Formulation of geopolymer concrete using lightweight aggregate /

Abstract

Sustainable and greener production is the need of the hour due to abrupt demographic increase, depleting resources, ever increasing wastes and related environmental concerns. In this scenario, this study presents the formulation of cold bonded lightweight aggregates (LWA) based on industrial by products, which are coal fly ash (FA) and steel industry ground granulated blast furnace slag (GBFS). Two types of LWA were produced in this project; cement based aggregates (Cags) and geopolymer aggregates (GPags), and were studied under varied curing conditions to produce optimized strength aggregates. Different tests were performed on LWA to investigate their physical properties, mechanical performance and durability characteristics. In the second part, lightweight concrete (LWC) were also manufactured using selected types of aggregates from those produced already and examined to investigate their suitable applications as a structural LWC. Results showed that produced aggregates were lighter than many aggregates from earlier studies and they also satisfied the ASTM standard because their density ranged between 764-878 kg/m3. However, due to less density, they experienced comparatively higher water absorption value, but still they managed to comply with usual range for water absorption (<25%). Mechanical strength test results displayed that the strength of aggregates was improved with increasing binder percentage and Cags proved to be stronger than GPags. Alkali silica reaction test results indicated that the 28 days expansion of specimens was well within limits and none of the aggregates presented deleterious characteristics, whereas, overall expansion was lesser for samples containing LWA than NWA samples. Petrographic analysis under thin sections study, XRD and FTIR, further confirmed the non-reactive nature of produced LWA with the absence of alkali silica reactive minerals. Regarding LWC formulated, results showed that density of concretes (1906-1965 kg/m3) were within the limits of lightweight concrete; and also they presented water absorption values in the normal range for LWC (<10%). Compressive strength of geopolymer LWC produced was better than cement based concrete, and their values ranged between 17.43-29.66 MPa which confirmed their feasibility as structural LWC usage. Split tensile strength results were also in agreement to their compressive strength results and varied between 2.40-3.21 MPa. Concluding, results of this study confirm the successful production of LWA and their ability to manufacture LWC for more economical, technically sound, and environmental friendly concrete applications.