Investigation of the ionic curing effect and performance of modified nano-montmorillonite on river sludge pastes: Influence of sludge substitution and MNMt dosage

The effect of replacing cementitious materials with different dosages of river sludge on the properties of the cement-slag binary-based geopolymer composites was investigated. The application of this research is the possibility of reusing river sludge into environment-friendly unburned bricks. The influence of nano-montmorillonite on the solidification of heavy metals in the matrix was also explored. Samples containing sludge were characterized by lower fluidity and compressive strength, but prolonged hardening time; at 60% replacement, the strength was equal to 8 MPa and the final setting time was 4.5 h. The sample including 0.4% NMt helps to improve strength thanks to its ability to partially fill the capillary pores and promote the degree of hydration. The pastes containing NMt have less dangerous heavy metals like Cu (II) and Cr (VI). The reaction products and the microstructure of the mixes with modified-NMt are exploited to understand the mechanisms at the basis of the findings.