ABSTRACT
SouthAfrica currently produces some thirty million cubic meters of concrete and mortar each year making it probably the most widely used construction material locally and world wide when considering both volume and diversity. (Addis. 1998) The vast majority of concrete structures have performed satisfactorily for many years and concrete was until recently seen as a maintenance free building material. This perception together with the expectation that university buildings should last for hundreds of years resulted in the decision to use off-shutter concrete as the principle building material and finish for the buildings of the University of Johannesburg. (Kruger & Pretorius. 1996)
Terms such as concrete durability, concrete carbonation, acid rain and related concrete construction problems were unknown when the construction of the University was in full swing during the early 1970’s. At the time of construction, the campus was a dream project for any consultant or contractor. The capital worth, in terms of today’s values, was in the order of one billion Rand. Design and construction of the project was completed over a period of five years using novel rapid construction techniques, which
tions. Time constraints, under which the project was planned, designed and constructed, resulted in very little attention being given to aspects such as ensuring durable concrete and adequate cover over reinforcing steel. Environmental attack is currently receiving a lot of attention as it is substantially reducing the lives of many concrete structures around the world as is the case with the buildings of the University of Johannesburg. (Kruger & Pretorius. 1996)
Over the following twenty-five year period, the inadequate concrete cover has exposed itself through cracking, the leaching of corrosion products and spalling. As the exposed concrete was considered to be maintenance free, very little time and money were spend on the maintenance of the external facade of the building during these years. Ongoing evaluation and diagnostic studies undertaken on the University buildings indicated that carbonation of concrete and inadequate cover of the reinforcement steel could be identified as the main causes of the concrete degradation and reinforcing steel corrosion, taking place on the campus buildings. Spalling of concrete on high locations and the aesthetically unacceptable appearance of cracks and leaching gave rise to concern.
