Alkali–silica reaction

Crystal structure

Optics

Physics

Engineering

Mortar

Composite material

Nanotechnology

Organic chemistry

Inorganic chemistry

Chemistry

Metallurgy

Materials science

Alkali metal

Mineralogy

Silicate

Calcium silicate

Characterization (materials science)

Raman spectroscopy

Chemical engineering

Calcium

Crystallography

Cement and Concrete Research

The reaction mechanism of alkali-silica reaction (ASR) is poorly understood due to the difficulties to directly characterize ASR products in concrete. In this study, ASR products with initial Ca/Si of 0.25 and (K + Na)/Si ratio 0.5 with different K/Na ratios are synthesized at 80 °C. The synthesized ASR products are characterized by different techniques, also the solution chemistry is analyzed and saturation indices are calculated. The results show that crystalline and nano-crystalline phases are formed in the presence of both alkalis and calcium. No ASR product is present in the absence of calcium. All synthesized crystalline ASR products highly resembles the crystal structure of shlykovite, indicating that a substitution of K in shlykovite by Na can occur. Its silicate sheet structure has strong similarity to the ASR products formed in concrete according to Raman spectra, while some differences are observed in their morphologies and basal peak of the XRD patterns.

Synthesis, characterization, and water uptake property of alkali-silica reaction products