Mechanical Properties of High-Strength Self-Compacting Concrete.

In this research work, the mechanical properties of high-strength self-compacting concrete (HSSCC) were studied. Three mixes were selected, having compressive strengths of more than 70, 80, and 90 MPa, respectively. For these three mixes, the stress-strain characteristics were studied by casting cylinders. It was observed during the testing that the binder content and water-to-binder ratio influence the strength of HSSCC, and slow changes in stress-strain curves were seen as the strength increased. The use of HSSCC results in reduced bond cracking, leading to a more linear and steeper stress-strain curve in the ascending branches as the strength of the concrete increases. Elastic properties such as modulus of elasticity and Poisson's ratio of HSSCC were calculated using experimental data. In HSSCC, since the aggregate content is lower and the size of the aggregates is smaller, it will have a lower modulus of elasticity compared to normal vibrating concrete (NVC). Thus, an equation is proposed from the experimental results for predicting the modulus of elasticity of HSSCC. The results suggest that the proposed equation for predicting the elastic modulus of HSSCC for strengths ranging from 70 to 90 MPa is valid. It was also observed that the Poisson's ratio values for all three mixes of HSSCC were found to be lower than the typical value for NVC, indicating a higher degree of stiffness.

Investigating the Flexural Behavior of a Two-Span High-Performance Concrete Beam Using Experimentally Derived Stress Block Parameters.

High-performance concrete (HPC) is increasingly used in construction due to its superior strength and durability. However, current stress block parameters used for designing normal-strength concrete cannot be safely applied to HPC. To address this issue, new stress block parameters have been proposed through experimental works, which are used for designing HPC members. In this study, the behavior of HPC was investigated using these stress block parameters. Two-span beams made of HPC were tested under five-point bending, and an idealized stress block curve was derived from the experimental stress-strain curve for grades 60, 80, and 100 MPa. Based on the stress block curve, equations for the ultimate moment of resistance, depth of the neutral axis, limiting moment of resistance, and maximum depth of the neutral axis were proposed. An idealized load-deformation curve was also developed, which identified four significant events: first cracking, yielding of reinforced steel, crushing of concrete with spalling of cover, and ultimate failure. The predicted values were found to be in good agreement with the experimental values, and the average location of the first crack was identified to be 0.270 L, measured from the central support on either side of the span. These findings provide important insights for the design of HPC structures, contributing to the development of more resilient and durable infrastructure.