Abstract : With increased competing demands of sustainable and green structures to support the United Nations sustainable development goals, new technologies are evolving for efficient design and manufacture and construction of civil and environmental engineering products. Researchers have up scaled their effort to develop techniques to monitor the performance of civil engineering structures within their service life for optimum return from investment. The aim of this research was to develop a corrosion model for prediction of the service life of reinforced concrete water conveyancing structures. To achieve the desired objective, steel samples were cast in 9 cylinders each of 150mm diameter x 300mm long, 130mm diameter x 300mm long and 100mm diameter x 300mm long in concrete of characteristic strength 25/mm2,30N/mm2 and 35N/mm2 respectively. After 24 hours the cast specimens were demolded and immersed in curing tanks for 28 days and then immersed in a 3.5% industrial sodium chloride solution under 6V. The accelerated corrosion specimens were monitored for onset of cracks and stopped when the cracks were 0.2mm in width. The physical and chemical properties of the materials were investigated for compliance with relevant and applicable British and Kenyan standards for conformity to acceptable criteria. The concrete materials were batched by weight and mixed by a lab electric pan concrete mixer in batches of 0.009 m3. The concrete batches were tested for consistency by the slump and compaction factor tests. The applicability of existing models for critical corrosion depth for cover cracking was assessed. The corrosion current density of existing models was evaluated using results of this work and a model was proposed that matched with the experimental data reasonably well. Further, a corrosion service life prediction model that takes account of the cover to the rebar, the compressive strength and split tensile properties of concrete has proposed. The service life model developed here is for reinforced concrete water conveyancing structures subjected to chloride contamination. The model defines a criterion for corrosion initiation period, crack propagation period to 0.05mm width and propagation period from 0.05mm to 0.2mm. The results of the analysis of the present model significantly correlate well with experimental work and results of other researchers
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Abstract : Corrosion of reinforced concrete water structures generates tensile stress within the concrete and reinforcement interface influencing the service life of structures. This research investigated the influence of selected commercially available corrosion inhibitors in Kenya in combination of selected brands of ordinary Portland cement on the bond behavior of reinforced concrete members. To achieve the desired objective, samples in concrete of characteristic strength of 25N/mm2, 9 cylinders each of 150mm diameter x 300mm long each for four corrosion inhibitors and one control experiment were cast with an embedded rebar of 10mm diameter and 110mm long. For each series 9 cubes of 150mm x 150mm and 9 cylinders of 150mm diameter x 300mm long were cast for compressive strength and split tensile strength test respectively. After 24 hours the cast specimens were demolded and immersed in curing tanks for 27 days and tested for bond strength. The physical and chemical properties of the materials were investigated for compliance to relevant applicable British and Kenyan standards for conformity to acceptable criteria. The concrete materials were batched by weight and mixed by a lab electric pan concrete mixer in batches of 0.009 m3. The concrete batches were tested for consistency by the slump and compaction factor tests. The result show that bond strength increased with all selected corrosion inhibitors in combination with each respective cement brand. A bond strength model that correlated significantly with Orangun et al and Stanish et al model has been proposed
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