Factors influencing ultrasonic pulse velocity in concrete

The hydration process of Portland cement triggers reactions of stabilization of minerals from the contact of the clinker with water, which is the Hydrated Calcium Silicate (C-S-H), the Etringite (3CaO.Al2O3.3CaSO4.32H2O) and the Portlandite (Ca(OH)2). In order to understand the effects of the evolution of hydration in cement, it is possible to apply non-destructive tests. In this context, the objective of this work is to evaluate the influence of the type of cement, the curing age, of the format and humidity of the test specimens of concrete in the ultrasonic pulse velocity (UPV). In order to do that, 36 cylindrical test specimens (10 x 20 cm) and 9 cubic ones with 25 cm of edges, with mix proportion of 1:2,7:3,2 (cement/sand/gravel), water/cement ratio of 0.58 and three types of Portland cement (CP II-Z-32, CP IV-32 RS and CP V-ARI) were molded. With data obtained it was possible to correlate the increase of concrete strength along time (at ages of 7, 14, 28, 70 and 91 days) with the increase of the ultrasonic pulse velocity. Besides, it was possible to prove the direct influence of the concrete moisture and of the degree of hydration in the UPV. The shape of the test specimen generally had no influence on the results, except in the case of cement CP V ARI.

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