Injection of liquid nitrogen into concrete truck
As a global leader in advancing concrete knowledge, ACI’s goal is to keep concrete industry professionals up to date with the latest information.
For example, here’s a recent exchange from ACI’s Q&A section:
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 301-16 “Specifications for Structural Concrete” 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.
Hot weather concreting is defined by ACI as “one or a combination of the following conditions that tends to impair the quality of freshly mixed or hardened concrete by accelerating the rate of moisture loss and rate of cement hydration, or otherwise causing detrimental results: high ambient temperature; high concrete temperature; low relative humidity; and high wind speed.”
Various adverse effects on the properties and serviceability of concrete are brought on by hot weather. Just one of those is the effect on strength—concrete mixed, placed, and cured at elevated temperatures normally develops higher early strengths than concrete produced and cured at lower temperatures.
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