Utilisation of treated rice straw waste fibre as reinforcement in gypsum–cement unfired clay bricks

The study inves t igates the properties of rice straw-reinforced gypsum–cement clay bricks. The NaOH-treated rice straw at constant proportion of 2% by weight of the binders was added to the mixture of clay soil, gypsum and cement. Linear shrinkage, density, initial rate of absorption, wet and dry compressive strength were the properties considered. Different characterisation analyses were conducted on the waste rice straw fibre-reinforced gypsum clay bricks. The results showed that lowest and highest shrinkage results were 25% less and 11.5% more than the reference. There is a corresponding connection between the density, linear shrinkage and initial rate of absorption of the clay bricks which were significantly influenced by the additives. Scanning electron microscope and Fourier transform infrared spectroscopy analyses established the dominant presence of calcium sulphate hydrate with increased peak intensities on introduction of rice straw to the mix. Prominent crystal phases of gypsum, kaolinite, quartz, calcium hydroxide and ettrengite were observed in the X-ray diffraction results. Thermogravimetric analysis and differential thermal analysis results indicated the dominance of singular massive endothermic peaks, thermal and gravimetric profiles denoted for calcium sulphate dehydrate decomposition at temperatures less than 500 °C. Brunauer–Emmett–Teller results revealed that the surface area, pore volume and pore diameter of rice straw fibre-reinforced clay bricks were higher than the non-reinforced clay bricks. The reinforcement of clay bricks with chemically treated rice straw and the other additives could help to produce an improved performance from clay bricks.