Strength development slag cements

In order to improve the properties of slag cements the finer grinding should be used as compared with the Portland cements of the same strength. The significant amendment of strength development can be obtained by the use of grinding aids, particularly of triethanoloarrrine [24]. 

Slag cements 32.5N should not be used when eonereting proeeed at low tem-peratirres, particularly below 5 °C, beeaitse of very slow strength development, as compared to Portland eement concrete. This is related also to the Portland cement class 32.5 with mineral additions (Table 7.2) [83]. 

The three component cements with fly ash addition, apart from granulated blastfurnace slag CEM II/B-(S-V), have the advantageous properties first of all fairly good strength development. 

Xi, Y., Siemer, D.D., and Scheetz, B.E. (1997) Strength development, hydration reaction and pore stmcture of autoclaved slag cement with added silica fume. Cement and Concrete Research 27,75-82. 

Fentiman, C.H. et al. (1990) The effect of curing conditions on the hydration and strength development inFondu slag, m. Proceedings International Symposium on Calcium Aluminate Cements, London, p. 272. 

Figure 4.1 Development of strength of different cement-admixture blends pure ordinary Portland cement (OPC), with 10% silica fume (MS), 30% fly ash (FA) and 65% ground granulated blast-furnace slag (GGBS), with different values of w/b, after Swamy and Laiw (1995).

Fig. 24 Strength development of various cements (from Woods/ Starke/Steinour, 1976) 1 = Portland cement with 70% alite and 10% belite, 2 = Portland blastfurnace cement with 60% slag, 3 = Portland cement with 30% alite and 50% belite...

The role of individual supplementary cementing materials and additives has been described in the previous sections. The effect of these materials, viz., silica fume, slags, rice husk ash, fly ash, metakaolinite, or natural pozzolans on the properties of concrete such as workability, setting, rate of hydration, strength development, heat, durability, etc., is known to... 

Cook, D. J., Hinczak, 1., and Cao, H. T., Heat of Hydration, Strength and Morphological Development in Blast Furnace Slag/Cement Blends, Int. Workshop on Granulated Blast Furnace Slag Conor., Toronto, pp. 67-78 (1987)... 

Tashiro, T., and Yoshimoto, T., Effect of Sodium Compounds on the Strength and Microstructural Development of Blast Furnace Slag Cement... 

An important development in concrete mix design has been the addition of so-called supplementary cementitious materials. Two classifications apply to these compoimds Pozzolans, such as fly ash and silica fume, react with the cement hydration products, notably calcium hydroxide hydraulic materials, such as granulated blast furnace slag, undergo direct hydration reactions. As these materials are of lower cost than conventional cement and essentially represent environmental waste products, there are obvious incentives for blending them in concrete mixes. As pointed out by Hansson, these materials can improve the strength and durability of concrete, with the important proviso that the concrete is cured adequately. 

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