A new approach to determine autogenous shrinkage of mortar at an early age considering temperature history

Shrinkage, settlement, and thermal deformations of concrete start to develop as soon as the casting is finished. The majority of standard tests currently used to measure free deformations are carried out on hardened concrete. Therefore, the prediction of thermal and other stresses at an early age cannot be determined. This article describes the design and the operation of an experimental device used for measuring the volume change of mortar in relation to the real temperature history. Measurements are carried out on a mortar having a water/cement (W/C) ratio of 0.35 and started approximately 20 min after the addition of water in the mixture up to 24 h of hydration. The measured deformation includes autogenous shrinkage and thermal expansion or contraction caused by the temperature changes induced by the heat of cement hydration. An experimental method is proposed to uncouple these deformations. The investigations show that the autogenous shrinkage amplitude is strongly affected by the temperature history of mortar. Therefore, for a good estimate of the shrinkage amplitudes of cement-based material, temperature must be taken into account in testing. (C) 2000 Elsevier Science Ltd. All rights reserved.