Survey of condition of precast high-alumina cement concrete components in internal locations in 14 existing buildings

Abstract

Over the past few years the Building Research Establishment has carried out surveys on 14 buildings between 20 and 35 years old to assess the performance of precast high-alumina cement (HAC) concrete components in service. The single most important finding of these investigations is that the majority of the floor and roof components are carbonated to the depth of the steel. Even though subsequent reinforcement corrosion has not caused disruption to date, the future risk from corrosion in such beams is still unclear, even in nominally dry internal conditions. Chemical attack, which may greatly affect the structural performance of HAC concrete components, has not been identified as a major problem in the 14 buildings investigated, although a few isolated instances have been found in some of the components exposed to persistent water penetration. The implications for structural assessment are also discussed in this Paper. The Building Regulations report by Sub-committee P remains the current guidance on the strength of HAC concrete components produced by the long line casting process, except in situations where chemical attack has been diagnosed.