Correlation Between Compressive Strength and Ultrasonic Pulse Velocity (UPV) of Fly ash Cenosphere Concrete

Abstract

The utilization of Fly Ash Cenosphere (FAC) as a substitute for sand in concrete presents a practical solution to address environmental concerns stemming from the disposal of fly ash. However, it's essential to recognize that the strength properties of FAC concrete differ from those of conventional M sand concrete. To effectively manage design and quality control in construction projects, it becomes necessary to explore the applicability of non-destructive testing methods for estimating the in-situ mechanical characteristics of FAC concrete. In this context, the current research study seeks to establish a connection between compressive strength and ultrasonic pulse velocity (UPV) as a means of predicting the compressive strength of FAC concrete using UPV testing. The study also investigates the influence of FAC replacement levels and curing duration. The experimental program involves a concrete mix proportion of 1:1.95:1.96 with a constant water-cement (w/c) ratio of 0.5. FAC replaces M sand in varying percentages from 10% to 50%, in increments of 10%, while the control mix maintains 100% M sand content. Concrete samples are cast, cured at ambient temperatures, and subsequently tested at curing ages of 7 days, 14 days, and 28 days. The consistent findings demonstrate that FAC concrete consistently exhibits lower UPV values and compressive strength compared to the control concrete across various replacement levels, curing durations, and mix compositions. Additionally, empirical relationships were established between compressive strength and UPV, displaying a strong exponential nature and a high correlation, ranging from 0.91 to 0.99. The effectiveness of these developed empirical equations for predicting compressive strength is validated through a comparison with actual test results.