contact with water, it absorbs varied degree of amount of water depending on its porosity.
The mechanisms of water uptakes by building materials are as varies as the possible damages it causes to the building.
NEED OF WATERPROOFING
There are many reasons to waterproof concrete. They include health, cost effectiveness, structural integrity, reduced opportunity costs, usage purposes, visual appeal, and to increase the life of a concrete structure.
Here are some of the common problems associated with humidity and moisture ingress;
While the above listed humidity and moisture problems are commonly understood, what many fail to understand is how the long term costs and problems associated with water ingress into their structures can be prevented through effective waterproofing through crystalline technology.
Water ingress is a major contributor to many of the concrete related problems that cause deterioration of concrete within concrete structures. These include corrosion, chlorides, carbonization, alkali-silicate reaction, freeze/thaw, and chemical attack.
1 Water Ingress and Corrosion
The two most common causes of reinforcement corrosion are (i) localized breakdown of the passive film on the steel by chloride ions and (ii) general breakdown of passivity by neutralization of the concrete, predominantly by reaction with atmospheric carbon dioxide. Sound concrete is an ideal environment for steel but the increased use of deicing salts and the increased concentration of carbon dioxide in modern environments principally due to industrial pollution, has resulted in corrosion of the rebar becoming the primary cause of failure of this material. The scale of this problem has reached alarming proportions in various parts of the world.
Corrosion deterioration in concrete normally occurs due to an electrical reaction caused by exposure of the reinforcing steel to oxygen and moisture. When the iron in the steel oxidizes, it expands, and causes tensile stress in the concrete until eventually the concrete cracks or spalls. As the cracks and spalls begin to occur increased amounts of water and oxygen access the reinforcing steel increasing the rate of corrosion and accelerating the deterioration effects. Stopping water ingress will also stop the effects of corrosion on the reinforcing steel thereby preventing tensile stress cracks and spalling.
2 Water Ingress and Chlorides
In 1962, it was reported that the required minimum concentration of chloride in the concrete immediately surrounding the steel to initiate corrosion, the chloride corrosion threshold, is 0.15% soluble chloride, by weight of cement. In typical bridge deck concrete with a cement factor of 7, this is equivalent to 0.025% soluble chloride, by weight of concrete, or 0.59 kg soluble chloride per cubic meter of concrete. Subsequent research at FHWA laboratories estimated the corrosion threshold to be 0.033% total chloride, by weight of concrete.
There are indications that the chloride corrosion threshold can vary between concrete in different bridges, depending on the type of cement and mix design used, which can vary the concentrations of tricalcium aluminate (C3A) and hydroxide ion (OH-) in the concrete. In fact, it has been suggested that because of the role that hydroxide ions play in protecting steel from corrosion, it is more appropriate to express corrosion threshold in terms of the ratio of chloride content to hydroxide content, [Cl-] / [OH-], which was recently established to be between 2.5 to 6.
When a concrete structure is often exposed to, salt splashes, salt spray, or seawater, chloride ions from these will slowly penetrate into the concrete, mostly through the pores in the hydrated cement paste. The chloride ions will eventually reach the steel and then accumulate to beyond a certain concentration level, at which the protective film is destroyed and the steel begins to corrode, when oxygen and moisture are present in the steel-concrete interface. Even high alkalinity will have minimal abilities to reduce deterioration. If water ingress is stopped even cast in chlorides will not deteriorate the concrete.
3 Water Ingress and Carbonization
Corrosion can also occur even in the absence of chloride ions. Carbonization is a chemical reaction between carbon dioxide in the air and the calcium hydroxide in the hydrated cement paste and with the presence of moisture reduces the pH of the concrete through the creation of carbonic acid. Over time this process will lower the pH as low as 8.5 of the concrete thereby permitting corrosion of the embedded steel. By stopping water ingress the effects of carbonization can be dramatically reduced.
4 Water Ingress and Alkali Silica Reaction/ Alkali Aggregate Reaction
ASR (Alkaline Silica Reaction) or AAR (Alkaline Aggregate Reaction) are basically a reaction that occurs when alkaline contaminated aggregates and moisture ingress cause an expanding gel to form around the cast in aggregates in the concrete. The expansion of the aggregates causes cracking and spalling of the concrete and the entry of more moisture ingress. Stopping water ingress can stop the expansion process of the silicate reaction formed around the gel and prevent expansion of the gel formed around the aggregate thereby preventing cracking and spalling.
Multiguard In-depth Crystalline waterproofing is a very interesting and promising concept and it will surely draw more and more attention in the future as the relevant technology makes leaps.
Enjoyment of life, environmental protection and global fairness are the salient criteria of the Green Lifestyle. Hydronil‘s MICT is a perfect fit for green chemistry.
Green chemistry encompasses the fundamentals of two significant trends: Healthiness and sustainability. All our products, technologies and activities are based on the principal of sustainable development, achieving a sensible balance between economics, ecological and social development without compromising the opportunity of future development.
As a global player, we are very much aware of our social responsibility and the respect that we owe both our employees and our neighbours. Life, environment, company, products, the sustainability philosophy of Hydronil extents across all these aspects.
Concrete waterproofing is a process of making concrete surfaces, such as slabs, walls, floors, etc, water-resistant. Various methods and materials are used in this kind of waterproofing. Ads by Google.
Waterproof Your Terrace With Dr.Fixit Newcoat Register Now for a Free Check-Up! www.doctor-fixit.com/newcoat/index.aspx Concrete by itself is not waterproof in nature, it is porous. Water seepage through concrete may cause damage to the construction leading to money losses, besides other inconveniences. Thus, waterproofing the concrete is a must.
What is Concrete?
It is a construction material composed of cement, water, aggregates, reinforcing materials, chemical and mineral admixtures. The aggregates include sand and gravel, while the reinforcing material is mostly the metal bars. Glass and plastic fibers can also be used as reinforcements. Chemical admixtures add special characteristics to the plain concrete. Mineral admixtures are added to the concrete to improve its strength. These can also be used as a replacement to Portland cement present in the concrete. Let us find more about the water proofing systems and related concepts.
The two important systems in these are Integral Waterproofing System and the other that uses membranes. Hydrophilic system and hydrophobic system are the subtypes of the Integral Waterproofing System. Among different hydrophilic waterproofing systems, crystalline technology is the most popular one. In this method, the water present in concrete is converted into insoluble crystals. Some hydrophilic waterproofing products make use of a property called hydraulic swelling. Here, the waterproofing material swells as it absorbs water, eventually filling pore spaces present in the concrete. In the hydrophobic system, externally applied products viz. coatings, membranes, etc, are used as a protection against water.
Waterproofing membranes are either liquid or sheet membranes. The liquid membranes are sprayed on the concrete, forming a rubber-like coating about 60 mm thick on the concrete surface. Quick application and low pricing are its major advantages. The sheet membranes are prepared from asphalt. These membranes are laminated to polythene films and the sheets thus formed are then pasted onto the concrete. The sheets are consistent in thickness. Excellent waterproofing can be provided to foundation walls, parking lots, tunnels, etc, using these sheet membranes. As the sheets need to be manually pasted, it raises the labor cost which proves to be its main disadvantage.
Unlike the hydrophobic membranes, ‘hydrophobic concrete’ is totally a different and innovative concept. Instead of applying any external agent for concrete waterproofing, here the concrete itself is manufactured waterproof. The concrete is made hydrophobic by adding admixtures to it at the time of production. These admixtures stop capillary action occurring in the concrete, thereby making it waterproof. This kind of concrete has been successfully used in Asia, Europe and Australia. It has also proved to be a boon for construction teams, since it allows construction to carry on even in the rains.
Let’s see how this technology can be used as an option to Integral Waterproofing System. First of all, the concrete which has to be waterproofed is saturated with water and then a low density solution is applied, followed by the crystalline waterproofing material, which is a high density solution. After this, the chemical diffusion process starts. The high density crystalline waterproofing solution seeps inside the concrete and travels towards the low density solution until an equilibrium is attained. Since water is applied to the concrete, cement hydration occurs. This hydrated cement now reacts with the crystalline material to form crystals inside the concrete. The diffusion process may take this crystalline waterproofing 12 inches inside the wall. This waterproofing is highly efficient, because crystals that are formed within the concrete remain protected from any kind of external damage. Resistance to 130 degree heat in a constant state is another advantage of this kind of waterproofing. It also resists chemical reactions like carbonation – which reduces alkalinity and damages the concrete. It stops chloride ion diffusion in the wall, protecting the steel present in the concrete from oxidation and also expansion.
Before You Start
Before one starts the waterproofing process, it is necessary to take into consideration some important points. The concrete surface should be clean. Any kind of debris, honeycombs, etc, should be removed. Rough surfaces should be smoothened, and holes need to be patched up. Check if the waterproofing material is compatible with the substance used for patchwork, so as to avoid any harmful chemical reactions. Some of the products used for waterproofing are flammable and due care should be taken while handling them.
Following these cautions will help in making waterproofing a safe activity, that will strengthen your house in the best way possible. Read more at Buzzle: http://www.buzzle.com/articles/concrete-waterproofing.html
Going beyond surface treatments to reduce concrete permeability.
Water is essential to concrete production, placement, and curing. But once it fulfills its role in those processes, water is no longer concrete‘s friend. Depending on its function and the nature of its exposure, concrete can of course perform well in wet environments. As a naturally porous material, though, and one that is prone to cracking, concrete is vulnerable to water infiltration. The unfortunate results can be freeze/thaw damage and deterioration due to corrosion of embedded steel reinforcement.
Any number of products and systems are available to help protect concrete structures from damage due to water, from coatings to sealers to membranes and more. Enormous amounts of effort and money are spent to design and apply such protection, with varying degrees of effectiveness.
