Preparation and properties of alkali-activated fly ash-waste brick porous building materials

Abstract

This study explores the development of sustainable porous building materials through the alkali-activation of fly ash and waste clay brick powder. Utilizing Class F fly ash and brick powder from demolished buildings, a series of alkali-activated mortars with varying brick powder replacements (0 % to 50 % by mass) were formulated and analyzed. The results reveal that a 10 % brick powder replacement optimizes the compressive strength, reaching 73 MPa at 28 days, attributed to enhanced nucleation and calcium-rich gel formation. However, higher brick content reduces strength due to the dilution of key reactive materials, with a 50 % replacement leading to a strength of 27 MPa. Porosity increases proportionally with brick content, achieving a maximum of 42 % at 50 % replacement, suggesting potential applications in insulation-centric scenarios. Microstructural analysis confirms the formation of a porous network and identifies the phase compositions and reaction products. This research demonstrates the potential of repurposing construction waste into efficient and environmentally friendly building materials, contributing to waste reduction and offering a greener alternative to traditional practices.

Keywords

• Sustainable construction
• Waste repurposing
• Alkali-activated binders
• Compressive strength
• Microstructural analysis