Assessment of concrete production quality control in building construction sites: A case of Adama city

Abstract

Concrete is a major component of most of our infrastructural facilities today in the 21stcentury because of its versatility in use. Concrete is generally produced in batches at the site with the locally available materials of variable characteristics. Moreover, concrete undergoes a number of operations, such as transportation, placing, compacting and curing. During these operations considerable variations occur partly due to quality of plant available and partly due to differences in the efficiency of techniques used. Thus there are no unique attributes to define the quality of concrete entirely. Under such a situation concrete is generally referred to as being of good, fair or poor quality. The aim of this paper is to assess concrete production quality control in the building construction project sites of Adama city by identifying the factors affecting the quality of concrete production, by identifying the impacts caused by factors affecting the quality of concrete production, by assessing the current practices implemented on the quality of concrete production. Concrete quality control related literature was reviewed. A survey questionnaire supported by site observation was used to explore the local practice in concrete quality control and compressive strength tests results of concrete was also collected from consultant’s data files and analyzed with compliance of different scientific code and standards. A questionnaire was distributed to consultants and contractors sides’ professionals who are assigned to perform building construction sites of grade one general contractors. The researcher collected 20 lots of 7 th, 14th and 28th days concrete compressive test results in which the 7th and 14th days results are used by the researcher to assess the progress by evaluating the percentage values at those ages with respect to attainable scientific grounds. In fact, quality control is done for both OPC and PPC cements concrete at 28 days commonly. Additionally, each of the lots contains 3 pieces and a total of 60 pieces for each ages from 16 ongoing building projects in Adama city are collected from consultants whereas 8 lots with C-30 and 12 lots with C-25 compressive strength. To sum up, all lots are collected and assessed from ongoing concrete structural work of columns, beams, slabs and shear walls on the period of the researcher site observation while concrete casting. Each lot is examined according to Ethiopian building code and standard (EBCS-2:1995), and American concrete institute (ACI 318). Based on standard deviation 5% and based on coefficient of variation 15% of projects have poor concrete quality control. Though the research expelled that, variations and non-conformity to standards is available within the investigated project. This implies that the test results among the investigated projects have shown large variability indicating the quality control is unsatisfactory on those projects