Development of sustainable ultra-high-performance concrete containing ground granulated blast furnace slag and glass powder: Mix design investigation

Ultra-high performance concrete (UHPC) is one of the most important advances in concrete technology. Since UHPCs possess outstanding mechanical properties and durability, they require less material consumption and post-maintenance conventional concrete. This helps reduce the detrimental impacts of concrete structures on the natural environment. However, the high price and high carbon intensity of UHPCs are main hurdles for their wide adoption. Recently, studies have revealed that waste glass at a certain fineness exhibits pozzolanic behaviour. This paper investigates the effect of replacing cementitious components in UHPCs with "medium-size" glass powder (GP) on the workability, mechanical properties, sustainability, and cost efficiency of the UHPCs. While principal binders (cement and silica fume (SF)) were replaced by "medium-size" GP in Series I, ground granulated blast furnace slag (GGBFS) and coarse GP were simultaneously used to substitute for SF in Series II. Regardless of curing regimes, slag GP-UHPC mixtures always exhibited better workability and greater compressive/flexural resistance, indicating the great synthetic effect of GP and GGBFS substitution. In addition, results showed that up to 30% of GP replacement, most specimens yielded reasonable mechanical properties, high cost efficiency, and low carbon indexes compared to the reference mixture. Specifically, while workability reduced with the increase of GP portions in the GP-UHPCs, it rose with larger replacement percentages of SF in the slag GP-UHPCs. For both series, 20% replacement of GP was the optimal ratio, resulting in cost-saving and carbon-efficient mix designs with comparable compressive/flexural capacity.