Technical Questions

How to Control Mass Concrete Temperature during Construction

Q. How can mass concrete temperature be controlled during construction?

A. The four elements of an effective temperature control program, any or all of which may be used for a particular mass concrete project, are:

• Cementitious material content control, where the choice of type and amount of cementitious materials can lessen the heat-generating potential of the concrete;
• Precooling, where cooling of ingredients achieves a lower concrete temperature as placed in the structure;
• Postcooling, where removing heat from the concrete with embedded cooling coils limits the temperature rise in the structure; and
• Construction management, where efforts are made to protect the structure from excessive temperature differentials by knowledge of concrete handling, construction scheduling, and construction procedures.

The temperature control for a small structure may be no more than a single measure, such as restricting placing operations to cool periods at night or during cool weather. On the other extreme, some projects can be large enough to justify a wide variety of separate, but complementary, control measures that can include the prudent selection of a low-heat-generating cement system including:

• The use of pozzolans;
• The careful production control of aggregate gradings and the use of large-size aggregates in efficient mixtures with low cement contents;
• The precooling of aggregates and mixing water (or the batching of ice in place of mixing water) to make possible a low concrete temperature as placed;
• The use of air-entraining and other chemical admixtures to improve both the fresh and hardened properties of the concrete;
• The use of appropriate block dimensions for placement;
• The coordination of construction schedules with seasonal changes to establish lift heights and placing frequencies;
• The use of special mixing and placing equipment to quickly place cooled concrete with minimum absorption of ambient heat;
• The evaporative cooling of surfaces through water curing;
• The dissipation of heat from the hardened concrete by circulating cold water through embedded piping; and
• The insulation of surfaces to minimize thermal differentials between the interior and the exterior of the concrete.

References: ACI 301-20; ACI 207.1R-05; ACI 207.2R-07; ACI PRC-207.4-20

Topics in Concrete: Mass Concrete; Specifications