Influence of Rubber Particle Size on Dynamic Energy Absorption of SBR-Modified Cementitious Composites

Concrete is one of the most widely used structural materials, and increasing demands for durability and dynamic resistance drive the search for improved and more sustainable solutions, including the use of waste-derived additives. This study investigates the effect of SBR rubber granulate with different particle-size distributions on the energy-absorption capacity of concrete composites under static and dynamic loading. A key objective was to enhance the material’s ability to dissipate blast-induced shock waves and to determine how rubber size and volume fraction influence fracture mechanics and impact resistance, relevant for designing energy-dissipating materials. Concrete of class C30/37 was modified with three SBR gradations (0.5/2.5 mm, 1.0/4.0 mm, 3.0/8.0 mm) at volume fractions of 10%, 20% and 30%. Static uniaxial compression and three-point bending tests were performed, recording complete load–displacement curves and determining the energy to failure as the area under the curve. Dynamic response was evaluated using a drop-weight impact tester with adjustable energy, supported by Digital Image Correlation and a Phantom TMX 7510 high-speed camera to identify crack initiation and full-field displacement evolution in time. The results showed a reduction in static strength with increasing SBR content, accompanied by enhanced post-peak deformability and higher energy absorbed to failure. Dynamic tests confirmed improved energy absorption and indicated a favourable particle-size range. The experimental data were used to calibrate a numerical model including fracture energy, deformability and strain-rate sensitivity. The findings confirm that SBR-modified concrete offers enhanced dynamic resistance and potential for structural elements subjected to impact or blast loading.