Investigation of Compressive Strength of Straw Reinforced Unfired Clay Bricks For Sustainable Building Construction

Abstract

Abstract The mud is considered as one of the oldest construction materials in Iraq and is still used in the country regions for farmer’s houses or animal shelters. In Iraq, there are different types of mud constructions, including adobe, unfired bricks and cob. The presented study has focused on unfired clay brick where the clay is the main material. To ensure that the clay is pure and clean, it was excavated from the depth of 2 m below the natural ground level. Different types of unfired clay bricks produced by adding different materials to the clay to improve its properties and especially large deformation due to shrinkage. The added materials are classified into three concepts, the first additives are the natural fibers (straw, sawdust, and rice husk) and they are used to improve the tensile strength of brick and reduce the cracking due to shrinkage. The second additives included added the fine and coarse sand as a stabilizer to reduce the volumetric changes. The third additives are adding cement to increase the adhesive and cohesion of the mud matrix. The measurements included compressive strength of brick, mortar, and masonry and the flexural strength of bricks alone. The behaviour of unfired masonry prisms was also compared to the traditionally fired clay brick prisms. The results indicate that higher compressive strength of bricks was got for the mix that included clay, coarse sand and straw. The maximum flexural strength of bricks was got for the mix that included clay and sawdust, while for unfired masonry prism the higher compressive strength was obtained with a mix that included clay, coarse sand and straw. Finally, a proposed formula to obtain the compressive strength of unfired brick masonry from the compressive strength of brick and mortar is presented.