Early-age heat development in GGBS concrete structures

Abstract

China accounts for approximately half of global steel production and more than 80 Mt of blast-furnace slag is generated every year as a by-product. About 80% of blast-furnace slag is recycled in China and the majority of this is used as an additive in low-grade composite cement or ‘blast-furnace cement’. This paper discusses the technical feasibility of using ground granulated blast-furnace slag (GGBS) in structural concrete for high-value applications in China. The effects of the slag on concrete compressive strengths are investigated experimentally at different curing temperatures. The influence of partial replacement of CEM I with GGBS on the heat development of concrete is investigated through isothermal calorimetry tests. The presence of slag contributes to a reduced heat output rate. The results obtained from the isothermal calorimetry tests are also used to simulate the heat liberation process in suspended concrete slabs using finite-element software. Finite-element modelling results, validated by semi-adiabatic calorimetry tests, indicate that partial replacement of CEM I cement with GGBS contributes to a reduced peak hydration temperature and this has a beneficial effect in hot-weather concreting.