Trowel application

These systems can be troweled on or extruded through a caulking gun. Little operator skill is required. Since the thixotropic nature of the paste prevents it from flowing excessively, application is usually clean, and not much waste is generated. With trowel application, the depth of notch and the spaces between them help regulate the amount of adhesive applied. Shallow, rounded, and closely spaced notches are often used with lower-viscosity adhesives to allow the lines of adhesive to flow together and form a continuous, unbroken film. 

Figure 4.8 Trowel application of polyurethane roof coating...

Trowel application is convenient only for large and flat surfaces such as floors, sandwich panels, walls (with a suitable high viscosity to avoid dripping). It is used to apply heavy coatings from 200 g/m up to several kg/m. ... 

Depending on the service, polymer concrete is cast in thicknesses from 1/2 in. (13 mm) to several inches, either with or without reinforcing. Cast-able polymer concretes are mixed and cast in a manner similar to that of Portland cement concrete, being poured into forms to harden. Troweled applications are generally thin coatings of less than 3/4 in. (20 mm) and are troweled in place with or without reinforcement. 

Mastic type formulations are generally applied by either an extrusion or by some type of trowel application or variation thereof. Extrusions can either be with the utilization of some type of automatic equipment or by common cartridge gun extrusion. 

Two-pack epoxy Section 12.3.3. These are widely used to give the maximum protection to concrete surfaces, floors and walls. They can be applied as relatively thin coatings by spray or as thick epoxy surfaces applied by trowel. In all cases, the application must be preceded by adequate surface preparation (see Section 12.6.1). To allow maximum penetration into the concrete the first coat must have a low viscosity. Coal tar epoxies are used where protection is the main requirement. 

There are other polymer processing operations often encountered in the manufacture of solid propellant motors. In one of these—the application of insulation to the inside of the motor chamber—various methods have been tried, and to date production processes have been developed for applying thick layers of filled rubbers to the interior of the chamber by such methods as casting, automated troweling, and spraying. To provide an adequate bond between the insulation material installed in... 

Waste water treatment. Supercritical CO2 has been put to use in a variety of industrial waste treatment applications. Clean Harbors Environmental Services, Inc., has used SCCO2 in Baltimore since 1989 to treat wastewater from chemical and pharmaceutical manufacturers. In the process the wastewater is pumped into the top of a 32-ft-high, 2-ft-diameter column, while the CO2 is pumped in from the bottom and percolates up. As the CO2 trowels up it dissolves the organics. CO2 contaminated with organics is at the top of the column, and clean water is at the bottom. The contaminants are incinerated off-site after separation from the CO2 which is recycled. 

Paste-Type Alkaline Removers. Sodium hydroxide, potassium hydroxide, or other caustic compounds are blended to make these types of removers. Polymer-type thickeners are added to increase the viscosity that allows the remover to be applied with a brush, trowel, or spray. Some of these products use a paper or fabric covering to allow the remover finish mixture to be peeled away, The most common application for this group of lemoveis is the iemoval of mchitectuial finishes from the inteiioi and exterior of buildings. The long dwell time allows for many layers of finish to be removed with one thick application of remover. 

It provides for certain application characteristics of the adhesive (brush, spray, trowel,... 

Control of Viscosity. To ensure that adhesives and sealants function well during their application and end use, the formulator must be able to control the flow properties of the product. The challenge that faces the formulator is that the adhesive or sealant may need different flow characteristics at different times. For example, adhesives must flow readily so that they can be evenly applied to a substrate and wet out the surface. Yet, there should not be an excess of penetration into porous substrates, nor should the adhesive run or bleed to create a starved joint. Certain adhesives and sealants must be capable of convenient flow application by trowel or extrusion, but they must also exhibit sag and slump resistance, once applied. Therefore, the flow properties, or rheology, of the material must fit the desired method of application. 

The epoxy adhesives are usually applied by simple extrusion from dispensing nozzles, brushing, or troweling. However, spray equipment may be used in certain applications. Conventional spray equipment is used with solvent-borne epoxy adhesives, but frequent cleaning is generally required. For fast-reacting systems, dual-nozzle spray equipment is available. 

Commercial grades are designed for specific end-uses, for example there are separate grades for trowel-applied products and for sprayable products. Cement systems modified with acrylic emulsion are used in numerous applications, as listed below ... 

All of these materials-brick, mortars and membranes-will be fully discussed in later chapters along with (1) Castables, grouts, and polymer concretes (2) Monolithics (troweled, sprayed and gunned linings) and (3) Expansion joint compounds, plus rigid plastic fabrications such as polyethylene, polypropylene and PVC. These components made from a whole host of materials are effectively used in a wide variety of industrial applications requiring superior chemical and thermal resistance. 

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. 

