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.
