High alumina cement strength

Portland and high alumina cements do nol withstand acids but are resistant lo bases. High alumina cemcnl attains its maximum strength mote quickly than Portland, and has the extra advantage that it withstands solutions of sulfates. 

The strength of latex-modified systems is affected to a lesser extent by the type of cement, except when high-alumina cement is used as shown in Fig. 4.16.126]... 

In Chapter 2 we mentioned cement and the reactions that occur during the setting and hardening of this material. There is a class of cements known as calcium aluminate cements (CACs) or high-alumina cements (HACs). These ceramics are not used as widely as Portland cement, but their attraction is the rapid hardening reactions. In 1 day CAC achieves the same strength as Portland cement achieves in a month. 

Midgley, H.G. (1980) The relationship between cement clinker composition and strength recovery of hydrating high alumina cement during conversion, in Proceedings 7th ICCC, Paris, Vol. 3, pp. V68-70. 

Phosphate-bonded high-alumina cement is reported to be useful for special purposes [28]. Increase in strength and heat resistance is claimed with P2O5 addition [29]. Special cements based on calcium aluminate and sodium polyphosphate, (NaP03> , which set and harden at 50 300°C, have recently been developed for use in geothermal wells [30]. 

The particular temperatures at which peaks are observed can be used for the identification of components in a mixture, and the size of a particular peak can be used for quantitative evaluation. Examples include the determination of quartz in clays and analysis of the constituents of polymer blends, both of which would be difficult to achieve by other means. DTA has been used to determine the presence and degree of conversion of high-alumina cement concrete (HAC), a material subject to severe loss of strength under certain atmospheric conditions due to solid-state reactions in the cement matrix. Figure 9 shows a DTA curve for partially converted HAC together with the way the data are used for a conversion measurement. 

Probably only large pores have an important detrimental influence on composite strength. Based on tests on high alumina cement specimens published by Murat and Bachiorrini (1987), it has been shown that a clear correlation existed only when porosity with pores larger than 1 pm was taken into acconnt. 

The latex-modified mortars using high-alumina cement exhibit a strength 1.5 to 2 times higher than that of the mortars using other cements. This is due to a difference in the structure formation at the initial stage of setting. 

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