As you would expect in a coastal climate as we have in Singapore, high humidity, salinity in the soil, salts in rainfall and exposure to a high level of airborne salts are greater along the coastline in comparison to an inland climate. High salinity levels can have an impact on the durability of some building materials such as concrete and masonry. They are susceptible to accelerated degradation such as cracking and spalling concrete caused by the higher concentration of salt and humidity in the environment.
The photo above is from an underground car park. It shows the process of breaking out spalling, unsound concrete and exposing reinforcing steel until sound concrete and clean non-corroded steel reinforcing are found.
After completion of material removal, concrete primers and rust inhibitor to the steel are applied prior to reinstating with a high build shrinkage compensated repair mortar. The treatment of concrete cancer must consider appropriate waterproofing as part of a complete solution. Otherwise, the repair work may remain a temporary fix as the underlying cause is likely to continue to affect the structure, depending on the situation.
We frequently carry out concrete cancer/spalling concrete repairs on the Queensland and New South Wales coastline (Gold Coast, Sunshine Coast, Sydney and Central Coast).
Spalling is often referred to as concrete cancer, as (like cancer) the problem is not obvious initially, and as the problem advances, the remedial repairs become increasingly more extensive.
Spalling/concrete cancer is a result of water with mineral salts entering the concrete structure causing the reinforcing steel to rust deep within the concrete. As steel rusts, it can expand up to seven (7) times its original size causing the surrounding concrete to be displaced and break away from the rebar or reo (reinforcing steel).
The small rust stain may just be a simple thing like a rusting steel tie, or it could be more comprehensive such as rusting reinforcement steel.
Cracks provide easy access for oxygen, moisture and chlorides, and thus, minor splitting cracks can create a condition in which corrosion and cracking are accelerated.
The deterioration of steel reinforced concrete, and is generally characterised by the appearance of:
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