Analysis of Cracking Risk in Early Age Mass Concrete with Different Aggregate Types

The main cause of early age cracks often observed in massive concrete structures is inhomogeneous volume changes associated with thermal and moisture gradients occurring in these structures due to the hydration process. Significant impact on a temperature rise which is the main reason of significant changes in concrete volume, and as a consequence, on the cracking risk in the massive foundation slab has the type of aggregate, which forms the thermal properties of concrete. In the paper, thermal properties of concretes made with different aggregate types and their impact on the cracking risk in a massive concrete slab are discussed. Thermal conductivity and heat capacity of concrete with different aggregate types have been experimentally measured and next used in the numerical study. The influence of gravel (consisting mainly of quartz), basalt, granite and limestone aggregate on the temperature development, stress level and the cracking risk has been studied in the numerical tests. The presented numerical analyses are conducted for a massive foundation slab with use of the original numerical model and computer programs TEMWIL and MAFEM. It has been shown that the use of the aggregate with the appropriate thermal properties may result in the reduction of thermal stresses and the cracking risk in early age concrete slabs.