Search

The need to mitigate the CO2 emissions deriving from the cement industry becomes imperative as the climate crisis advances. An effective strategy to achieve this is increasing the replacement level of cement clinkers by waste-derived supplementary cementitious materials (SCMs). In this study, the use of mechanochemically activated biomass ash for high-volume (up to 40%) substitution of cement is investigated. The effect of mineral carbonation treatment on the performance of the mechanochemically treated biomass ash as SCM was also examined. The results showed that the mechanochemically treated biomass ash was the most effective SCM, with the respective samples at 40% cement replacement reaching 63% of the strength at 28 days as compared to samples with 100% Portland cement, while only 17% of the strength was achieved in samples with 40% untreated biomass ash. As suggested by the isothermal calorimetry, XRD, FTIR, and TG analysis, the mechanochemical treatment enhanced the reactivity and the filler effect of the biomass ash, leading to improved mechanical performances of these mortars compared to those containing untreated biomass ash. Mineral carbonation reduced the reactivity of the mechanochemically treated biomass ash but still led to better strength performances in comparison to the untreated biomass ash. [ABSTRACT FROM AUTHOR]

Partially replacing cement clinkers with activated clays is one of the most promising routes to decarbonise the cement industry and tackle the climate change crisis. This study systematically investigated the impact of mechanochemical activation on the physicochemical properties of kaolinite, muscovite and montmorillonite clays, including particle size distributions, morphologies, bulk and surface chemical structures. The results suggest that mechanochemical activation treatment is particularly efficient for improving the pozzolanic activity of 2:1 clays (i.e. muscovite and montmorillonite), which are difficult to effectively activate through thermal treatments and therefore not previously been extensively used as supplementary cementitious materials (SCMs). In addition to dehydroxylation and amorphisation, mechanochemical milling also leads to surface aluminium enrichment and reduction in binding energies of both Si and Al elements, all contributing to the enhanced pozzolanic reactivity. The outcome from this study represents a step-change in scientific knowledge and extends frontiers of developing new SCMs from sustainable resources. [ABSTRACT FROM AUTHOR]