Enhanced thermal insulation behavior of metakaolin-based geopolymer reinforced by miscanthus fibers

Abstract

This study addresses the urgent demand for sustainable building materials, presenting a pioneering use of miscanthus fibers (MF) in metakaolin-based geopolymer paste for thermal insulation. Investigating metakaolin types, alkaline solutions, and curing methods, the study assesses workability, density, compressive strength, thermal properties, porosity, and microstructure. With 30 wt% MF, compressive strength reduces from 19.38 MPa to 6.43 MPa at 28 days, with porosity increasing from 37% to 52%. This heightened porosity, especially in pores >10 μm, lowers thermal conductivity, crucial for insulation. The geopolymer matrix without MF exhibits a thermal conductivity of 0.45 W.m⁻¹.K⁻¹, serving as a reference. A 50 wt% MF formulation achieves the lowest thermal conductivity (0.21 W.m⁻¹.K⁻¹) and 5 MPa compressive strength. Aligning with plastering, rendering, and masonry mortar standards, using Argical 1000 metakaolin enhances compressive strength by 57% compared to the reference sample made with Argicem metakaolin. Analytical Scanning Electron Microscopy reveals robust fiber-matrix adhesion, ensuring structural integrity.