Mechanical Properties of HS⁃HDC Based on Orthogonal Tests

To prepare a low-carbon and cost-effective high-strength and high-ductility concrete （ HS-HDC ）， the paper designed 16 groups of orthogonal tests with 5 factors and 4 levels of coal gangue powder， silica fume， PVA fibers， water-binder ratio， and sand-binder ratio， three tests of uniaxial compression， four-point bending， and electron microscope scanning were carried out to explore the influence of each factor on the mechanical properties of HS-HDC and its microscopic mechanism. The test results showed that the integrity of the uniaxial compression failure specimen was good. When the fiber volume content was not less than 1.0%， the surface cracks of the failure specimen were vertically distributed， and the higher the fiber content， the smaller the surface crack width of the specimen. The coal gangue powder and water-binder ratio significantly affected the compressive strength， with contribution rates of 44.83% and 33.56%， respectively. The four-point bending specimen exhibited two failure forms： single crack and multiple cracks， demonstrating a typical three-stage failure mode. Only PVA fibers had a significant effect on the bending strength， with a contribution rate of 66.10%. The comprehensive mechanical properties of the H5 mixture ratio （ coal gangue powder 0.6， silica fume 0.14， PVA fibers 1.7%， water-binder ratio 0.3， sand-binder ratio 0.5 ） were the best. The cubic compressive strength was 69.0 MPa， the flexural strength was 19.7 MPa， the equivalent flexural toughness was 108.9 kJ/m³， and the tensile strain capacity was 1.05%. Cement and fibers were the two most critical components that affected embodied energy and embodied carbon. Using solid waste to replace part of cement was a very effective way to reduce carbon emissions.