ABSTRACT
The vulnerability of metals to alkali environments is not consistent, however. Steel encased in cementitious materials containing lime will be preserved by the highly alkaline environment. In contrast, lead and aluminium are etched by alkaline water running off from cementitious materials, and where concrete structures support metal sheets and components, a risk of condensation corrosion exists. This risk is enhanced where vapour barriers are omitted, inadequately positioned or jointed. The occurrence of reversible movement in metals is directly related to their coefficient of expansion. This can be significant, since typical values are 17.1×10-6 per °C for copper and 29.7×10-6 for lead. Failure to allow for this at joints and changes of direction will produce buckling, distortion and cracking.
