Effects of using sawdust as a partial replacement of fine aggregate for the production of hollow concrete block around jimma.

Abstract

Hollow concrete blocks are a construction material produced from a mixture of Portland cement (OPC or PPC), Fine aggregates and Water. But the concrete mixture used for blocks has a higher percentage of fine aggregate and a lower percentage of water than the concrete mixtures used for general construction purposes. The construction industry is rapidly growing industry in the world and hollow concrete blocks are being widely used in construction of residential buildings, factories and multi-storied buildings. Due to these there is a scarcity of good quality fine aggregate due to depletion of resources and restriction due to environmental consideration, to make a hollow concrete block manufacturing to look for suitable alternative fine aggregate. The objective of this experimental study was to investigate the effect of using sawdust as an alternative fine aggregate for hollow concrete block production and to determine an optimum content of sawdust for the replacement of fine aggregate that can be acceptable for the production of hollow concrete blocks, in order to help contribute to the industry in saving the environment, to provide new knowledge to the contractors and developers on how to improve the construction industry methods and services by using sawdust concrete mixture, and sustain good product performance. The study was a laboratory experimental study conducted by preparing two types of HCB test samples. The first test sample of HCB was produced by using mix proportion 1:2:1:2 of cement, sand, gravel 00 and crushed aggregate respectively as a control group. The second sample HCBs were produced by replacing sand with sawdust in 4% increment in volume 4%. 8%, 12%, 16%, 20%, and 24%. but the result between 8% and 12% replacement shows high difference therefore 10% replacement is needed to get the intermediate result. According to this study, the HCB without sawdust achieved 5.09Mpa mean compressive strength and the HCB with 10% sawdust achieved 4.01Mpa mean compressive strength and the HCB with 20% sawdust achieved 2.13Mpa. The acceptable replacement was obtained at 10% for the desired class B HCB and at 20% for class C HCB. The result from density and absorption show replacing sand with sawdust 4% in volume can decrease the density by 3.86% and increase the absorption by 2%. Material cost of all HCBs with sawdust was found lower than the HCB without sawdust. Replacing sand with sawdust 4% in volume can decrease the material cost by 3.68birr or 2%.According to the result hollow concrete block with sawdust replacement in this study has achieved a better reduction in material cost and density and a smaller increment in absorption also achieved the desired compressive strength by limiting the sawdust replacement percentage. Therefore as a recommendation for contractors, HCB manufacturer, Wood product manufacturing firm, construction industry and other researcher that the benefit of using sawdust as a replacement of fine aggregate has to be considered and deeply investigated.