CASE STUDY ON THE ASSESSMENT OF SELECTED REINFORCED CONCRETE STRUCTURE AGAINST CORROSION IN ADDIS ABABA
Creators: name: GETACHEW AKALU ESHETE
Publisher: name: National Academic Digital Repository of Ethiopia
Year: 2019
Subjects: Reinforced concrete structures, assessment, re-bar, corrosion, re-bar exposure, tensile test, flexural test and visual inspection

description: This study focuses on the effect of reinforcement corrosion on selected reinforced concrete structures in Addis Ababa. Corrosion of reinforcement has been established as the predominant factor causing widespread premature deterioration of concrete construction worldwide. The cause and effect of corrosion on reinforced concrete structure, the assessment techniques, and the repair mechanism of reinforced concrete structure, handling and storage of re-bar is covered. Ten reinforced concrete structures are studied. Visual inspection was made and from that the re-bar handling and storage, the concrete cover usage and exposure of re-bar and the rust stains on the structures are assessed. To evaluate the reduction in strength of the re-bars tension test was conducted on 6 groups of corroded and non-corroded re-bar of diameter 10mm and 12mm.The re-bar is collected from three study area and diameter is measured and average value was made for the groups of re-bar. The measurement shows a 0.27mm, 0.32mm and 0.31mm loss in diameter of corroded re-bar compared to non-corroded re-bar. The result shows that the yield strength and ultimate strength of corroded re-bar is less than that of non-corroded re-bar. The percentage reduction of yield strength is by 20.43%, 33.47% and 10.86%. The percentage reduction of ultimate tensile strength is by 14.34%, 33.66% and 10.46%. To study the behavior of corroded and non-corroded re-bar flexure test was conducted on 6 beams specimen of size 20cm*20*cm*75cm for both corroded and non-corroded re-bar. A diameter 12 re-bar was used for all specimens and the degree of corrosion (mass loss) of the 3 beams was 0.64%, 14.23% and 10.48%. From the flexural test the load deflection curve, the failure load and the maximum deflection was recorded. The beams which were casted using 14.23% and 10.48% corrosion degree had a failure load of 58kN and 60.82kN.The beam which was casted using a 0.64% corrosion degree had a failure load of 77.1kN. The controlled beams had a failure load of 91.7kN, 70.8kN and 81.3kN with an average failure load of 84.73kN.These shows that the degree of corrosion is inversely related to the carrying capacity of a beam and that a very low level of corrosion degree or the<br> acceptable rust doesn"t affect the strength of a member. In order to know the handling techniques in construction sites questionnaire was prepared and data was collected. From the data 83.6% of the respondents said the re-bars are stored in open area, 30.9% of the respondents said that the re-bar was stored up to 6 month, and 25.5% said more than 1 year. This shows that much carelessness is seen in public construction sites towards re-bar storage. Thirty five percent of the respondents said that the correctness of clear (concrete) cover used is checked by experience and observation. These kinds of checking results for re-bar exposure after concreting. It is mandatory from all construction party to give emphasis to prevent and control corrosion problem before, during and after construction of reinforced concrete structure and standard handling and storage of re-bar should be achieved by the contractor during the construction stage. The government should fulfill corrosion level indicator instrument which is electrochemical and NDT