Study Physicochemical and Thermal Properties of Eco-friendly Lightweight Geopolymers Incorporating Silica Sand Flour

Low-cost lightweight geopolymer mortars based on water-cooled slag, fly ash, and silica sand flour were prepared as a structural and thermally insulating material. The effect of chemical foaming agents such as hydrogen peroxide (H2O2) and sodium perborate tetrahydrate (NaBO3·4H2O) on thermal conductivity, bulk density, water absorption, porosity, and compressive strength was studied. FTIR, XRD, XRF, and SEM were used to investigate the raw materials and selected samples of prepared lightweight geopolymers. The prepared lightweight geopolymers were given a compressive strength of 1.05 to 17 MPa. The compressive strength, bulk density, and thermal conductivity values decrease with increasing foaming agent content due to the decomposition of its chemical structure and releasing of oxygen bubbles. The results show that hydrogen peroxide mixes have better performance in the physio-chemical and thermal properties than sodium perborate mixes to achieve low thermal conductivity (0.21–0.24 W/mK) with compressive strength values (1.18–3.45 MPa) for MS-H1 and MS-H2 mixes, respectively. According to the results of bulk density (454–800 kg/m3), MS-H1, MS-H2, MS-B3, and MS-B4 mixes can be considered ultra-lightweight. Using silica sand flour in powder form improves the physicochemical and thermal properties of the lightweight geopolymer and decreases the production cost of the lightweight geopolymers.