DETERIORATION OF HEAT-CURED MORTARS DUE TO THE COMBINED EFFECT OF DELAYED ETTRINGITE FORMATION AND FREEZE THAW CYCLES/

The interaction between freeze/thaw (F/T) exposure and delayed ettring ite formation (DEF) and their combined effect on the performance of he at-cured mortar specimens are reported. The results show that heat-cur ed mortar, not subject to F/T, starts to expand gradually after a long induction period ([approx]150 days). This period is shortened and the extent of the expansion is increased as a result of F/T exposure. The longer the period of water storage at 20 degrees C before F/T exposur e, the greater the rate and extent of expansion immediately after F/T exposure and during the water storage period. The expansion observed i n heat-cured mortars seems to be associated with delayed ettringite ba nd formation. Mortar specimens that exhibit marked expansion show a co rresponding decrease in strength and increase in oxygen gas permeabili ty. (C) 1997 Elsevier Science Ltd.