Magnesium Sulfate Resistance of Strain-Hardening Fiber Reinforced Slag and Fly Ash-Based Engineered Geopolymer Composites.

In this paper, the mechanical properties and durability performance of polyvinyl alcohol fibers reinforced lightweight engineered geopolymer composites (EGC) with different fly ash and slag contents exposed to 5% magnesium sulfate solution for up to 120 days were investigated. The results were also compared to lightweight engineered cementitious composites (ECC). Instead of silica sand, recycled glass was employed as a lightweight aggregate to reduce the density of EGC and ECC composites. A combination of NaOH and water glass (Na2SiO3) solutions with a Na2SiO3/NaOH ratio 2.5 was chosen to produce lightweight EGC specimens. The relative slump, density, ultrasonic pulse velocity, visual inspection, weight change, compressive stress–strain diagram, load–deflection responses, and scanning electron microscopy were examined to investigate the normal and sulfate environments of EGC and ECC specimens. The obtained results confirmed that the EGC composites had significant multiple-cracking characteristics, strain-hardening behavior, and high deformation capacity after 120 days of exposure to sulfate environments. Moreover, the results showed that the EGC specimens had higher residual compressive and flexural strengths in normal and sulfate environments than ECC specimens. Including 50% slag and 50% fly ash into the EGC mixture exhibited the optimal deflection capacity; however, the deflection of EGC specimens substantially reduced from 6.97 to 2.52 mm when the slag amount increased from 50 to 100%. Despite all studied samples preserving their multiple-cracking and tight crack width control and deflection-hardening behavior when exposed to sulfate environments for up to 120 days, the reduction in deflection capacity of EGC specimens ranged from 8 to 22%. [ABSTRACT FROM AUTHOR]