Cementation secondary

Polymers are added to Portland cement based mortar systems for a number of reasons. Firstly, polymers improve the key properties of the fresh, non hardened mortar, i.e. adhesion, workability and open time. Polymer additives also tend to have a plasticizing effect on cementitions mortars, there by reducing the amount of added water to achieve needed workability and mortar flow properties. Minimizing added water results in fewer capillary pores, lower porosity and stronger cements. Secondary, the properties of a hardened cement mortar are improved. Properly selected... 

Sometimes primary cementations are not successful, for instance if the cement volume has been wrongly calculated, if cement is lost into the formation or if the cement has been contaminated with drilling fluids. In this case a remedial or secondary cementation is required. This may necessitate the perforation of the casing a given depth and the pumping of cement through the perforations. 

Petroleum. Apart from its use ia petrochemicals manufacture, there are a number of small, scattered uses of lime ia petroleum (qv) production. These are ia making red lime (drilling) muds, calcium-based lubricating grease, neutralization of organic sulfur compounds and waste acid effluents, water treatment ia water flooding (secondary oil recovery), and use of lime and pozzolans for cementing very deep oil wells. 

Table 3 Hsts the characteristics of CAC mineral constituents that can occur in CAC of varying purities. The primary hydraulic setting cement phase in all CAC grades is CA [12042-68-1/, CaO AI2O2 the main secondary phase in 70% AI2O2 CAC is Ca2, [12004-88-5] CaO 2AI2O2. CA2 and C 2 ...

Cobalt. There is no U.S. mine production of cobalt. Refining of imported nickel—cobalt mattes has not occurred since the mid-1980s. About 1600 t of secondary cobalt was recycled from scrap by 13 faciUties in the United States representing - 22% of total U.S. consumption. The price of the metal was around 44/kg. Most is imported from Zaire and Zambia. Increasing quantities are coming from Russia. Historically, the price of cobalt has been quite volatile and dependent on the pohtical environment in those countries. Cobalt is used in superaHoys, 40% catalysts, 14% paint driers, 11% magnetic alloys, 10% and cemented carbides and other uses, 16%. 

The calcium chelate cements are limited to the use of a cavity liner. They may be placed directly over an exposed tooth pulp to protect the pulp and stimulate the growth of secondary dentin, or used as a therapeutic insulating base under permanent restorations. The high alkalinity and high solubihty of these materials prohibits use in close proximity to soft tissues or in contact with oral fluids. 

Cement plants Quarrying primary crusher, secondary crusher, conveying, storage Particulates (dust) Wetting exhaust systems with fabric filters... 

In addition to primary cementing of the casing and liner, there are other important well cementing operations. These are squeeze cementing and plug cementing Such operations are often called secondary or remedial cementing [161]. 

There are two basic oil well cementing activities primary cementing and secondary cementing. 

Secondary or remedial cementing refers to cementing operations that are intended to use cement as a means of maintaining or improving the well s... 

The extraction technology is applied for scrap recycling of tantalum and niobium and for the treatment of related materials. Recovery of tantalum and niobium from secondary material, such as Sn slag, Ti slag, W slag, catalyst wastes, used cemented carbide and used tantalum capacitors was reviewed by Dai, Zhong, Li and Li [483]. 

Waste Treatment. Figure 2 outlines the current waste recovery and treatment processes, and proposed changes. Acid waste streams are sent through nitric acid and secondary plutonium recovery processes before being neutralized with potassium hydroxide and filtered. This stream and basic and laundry waste streams are sent to waste treatment. During waste treatment, the actinides in the aqueous waste are removed by three stages of hydroxide-iron carrier-flocculant precipitation. The filtrate solution is then evaporated to a solid with a spray dryer and the solids are cemented and sent to retrievable storage. 

As research progresses over the years it is becoming apparent that the majority of these cements are essentially amorphous, and that crystallinity is secondary and sometimes very slight. Kingery s arguments based solely on XRD data are, perhaps, not very relevant. 

Another biological disadvantage is that dental silicate cement does not bond to tooth material, and harmful substances and bacteria can percolate between it and the tooth, giving rise to secondary caries and pulpal irritation (Going, Massler Dute, 1960). These effects are magnified when dissolution of the cement occurs. 

Hals, E. (1975). Histology of natural secondary caries associated with silicate cement restorations. Archives of Oral Biology, 20, 291-6. 

The fact that the initial setting process for magnesium oxychloride cements takes place without observable formation of either the 5 1 8 or the 3 1 8 phase is important. It indicates that formation of an amorphous gel structure occurs as the first step, and that crystallization is a secondary event which takes place from what is effectively a supersaturated solution (Urwongse Sorrell, 1980a). This implies that crystallization is likely to be extremely dependent upon the precise conditions of cementition, including temperature, MgO reactivity, heat build-up during reaction and purity of the components in the original cement mixture. 

Bentonite is used in secondary cementing operations [1634]. High percentages of bentonite significantly reduce the specific weight of the slurry. 

Use of wastes as raw material or secondary fuel in cement manufacture... 

In the manufacture of Portland cement, many otherwise-waste materials can be used either as a substitute for the traditional raw material, or as a secondary fuel (e.g., used tires) [334,1577]. In particular, drilling wastes can be introduced in the clinker burning process [878]. For both waste disposal and cement manufacturers, a mutual benefit will emerge. The cement manufacturing companies reduce their demand for traditional raw materials and save the limited capacity of landfills and other waste-treatment industries. 

Calcinating a mineral removes its volatile components, such as water or carbon dioxide and leaves an usually crumbly solid residue. Calcinated secondary minerals such as limestone are the basic components of building cements, and in extractive metallurgy operations they facilitate the smelting of metals. Calcinating limestone (composed of calcium carbonate), for example, drives away carbon dioxide, leaving a solid, friable residue of quicklime (composed of calcium oxide) ... 

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