Prevent thermal cracking
Mass concrete, usually thicker than 0.5m, may require some form of thermal management to prevent thermal cracking (thermal shock).
This occurs when thermal gradients build up in the concrete and results in a large temperature differential between the outer edge and middle (heart) of the mass. If this occurs then thermal cracking can occur, similar to pouring boiling water into a cold glass. Although with time and heat dissipation any formed cracks can close and autogenously heal, prevention is a much more sensible approach.
In order to prevent thermal cracking, typically limiting the differential between outer edges and the centre to 20°C is sufficient. This does vary with different aggregate types so further advice may be necessary. Hanson concrete technologists can advise you further.
Hanson concrete can calculate thermal properties of your concrete mix design including predicted peak temperature at x hours and the maximum expected differential at y hours once given a number of details pertaining to your placement methods.
Hanson can also reduce the impacts of temperature on your concrete by using bespoke engineered designs that restrict the temperature characteristics by reducing the heat generated by hydration. (Hydration is the exothermic reaction between cementitious binder and water.)
We can also utilise temperature data to predict appropriate striking times of formwork or post tensioning times based on temperature matched curing techniques. All of which can optimise construction time and help deliver value added engineering to the overall contract cost and programme timeline.
In addition to the above, we also have a range of concrete temperature models to calculate predicted concrete temperature at time of production. These can be beneficial during both extreme hot and cold weather to meet specification requirements.
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