BRE DG455 PDF

Introduction

Well designed reinforced concrete structures have generally shown excellent durability. However, there are numerous examples of problems that have occurred due to the corrosion of the steel reinforcement in structures that are exposed to aggressive environments (such as motorway bridges, car parks and marine structures), and to poor design and workmanship. These structures have required premature and costly repair, remediation or even replacement.

The problems highlight the need for the service life – the period of time over which it is assumed that a structure will be used for its intended purpose – to be addressed at the design stage (see the box, ‘Definitions', on page 2). Designing the structure to meet its required service life allows an appropriate balance between initial and running costs to be established; it allows, also, the level and nature of repair and maintenance appropriate to the structure and the client's needs to be planned. Similarly service life concepts and techniques can facilitate the planning of maintenance and repair strategies for existing structures.

There have been a number of recent developments that are relevant to service life design and the prediction of the residual service life of existing structures, including.

• the improved ability to specify durable concretes for specific aggressive actions; 

• greater awareness of the causes of durability failure in concrete structures; 

• introducing additional protective measures for corrosion resistance; 

• the emergence of a better perspective of the relative importance of different deterioration mechanisms affecting concrete and the development of predictive models to quantify their effects; 

• growing demand by owners for using whole life costing (see page 3) in optimising the balance between initial and running costs for structures.