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Aggregates
Published in M. Rashad Islam, Civil Engineering Materials, 2020
Igneous or metamorphic rocks are disintegrated by weathering and erosion processes over the millions of years they are formed. The disintegrated rock particles are then transported to different places and/or in water bodies with the actions of wind, rain, ice, mass movement, glaciers, and so on. The deposition and subsequent cementation of these disintegrated rock particles, at the surfaces and within bodies of water in layers of strata, become what are called sedimentary rocks. These rocks cover about 75% of the total land surface (Somayaji 2001). Calcareous rocks such as limestones, chalk, etc.; siliceous rocks such as sandstones, cherts, etc.; and argillaceous rocks such as shale are examples of common sedimentary rocks.
Petroleum Geological Survey
Published in Muhammad Abdul Quddus, Petroleum Science and Technology, 2021
‘Microfossils’ are found in the deep ocean bottom. The fossils contain siliceous matter. The microfossils were produced from the remains of algae bacteria microorganisms. The remains of the microorganism, on being compressed and cemented, become constituents of the rock. Chemically the microorganisms composed of siliceous compounds (SiO2 units) form “siliceous rock” or “siliceous ooze”. Siliceous ooze is a soft deposit of fine-grained siliceous remains along with some clay. Various types of microfossil exist.
Predictive quantitative model for assessing the asphalt-aggregate adhesion quality based on aggregate chemistry
Published in Road Materials and Pavement Design, 2021
The current consensus within the field is that aggregates with high contents of silicon dioxide or SiO2 (e.g sandstone or granite) have a higher moisture susceptibility than aggregates with high contents of calcium oxide or CaO (e.g. limestone) (Kim et al., 2008). However, a comprehensive predictive model for moisture damage in which the influence of each major compositional oxide of the aggregates is considered is not currently available. For instance, it is not clear what would be the moisture susceptibility of an aggregate with high contents of both SiO2 (an oxide which promotes moisture damage) and CaO (an oxide that inhibits moisture damage), since these two oxides are compatible, which means that these aggregates can exist and are, in fact, quite common (Pettijohn, 1975). Conflictive characterisation of aggregates, such as the acid-basic scale in which acidity is related to high SiO2 contents and basicity is related to high CaO contents (Kakar et al., 2015), have further normalised the flawed idea that these two oxides could not be present at the same time within an aggregate. Geochemically speaking, dividing aggregate characterisation in siliceous (i.e. silicon dioxide, SiO2, as the major constituent) and calcareous (i.e. calcium oxide, CaO as the major constituent) rocks would be more inclusive, as this does not imply exclusivity within these two oxides. Moreover, the petrogenesis (i.e. how the rocks were created) and secondary chemical composition of these two broad categories of rocks are very different, which would imply that their interactions with the asphalt binder must be studied separately. Calcareous rocks (e.g. limestone) were formed almost exclusively on costal environments by the sedimentation of calcium-rich organisms (Tucker, 2009); further metamorphic processes transformed these limestones into marble, which are also calcareous rocks since metamorphic processes do not alter the chemical composition of the original rock (Bucher & Frey, 2002). Siliceous rocks, on the other hand, were mainly formed through igneous cooling of magma (e.g. granitic rocks); from here, erosion and metamorphic processes gave rise to many different types of rocks such as sandstones and quartzites, respectively (Bucher & Frey, 2002; Pettijohn, 1975; Tucker, 2009).
Elemental characterization of quartzite of Pouma sub-division of Cameroon and radiation attenuation properties based on XCOM and GEANT4 Monte Carlo simulation
Published in Radiation Effects and Defects in Solids, 2022
Patricia-Laurelle Degbe, Cebastien Joel Guembou Shouop, Daniel Bongue, Merylle Glawdys Beyinda, Maurice Ndontchueng Moyo, Moïse Godfroy Kwato Njock
Quartzites are rocks formed of quartz crystals and defined as siliceous rocks among different commonly used types of rocks (igneous, sedimentary and metamorphic rocks). They come either from the recrystallization of a Quartz strand (gneiss) or from the cementation of a sandstone. They have several applications because of their form, durability, and slice alignment that could be easily separated into thin or thick parts. The density of quartzite varies from 2.6–2.7 g/cm3 or an average of 2.65 g/cm3 (40, 41). The sample selection was justified by the applications of the investigated rocks. Their applications are nationwide acknowledged as these rocks are used in almost every part of the country and worldwide as few importations have been made in neighboring countries. The following list shows a few applications of the quartzite rocks from Pouma (Cameroon): The exploitation of rocks of Pouma makes the main activity of the local population. A flourishing trade of it is being developed locally and the activities of extracting and exporting nationwide contribute to the growth and the development of the locality.Pouma rocks have been recognized as one of the best decorative stones on the world market (EcoMatin. 2018). As the population makes daily use of Pouma rocks in the preparation of dishes (specifically to grind food), it is of great importance to assess these rocks.Used as building materials in the construction of houses, hospitals, and other administrative areas, it is worth valuing the evaluation of the rocks radiation attenuation properties (especially if it is being used in the construction of radiographic test rooms);Their use in manufacturing aggregates for building materials is another asset of the investigated rocks;Other minor applications of these rocks include the non-exhaustive following: manufacturing of tiles for the covering of walls and facades, manufacturing of glasses (Glassmaking company SOCAVER), manufacturing of thermal or acoustic insulation materials, and the use for re-mineralization and fertilization of agricultural soils … etc.