One method that can simplify the protective process is to make concrete with admixtures that reduce its permeability—in effect to make the concrete itself waterproof. A variety of such admixtures are now on the market, and ACI Committee 212, Chemical Admixtures, offers some guidance on their use in its 2010 revision of ACI 212.3 ―Report on Chemical Admixtures for Concrete.‖
Chapter 15 of that report covers permeability-reducing admixtures (PRAs) and differentiates between those suitable for concrete exposed to nonhydrostatic conditions (PRAN) and concrete exposed to hydrostatic conditions (PRAH). Besides reducing permeability, some PRAs impart other beneficial characteristics, such as reduced drying shrinkage, reduced chloride-ion penetration, improved freeze/thaw resistance, and enhanced autogenous sealing.
6 Three types of PRAs
The materials used to produce PRAs vary, but they generally fall into three categories. The largest category consists of hydrophobic, or water-repellent, chemicals derived from soaps or fatty acids, vegetable oils, and petroleum. These materials form a water-repellent layer along pores in the concrete, but the pores themselves remain open.
The second category is finely divided solids—either inert or chemically active fillers such as talc, clay, siliceous powders, hydrocarbon resins, and coal-tar pitches. These materials densify the concrete and physically limit the passage of water through the pores. Some experts also consider supplementary cementitious materials (SCMs) to be in this category.
The third category consists of crystalline products—proprietary active chemicals in a carrier of cement and sand. These are hydrophilic materials that increase the density of calcium silicate hydrate or generate crystalline deposits that block concrete pores to resist water penetration. The various types of materials can be used alone or in combination to give different levels of performance.
According to the ACI report, concrete produced with hydrophobic chemical admixtures could theoretically resist some hydrostatic pressure. However, because the hydrophobic material does not uniformly coat all pores and because the concrete also contains larger voids, such products are not typically classified as PRAHs.
There are also some latex-polymer admixtures that can resist hydrostatic pressure, but they can‘t bridge cracks in concrete and thus don‘t produce truly watertight concrete structures. These admixtures are sometimes added to repair mortars, but are not typically used in ready-mixed concrete.
It is the hydrophilic crystalline admixtures that provide concrete with the greatest resistance to infiltration of water under hydrostatic pressure. Their active ingredients react with water and cement particles to form calcium silicate crystals that integrally bond with the cement paste. These crystalline deposits block both pores and micro cracks in the concrete, to prevent the passage of water. This reaction continues over the life of the concrete, serving to seal not only initial shrinkage cracks, but also cracks that occur over time.
Table 1, reproduced from ACI 212.3, summarizes results from a series of permeability tests performed on concrete mixes with and without three different types of PRAs. Note that these results only indicate the reduction in permeability between the reference and test concrete for each admix type. They can‘t be used to directly compare the different admix technologies because the reference concrete mix for each type was different.
When to use them
In theory, a PRA could be added to any concrete mix without adverse effects, but it‘s not usually necessary in practice. The value of a PRA depends entirely on the environment the concrete will be exposed to and the importance of keeping water from passing through. For interior columns, beams, and floor slabs in a high-rise, permeability isn‘t a big issue. On the other hand, for structures that will be exposed to moisture, salt or salt water, wicking, or water under hydrostatic pressure, using a PRA can help prevent problems such as water migration, leaks, freeze/thaw damage, corrosion, carbonation, and efflorescence.
PRANs are often used in architectural concrete, precast panels, and concrete brick, block, and pavers to repel rain and minimize dampness. Reducing permeability can help minimize efflorescence and make it easier to keep walls clean.
PRAHs are needed for more extreme and continuous exposures, such as below-grade structures, tunnels and subways, water tanks and pools, bridges, and dams. Manufacturers of the crystalline PRAHs say the products can eliminate the need for membrane waterproofing systems and epoxy-coated reinforcement, thereby reducing the cost of waterproofing.
How to use them
Like other admixtures, PRAs are typically specified by the architect or engineer and added to the concrete at the ready-mix plant. Greg Maugeri, head of New England Dry Concrete, which distributes Kryton‘s line of PRAHs in the northeastern U.S., describes the process: ―We market to ready-mix companies, but part of our role is to educate designers and applicators about the product. We‘ll help designers understand how to detail waterstops when they use our product, because that‘s different from conventional membrane waterproofing.
―Besides reducing permeability, the admixture acts as a mild retarder, so it helps to control the heat of hydration and consequently reduces shrinkage cracking. It doesn‘t drastically change the properties of fresh concrete, but it can improve workability somewhat. When someone considers using our product, we‘ll review the mix design and also send it to Kryton‘s lab for review, to make sure any interactions with other admixtures are taken into account. We also recommend that the contractor do a test pour, to check for air content, slump, and so on,‖ Maugeri says.
―The typical dosage rate for crystalline PRAHs is 2% by weight of total cementitious materials,‖ says John Ladas, a sales representative for Xypex Chemical Corp.‘s waterproofing admixtures, ―except in an extraordinary case, such as an exceptionally corrosive atmosphere. We can also modify the formula depending on the circumstances. We make one formulation that doesn‘t retard set at all. We might recommend that for large flatwork areas, cold weather, or a mix that contains a lot of slag.‖
Waterproofing admix was used in the renovation and expansion of the Mark Jefferson Science Complex at Eastern Michigan University in Ypsilanti, completed earlier this year. Concrete containing the Xypex crystalline PRAH was used for green roof slabs on the building addition and for an underground utility tunnel. It was the first experience with the material for Jennifer Emerick, project manager for general contractor The Christman Co. in Lansing, Mich., and she was favorably impressed. ―The tunnel consists of a 1-foot, 2-inch-thick slab, with 1-foot-thick walls and lid. It was built about 2 years ago, and there have been no leaks since the initial shrinkage cracks were sealed by the crystallization of the admix. It worked just the way the manufacturer said it would. We also got a watertight roof on the addition, without any additional roofing materials. And the placement went smoothly, just like any concrete mix,‖ Emerick says.
For projects and applications that need waterproof concrete, the use of PRAs is worth considering. Contractors need only follow sound placement and finishing practices to install it successfully, and owners may be able to cover the costs by saving the labor and materials required for other waterproofing methods.
7 ACI International Repo rt Examines Waterproofing Admixtures for Concrete: Crystalline vs. Pore Blocking and Other Admixtures
This report examines three classes of admixtures that all reduce, in some way, the permeability of concrete. The classes are hydrophobic or water-repellent chemicals, mineral fillers, and crystalline materials. In addition, the report defines two sub-categories for admixtures intended to reduce water ingress as either a PRAN – for concrete not subject to hydrostatic pressure, or as a PRAH – for concrete that is subject to hydrostatic pressure.
The water repellent or hydrophobic admixtures are based mostly on fatty acid derivatives called stearates which react with calcium hydroxide in the pore water to form an insoluble stearate that lines the pore walls. Waxes and oily emulsions can also be used as a base for hydrophobic admixtures but they are non-reactive. These types of admixtures are effective in reducing the absorption and ingress of chlorides into concrete but usually only under non-hydrostatic conditions and thus are usually classified by this document as PRANs.
The mineral fillers are inert finely ground minerals such as talcs, bentonites, clays etc but can also include chemically active materials such as lime and alkaline silicate based products. Some experts include SCMs in this category as well. While these materials will often densify the matrix and possibly shrink the pores of the concrete and restrict water passage, they typically do not fully block all pores and as such are also classified as PRANs.
Crystalline-based admixtures, on the other hand, are hydrophilic in nature and react with the constituents of the cement matrix to form CSH crystals. These crystals generate pore blocking deposits that are found to improve the concrete‘s ability to resist water penetration under pressure. These admixtures have been found to remain chemically active within the concrete and will seal additional gaps up to a certain size as they occur.
The ACI 212.3R document recommends PRAH type admixtures for applications that will experience hydrostatic head such as below grade and water retaining structures. The ACI 212.3R document further recommends that the water pressure resisting capabilities of the admixture modified concrete should be checked and confirmed through the use of permeability tests such as the US Corp of Engineers C48, DIN 1048 or BS EN 12390. The results of these tests can be used to determine a permeability coefficient K, or side by side testing against a control can be used to give an indication of permeability reduction.
Xypex Admix products would be classified as PRAH and have excellent crack healing properties. As such, Xypex admixtures are ideally suited for concrete that will need to perform in the most severe waterproofing applications. Furthermore, Xypex-treated concrete improves many of the other engineering properties of concrete such as its freeze and thaw resistance, corrosion resistance, chemical resistance and carbonation resistance.
Many of Xypex‘s competitors have for years suggested that their active or inert pore blocking technology will give performance similar to Xypex, but this recently released document from ACI suggests otherwise. The latest copy of the ACI 212-3R-10 is available on-line from ACI International and is suggested reading for those in the concrete industry.
Xypex introduced Xypex Crystalline Technology some 40 years ago and has become a primary resource to the concrete industry for information regarding crystalline waterproofing.
About Xypex Chemical Corporation
Xypex is a non-toxic, chemical treatment for the waterproofing and protection of concrete. Xypex’s primary and most distinguishing performance feature is its unique ability to generate a non-soluble crystalline formation deep within the pores and capillary tracts of the concrete – a crystalline structure that permanently seals the concrete against the penetration of water and other liquids from any direction. Xypex crystalline products are dry powder compounds composed of portland cement, silica sand and many active, proprietary chemicals.
The ABCs of Integral Crystalline Waterproofing
Although crystalline waterproofing technology has been around for more than 50 years, it is still considered ―state-of-the-art‖ and has only recently been embraced by the construction industry as a superior replacement for conventional membranes. Used in virtually every country around the world, integral crytalline waterproofing has been repeatedly and successfully tested.
Though concrete looks like a dense, rock-hard material, it‘s actually full of pores, capillaries and microcracks invisible to the naked eye. It‘s through these openings that water can enter and cause damage, making waterproofing necessary. Traditional membranes only cover the outside of concrete whereas crystalline chemicals actually work deep below the surface, within the concrete matrix itself.
