Low-heat cements

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]. 

Clinkers with increased C2S and reduced C3S contents are employed in the production of cements with reduced hydration heat evolution (see section 19), such as moderate heat of hardening cement (corresponding to ASTM Type II cement) and low-heat cement (corresponding to ASTM Type IV cement). To slow down the rate of heat evolution, cements employed for this purpose are usually ground to a relatively low specific surface area. Cements of this type are used in applications in which a reduced release of hydration heat is required, as in the constraction of dams and other bulk concrete structures (Kelham and Moir, 1992 Sone et al, 1992). High-C2S cUnkers, especially those with a reduced C3A content, are also constituents of some oil well cements (see section 27). L0W-C3S clinkers are less suitable for the production of blended cements, owing to the reduced amount of free calcium hydroxide produced in the hydration of such clinkers. 

Sane, T., Fujiyama, O., and Tanimura, M. (1992) Properties of concrete rrsing low heat cement containing a large amount of belite. Semento Konkurito Ronbunshu 46,392-397. 

Nakatsu, K. et al. New low-heat cement with Ca0-Al203-Si02 glass. Ceramic Transactions 4,265. 

Unlike belite eements, sulfobelite cements tend to exhibit a fast initial rate of hydration heat release, owing to a fast hydration of the C4A3 S phase, and do not usually qualify as low-heat cements. 

Calcium aluminate cement does not qualify as low-heat cement either, as its heat of hydration is high (500 k J/kg), and most of it is released within the first few days of hydration. 

Tomisawa, T., Chikada, T., and Nagao, Y. (1993) Properties of super low heat cement incorporating large amounts of ground granulated blast furnace slag of high fineness. American Concrete Institute SP-132, pp. 1385-1399. 

Yoshida, K., and Igarashi, H. (1992) Strength development and heat of hydration of low heat cement, in Proceedings 9th ICCC, New Delhi, Vol. 3, pp. 16-22. 

It has been shown by conduction calorimetry that Type 10 (Type I ASTM) cement containing 25% fly ash exhibits similar behavior to Type 40 (Type IV ASTM) low heat cement containing no fly ash.f l Both these cements have lower heats of hydration compared to pure Type 10, normal Portland cement (Fig. 3). 

Figure 3. Conduction calorimeteric curves of normal portland cement and low heat cement containing fly ash.

The temperature rise in the hardening concrete depends on, among other things, the cement content, and on the chemical composition and fineness of the cement. Thus, there are specific cement types produced with particularly low and slow development of heat - low-heat cements - which are used for casting of heavy concrete structures such as dams. 

Determination of the heat of hydration after 1, 3 or 7 days is made to classify cements into different types, based on their reactivity, and this type of measurement is most important for low-heat cements used in mass concreting. Solution calorimetry according to ASTM C186 (2013) or EN 196-8 (2010) and semiadiabatic calorimetry according to EN 196-9 (2010) have been the preferred techniques for this, but isothermal calorimetry is becoming more and more used. As discussed previously, the different types of... 

Low-heat cement, very low-heat cement Cement with slow hydration rate and related low rate of heat release. Mostly used to avoid the buildup of internal stress and cracking by thermal expansion in large, voluminous structures such as dams. Low-heat release cements can be achieved by coarse grinding of portland cement and/or by using high levels of replacement of clinker by supplementary cementitious materials. 

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