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Here, we report a study of white-ochre powders with targeted composition MnWO4 prepared via a coprecipitation method. Through X-ray total scattering combined with pair distribution function analysi...

To future-proof alkali-activation technology, there is a need to look beyond well-established precursors such as fly ash and blast furnace slag, due to resource competition, geographical distribution and technical limitations. Clay minerals are abundant and diverse aluminosilicate resources available around the world. However, due to the mineralogical complexity amongst the most common 1:1 (kaolinite, halloysite) and 2:1 (montmorillonite, illite) clay minerals, and practical issues such as workability, their use has been more limited. Recent advances have improved understanding both of pre-activation treatments (thermal, mechanical, chemical), and of the factors influencing clay reactivity, phase assemblages and properties of final products. This opens new opportunities for the exploitation of these resources to produce sustainable cements. A one-size-fits-all approach for processing and activating clay minerals is not viable. Instead, activation routes need to be tailored according to the clay mineralogy to achieve the binder properties required for key applications. Published with golden open access ispartof: Cement And Concrete Research vol:132 status: published

Alkali-activated soils have potential as low carbon, low cost construction materials. There is a lack of fundamental understanding around how soil composition influences alkali activation behaviour, especially for uncalcined soils. The types and relative amounts of clay minerals can vary greatly throughout soils across the world. Since clays are typically the dominant reactive aluminosilicate constituent in soils, it is desirable to understand how the types and relative amounts of clay minerals influence reaction products in alkali activation. In this study, mixtures of kaolinite, montmorillonite and illite precursors were activated with sodium hydroxide solutions. By comparing with extrapolations of cross-characterisation from the behaviour of individual clays, it was shown that phase formation behaviour deviated from an ideal rule of mixtures model. Instead, there was a hierarchy between the clays in determining the reaction products: kaolinite and montmorillonite dominated illite in this regard. This study demonstrates that the viability of a given soil for alkali activation depends not only on the total amount of clay, but the types and relative amounts of clay minerals present. In order to unlock the potential of alkali-activated soils, more understanding is needed of the role of the different components in soil.

Alkali activation of clay minerals in soil can be used to form a stabilising phase, such as a geopolymer. Because this requires low-temperature curing, typically