Effect of partial replacement of cement with slag on the early-age strength of concrete

Abstract

Concrete structures are popularly used to provide open space areas that are often incorporated into the design of sports, social and industrial structures. One of the concerns with concrete structures, especially long-span concrete structures, is early-age thermal expansion and subsequent contraction as a result of the exothermic cement hydration reaction. Thermal contraction, externally restrained by vertical structural elements such as columns and shear walls, may cause thermal cracking if it exceeds the tensile strength of the concrete. The early-age thermal loading of cast-in-place concrete can be estimated through isothermal calorimetry, semi-adiabatic calorimetry and finite-element modelling. This paper discusses the efficiency of using finite-element modelling, based on the isothermal calorimetry results, for predicting early-age temperature development of in situ concrete. In addition, this work quantifies the beneficial effect of using ground granulated blast-furnace slag as a partial replacement of cement in structural concrete. The simulation results, validated via semi-adiabatic calorimetry, indicate reduced thermal loading due to the presence of slag. This can be taken as an advantage of using such slag in structural concrete.