Abstract
The potential release of elements from potassic and calcic–sodic feldspars into the concrete pore solution was evaluated by ICP-MS using 1 N NaOH and KOH solutions at 80 °C in accordance with the conditions set in the chemical test method. Materials were characterized by petrography, XRD and by XRF analysis. The influence of textural and microstructural characteristics on the leaching process was also analyzed by immersing polished plates of each mineral in 1 N NaOH at 80 °C for 7 days. Optical microscope and SEM observations indicate that microstructural characteristics, such as cleavage zones, twins, grain–grain contact and the finer and less abundant phases in perthites, play a key role in the leaching process under alkaline conditions. Na 2O, K 2O, SiO 2 and Al 2O 3 are supplied by hydrolysis, although the participation of other processes cannot be ruled out.
Highlights
A significant percentage of the rocks used as aggregates in concrete come from metamorphic and igneous basement areas containing rocks such as migmatites, gneisses, schists and different types of granitoids
Feldspars rich in sodium and potassium are a potential source of alkalis that may be released into the concrete pore solution and contribute to trigger the alkali–aggregate reaction (AAR)
In this work we focus on to alkali release from potassic and calcic– sodic feldspars into alkaline solutions in order to understand the role played by each feldspar species, its composition and its microstructural and textural characteristics in the process
Summary
A significant percentage of the rocks used as aggregates in concrete come from metamorphic and igneous basement areas containing rocks such as migmatites, gneisses, schists and different types of granitoids. These rocks contain minerals of the feldspar group in varying proportions. They are found worldwide and especially abundant in the “Sierras Pampeanas de Córdoba,” Argentina. Due to their physical and mechanical characteristics, most of them can be used as concrete aggregates. Some of the most recent papers are those by Bérubé et al [1,2,3], Constantiner and Diamond [4], Leemann and Holzer [5], Lu et al [6], Shi [7] and Wang et al [8,9], this subject has been under study for 50 years
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