Spalling is a result of water entering brick, concrete or natural stone and forcing the surface to peel, pop out or flake off .
How can it be controlled especially for a blockwall with no reinforcement ?
When it has occured, how can it be corrected?
By good detailing of slab reinforcement, for blockwall used wiremesh
or textile woven fabrick
By avoiding volume expansion reactions in the concrete due to chemical and/or physical conditions.
Chemical:
a) Check the soundness of the cement (Le Chatelier test) for the presence of lime or magnesia which may cause volume expansion reactions in hardened concrete.
b) Use cements with low C3A to avoid possible volume expansive reactions with sulphate containing ground waters.
c) Avoid Aggregate Silica Reaction (ASR) by proper choice of aggregates
d) In general use sound aggregates. A sound aggregate will withstand both physical (like moisture movement) and chemical actions without spalling
Physical:
Fire safety of the building must be provided. Excessive temperatures due to fire causes spalling in concrete.
Chemical additives increasing water impermeability should help in this case. Currently, there are many products in the marked able to produce water impermeable concrete. Some produces water-tight concrete structure, others grow crystals in contact with water. The later concrete is able to self-heal cracks.
Also, these additives are not compatible with some others additives, so if you are using superplatisizer, for example, it should come from the same manufacturer.
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