School of Civil and Environmental Engineering

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Browsing School of Civil and Environmental Engineering by Subject "4mineral aggregates"

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    Concrete Production and Quality Control in Building Construction Industry of Ethiopia
    (Addis Ababa University, 2005-11) Eshetu, Abebe; Dinku, Abebe(PhD)
    Concrete is a construction material produced from three main ingredients namely, cement, mineral aggregates and water. The production process goes through various phases. Batching, mixing, transporting, placing compacting, finishing and curing are the main ones. In order to get quality concrete product, which satisfies both the strength and durability requirement, great care has to be given for concreting work starting from ingredient selection. The ingredient selected has to fulfill the requirement stated on standards. Every production process should follow the proper scientific procedures to get the desired quality concrete products. For this, quality control plays a significant role. Quality control is all the measures that are taken during material selection, concrete production processes and on finished concrete products to ensure the compliance of works with the specification. Concrete as a major building material, which is useful for the construction of the structural part, and as a non-factory product, which is susceptible to variation, proper control is utmost important in ensuring the desired quality product. Therefore, concrete quality affects the overall quality of buildings to a higher extent. But in Ethiopia there hasn’t been any study made on this area yet. Considering this, investigations focusing on concrete production and its quality are undertaken in the year 2005 on forty three building construction projects found in various parts of Ethiopia namely, Addis Ababa, Nazreth Debrezeith, Jimma, Awassa and Bahirdar The research is carried out by collecting sample compressive strength test result data and information on qualities of concrete ingredients and methods of concrete production through questionnaire and site observation. The findings xii of the investigation have shown that in most of the projects sufficient tests are not conducted both for the coarse and fine aggregate. This indicates that a lot has to be done to improve concrete quality in the building construction industry. From the statistical analysis of test results, the computed standard deviation shows 51.23 % of the projects` quality control is not good from which 19.51% fall in the “fair” classification range and 31.72% in the “poor” range; and that of the coefficient of variation shows 53.67 % of the projects` quality control is not good from which 39.02% fall in the “fair” classification range and 14.65 % in the “poor” range as per the classification of ACI 214. This is an indication that the test results among a significant portion of the investigated projects have shown large variability implying the quality control is unsatisfactory on those projects. It is also observed that, more than half, 52.17% of the projects have got defective lots, which fail to satisfy the compliance requirement set on the Ethiopian building codes and standards. Key words:- Cement, mineral aggregates, water, bathing, mixing, transporting, placing, compacting, finishing, curing, quality control, standard deviation and coefficient of variation.