Assessment of Time-dependent Temperature Behaviour in Immature Concrete Walls using Numerical Analysis

Abstract

Hydration of cement is exothermic and the consequent temperature development leads to non-structural cracking in immature concrete. The maximum internal temperature drop (T1) is a governing parameter towards thermal cracking, and for structural deigns, T1 values recommended in the codes of practice are commonly used. Past investigations show that such recommendations could be too conservative. Amid the complexity of concrete thermal behaviour, one good prediction option is to use numerical methods. In this light, this study attempted to formulate recommendations for T1 via finite element (FE) analysis. First, a commercial FE software was validated for two distinct experimental results and, second, the FE application was used to predict the temperature in concrete walls. The variables were: wall thickness (300 1000 mm); cement composition (350 560 kg/m3); and plywood/steel formwork types. Semi-adiabatic experiments were conducted to obtain the rate of heat evolution in concrete. The numerical results showed that the predicted T1 values were considerably lower than those recommended in two currently practiced guidelines. The observed disparity was in the range of 22% 34%. It was also shown that T1 could be further reduced by about 15% and 23.5% through supplementing the mixes with fly ash by 20% and 35%, respectively.