Investigation of the temperature change and heat evolution of mortar incorporating PFA and metakaolin

Temperature-time profiles of mortar cubes have been determined using a semi-adiabatic curing method for curing times of 160 h. The binders employed were metakaolin-portland cement (MK-PC), fly ash-portland cement (PFA-PC) and MK-PFA-PC blends, with a maximum PC replacement level of 40% and MK levels of up to 15%. Relative to PC mortar (and as previously reported by other workers), MK-PC mortars show an enhanced temperature-rise whereas in PFA-PC mortars the temperature-rise is depressed. In ternary mortars MK and PFA have a compensatory effect. Both MK and PFA delay the time taken to reach the peak temperature with MK producing the greatest delay. Partial substitution of MK for PC has only a minor influence on the total heat evolved by the mortar whereas partial substitution of PC with PFA produces a marked fall in the heat evolved. The temperature-rise of MK-PC mortars with respect to PC-mortar shows two distinct peaks which are attributed to a two-stage hydration effect. (C) 2002 Elsevier Science Ltd. All rights reserved.