Synthesis and characterization of lightweight foamed geopolymers from iron tailings for energy-efficient construction

Thermal insulation is a critical consideration in building design, as it enhances energy efficiency and contributes significantly to occupant comfort. An effective solution involves using materials that not only prevent/inhibit heat transfer and have sufficient mechanical strength but also have low energy consumption and sustainability. Among the emerging alternatives, foamed geopolymers have shown considerable promise for thermal insulation applications, generally exhibiting lower thermal conductivity coefficients compared to conventional insulating materials. This study addresses two main aspects: the incorporation of iron tailings into geopolymeric matrices by 10 and 20% of the weight and the preparation of foamed geopolymers utilizing three different foaming agents: aluminum powder, hydrogen peroxide, and sodium perborate. The iron tailings were used as a supplementary additive to partially replace metakaolin, with the aim of promoting sustainable resource utilization. To evaluate the performance and feasibility of these materials, a series of tests were conducted, including compressive strength analysis, thermal conductivity measurements, and mercury intrusion porosimetry. The results indicate that the formulations incorporating sodium perborate achieve the lowest thermal conductivity values, ranging from 0.211 to 0.110 W/m·K. However, these samples exhibit relatively low compressive strengths, between 1.5 and 5 MPa. Conversely, geopolymers foamed with aluminum powder demonstrate higher thermal conductivity values, 0.296 to 0.391 W/m·K, but with significantly improved compressive strengths, reaching up to 13 MPa. Porosity analysis reveals that samples with more heterogeneous pore structures tend to perform better in terms of thermal insulation. The addition of iron tailings improved some characteristics, such as compressive strength. • Integrating 20wt.% iron tailings improved mechanical properties in foamed geopolymers; • Foamed geopolymers with aluminum powder providing the best strength (up to 13 MPa); • NaBO 3 created higher porosity (46%) and reducing thermal conductivity (0.110 W/m.K); • Geopolymer with H 2 O 2 and 20wt.% iron tailings are the best formulation for insulation.