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Diagnosis, Inspection,
Testing and Repair of

RC Structures

6.1 Introduction

Anyone involved in the maintenance of reinforced concrete structures cannot be unaware
of the substantial increase in the amount of repair work now being carried out. This may
merely reflect the fact that a large number of reinforced concrete structures are now
coming of age although certain changes in materials have been identified over the past
twenty years or so which might be partially responsible in some cases.

For example, in the early 1970s it was believed that there were no deposits of alkali-
reactive aggregates in the UK and yet within a few years alkali aggregate reaction became
a subject of major interest as more and more cases came to light. This upsurge in ASR
problems may be partially traceable to an increase in cement alkali content in the preceding
years. Furthermore, increases in the early age strength of cement may have meant that
specified minimum strengths were being achieved with less cement than had previously
been used with an appropriate effect on subsequent durability.

In the light of such phenomena it is clear that concrete must be regarded as a complex

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