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Minerals and rocks
Published in A.C. McLean, C. D. Gribble, Geology for Civil Engineers, 2017
Calcite is an essential mineral in limestones and may be present in many sedimentary rocks as the cement matrix. It is the principal constituent of marble. Limestone deposits may be crushed to a fine powder and used as agricultural lime. The neutralising value of any calcite limestone deposit must be known for this purpose, and in many regions agricultural lime with a higher MgO content may be preferred; that is, the limestone will be composed of both calcite and dolomite. In many countries of the Middle East, limestones are widespread and may be the only material available to use as a crushed rock aggregate for concrete or roads. Limestones are also the most important constituent in the manufacture of cement.
Ground improvement
Published in Alan J. Lutenegger, Soils and Geotechnology in Construction, 2019
The mechanisms of lime reaction with soil depend on the type of lime used and the soil. The most frequently used limes in stabilization are quicklime (CaO) and hydrated lime (Ca(OH)2). Quicklime for use in soil stabilization is produced by heating limestone (CaCO3) to remove carbon dioxide (CO2), leaving calcium oxide (CaO); hydrated lime is produced by running crushed quicklime through a water hydrator to form calcium hydroxide (Ca(OH)2). Agricultural lime (calcium carbonate, CaCO3) will not react with soils and should not be used in stabilization of fine-grained soils.
The effect of sodium alginate, lignosulfonate and bentonite binders on agglomeration performance and mechanical strength of micro-fine agricultural lime pellets
Published in Particulate Science and Technology, 2021
Claudia F. Schwaeble, Robert W. M. Pott, Neill J. Goosen
Agricultural lime (CaCO3) is typically applied to acidic soil in order to increase its pH to the crop-appropriate level, as well as avoiding the effect of acid solubilized toxic metals on root development. Agglomerates of micro-fine CaCO3 can be applied to the soil rather than powdered limestone, as it is easier to handle in windy conditions. In this study, sodium alginate, lignosulfonate and bentonite are used as binders to ensure that the agglomerates remain intact after being produced in a bench-scale disk agglomerator. The agglomeration process was optimized with regards to the liquid required to produce a standard size agglomerate of 2–5.6 mm. The production of 100 g agglomerates required approximately 20 ml. After production, the agglomerates underwent an impact-, abrasion resistance-, compression- and moisture disintegration-tests to determine if they would be able to withstand the stresses of handling and transportation. Only agglomerates of 3–5 g/kg sodium alginate and 70 g/kg bentonite agglomerates performed satisfactorily in the strength tests. Exploitation of the stiff product that forms when sodium alginate comes into contact with calcium ions, proved valuable in the production of strong agglomerates that can be used in agriculture.