Cement high-alumina

Concrete is a particulate composite of stone and sand, held together by an adhesive. The adhesive is usually a cement paste (used also as an adhesive to join bricks or stones), but asphalt or even polymers can be used to give special concretes. In this chapter we examine three cement pastes the primitive pozzolana the widespread Portland cement and the newer, and somewhat discredited, high-alumina cement. And we consider the properties of the principal cement-based composite, concrete. The chemistry will be unfamiliar, but it is not difficult. The properties are exactly those expected of a ceramic containing a high density of flaws. 

High-alumina cement is fundamentally different from Portland cement. As its name suggests, it consists mainly of CA, with very little C2S or C3S. Its attraction is its high hardening rate it achieves in a day what Portland cement achieves in a month. The... 

High-alumina cement is very quick setting, but its acid resistance is only slightly better than Portland cement, and it is rapidly attacked by alkalis. Super-sulfated cement is used for liquors high in sulfates. It is resistant to acidic conditions down to a pH of 3.5 and has alkali resistance similar to Portland cement [50]. 

Little information is available about the corrosion of metals in concrete, although it seems likely that all Portland cements, slag cement and high-alumina cement behave similarly Concrete provides an alkaline environment and, under damp conditions, the metals behave generally as would be expected e.g. zinc, aluminium and lead will react, copper is unaffected, while iron is passivated by concrete. 

High-alumina cement is a rapid-hardening cement made from bauxite and limestone. It is comparatively resistant to chemical attack. Milling retards the setting of aluminous cement [1582]. On the other hand, setting accelerators such as lithium carbonate increase their effect by this treatment. 

Compositions of high-alumina cement containing quartz or glass, calcium carbonate, microsilica, carbon black, iron oxide red mud or screened fly ash, and styrene-butadiene latex have been described [141,1803,1804]. 

M. Michaux. Controlling setting in a high-alumina cement. Patent WO 9933763, 1999. 

A. N. Scian, Lopez. J. M. Porto, and E. Pereira. Mechanochemical activation of high alumina cements— hydration behavior Pt 1. Cement Concrete Res, 21(l) 51-60, January 1991. 

I cement, high-alumina cement, CaS04.2H20, Ca(OH)2 and CaO [75]. 

Subsequent reaction of the monosulfate with gypsum produces acicular crystals of ettringite. Monosulfate apparently does not contribute to expansion, whereas the formation of ettringite involves expansion. A recently issued patent [75] covers the use of prehydrated high-alumina cement (H-HAC), lime and gypsum mixtures. Particle type, size, thickness of protective coating, and presence of moisture determine the rate and extent of expansion [Fig. 6.11]. 

Fig. 6.11 Comparison of expansion for admixture containing coarse and fine grinds of hydrated high alumina cement (courtesy NRC).

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. 

Risch A, Pollmann H, Ecker M (1997) Application of Portland cement and high alumina cement for immobilization/solidification of a waste model composition. Proceedings of the 10th ICCC, Goteborg, Sweden, vol. 4,4iv044,8 pp... 

Calcium aluminate cements have also been termed aluminous or high-alumina cements, but the former term is less specific and the latter is more appropriately used for the white cements high in AljO, mentioned above. The cements described here are those manufactured in France and the UK. Those made elsewhere are similar in essential respects. 

BI28 Building Research Establishment, High alumina cement concrete in buildings (CP 34/75) , in Practical Studies from the Building Research Establishment, Vol. I, Concrete, p. 228, Construction Press, Lancaster, UK (1978). 

R47 Robson. T. D. High-Alumina Cements and Concretes, 263 pp.. Conlraelors Record Ltd. London and John Wiley and Sons Inc., New York (1962). 

Yakerson V.I., Golosman E.Z., Efremov V.N. Preparation and properties of the adsorbent and support on the basis of calcium dialuminate, a component of high-alumina cement. Kinetika i Kataliz 1994 35 626-30. 

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