Early-Age Properties of Slag-Fly Ash Blended Geopolymer Concrete Reinforced with Glass Fibers – A Preliminary Study

– This research investigates the effect of additional water content, glass fibers addition, glass fiber length, and the handling time on the workability, 1-and 7-day compressive strength, and 7-day splitting tensile strength of slag-fly ash blended geopolymer concrete. The additional water content ranged from 0 to 100 kg/m³. Two types of glass fibers were used with lengths of 24 and 43 mm and incorporated by up to 2 and 1.5%, by volume, respectively. Also, the handling time, representing the time from mixing to casting, was varied. The experimental results showed that the additional water content led to a significant increase in the slump and decrease in the 1-and 7-day compressive strengths of plain geopolymer concrete. A value of 75 kg/m³ was required to attain a slump of 150 mm and 7-day compressive strength of 35 MPa. Furthermore, the addition of 24-mm long glass fibers reduced the slump and increased the compressive and splitting tensile strength by up to 23 and 40%, respectively, compared to the plain control mix. Longer glass fibers (43 mm) resulted in further slump loss and increase in the splitting tensile strength, while the compressive strength was unaffected. Extending the handling time led to lower workability and limited impact on the mechanical properties.