Effect of Mix Design Parameters on the Compressive Strength of Ultra-High Performance Alkali-Activated Concrete

This study investigates the influence of mix design parameters on the compressive strength of one-part ultra-high-performance slag-based alkali-activated concrete (UHP-AAC). In contrast to cement-based ultra-high-performance concrete (UHPC) with high cement consumption and associated CO۲ emissions, UHP-AAC utilizes industrial by-products such as ground granulated blast furnace slag and silica fume to reduce environmental impacts. While previous studies primarily focused on two-part alkali-activated systems, limited research has been dedicated to developing one-part UHP-AAC, particularly regarding the combined effects of mix ratios and recycled steel fibers. In this research, slag and silica fume were used as precursors, sodium metasilicate pentahydrate as solid alkali activator, glass powder as filler, and silica sand as aggregate. Some mixtures incorporated recycled steel fibers. The investigated mix proportion parameters include the silica fume-to-binder ratio, metasilicate-to-binder ratio, sand-to-binder ratio, water-to-binder ratio, and recycled steel fiber content. Additionally, quartz powder was compared with glass powder as an alternative filler in terms of its effect on compressive strength. Specimens were wrapped in plastic sheets during the curing process to minimize water loss. The results show that incorporating recycled steel fibers significantly enhanced compressive strength in the range of ۰-۵%, while decreasing water-to-binder and silica fume-to-binder ratios consistently improved performance.

Keywords:

Alkali-Activated Concrete , Ultra-High Performance Concrete , Mix Design Parameters , Compressive Strength