Triaxial compression and shear strength characteristics of two-stage concrete: an experimental study.

The research necessity stems from the need to understand and evaluate the performance of Two-Stage Concrete (TSC) under triaxial compression conditions, as prior studies have predominantly focused on uniaxial and biaxial testing of conventional concrete (CC). This study represents the first comprehensive investigation into the triaxial compressive strength and related mechanical properties of TSC, addressing a critical gap in the existing body of literature. Three different mixtures were prepared, including one CC and two TSC variants with varying cement content. The results and behavior of these mixtures were compared to assess their performance. Findings reveal that TSC, particularly those types with finer aggregates, demonstrates superior shear strength, achieving up to 52.4 MPa under dry conditions, in contrast to the 48.38 MPa observed in CC. Furthermore, TSC exhibits remarkable stress tolerance, withstanding up to 82.04 MPa, significantly outperforming CC, which withstands only 69.61 MPa under similar conditions. This behavior can be attributed to the higher coarse aggregate content, the increased interaction and contact points between coarse aggregates, the improved bonding between them, and the inherent properties of the grout. TSC also maintains a higher modulus of elasticity and internal friction angles, indicating superior deformation behavior and shear resistance. Additionally, TSC shows greater resilience to moisture, suggesting its potential suitability for use in variable moisture environments. These properties highlight the strength of TSC for high-load applications and its suitability for infrastructure prone to environmental fluctuations.