Early thermal cracking in concrete
The addition of water to cementitious binders allows them to set, harden and gain strength. This chemical process of hydration is also exothermic, that is, heat is generated as a result of the process. The amount and rate of heat produced is dependent on the type of cement (or combination of cements) used, the amount of cement, the thickness of the concrete section, and external conditions such as ambient temperature, wind, solar gain and concrete placement temperature.
Like all other materials, concrete expands during heating up and contrracts during cooling. In a structure these movements can generate strains from within the element, increasing the risk of cracking. Cracking may be of little consequence for some structures, but for others it puts their intended servicebility at risk, with the potential to cause longer term operational or durability problems such as leakage of the structure or ingress of carbon dioxide or chlorides leading to reinforcement corrosion.
Methods are available to assess the risk of cracking for concrete structures and incorporate measures into the design to avoid or mitigate the risks of early age cracking. These measures range from careful materials selection and specification, changes in construction procedures, the use of enhanced curuing and protection measures, and the design of crack control reinforcement. CIRIA C660 “Early age thermal crack control in concrete” (2007) is an updated version of previous guidance that uses Eurocode design to assess and control the risk of early thermal cracking in concrete.
I have extensive experience of the assessment of early thermal behaviour (and sit on the Steering Committe of C660), and am able to provide comprehensive services for the analysis, interpretation and recommendation of measures to mitigate the risk of early thermal cracking in concrete structures.
Additional advice is also available on the investigation and remediation of early thermal cracking once it has occurred.
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