Estimation of geopolymer concrete strength from ultrasonic pulse velocity (UPV) using high power pulser

The objective of this paper is to establish the relationship between the ultrasonic pulse velocity (UPV) and the compressive strength of geopolymer concrete. The specimens used in the studies were geopolymer concrete synthesized at ambient temperature with alkali activators of different concentrations. A high power pulser based equipment Ultra-β™ designed at CSIR-NML, Jamshedpur was used for the UPV measurement and the compressive strength tests were carried out at the concrete age of 1, 7, 28, and 90 days. The result shows that the relationship between UPV and the compressive strength of concrete is significantly influenced by age and alkali activator concentration. The UPV and the compressive strength of concrete increase with age, but the rate of increase varies with alkali activator. The study of hardened concrete at an age of 90 days was considered as the reference. It is found that with the same content of alkali activator, a clear relationship curve can be drawn to describe the UPV and compressive strength of hardened concrete. The standard error in estimating compressive strength from the UPV varies from 1.6MPa to 2.34 MPa. This paper highlights the UPV and strength relationship for geopolymer concrete prepared with different concentration of alkali activator.