Experimental observation of factors influencing impact test of concrete compressive material properties

Abstract

Significant scatterings of dynamic strength of concrete materials are observed from different tests. Sources of causing such scatterings, among other factors, include the contributions of lateral inertia, friction confinement and coarse aggregates to dynamic strength increment. Most previous studies investigating these factors are based primarily on numerical simulations. Due to different numerical models adopted, inconsistent and sometimes contradicting conclusions are made. In the present study, systematic experimental tests are conducted to investigate the effects of lateral inertia and end friction confinements, and aggregate size and percentage on high-rate strengths of concrete material and to validate the proposed formulae in previous numerical studies. For direct assessment of a particular influencing factor, proper designs of the material mixtures, the specimen dimensions, and the boundary conditions have been considered in preparing the specimens. The dependency of the DIF (dynamic increase factor) of the tested specimens on the concerned factors is discussed. The findings from the previous numerical studies that lateral inertia confinement effect is dependent on the specimen diameter and strain rate are confirmed by the test results. The influences of aggregate size and volume on DIF are considerable, and cannot be neglected in experimental or numerical studies. It is also confirmed that the end friction confinement effect is sensitive to the strain rate and specimen geometry. The proposed formulae for correcting the DIF relations in previous studies are verified by the experimental data in this study.