Engineering properties, sustainability performance and life cycle assessment of high strength self-compacting geopolymer concrete composites

Abstract

The present investigation aims to study the mechanical and durability performances of Fly Ash (FA), Ground Granulated Blast Furnace Slag (GGBS), and Metakaolin (MK) blended Self-compacting Geopolymer concrete (SCGC). The significance of the investigation is to study the application of SCGC composites over conventional cement concrete for infrastructure. Furthermore, this investigation was focused on developing guidelines for SCGC. FA-SCGC (100% FA), FG-SCGC (50% FA + 50% GGBS), and FM-SCGC (50% FA + 50% MK) were exposed to acid and salt solutions. Two sets of curing conditions were adopted in the present investigation, namely, ambient and oven curing. In the case of ambient curing condition, the specimens are left at room temperature for a period of 28-days. Whereas, in the case of oven curing, after the rest period of 24 h, the specimens are cured in the oven at a temperature of 60 ℃ for a period of 24 h, then followed by ambient condition curing for the rest 27-days. Two types of acid solutions were employed: Sulfuric acid (H2SO4) and Nitric acid (HNO3) with a concentration of 2%. Two salt solutions are employed: magnesium sulfate (MgSO4) and sodium chloride (NaCl), with a 3.5% concentration. The parameters such as the physical observation, mass loss, and strength loss of SCGC composites exposed to acid and salt solutions were evaluated after 28-, 56-, 90-, 120-, 180-, 270- and 360-d of exposure. The result of all the three mixes, FA-SCGC, FG-SCGC, and FM-SCGC, show a better performance against acid and salt solutions. In addition, FG-SCGC is stronger and more durable than FM-SCGC, and FA-SCGC mixes; this could be attributed to the highly stable and cross-linked alumina-silica structure. The FA-SCGC shows better durability resistance but possesses lower mechanical properties among all the three mixes; this might be attributed to the low reactivity of FA particles, lower oxide composition of calcium, and more porous structure. It is found that amongst all the exposure conditions, exposing to H2SO4 environment causes severe damage to the concrete mixes. Further, a life-cycle assessment (LCA) examines the energy requirement and greenhouse gas emission (GHG-e) of normal strength and HSGC with various precursor materials. The FA-blended SCGC accounts for the least energy requirement for its production, while FG-SCGC possesses a slightly higher energy requirement than the FM-blended SCGC. The comparison of SCGC with the conventional Portland cement concrete shows that the FA-SCGC and FG-SCGC mixes have lower GHG-e by about 9.45 % and 5.88 %, respectively.