Monitoring by resistivity and ultrasonic velocity of the effect of the w/c ratio on setting and hydration evolution

Resumen del trabajo presentado en el XIII International Congress on the Chemistry of Cement, celebrado en Madrid (España), del 3 al 8 de julio de 2011The period from the mixing of concrete constituents to 24h later is a crucial step for the future performance of the concrete, which justifies its detailed study from different perspectives. One present trend is based in the use of non destructive techniques, as the ultrasonic pulses, either as the impulse-echo method or the flight time of sound wave, from cement mixing with water. Regarding resistivity, it has been used some decades ago for the identification of the setting time and the conductivity has been used for the study of the pore solution chemistry. In this study is presented the joint analysis of both ND techniques applied to an ordinary Portland cement. In the case of the sonic pulse, the technique of velocity or flight time has been used. The results show the suitability of the sonic flight time to monitor the dynamic modulus of the material and through the resistivity, the formation of the pore network and in consequence of the mechanical strength. Then both techniques jointly analyzed are promising for the prediction to longer terms of the strength, porosity and likely of other hydration events