Effect of binder dosage and the use of waste rubber fiber on the mechanical and durability performance of geopolymer concrete

This paper was designed to find solutions to the fact that the availability of natural aggregates in accordance with the standards used in concrete is gradually decreasing, the environmental problems caused by cement threaten our future, and the recycling of used tire waste is very difficult. The effects of three different binder dosages (300, 400 and 500 kg/m3) on the mechanical and durability properties of geopolymer concrete (GPC) samples were investigated in binder contents consisting of 98% granulated blast furnace slag (GBFS) and 2% nano silica. As for the aggregate composition, natural sand was used as the fine aggregate, while the waste rubber fibers (WRF) were substituted in different proportions (0%, 5%, 10% and 15%) of the coarse aggregate by volume. Following the solid part was obtained as described, the alkaline activation of GPC specimens was provided using a 12 M NaOH solution. At the end of 28-day curing period, compressive strength, flexural strength, splitting tensile strength, impact resistance, capillary permeability and elevated temperature performance properties were investigated in detail and the results obtained from the mentioned tests were also confirmed by microstructural analysis. Experimental findings revealed that the increase in binder dosage resulted in significant increases in all of the mechanical properties, and it was speculated that this was due to the formation of a denser and more compact microstructure compared to their counterparts produced using lower binder dosage. Besides the negative effects of WRF usage on compressive strength and resistance of elevated temperature, the other performance criteria such as flexural strength, impact resistance and splitting tensile strength values of GPC samples significantly improved with the usage of WRF. As a result, experimental findings demonstrated that the usage of waste rubber fibers in the production of GPC was advantageous in terms of some mechanical and durability properties. •The binder part, consisting of nano silica and GBFS, was activated with 12 M NaOH.•A positive effect of the use of WRF on mechanical properties except for compressive strength was observed.•It was observed that the degradation of WRF at high temperatures led to lower compressive strength values.•It was determined that waste rubber is a potential alternative to natural aggregates.•The obtained SEM micrographs were deemed sufficient to support the findings obtained from different experiments.