Comprehensive Study of the Effect of Hematite-Rich Sludge from Water Treatment Station on the Physical Properties of Metakaolin-Based Geopolymer Cements

This work aimed to study the effect of WTHs (Water treatment hematite-rich sludge) additives on the properties of geopolymers cement. Three formulations of geopolymer cement based on metakaolin powder substituted with 0, 5 and 10 wt.% of WTHs were investigated and the obtained pastes were characterized after curing times varying from 7 to 28 days. X-ray diffraction (XRD) and FT-IR patterns of metakaolin and WTHs dry powders indicate that they were in the amorphous states with illite, lepidocrocite and quartz in low concentrations in metakaolin and mainly hematite in the sludge. The pastes demonstrated an accelerating effect of the WTHs. The specimens showed weak linear shrinkage that increased slightly with sludge additive (from 0.5% to 1.7%). Improved apparent density was obtained with increasing WTHs contents (1.83 to 1.97 g/cm3). The Porosity was improved for 5% WTHs (67% to 77%) with a slight drop for 10%. The optical microstructure exhibits pores interconnectivity with appearance of some macropores favoured by WTHs additives that promoted a three-dimensional porous structure. The products exhibited a compressive strength of 14 MPa on day 28 and could be used as structural and porous materials required for thermal and acoustic isolation.