Brick deterioration

Nitric and hydrochloric acid were found to be even more aggressive to glass than sulfuric acid (15). It could therefore be expected that nitrogen oxides would be more aggressive than sulfur oxides with respect to brick deterioration. 

Figure 6. Brick deterioration due to salt crystallization in masonry. In this case the bricks are more porous than the mortar and the salts will accumulate in them leading to their deterioration. Considerable variation in the degree of deterioration is evident.

The temperature of initial liquid formation in basic refractories is important because the mechanical properties of the brick deteriorate once liquid begins to form. 

Brick lining (40-65 mm thick) is used for reducing the temperature at the membrane. This protects the membrane from deteriorating with free access of the process liquors and prevents its erosion and other mechanical damage [51,52]. 

Modem building materials have been developed to reduce the rates of environmental deterioration. However, stone, brick, and masonry constitute the stmcture of many of the historic buildings and statues that make up our cultural heritage. The reaction of sulphur-based solutions on the surfaces and... 

Damage to houses, buildings and other structures caused by the deterioration of brick, mortar, and concrete, resulting from saline water crystallizing in brickwork (e.g.. Cole and Ganther 1996). 

Masonry products have been widely used in the construction industry and include building materials such as cementious materials, concrete, brick, tile, stone, grout, and like substances. Driveways, garage flooring, concrete block, brick fronts, fireplaces, fireplace hearths, as well as tiled floor, wall and counter top surfaces are exemplary applications. Masonry surfaces are porous and if left unprotected can deteriorate from exposure to water and they can become discolored. For example, water penetration can cause spalling or lead to discoloration via microbial growth. Tiles and grouts employed in homes come in contact with various foods and liquids, e.g., fruit juice, coffee, oils, ketchup, mustard, etc. that can cause discoloration. 

Cured concrete can be bonded to cured concrete, as in the installation of precast buttons to a highway surface. Steel bridge railings can also be bonded to the concrete surface of a bridge sidewalk. In the case of deteriorated concrete, the adhesive can be used to rebuild the structure to its former line and grade. Epoxy adhesives are also commonly used on other roadway materials, such as asphalt and brick however, the predominant application is concrete substrates. The most frequent combinations of substrates that are bonded with adhesives in this market segment are... 

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... 

Mortar joints between the brick will recede due to wear and adverse chemical and thermal effects. This is normally a relatively slow, progressive phenomenon. The condition is remedied by raking any loose or deteriorated mortar from the joint and repointing with furan mortar. This is a maintenance procedure which will be done many times during the lining life. 

Concrete floor areas in a pulp and paper mill are frequently lined to prevent deterioration of the concrete. These linings can consist of red shale brick, quarry tile, or an aggregate filled resin (referred to as a monolithic floor lining). Floor linings are primarily used in areas exposed to very aggressive chemicals such as in the bleach plant and paper mill. 

Maintenance of a floor lining usually involves repointing of deteriorated and receded joints, replacement of broken brick or tile, and removal and replacement of loose or disbonded brick or tile or monolithic. If proper maintenance procedures are not followed, the lining can be severely undercut and disbonded and the concrete substrate attacked. 

Steel chimneys have the advantages of lightness and strength, but since they are better conductors of heat, must be lined with brick for heights over 75 ft. except in forced-draft installations. They must be carefully inspected and painted from time to time, as they are subject to deterioration by corrosion. 

Deterioration of Brick Masonry Caused by Acid Rain... 

Several different mechanisms are operant in the deterioration of brick masonry through the action of acid rain. The bricks are susceptible to acid rain through the selective dissolution of their glassy phase. The mortar is affected mainly by the reaction of its calcareous components. The soluble salts resulting from these reactions, in solution with rain water or condensed moisture, will migrate through the porous matrix of the masonry. In the places where the water evaporates the salts will be deposited. 

Deterioration of brick masonry is a problem that has worried man ever since the first brick wall was constructed. It is interesting to remember that already by the first century A.D. bricks were considered more resistant to deterioration than marble., which had an estimated useful lifetime of about 80 years ( ). Today, the problem is still in study, if only due to the increased number of masonry structures. 

The deterioration of brick masonry is a complex problem, in which two variable ingredients, brick and mortar, make up the whole. As each component can have a large variation in composition and structure, when both are combined in a wall, the number of variations that result is given by all the possible combinations of the two components. 

This type of deterioration was observed in the glassy matrix of a brick exposed to concentrated sulfuric acid where the leached layer crumbled away exposing the more acid resistant minerals (12). Sulfuric acid solutions formed from atmospheric constituents were estimated to increase tenfold the rate of attack on bricks (13). Gaseous SO2 in a water vapour saturated atmosphere was found to... 

Figure 1. Surface of a 16th century Venetian brick eroded by rain water run-off. A highly-vitrified nodule resists deterioration better than the less vitrified matrix.

Figure 2. SEM photomicrograph of an eroded surface of a 12th century brick, "altinella, from Venice. The quartz grains are exposed as the more susceptible matrix deteriorates faster.

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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