Development of eco-friendly HPC using advanced hybrid multi-scale basalt fibers and ground mining materials

In recent decades, high performance concrete (HPC) has gained the attention of concrete industry due to its high strength and durability. However, the high consumption of manufactured fibers and Portland cement in HPC raised a high concern about its suitability. Accordingly, this research has been designed to investigate the effect of using hybrid multi-scale basalt fibers as natural fibers, in addition to ground mining materials as Portland cement partial replacement in the production of eco-friendly HPC. The basalt fibers were used at different contents of 1, 2, and 3% by weight of cementitious materials, with fiber length gradation examined across three hybridization levels incorporating four fiber lengths ranging from macro (30 mm) to micro (3 mm). The partial replacement of cement was conducted using eco-friendly ground mining materials namely, metakaolin (MK), silica flour (SF), and ground feldspar (FLs) at various replacement ratios. Several mechanical properties were measured such as; compressive strength, splitting tensile strength, flexural strength, and elasticity modulus. The results demonstrate that increasing the level of fiber hybridization and combining multiple basalt fiber lengths significantly enhanced the mechanical properties compared to mono-size fiber systems, resulting in HPC compressive, tensile, and flexural strengths increases of over 4%, 8.5%, and 6%, respectively, at the highest hybridization level. Moreover, the usage of eco-friendly supplementary cementitious materials in HPC helped in achieving better mechanical properties, denser microstructures, and better ultrasonic pulse velocity (UPV) values, which in turn aided in the development of eco-friendly HPC with better overall performance. The optimal content of MK and SF was 10%, while that of FLs was 5%, which was based on the mechanical performance, UPV, microstructure, and both environmental and economic assessment of HPC. This study has provided a more sustainable HPC with better mechanical performance, lower material cost with favorable environmental impact, and better eco-efficiency.