The effect of w/b and temperature on the hydration and strength of blastfurnace slag cements

CASTELLANO, C. C.; IRASSAR, E.F.; BONAVETTI, V. L.; DONZA, H.

CONSTRUCTION AND BUILDING MATERIALS

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2016 vol. 111 p. 679 - 688

0950-0618

he combined effect of water to binder ratio and the curing temperature on the progress of the hydration and the crossover effect on blastfurnace cements containing 40% (BFS40) and 80% (BFS80) of GGBFS was investigated. Tests were performed on pastes with w/b of 0.3?0.5 exposed to 20, 40 and 60 °C up to 365 days. The hydration progress was monitored by the amount of non-evaporable water and the calcium hydroxide by XRD. A quadratic response-surface model was used to model the crossover effect. Blastfurnace cements present high apparent activation energy (Ea), which is proportional to the GGBFS content in cement, causing a high sensibility to temperature. The non-evaporable water of blastfurnace cements increases with the w/b ratio, temperature and age. The high temperature increasing the early compressive strength and therefore the crossover effect appears after 7 days for PC, 28 days for BFS40 and it is not detected until 365 days for BFS80. The w/b ratio has little or no effect on this phenomenon. To improve the strength of blast-furnace cements, the w/b ratio and the curing temperature will be properly designed according the proportion of slag in cement.