Quick setting cements

Other types of cement than those of Table 1.3 are available for special uses. These are for instance low heat cements to be used when low heat of hydration is desired such as in massive structures, sulfate-resisting cements to be used to increase the resistance of concrete to sulfate attack, expansive cements, quick setting cements, white or coloured cements, etc. [2]. 

The hydration mechanism described accounts for the main features of the European Roman cements— quick setting, combined with high initial and long-term strength. These features made them favored materials for economic and easy manufacture of the renders and stuccos for the exterior of buildings in 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]. 

Acid-base (AB) cements have been known since the mid 19th century. They are formed by the interaction of an acid and a base, a reaction which yields a cementitious salt hydrogel (Wilson, 1978) and offers an alternative route to that of polymerization for the formation of macro-molecular materials. They are quick-setting materials, some of which have unusual properties for cements, such as adhesion and translucency. They find diverse applications, ranging from the biomedical to the industrial. 

Semler, C. E. (1976). A quick-setting wollastonite phosphate cement. American Ceramic Society Bulletin, 55, 983-8. 

These cements are defined as materials that are formed by mixing a basic powder with an acidic liquid, and offer an alternative to polymerization as a method for forming solid substances. They are quick-setting materials, with unusual properties, which find diverse applications as biomaterials and in industry. 

Zinc oxide has a wide range of uses apart from its use as an artist s pigment where it provides a more translucent white than flake white or titanium white. It is used in cosmetics, driers, quick-setting cements with syrupy phosphoric acid or zinc chloride in dental cement in the manufacture of opaque glass, enamels, car tyres, white glue, matches, white printing inks and porcelain. The photophysics of zinc oxide has been reviewed.1468 ... 

The soluble sulfate versus time curve for the cement containing the natural anhydrite is radically changed when CLS is present [130, 131]. The rate of solution of natural anhydrite, which is much slower than that of gypsum or calcium sulfate hemihydrate, is further retarded in the presence of chemical admixtures, which leads to a sulfate-starved system in the concrete, often producing rapid set and an increase in rate of concrete slump loss (Fig. 7.42). Apparently the adsorption of the lignosulfonate by the natural anhydride plus the rapid reaction between the soluble SO and the tricalcium aluminate keeps the SO level near zero concentration for the first 10-20 min causing rapid stiffening and quick set (approximately 15 min). It is also reported that chemical... 

C.E. Semler, A quick-setting wollastonite phosphate cement, Am. Ceram. Soc. Bull., 55 (1976) 983-988. M.S. Ter-Grigorian, V.V. Beriya, E.N. Zedginidze, and M.M. Sychev, Problem of the setting of serpentinite-phosphate cement, Chem. Abstr., 101 (1984), No. 156469. 

Table 13.2 lists phosphate cements developed using C S and C A as the starter powders. Semler [4] used a naturally occurring mineral, wollastonite (C S), as the source of Ca(aq) " and reacted it with H3PO4 solution that was buffered with A1 and Zn to produce a calcium phosphate quick-setting cement that hardened within 3-8 min and provided... 

Regrout with quick setting cement grout, using new vertical grout holes on upstream side of curtain. Checking continuity of curtain is necessary. 

The reaction between hard-burned MgO, water, and potassium dihydrogen phosphate produces a quick setting cementitious mass, KMgP04-6H20. This cement system was originally developed at Argonne National Laboratory for the stabilization and encapsulation of hazardous and radioactive wastes (Wagh et al., 1998). 

As shown in Fig. 225, an unglazed porcelain boat is charged with 20 g. of very pure silicon and placed in a porcelain or quartz tube (30-40 mm. diameter, 800 mm. lot ), placed in a Globar tubular furnace. The boat is pushed to the hottest part of the furnace. The temperature should be about 1150°C at this point. The ends of the tube, which extend beyond the furnace, are wound with lead cooling coils and are closed with well-seated rubber stoppers c and d. The stoppers are painted with quick-setting chlorinated rubber cement to ensure a better seal. The flask o, which contains SiBr 4, is first cooled to at least -80°C and Is then very slowly... 

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