Innovative glass-ceramic foams prepared by alkali activation and reactive sintering of clay containing zeolite (zeolite-poor rock) and sawdust for thermal insulation

Abstract

Energy-saving through thermal insulation of the buildings is becoming extremely important recently, addressing sustainability-connected challenges. This work examines the potential for producing innovative glass-ceramic foams from zeolite-poor rock and sawdust using alkali activation and reactive sintering techniques. A comprehensive analysis has been conducted for the detailed characterization of raw materials as well as the produced samples. The starting raw materials and the produced samples were investigated based on their chemical constituents, particle size distribution, BET (Brunauer, Emmett and Teller), X-ray diffraction (XRD), X-ray fluorescence (XRF), energy-dispersive X-ray spectroscopy (EDS), thermogravimetric (TG), differential thermal analysis (DTA), scanning electron microscopy (SEM) and computed tomography (CT). The alkali activation and the mechanism of foaming were systematically discussed. The optimal sintering temperature and the maximum expansion percentage are evaluated using heating microscopy. The findings show that the used alkali-activated raw mixtures have excellent foamability at 850–950 °C. The influence of the sawdust content and sintering temperatures on different technical characteristics such as bulk density, volume expansion, compressive strength, thermal conductivity, morphologies, phase identification, and microstructural properties of the sintered samples were thoroughly examined. The SEM and CT analysis of the produced specimens reveals the formation of foams with different types of pore sizes and distribution. The produced glass-ceramic foams have compressive strengths ranging from 0.3 to 4.5 MPa and thermal conductivities ranging from 0.058 to 0.178 W/mK. Development of these value-added glass-ceramic foams utilizing easily obtainable, low price raw materials should result in economically cost-effective materials with extra environmental benefits.