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Natural aggregate sources and production
Published in Mark Alexander, Sidney Mindess, Aggregates in Concrete, 2005
Mark Alexander, Sidney Mindess
Chalcedony: A fibrous form of quartz with submicroscopic porosity. Frequently occurs with chert and is usually alkali-reactive. Tridymite and Cristobalite: High temperature crystalline forms of silica associated with volcanic rocks, and alkali-reactive.
Residual alkali–silica reaction of coarse recycled concrete aggregate based on the application of a prescriptive measure from the Argentinian regulation
Published in European Journal of Environmental and Civil Engineering, 2023
Claudio Javier Zega, Darío Daniel Falcone, Silvina Marfil, Gabriela Soledad Coelho dos Santos, Ángel Antonio Di Maio
SC specimens (stored at 38 °C and in the fog room, at 23 °C) have similar characteristics. The granite used as coarse aggregate is composed of subhedral to anhedral quartz, plagioclase and K-feldspar (with a slight alteration to kaolinite and illite). Also, hornblende, pyroxene and biotite (partially deferrised and chloritised) were observed. In some sectors, very scarce subgrains, microcracked and fine-grained quartz were identified (<2%). The siliceous sandstone is composed of well-rounded quartz clasts cemented by chalcedony, opal and cryptocrystalline silica. In general, this rock shows reaction processes with the development of microcracks filled with reaction products that continue in the mortar. The prisms cured at 38 °C have abundant microcracks that also affect some granite particles and the new mortar (Figure 9(a)). Figure 9(b) corresponds to the SC stored in the fog room, where a microcrack is observed in a sandstone particle-mortar contact. The microtextural characteristics, the intense microcracking, as well as the reaction rims observed in the contacts with the sandstone, are clear evidence of the ASR development.
Microindentation testing as a means of predicting lump iron ore physical properties
Published in Mineral Processing and Extractive Metallurgy, 2023
Microindentation testing was undertaken on a reference suite of well-defined material types/ore groups from a variety of different Pilbara iron ores. For practical reasons, test work was conducted on −8 + 6.3, −6.3 + 4, −4 + 2 and −2 + 1 mm size fractions. 727 microindentations (approximately equal numbers of Vickers and Knoop) were conducted on 19 different ore groups across 17 samples from six different iron ores. Three of the 17 ore samples utilised for microhardness testing were also used for lump ore sorting (Lump ores A, B and C from Table 2). Mean data for a variety of textural types of hematite (microplaty hematite, martite and hydrohematite), goethite (vitreous, earthy and ochreous goethite) and magnetite (e.g. kenomagnetite) were then used to calculate a representative ore group Vickers microhardness and representative ore group fracture toughness. Data was also obtained for quartz, chalcedony and shale. Ore groups used were from the CSIRO Iron Ore Classification Scheme and are listed in Table 1.
Hydrothermal alteration and corresponding reservoir significance of the Permian Emeishan basaltic lavas, west Sichuan, China
Published in Australian Journal of Earth Sciences, 2023
Y. B. Sun, Y. F. Zhang, A. H. Xi, Y. Tang, B. J. Zhang, S. Q. Pei, R. R. Li, H. Yin, Q. Zeng, H. Z. Qu, R. J. Zhou
The middle sub-section has a predominance of small dissolution caverns, amygdales, and structural fractures (Figure 3a–c), which jointly form the dissolution-filling zone. Small dissolution caverns are concentrated from the bottom to the middle of this sub-section, mostly irregular, with diameters generally 1–5 cm. The caverns are filled with multi-stage siliceous minerals such as opal, chalcedony and quartz (Figure 3d), and some have chlorite near the cavern wall. The amygdales are mostly primary amygdales with rounded, oval and irregular shapes and diameters of 1–2 cm, and are generally filled with chlorite. Structural fractures are divided into two groups, with fracture widths of 1–3 mm. These fractures, oblique or vertical, are commonly seen with dissolution-induced expansion, and some cut through amygdales showing that fluid dissolves and fills the primary amygdales via the fracture migration channel; secondary amygdales mostly have irregular edges and are larger (Figure 3e).