The revolutionary technology of integral crystalline waterproofing is changing the way concrete structures around the world are protected from corrosion and water damage. When crystalline chemicals come into contact with water, a catalytic reaction occurs that produces crytals that plug the natural pores and microscopic voids of concrete. Crystalline technology waterproofs concrete by forming long hexagonal prisms that block concrete‘s pores and transform the concrete itself into a strong, durable waterproof barrier.
A Better Choice All Round
Unique Self-Sealing Ability
One of the unique traits of an integral crystalline waterproofing application is its ability to “self-seal”. Only a small fraction of the chemicals are used to facilitate crystal growth when they are initially mixed or applied to concrete. The unused chemicals sit dormant. When future cracks occur, water acts as a catalyst to the crystalline chemicals, triggering additional crystal growth to seal the crack.
A Permanent and Sustainable Choice
Integral crystalline waterproofing is a permanent solution – it will not crack, peel, tear or wear away, even against high hydrostatic pressure, so it never needs replacing. It’s non toxic, safe for potable water tanks and contains no volatile organic compounds. In comparison, external membranes are usually petroleum-based and can leach oil into the ground, contaminating drinking water. Membrane-coated concrete also goes straight to the landfill while crytalline waterproofed concrete can be safely recycle.
Crystalline chemicals come in powder form and can be conveniently added to new concrete at the time of batching or at the jobsite to create a powerful water barrier in slabs, walls and joints. There is no need for any type of surface application at the construction site.
Crystalline formulas can also be brushed or sprayed onto existing concrete in slurry form or broadcast onto fresh concrete flatwork by way of the “dry-shake” method. Products and application methods also exist for crack repair, construction joints, pipe penetrations and form-tie holes to protect against contamination and steel reinforcement corrosion. The best waterproofing systems can be applied to the positive or negative side of concrete, allowing the structure to be waterproofed or repaired without the costly process of digging up the perimeter landscaping.
When applied to existing concrete, crystalline chemicals are absorbed by natural capillary action and diffusion. Once inside, the chemicals begin growing crytals that fill the naturally occurring pores, capillaries and microscopic voids of concrete.
Time and Cost Savings
Using crystalline systems can actually accelerate project schedules by eliminating the need for conventional membrane application. Backfilling can begin right away and the cost of labor and surface membrane materials are reduced.
Crystalline technology is impervious to physical damage or detorioration. While membranes are the best the day they are applied, crystalline waterproofing becomes better with time.
Crytalline Copycats – What’s the Difference?
Kryton’s flagship product is Krystol Internal Membranes, better known as KIM. KIM is an environmentally friendly admixture that is mixed directly into the concrete. It can be thrown into a ready-mix truck in a convenient dissolvable bag.
KIM is also the world’s first and leading crystalline waterproofing admixture. Being ‘the original’ means there are plenty of copycats on the market. It’s easy to confuse crystalline waterproofing with products that are simply concrete densifiers or pore blockers. It’s important to stay away from stearates and sodium silicates and beware of hydrophobic products.
There are many crystalline products that claim permanent, in-depth waterproofing. However, the majority of these contain stearates and sodium silicates. Stearates and sodium silicates are often classified as dampproofers and not waterproofers since they are known to break down and leach out of concrete.
Silicate-based products react with compounds in concrete such as calcium hydroxide or free lime. The reaction binds the compounds into an insoluble solid and does not panetrate more than a few milimeters into the concrete. These products do not possess self- sealing capabilities and since they are insoluble, the presence of water in the future has no effect on them.
Stearate-based products are also hydrophobic, which means they repel water. These products have minimal penetrating ability and merely fill the initial surface pores of concrete. They are best when first applied and will not withstand hydrostatic pressure over time and cannot effectively provide long-term waterproofing.
Stick to the original: KIM
Kryton’s KIM is a cementitious chemical admixture that contains no stearates, sodiums silicates or harmful chlorides. KIM works through a proprietary blend of chemicals, promoting crystal growth that counteracts water intrusion. Moreover, KIM and other Krystol products are hydrophilic – they use water to facilitate a chemical reaction that creates an impermeable concrete mass. More water equals more crystals, until no additional water can panetrate. KIM’s self-sealing hydrophilic properties mean it’s able to grow throughout the concrete, increasing resistance to hydrostatic pressure and allowing it to become stronger with age.
In short, KIM works. It is a true crystalline waterproofing admixture that has become the industry standard for new construction. Guaranteed.
8 The Science of Krystol® Technology
Krystol® technology is based on principles that are very similar to the processes that occur during the hydration and hardening of concrete. Cement is mainly made up of several calcium silicates. When cement particles are mixed with water, a chemical reaction occurs whereby these calcium silicates combine with the water to form new compounds. The new compounds are calcium silicate hydrate (CSH) and calcium hydroxide.
The CSH forms as an amorphous microcrystalline structure, extending outward from the individual cement particles and eventually filling the space between them. The CSH crystal formation is the mechanism by which the concrete stiffens and gains strength. It is most dramatic in the first hours after the concrete is placed, but actually continues for weeks, months and even years into the life of the concrete.
The reason that hydration can continue, seemingly indefinitely, is because only a portion of the cement has reacted during the initial hydration and hardening of the concrete. A significant portion of each cement particles remains un-reacted long after the concrete has reached its design strength. It is the un-reacted particles that allow the Krystol chemicals to perform their function. Krytstol® acts as a catalyst to a larger reaction within the concrete mass.
This is significantly different from silicate-based products that react with compounds in the concrete such as calcium hydroxide or free lime. The reaction binds such a treatment into an insoluble solid and hopefully blocks the pores. These products quickly become completely bound in place and therefore do not penetrate more than a few millimeters into the concrete. For the same reason, these products will not reactivate to self-seal new cracks that may form. In fact, they are insoluble and the presence of water in the future has no effect on them.
Krystol®, on the other hand, works quite differently. The crystals that are formed are hydration crystals, but they are not amorphous like cement hydration crystals. Instead, they form into a crytalline structure of long hexagonal prisms that extend through and fill the capillary voids and micro-cracks of the concrete. The crystals themselves are not made up solely of the Krystol material, but grow from the partially reacted cement particles. This is why the crystals can travel many inches through the concrete.
Krystol® treatments that have been applied to one side of a concrete wall have been observed to cause crystal growth to occur on the other side of several inches of “solid” concrete. The Krystol® chemical is never used-up during the crystallization process. As a catalyst, only a very small amount of Krystol® is required to grow a very large quantity of crystals. Within the tight confines of the concrete, crystals can easily grow to fill and block the microscopic capillary pores and micro-cracks without using more than a small fraction of the available Krystol® chemical. The remaining chemical lies dormant within the concrete waiting for a crack to develop that will provide the necessary space and water source to allow the crystallization process to continue.
Building “green’ is increasingly becoming a necessary part of a construction firm’s best practices. Instead of just being a niche sector, green building is now at the forefront of design and construction.
The rigorous LEED (Leadership in Energy and Environmental Design) Green Building Rating System is rapidly becoming the standard for measuring a building’s environmental performance. Only introduced in the US in 2000 and in Canada in 2004, LEED standards are encouraging the construction industry to create buildings that are environmentally responsible, healthy, and profitable. Governments at all levels across the US and Canada are imposing regulatory requirements to ensure new public buildings meet a certain LEED standard.
With growing global pressure to go green, more eco-friendly products are being developed. “Green concrete” used to refer solely to concrete that had set but not hardened. Today, it also means concrete that’s made with recycled alternative materials such as reclaimed fly ash: a by-product of coal burned at power plants. Usually trucked off to landfills, the tiny glass particles of fly ash are now being used in place of traditional Portland cement to make concrete. Not only does adding fly ash increase concrete’s strength and durability, but this substitution reduces the greenhouse gas footprint of concrete.
Another green innovation is a new concrete recipe spiked with titanium dioxide: a compound often used in sunscreen products. This new cement becomes chemically active in sunlight and neutralizes air pollutants such as benzene, carbon monoxide, nitrogen oxide, and others.
Finally, there is pervious concrete. Originally used a century ago in Europe as structural insulation, pervious concrete is a permeable, porous material. This environmentally friendly material is now making a resurgence in places such as parking lots, because it allows storm and nuisance water to filtrate into the ground, recharging ground water, and resulting in zero discharge of polluted runoff into waterways. This in turn reduces urban flooding, improves the health of adjacent trees, and reduces or eliminates the need for storm drain infrastructure.
However, more often in buildings and construction, it’s waterproof concrete that’s needed. Increasingly, in the new LEED-based paradigm, the old methods of waterproofing concrete with oil-based membrane sheets are just not environmentally acceptable.
Environmentally responsible waterproof concrete
While concrete on its own has huge advantages as a green building material, making it waterproof using old-fashioned, externally applied membranes is less acceptable in today’s eco-conscious environment.
External membranes are often petroleum based and are typically applied using adhesives with highly volatile organic compounds. The high vapor pressure from these compounds can cause respiratory problems and are a contributor to “sick building syndrome.” Oil from conventional membranes can also leach out and contaminate drinking water.
One company offers products that are a significant solution to today’s “green building” pressures. Kryton’s integral crystalline technology permanently seals concrete by plugging its natural pores and capillaries and blocking the movement of water. It reacts with incoming water to self-seal the cracks that inevitably develop in concrete, protecting structures against water and contaminants that can weaken or destroy concrete and corrode steel reinforcements. Kryton’s integral crystalline technology, Krystol®, creates strong, waterproof, environmentally-safe concrete.
Although only buildings, not materials, can be certified as meeting LEED standards, Kryton products can contribute to achieving valuable LEED points in a variety of ways:
It’s predicted half of North America’s existing infrastructure will need replacing in the next 20 years. Kryton is making sure sustainability plays a big part in rebuilding North America.
