Measurement of setting process of cement pastes using non-destructive ultrasonic shear wave reflection technique

In this paper a new setup for measuring, setting and hardening process of cementitious materials, using a non-destructive ultrasonic shear wave reflection technique and design with the objective to be easily used in-situ, is described. Using the developed setup, the measurements can be performed by slight deepening of a measuring head into a paste in a mold or by placing the paste into a mold fixed on a measuring head. To test the proposed methodology, cement pastes with different compositions were prepared and exposed to different curing temperatures. Significant differences in the evolution of a change of a shear wave reflection coefficient Delta r in time were observed, indicating the ability of the method to monitor setting process of cement pastes. Moreover, some interesting phenomena in the solidification process of the materials can be identified. A linear relationship between development of Delta r and penetration resistance tip values in time was found, allowing development of a simplified procedure to determine both initial and final setting times of the material. (C) 2013 Elsevier Ltd. All rights reserved.