Compressed stabilized earth blocks incorporating cement and waste cotton fiber: Mechanical, durability and life-cycle performance

Abstract

Earthen construction offers a low-energy, low-carbon alternative to conventional masonry, but the limited strength and moisture sensitivity of unfired earth restrict its structural use. This study evaluates waste cotton fiber, an abundant textile-industry by-product, combined with ordinary Portland cement in compressed stabilized earth blocks (CSEBs). A clayey sand (SC) was stabilized with 0, 6, and 8% cement and 0, 0.5, 1.0, and 1.5% cotton fiber by dry-soil mass, producing twelve mixtures. Mechanical performance was assessed through unconfined compression, split tensile, and flexural tests, while durability was evaluated by wet compressive strength, water absorption, submersion, and efflorescence. FE-SEM, TGA-DSC, and factorial ANOVA were used to examine microstructure, hydration-related behavior, and the effects of cement content, fiber content, and their interaction. The 28-day dry compressive strength of cement-stabilized mixtures ranged from 0.70 to 2.28 MPa, up to about seventeen times that of the unstabilized control, while split tensile and flexural strengths reached 0.60 and 3.10 MPa, respectively. Strength generally peaked at 1.0% fiber and declined at 1.5%, with C8Co1 providing the strongest combined mechanical performance among the tested mixtures. Mechanical and microstructural observations indicated complementary contributions of cementitious matrix bonding and cotton-fiber crack bridging. C8Co1 satisfied several regional earth-construction standards and showed approximately 90.4% lower cumulative energy demand and 66.6% lower GWP 100 than fired clay brick for the representative single-story dwelling. Lower-cement sensitivity scenarios provided further environmental reductions, while C8Co1 retained the strongest experimentally verified overall performance. The project-specific cost analysis indicated a superstructure saving of about 8.9%.