Quality control of concrete constructions in Tanzania

Quality control is a process that is aimed at ensuring conformity with the design requirements and where it deviate significantly from this the taking of corrective action. In this dissertation an attempt has been made to assess the extent of quality control of in situ reinforced concrete(r.c,) construction vis-a-vis stipulations in specifications. The survey was preceded by a questionnaire addressed. to a sample of the main parties involved in various construction projects. Their experiences were then subjected to a Chi-square (Significance) test. The analysis indicates that the basic quality aspects are not jointly controlled to the extent that a specified end product may not be assured. The quality of the basic r.c. inputs were analyzed prior to an assessment of their performance at site, For cement and steel, it has been possible to trace quality control procedures for the production processes right at the respective factories. As strength is a safety related parameter, both plants have shown in -adequate process capabilities. Especially so is for the cement plant where a one day strength prediction criteria. governed by instinct could, not be justified. A some-what stricter criteria developed by utilizing techniques of linear regression analysis has been recommended. Model charts based on the Shewhart control charts have been developed for the processes. Literature survey based on Tanzanian contributors suggest adoption of the Latest foreign standard for structural use of concrete subject to some modifications to suit local conditions. Various site concretes were thus analyzed to reveal how they would stand against the basic requirement of BS.8110:1985. The results indicate that almost all concretes fail to comply with strength requirements of the standard. A proposal for extensive structural evaluation of structures already in place is suggested.