Mechanical Properties and Microstructure of Environmentally Friendly Foam Concrete with Fly Ash Modified with Micro- and Nano-SiO2

Currently, foam concrete is a prevalent energy-efficient building material, which is applicable for multiple purposes in a wide variety of buildings and structures. Improving the environmental performance of foam concrete and reducing its production costs through the use of industrial waste is a relevant and promising area. The goal of this study is to create innovative foam concrete (FC) mixtures using industrial waste, focusing on their environmentally friendly and energy-efficient properties for structural and thermal insulation purposes. The production of FC involved industrial waste products like fly ash (FA) and microsilica (MS). Nanosilica (NS) was used as an additional modifying additive. The study experimentally investigated the impact of the proposed formulation and process solutions on FC’s density, compressive strength (CS), and thermal conductivity (TC). The most effective FC modification parameters were identified for FA, MS, and NS. The best combination of 15% FA, 6% MS, and 0.4% NS produces environmentally friendly FC with improved properties: a density of 1142 kg/m3 and a TC of 0.268 W/m×°C, which are 3.8% and 15.2% lower than the control composition, respectively, and a CS of 15.1 MPa, which is 46.6% higher than the control value. Scanning Electron Microscopy (SEM) analysis validates that incorporating pozzolanic additives FA, MS, and NS into the FC composition fosters the development of more robust interpore partitions. This is due to the generation of a significant quantity of supplementary calcium hydrosilicates and a more homogenous pore structure. The structural quality factor of FC with 15% FA, 6% MS, and 0.4% NS increases to 52.4%. The structural and thermal insulation of FCs developed in this study are environmentally friendly building materials with reduced environmental impact and improved performance properties.