Influence of the Quartz Deformation Structures for the Occurrence of the Alkali–Silica Reaction

Abstract

Defects in the crystalline structure of quartz facilitate the connection with the alkali hydroxides, since under a high alkalinity condition (e.g., in concrete), the Si-O bonds of quartz are easily broken. This study set out to investigate the influence of the deformation structures of quartz on its susceptibility to the alkali–silica reaction. A granite, a protomylonite, and a mylonite were selected for this study. Using optical microscopy, the quartz grains contained in these rocks were quantified and their texture characterized. The quartz samples extracted from the rocks were analyzed by magnetic nuclear resonance, to evaluate their potential for dissolving silica as well as changes in their atomic scale before and after the reaction with alkali hydroxides. These analyses were compared with the results of the accelerated mortar bar test. The study showed that the quartz with intense undulatory extinction and deformation bands denotes the most favorable condition to the development of the alkali–silica reaction. However, on an atomic scale, the slightly deformed grains were highly prone to react. Thus, in a high alkalinity condition, over a long period of time, any quartz tends to develop the alkali–silica reaction, regardless of the deformation degree of the grain.

Associations of Gangue Minerals in Coal Flotation Tailing and Their Transportation Behaviors in the Flotation Process

“…26,27 The peak marked by the dotted line on the right was Q 4 , corresponding to the coordination of silicon in quartz. 28 These results were consistent with the XRD analysis. For F r products, two new peaks (i.e., peak 1 and peak 2) were observed, indicating that the Si in F r products had other coordination forms besides kaolinite and quartz.…”

“…The Si in kaolinite is tetracoordinated, and the silicon-oxygen tetrahedron is connected with an aluminum-oxygen octahedron and three other silicon-oxygen tetrahedra. As observed, the peak at around a chemical shift of 97 ppm was Q 3 , corresponding to the coordination of silicon in kaolinite. , The peak marked by the dotted line on the right was Q 4 , corresponding to the coordination of silicon in quartz . These results were consistent with the XRD analysis.…”

Durability Behavior of Mortars Containing Perlite Tailings: Alkali–Silicate Reaction Viewpoint

“…Such SiO 2 and Al 2 O 3 contents plus values of alkaline equivalents (Na 2 O eq ) greater than 5% can trigger characteristic expansions of alkali-aggregate reactions (Table 2). The amorphous alkaline gel is the main product of such reactions and has high water absorption, which can cause expansion and consequent cracking of the cementitious materials [33][34][35]. Table 2 presents the chemical composition of the PP and CP tailings used in this research.…”

Alkali-Silica Reactivity of High Density Aggregates for Radiation Shielding Concrete

“…It was shown that products of the reaction were associated with coarse-grained quartz (up to 1500 μm in size and essentially free of deformation), whereas granitic mylonites containing microcrystalline quartz and low amounts of mica were found to be innocuous. However, according to Tiecher et al [45], under favorable conditions of temperature, humidity, and access of alkali over a long time period, each type of quartz tends to provoke the alkali-silica reaction.…”