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The calcium carbonate content of limestone rocks has been used from the earliest civilisations, dating back to 14,000 BCE, to its extensive use in modern times. It is a valuable resource that services the needs of a multitude of industries.
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Depending on the quality of the deposit, limestone can be quarried to service the needs of the building and construction industries. For example, certain types of limestone such as that found in North Otago can be cut into blocks suitable for direct use as building stone Oamaru stone. In road construction, limestone aggregate direct from the quarry can be used as base material.
Lower-grade limestones, particularly ones with some clay content, can be used in the production of cement for use in the building and construction industry. Cement is a key ingredient of concrete, huge volumes of which are poured each day to serve as roading, foundations, structural beams and columns.
Concrete is a hardened material that forms when a mixture of cement, sand, crushed stone and water is poured into moulds or formwork and allowed to cure or harden. Cement is made by strongly heating a mixture of limestone, silica and clay in a kiln until small pea-sied lumps called clinker form. This is then ground to a powder, the key ingredients of which are dicalcium silicate, tricalcium silicate, tricalcium aluminate and calcium oxide.
When water is added to dry cement powder to make a stiff mix, a complex series of chemical reactions hydration occurs, which begins the hardening process. Over time, the hardening process continues until full strength is obtained.
New Zealands total cement production in 2010 was approximately 1.1 million tonnes.
Limestone deposits with a calcium carbonate content around 90 can be quarried to be used by the farming sector. By crushing the limestone, various grades based on particle sie can be produced. These products are marketed as agricultural lime.
Soil acidity is one of the factors that can influence plant growth and can seriously limit crop production. By spreading agricultural lime onto the paddock or soil, the calcium carbonate content of the limestone is capable of neutralising some of the acid in the soil. This also has the effect of freeing up some of the soil minerals, such as phosphates, and making them available for absorption into the plant.
In the steel production process carried out at the Glenbrook plant south of Auckland, large amounts of limestone and lime are needed to remove impurities during the iron ore reduction phase and the steel production phase. The torohanga region supplies these much-needed ingredients.
Calcium oxide, obtained from limestone, acts as a pH regulator when extracting gold from quart. The chemical extraction of gold from powdered quart rock uses a solution of sodium cyanide. In this cyanidation process, the pH of the solution needs to be maintained between 1011 to prevent the production of deadly hydrogen cyanide gas. The addition of calcium oxide to the solution maintains the pH 1011 level.
Fossiliferous Limestone Usage in Construction Industry Fossiliferous limestone is crushed and mix with clay. The mixture then heated in kilns to make Portland type of cement. Calcium sulfate used as an additive to stop the early setting of the cement-water mixture.
Oct 18, 2009nbsp0183321. Limestone is a type of sedimentary rock that is mainly made up of a substance called calcium carbonate. Calcium carbonate has the chemical formula, CaCO3 Because it has many uses and can be used to make other products, limestone is a valuable resource. 2. Basic properties of limestone The appearance of limestone can vary tremendously.
Relevant identified uses of the substance or mixture and uses advised against Limestone may be used in the manufacture of bricks, mortar, cement, concrete, plasters, paving materials, and other construction materials. Limestone aggregate may be distributed in bags, totes, and bulk shipments. No known recommended restrictions.
a sedimentary rock consisting primarily of calcite CaC0 3 more rarely of aragonite. The most frequent impurities in limestone are dolomite, quart, clay minerals, and the oxides and hydroxides of iron and manganese, as well as pyrite, marcasite, phosphates, gypsum, and organic matter.
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