Characterising fundamental properties of foam concrete with a non-destructive technique

Lightweight foam concrete has been developing rapidly in construction industry due to its sustainability, excellent thermal insulation, excellent fire resistance and affordability. It is desired to assess the performance of the foam concrete structure on site instead of testing isolated specimen in laboratory condition, as the changes in site environment and different construction procedure will affect the testing result. For on-site testing of foam concrete, non-destructive methods are required to avoid damage to structures. Ultrasonic pulse velocity method (UPV) is one of the attractive methods used for onsite testing of concretes due to its benefits such as accurate results, high sampling rate and cost-effectiveness. UPV method can determine various concrete properties such as strength, dynamic elastic constants, defects, uniformity and effects of curing time. However, for foam concrete application, the effect of high porosity on the UPV test results is largely unknown in current literature. Existing research explored the relationship between porosity and strength for metals, as well as the relationship between UPV and porosity for normal mortars. Yet no correlation between UPV and porosity for lightweight foam concrete is developed, which is very critical in the strength estimation and site quality control of the construction. In this research, a comprehensive laboratory experiment was designed to establish the correlations between UPV, porosity, and compressive strength using UPV experiments and compressive strength tests. New equations are developed which can be used as reference for estimating the mechanical properties of lightweight foam concrete using ultrasound testing technique in civil engineering practice.