Partial Replacement of Cement by Coffee Husk Ash for C-25 Concrete Production

Abstract

Concrete is mixture of aggregates and binders. From concrete ingredients the binder and the most costly and environmental unfriendly element is cement and it is one of the environmental unfriendly processes due to the release of CO2 gases to the atmosphere and environmental degradations Coffee husk is an agricultural by product of coffee bean, which is a result of dry process. Coffee husk usually considered as a type of agriculture waste; as its quantity rises, the treatment/disposal of it will become an environmental problem. In Ethiopia enormous amounts of coffee husk is generated annually from different coffee pulpler. Conversely, it have poorly been utilized or left to decomposed or otherwise dumped in the environment. As a result, this research was conducted to produce coffee husk ash concrete from coffee husk. Due to the booming of the construction activity in the country, there is high demand of cement. This research was therefore, amid to examine the potential of coffee husk ash as partial replacement for ordinary Portland cement (OPC) in C-25 concrete production with investigation of optimum ratio of replacement and engineering properties of C-25 concrete. Coffee husk samples were collected from different coffee treatment centres in Jimma Zone, Jimma City and it was carbonized at 550 oC temperature for 3 hours in an oxygendeficient environment and its chemical and physical properties were investigated. After that, the pastes containing OPC and coffee husk ash at 2, 3, 5, 10 and 15 % of replacement were investigated with zero percept of coffee husk ash as a control mix. Six different concrete mixes were prepared for 25MPa concrete with water to cement ratio of 0.5 and 360 kg/m3 cement content. The properties of these mixes have then been assessed both at the fresh and hardened state. The results of the concrete work have shown that, up to 10% replacement of the coffee husk ash achieved a higher compressive strength at all test ages i.e. 7, 14, and 28 days of age by compressive test machines. However, the results of the cube compressive strength and densities show that the compressive strength and density reduces as the percentage of coffee husk ash increases. It can therefore, be concluded that 10% replacement of cement by coffee husk ash results in a similar concrete properties with control test and it is the optimum replacement.