A Study of No-Fines Alkali-Activated Concrete Using Binary Blends of Industrial Wastes

Abstract

The present investigation focuses on alkali-activated concrete (AAC) without fines as a sustainable substitute for pervious (permeable) concrete made of ordinary Portland cement (OPC). Fly ash and slag, which are industrial waste materials, were utilised as precursors and activated using sodium hydroxide (NaOH) and sodium silicate (Na 2 SiO 3 ). To maximise strength and permeability, activator-to-source material ratios (ASR: 0.3, 0.4, 0.5), aggregate content (70–80%), and NaOH concentrations (12M and 14M) were undertaken. Under ambient curing conditions, a maximum compressive strength of 17.4 MPa was attained at 14M NaOH and ASR 0.4. Lower NaOH concentrations (12M), however, preserved permeability but decreased strength (16.1 MPa). The porosity improved with increasing the aggregate content, while the strength dropped. By substituting the OPC while preserving durability and drainage efficiency, the study shows that optimised no-fines AAC can be a practical low-carbon, high-permeability material for stormwater management and environmentally friendly construction. Removing sand and substituting alkali activators for OPC promotes sustainability by producing long-lasting concrete, while reducing urban waterlogging.