The Response of Synthetic Alkali-Silica Reaction Products to Carbonation

Alkali-silica reaction (ASR) is one of the most studied deterioration mechanisms of concrete. However, the ASR mechanism in the presence of external environments such as carbonation is yet to be understood. The present study simplifies this research gap by subjecting the synthetic ASR gels to carbonation and evaluating the changes in the gels through microanalytical studies. Synthetic ASR gels are prepared and subjected to 3 days of carbonation at 3% CO₂ concentration. Thermogravimetric analysis indicated the uptake of CO₂ in the form of calcite validating the interaction of ASR and carbonation. Nanoindentation demonstrated the improvement in mechanical properties of the synthetic gel due to carbonation. Electron microscopy coupled with energy dispersive spectroscopy revealed the compositional changes of the gel caused by its interaction with CO₂ that led to the improvement in their mechanical properties. These results suggest a possible increase in the deterioration of concrete due to the interaction of ASR and carbonation.