Utilization of Waste Silicone Sealant and Aluminium Scraps as Additives in Fly Ash–Based Geopolymer for Lightweight Construction Blocks
Year: 2026
Type: article
Abstract: This study presents a pathway for using waste silicone sealant (Si-s) and aluminium scraps (Al-s) to produce lightweight geopolymer materials. Fly ash, sodium hydroxide, and sodium silicate were used as the starting materials for geopolymerization. Ground Si-s and Al-s were added to the mixtures, which were then cured for 28 days under ambient conditions (25°C). The structural composition and morphology were analyzed using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM–EDS). The results showed that Si-s acted as a dispersed additive in the geopolymer matrix and affected the reaction, possibly because its acidity neutralized the alkaline solution. It also increased the crystallite size to 51.68 nm, compared with 20.25 nm for the control geopolymer. The addition of Al-s produced a porous structure and reduced the crystallite size to 14.94 nm because it reacted with the alkaline solution, generating an exothermic reaction and hydrogen gas. The physical and mechanical properties, including density, apparent porosity, water absorption, compressive strength, and ultrasonic pulse velocity, were evaluated. The proportions of Al-s and Si-s were expressed as parts per hundred mixtures (phm), with the mixture comprising fly ash, NaOH, and Na₂SiO₃ used in the geopolymerization process. The addition of 0.4–0.6 phm Al-s and 40 phm Si-s resulted in geopolymers with densities of 1,292–1,438 kg/m³, apparent porosities of 18.18%–25.87%, and water absorption values of 6.97%–10.15%. The compressive strength ranged from 13.25 to 41.91 ksc, depending on the Si-s content. These geopolymers exhibited physical properties and compressive strengths that complied with the requirements for Type C12 lightweight concrete blocks specified in Thai Industrial Standard TIS 2601-2556. Therefore, waste Si-s and Al-s can be effectively recycled to produce lightweight geopolymer materials with properties suitable for construction applications.
Language: English
Subfield: Civil and Structural Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: diamond
OpenAlex ID: W7213634975