EXPERIMENTAL INVESTIGATION ON THE ELEVATED TEMPERATURE RESISTANCE OF CONCRETE CONTAINING WHEAT STRAW ASH AS A PARTIAL REPLACEMENT FOR CEMENT

Abstract

Concrete is a widely used construction material due to its durability, strength, and fire resistance. However, the concrete may decompose at the elevated temperature. Due to this there is a change in its properties, such as thermal, mechanical, and deformation. This study was investigating the impact of wheat straw ash on concrete's mechanical and microstructure properties under elevated temperatures. To achieve the goal of this research concrete produced by using wheat straw ash at a percentage replacement of 0%, 7.5%, 10%, 12.5%, and 15% by weight of cement was tested for its mechanical and durability properties by exposing it to elevated temperature. The test was conducted at the curing ages of 7th, 14th, 28th and 56th days. The compressive, split tensile and flexural tests were conducted by using ASTM C-39, C-496 and C-78 standards respectively and under durability tests water absorption and density of concrete conducted by using ASTM C-128 and ASTM C-138 standards respectively. The microstructures tests such as XRD and SEM, were be determined 56 days after being exposed to under controlled temperatures of 400ºC, 600ºC and 800ºC for 2 hours. The results of this study shows that, the strength of concrete increase with increasing amounts of wheat straw ash those containing up to 10% of wheat straw ash, when compared with the control but it decreases for the specimens those have percentage of replacement beyond 10% of wheat straw ash at the ages 28 and 56 days. The result of water absorption of concrete increasing, when the replacement of wheat straw increases due to high absorbative characteristics of ash and the presence of temperature. Microstructural tests such as X-ray diffraction and Scanning Electron microscopy analysis showed increments performance compare to the control mix for replacement of wheat straw ash up to 10%. The concrete exposed elevated temperature at 600ºC and 800ºC cracks and color changes pronounced on the surface of concrete. Therefore, the optimum amount of replacement is 10% wheat straw ash which gives comparable properties to the control mix and 10% wheat straw ash as a partial replacement for cement in concrete mixtures can enhance strength and durability. This makes it an excellent choice for construction in hot climates and also for chimney structures, where thermal performance is critical.