Furan mortars

In phosphoric acid production plants, both red shale and fireclay brick have excellent resistance to all concentrations of phosphoric acid at temperatures up to 250°F, provided the acid contains no HF. If HF is present in the phosphoric acid, carbon brick construction must be used. As a rough rule-of-thumb, HF levels above 50 ppm in phosphoric acid require tank linings of carbon brick bonded and jointed with a carbon (or barytes) filled furan mortar over a suitable membrane to match the steel or concrete substrate structure. 

Furan Mortars Furans have the broadest range of resistance to both acid and alkali (pH 0-14) and temperatures of all the resin mortars. Furan mortars can accept temperatures up to 350°-360°F. Modified furans are available that can withstand continuous temperatures of up to 425°F and intermittent temperatures to 475°F. Unlike the other mortar materials, furans have excellent resistance to strong alkalies as well as non-oxidizing acids and many organic chemicals. However, furan mortars are attacked by some organic solvents such as aniline. Furans are available with silica, carbon or barytes fillers, the filler choice depending upon the environmental conditions. 

Another seven days cure is recommended at this point, if this is possible. However, if down time is vital, this may be reduced to an absolute minimum of three days at 70°F. After the cure time has elapsed, a final overall application of the furan mortar, V32" to Vs" thick, is trowelled to as uniform a surface as possible. 

In chemical plants where corrosive, wet conditions are anticipated, walls are protected with membranes and brick veneers in the same manner as floors. Alternatively, a divider wall between two rooms, or one that is to support a roof or other load, may be built entirely of "acid brick" and mortar. A different, more attractive system, is usually followed in food plants such as dairies, often employing glazed tile or block. The latter are laid just as are regular cement block, except that the face joints are left void to a depth of % in. or more, or raked back to that depth before the joints set up. After cure, the surfaces of the joint are cleaned usually with dilute hydrochloric acid, and the joints pointed full with a furan mortar. See Drawing 14 to see how this kind of a wall is mated to an "acid brick" floor and membrane. 

Figure 45-4 Examples of floors laid with high bond, high strength furan mortar in which cure shrinkage of the mortar has caused the brick to break. The cracks so created have been filled with expansion joint sealant. See Chapter 25.

If the shaft of the pipe, or even a joint, is cracked or otherwise damaged, and the line is leaking through the crack, the line can often be saved, or at least kept in service for a considerable length of time by "armoring" it with glass fabric and furan mortar. 

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. 

These vessels are operated under extreme chemical and high temperature conditions. They are, therefore, usually brick lined. The lining consists of a polyvinyl chloride sheet membrane applied to the steel shell with an acid brick lining set in furan mortar installed over the membrane. The vessel is occasionally exposed to a caustic solution for cleaning and, therefore, a partial carbon brick lining may be installed in the lower wall area and floor. These lower areas of the vessel are normally where the most maintenance is required. Eroded mortar joints may need repointing and softened and eroded brick may need to be replaced. 

Some mortars are heat sensitive. The speed of set of furan mortars in particular, is much accelerated by heat, so that "open time" can be reduced to 10 minutes at 85° to 90°F. The effects of temperature on setting speeds of other resins are less extreme, but the contractor will have more time to use up his mix at a 60° to 70°F material temperature. Phenolic mortars must be stored prior to use at temperatures of 60°F or lower. If they are left in areas where they may be overheated, they can be ruined in a short time or so badly affected as to be unusable. There is a case on record of phenolic mortars being delivered to a site in Texas late on Friday, and left on the loading dock, resulting in materials which were totally unusable by 7 A.M. on Monday morning when the construction crew arrived. On the other hand, no serious damage will result if the components of resin mortars are subjected to temperatures below freezing. 

However, until recently, the principal application of polyurethanes has been as in situ-polymerized rigid and flexible foams used for insulation and cushioning, respectively.— — Unlike the phenolic, urea and furan mortars, in which the high polymer formation is the result of the chain extension and crosslinking of a prepolymer, the final polyurethane product is the result of a reaction between hydroxyl and isocyanate groups as shown by the following equation ... 

Bricklayer s Method. Acid-resistant brick linings are used where immersion in highly corrosive chemicals is involved or where severe thermal shock conditions exist. Furan resins have been used for years for such applications. As with the furan grouts previously discussed, a number of companies manufacture and market furan mortar systems for acid-resistant brick linings. Most, if not all, of these companies also install the complete lining system. 

Furan mortar is the most commonly used mortar in the chemical process industry. It is a two-component system containing a liquid binder and a powder that is mixed in a mortar box to produce a material of trowelable consistency. Furan mortar is suitable for a wide range of corrosive service conditions including various concentrations of acids and alkalies at temperatures up to 170°C. It is note recommended for strongly oxidizing services. 

The furan mortars are resistant to most nonoxidizing organic and inorganic acids, alkalies, salts, oils, greases, and solvents to temperatures of 360°F/182 C. Fillers... 

Furan mortars and grouts are formulated using either 100% carbon or part carbon/silica fillers. Although not normally used as a monolithic surfacing, they are used to produce furan polymer concrete. Either formulation is satisfactory to resist normal atmospheric pollution but more aggressive pollutants might require the use of 100% carbon filler. Furan grouts normally are filled with only 100% carbon filler. 

Corrosion tests have been conducted on 1 inch x 2 inch furan polymer concrete test cylinders made with Quaker s QO FA-RoK resin/catalyst system by totally immersing them in several key media at 1 SOT for one year. Results of these tests indicate that furan polymer concrete should be suitable for use in environments that have been serviced for many years by furan mortars and furan FRP equipment. 

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