Energy-based evaluation of hardness testing with discrete element method

Abstract

Present paper focuses on the static hardness testing of porous construction materials. A series of experiments were conducted by the authors, during which the main strength properties of twelve different construction materials (normal and high strength concrete, concrete with supplementary cementing materials (SCM), limestones, ceramics, polymer concrete, etc.) were tested. Compressive strength, Young’s modulus and Brinell hardness of every material was measured and based on an energy-based approach a relationship between the variables was defined. Brinell hardness test is a commonly used method for estimation of strength of solid materials (e.g. metals), however in case of porous materials contradictory results can be found in the literature. Present research is aiming to find a general formula for porous materials with as less restrictions as possible. The Brinell hardness of the materials was determined with DSI (Depth Sensing Indentation) method, which is an updated form of the classical Brinell hardness test. The output of DSI test are the loading-unloading curves belonging to a predefined maximal loading force. Based on these figures the elastic, dissipated and total strain energy can be determined and a formula can be given to estimate strength parameters based on them. The results were validated by using DEM (Discrete Element Method), mainly focusing on concrete and the effect of SCMs. The model was set up based on the experimental data and DSI test was performed with the model as well. The results of the model were compared to the laboratory measurement results.