Study on Coupling of Glass Powder and Steel Fiber as Silica Fume Replacement in Ultra-High Performance Concrete: Concrete Sleeper Admixture Case Study

To investigate the substitution of silica fume (SF) with the coupling of glass powder (GP) and steel fiber (STF), a concrete sleeper admixture (CSA) contains SF is considered as the reference concrete admixture. The use of high SF content in CSAs has negative effects on concrete rheology. Furthermore, it decreases the extensive use of ultra-high performance concrete (UHPC) in concrete markets that can mainly be caused by the limitation in available resources and the high cost of SF production. The substitution of SF with GP is insufficient; therefore, the possibility of using the coupling of GP and STF as a SF replacement has been researched. In this regard, 0.5%, 1 % and 1.5% steel fiber by concrete volume and 5%, 10% and 15% glass powder and silica fume by weight of cement content have been investigated. It is found that concrete admixture with the coupling of STF and SF improves all the characteristics of the concrete. Additionally, the coupling effects of GP and STF are better than that of the SF and STF. Based on the synthetic consideration of the performance and cost, the combination of 10% GP and 1.5% STF is optimal in case of CSA mechanical performance.