Mechanical performance of one part alkali activated concrete incorporating RMC wash water

This study investigates the development of one-part alkali-activated (OPAA) concrete using ready-mix concrete (RMC) wash water as a complete replacement for potable water. Fly ash (FA) and ground granulated blast furnace slag (GGBS) were used as primary binders, with the GGBS content fixed at 30%, while the solid activator dosage and water-to-binder (w/b) ratio were varied. The effects of wash water on fresh properties, mechanical performance, durability characteristics, and microstructure were evaluated. Microstructural and mineralogical analyses were conducted using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The OPAA concrete incorporating wash water achieved a maximum compressive strength of 50.67 MPa at 28 days with 14% solid activator and a w/b ratio of 0.32, exceeding the strength of the potable water counterpart of 48.89 MPa. The enhanced performance is attributed to the higher ionic content of wash water, which increased system alkalinity and promoted effective dissolution of aluminosilicate phases. Lower water absorption and sorptivity values indicated a denser microstructure, corroborated by the formation of well-developed C-A-S-H and N-A-S-H gels. Furthermore, OPAA concrete exhibited approximately 70% lower CO₂ emissions compared to conventional OPC concrete of the same strength grade, highlighting its potential as a sustainable construction material.