Thermal crack reduction of large mat foundation using inserted precast lightweight

Abstract

A large mat foundation has become more popular among tall building construction. During construction, its thermal crack problem, due to temperature difference between concrete surface and concrete core generated from hydration reaction, is concerned. Consequently, the induced concrete stresses may higher than tensile strength in early age concrete which has not been fully strength developed. This thermal crack problem negatively affects the durability of a large mat foundation. This research aims to study and present an alternative solution by inserting concrete core with precast lightweight concrete which can reduce the heat from hydration reaction and absorb the heat at concrete core. This study uses 3D finite element model to predict temperature and stress inside 2 large mat foundations. Actual temperatures of the large mat foundations were also measured, and the results were used to improve the accuracy of the models. Then, the models with precast lightweight concretes partially replaced into mat foundations in small stress region is studied. The thermal stress analysis of the mat foundations with and without precast lightweight concretes is compared in order to demonstrate the efficiency in reducing the risk of thermal crack in large mat foundations.