Maximum temperature limits for hot-weather concreting

Q. What are the ACI building code requirements for placing concrete in a tropical climate? Some people in our office say we should specify a maximum permissible concrete temperature of 90 ºF (32 ºC). Others say a temperature higher than 90 ºF (32 ºC) is allowable if the concrete contains a set-retarding admixture.

A. ACI 301-20 “Specifications for Concrete Construction” and ACI 305.1-14 “Specification for Hot Weather Concreting” limit the maximum concrete temperature to 95 °F (35 ºC) at the time of discharge. This limit is for general types of hot weather construction such as pavements, bridges, and buildings, not mass concrete.

According to ACI 305.1-14, qualification of a concrete mixture with a maximum concrete temperature that exceeds 95°F (35 ºC) shall be supported by successful past field experience or preconstruction testing. The request for a maximum concrete temperature that exceeds 95°F (35 ºC) shall be submitted to the architect/engineer prior to concrete placement. Computer modeling to predict fresh concrete temperature could be used to assist in determining control measures but shall not be used as a substitute for preconstruction testing.

For more information and details on hot weather concrete, refer to ACI 305.1-14 and ACI 305R-20 “Guide to Hot Weather Concreting”.

For temperature, volume changes, and cracking problems associated with mass concrete refer to section 8 of ACI 301-20, ACI 207.1R-05 “Guide to Mass Concrete”, 207.2R-07 “Report on Thermal and Volume Change Effects on Cracking of Mass Concrete”, and 224R-01 “Control of Cracking of Concrete Structures”.

References: ACI 301-20; ACI 305.1-14; ACI 305R-20; ACI 207.1R-05; ACI 207.2R-07; ACI 224R-01; ASTM C1064

Topics in Concrete: cracking; hot weather; durability; placing; shrinkage