Wood biomass ash, municipal solid waste ash, and recycled concrete from construction demolition waste as supplementary cementitious materials in fine graded granular mixtures

The use of supplementary cementitious materials (SCMs) for substituting Portland cement is a pragmatic short-term solution to mitigate the CO2 emissions related to cement production. The present paper concerns the development of cement-reduced binders to be used as alternative stabilizing agents for layers in road pavements. Binary, ternary and quaternary cementitious pastes made of cement and local supplementary cementitious materials, namely biomass ash (BA) from woody biomass plants, municipal solid waste incineration (MSWI) ash and recycled concrete from construction demolition wastes (RC), were formulated. As a first step, the supplementary cementitious materials were characterized and tested for hydraulic or pozzolanic reactivity to ascertain their potential as binders. Subsequently, the hydration mechanism of novel formulated mixtures made of Portland cement and supplementary cementitious materials were investigated. The R3 (rapid, relevant and reliable) heat release test, demonstrated that both BA and MSWI are significantly reactive; nevertheless, MSWI exhibited a slower reaction rate, likely related to the presence of organic matter. On the other hand, the RC is largely inert. Cement hydration tests confirmed a high degree of reactivity and a significant increase in cement hydration products in binary blends containing BA and MSWI, whereas the cement mixtures containing RC were confirmed to have low reactivity. Binary mixtures containing BA or MSWI, which were found to be the more reactive, were added to a sandy fine graded granular mixture to evaluate their binding potential through unconfined compression tests. Results confirmed the cementitious properties of the tested binders, notably in the BA-stabilized mixture.