Early age thermal cracking of mass concrete blocks with Portland cement and ground granulated blast-furnace slag

Abstract

Evolution of heat due to an exothermic reaction between cementitious materials and water plays a significant role in the temperature rise in mass concrete at an early age. The temperature gradient between the core of mass concrete and its surfaces leads to the development of thermal stresses and may cause cracking if these stresses exceed the evolving tensile strength of concrete. This paper presents the results of an experimental and finite-element investigation of heat generation and dissipation in full-scale mass concrete blocks 2 m × 2 m × 2 m in size. A concrete mix with 100% OPC and 70% cement replaced by GGBFS was used in these blocks. The temperature profile across the depth of the block was measured at the centre, side and corner of the block. A semi-adiabatic calorimeter was used to measure the heat of hydration of the two concrete mixes. Finite-element simulation of these blocks captured with good accuracy the measured evolution of temperature in the blocks. Numerical simulation was subsequently used to investigate the influence of the size of the blocks, placement temperature of concrete, ambient temperature, solar radiation and type of formwork on the temperature rise and the associated potential of cracking in the mass concrete blocks.