Abstract

Ambient-cured Alkali-Activated Mortars (AAMs) are developed incorporating Volcanic Ash (VA), powdered pumice (VP), ground granulated blast furnace slag (GGBFS) and their combinations. Powder form alkaline reagent (calcium hydroxide: sodium metasilicate = 1:2.5), silica sand and a one-part dry mixing method were used. The mechanical (dry density, compressive strength, ultrasonic pulse velocity, and fracture energy), durability (shrinkage/expansion and mass change in water curing condition, water absorption/sorptivity and rapid chloride permeability) and microstructural (SEM/EDS analyses) characteristics of six AAMs were investigated. The 28-day compressive strengths of AAMs ranged from 29MPa to 49MPa with 100%GGBFS showing the highest value. Incorporation of VA/VP produced lower compressive strength, UPV, fracture energy and shrinkage characteristics but higher sorptivity and chloride permeability compared to their GGBFS counterparts. This can be attributed to the lower activation potential of VA/VP producing less dense microstructure which is characterized by predominant formation of C-A-S-H and N-C-A-S-H binding phases in all AAMs. This study confirmed the viability of producing cement-free VA and VP based AAMs (ranging from normal weight to lightweight) having satisfactory mechanical and durability characteristics for construction applications.

Keywords: Alkali activated mortars; Volcanic materials; Industrial wastes; Powder form reagents; Strength; Fracture; Durability; Microstructure