Performancebased Specification Of Concrete For Durability- Carbonation-Induced Corrosion

Abstract

Sustainability lity of concrete in terms of thermal l mass and low operational l CO2 makes it a first choice of the construction industry over steel. The working life of concrete structures and their repair costs depend directly o n the ability of concrete t o resist corrosion of steel (Figure 1). Whilst carbonation in p lain concrete is not a major threat, in reinforced and prestressed concrete members, it brings d own the alka linity of the concrete around the reinforcement creating a conducive environment for corrosion to occu r. The knowledge gained from the vast accumulated past experiences has enabled the standardisation of concrete specifications in terms of mix proportioning, resulting in better use of materials and tough contro ls in ready-m ixed concrete production. Having realised production of consistent quality concrete that is durable as intended by way of standardisation, it is up to the end user to utilise it with appropriate aftercare in terms of placement, moist curing etc. For example, the onerous task of fi xing accountability in the UK on the specifier and the producer has been well-defined and quantified in BS 8500 Parts 1 and 2 (British Standards Institution (BSI), 2002; 2006; 2015) w hich helps in producing durable concrete conforming to the Standards on a routine basis. The signifi ca nce of such a prescripti ve approach rather than a restrictive one is the support gathered from long-term experiences along with judicious interpretation.