Strong, waterproof concrete (waterproof from the inside out) is key to tomorrow’s environmental sustainability.
Concrete is porous and, if not waterproofed, absorbs water that can cause cracks, waterborne contaminants and chemicals that can cause deterioration. If you want to protect your concrete and ensure it has a long, serviceable life, waterproofing is essential.
But how? What‘s the best method and the best material?
To make concrete really waterproof—which means both preventing water passage and resisting hydrostatic pressure—you can waterproof from the positive (exterior) side, negative (interior) side or from within the concrete itself (integral systems). Al-though the oldest and most widely used positive-side technology is sheet membrane waterproofing, its failures and limitations are also common and costly. Since the 1980s, many construction projects around the globe have used integral crystalline admixtures to waterproof concrete. Integral systems block water pas-sage from any direction by working from the inside out, making the concrete itself the water barrier.
It can be difficult to keep up with advancements in both membranes and crystalline admixtures—and there have been substantial advancements in both technologies. Here‘s a summary that can help make the choice more clear.
Sheet membrane systems
Historically, hot-applied sheet systems—known as built-up bituminous membranes—were used for below-grade concrete waterproofing. These sheets were made from alternating layers of bitumen and felt. When heated, traditional bitumen—both coal tar pitch and asphalt—releases volatile organic compounds (VOCs) and potentially carcinogenic fumes.
Since the early 1990s, the bitumen system‘s popularity has fallen due to an increasing number of bans on its use by governmental and regulatory agencies. Substantial steps have been taken by product manufacturers to replace these membranes.
Polymer-modified bitumens have evolved from the original bituminous sheet systems, offering a safer, cold-applied alter-native. Cold-applied polymer-modified bitumen is a sheet membrane composed of polymer materials compounded with asphalt and attached to a polyethylene sheet. The polymer is integrated with the asphalt to create a more viscous and less temperature-sensitive elastic material compared to asphalt on its own. These sheets are self-adhering and eliminate the harmful toxins typically associated with asphalt adhesion. They also increase tensile strength, resistance to acidic soils, resilience, self-healing and bondability.
Despite such advancements, disadvantages persist. Their field fabrication requires intensive labour and carefully supervised installation.
Installation can be challenging as membranes require sealing, lap-ping, and finishing of seams at the corners, edges and between sheets. Additionally, sheet membranes must be applied to a smooth finish without voids, honeycombs or protrusions. Because the membrane can puncture and tear during backfilling, protection boards also need to be installed.
Sheet membranes also pose other limitations. They are challenging to use in vertical applications and difficult, if not impossible, for blind wall applications. They are often inaccessible for repairs after installation.
Performance and durability can also be issues. Performance depends on surface adhesion and proper seam lapping. Materials are strong-est on the first day following installation, after which they gradually deteriorate.
Although polymer-modified bitumens are an improvement over their hot-applied predecessors, they still present challenges, including poor resistance to ultraviolet radiation, the need for solvent-based primer and adhesives and an air temperature warmer than –4° C (25° F) during installation.
Careful installation practices must also be followed. Sheets can debond if they are not promptly covered after installation, the top edges are not sealed, the primer is incorrectly applied or if tie-holes are not flush with the concrete surface.
In spite of all these drawbacks, sheet membranes have been the industry norm in waterproofing for many years—they still hold the majority of the market share. Their continued use is due to impact resistance, toughness and overall durability compared to other membrane options.
Thermoplastic polymers have led to the creation of thermoplastic membranes. These membranes are composed of polyvinyl chloride (PVC), chlorinated polyurethane or chlorosulfonated polyethylene, with glass fibre-reinforced PVC being the most popular membrane type.
Thermoplastic materials soften when heated and harden when cooled, so sheets can be attached with solvent-based adhesives or by heat-welding at the seams—a significant advantage over field-fabricated seams. Thermoplastic membranes also effectively resist chemicals and hydrostatic pressure.
Despite these advantages, there are drawbacks. Thermoplastic membrane properties change depending on the temperature. The PVC deteriorates if it is in contact with hydrocarbons. Installation still demands the use of solvent-based primer and adhesives and any asphalt-based protection boards cannot be placed directly on the PVC membranes. In addition, the concrete must have a ―floor quality‖ steel trowel finish to ensure good adhesion.
Thermosetting membranes (i.e. vulcanized rubber) are more resistant to heat, solvents, general chemical attack and creep than thermoplastic membranes are, due to the vulcanization of butyl, ethylene propylene diene monomer or neoprene rubber.
However, as thermosetting materials harden permanently when heated, these sheets can only be attached using solvent-based adhesives on the seams, and movement after application is very restricted. Also, because the seams between sheets are field-fabricated, they never attain the base material‘s tensile strength. Thermosetting membrane sheets tend to stretch and are difficult to install on vertical surfaces. They can disband or blister if a negative vapor drive is present because they do not breathe. And they require the use of solvent-based primers and adhesives—another drawback.
Clay systems (bentonite)
This waterproofing method has been employed for more than 75 years, but its popularity has recently increased. Its effectiveness is based on the properties of impure clay, which swells to block water. Bentonite is versatile and comes in various forms, from prefabricated panels to trowelable mixtures.
Clay systems are excellent for waterproofing, but need sufficient hydration for success—and in some applications this can be difficult and unreliable. First, high hydrostatic pressure is required for complete hydration of the clay molecules. Hydration must occur immediately after installation and backfilling. It must also take place in an adequately confined area to avoid lifting or cracking the concrete slab.
Bentonite can self-heal, is non-toxic and is relatively easy to install, but it is rarely used in places where the risk of leaks must be minimal and humidity control is necessary. Bentonite materials are weather-sensitive and not resistant to soil chemicals (e.g., brines, acids or alkalines), which ultimately decreases their ability to thoroughly waterproof structures.
Bentonite systems cannot be installed during rainfall while groundwater level is fluctuating, or in areas with constant wetting and drying cycles because the clay will deteriorate. Installation is also not advised in places with free flowing water that would wash away clay. Once installed, bentonite is difficult to remove, so options for future repair or replacement are limited.
Bentonite sheets are most beneficial for blindside wall applications as they can be nailed directly to the foundation walls.
Liquid-applied membranes can be applied with a brush, spray, roller, trowel or squeegee, and usually contain urethane or polymeric asphalt (hot- or cold-applied) in a solvent base. These membranes are usually applied on the positive side of set concrete and have high elastomeric properties. More recent technologies have also made negative-side applications possible.
Successful waterproofing with liquid-applied membranes depends on proper thickness and uniform application. They call for skilled, experienced labour to apply them, a clean and dry substrate—which can often be a construction environment challenge—a protection layer before backfilling, properly cured concrete to avoid problems with adhesion and blistering and, on horizontal applications, a sub-slab. Liquid-applied membranes deteriorate when exposed to UV radiation and cannot withstand foot traffic. The liquids them-selves also contain toxic and hazardous VOCs.
Although liquid-applied membranes work well on projects with multiple plane transitions, intricate geometric shapes and protrusions, they are typically only used when prefabricated sheets do not work.
For the last three decades, a new type of waterproofing has been used around the globe. These integral admixture systems are added at the batching plant or onsite, and react chemically within the concrete. Instead of forming a barrier on the positive or negative side of concrete, they turn the concrete itself into a water barrier. Integral concrete waterproofing systems can be densifiers, water repellents or crystalline admixtures.
Densifiers react with the calcium hydroxide formed in hydration, creating another by-product that increases concrete density and slows water migration. They are typically not characterized as waterproofing materials or repellents because they have no ability to seal cracks and joints. Concrete under hydrostatic pressure requires additional waterproofing methods to protect it from damage and deterioration.
Water repellents are also known as ―hydrophobic‖. These products typically come in liquid form, and include oils, hydrocarbons, stearates or other long-chain fatty acid derivatives. Although hydrophobic systems may perform satisfactorily for dampproofing, they are less successful at resisting liquid under hydrostatic pressure. Pre-curing and post-curing stresses cause cracking in any concrete, which creates pathways for water passage. So the effectiveness of water repellents is highly dependent on the concrete itself.
Crystalline-based systems typically come in a dry, powdered form and are hydrophilic in nature. Unlike their hydrophobic counter-parts, crystalline systems actually use available water to grow crystals inside concrete, effectively closing off pathways for moisture that can damage concrete. They block water from any direction because the concrete itself becomes the water barrier.
In contrast to water repellents, crystalline technologies enable self-sealing. The admixture is a blend of cementitious and proprietary chemicals that actually work with the available water in concrete to form insoluble crystals. These needle-like crystals grow until all pores are blocked and no water can penetrate the concrete. The crystalline formula can allow concrete to self-seal hairline cracks up to 0.5 mm (0.02 in.), even years after the original construction.
Concrete treated with these admixtures contains chemicals that lie dormant within. If a crack forms, any water influx causes more crystals to grow, re-blocking and sealing the passage against water and waterborne contaminants. Whenever new water enters the concrete through changing water levels or new cracks, crystals continue to grow and seal the concrete. The crystals within the concrete are impervious to physical damage and deterioration; there is no danger of punctures, tears or seam leaks. As a result, a building‘s durability increases when crystalline admixtures are used.
In addition to promoting and enhancing the natural hydration process of cement, these systems are highly versatile, useful and reliable for a wide range of applications. For example, concrete treated with crystalline admixtures is suitable for complex architectural designs. As architectural protrusions do not pose any waterproofing challenge, any type of concrete structure—vertical, horizontal or shaped—can be securely waterproofed.
Concrete waterproofed with crystalline admixtures affords other benefits, too. It contains no VOCs and can be completely recycled when demolition occurs. Membranes do not have to be separated from the concrete, waterborne contaminants are not present in the concrete, and petroleum-based materials are not left behind to leach into soil.
