An experimental assessment of fracture parameters and microstructure of concrete exposed to calcium leaching

This study delves into the intricate dynamics of calcium leaching in concrete, employing a comprehensive approach to evaluate its impact on structural durability. Accelerated calcium leaching tests, conducted in NH4NO3 solution with a constant pH under controlled conditions, simulate real-world scenarios. Using methods based on degraded thickness and calcium ion concentration, the study determines the acceleration factor, revealing the material's susceptibility to leaching. The chemical composition of the concrete is analyzed using SEM-EDX and XRD patterns with an energy spectrometer. A detailed examination of 145 concrete beams through Three-Point Bending tests over 150 days demonstrates a proportional decline in fracture toughness and tensile strength by 46.6 % and 44.2 %, respectively. A significant correlation emerges between calcium leaching and the reduction in fracture energy, with a 57.5 % decrease observed after 150 days, while compressive strength decreases by up to 38.57 %. This study introduces novel formulations for fracture parameters of leached concrete by employing the boundary effect method (BEM) to connect with concrete microstructure. This represents a pioneering advancement in fracture mechanics and provides a fresh perspective on understanding and addressing the structural effects of calcium leaching in concrete structures.