The effect of mineral additives on the development of alkaline corrosion in Portland cement concrete with reactive gravel aggregate

The intensity of the alkali-silica reaction (ASR), a destructive interaction between alkalis and reactive SiO₂ in materials containing Portland cement and aggregates, is usually assessed by the deformations of samples in an alkaline solution. With gravel aggregates containing reactive inclusions (2–4 %), deformations are not very significant (0.11–0.17 % in accordance with RILEM AAR 2.2), however, before the preventive measures had been introduced, that is, restrictions on alkali in Portland cement and concrete, ASR in concrete structures developed quite actively causing mainly surface destruction. This article describes a study of the effect of active mineral additives (AMA) on ASR in concrete with the mentioned gravel aggregate, which was evaluated not only by the development of deformations in an alkaline solution, but also by other criteria: strength and structural changes when exposed to alkalis, emergence of surface defects. It was established that the influence of fly ash and slag, which are known as ASR inhibitors, is ambiguous when their content in Portland cement does not exceed 20 % (Portland cement CEM II/A). A decrease in deformations indicates a positive effect of AMA, whatever their content in Portland cement is, however, there are signs indicating a "pessimum". Damage to the surface of samples in which Portland cement is replaced by 10 and 15 % fly ash and by 5 to 10 % zeolite is more significant than on samples with CEM I Portland cement. When using zeolite, a decrease in bending resistance of the samples is observed. As for the addition of slag (15 %), in this case, the damage to the samples is the same as with CEM I. Thus, the evaluation of the ASR intensity by the deformations of the samples is not effective in some cases. Despite fewer deformations in the presence of AMA in Portland cement, destructive processes due to ASR in concrete containing local gravel aggregate may intensify.

Author: J. Zvironaite, J. Pranckeviciene, J. Skamat, R. Stonys, J. Malaiskiene

Section: Concrete

Keywords: Portland cement, alkali silica reaction, supplementary cementing materials, gravel aggregates, fly ash, zeolite