Expansive cements sulfobelitic

Sulfobelite cements may perform either as non-expansive high early strength cements, or as expansive cements, depending on the proportion of the individual phases in the cUnker and the amount of interground calcium sulfate. 

The ettringite that is formed exhibits distinet eementing properties, but may cause expansion at a different rate and to a different degree, depending on the Al source involved in the reaction. Cements that eontain significant amounts of calcium sulfate include expansive cements (see seetion 21), regulated set cement (see section 5.2), supersulfated cement (see section 8.4), sulfobelite cement (see section 4.2), and sulfoalite cement (see section 4.3). Limited amounts of ealeium sulfate are also present in Portland cement (see section 2) and blended eements (see section 7). 

The development of strength and the extent of expansion will depend on the composition of the cement and the proportions of the phases involved. Within reasonable limits and at appropriate calcium sulfate contents the early strength will increase with increasing amounts of the sulfoaluminate phase in the cement and— to a lesser extent— with increasing content of the ferrite phase. However, the belite phase will affect maiidy the final strength of the cement. Table 4.2 shows the effect of cement composition on the compressive strength development of a series of sulfobelite cements. 

Figure 4.1 Effect of gypsum intergroimd with a sulfobelitic clinker on the expansion of the resultant cement. SOj in clinker=10.0 wt%. Source Wang et al. (1992a)...

Non-expansive sulfobelite cements exhibit good chemical resistance in contact with... 

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