A comprehensive analysis on optimization of Sewage sludge ash as a binding material for a sustainable construction practice: A state of the art review

Abstract

The cement consumption by the construction industry results in the emission of CO2 into the atmosphere, depletion of the natural resource material, and consuming a lot of energy during the manufacturing of cement. The modern era of construction practice reclining slowly towards sustainable construction methods to reduce the burden on the environment. It has become mandatory to synthesize eco-friendly binding material out of various agricultural, industrial, and domestic wastes. In this domain, sewage sludge ash has gained attention as a prominent raw material that can be replaced effectively to reduce the consumption of cement in construction practice. In this review, comprehensive studies were made to find out the various physical, chemical, and microstructural properties of Sewage sludge ash (SSA). The pre-treatment that had been given to as received SSA such drying, ball milling, sieving, and incineration. Ball milling between 60 and 120 min enhanced its physical and chemical properties. The specific surface area of the crystalline matter was reduced drastically by enhancing the amorphous content, incineration at a 700 °C will activate the material increase the reactivity reduced unburnt carbon material and heavy metals which will hinder the reaction. SEM images proved that SSA contributes to the gel formation at the later stages of the reaction making the matrix dense and compact. The review showed that the SSA can be effectively replaced with cement up to 20% with little processing, enhancing the mechanical properties similar to a conventional binder.