Development of bio-based blended ash and fly ash-based alkali-activated concrete

Owing to rapid industrialisation and urbanisation there has been a significant increase in the manufacture and application of cement, resulting in high carbon dioxide (CO2) emissions into the atmosphere. This paper investigates alternative binders that have reduced carbon dixoide emissions and better performance. The study elaborates the mix design of novel concrete, wherein the principle raw material used was locally available bio-based blended ash (BA) procured from the co-combustion process with sodium-based alkali activators. The physical, chemical, mineral and morphological characteristics of BA were studied. Beside this, the influence of parameters such as molarity of sodium hydroxide (NaOH), liquid sodium silicate (LSS) to NaOH ratio, fly ash (FA) to BA ratio and method of curing on the physico-mechanical properties of alkali-activated concrete as a sustainable construction material were studied. Higher characteristic strength was attained with an increase in these parameters. A maximum characteristic strength of 42.31 MPa at day 28 was obtained with 8 M NaOH, LSS/NaOH ratio of 1.5 and FA/BA ratio of 3. The average flexural and split tensile strength obtained were 3.70 and 2.72 MPa, respectively. The experimental investigation of the alkali-activated concrete using BA and FA proved to be an efficient solution for zero-cement concrete with improved performance.