Durability of ultra-high-performance self-compacting concrete with hybrid fibers

Today, the concrete industry is considered one of the most important industries in the world. The need to build high-order structures with more strength and with structural elements with smaller dimensions and high durability has encouraged investigators to search for more resistant and more durable concrete for construction. Therefore, the use of concrete with self-compacting properties, ultra-high performance and fiber-reinforced matrix microstructure can help construct high-performance and high-durability structures. In this experimental research, the engineering properties of fiber-reinforced ultra-high-performance self-compacting concrete containing three kinds of pozzolan (microsilica, nanosilica and fly ash), basalt aggregate, carbon fibers and basalt fibers were studied. The engineering properties that were considered in this research were analysed using various methods of testing: mechanical properties tests, including compressive strength and tensile strength tests; durability tests, including volumetric water absorption, special electrical resistance and rapid chloride permeability; and microstructural analysis, including scanning electron microscopy. Experiments were carried out in accordance with relevant standards, and concrete engineering properties discussed in this paper improved in all cases compared with those of the reference concrete. The results indicate the effect of the addition of pozzolans, hybrid fibers and basalt aggregate. Also, significant improvements in mechanical properties and durability distinguish this concrete from ordinary concrete.