Hydration of cement is an exothermic reaction and in large-volume pours, the temperature can rise significantly.

In the core of sections greater than 2 metres thick, the temperature rise will nearly be adiabatic. The cement content per cubic metre fundamentally determines the heat generated, and values of peak temperatures of the order of 70–80°C are possible.

Large volume pours decrease the number of necessary joints

The heavily reinforced foundations required to carry significant design loads tend to create situations where the construction of joints or temporary stop-ends are impossible to form.

The drawback of cracks that might transpire where construction joints are not used, is relatively minor. However, the importance of these cracks should be considered in relation to the structural requirements of the section, together with considerations of durability.

• For the protection of reinforcement: a maximum crack width should be considered. In addition, the elimination of joints removes potential cracks and zones of weakness, which are often highlighted in structures that are required to be water-retaining.
• The designer can have significant impact on the construction process: they should work closely with the contractor. The designer must ensure that all aspects of the specification are compatible and will work with the construction process.
• Achieve a balance in the concrete mix: between specified strength, durability, heat of hydration and the requirements for placing and compaction. The strength and minimum cement content should not be over specified.
• To control the occurrence of early age thermal cracking: specify allowable limits on the peak core temperature and on temperature differentials. The differential is usually for a post construction period and relates to the difference between the core and the outside surfaces and between previous pours.

Substitute Golden Bay EverSure Type GP Cement with EverPlus Class C Fly ash will largely reduce the amount of heat produced through its’ pozzolanic reactions

1. 30% EverPlus Class C Fly Ash:
   Concrete containing 330 kg/m3 of EverSure when placed at a temperature of 20°C is likely to have a peak adiabatic temperature rise of approximately 70°C – which is a typical specification limit imposed. The replacement of 30% EverPlus Class C Fly Ash on a one for one basis will reduce this peak temperature by approximately 12°C and will have a significantly reduced temperature gradient.
2. A pre-blended binder of EverSure Type GP and EverPlus Class C Fly Ash:
   This combination is available at specified replacement levels from our product solution range – providing logistical and operational advantages if silo infrastructure at a ready mix concrete plant is limited.

Close collaboration between designer, contractor and ready mix supplier are critical for a successful outcome.