The materials that are commonly used for curing horizontal surfaces, such as roads, pavements, domestic, and industrial floor slabs include:
• Proprietary Spray Applied Membrane
• Impervious Sheeting Laid in Close Contact with the Concrete Surface
Early curing of slabs is vital to minimise the risk of plastic shrinkage cracking, especially in climatic conditions that experience a combination of high temperatures with strong drying winds.
Spray applied curing compounds are rated by their manufacturers according to the efficiency with which they provide a barrier to evaporation. This is measured as a percentage of total water retained in the concrete.
Research has shown the effects of delay in the application of curing compounds to flat slabs and formed vertical surfaces through the process of measuring water loss from concrete specimens at various ages.
The results of the tests on a trowelled slab – where one of the best resin based curing compounds was used – clearly shows the rapidity with which water can be lost if curing is delayed.
Although membranes formed by curing compounds normally degenerate after a period of time, their use is not recommended on surfaces, which are subsequently to receive an applied finish. This includes use as a screed because of the likelihood of reduced bond.
Water is the most effective and cheapest curing medium but it is seldom used because of the practical problems associated with its supply, containment, and ultimate disposal. Materials like wet hessian or wet sand are sometimes utilised but they must be kept continually wet and not be allowed to dry out.
In extreme weather conditions, special precautions are necessary to minimise evaporation of hydration water and to control temperature differentials.