Potential of waste rice husk ash and cement in making compressed stabilized earth blocks: Strength, durability and life cycle assessment

Abstract

Compressed stabilized earth block (CSEB) is an environmentally safe building material that is required as a sustainable alternative to traditional building materials. This research aims to investigate the suitability of rice husk ash (RHA) and cement for producing sustainable CSEB. RHA is a readily available waste product in rice-producing countries and using this waste product as a partial replacement for cement in CSEB has both environmental and economic benefits. To discern the ideal combination of stabilizers, three cement contents (4%, 6%, and 8% by wt. of dry soil), and five RHA contents (0%, 5%, 10%, 15%, and 20% by wt. of dry soil) are considered. The performance of CSEB is assessed regarding strength and durability. Strength characteristics were assessed by performing unconfined compression, split tensile, and flexure tests, and durability characteristics were assessed through water absorption, wet compressive strength, submersion, and efflorescence tests. There is an improvement of 224–1515% in dry compressive strength, 63–1190% in split tensile strength, and 112–732% in flexural bending strength (compared to unstabilized specimens) due to the addition of stabilizers. Considering strength properties, the optimum RHA content was 5% for 4% cement content, whereas for 6% and 8% cement content, it was found to be 10%. Considering durability, stabilized samples showed a reduction in water absorption of 2.8–73.4% compared to unstabilized samples. The strength and durability requirements provided in various codes have been met by the combination of 4–8% cement and 5–10% RHA. CSEB incorporating lower cement content with 5–10% RHA was found to perform better than that produced using higher cement content which indicates the suitability of RHA as a partial cement replacement. Furthermore, microstructural and thermal analysis has been performed on CSEBs fabricated with RHA, and the results revealed the existence of a higher concentration of C–S–H gel in CSEB stabilized with 8% cement and 10% RHA. Life cycle analysis conducted on a one-story house showed that CSEB is superior to fired clay bricks considering environmental and economic aspects. Based on the outcome, it is evident that CSEB stabilized with RHA, and cement could serve as a sustainable building material.