Additionally, crystalline admixtures offer installation advantages. Unlike traditional membrane waterproofing, which tends to be labour-intensive and expensive, crystalline technology decreases installation and maintenance costs and is easy to handle—admixtures can be shipped in dissolvable, pulpable bags that are thrown into the concrete batch during mixing. This speeds up the construction schedule and decreases labour costs by combining steps with concrete placing.
Integral crystalline waterproofing systems should not be used in applications under constant movement. During the crystallization process, crystals align in a three-dimensional array that breaks when subjected to excessive movement. Areas that require flexibility and face recurring movement—such as plaza decks or rooftops—would be better waterproofed another way.
Integral waterproofing admixtures tend to be less expensive for materials, and additional labour costs are almost non-existent. They also allow for a larger building footprint and reduce maintenance and repairs over the long term.
9 Basement Waterproofing Products
Basement Waterproofing Site’s specialists are involved every day with all of the different types of materials, products and systems for successful basement waterproofing. These include:
10 1) Waterproofing Type A Barrier Protection Products (Externally or Internally Applied)
i. Bonded Sheet Waterproofing Membranes (for new construction waterproofing works)
Bonded sheet membranes may be pre – or post-applied to the structure.
Pre-applied: Pre-applied membranes are usually attached to the concrete blinding for slabs and to the formwork for the walls and vertical surfaces. With fleece fabric layers they subsequently become bonded to the concrete walls and slabs as they are poured. Typical examples of these products are the Grace Preprufe range. These sheet waterproofing membranes are produced using HDPE bases self-adhesive membranes fully bonded through the laminated fleece on the concreting side, other systems are also available based on the even more durable FPO sheet membranes are also available.
Post-applied: Alternatively sheet membrane waterproofing systems are post-applied to the structure and jointed by welding (hot air) to the integral joint waterstops in a combined waterproofing system.
Internal (i.e. for water retaining structures to keep water in) and external (i.e. for basements to keep water out) bonded sheet membrane syatems need to be supported and protected by the load-bearing structure itself and / or additional protection boards, so that external ground or water pressures can be adequately resisted.
It is very important with all post-applied sheet membrane systems that the substructure has a suitable substrate surface finish to apply the sheet membranes onto. The concrete slabs are again poured over this type of sheet membranes that are loose-laid on the blinding and welded at the joints. Where required they are also pre-welded to the joint waterstops, such as external waterstops or when they are being used to create a compartment waterproofing system. On the blinding and for post-application on concrete walls and other surfaces, they must be free from raised ridges and sharp corners, plus any indents or voids should be pre-filled and tie-wires etc. removed, so that overall it is finished to a smooth, uniform level surface. Brick and blockwork walls must have flush joints, or these must also be pre-filled by pointing.
ii. Liquid Applied Waterproofing Membranes
There are many different types of Liquid Applied Membrane (LAM) Waterproofing materials and they all have different application and performance advantages and limitations. these materials range from polymer modified bitumen‘s (such as Remmers Profi-tight), through single pack polyurethanes, to very high performance 2 component polyurethane (such as Liquid Plastics Decothane range) and other resin based materials (designed for both New and Refurbishment waterproofing works). Details on the preparation of substrates, application rates, method statements and curing requirements are detailed on the individual Product Data Sheets.
In principle many difficult waterproofing problems ‘from the basement to the roof’ of buildings and many other structures can be solved with liquid applied waterproofing membranes.
Suitable protection to liquid applied waterproofing membrane systems should also be provided once it has completely cured and hardened, if it is to be exposed or back-filled, such as protective boards purpose designed for this purpose and cut to fit the external profile.
For additional advice on the suitability of liquid applied membranes for waterproofing on your project, please call any NCC Basement Waterproofing Site office and one of our waterproofing specialists will be pleased to assist you.
iii. Geosynthetic & Clay Waterproof Liners (using bentonite clay for New Construction Waterproofing Works)
Traditionally bentonite is a natural clay mineral, following similar principles to the use of clay for waterproofing as it is has been for thousands of years. The bentonite clay absorbs water and expands when in contact with water, also forming a barrier to the transmission of further water or other liquids. The bentonite is held between two geosynthetic layers and forms an impervious seal bonded to the concrete surface. They are available in two types:
– Dry bentonite liners which rely on activation taking place on site from the absorption of the groundwater once installed.
– Pre-hydrated bentonite liners, which are manufactured by vacuum extrusion and therefore they do not need to be additionally hydrated on site. Bentonite based waterproofing materials have largely been replaced with newer and more efficient technologies for basement waterproofing projects in the UK, but they are still widely used around the world for new-build basement waterproofing due to their relatively simple installation and low cost, but NCC find that today there are normally much more effective and efficient waterproofing solutions available.
Important Notes: Bentonite-based waterproofing solutions can only be used on new construction projects and where it is certain that they will always remain confined between two surfaces and they cannot ever be left exposed. The main problem with these older technology waterproofing products is that in variable water table conditions, all bentonite systems are not effective and can be washed out through cyclic wetting and drying.
iv. Mastic Asphalt Waterproofing (for new construction basement waterproofing only)
Important Note: Mastic asphalt standards dictate that it should always be applied in a minimum of three coats and that concrete surfaces must be prepared. Smooth concrete surfaces will not provide an adequate key, so mechanical surface preparation is always required.
In common with many UK building owners and architects, NCC no longer recommend Mastic Asphalt, nor any other hot or flame applied materials for waterproofing works due the difficulties of application on site, due to the risk of fire and the corresponding and increasingly prohibitively high insurance costs and the onerous contractor / specifier / owner risk liability and implications.
v. Crystalline Slurries and Powders (New and Refurbishment Waterproofing Works)
Cement based crystalline slurry barrier coatings are blends of cement, sand, additives and so-called ‘active’ chemicals. They are supplied in pre-batched units of slurry product, or in powder form to be mixed with water and cement and also applied as slurry coating, directly onto prepared concrete surface. The ‘active’ chemicals combine with free lime and moisture present in the concrete capillaries to form insoluble crystalline calcium silicate hydrate complexes, which block the pores and also prevent water ingress. Crystalline waterproofing product of this type include materials from Remmers, Xypex and Sika.
The cement based crystallization waterproofing barrier coatings can be applied to the internal or external surfaces of a concrete structure by brush or spray. They are suitable for use on both new and existing structures, and some claim that they do not require an additional protective layer such as the modified render coats normally employed for this. However NCC’s Basement Waterproofing Site specialists believe this to be a false economy and that any surface waterproofing solution must incorporate a physical layer rather than just surface treatment by the coating alone. This is due to the variable consistence and porosity of the substrate as this can lead to wide variations in effectiveness for the waterproofing treatment, if this is not completed with the additional ‗protective‘ layer.
The concrete surfaces should always be mechanically prepared to have an open textured surface and capillary pore structure, prior to application of this type of crystalline waterproofing barrier.
vi. Cement Based, Multi-coat Waterproofing Renders, Mortars and Slurry Coatings (for New and Refurbishment Waterproofing Works)
This is one of the most widely used and well proven basement waterproofing solutions for refurbishment waterproofing projects throughout the UK, Europe and the rest of the world. They are also preferred in some situations for new construction due to their ease of application and cost effectiveness.
The installation of cement based multi-coat renders, mortars and coatings should, be left until as much as practicable of the structure is built and therefore its dead load has been created. The substrate should be prepared to an open textured surface and capillary pore structure in accordance with the relevant product PDS prior to application of the system which can be by trowel, brush or spray according to the specific products nature. These products are also known as ‗cellar tanking products‘ or ‘basement tanking products’ and the best known and most widely used in the UK is the BBA Aproved, Sika-1 prebagged waterproof tanking system. The Sika 1 Tanking system is applied as a combination of a tanking slurry and then built up with tanking renders in a multi-coat waterproof tanking system.
The slurry applied systems are also known as ‗tanking slurries‘ and include the well-known and also BBA Approved, SikaTop Seal 107 tanking slurry and Remmers Profi-Tight tanking slurry. These are both applied by ‗slurry brush’ in 1 – 3 coats according to the waterproofing system‘s performance requirements.
Details on the cement based multi-coat waterproofing products application methods and thicknesses, consumption rates, mixing ratio and requirements, the number of layers/coats and curing required can vary quite considerably between the different products and systems. Therefore we recommend that you read the relevant Product Data Sheet (PDS) and Materials Safety Data Sheet (MSDS) and if you have any concerns, and then please contact any NCC office for detailed information and advice for your specific waterproofing project. The substrate and structural elements should also be assessed for their suitability to withstand any increase in applied loads from future water pressure after the waterproofing is complete.
11 2) Waterproofing Type B Structurally Integral Waterproofing Protection Products
Obviously integral waterproofing product, systems can only be used as the waterproofing system, or as a component of the waterproofing system for new reinforced concrete structures. They can also be designed to achieve or assist in preventing water vapour ingress.
This approach cannot normally be used for refurbishment works, as Type B integral waterproofing protection relies upon the waterproofing materials being incorporated into the structure. However they are very often ideal for use in extension situations for the potentially complex connections and providing watertight joints between new construction and existing structures.
Pipework and other service entries are particularly vulnerable to water penetration, so where these cannot be avoided, they should be carefully detailed, for example by incorporating preformed hydrophilic gaskets and swellable hydrophilic joint sealants (such as Sikaswell P profiles and SikaSwell S sealants) to minimize the risk of any future water ingress.
NCC Basement Waterproofing Site specialists can assist you to determine most appropriate integral waterproofing solutions for your project including the complete specifications, detailing solutions and method statements.
