Concrete structures, in particular reinforced concrete structures, have been designed and built for many years. Many previously built structures are now being compromised with regard to their condition and structural integrity. There has developed a need to maintain these structures and protect them in order to protect the users and minimise the expenses associated with repair and maintenance. Instead of resorting to demolishing and rebuilding, engineers are becoming increasingly capable of restoring and enhancing existing structures in order to maximise the original structures lifespan. One of the ways in which this is achieved is through the implementation of various repair and maintenance strategies. These strategies can range from cathodic protection of the steel reinforcement to increasing concrete cover of the section. The easiest and often most commonly used method, although often not effective when used on its own, is to coat the concrete surface with a protective coating. There are many coatings available, ranging from simple to complex formulations of inorganic and organic materials. These coatings each perform a unique function and will often be designed to combat a specific problem with which the structure is to be exposed. The formulation of the coatings are almost always designed correctly when they are manufactured, however, premature bond failure due to poor substrate surface preparation and various substrate moisture conditions still seem to occur after coating application. This investigation will give insight into the effects a sound, clean and profiled concrete substrate that is subjected to different moisture conditions will have on the bond strength achieved when using cementitious based coatings. The reason for differing the moisture conditions of the substrate is that often on site the moisture condition of an existing substrate is not known prior to application of the coating. This investigation shows that epoxy modified cementitious coatings provide acceptable bond strength. In some cases, failure within the coating instead of the acceptable failure within the substrate has resulted, due only to the level of dryness of the substrate. A thorough investigation on the theory behind surface coatings, their properties and performance requirements was done and subsequently followed by a detailed experimental programme that was performed and analysed to provide insight to the said coating behaviour. Inorganic coatings behave more predictably when applied to moist substrates as this is the ideal condition for the coating to adequately hydrate. In almost all the specimens with fully dried substrates, the resulting bond strength of the coating was less than that observed with the saturated surface dry substrate condition. It is therefore advised that the moisture condition stated by the coating manufacturer be adhered to as this will give acceptable results with failure taking place within the concrete substrate and not within the coating as a failure of the latter is completely unacceptable when referenced to the European and American set of standards. The European standard BS EN 1504: Products and systems for the protection and repair of concrete structures provide a more complete and reliable framework for the concrete repair industry and hence is preferred over any South African national standard currently available. Further research into the viability of a South African based standard will need to be investigated before being considered for use in this research paper.

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