The repair and maintenance of ageing reinforced concrete (RC) structures has become increasingly costly, especially in the Cape Peninsula. Protection and maintenance of these reinforced concrete structures against concrete deterioration and rebar corrosion have become far more important for road authorities and asset managers. City Engineers are responsible for the repair and rehabilitation of RC structures in different exposure conditions, by identifying the type of deterioration and then employing the correct concrete repair solutions or corrosion resistance measures. This dissertation investigates the environmental exposure conditions in the Cape Peninsula that result in chloride-induced and carbonation-induced corrosion of reinforced concrete structures in the region. It includes a literature review on concrete deterioration mechanisms and the role of aggressive elements in rebar corrosion. The literature review also considered alternative corrosion-resistant rebar. There are a number of available alternatives, which include Fiber Reinforced Polymer (FRP), Hot Dip Galvanized (HDG) steel, and Stainless Steel rebar. Each alternative has advantages and disadvantages depending on design applications and durability requirements. The use of corrosion-resistant rebar would increase the structure's longevity, thus providing long-term cost saving for road authorities. In the City of Cape Town, city engineers have standardised the use of HDG rebar for repair solutions and new concrete structures. HDG improves corrosion resistance, thus making it desirable to road authorities. The HDG process has been developed in the construction industry with low production time and cost, proving favourable factors for engineers. In addition, engineers have to improve concrete quality and construction methods to protect the underlying rebar from corrosion. On a technical level, HDG rebar use in RC structures has benefits which outweigh their cost implications. The exclusive use of HDG rebar without sound engineering judgment based on factors such as the location of the structure, distance from the coast, the structural loading conditions, and construction methods and quality standards, might not ensure better concrete durability and structural longevity. Generally, correct structural rebar design and concrete quality can eliminate the need for the use of corrosion protection methods and materials. The use of HDG is a very attractive solution for structures within 5km from the coast; otherwise, normal steel is suited for most applications. Reinforced concrete members such as concrete bollards, bridge handrails and balustrades can be treated as consumables and can be replaced once steel corrosion or concrete deterioration has occurred and becomes unsightly, which would be about 20 years. This approach would be economically advantageous and politically favourable to the road authority as it creates skills and jobs by reducing initial internal and contractual costs. To illustrate the common forms of rebar deterioration in the Cape Peninsula region, this dissertation has included five repair and rehabilitation projects completed by the City of Cape Town's Road Authority. These rehabilitation projects have been identified for concrete repair and rehabilitation works, and some of these structures have recently undergone extensive concrete rehabilitation. City engineers are faced with many challenges that hinder service delivery, engineering processes and effectiveness. Among these are lack of staff with experience in concrete repair and asset management, and the lack of proactive maintenance tools. The lack of an adequate Bridge Management System (BMS) contributes to the inefficient allocation of resources for rehabilitation and repair projects. The Supply Chain Management System also delays the appointment of appropriate contractors due to unwieldy management systems and bureaucracy. These systemic problems are discussed to provide a better understanding of the current selection of concrete repair systems.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uct/oai:localhost:11427/27878 |
| Date | January 2018 |
| Creators | Abed, Gesant |
| Contributors | Alexander, Mark Gavin |
| Publisher | University of Cape Town, Faculty of Engineering and the Built Environment, Concrete Materials and Structural Integrity Research Unit (CoMSIRU) |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Master Thesis, Masters, MEng |
| Format | application/pdf |
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