Research on Indirect Evaluation Methods for UHPC Strength

ABSTRACT This paper systematically explores indirect evaluation methods for determining the strength of ultra-high performance concrete (UHPC). It also examines the feasibility of ultrasonic testing, impact elastic wave testing, combined methods, and pull-out testing for indirect strength evaluation. In addition, it establishes corresponding strength prediction formulas and verifies their accuracy and applicability. The results indicate that the ultrasonic-based strength prediction formula exhibits high precision, with an average relative error of just 2.68 %. It is also applicable to various types of UHPC. The impact elastic wave-based formula also demonstrates high accuracy but is limited to UHPC with similar material properties, restricting its applicability range. The combined formulas, which integrate rebound hammer testing with either ultrasonic or impact elastic wave methods, do not show significant improvement in accuracy compared with the single-method formulas. The post-install pull-out method-based formula achieves high precision, with an average relative error of 1.79 %. It also demonstrates excellent applicability.