Acid resistant masonry

Concrete is ideally suited to being used as a supporting substrate for acid resistant masonry. It has a coefficient of thermal expansion closest to that of brickwork (5.3 X 10 as against 3.8 - 4.2 X 10" for most shale and fireclay brick— while steel falls into the range of 6.8 to 7 X 10" ). Concrete also has the ability to absorb blows and vibration without transmitting them to the masonry lining. 

Acid Brick Acid brick, also called acid resistant or acid proof brick (covered by ASTM C279), are of two major types (1) Red shale, the predominant brick in CRM construction and (2) Fireclay, another common brick in CRM applications. These two acid brick are the most widely used masonry units in CRM structures and linings, including floors, trenches, sumps, vessels and chimney... 

The use of silica brick in chemical-resistant masonry is limited, because of high cost, to applications requiring a high degree of chemical resistance where traditional acid brick cannot be used, such as concentrated phosphoric acid free of fluorine. Silica brick, however, cannot be used in strong alkaline exposures or any concentrations of hydrofluoric acid. As with acid brick, its main function is to provide a barrier to abrasion and to protect other membranes or structures from chemical attack. Because brick porosity may be as high as 16%, silica brick is backed by an impermeable material and a support structure. 

The integrity of any lining system depends not only on the quality of the material used but also on the quality of the actual installation. Therefore, an experienced specialty contractor is required to ensure a high-quality installation. Typically, a masonry contractor experienced in the special handling of acid-resistant brickwork construction will have the expertise to follow the block supplier s application instructions. 

Granite is most commonly used in applications where physical stability, durability and strength in a mildly acid environment are required. Historical uses of granite as a chemically resistant masonry include its use as flooring in places where "oil of vitriol" (sulfuric acid) was made. In the nineteenth century, granite blocks hollowed out to form tubs were employed by steel wire companies to hold dilute HCI baths for pickling off mill scale from the wire. Some of these tubs are still in use today. 

The properties that make granite an attractive chemically resistant masonry are its naturally low permeability, thermal expansion (in generally the same range as that of "acid-brick"), high strength and the insolubility of its component minerals in dilute HCI and H2SO4. Hydrofluoric acid is the only acid in which quartz, feldspar and mica, the major constituents of most industrial granites, are easily soluble. Contact with HF must therefore be avoided. 

Strength. A structure composed of "acid brick" or block in any other chemically-resistant masonry unit cannot be reinforced. Although it has good compressive strength, it is weak in tension and shear, and depends for its integrity on the bond of the mortar to the masonry face. 

Brittleness. Structures composed of "acid brick," block or other chemically-resistant masonry units cannot be flexed or bent (which would cause torsion or shear of joints). They are all somewhat brittle, and if the supporting structure around them bends, they are certain to break. For the same reason, they cannot accept excessive vibration. 

As stated earlier, acid resistant brick masonry (ARBM) has been a long standing workhorse in the industry. While the corbel supported brick liner has likely seen its last days with the passing of the hot, dry chimney, independent brick liners remain those most commonly specified today. 

When a failure occurs in an alloy vessel containing chemicals, the owner starts to investigate to learn if the correct alloy was used, if the designer mal-designed it, or if the fabricator made some error in assembling it. However, when a failure occurs in an "acid brick"-or other chemically resistant masonry-structure, the customer often abandons the concept without investigation, with a comment such as "we tried it and it didn t work." There is always a reason for a failure and if you are able to analyze the failure so as to learn the source of the trouble, there is no reason why such failure cannot be prevented in the future. 

McDowell, D.W., Jr. and Sheppard, W.L., Jr., Using Acid-Proof Brick and Mortar in Masonry Construction and Picking Nonmetailic Construction Materiaisto Resist Mineral Acid Attack,Plant Eng. (2/19/76 3/18/76). 

Red shale and fireclay acid brick are probably the most widely used masonry materials in chemically-resistant systems. Many scrubbers, trenches, floors. 

From the above, it would appear that the carbon brick is not greatly different in abrasion resistance from the fireclay brick. Where construction requires masonry internals, such as support plates and packed scrubbers, yet the exposures include hydrofluoric acid or strong alkalis, beams, stringers and plates... 

Use Wetting agent, furan polymers, corrosion-resistant sealants and cements, foundry cores, modified urea-formaldehyde polymers, penetrant, solvent for dyes and resins, flavoring. The polymer is used as a mortar for bonding acid-proof brick and chemical masonry. 

Brick masonry, even though susceptible to acid rain attack, owes its deterioration mainly to the crystallization of the soluble salts produced in that reaction or from other, more important, sources of soluble salts the inherent vice in bricks and ground water salts. The capability of a given masonry structure to resist deterioration will be directly related to its resistance to water penetration, which is the main single agent responsible for the decay process by salt crystallization. 

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