Over the recent years the amount of fast destruction defects of cement paste matrix has increased markedly for exposed concrete structures of highway and airport pavements. The accelerated destruction of silicate structure is unusual due to its irregular occurrence. It only occurs at 30 to 50% of newly built pavements (in continuous segments). The issue is applicable to loaded as well as unloaded pavements. Detailed diagnostics found that the probable cause is based on concurrently occurring expansive reactions in capillaries, cracks and pores in the cement paste matrix. In defect spots the presence of several expansive substances was proven, wherein the biggest question poses the unexpectedly high potassium concentration. Potassium is only contained at best in trace amounts in road concrete input components in the Czech Republic. Neither existing regulations nor standards sufficiently deal with this type of defects of cement concretes. If they mention the existence of this issue at all, they are just limited to recommendations. Since the modification of the existing commercially produced cements to pavements is still improbable, the solutions to this issue seem problematic.

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The short material service life of concrete is currently a frequently discussed topic, especially for newly constructed roadways with cement concrete pavement. This early degradation of cement concrete pavement slabs is a major problem that threatens the service life of sub-sections or the entire road. As some partial results demonstrate, a possible cause of this degradation can be seen in the surrounding road environment, namely the possibility of transferring aggressive substances to the concrete pavement slab. This paper is concerned with the verification of the possibility of the penetration of alkalis penetration from the surrounding environment into the concrete pavement slab by simulating the effect of different external conditions and environments.

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