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32857 Parchem Technical Data Compendium 2015_Crop4emag.pdf

CONTENTS CONCRETE REPAIR CORROSION CONTROL GROUTS & ANCHORS PROTECTIVE COATINGS INDUSTRIAL FLOORING SURFACE TREATMENTS JOINT SEALANTS CONCRETE JOINTING ROOFING WATERSTOPS WATERPROOFING JOINT FILLERS TIMBER FLOORING ALPHABETICAL INDEX 304 Technical Data Fosroc® Preco RWB Sheet Surface revealing liquid for exposed aggregate finish on fresh concrete Uses Preco RWB is used to reveal aggregate in freshly placed horizontal concrete by delaying the surface set so that the mortar paste may be brushed and washed from between the aggregate particles, after the mass of the concrete has set. This produces an attractive exposed aggregate finish, or a key for subsequent pours or renders, e.g. floors, precast walls and slabs, paving, etc. Advantages „ Preco RWB provides uniform and controlled depth of retardation. „ Preco RWB treated surfaces are normally readily revealed and cleaned by careful jet hosing, brooming or wire brushing „ Surfaces treated with Preco RWB provide an excellent key for bonding subsequent renders or concrete, without the need for hacking, or mechanical scabbling „ Depth of reveal for various sized aggregate can be readily controlled „ Economical and simple method of horizontal concrete surface revealing „ Flexible time factor - up to 24 hours under normal application usage „ Less labour time necessary to obtain required face up finishes Description Preco RWB is a water based retarder for concrete surfaces, which is ready for use on freshly laid concrete to reveal the aggregate content of the mix. It is based on polyoxycarboxylates and other agents which combine to retard the set of the cement matrix on the surface of concrete to a depth of between 3 mm and 6 mm, depending upon the thickness and concentration of the application, and the design of the concrete mix. Technical Support Parchem offers a technical support package to specifiers, end-users and contractors, as well as on-site technical assistance. Properties Preco RWB is a stable water based solution and the active ingredients will remain in dispersion under sealed conditions. It must not be mixed with any solvent or liquid except clean water. Specific gravity: approximately 1.05 at 25°C. Application Instructions Application Allow the concrete to “firm” after it has been placed and compacted, to prevent the application of Preco RWB from marking trowelled surfaces. Stir the product before use Apply in an even coating by brush or apply (knapsack or stirrup pump) directly onto the exposed upper surface of the concrete immediately the mix has firmed, but before the initial set has taken place The depth of reveal can be varied to suit the size of the aggregate in the mix by altering the thickness of the coat of Preco RWB applied. To achieve a normal reveal on aggregate up to 20 mm, use at a rate of approximately 1 litre to 4 m² of surface area. For aggregate between 6 mm and 9 mm, dilute Preco RWB with between 1/2 to 1 equal volumes of water according to the reveal required. It is always advisable to carry out tests to determine the optimum application rate prior to full scale production commencing. Treated concrete surfaces must be protected from direct sunlight or warm draughts which may cause the surface to dry out rapidly. The concrete should be allowed to cure for up to 24 hours (less in elevated ambient temperatures) before hosing with water and brushing to remove the unset cement matrix. The concrete should be cured in a normal manner but if a delay of longer than 24 hours is unavoidable, or in the case of elevated temperatures, the concrete should be covered with polythene sheet. If delays of longer than 24 hours are experienced between the application of Preco RWB and the removal of the cement matrix, the concrete surface will begin to harden and an even aggregate reveal will be difficult to accomplish. Select aggregate sizings and gap gradings to suit end result desired. See under Limitations. Cleaning Water Limitations Approval test - always pre test on a small section to determine the thickness or concentration of Preco RWB to give the reveal required. This is particularly important with finer aggregates such as 6mm and 9mm and with concretes with accelerated set additives such as calcium chloride, heated or steam cured concretes, etc. The application of excessive quantities of Preco RWB will result in a very deep reveal, and the displacement of aggregate during hosing and brushing. As a consequence of this, the surface texture of the concrete will be uneven. Preco RWB delays the set but does not prevent setting on exposure unless excessive quantities are used or added directly to the concrete. Proper curing of exposed aggregate surface is essential for maximum strength development. In order to achieve a uniform exposed aggregate surface, it November 2011


32857 Parchem Technical Data Compendium 2015_Crop4emag.pdf
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