Strength slag cement

Notation of cement indicates the cement type (Table 1.3) and the strength class (Table 1.4). For instance, CEM II/A-S 42.5N indicates Portland-slag cement with addition of blast furnace slag in the range of 6-20% and strength class 42.5 with normal early strength. 

When a high early strength is required, such as for post-tensioned structures or pre-tensioned precast elements, Portland cement with a strength class of 52.5 may be used. Blended cements are usually not suitable because of the slow rate of hydration, with the exception of Portland-silica fume cement and special (fast) slag cements. 

Additionally the strength of cement with air entraining agent, but without mineral addition is as for J(SM). Clinker can be replaced by Portland or slag cement. 

Fig. 7.3 The mean strength of slag cement mortar as a function of Al Oj content in slag 75% slag with specific surface area 3850 cmVg (according to [1]) ...

The other coefBdent of slag the hydrauhc activity, thus Unked with the strength of slag cements, were formulated too. Two examples are presented below [33, 34] ... 

Fig. 7.8 Flexural strength of mortar from slag cement (SC) with the fineness 350 m /kg (SC-2) and 630 m /kg (SC-1) respectively, in comparison to the strength of Portland cement mortar (PC) (according to [72])...

There is an opinion that the early strength of cement, after 3 or even 7 days depends primarily on the properties of cement clinker and its fineness, even in the case of high slag content, about 50% [36]. On the other side, at high slag content, over 75 %, this is the slag, which contributes to the early strength of cement and clinker only after 28 days [70],... 

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]. 

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

Portland-slag cements may be employed in most applications in which plain Portland cement is also used, as long as a high short-term strength is not required. The main areas of their use are applications in which a high corrosion resistance or a slow hydration heat liberation of the binder are required. 

Figure 23.4 Compressive strengths of pastes made with different cements and exposed to increasing temperatures. OPC, ordinary Portland cement BFSC=blast furnace slag cement with 50% of granulated blast fiimace slag PFA, fly ash cement with 25% of pulverized fly ash ...

Puertas, F., Martinez-Ramirez, S., Alonso, S. Vazquez, T. (2000). Alkali-activated fly ash/slag cements Strength behaviour and hydration products, Cent Conor Res, 30 (10), 1625-1632. 

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