Application of activated river sediments and bentonite in Supplementary Cementitious Materials (SCMs): a review

Cement production accounts for approximately 7% of global CO2 emissions, creating urgent demand for sustainable supplementary cementitious materials (SCMs). This review systematically evaluates the physicochemical properties of river sediments and bentonite across diverse geological contexts, and comparatively analyzes three activation strategies – mechanical grinding, alkali activation, and thermal calcination – applied to both materials over the past decade. Quantitative meta-analysis of pozzolanic activity indices (PAI) identifies optimal processing parameters: grinding time 40–85 min, alkali equivalent 4.0–5.5% Na2O, and calcination temperature 750–850°C. Under these conditions, river sediments replacement up to 30% and bentonite up to 20% maintain cement-based material performance. Life-cycle assessment (LCA) data indicate CO2 reductions of 20–35% per cubic meter of concrete relative to ordinary Portland cement (OPC). Advanced characterization via Fourier transform infrared spectroscopy (FTIR) and 29Si/27 Al MAS NMR, cross-validation of machine learning predictions against laboratory durability data, and the limitations of current ternary system models are critically addressed. Molecular dynamics simulation is proposed as a priority for mechanistic validation. A unified theoretical framework and practical technology pathway are provided for the high-value, low-carbon utilization of river sediments and bentonite as SCMs.