Air dry or low force cured systems utilize either amines, amine adducts, or polyamide curing agents for polymerization. They can be formulated for spray, brush, roller or trowel type applications. Since these materials do use a catalyst to obtain curing, they will have a limited pot life. This can vary from one-quarter hour to 24 hours depending on the type of catalyst utilized and the amount of solvent in the formulation. Systems vary in their solvent content generally from 60% to 0% solvents. As the solvent decreases, the pot I ife also decreases substantially. 

This means that the designer must make certain that his specifications are not misunderstood. He must carefully specify what the exact surface of the slab must be in order to be accepted, exactly what membrane shall be used instead of the waterproofing and how it shall be installed, exactly what bedding material shall be used to set the tile, and exactly what "grout" shall be used in the open joints. If a thin bed is to be used to bond the tile directly to the concrete substrate, he must indicate acceptable thicknesses for it and specify that the application Is to be made with a flat trowel-/iof a ribbed or serrated one that will lay ribbons of bed rather than a smooth, continuous, void-free bed on the concrete. All materials should be identified generically so that there is no mistake and so that if later another product said to be "equal" is substituted, the installer will be able to determine whether it is indeed equal. 

Troweled surfacing materials (monolithics) sometimes are used as membranes, where there may be a load on the surface beyond the capability of a membrane to support. In such cases, there may be adjacent areas of membrane and monolithic. If the system is to be continuous and void-free, the monolithic must be overlapped at all edges by the membrane, or the two surfaces continuously mated or flashed together. The inspector should examine this section very carefully for voids and discontinuities. In addition, he observes the following inspection procedure on the application ... 

Mor-Flo CS-38-S1 is a polyurethane modified acrylic concrete sealer. A simple water dilution and the addition of a preservative will produce a ready-to-use product. Leveling and wetting on tightly troweled concrete or other extremely smooth surfaces can be improved by the addition of 0.5% Fluorad FC-129 (1% active solution). Foaming, which may be a problem depending on the application method, can be greatly reduced by adding 0.03% of an antifoam emulsion (2). 

Adhesives can vaiy from low viscosity to high viscosity, depending on formulation and application. Thicket adhesives used for floor tiling are stiff when first put onto a trowel but spread easily over the floor. This ease of application is important to the user, although the quality of the adhesive is possibly judged more by its stiffiiess, which relates to yield stress value. 

In recent years, epoxy resin systems have been utilized for special applications on the exteriors of buildings. One of these systems involves the use of an epoxy plaster, which is troweled onto the surface of an exposed wall, into which are set stone aggregates. This surfacing resembles a pre-cast concrete panel with an exposed aggregate facing. This method is utilized, not only in new construction, but in re-surfacing deteriorated areas. 

A primer adhesive is first applied to a properly prepared concrete surface. A thin coat of epoxy mortar is then applied with a trowel. While this thin coat is still wet, a fiberglass membrane is rolled into the mortar. The edges of the membrane should be overlapped 2 inches. The mortar will squeeze up through the voids in the fiberglass mesh, resulting in adhesive base to which the final epoxy mortar will adhere. While this first application of mortar is still tacky, the second layer of epoxy mortar is applied over the glass cloth. This second layer may then be screeded and leveled. ... 

Among the various applications which have not been treated in greater detail are the spray coat applications and the underlayment applications. The spray coat applications are based on combinations of cement and other fillers, together with a latex binder. These applications may be applied by banish, roller and trowel, as well as by spray. They are often promoted as a substitute for "rubbing" concrete. 

Rheology and application procedure. The properties required of the repair material in the fresh state depend on the thickness of the new cover and the procedure used for the application [2,3]. If the thickness of the cover is high (e. g. higher than 50 mm) formworks may be used and the repair material should have a flowable or pumpable consistency and should be self-compacting, to be able to fill the space inside the form without segregating. When a lower thickness is required or a form cannot be used, the material can be applied by trowelling or can be... 

Application Location of Work Cement Sand Latex Troweling or... 

Thin section panel results. The results of the thin section panel evaluation are presented Table 3. Trial mixes PINR and PINT offered very similar workability and mesh bond characteristics. The difference in mesh concrete bond can be seen in Fig. 5 which compares the bond between the mesh and mix PINT with that of the control mix CL. The trial mixes PINR and PlNl gave the best all round balance between workability and finish. As can be seen from Table 3, the trial mix P2NL may suit an extrusion process very well. This possibility was identified during the construction of the thin section panel specimens and will require further research. During the application of the mix mortar it was noticed that additional trowel pressure gave the mortar a putty like appearance which also served to improve the surface finishes of the manufactured specimen. 

Some of the earliest major applications of adhesives in civil engineering involved the use of resins for abrasion resistant and non-slip surfaces to heavy duty floors and roads. This was achieved by the use of synthetic anti-skid grits, such as calcined bauxite, set in a resin base. Both epoxy and polyester resins have been used, applied either by trowel or in slurry form by squeegee. Trowelled systems are usually heavily filled mortars with an aggregate resin ratio of the order of 6 1 and as such usually require a priming... 

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