A summary of the key component products includes:
i. Watertight Concrete Using Waterproofing Admixtures:
These are the waterproofing admixtures which increase the inherent resistance and therefore reduce the permeability of concrete to water and water vapour. Waterproofing (water-resisting) admixtures such as the BBA Approved Sika-1+ system that is used in conjunction with Sika Viscocrete high range water-reducing admixtures to achieve the necessary reduction in water permeability of the concrete..
Concrete containing a proven waterproof admixture (i.e. the BBA Approved Sika-1+ system), will have a considerably lower degree of water permeability and water vapour transmission. The concrete mix design and placing must always be adequately supervised at the ready-mix plant and on-site. NCC basement waterproofing specialists can assist with this supervision on your site.
These waterproofing admixtures are generally to be used in conjunction with the integral jointing systems below and these are normally approved and supplied by the waterproof concrete admixture producer to ensure compatability and waterproofing system responsibilities.
Waterstops are established solutions for integral joint sealing and NCC can provide detailed advice and support to select, specific and install the right system on your project. The principal types of waterstops for construction and movement (expansion) joints can be classified as follows:
ii. a) Passive waterstop sections:
Today these are usually flexible polyvinyl chloride (PVC) or other synthetic elastomer based profiles cast into the concrete and therefore fixed into the structure on both sides of the joint, either at the concrete surface or mid-depth of the concrete section, to form a physical obstruction to water transmission; i.e. these systems basically function by greatly extending the length water has to trowel and therefore reducing the possibility of any leak occurring.
ii. b) Active ( hydrophilic) profiles:
Preformed hydrophilic profiles or sealants (such as SikaSwell P or S) applied in or concrete joint at depth in the section. The materials swell or give rise to crystal growth on contact with water providing an enhanced obstruction to its path. They can be used on their own as the joint sealing system with limited exposure to water pressure, or in a combined system with passive waterstop sections for example.
ii. c) Permeable hoses (i.e. Sika Fuko) or special sections (i.e. sika Injectoflex):
These are fixed to the construction joint surface before casting the second pour and they are specially designed to facilitate the injection of a specialist sealing resin into the joint, if and when required in the future.
All of these waterstops can be used to provide enhanced resistance to water transmission in all of the joints in the concrete structure, e.g., including movement / expansion joints; at construction, isolation or day-work joints, service entry pipe or other penetrations. The positioning of the waterstop(s) (external and/or internal) should be appropriate for the method of construction and the level of risk. Particular attention should be given to the use of waterstops in the movement / expansion joints in the concrete structure (although the requirement for these should always be avoided by design wherever possible).
Where centre-bulb waterstops are used, the methods of fixing should also be sufficient to keep the components in the correct position during the concreting operations. These must always be adequate compaction of the concrete around these internal waterproofing components to avoid actually creating paths for subsequent water ingress. NCC can support you throughout the design and installation phases of your waterproofing projects.
12 3) Waterproofing Type C: Cavity Drain Waterproofing Protection Products
Type C Cavity Drain Waterproofing Protection manages water that penetrates the external shell of a structure, by collecting it in a cavity formed between the external wall or floor and an internal lining/wall/floor surface. There is permanent reliance on this cavity to collect any groundwater seepage and condensation internally, then direct it to a suitable discharge point e.g. drains or a sump for removal by gravity drainage or mechanical pumping.
Traditionally, the drainage cavity in floor construction was formed by the use of a no-fines concrete base or ceramic drainage units / channels embedded in the concrete. These are rarely used today due to cost and their dimensions in new construction, but this design might well be encountered and have to be accommodated when refurbishing existing structures.
Structural aspects of cavity drainage:
The exterior walls of the structure should be capable of controlling the quantity of water that can pass through it, in order not to exceed the drainage capacity of the system. Water entering a drainage cavity system is regulated by the structure, so any defects that might result in unacceptable leaks should be remedied before the new drainage cavity membrane is installed.
Cavity drain systems do not change the loadings on an existing structure due to water, other than where remedial measures are taken to control the level of water ingress.
Cavity drain membranes:
Cavity drainage membranes form a permanent void or ‗cavity‘ between the external elements of the structure and the internal wall/floor finishes. Such cavities vary in width, depending on the design of the stud height or profile of the membrane; They are usually ≤ 20 mm according to the anticipated volume of water that they are to channel to where it is drained or pumped out of the structure.
Cavity drain membranes should be used in accordance with appropriate stud height or profile after considering the external hydrostatic pressure, the porosity of the structure and the predicted rates of water ingress though the structure’s external fabric.
Cavity drain membranes have a particular advantage in that they can be used on surfaces that have been contaminated with impurities. However, in these situations, consultation should first be undertaken with the local Environmental Agency regarding any potential discharge from the system.
Before a cavity drain membrane is laid or fitted on walls and floors constructed of new concrete, the concrete surface should be treated to reduce the risk of leaching of free lime or mineral salts, which could otherwise build up over time and eventually create an obstruction of the drainage system.
Where the floor cavity incorporates perimeter channels that discharge into a sump(s), both the channels and the sump(s) should be cleaned before, during and after installation of the membrane to allow uninterrupted drainage
The regular servicing requirements for this type of waterproofing system should be clearly set out in the documentation supplied to the client, including the need for regular planned maintenance of the drainage and/or pumping systems which must never be done less than once a year.
With cavity drain systems the client and their designers should always be informed that any failure to adhere to the defined maintenance schedules could result in a premature failure of the waterproofing system.
Advice on Basement Waterproofing System – All Types
Understanding Crystalline Concrete Technology
CONCRETE IS POROUS. WITHOUT WATERPROOFING, IT ABSORBS MOISTURE THAT CAN CAUSE CRACKS, AS WELL AS CONTAMINANTS AND CHEMICALS THAT LEAD TO DETERIORATION. TO PROTECT CONCRETE AND ENSURE IT HAS A LONG, SERVICEABLE LIFE, WATERPROOFING IS ESSENTIAL.
According to ASTM International, concrete waterproofing involves using a material that prevents water passage and resists hydrostatic pressure. The capacity to resist this pressure differentiates ‗waterproof‘ from ‗dampproof‘, as the latter offers no hydrostatic resistance.
There are many choices and approaches to make concrete truly waterproof. It call be achieved from:
The most widely used positive-side waterproofing type is sheet membrane technology. Membranes have been used for decades but, despite advancenlents, their failures and limitations can be costly.
Since the 1980s, many construction projects have employed crystalline admixtures, which are integral waterproofing systems. These integral systems block water passage from any direction by working from the inside out; this makes the concrete itself the water barrier.
It can be difficult to keep up with advancements in both membrane and integral waterproofing as the admixture technologies. However, improvements in integral waterproofing make it a highly effective and valuable system for use in place of the more common membranes.
Sheet membrane systems
Positive-side waterproofing can be achieved using various membrane technologies.
Historically, hot-applied sheet systems—known as built-up bituminous membranes—were used for below-grade concrete waterproofing. These sheets were made from alternating layers of bitumen and felt. When heated, traditional bitumen—both coal tar pitch and asphalt—releases volatile organic compounds (VOCs) and potentially carcinogenic fumes.
Since the early 1990s, the bitumen system‘s popularity has fallen due to an increasing number of bans on its use by governmental and regulatory agencies. Another drawback of sheet membranes is their field fabrication requires intensive labor and carefully supervised installation.
Substantial steps have been taken by product manufacturers to replace these membranes. Polymer-modified bitumens have evolved from the original bituminous sheet systems, offering a safer, cold-applied alternative. Material developments, such as thermoplastic and thermosetting polymers, have opened the door for a new series of radically different sheet membranes. Despite such progress, disadvantages persist.
Installation can be challenging as membranes require sealing, lapping, and finishing of seams at the corners, edges, and between sheets.
Additionally, sheet membranes must be applied to a smooth finish without voids, honeycombs, or protrusions. Protection board installation is also required as the membrane can puncture and tear during backfilling.
Sheet membranes pose various other limitations. They are challenging to use in vertical applications and difficult, if not impossible, for blind wall applications. In cases where they can be employed, they may be inaccessible for repairs after installation.
Performance and durability can also be issues. Performance depends on surface adhesion and proper seam lapping. Materials are strongest on the first day after the installation; at that point, they deteriorate over time.
However, hot-applied sheet membranes have been the industry norm for many years—they still hold the majority of the market share and remain popular for waterproof roofing systems. Their continued use is due to impact resistance, toughness, and overall durability compared to other membrane options.
The newest phase in bituminous sheet waterproofing is polymer-modified bitumen (i.e. rubberized asphalt). This cold-applied sheet membrane is composed of polymer materials compounded with asphalt and attached to a polyethylene sheet. The polymer is integrated with the asphalt to create a more viscous and less temperature-sensitive elastic material compared to asphalt on its own. These sheets are self-adhering and eliminate harmful toxins typically associated with asphalt adhesion. They also increase tensile strength, resistance to acidic soils, resilience, self-healing, and bondability.
Although polymer-modified bitumens are an improvement over their hot-applied predecessors, they still present some challenges, including:
Careful installation practices must also be followed. Sheets can debond if:
These waterproofing membranes are currently employed in all applications where hot-applied sheet systems were previously used; they can be utilized to waterproof all three areas of concrete construction, including structural slabs, slabs-on-ground, and foundation walls.
Thermoplastic polymers have led to the manufacturing of thermoplastic membranes. These membranes are composed of polyvinyl chloride (PVC), chlorinated polyurethane, or chlorosulfonated polyethylene, with glass fiber-reinforced PVC being the most popular membrane type.
Improvements in integral admixture waterproofing technologies make it a highly effective and valuable system for use in place of the more common membranes.
Thermoplastic materials soften when heated and harden when cooled, so sheets can be attached with solvent-based adhesives or by heat-welding at the seams—a significant advantage over field-fabricated seams. Thermoplastic membranes also effectively resist chemicals and hydrostatic pressure.
