Concretions adherent

Corrosion inhibitors. Corrosion-inhibiting admixtures are essentially designed to improve the performance of good-quality reinforced concrete. It has been emphasized that the function of such admixtures is not to make good concrete out of poor quality concrete. Adherence to this important principle is important in order to avoid unrealistic performance expectations for corrosion inhibitors in concrete. 

In modem PMR constmction, thermal iasulation that is unaffected by water or that can be kept dry ia some manner is required. Extmded polystyrene (XEPS) foam iasulation boards ate commonly employed (see Insulation, thermal). They ate placed on top of the waterproofing roof membrane, which is next to the deck. The iasulation should not be adhered to the membrane. Ballast at the rate of >48.8 kg/m (1000 lb/100 ft ) holds the iasulation ia place and offers protection from the sun. The iasulation joiats ate open and drainage must be provided. Various other materials, eg, patio blocks and concrete slabs, ate also used as sutfaciags and ballast. The extra weight imposes mote exacting requirements on constmction. 

Pa.ints, Paints (qv) prepared from poly(vinyl acetate) and its copolymers form flexible, durable films with good adhesion to clean surfaces, including wood, plaster, concrete, stone, brick, cinder blocks, asbestos board, asphalt, tar paper, wahboards, aluminum, and galvani2ed iron (147). Adherence is also good on painted surfaces if the surfaces are free from dirt, grease, and mst. Developments in emulsion polymeri2ation for paint latices have been reviewed (148). 

The rust-colored concrete chips shown in Fig. 11.24 were removed from the tube ends. Inspection of the water box revealed large quantities of debris adhering to the tube sheet. The gouging was caused by the lodgement of this hard debris at tbe inlet end of the tubes. Intense turbulence by the lodged debris was sufficient to cause highly localized erosion. 

Have ability to form continuous films in mortar or concrete, due to a lower minimum fihn-forming temperature than the application temperature, which adhere well to the aggregates and cement hydrates and possess good alkali and water resistance. 

In recent years use of the oxide as a constituent of cement has been advocated,1 especially in Sweden. Thus, a mixture of Portland cement (60 to 70 per cent.) and white arsenic (40 to 30 per cent.) heated to 200° to 250° C. affords a hydraulic cement of normal setting time and of less solubility than ordinary cement, so that lime liberation is inhibited and the resistance to water improved. Wooden structures exposed to the action of sea water may be protected by spraying with a concrete composed of white arsenic, cement and sand in the proportions 1 3 12. The arsenic makes the mixture elastic and helps the cement to adhere to the wood. There is, however, danger in the too widespread application of arsenic in the directions described above. 

Hot asphalt applications had been used for many years in concrete tanks, inner lined with brick for similar service, and also, of course, unlined wood tanks made from timber, and small pickling tanks made by hollowing out cavities in granite blocks. But the use of hot asphalt as a liner for steel tanks had been unsatisfactory due to the erratic cold flow of the asphalt which demonstrated selective adhesion to steel and so would tear and open cracks in the membrane system in the areas of cold flow below the points where it adhered. To overcome this difficulty, a number of inventive persons experimented with the manufacture of asphalt sheet lining materials, similar in form to the sheets of natural rubber, in which the asphalt was compounded with various admixtures, including rubber. These asphaltic compound sheets were then warmed sufficiently to make... 

If there is no membrane under the joint, as in an expansion joint in a tile floor laid directly over a crack in the concrete slab, the deformable sealant will adhere to the bottom as well as the sides of the joint. If this happens, the deformable material will not function properly. The joint cannot open without pulling the filler off the sides of the joint at the bottom, or close without tearing it loose at the bottom and top of the joint. 

In the early 1970s, light, closed-cell foamed borosilicate glass block (see Chapter 17) were developed. These block, with a mass of only 12 Ib/cu.ft., will adhere to the underside of a concrete or steel cover by using a urethane asphaltic adhesive all joints between them are made the same way. Insulation of this type has been applied to the underside of both concrete and steel covers and has functioned successfully for a decade. 

If quarry or ceramic tile is adhered to the concrete substrate with a strong adhesive, exactly the same rules as for the monolithic should be followed, including stress relief, since the adhesive functions in an identical manner. The tile must be cut to place the expansion jo-int in the tile exactly over the one in the substrate. On the other hand, if the floor is protected by "acid brick" laid on a membrane, the membrane acts as a "sliding joint" as described earlier, and the expansion joint in the brickwork may be offset by as much as a brick length from the point of movement in the substrate—saving the installer the cost of cutting brick to match exactly the expansion joint in the slab. 

This is probably the most frequent treatment performed on museum objects. It can range from removal of loosely-deposited surface dust to that of hard, adherent concretions. In general, it is considered as a simple and self-evident task and consequently not much thought is given to it. However, it is not a simple task and, in many cases, difficult decisions have to be made about how it has to be performed. If a metal object has a heavy calcareous incrustation covering most of it, would removal of this incrustation, which may result in the removal of the original patina the object had, be acceptable Loss of the original patina means that part of the information that patina carried (How was that patina formed Was it natural Was it the result of an intentional treatment ) would be lost, and with it, part of the authenticity of the object. 

Since cement contractors cannot finish foundations to exact levels, it is customary to provide a rough finished machine foundation 1 to 2 in. below the required level. The equipment is temporarily wedged and then positioned by adjusting nuts. The frame is then grouted in place by use of a mortar fill which adheres to the rough concrete surface (Fig. 8-6c). 

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