Expansion cement

The expansive component C A SI in Type K expansive cements hydrates in the presence of excess sulfate and lime to form ettringite is... 

ASTM C845 Type E-I (K) expansive cement manufactured ia the United States usually depends on aluminate and sulfate phases that result ia more ettriagite formation duriag hydration than ia normal Portland cements. Type K contains an anhydrous calcium sulfoaluminate, C A SI. This cement can be made either by iategraHy burning to produce the desired phase composition, or by intergrinding a special component with ordinary Portland cement clinkers and calcium sulfate. 

Cohen, M. D. 1983. Theories of expansion in sulfo-aluminate-type expansive cements schools of thought. Cement and Concrete Research, 13, 809-818. 

Expansive cements are hydraulic cements designed to expand rather than shrink on curing, as do standard Pordand cements. They are defined in ASTM C845 and are used to control and reduce shrinkage cracks in large poured-in place structures. 

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 even an almost complete reduction in expansive properties with expansive cements in the presence of water-reducing admixtures. However, pozzolans such as fly ash appear to behave normally with water-reducing admixtures. 

Calcium Aluminate, Expansive and Other Cements 335 10,2 Expansive cements 10.2.1 General... 

In any expansive cement, the amount of expansion and the period during which the expansive reaction occurs are critical. The reaction must take place after the concrete has developed some strength, but before exposure to a reduced RH places it in tension, which could cause irreversible damage. 

Probably a majority of practical expansive cements have depended on the modification of a Portland cement in such a way as to increase the formation of ettringite. Single expansive cement clinkers can be made, but it has been more usual to produce admixtures that are blended or interground with a normal Portland cement or clinker. Blending has the advantage that the... 

M99 Mikhailov, V. V., in Klein Symposium on Expansive Cement Concretes (Sp. 

A type No. 29 Sauereisen low expansion cement was used for connection of the electrode body and the silver-silver chloride wire. The concentration of the KCl solution in the electrode for this study is 0.1 mol/1. The iron alloy working electrode dimensions were 20mm x 5mm x 1.5mm. The body of the reactor served as the a uciliary electrode. 

Expansive cements are available in some countries and may be incorporated in Portland cement mixes to provide expansion which, as with granulated iron, can continue beyond the plastic phase. 

Other types of cement than those of Table 1.3 are available for special uses. These are for instance low heat cements to be used when low heat of hydration is desired such as in massive structures, sulfate-resisting cements to be used to increase the resistance of concrete to sulfate attack, expansive cements, quick setting cements, white or coloured cements, etc. [2]. 

There are the other reactions or processes hnked with volume increase of the mixture, in which they proceed. Some of them are mentioned in Chap. 5. For mar reasons these reactions cannot be used in the production of expansive cements. 

Mehta [59] developed the method of expansive cement production, containing MgO grains. In order to obtain good expansion magnesite should be decarbonated 1 h at temperature of 900 4-950 °C and the size of MgO grains should exceed 300 pm. The addition of such prepared expansive agent should be 5 4-10 % by mass of cement. 

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