The Effect of Using Ground Granulated Blast Furnace Slag (GGBFS) as a Partial Substitute for Portland Cement in Fiber Concrete

Ground Granulated Blast Furnace Slag (GGBFS) is a residual material (waste) from the steel smelting process using Blast Furnace technology which has a chemical composition like cement, namely CaO, SiO2, Al2O3, and MgO. GGBFS can be used as a partial replacement for cement in Self Compacting Concrete (SCC). To increase the crack resistance of concrete, steel wire fiber can be used. Using GGBFS and steel wire waste fibers together in SCC concrete can produce concrete with high performance. This research aims to find the performance of fresh concrete and the mechanical performance of SCC concrete using GGBFS as a partial replacement for Portland cement and pieces of steel wire as added materials. The research was carried out by making concrete test specimens with a water cement factor (FAS) of 0.30, with a steel wire cut fiber ratio of 40 equal to 1% of the weight of the concrete. The admixture used is Polynex HE658 superplasticizer produced by PT Nexco at 0.8% of the cement weight. Test specimens were made with 4 variations of using GGBFS which replaced Portland cement, namely 0% GGBFS, 10% GGBFS, 20% GGBFS, and 30% GGBFS. The research results show that the greater the use of GGBFS in fiber SCC, the greater the filling ability and passing ability of the concrete. The use of GGBFS and superplasticizers can also increase the compressive strength, tensile strength and flexural strength of concrete. The highest compressive strength, tensile strength and flexural strength were produced at a GGBFS variation of 20%. The use of GGBFS and superplasticizer can also reduce cement use by ± 20%.