Concrete surface finishes

The surface of the concrete slab should have good texture to provide sufficient and lasting skid resistance. Other factors such as noise generation may be of concern. The provision of good texture is obtained by usual techniques such as tining, hessian drag, broomed, exposed aggregate concrete, stamped concrete and so on, the details of which can be found 

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ABRASION-RESISTANT CONCRETE (SURFACE FINISHING PROBLEMS ASSOCIATED WITH AIR-ENTRAINED AND RETARDED CONCRETE)... 

Part V mentions and describes concrete surface finishing processes that are environmentally friendly, their basic characteristics, and their future scopes. In... 

The interior surface finish, to comply with EEC and other health standards, must be rustproof, cleanable, and free from any crevices which can hold dirt. Bare timber in any form is not permitted. Most liners are now aluminium or galvanized steel sheet, finished white with a synthetic enamel or plastic coating. GRP liners are also in use. Floors are of hard concrete or tiles. Very heavy working floors may have metal grids let into the concrete surface. Floor concrete is coved up at the base of the walls to form a protective curb. 

The physical panel size used resulted in more joints between panels than would have been the case in a Portland cement pour, owing to the surface finishing with a screed and the continuous obstruction of the existing support columns. Asphalt expansion strips were placed between panels and were provided with a removable top strip which was filled with a polyurethane compound. Shrinkage of pours in this work was negligible. Shrinkage in sulfur concrete was proportional to the amount of sulfur binder used. 

Laitance A weak layer of non-durable materials containing cement and fines from aggregates on a concrete surface that is usually caused by an overwet mixture, overworking of the mixture, improper or excessive finishing or combinations thereof. 

Carbon steel substrates must be sandblasted to a near-white metal finish (SSPC-SP10 or NACE 2) and maintained at least 5°F above the acid dewpoint during installation. Concrete surfaces must be free of any imperfections such as blow holes or honeycombing. Old concrete must be free of oil, grease or chemical contamination. 

The test was conducted in accordance with ASTM C 944-90a Standard of Abrasion Resistance of Concrete by the Rotating-Cutter Method. This method measures the capacity of wear resistance of a concrete surface. The specimens were 5 in. (127 mm) long, 4 1/2 in. (114 mm) wide and 1 1/2 in. (38 mm) thick and were cut from the tops of the beams cast for the deicing scaling test. The rotating-cutter was applied to the interior cut surface and not to the tool-finished surface of the sample. 

The actual size of the roughness elements on any surface will vary with the material, age and usage, deposits, dirt, scale, rust, etc. Typical values for various materials are given in Table 5.3. The most common pipe material—clean, new, commercial steel—has an effective roughness of about 0.0018 in. (0.045 mm). Other surfaces, such as concrete, may vary as much as several orders of magnitude, depending upon the nature of the surface finish. 

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). 

Cag ) comes into contact with the surface of concrete(take x = 0 at the surface). (2) Diffusive CO2 (molar concentration, Ca2 diffusion coefficient, Da2 in concrete) feels the mass transfer resistance at the surface of concrete (surface mass transfer coefficient, Kg g), unless the equilibrium Ca2 = al satisfied ( k-ag + ). The retardation effects of finishes on the diffusion of CO2 (thickness,... 

Air-entraining admixtures are used to reduce bleeding and improve cohesion, compaction and surface finish in extruded concrete. 

Once the steel becomes active due to carbonation of concrete or chloride penetration, the influence of chemical composition, microstructure and surface finish-... 

Fields of applicability. Figure 15.3 depicts the fields of applicability of pickled stainless steels in chloride-contaminated concrete exposed to temperatures of 20 °C or 40 °C. Fields have been plotted by analysing the critical chloride values obtained by different authors from exposure tests in concrete or from electrochemical tests in solution and mortar and taking into consideration the worst conditions [11-28]. Nevertheless, it should be pointed out that values are indicative only, since the critical chloride content depends on the potential of the steel, and thus it can vary when oxygen access to the reinforcement is restricted as well as when stray current or macrocells are present. For instance, the domains of applicability are enlarged when the free corrosion potential is reduced, such as in saturated concrete. Furthermore, the values of the critical chloride Hmit for stainless steel with surface finishing other than that obtained by pickling can be lower. 

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. 

CL Very dry appearance Difficulty in trowelling, material crumbles Cannot obtain a smooth surface finish Does not pass through mesh Difficulty demoulding material crumbles Poor finish Concrete delaminates from mesh... 

PINR Very fluid mix Very good trowellability Easy to impart good finish. Similar to PINL Flows easily through mesh To be used rapidly as trowellability reduces within 30min Easily demoulded Reasonable surface finish Good concrete/mesh bond... 

A more expensive barrier approach can be seen on bridges where the reinforced concrete has been clad in a brick or masomy finish, usually for cosmetic reasons. The salt rarely penetrates to the concrete surface. However, this option is rarely available for reasons of cost. Encasement of building elements can often be undertaken as part of a refurbishment programme, such as with a change of use. External cladding can be added which encloses concrete elements at risk of corrosion. Once in a warm, dry, indoor environment the risk of corrosion is significantly reduced. 

The size and shape of the hard and durable aggregate, as well as proper mix design and the curing process, play an important role in this technique. The cost of exposed aggregate concrete surfacing is slightly higher than that of a similar pavement with conventional brushed concrete finishes. 

In this chapter, we explained the meaning and basic concept for environmentally friendly surface finishing. And as a concrete example, a unique case - HACCP (the assured environmentally friendly surface finishing process) was introduced. There are still many typical environmentally friendly surface finishing processes. However, those typical processes will be described in other chapters. In this chapter, two cases were introduced. One of them was the production process composed of heat treatment and surface treatment to produce films that were intermetallic compounds between Sn-Ag and Cu-Ag. The intermediate compounds could show antibacterial effects and control dissolution simultaneously. The other example was a composite film based on the silane compound. Nano silver or copper powders were dispersed into a silane compound. The organic compounds of those antibacterial metals were also dispersed into silane compounds. The antibacterial, nano-powder dispersed, silane compounds were coated on various materials. These coated materials showed antifouling properties on their surfaces. They all assured HACCP and environmental friendliness. 

All metal (e.g., tie wires) reaching through the concrete must be cut back at least V2 in. below the surface. The voids created should be completely filled with a rich Portland cement-sand mix tamped into place and finished flush with the concrete surface. 

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