The semiquantitative determination and morphology of ettringite in pastes containing expansive agent cured in elevated temperature

The semiquantitative determination and morphological investigation of ettri ngite in the paste containing 10% expansive agent was done with XRD and SEM -EDS under the temperature match conditioning (TMC), simulating the hydrati ng condition in shrinkage-compensating massive concrete. Elevated curing te mperature over 70 degreesC impedes the formation of ettringite or even indu ces its destruction. The relative humidity in the TMC process and later cur ing period with ambient temperature is a crucial factor determining the qua ntity, morphology and, as a result, the expansive potential of delayedly fo rmed ettringite. Besides its amount, the morphology of ettringite is also a n important factor to influence its expansive effect. The great expansion t akes place only with the later formation of microcrystalline ettringite abu ndantly in the dense paste cured under water-saturated condition. (C) 2001 Elsevier Science Ltd. All rights reserved.