Performance of mechanochemically activated supplementary cementitious materials in cement pastes and mortars

Abstract Mechanochemical activation (MCA) is a rapidly emerging technology for producing supplementary cementitious materials (SCMs). However, performance data on MCA SCMs is lacking. Here, we investigated the potential use of four low-grade materials as sources of alternative SCMs following MCA treatment. The studied materials were municipal solid waste incineration bottom ash (BA), basaltic fines (BF), low-grade clay (CL), and dredged sediments (DS). MCA increased the amorphous content (44% on average) and reactivity (830% average) of all materials, as indicated by quantitative X-ray diffraction and modified R 3 test results. All materials, except for DS, were transformed into reactive SCMs after MCA. The BET specific surface area increased significantly for BA, BF, and DS, but decreased by 64% for CL. Generally, MCA increased the 168-h heat release of the blended cement pastes (15% on average), while no systematic effect on the heat flow was detected. The increase in SCM reactivity was also evidenced by reductions in calcium hydroxide content of cement pastes incorporating MCA materials compared to untreated materials (40% average at 28 days). Slump flow values increased for all materials, except for BF, for which a minor decrease was detected. The compressive strength and bulk resistivity of mortar samples showed that MCA had beneficial effects, especially at later ages (~ 42–45% average increases at all ages). These results suggest that compressive strength, bulk resistivity, and slump flow in mortars can be simultaneously enhanced through MCA. This is especially valuable considering that the materials studied are all considered low-grade or landfillable by-products.