Agro-waste ash based alkali-activated binder: Cleaner production of zero cement concrete for construction

Alkali-activated binders are sustainable alternatives to carbon-intensive conventional cements. A comprehensive review of the potential of different agro-waste ashes and their performance as precursors in alkali-activated binders are essential to enable their acceptance in the construction sector. Hence, the present study focusses on a systematic review of the alkali-activation of bagasse ash, rice husk ash, corn cob ash, palm oil fuel ash, wheat straw ash, and sugarcane straw ash. Moreover, their influence on the mechanical and durability characteristics of alkali-activated concrete is also presented. Based on the review, it is found that except for rice husk ash, all the other agro-waste ashes have almost similar silica content as that of fly ash. The morphologies of the different agro-waste ashes are found to be distinct. Incorporation of agro-waste ashes in fly ash-based binders results in better resistance to acid attack than slag-based binders. Addition of agro-waste ashes brought down the drying shrinkage of slag-based binders significantly. Ambient curing is beneficial for bagasse ash-based alkali-activated mortar specimens. Water absorption is higher for agro-waste ash based alkali-activated binder specimens due to the porous cellular structure of agro-waste ashes. Enhanced performance at elevated temperatures is observed for agro-waste ash based alkali-activated binders. Rice husk ash-based binders are remarkably stable at elevated temperatures. [Display omitted] •Use of agro-waste ashes in alkali activated concrete is comprehensively reviewed.•Influence of six agro-industrial waste ashes on properties of concrete is discussed.•Effect of curing, type and molarity of alkaline activators on strength is presented.•Durability properties of agro-waste based alkali activated concrete are reported.•Current status of agro-waste ashes utilisation and further research are highlighted.