Thermal cracking in concrete members having large sections continues to be a concern for designers and specifiers of concrete. These issues are common to both large structural components in buildings and in civil engineering infrastructure projects. An example of the effects of severe temperature differentials is warping of thin external slab elements, which have resulted in cracking of concrete within a matter of days.
There is often a conflict for specifiers when high binder or high strength concretes are required for durability or structural requirements, and the associated heat of hydration characteristics of such concretes. An undesirable outcome with the use of such concretes may be thermal cracking resulting from the high heats of hydration of the binder.
Low heat concrete can reduce the incidence of thermal contraction cracking and provide designers with alternative means of obtaining more serviceable and aesthetically pleasing concrete elements.
The reaction of cement with water is exothermic therefore it produces heat. The more portland cement in the mix, the greater is the heat produced.
At Holcim we have a significant amount of information on heat of hydration and thermal cracking potential in concrete.
Much of our supplied concrete contains one or more supplementary cementitious materials. As these are either cementitious and/or pozzolanic, heat of hydration characteristics of concretes incorporating these can be reduced over that observed for Portland cement concretes.