A Statistical Evaluation On the Quality of Construction practice in Uganda
Kayongo, Umaru Sekalembe
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This research investigated statistically the quality of construction practice in Uganda. The specific objectives were to: investigate the quality of concrete used specifically looking at the standard deviation in the concrete strength as a parameter that would cause variations in the concrete quality; investigate the dimensional variations in the 4 building elements – investigate the poor quality of building elements and their effects on structural integrity. Concrete strength tests results were obtained from 3 labs; Makerere University Structures Lab, TecLab and GetLab, and a standard deviation obtained while assessing its effect on the concrete used. The 4 building elements dimensions data was obtained from the 20 sites in Kampala and Wakiso to check for compliance with tolerances provided by the 3 codes of practice. 375 concrete strength test samples from 2 concrete classes (C20/25, C25/30), from the 3 labs, each sample tested at 28 days according to BS EN 12390 in 2022. Statistical analysis for the strength tests was conducted to determine compliance with acceptance criteria of the quality indicators and the level of quality for each class separately obtained. Shewhart chart analyses were used to determine whether or not the process of concrete production was controlled. Building elements dimensions were subject to tolerances provided in various codes to ascertain conformance to limits. The statistical analysis data revealed that the degree of quality for the 2 classes varied from poor to good, unacceptable to acceptable and below standard as per the quality indicators. Shewhart charts indicated both classes were good; ACI indicated both classes were poor; US indicated both classes were below standard, and BS EN 2000 indicated C25 was unacceptable and C30 was acceptable. Based on definition of characteristics, not more than 5% of test results should not fall below the characteristic value, however, both classes had more than 5% strength values falling below the characteristic value; 12% for C25 and 9% for C30, which implied poor quality level for concrete strength. Hence, the degree of quality for the 2 classes was poor. The data revealed that, the greatest percentage of all the 4 building elements except stairs met the tolerance limits and were hence classified as ‘Pass’ as opposed to ‘Fail’ for the stairs. We recommend utmost attention be given to stairs during construction. The research findings would help to reduce claims, disputes, and wastes on site if quality work is executed. This research provides information on poor quality building projects and poor-quality concrete used and provides a systematic process for anticipating poor quality in building projects.