Concrete Cancer Information for Adelaide
Cracking, crumbling exposed rusty reinforcement steel are all signs of spalling Concrete Cancer.
The durability of a concrete structure is affected by original design faults, poor detailing, the use of unsuitable materials, shortfalls in workmanship and lack of routine maintenance. These inadequacies accelerate penetration of the concrete by atmospheric carbon dioxide and water borne chloride ions from the environment.
Concrete breakdown occurs when concrete is permeable or when the concrete cover to the steel reinforcement is deficient. Permeable concrete is caused by high water/cement ratios, low cement contents, inadequate curing and poor compaction. Lack of an effective waterproof membrane, blocked surface water drainage and leaking expansion joints are all means by which water reaches the surfaces of roof slabs, columns and beams.
Concrete with a high alkali content, reactive aggregates and sufficient moisture also puts a structure at risk from alkali - silica reaction.
Fine cracks may occur in tensile zones of reinforced concrete members under normal design loading conditions because concrete can only sustain a relatively small tensile stress before cracking develops.
Chloride attack is caused by the miniscule and highly mobile free chloride ion penetrating the concrete through water present in the pour structure. Through electrochemical action pitting corrosion occurs to the reinforcement.