Investigating the impact of TiO2 on the physical and mechanical properties of roller-compacted concrete pavements containing ground granulated blast furnace slag via response surface methodology

This study examines the effects of substituting ordinary Portland cement with 0%, 5%, and 10% of titanium dioxide (TiO₂), along with the addition of ground granulated blast furnace slag (GGBS) at levels of 0%, 30%, and 60%, on the physical and mechanical properties of roller-compacted concrete (RCC) pavement using the soil compaction method. Response surface methodology assessed the compressive strength at 28 and 90 days of curing and the flexural and split tensile strengths and water absorption at 90 days. The test outcomes indicated that using TiO₂ alone in the specimens improved compressive, flexural, and split tensile strengths while decreasing porosity and water absorption. The optimal results were achieved with a 10% TiO₂ concentration. Adding GGBS solely reduced the compressive strength after 28 days of curing. However, 30% GGBS on the 90^th day significantly improved compressive, flexural, and split tensile strengths, and 60% GGBS achieved the lowest porosity and water absorption. Using TiO₂ and GGBS together decreased strength after 28 days. However, after 90 days, a mix with 5% TiO₂ and 30% GGBS slightly improved strength. Employing TiO₂ and GGBS, whether individually or together, led to a decrease in both porosity and water absorption. The blend with 10% TiO₂ and 30% GGBS demonstrated the lowest values. The response surface method revealed that utilizing 10% TiO₂ and 39.3% GGBS individually results in the highest strength and the lowest porosity after 90 days. The most effective combination comprises 10% TiO₂ and 2.02% GGBS. Scanning electron microscopy images demonstrated that GGBS and TiO₂, whether applied individually or in combination, enhanced distribution, filled voids, and modified the microstructure of the RCC samples, leading to decreased porosity and increased density compared to control samples without TiO₂ or GGBS.