Bacterially Stabilized Desert-Sand Bricks: Sustainable Building Material

Abstract

This paper presents the results of an experimental investigation carried out to determine the consolidating effect of ureolytic and nonureolytic Bacillus sp. on desert sand. Bacteria-infused desert-sand bricks were prepared using various binders (cement, lime, fly ash), and their engineering properties were evaluated. The results showed an increase of ~19% in compressive strength and water absorption value of 17% in bacteria treated desert sand-cement bricks relative to the same properties in control. In treated bricks field emission scanning electron microscopy (FESEM) analysis revealed thick biodepositions at points of particle to particle contact of desert sand, creating a densified microstructure compared to untreated bricks. X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) analysis of bacteria-treated desert sand–cement bricks indicated the enhanced formation of other hydration products in addition to calcite, and thermogravimetric (TG) analysis validated the formation of additional C─ S─ H (approximately 12%) and calcium hydroxide (approximately 40%). This study shows that nonureolytic bacteria–infused desert sand–cement bricks can achieve an unfired compressive strength ≥ 5 MPa and, therefore, may serve as a sustainable alternative to other conventionally available bricks.