Hydration modulation measures to mitigate the negative effects of paving concrete in hot weather

Abstract

Concrete Placement above a temperature of 35°C (95°F) is typically prohibited in many specifications for construction due to concerns over early-aged cracking, early stiffening, increasing setting temperature, and reduction of ultimate concrete strength etc. A common way to control or modulate the concrete placement temperature has been to cool the concrete constituents (e.g., aggregates and water) or the concrete mixture by using ice or injecting liquid nitrogen. However, these temperature modulation measures often increase the cost of the concrete. In the present study, an attempt has been made through laboratory testing to investigate the effect of hydration modulation measures such as modifying mixture proportions in terms of fly ash proportions in order to combat the negative effect of high temperature placement. Use of fly ash contents greater than 25-30% is an affective way to control the high heat generation and excessive drying shrinkage that is characteristic of high placement temperature and can mitigate the negative effect of high set temperature gradients that can result from placing artificially-cooled concrete under hot weather conditions.