Special Cements

According to Kurdowski and Sorrentino the special cements are these, which properties are outside the limits included in standards, relating to the oniinaiy cements [1,2], They are devoted to the special applications and are frequently produced with unconventional methods or from atypical raw materials. This definition based on use is restrictive, because it does not take into account that it is possible to produce concrete with special properties from ordinary cements by using various additives and admixtures or by thermal treatment, during the hydration stage e.g. autoclaving. 

One can expect that the properties of some special cements will be standardized and these materials will join the group of conventional binders. However, other will remain for the long time in the group of imtypical, special cements. The examples of the latter are white and calciitm aluminate cements. 

InPohsh Standard PN-B-19707 the following special cements are distinguished  

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Welan has similar properties to xanthan gum except that it has increased viscosity at low shear rates and improved thermal stabiUty and compatibihty with calcium at alkaline pH (90). The increased thermal stabiUty has led to its use as a drilling mud viscosifter especially for high temperature weUs. The excellent compatibihty with calcium at high pH has resulted in its use in a variety of specialized cement and concrete appHcations. 

Other Phases in Portland and Special Cements. In cements free lime, CaO, and periclase, MgO, hydrate to the hydroxides. The in situ reactions of larger particles of these phases can be rather slow and may not occur until the cement has hardened. These reactions then can cause deleterious expansions and even dismption of the concrete and the quantities of free CaO and MgO have to be limited. The soundness of the cement can be tested by the autoclave expansion test of Portiand cement ASTM C151 (24). 

Cement-Lined Steel Cement-hned steel pipe is made by lining steel pipe with special cement. Its use prevents pickup of iron by the fluid handled, corrosion of the metal by brackish water, and growth of tuberculation. Threaded pipe in sizes from to 4 in is stocked however, cement-lined pipe in sizes smaller than in is not considered practical for common use. 

Cement-Lined Carbon-Steel Pipe Cement-lined carbon-steel pipe is made by lining steel pipe with special cement. The cement lin-... 

It was shown earlier that aggregate types do not materially affect the performance of water-reducing admixtures. This is not true for cement and mixes containing special cements require particular care. Examples here are increased retardation with low C3A cement (for example, sulfate-resistant cement) and... 

Admixtures should be purchased under specifications that stipulate the desired properties, exclude adverse effects and provide evaluation of uniformity of the admixture from batch to batch. The user should ensure that the admixtures being considered conform to ASTM or other applicable specifications and the manufacturer of the admixture should be required to certify that individual lots meet the requirements of applicable standards or specifications. The following information should be provided by the admixture manufacturer or supplier (1) composition of the admixture in terms of the generic type of its main constituents (2) incompatibility with other admixtures or special cements (3) typical dosage (4) detrimental effects of overdosage or underdosage (5) chloride content and (6) whether air is entrained at the recommended dosage. 

MacDowell, J. F. 1991. Stratlingite and hydrogamet from calcium aluminosilicate glass cements. In Special Cement Advanced Properties, Mater. Res. Soc. Symp. Proc., 179, 159-179. 

Maintenance difficulties encountered with floors and roofs should be given particular attention in a structural design. Concrete floors are used extensively in the process industries, and special cements and coatings are available which make the floors resistant to heat or chemical attack. Flat roofs are often specified for industrial structures. Felt saturated with coal-tar pitch combined with a coal-tar pitch-gravel finish is satisfactory for roofs of this type. Asphalt-saturated felt may be used if the roof has a slope of more than jin./ft (4.17 cm/m). 

Nonmetallic castable refractories, reinforced with hexagonal steel mesh, are particularly good, since they resist both corrosion and erosion. Conventional refractories are susceptible to deterioration by water sprays, but this difficulty can be overcome by shielding from water impingement or by use of special cements. For best results, the refractory is installed flush with the surface of the steel mesh and is commonly applied with a pneumatic gun to ensure completeness of fill and maximum... 

Keywords wood-chip concrete, recycling of used timber, special cement paste, injection method of cement paste, wood-chip packing ratio, strength, specific gravity, thermal conductivity... 

Bentonite or other clays are added to the mud if there are not enough clays or solids present. Fibrous materials such as special cements, sawdust, beet pulp, cellophane and shredded plastic foil may be used as a seal. High-density fluids are used to prevent blowouts, and weighting materials, such as barite, may be added to increase the weight of the mud for deep drilling. 

Definition. Concrete is a mixture of cement (portland, natural, or special cement), fine aggregate (sand), coarse aggregate (gravel), and water. Concrete mixtures are defined by a volume ratio, i.e., 1 2 4 concrete contains 1 part of cement, 2 parts of sand, and 4 parts of gravel. Additive materials, such as lime and calcium chloride, are used to prevent freezing, improve workability, and accelerate the setting time. 

The causes of breaking of asphalt emulsions in contact with mineral particles of various nature are analysed in [216]. When mineral particles are in contact with water, the pH value of the medium changes and the emulsions stabilised by cationic surfactants are stable between pH 1.3 to pH 6.3. Emulsions stabilized with anionic surfactants break at pH < 10. In Japan [217], special cement-asphalt emulsions have been developed for low-traffic roads. 

There are four kinds of materials used in paste-like filling, which are fragmentized coal gangue, fly ash, special cement and water. The process of filling is as follows (Sun Henghu, et al. 2002) ... 

In the next place, mixing the coal gangue, fly ash, special cementing material and water in proportion to make into paste-like slurry. 

There are few differences in the setting time in the world standards initial setting time is in the range 40-90 min, the final is 6, 8, and 10 or 12 h. Much higher differences are embracing special cements beyond the standards (see Chap. 8). In EN 197-1 standard there is even no requirement for final setting time. This approach is,... 

In the past the division of cements on the basis of phase composition was applied, as follows alite, alite-celite (Tdmebohm called brownmillerite celite), alite-aluminate and others (Fig. 1.5) [31]. Such division, although fully justified, gives few information to the user— properties of several classes are very approximate, it has no application to cements with additions and for these reasons has no practical use. However, the chemists use it frequently enough for cement kind definition, especially in the case of special cements, which are discussed in Chap. 9. 

The studies on the immobilization of heavy metals in concrete have been developed for the last 20 years [316-320]. It has been found that the concrete is a very effective heavy metals immobilizing matrix. The combinations with AFm phases are formed these phases have a layer stracture and the exchange of OH ions with monovalent and bivalent anions is possible [317]. The strong adsorption on C-S-H gel is an important factor, and morphology of this phase is markedly modified [318]. Cement with zeolites addition can be applied to immobihze the radioactive elements [319]. Special cement with high aluminates content has shown high effectiveness for heavy metals immobilization [320]. 

Special cements with silica fume, giving condensed, compact pastes (DSP) with high content of ultra-fine particles, have very good freeze-thaw resistance [80], It is caused by extremely low capillary porosity and hence very low content of freezable water in these pastes. The same rerrrark can be related to the reactive powder concrete (RPC), for example the Ductal type composite [335], This question will be discussed in Chap. 10. 

The total annual output of silica fume is low, about 1.2 million tons, from which 30% is delivered by USA, Japan and Norway [16] (inPoland—about 10,000 tons). Therefore this material is expensive. Moreover, because of the high fineness and low density (2.1-2.25 g/cm ) their handling and transport are troublesome. Hence, their practical application is focused in the production of special cements and concretes. This problem will be discussed in Chap. 10. 

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