Heat of hydration and mechanical properties of mass concrete with high-volume GGBFS replacements

Abstract

This paper examines how the high-volume replacement of ground granulated blast furnace slag (GGBFS), one of the most widely used mineral admixtures for concrete production, affects the mechanical and heat of hydration characteristics of concrete through both laboratory and mock-up tests. Mechanical properties such as compressive strength, splitting tensile strength, and elastic modulus, as well as thermal properties such as adiabatic temperature rise, isothermal calorimetry, and in situ hydration heat developments in a full-scale specimen were measured. The results have shown that the high-volume GGBFS replacements substantially promoted mechanical properties of concrete while effectively reducing early-age temperature rises in the presence of CaCO3-based alkali activator. The hydration temperature evolutions measured using adiabatic temperature rise tests were in good agreement with those measured in the full-scale specimens. The isothermal calorimetry test results revealed that both the GGBFS content and availability of alkali activator largely affected the reaction kinetics of GGBFS blended cement paste. From the findings of this study, the high-volume GGBFS replacement appears a promising strategy to alleviate early-age thermal stresses and potential cracking risk in mass concrete by reducing the temperature gradient between the surface and interior of a full-scale specimen (1.5 × 1.5 × 2.5 m) by 5.3 °C and the hydration temperature rise by 11.3 °C while significantly improving the strength characteristics.