Despite these various advantages, drawbacks include:
These waterproofing membranes are commonly used as liners in water and sewerage containment applications. They are fully adhered to the substrate in horizontal and vertical applications, but can also be loosely laid over a framed slab.
Thermoplastic membranes can be employed to waterproof all components, including structural slabs, slabs-onground, and foundation walls. The concrete must be a ‗floor quality‘ steel trowel finish, however, in order to ensure good adhesion.
Thermosetting membranes technology (i.e. vulcanized rubber) is more resistant to heat, solvents, general chemical attack, and creep than thermoplastic membranes are, due to the vulcanization of butyl, ethylene propylene diene monomer (EPDM), or neoprene rubber.
However, as thermosetting materials harden permanently when heated, these sheets can only be attached using solvent-based adhesives on the seams.
Further, as seams between sheets are field-fabricated, they never attain the base material‘s tensile strength.
Sheets are also difficult to install on vertical surfaces, as they tend to stretch due to a low elastic modulus and lack of reinforcement. Additionally, their non-breathability may cause disbonding or blistering if negative vapor drive is present. Other disadvantages include:
These waterproofing membranes are used in similar applications as thermosetting membranes, but only require a ‗smooth‘ concrete finish.
Clay systems (bentonite)
This positive-side waterproofing method has been employed for more than 75 years, but its popularity has recently increased. As impure clay swells to block water, bentonite is versatile and comes in various forms, from prefabricated panels to trowelable mixtures.
Clay systems are excellent for waterproofing, but need sufficient hydration for success—in some applications, this can be difficult and unreliable. First, high hydrostatic pressure is required for complete hydration of the clay Molecules. Hydration must occur immediately after installation and backfilling; it must also take place in an adequately confined area to avoid lifting or cracking the concrete slab.
Bentonite can self-heal, is non-toxic, and is relatively easy to install, but is rarely minimal in places where leaking risk must be minimal and humidity control is necessary. These conditions are essential because bentonite materials are weather-sensitive and not resistant to soil chemicals (e.g. brines, acids, or alkalines), which ultimately decreases their ability to thoroughly waterproof structures.
Bentonite systems cannot be installed during rainfall, while groundwater level is fluctuating, or in areas with constant wetting and drying cycles because the clay will deteriorate. Installation is also not advised in places with free flowing water that would wash away clay. Once installed, bentonite is difficult to remove. This attribute limits options for future repair or replacement.
Bentonite sheets are most beneficial for blindside wall applications as they can be nailed directly to the foundation walls. Bentonite can also be used in other applications, especially now with the variety of forms in which it is supplied.
Liquid-applied membranes (LAMs) can be applied with a brush, spray, roller, trowel, or squeegee, and usually contain urethane or polymeric asphalt (hot- or cold-applied) in a solvent base. These membranes are usually applied on the positive side of set concrete and have high elastomeric properties. More recent technologies have also made negative-side applications possible.
Successful waterproofing with liquid-applied membranes is contingent on proper thickness and uniform application.
Additionally, LAMs require:
Liquid-applied membranes can be problematic due to their lack of resistance to UV radiation and inability to withstand foot traffic. The liquids themselves also contain toxic and hazardous VOCs.
Although LAMs work well on projects with multiple plane transitions, intricate geometric shapes, and protrusions, they are typically only used in cases where prefabricated sheets do not work.
Negative-side waterproofing systems are applied to the concrete structure‘s dry side, opposite the water pressure. Typically (but not always), negative-side waterproofing systems come in the form of cementitious coatings rather than membranes technologies, because the latter would be at risk of debonding from the external water pressure. Waterproofing coatings are often trowelled onto the concrete, brushed, or sprayed as slurry.
The placement of negative-side waterproofing on the dry, inside surface of a structure is its main advantage. This application offers easier application, leak detection, and maintenance over positive-side waterproofing. It is often used where positive-side waterproofing is not an option, such as inaccessible areas like pits or shafts.
Although cementitious waterproofing offers limited flexibility and no self-sealing ability, it is very durable and typically costs less than alternatives. However, negative-side cementitious waterproofing is rarely used for new construction because it leaves concrete exposed to any corrosive soil chemicals and freeze-thaw cycles.
Positive-side systems act as a physical barrier between the concrete and dirt/ground water. In contrast, negative-side waterproofing takes place on the opposite side of the concrete wall, stopping water from entering the structure without protecting the concrete itself. Concrete can still be penetrated by water and waterborne contaminants, leading to deterioration. Consequently, the use of negative-side waterproofing is predominantly limited to remedial work.
Integral admixture systems are added at the batching plant or onsite, and react chemically within the concrete. Instead of forming a barrier on the positive or negative side of concrete, they turn the concrete itself into a water barrier.
Integral concrete waterproofing systems are categorized in three main ways—as densifiers, water repellents, or crystalline/pore blockers.
Densifiers include pozzolans and supplementary cementing materials (SCMs) such as fly ash, silica fume, metakaolin, and slag. Densifiers react with the calcium hydroxide formed in hydration, creating another by-product that increases concrete density and slows water migration.
Densifiers are typically not characterized as waterproofing materials or repellents. They have no ability to seal cracks and joints. Concrete under hydrostatic pressure requires additional waterproofing methods to protect from damage and deterioration.
SCMs can be used to modify concrete‘s properties. They are typically employed as a replacement for a portion of the portland cement and to increase the strength and durability of a concrete structure. When added in the right proportion, they can also reduce the concrete‘s overall cost.
Systems that work to repel water are known as ‗hydrophobic.‘ These products typically come in liquid form, and include oils, hydrocarbons, stearates, or other long-chain fatty acid derivatives.
Although hydrophobic systems may perform satisfactorily for dampproofing, they are less successful at resisting liquid under hydrostatic pressure. Additionally, these compounds‘ performance is highly dependent on the concrete itself. Pre-curing and post-curing stresses cause cracking in any concrete, creating pathways for water passage.
Hydrophobic systems are ineffective at waterproofing such cracks under hydrostatic pressure. These systems are best suited for above-grade applications or non-critical areas with low water tables.
Crystalline-based systems typically come in a dry, powdered form and are hydrophilic in nature. Unlike their hydrophobic counterparts, crystalline systems actually use available water to grow crystals inside concrete, effectively closing off pathways for moisture that can damage concrete. They block water from any direction because the concrete itself becomes the water barrier.
In contrast to water repellents, crystalline technologies enable self-sealing. They involve admixtures made up of a blend of cementitious and proprietary chemicals that actually work with the available water in concrete to form insoluble crystals; the needle-like crystals grow until all pores are blocked and no water can penetrate the concrete. These crystalline formulas can allow concrete to self-seal hairline cracks up to 0.5 min (0.02 in.).
Concrete treated with these admixtures contains chemicals that lie dormant within. If a crack forms, any water influx causes more crystals to grow, re-blocking and sealing the passage against water and waterborne contaminants. Whenever new water enters the concrete through changing water levels or new cracks, crystals continue to grow and seal the concrete. The crystals within the concrete are impervious to physical damage and deterioration; there is no danger of punctures, tears, or seam leaks. Consequently, a building‘s durability increases when crystalline admixtures are used.
In addition to promoting and enhancing the natural hydration process of cement, these systems are highly versatile, useful, and reliable for a wide range of applications. For example, concrete treated with crystalline admixtures is suitable for complex architectural designs. As architectural protrusions are not waterproofing challenges, any type of concrete structure—vertical, horizontal, or shaped—can be securely waterproofed.
Concrete waterproofed with crystalline admixtures affords other benefits. It contains no VOCs and can be completely recycled when demolition takes place. Membranes do not have to be separated from the concrete, waterborne contaminants are not present in the concrete, and petroleum-based materials are not left behind to leach into soil.
Additionally, crystalline admixtures present a number of installation advantages. Unlike traditional membrane waterproofing, which tends to be labor- intensive and expensive, crystalline technology decreases maintenance costs and is easy to handle—admixtures can be shipped in dissolvable, palpable bags that are thrown into the concrete batch during mixing.
As admixtures are added, they speed up the construction schedule and decrease labor costs by combining steps with concrete placing.
Limitations and considerations
Despite their benefits, design /construction professionals should keep in mind integral waterproofing systems are no substitute for sound construction practices. These systems must be used in conjunction with industry standards and best practices for concrete construction.
As the concrete itself makes up the barrier to water penetration, crystalline waterproofing requires above-average concrete. Substandard construction practices and products that lead to poor consolidation, unplanned cold joints, and improperly cured concrete cannot be tolerated.
Additionally, integral crystalline waterproofing systems should not be employed in applications under constant movement. During the crystallization process, crystals align in a three-dimensional array that breaks when subjected to excessive movement. Areas that require flexibility and face recurring movement—such as plaza decks or rooftops—would be better serviced with another system. Expansion joints and some suspended slabs and roof decks with excessive cracking may not self-seal at an acceptable rate.
Built-up options are generally the most costly due to the materials involved and the need for highly trained, experienced applicators. The time and space to apply sheet membranes is an indirect cost to this application method.
Integral waterproofing admixtures tend to be less expensive for materials, and labor costs are almost non-existent given the application method. They also allow for a larger building footprint and reduce maintenance and repairs over the long term.
Although sheet membranes have been—and continue to be—the industry norm, integral hydrophilic systems should receive their due. Advancements in this technology make it a highly versatile and sophisticated method for waterproofing. It provides an inexpensive way to seamlessly waterproof concrete, creating permanent and durable structures.
Concrete is a porous material that has the ability to soak up water (and waterborne contaminants). A crystalline integral concrete admixture is a relatively new and advanced technology that can be used in the place of traditional protective membranes. Proprietary chemicals in the material enhance the natural hydration process of cement, blocking the pores with millions of needle-like crystals—the concrete itself becomes the barrier to water penetration.
