Masonry units

Masonry cements (80) are cements for use in mortars for masonry constmction. They are formulated to yield easily workable mortars and contain special additives that reduce the loss of water from the mortar to the porous masonry units. 

Mortars are cements used for bonding together masonry units, such as stones or bricks. When a cement is used to conceal masonry, as a more or less smooth covering on walls, for example, it is referred to as plaster. A very fine plaster, known as stucco, is made of very thin sand or finely comminuted marble. Freshly prepared plasters and stuccos are spread on consolidated masonry to form more or less uniform and smooth layers stucco also provides a smooth and often flat outer coating. 

For facilities susceptible to nitrocellulose, single base and multibase dusts, the same details could be used with the addition of alternate basic construction types. Six types of construction were chosen which included wood frame, concrete masonry units, reinforced concrete, modified preengineered buildings, fiberglass reinforced plastic and sandwich panels. These were chosen for development of architectural details similar to those mentioned above for nitroglycerin facilities except troweled-on conductive floor lining was to be used instead of lead. 

Hollow masonry units should conform to ASTM C90, Grade N. Joint reinforcing should meet the requirements of ASTM A82 with a minimum yield stress of 70 ksi (483 MPa) and a minimum ultimate strength of 80 ksi (552 MPa). Grade 60 bars should be used for primary reinforcing. 

Many petrochemical structures have concrete masonry unit (CMU) walls with little or no steel reinforcement. This type of construction lacks ductility and has relativity low resistance to blast loads. 

Concrete masonry unit (CMU) construction is widely used (Figure 6). It can prevent buildup of contaminants when finished with an epoxy or other smooth, chemical-resistant coating. Where retrofit is not a regular practice, the strength of concrete block and its long life recommend it. 

To quote the editor CRM may be defined as "a structure composed of non-metallic, chemically inert masonry units such as brick, stone, block or other aggregate bonded together with a mortar or mortars of adequate adhesion to the units and possessing suitable chemical and thermal resistance for the anticipated exposure. Such a structure may be assembled from units and mortars of a single type or from a combination of several different types of such units and mortars in order to achieve optimum and most economically satisfactory results." CRM structures as such comprise three components (1) Masonry units such as brick or tile (2) Mortars to bond them together, and (3) Membranes to attain a liquid-tight, fully resistant system. All of these components are available in various forms and are produced from many different materials. All three components must be chosen to meet both the environmental conditions and the design requirements of each application. 

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... 

With the exception of the epoxies, the adhesive quality of the cements and mortars is not high. They will develop hair cracks at interface with the masonry units consider these joints not watertight. The membrane is the major line of defense and is the watertight element in this construction. 

Resistant Masonry Units. C-279-79 in 1984 Annual Book of ASTMStandards Section 4, Construction Voi. 4.05, Chemical-Resistant Materials Vitrified Clay, Concrete, Fiber-Cement Products Mortars, Masonry,pp 170-172 (1984). 

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. 

Since, according to the commentary of certain other sources of brick specifications, as much as 80% of potential moisture growth takes place within most masonry units if they are exposed to ambient conditions for about a year, it seems that some simple measures could be taken to lessen the problem. For example, the brick for a given chimney could be purchased a year ahead of construction and "aged" before placement within the liner. Possibly even an artificial environment could be created to enhance the process. The resultant decrease in latent moisture growth characteristics would then reduce the degree of subsequent expansion to a point where it could be accommodated. This, of course, may not be practical for the majority of construction projects, but it may be worth consideration for some. 

The masonry units used in the pulp and paper industry include fireclay, shale, and carbon brick, structural glazed tile and Portland cement/aggregate brick. Structural glazed tile and Portland cement/aggregate brick are relatively unique to this industry and have not been widely used outside of it. 

First, let us consider constructions of masonry units (as acid brick) and mortar. 

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