Mortar deterioration

Figure 5. Mortar deterioration due to salt crystallization in masonry. The mortar is more porous than the brick allowing for fast evaporation and concentration of the soluble salts.

Mortar Deterioration. Mortar may decay from the formation of calcium sulfoaluminate (which causes expansion and loss of mortar strength) and by the attack of pollutants in the atmosphere. Portland cement contains tricalcium aluminate, which reacts with sulfates in solution to form calcium sulfoaluminate. Exhaust gases from automobiles contain sulfur dioxide, sulfur trioxide, and nitrous oxides. These oxides react with moisture in the atmosphere to form sulfurous acid, sulfuric acid, and nitric acid, which are the attacking agents. As attack continues over the years, the mortar joints may crack, the surface of the joint may spall off, and the mortar may become softer and more crumbly. 

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). 

Nonhydraulic cements were among the most common of the ancient cements. The relatively high solubilities of portlandite (Ca[OH]2) and gypsum means that they deteriorate rapidly in moist or wet environments. Many decades ago, the Romans used lime-based cements and mortars (cement plus sand) by ramming the wet pastes... 

This reagent may be purchased in the form of small pellets which are easily and quickly crushed in a mortar immediately before addition to the reaction flask (as for example in a Friedel-Crafts reaction, Expt 6.5), and covered with solvent. In these cases the small amount of hydrolysis which occurs during the grinding operation is not unduly harmful to the reaction yield. This pelleted material does unfortunately deteriorate fairly rapidly on reaction with atmospheric moisture on continued opening and closing of the reagent bottle. The material should therefore be carefully inspected before use and if a large amount of powdery white material is present a fresh bottle should be used. 

Corrosion. A more serious effect and one of great economic importance is the corrosive action of acid gases on building materials. Such acids can cause stone surfaces to blister and peel mortar can be reduced to powder. Metals are also damaged by the corrosive action of some pollutants. Another common effect is the deterioration of tires... 

Tetryl forms yellow crystals with a melting point of 132 Celsius—it explodes when heated to 180 Celsius. It is insoluble in water, but soluble in alcohol, benzene, and acetic acid. Solutions of tetryl in solvents should be stored in a dark place, protected from light—as they will slowly deteriorate on standing—normally tetryl is stored dry or moistened with kerosene or water. Solutions of tetryl or even the dry solid upon the skin and teeth causes yellow staining. Tetryl is a very powerful explosive used primarily in detonators as a booster for artillery, mortar, and projectile fuses. Tetryl is a standard military initiating explosive (booster). Tetryl boosters are common in shape charges, mines, mortars, artillery shells, rockets, anti-tank munitions, and missiles. 

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. 

Zinc, dusi, Zn, At. wt. 65.38. Suppliers Fisher (Certif.) min. 97% Mallinckrodt (best grade, AR) 95% min. Merck 90% min. Once a bottle has been opened, the reagent may deteriorate owing to oxidation. Procedures of activation (other than alloy formation) may involve chiefly removal of inert oxide. (1) Wash several times with 5% hydrochloric acid, wash in turn with water, methanol, and ether, and dry. (2) Another, described as a purification 1.2 kg. of zinc dust is stirred with 3 1. of 2% hydrochloric acid for 1 min. The zinc is collected and washed in a beaker with one 3-1. portion of 2% hydrochloric acid, three 3-1. portions of distilled water, two 2-1. portions of 95% ethanol, and with one 2-1. portion of absolute ether. The material is thoroughly dried and any lumps are broken up in a mortar. (3) Stir with 10% hydrochloric acid 2 min., collect, wash with water, then acetone. (4) See Zinc, for Reformatsky. 

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. 

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. 

The section on masonry deterioration focuses on limestone, coquina, sandstone, marble, concrete, brick, and mortar as related to acid deposition effects on structures such as buildings and on cultural resources such as monuments. 

Bricks and mortar (New Haven, CT) are susceptible to deterioration through the action of acid deposition. (Photo by Robert Baboian.)... 

Because they are relatively expensive, epoxy polymers have not been used very widely as binders in PC products. Therefore, epoxy PC is used for special applications, in situations in which the higher cost can easily be justified, such as mortar for industrial flooring to provide physical and chemical resistance, skid-resistant overlays (filled with sand, emery, pumice, quartz) in highways, epoxy plaster for exterior walls (e.g., in exposed aggregate panels), and resurfacing material for deteriorated areas (e.g., in flooring). Epoxy PC reinforced with glass, carbon, or boron fibers is used in the fabrication of translucent panels, boat hulls, and automobile bodies [2,6],... 

Of course, floors in a structure receive the greatest abuse, where deterioration occurs in such areas, epoxy resin systems have been widely used for repairs. Industrial floors are now constructed with initial specifications calling for an epoxy mortar, usually, 1/4 inch in thickness, to provide a diemically and physically resistant surface. Slip-resistant aggregates may be embedded in such epoxy toppings. The same tech-... 

As ordnance deteriorates, it must be disposed of properly. Also, many World War I guns and mortars were replaced over the next two decades, rendering many munitions obsolete, such as the Stokes and Livens mortars. Much World War I small arms ammunition was corrosively primed, rendering it undesirable. Fuses were improved and standardized around 1930, rendering still more ammunition unserviceable. Much of this obsolete ordnance was buried during this time frame and is even more... 

Conroy, P.J. and Oliphant, R. (1991), Deterioration of water quality. The effects arising from the use of factory applied cement mortar linings, WRC Report NDoE 2723-SW. 

For the past seventy years or more, active research and development of polymer-modified mortar and concrete has been conducted around the world, resulting in products which are currently used as popular, important construction materials. To match the technical innovations in the construction industry in recent years, useful polymeric admixtures or polymer-modified mortar and concrete have been developed in advanced countries. There is currently great interest in using polymer-modified mortar and concrete as repair materials for deteriorated reinforced concrete structures. Polymer-modified concrete and mortar are promising construction materials for the future because of the good balance between their performance and cost compared to odier concrete-polymer composites. 

Since the permeability significantly influences the deterioration of concrete, evaluation of water permeability in cracked HPFRCC seans a key factor to describe the durability performance of given materials. Superior impermeability of HPFRCC has been observed by several researchers. Lepech and Li (2005) studied the water permeability of cracked HPFRCC and reinforced mortar specimens. When subjected to identical tensile deformation, the HPFRCC and reinforced mortar specimens exhibited very different cracking patterns and widths. They found that the cracked HPFRCC exhibits nearly the same permeability as sonnd concrete, even when strained in tension to several percent (Figure 6.8). Homma et al. (2009) also evaluated the water permeability of cracked... 

Wide-ranging use of repair, restoration or rehabilitation systems using polymer-modified paste, mortar and concrete for deteriorated reinforced concrete structures [72-73]... 

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