If you‘ve followed the necessary steps to prevent cracks from forming in concrete structures and how to control them and are unsuccessful, you may be faced with a leak that requires repair. The most common method is to inject a product into the crack in an attempt to fill it and make the crack waterproof.
Typically, a series of holes are drilled along the crack length so that they intersect the crack beneath the surface. A port is then inserted into each hole and a product is pumped into the crack. Common products include slurry mixtures of cement and/or clay with water, which can be cost effective for situations of minimal water flow and low-pressure.
A pool and foundation that required repair in Mexico.
For more challenging repairs, hydrophilic urethane products are recommended. These react with water to produce a foam that quickly sets within the crack to block water flow. Urethane foam injection will normally remain flexible and tolerate a slight amount of movement in the concrete; however, this flexibility deteriorates with time.
Avoid using an injection product such as epoxy. Epoxy injection is designed and used for restoring the strength and integrity of cracked concrete structural elements. These cracks must be relatively dry for the epoxy to achieve adhesion. Epoxy will not displace or react with water and therefore is largely ineffective at waterproofing a leaking crack.
All injection products suffer from the disadvantage of being somewhat hit and miss because both the drilling of the holes and injection of the material is done blind. Although the success rate can be high, achieving 100 per cent effectiveness is extremely difficult. Due to this, waterproofing and creating a completely dry structure is equally challenging and unreliable. Attempting to re-inject missed and still leaking areas can also be very difficult.
To ensure that a leaking crack is made completely waterproof it is necessary to open it and repair it directly. Cracks can be quickly chiseled open using an electric chipping hammer. This involves chiseling the entire length of the crack to create a deep and narrow chase. The chase is then filled with hydraulic grout and preferably with a crystalline waterproofing system.
Crystalline waterproofing systems provide both a short-term physical barrier to water and long-term chemical waterproofing through the growth of pore-blocking crystals. Crystalline waterproofing is roughly equal to injection in the skill and time required, but is significantly cheaper and far more reliable. The downside of the repair method is that it is rigid and will not tolerate movement of the concrete. With quality products and proper training, even badly cracked and leaking concrete can be successfully repaired to a dusty-dry state. Because repairs are inconvenient and often expensive, your best crack repair strategy is to focus on prevention and control.
Water is the enemy of hardened concrete. It causes expansive damage when it freezes, carries corrosive salts to attack the reinforcing steel, reacts with certain aggregates to cause disruptive expansion, and provides an essential ingredient for the growth of mould. Water-retaining structures like reservoirs, dams, and waste treatment facilities must prevent water from escaping; other structures such as tunnels and buildings must prevent water from entering.
For as long as anyone can remember, the construction industry has used the word ‗waterproof‘ to describe construction materials. People commonly refer to something as being waterproof if it holds water in or out and does not leak. However, the word waterproof is technically not defined this way. Most dictionaries define it as being impervious to water, that water cannot penetrate it at all. This raises a serious question: Can anything really be completely impervious to water?
The American Concrete Institute (ACI) is an international organization dedicated to the advancement of knowledge about concrete. Recognizing the problematic nature of the term ‗waterproof,‘ ACI has discouraged its use, stating:
Because nothing can be completely ‘impervious’ to water under infinite pressure over infinite time, this term should not be used.
Instead, ACI has over the years preferred to use the term ‗watertight.‘ However, its definition of this word is very similar to that of waterproof (which, in practice, remains far more frequently employed). Another commonly used industry term is ‗dampproofing,‘ which is defined by ACI to mean:
Treatment of concrete or mortar to retard the passage or absorption of water.
The word is typically used to describe liquid coatings or plastic sheets applied to the outside of concrete in contact with damp soil. Its goal is to prevent the absorption/wicking of moisture by the porous concrete.
Waterproof, watertight, dampproof… the trouble has been all three of these terms are imprecisely defined and tend to overlap each other in common use. This is especially problematic when they are used to define admixture products because testing methods and performance standards are relatively new and still being developed.
Where does the performance of a dampproofing admixture end and a waterproofing admixture begin? How can a professional expect to write a proper specification using such terms?
Advent of permeability-reducing admixtures
Permeability-reducing admixtures are not new; people have been adding things to concrete to reduce its permeability for centuries. These range from plant and animal products to modern plasticizers. Additionally, supplementary cementitious materials (SCMs)—such as silica fume, fly ash, and slag—are technically not categorized as admixtures, but can nonetheless be added to a concrete mixture to reduce permeability.
The ACI sub-committee responsible for concrete admixtures is Technical Committee 212, Chemical Admixtures. Its members recognized something needed to be done to clarify any confusion.
Professions needed more precise language with clearly understood meanings. Standardized testing methods and performance criteria that could be included in written specifications was also necessary.
The revised technical document, ACI 212.3R-10, Report on Chemical Admixtures for Concrete, contains a completely new section specifically written to address issues relating to permeability—reducing admixtures. This Chapter 15 describes three general categories for these materials:
Since products may contain one or more of these materials, they cannot simply be classified based on their ingredients alone. Instead, Chapter 15 classifies permeability-reducing admixtures by their ability to resist hydrostatic pressure:
Most products will fall into the PRAN classification. Water-repelling or hydrophobic materials can be very effective at preventing water absorption into concrete. They work by way of surface tension in the same way fabric treatment repels spills on clothing and furniture. They can be easy to use and cost—effective for applications not subjected to hydrostatic conditions.
However, even a modest amount of this pressure can overcome and push past the surface tension created by these materials. If acted on by water under pressure, concrete protected by only a PRAN may allow water to pass through.
Another term, ‗finely divided solids,‘ refers to materials that improve the packing of the concrete‘s ingredients, causing its pores to be as small as possible. These materials may also act to block the pores with loose particles. The category includes:
All these materials can significantly reduce permeability. However, because they cannot reliably plug all the pores and because they are unable to bridge cracks, they cannot be counted on to withstand hydrostatic pressure, especially over extended periods. For these reasons, finely divided solids are also classified as PRAN.
Crystalline chemicals react with water and the cementing materials in concrete or mortar to form distinct crystalline structures within the pores and small cracks of the concrete. These crystals effectively block the concrete‘s pores in a similar way to the finely divided solids. Additionally, these crystalline structures have the ability to bridge small cracks. Since any concrete structure has a high likelihood of developing cracks, this bridging ability is critical to successfully creating a watertight structure.
Further, since crystal formation only takes a small amount of crystalline materials in reaction with a larger amount of water and cementing materials, the admixture is not used up. This means when new cracks form later, and moisture begins to penetrate the concrete, more crystals grow to seal the crack. This self-sealing ability is unique to crystalline materials. Consequently, crystalline products have been shown to withstand very high hydrostatic pressures over long periods.
Specifiers should be aware not all products calling themselves ‗crystalline‘ actually fall into this category—some merely crystallize as they harden or dry. For example, sodium silicate is a solution that forms a crystalline structure as it dries, whereas ‗true‘ crystalline materials are PRAHs that cause a chemical reaction to form distinctly new crystals. More importantly, the material remains continuously reactive, allowing new crystal formation in the face of future moisture penetration. To be a PRAH, the crystalline material must possess this self-sealing ability.
Various testing methods have been used to indicate the permeability of concrete. Perhaps the most often referenced being ASTM C1202, Standard Test Method for Electrical Indication of Concrete‘s Ability to Resist Chloride Ion Penetration, more commonly known as the rapid chloride permeability (RCP) test.
There is much debate over the value of this method; its accuracy is an issue, as results from identical test specimens are often found to vary greatly from each other. More importantly, the test does not actually measure permeability—it deals with electrical conductivity, and there are many factors influencing this attribute beside permeability.
Other common test methods measure capillary absorption or wicking potential of concrete. These are useful for PRANs, but are inappropriate for PRAl·is because they exert no hydrostatic pressure.
A suitable testing method for PRAHs must directly measure permeability of the concrete when it is subjected to hydrostatic pressure. Chapter 15 cites U.S. Army Corps of Engineers (USACE) CRD C48-92, Standard Test Method for Water Permeability of Concrete, and two nearly identical European tests that accomplish this goal:
Each of these methods subject concrete specimens to water under pressure for a time. They measure the actual penetration and transport of water within the concrete matrix. Methods such as these come closest to replicating the actual service conditions of concrete in water-retaining structures in the field.
Chapter 15 of the ACI report recommends using a permeability-reducing admixture in any concrete that will benefit from moisture protection. Choosing to specify a PRAN or PRAH depends on the presence or absence of hydrostatic pressure. PRANs are appropriate for applications where resistance to water and waterborne chemicals may be needed, but hydrostatic pressure is absent. Foundations in contact with damp soil, concrete masonry units (CMUs), and exposed slabs, columns, or beams are just a few examples.
Where resistance to water under hydrostatic pressure is required, a PRAH must be used. Examples of these are:
Where the application is critical, it may be worthwhile to include a PRAH instead of a PRAN even when hydrostatic pressure is not expected. Elevator pits are a good example of this.
The final sections of Chapter 15 give advice for proportioning, batching, and quality control—much of which is good practice for most concrete work.
ACI-212‘s new Chapter 15 has given design/construction professionals several new tools. The identification and categorization of different materials shows not all permeability—reducing materials are the same. Its classification of various admixtures based on performance rather than chemistry has a more practical benefit. Chapter 15 also introduces new, descriptive, and much more precise language to employ in specifications. The Portland Cement Association (PCA) has already adopted this new language and included PRAN and PRAH in its book, Design and Control of Concrete Mixtures.
Chapter 15 recommends improved testing methods that closely replicate the real world. All of this helps industry professionals to choose the proper product for their application. With the assistance of ACI 212‘s new Chapter 15, Canadian engineers and architects can now agree that when protecting concrete from water not under pressure, a PRAN should be specified. In cases when one is building a watertight structure, a PRAH is what is needed.