Cracks that are not structural have no impact on the integrity or strength of the concrete structure, but have an aesthetic effect on the structure. However, if left untreated, they can develop into a serious problem due to the possibility of materials, water, and chemicals penetrating the concrete structure.
Cracks that are considered to be fine and small (less than 0.3 mm in width) are generally considered acceptable as part of minor settlement. However, if you are unsure of the status of a crack, we recommend having it inspected and diagnosed to determine the severity of the crack, the cause of the crack, whether a repair is required and if so, what would be the most effective method.
Durability and watertightness can be compromised by cracks of 0.3 mm or more. Concrete deterioration results from this, affecting its strength and durability.
In addition to addressing the cracks themselves, successful long-term repair procedures must also address the causes of the cracks. A qualified and licensed professional should be consulted before making repairs to concrete structures. Inappropriate repair methods can lead to further damage. A concrete structure’s repair will depend on the crack width, depth, if it’s dormant or live, as well as its service conditions.
Once the cause and significance of the concrete cracking has been diagnosed by a qualified and licenced inspector, it is important that accurate repair methods are followed. The selected repair methods are based on an evaluation of the crack and the repair’s objective(s).
Concrete crack repair objectives:
The key to successful crack repairs is having an understanding of the causes of the cracking and also whether the cracks are dormant or active.
Repair of Dormant cracks – Dormant cracks are stable and future movements are not anticipated or in other words, unlikely to open, close or extend further. Cracking caused by drying shrinkage and thermal shrinkage will be active cracks at the beginning but may eventually stabilise and become dormant.
Fine hairline cracks may not need any repairs however, these cracks may prove to be a future durability problem. We recommend sealing them by installing a bonded overlay or surface treatment as a protective coating. (If the fine crack is non-dormant, we would recommend v-cutting it and seal it with appropriate sealant material to accommodate for the potential movement). These treatments will aid in protecting the concrete from water ingress and other destructive environmental influences.
Wider cracks may be sealed by epoxy, polyurethane or acrylic resins followed by a protective coating or membrane.
Repair of Active/Non-dormant cracks – Active/dynamic/live concrete cracks are expected to experience further movement and growth. The cracks may be resulting from continuous foundation settlement or the cracks are acting as contraction and expansion joints.
These cracks should be treated as if they are the moving joints and the repair should cater for the anticipated potential movement. V-cutting along the line of the crack and then sealing it with appropriate sealant material will allow movement and protect against further expansion of the crack and possible water ingress.
Active/dynamic/live cracks can effectively be repaired with high-pressure polyurethane injection, which may be followed by installation of a joint-seal and protective coating or membrane.
When to use Epoxy
If cracks measure 0.05 mm or more in width, epoxy injection can restore structural integrity and reduce water penetration through concrete cracks.
Epoxy resin with low viscosity is mainly used to repair structural cracks that are not anticipated to move in the future (dormant cracks). In the case of cracks subject to subsequent movement, an epoxy resin repair may not be feasible.
Unless the epoxy resin is designed to withstand water during the curing process, epoxy resins can have difficulty setting and achieving the desired strength when present with water.
When to use Polyurethane
Polyurethane resins are excellent for sealing wet and leaking cracks and cracks that are not dormant/active. Water leaks can be repaired using this method by injecting highly water-reactive resin into cracks under pressure. As soon as the product comes into contact with water, it starts to foam and expand, filling the crack, forming a strong bond with the concrete and preventing future leaks. Repairs are permanent and can be applied to either active or dormant cracks. Among the benefits of polyurethane crack injection are its strength and flexibility.
For recommendations on crack repair methods, detailed preparation and application guidelines and application, please contact Singapore Waterproofing for relevant information and site inspection. Contact us
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