UBFS-Based Fiber-Reinforced Geopolymer Concrete as Jacketing Material for Retrofitting

Abstract

Recently, a new sustainable binder named geopolymer has gained significant momentum due to its cost-effectiveness and environmental benefits. In the present paper, material characterization of fiber-reinforced geopolymer concrete (FRGC) has been investigated, and its application as a noble jacketing material has been investigated. Ultrafine ground granulated blast furnace slag (UBFS) blended with fly ash (FA) was used as the binding material, activated with sodium hydroxide (SH) and sodium silicate (SS) solutions. Several FRGC mixes were prepared, and the effects of molar concentration (M) of SH, volume of fine aggregate to total aggregate (s/a), and volume fraction (Vf) of steel fiber were studied both in fresh and hardened states. To evaluate the efficiency of the FRGC as jacketing material, a RC prismatic beam was initially tested until failure. The cracks in the damaged specimen were initially repaired using geopolymer mortar (GM) followed by FRGC jacket, and the strengthened specimen was retested after 7 days of curing. To validate the effectiveness of FRGC, specimens were also repaired with ordinary portland based cement (OPC-Cement) mortar (PCM) and fiber-reinforced cement concrete (FRCC), and their performance was compared with those jacketed by FRGC. Test results show that variation in the s/a ratio and molarity of SH significantly influences the thickness of the paste in FRGC mix, thereby controlling the bleeding and segregation. However, an optimum value of 0.41 (s/a) and molarity within 6 to 8 M leads to better packing and superior mechanical strength in FRGC. Steel fiber substantially affects the workability; however 1.3% Vf of steel fiber exhibits significant improvement in flexural property and postcracking behavior of the FRGC mix. The section enlargement with both FRCC and FRGC exhibits more than 100% strength enhancement. But FRGC jacket performs better than FRCC pertaining to higher strength enhancement ratio (SER) and crack-arresting features with no sign of debonding of the jacketing layer, indicating better monolithic action in comparison with the FRCC jacket.