Since the publication of the Second Edition of this book in 1986, the need to carry out extensive repairs to reinforced concrete structures has continued. Most of these structures were originally expected to have a life span of 80– 100 years and this premature deterioration has caused serious concern. In this country considerable publicity has been given in the technical press to major repair work on road bridge structures, particularly on major trunk roads and motorways.
While structural design, including specification, varies to some extent from one country to another, the materials used—namely Portland cement, aggregates, steel reinforcement and mixing water—are essentially similar. The main cause underlying this deterioration is also basically similar, namely the corrosion of the steel reinforcement.The journal, Building and Civil Engineering-Research Focus, April 1995, p. 5, says: The corrosion of steel reinforcement is the most serious durability problem affecting concrete structures throughout the world…A possible alternative solution is the use of non-ferrous fibre reinforced plastics (FRP).
Repair methods show somewhat wider differences. For example, in the US and Canada, cathodic protection has been used for many years before it was given serious consideration in the UK. The removal of chlorides by electrochemical means has also been tried in the US, but with mixed success.In France, considerable use (appreciably more so than in the UK) is made of special elastomeric coatings to increase the durability of the repaired areas of concrete, and to reduce greatly the risk of corrosion of reinforcement in new construction.
These coatings are formulated to reduce water penetration into the concrete and comparatively little attention is given to the ability of the coating to prevent/reduce diffusion of carbon dioxide into the concrete. This book is intended to deal mainly with ‘non-structural’ repairs, that is, repairs which are intended to restore as far as practicable, long-term durability and ‘useful life’ of the structure or part of the structure. The expressions ‘long-term durability’ and ‘useful life’ are almost impossible to define in a clear-cut way, and therefore in Chapter 3 I have included some comments on this subject.
Non-structural repairs will not increase to any significant degree the load-bearing capacity of the structure. One of the first and most important steps in the investigation of a deteriorated structure is to decide whether structural strengthening is required and, if so, whether the result is likely to be cost-effective. I recommend that investigations of deteriorated reinforced concrete structures should be carried out by a chartered civil or structural Engineer, or other professional with considerable experience in this type of work
I have included in Chapter 1 certain aspects of the investigation and repair of structures which my experience suggests are relevant and important to those associated with this type of work. While mention is frequently made to the engineer, especially his or her duties and responsibilities, the term is intended to apply to architects, building engineers, contractors and others who have responsibilities for the repair and renovation of concrete structures.
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