Cement materials

Cementstone is an impure (usually argillaceous) limestone, possessing the ideal balance of siUca, alumina, and calcium carbonate for Portiand cement (qv) manufacture. When calcined it produces a hydrauHc cementing material. 

The chelated calcium cementing materials are suppHed as two-part paste products. In use, equal parts of the two pastes are thoroughly mixed together to give a fluid mass that can be appHed without pressure over an exposed tooth pulp or in a deep-seated cavity. Under the influence of the oral temperature and humidity, the fluid mass sets to a hard, strong, therapeutic protective seal. 

Resin cement materials are provided as a two-part powder—Hquid product. The powder consists largely of poly(methyl methacrylate) to which various fillers (qv) maybe added. These include calcium carbonate [471-34-1], siHca [7631-86-9], barium carbonate [513-77-9], and calcium tungstate [7790-75-2]. An organic peroxide, eg, benzoyl peroxide, capable of generating free radicals is also present (see Initiators Peroxides, organic). 

A number of cement materials are used with brick. Standard are phenolic and furan resins, polyesters, sulfur, silicate, and epoxy-based materials. Carbon-filled polyesters and furanes are good against nonoxidizing acids, salts, and solvents. Silica-filled resins should not be used against hydrofluoric or fluosihcic acids. Sulfur-based cements are limited to 93°C (200°F), while resins can be used to about 180°C (350°F). The sodium silicate-based cements are good against acids to 400°C (750°F). 

Well cementing materials vary from basic Portland cement used in civil engineering construction of all types, to highly sophisticated special-purpose resin-based or latex cements. The purpose of all of these cementing materials is to provide the well driller with a fluid state slurry of cement, water and additives that can be pumped to specific locations within the well. Once the slurry has reached its intended location in the well and a setup time has elapsed, the slurry material can become a nearly impermeable, durable solid material capable of bonding to rock and steel casing. 

When the kiln material is cooled it forms into crystallized clinkers. These are rather large irregular pieces of the solidified cement material. These clinkers are ground and a small amount of gypsum is added (usually about 1.5 to 3%). The gypsum prevents flash setting of the cement and also controls free CaO. This final cement product is sampled, analyzed and stored. The actual commercial cement is usually a hlend of several different cements. This blending ensures a consistent product. 

When the water is added to the final dry cement material, the hydration of the cement begins immediately. The water is combined chemically with the cement material to eventually form a new immobile solid. As the cement hydrates, it will bond to the surrounding surfaces. This cement bonding is complex and depends on the type of surface to be cemented. Cement bonds to rock by a process of crystal growth. Cement bonds to the outside of a casing by filling in the pit spaces in the casing body [163]. 

Plant, C. G., Jones, I. H. Wilson, H. J. (1972). Setting characteristics of lining and cementing materials. British Dental Journal, 133, 21-4. 

H. Jusmes and E. Dahl-Jorgensen. Alternative cementing materials for completion of deep, hot oil-wells. Patent WO 9412445, 1994. 

Cracking can be caused by numerous physical and chemical phenomena in Portland cement materials. For example, freeze-thaw damage and ASR manifest themselves through crack development that may be studied using MRI. In addi-... 

The role of pectin in plant physiology is still far from clear. It is considered by some to be a cementing material but it is evident that the various types of pectic materials are able to perform in plants exceedingly varied biological functions. 

If there is one, record the unknown number of your cement material. Using the analytical balance, weigh approximately 1.0 g of the cement (do not dry first) into the crucible, transferring with a spatula. If the balance has a tare feature, you may use it, but make sure you have the weight of the crucible with lid recorded. 

Rixom, M.R. (1998) International Workshop on Supplementary Cementing Materials, Superplasticizers, and Other Chemical Admixtures, CANMET/ACI, Toronto, Canada. 

This shrinkage mechanism occurs only in pores within a fixed range of sizes. In pores larger than 50 nm the tensile force in the water is too small to cause appreciable shrinkage and in pores smaller than 2.5 nm a meniscus cannot form [122]. The amount of cement-paste shrinkage caused by surface tension depends primarily on the water-cement ratio, but it is also affected by cement type and fineness and by other ingredients (such as admixtures, and supplementary cementing materials) which affect pore size distribution... 

The significant increase in the use of supplementary cementing materials (such as fly ash and slag) in the last decade has dictated the need for an admixture that can offset the slowed hydration that results when such materials are incorporated in concrete. Strong basic salts such as sodium aluminate, alkali hydroxides, silicates, sulfates and thiosulfates have shown some promise. A number of proprietary admixtures which claim to catalyze the pozzalanic and thereby increase the rate of hydration are now marketed. 

The U.S. Department of Energy (DOE) found the cost to dispose of depleted uranium hexafluoride ranged from 4 to 12 billion. As an alternative to disposal, INEEL developed a concept of converting depleted uranium into an oxide aggregate material for use in cement. This cement material is known as Ducrete cement and is used as a shielding material (D202937, p. 1). 

Dmitriev, S. A., Lifanov, F. A., Varlakov, A. P., Karlin, S. V. Chernonozshkin, V. N. 1999. Obtaining of an alkaline cementing material on the basis of radioactive silt and LRW of low and intermediate activity level. In Waste Management 99 Conference. Laser Options, Inc., Tucson, CD-ROM. 

---