Experimental study and numerical simulation on the formation of microstructure in cementitious materials at early age

The formation of microstructure in early age cement paste and concrete was examined with an ultrasonic experimental set-up, Research parameters included the influence of curing temperature (isothermal curing at 20, 30 and 40degreesC), water/cement ratio (0.40, 0.45 and 0.55) and amount of aggregate. In parallel with the experiments. the cement hydration model HYMOSTRUC was utilized to simulate the formation of the microstructure, In this study, the cement paste was considered as a four-phase system consisting of water, unhydrated cement, hydration products and that part of the hydration product that causes the contact between the hydrating cement grains (so called "bridge volume"). A correlation has been found between the growth of bridge volume calculated with the model and the changes in the pulse velocity. It is believed that ultrasonic pulse velocity (UPV) measurements can represent a valuable tool to investigate the development of the microstructure at early age. (C) 2002 Elsevier Science Ltd. All rights reserved.