Abstract
The dissolution kinetics of silica-containing minerals in aggregates influences strongly the process of ASR in concrete. In this paper, the effect of different ions on the dissolution rates of SiO2 (amorphous and quartz) and feldspars at high pH values was studied by following the increase of silicon concentrations in dissolution experiments and with a novel approach of measuring the evolution of scratches of polished surfaces. The second method avoided the problem of precipitation in some systems, such as the formation of C-S-H when calcium was present and lithium silicates in the presence of lithium. At high pH values, lithium, calcium and sulfate increased the dissolution rates of silica and feldspars, while iron, magnesium and additional NaCl, KCl or CsCl showed no significant effect. In contrast, aluminium slowed down significantly the dissolution rates of quartz, amorphous silica and Na and K-feldspar at for all temperatures studies: 20, 40 and 60 °C.
Highlights
Building materials play a key role in modern infrastructures and housing
The dissolution kinetics of reactive aggregates in con crete depends on different factors including i) the composition of the pore solution, which depends on cement and aggregate composition [4,7], ii) surface area, crystallinity and presence of crystal defects in the reactive aggregates [3], iii) moisture [8] and iv) temperature [7,9,10]
The present study investigates the effect of solution composition on the dissolution kinetics of silica and feldspars (K-feldspar and Na-feldspar) at high pH values by studying i) indirectly by following the increase of silicon concentrations during dissolution experiments, ii) by observing mass changes and iii) directly the dissolution of scratched surfaces, as an innovative method
Summary
Building materials play a key role in modern infrastructures and housing. Cement-based materials are in high demand because of their high performance, availability of raw materials, low cost, and relatively low environmental footprint per unit mass produced [1]. A possibility to lower the risk of damage due to ASR is to decrease the dissolution rate of silica-containing minerals within the aggregates, as the dissolution of metastable silica from aggregate is the initial reaction of ASR [12] This goal can be achieved by the use of appropriate cement paste, which changes the pore solution composition. The present study investigates the effect of solution composition on the dissolution kinetics of silica (amorphous silica and quartz) and feldspars (K-feldspar and Na-feldspar) at high pH values by studying i) indirectly by following the increase of silicon concentrations during dissolution experiments, ii) by observing mass changes and iii) directly the dissolution of scratched surfaces, as an innovative method
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