Proof for durability of chemically stressed concretes and concrete components: Proof of concrete attacked by carbonic acid

The findings on the chemical concrete attack by carbonic acid are essentially based on studies from the 1980s. For new, clinker-efficient cements, there is no experience available for their assessment in the case of a chemical attack. Also for the case of a strong chemical attack (XA3), no assessment concept is available for high performance concretes, which could perhaps abstain from the standardized “additional measures of protection”. In the Standard, reference is made to an unspecified expert solution.

Starting point is the determination of the degree of damage by the attack of carbonic acid on concretes which are approved for the exposure class XA2. These are to be compared with the degrees of damage of concretes that have not been approved so far. NMR is used as a non-destructive measuring method. As cements, mainly those with several main constituents in addition to Portland cement clinker will be used. From these results an assessment background will be derived. In future, this background in combination with the test method can be used for technical approvals for new cements.

In a second step, the attack conditions will be increased (XA3). The impacts  of higher concentrations of carbonic acid (> 100 mg / l) as well as chemical attack increased by flowing conditions will be investigated. Concretes, which despite the increased degree of attack can be classified by the previously derived XA2 assessment background, could in future also be used without additional protective measures in exposure class XA3.

The project is to be seen in the context of a research project on chemical attack by organic and inorganic acids under the leadership of the German Society for Concrete and Construction Technology (DBV). The results of both research projects will be presented and discussed in the VDZ committees.