Study on the development of the microstructure in cement-based materials by means of numerical simulation and ultrasonic pulse velocity measurement

The formation of microstructure in cementitious materials was simulated with a numerical model. Simulation results have been verified by measuring the evolution of the ultrasonic pulse velocity (UPV). In this contribution, the applied computer-based cement hydration model is presented. The UPV measurements are also presented and evaluated. Experiments were performed on concrete mixtures with water/cement ratio 0.40, 0.45 and 0.55. The concrete was cured isothermally at 10, 20, 30 and 40 C. Correlations between the development of the microstructure and the evolution of UPV were found. Two critical processes were individuated. The first is the percolation threshold of the solid phase. The second is the full connectivity of the solid phase. Both in the experiments and in the numerical simulations it was possible to distinguish these critical stages. These stages are discussed and conclusions are drawn regarding the potential of numerical simulation models in the study of early age cementitious materials for quantitative analysis of hydration processes. (C) 2003 Elsevier Ltd. All rights reserved.