Silicate mortars

Wilding, C. R. The Performance of Cement Based Systems. Cem. Res. 1992, 22, 299. Wilk, C. M. Stabilization of Heavy Metals with Portland Cement Research Synopsis Portland Cement Association Report IS007 PC A Skokie, IL, 1997. Young, J. F. Berger, R. L. Breese, J. Accelerated Curing of Compacted Calcium Silicate Mortars on Exposure to C02. J. Am. Chem. Soc. 1974, 57, 394—397. 

Silica Mortars Silica mortar is a strictly acid and heat resistant material, handling all acids except HF and acidic fluorides at pH 0-7 and thermally stable up to 2000°F. A relatively recent self-curing silica mortar contains only borosili-cate glass powder, silica sol and crushed silica with no metallic constituents. This avoids both the sulfation-hydration reaction of the sodium silicates and the alum formation problems of the potassium silicates. Like the silicate mortars, silica mortars also resist organic chemicals. 

A CRM lined S30403 (Type 304L) stainless steel vessel with silicate mortar joints is successfully used for boiling 30% nitric acid containing an abrasive slurry. Stainless steel is used because there is no economically satisfactory membrane to protect the steel shell in such service and an unlined stainless steel shell could not withstand the abrasive slurry. 

Within the last few years, there have been several instances in which independent brick liners have experienced problems in resisting the effects of wet flue gases. In certain instances the problems have been due to actual deterioration of mortar and/or brick which were subjected to chemical attack by certain constituents of either the flue gas itself or carry over" reagents from the flue gas desulfurization system. In general, the commonly used silicate mortars for chimneys are quite resistant to a wide range of acids and actually thrive in a wet acid environment. However, certain acids, such as hydrofluoric acid, and most... 

Silicate mortars, however, will not be injured by storage in warm locations, with the possible exception of a few with limited shelf life, where it is possible that shelf life may be shortened. But if the liquid component (sodium or potassium silicate) is frozen, the fluid mixture (a colloid) will "break" and the silicate will come out of solution and coat itself on the inside of the metal containers. If this happens, the mortar will not function until the silicate is redissolved— mixed back with solutions using a power-stirring device such as a "Lightning Mixer."... 

Figure 52-13 Showing the effect of trace amounts of acid fiuorides in the acid washing the inside of the tower in this case, 750 parts per million. This damage occurred in less than 6 months, (a) Top picture shows loss of silicate mortar, (b) Underside of a brick on the floor. Center of the picture displays original texture of the surface (protected by mortar), (c) Right-hand picture shows surface exposed to scrubbing liquid containing the fluorides.

Vitrex. [Atlas Minerals Chem.] Silicate mortar. 

The fall of the Roman Empire was to lead to a dramatic loss of Collegia skills. Vitruvius described how the Romans had made extensive use of cement and even hydraulic lime and silicate mortars that could set underwater." The magnificent dome of the Pantheon built in llOCE... 

There are basically three types of mortars in use in CRM. They are thermoset resin based mortars (such as furan, phenolic, epoxy, polyester), silicate mortars, and sulfur mortars. 

Because of its structure and composition the cellular glass is an excellent insulating material for the inside hot surfaces of process equipment. It has a weight of only 12 Ib/ft (0.19 g/cm ). For example, a process vessel handling 65% sulfuric acid at 350°F/177°C would have an outer shell of mild steel, an inner membrane of sheet rubber or vinyl, and an inner insulation of four 4 in. courses (layers) of acid brick laid up with a silicate mortar. As a result of the extra thickness of the lining, the outer steel walls and vessel supports would have to be heavy. 

The inorganic mortars are the original mortars. They are commonly referred to as acid proof mortars, primarily because they are limited in application to a maximum pH of 7. They cannot be used in alkaline or alternate alkaline-acid service. There are two general types of inorganic mortars the hot pour sulfur and the ambiently mixed and applied silicate mortars. 

Sodium silicate mortars are available as either two component systems, which consist of the liquid sodium solution and the filler powder containing settling agents and selected aggregates, or they may be a one part system in powder form to be mixed with water when used. There are some differences in the chemical resistance between the two types. The differences in the chemical resistance of the two types of mortars are shown in Table 7.7. Sodium silicate mortars are useful in the pH range of 0-6, except where sulfuric acid exposures exist in the vapor phase, wet-dry exposures, or in concentrations above 93%. 

Potassium silicate mortars are preferable to sodium silicate mortars. They have better workability because of their smoothness and lack of tackiness. They do... 

Table 7.7 Corrosion Resistance of Sodium Silicate Mortars...

New setting agents have been developed that improve the water resistance of the sodium silicate mortars making them suitable for use with dilute as well as concentrated acids (see Table 10.3 for their resistance to normal atmospheric corrosion). 

H.E.S. and HB Mortars differ from other siliceous, silicate, or silica mortars in resisting exposures between pH 0.0 and pH 8.0 with the exception of acid fluorides and HF acid. In addition, they can be used in glycol acetate, potassium sulfate or persulfate, sodium sulfide and trisodium phosphate, all of which will damage other siliceous mortars. 

IN 0 BOND C is a high-purity quartz colloidal silicate mortar for use with all sizes of acid brick and is especially suited for stack or chimney linings as in sewage treatment operations and other, and as a mortar for process linings. 

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