28 Apr Concrete stumps or stilts repair
Waterstop Solutions was engaged to inspect and repair 25 concrete stumps/stilts and a concrete slab entrance identified by the client as displaying signs of efflorescence.
Based on our examination only 12 of the 25 stumps and a section of the concrete slab showed evidence of pitting in the concrete. The affected stumps displaying signs of efflorescence caused by rising damp are in direct contact with bare soil underneath the building.
The damage to the concrete stumps by efflorescence appeared to be in the early to mid-stage with only two small sections of unsound concrete observed. When treated early, the risk of developing concrete spalling may be largely mitigated.
To treat the concrete stumps, we recommend the following:
- Perform concrete repairs to the two sections identified.
- Water-blast the concrete stumps and the concrete slab entrance to remove the efflorescence and prime the concrete for the application of a silicate-based, hardener densifier.
- Apply a silicate-based, hardener densifier to the concrete stumps and the concrete slab section to seal the concrete, reduce water permeability and to prevent water from travelling to the surface from within.
- Return after the hardener-densifier has finished chemically reacting with the concrete (a period of 30 days or more), to water-blast clean the concrete stumps and apply render coating to the stumps to improve the coverage of the steel reinforcements and the appearance of the stumps.
During the curing period, we recommend to wet down the concrete stumps every 2 days over the following week while the silicate-based, hardener densifier is chemically reacting with the concrete.
Is efflorescence just a cosmetic problem or could it pose a structural threat?
Efflorescence is caused when carrier moisture brings salts and other minerals to the surface of porous building materials such as concrete, bricks and mortars. The ground in which these materials can come into contact also contains salts and unsealed building materials that are in contact with the ground may be susceptible to efflorescence because they can absorb or wick water through capillary action. When the carrier moisture evaporates, the salts and minerals crystallise creating a build-up of efflorescence (free lime/calcium deposits) that appears as white/light grey/yellow staining or chalky powder on the surface. Sometimes it can mould and efflorescence can be confused by the untrained eye. Efflorescence will turn into powder if pinched between the fingers and it dissolves in water, while mould will not.
Efflorescence alone can be just an aesthetic problem. However, when efflorescence happens, it can be a symptom of moisture intrusion that potentially can lead to mould growth and/or structural damage if left untreated. The capillary action continues as water is drawn to the salts deposited on the surface. The water is attracted by the increasing salt concentration and creates a pressure that can exceed the tensile strength within the porous building material, such as the concrete stumps/stilts in this case, which can result in damage called pitting or spalling.
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If you have any issues with water ingress, rooftop leaks, leaking balcony, leaking basement, cracking concrete slabs, structural cracks, concrete deterioration, spalling concrete, concrete cancer, deteriorated joints, moisture, seepage, efflorescence, rising damp and/or high-flow active leaks in concrete structures, we would be happy to assist you. You are welcome to contact us with any questions that you may have.
Brisbane office: (07) 3205 1899
Email: [email protected]
Sydney office: (02) 9346 8308
Email: admi[email protected]
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