Design for chloride contaminated harsh environments: Concrete protection - The key to durable service life

Experience in the last forty to fifty years shows that current design specifications, even if properly implemented, do not provide. for adequate resistance of portland cement concrete to aggressive environments. Premature deterioration of concrete structures is still unacceptably high, and corrosion of reinforcement continues to represent the single largest cause of deterioration of reinforced concrete structures. In chloride contaminated hot/dry/humid conditions, the time-dependent and interactive effects of exposure and. climatic conditions initiate a cumulative deterioration mechanism which becomes an overall synergistic process, and a complex combination of many individual mechanisms, the exact role, effect and contribution of each of which to the totality of damage is not fully known. This paper advances an integrated, holistic approach - a global design/management strategy - which will enable us to design new structures with a specified, cost-effective durable service life when exposed to such aggressive environments. It is shown that in chloride environments, and rapidly drying ambient conditions, protection of the young concrete from external contamination is the first - but not necessarily the only one - reliable and positive step, to ensure long-term. material stability and structural integrity of concrete structures. Extensive data are presented to show that it is possible to develop concrete surface coatings which can provide long-term durable performance in terms of water-proofing qualities, adequate vapor diffusion, breathability, excellent bond to the concrete substrate, very low permeability to chlorides, moisture and carbonation under extreme exposure conditions, and also maintain the ability to bridge cracks.