Sustainable alkali activated concrete with fly ash and waste marble aggregates: Strength and Durability studies

Abstract

This study examines the use of waste marble aggregates (WMA) as a substitute to natural aggregates (NA) to produce sustainable alkali activated concrete (AAC). Sodium hydroxide (NaOH) of 8M concentration and sodium silicate (Na2SiO3) were used as an alkaline activator for high calcium fly ash based AAC. NA were replaced with WMA at different weight ratios, namely 0%, 25%, 50%, 75% and 100%. Different properties like density, workability, air content, compressive, flexural and tensile strengths, along with modulus of elasticity of fresh and hardened concrete were investigated. Also, rapid chloride penetration test, oxygen permeability index test, depth of water penetration, electrical resistivity and acid resistance were also conducted to study the durability characteristics of the sustainable AAC. Results of this study showed that WMA affected the pore structure and new calcium-based products were formed along with polymeric products. New products in the matrix accelerate the polymerisation process and significantly enhanced the strength properties and durability of AAC. The outcomes of this study revealed that WMA can be employed to replace up to 50% of NA in the production of sustainable AAC. Its high potential to replace NA could lead to significant saving in energy, cost and, can further reduce the hazardous environmental impacts caused by marble industries during mining, processing and polishing phases.