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A growing number of architects and owners are opting for concrete flatworks that resemble slate, brick, tile, stone, or even wood. Stamped concrete creates an illusion of expensive slate or tiles at a lower cost. It can brighten a poolside, enhance an entrance, and glamorize a driveway with colors and patterns. Unlimited color capabilities offer architects and designers total flexibility to match any design, theme or specification. If texture is desired on patterned surfaces, stamped concrete is applied using stamping mats that simulate slate, granite pavers, used bricks, and wood. Yet, results require the use of the right tools, good concrete, and correct finishing and stamping procedures.

Concrete requirements for stamping

Generally, stamped concrete proportions depend on depth of stamped pattern. For example, if an area is intended primarily for vehicular traffic or if the grooves are to be grouted, the desired pattern penetration may be as much as 20mm. In such cases, concrete with 20mm maximum size aggregate works best and enables workers to achieve uniform imprint depth; the slump should not exceed 120 to 150 mm. In contrast, embedding a stamping tool to a depth hovering 5mm requires minimal interference from coarse aggregates, thereby requiring reduced maximum aggregate size.

Entrained air is required for concrete that will be exposed to freezing and thawing; this can be as high as 7.5% for 20mm gravel concrete. When deeply grooved patterns are cut without using thin polyethylene films between the tool and concrete, tools must be cleaned frequently with water to prevent concrete from sticking to them. Spraying tools with a release agent may also help.

Retarders are sometimes needed to extend the period during which concrete can be stamped and increase daily production. This slows the setting long enough to permit stamping. However, if too much retarder is used, the stamped surface may crust over and even crack. Some contractors try to slow setting, especially in hot weather, by using less cement and increasing the slump. Concrete quality might suffer when this is done. No admixtures containing calcium chloride should be used for colored stamped concrete, as these could cause discoloration.

Procedures for stamping concrete

Good quality stamped concrete requires dedicated craftsmen who consistently follow proper concrete placing and stamping procedures.

Planning and preparation

Ideally, stamping should be the last job done on-site so the concrete is not damaged or stained during other construction operations. Plan the layout to provide a pleasing appearance, including the location of contraction and construction joints to minimize cracking and control pour size. Pours should be scheduled about 2 1/2 hours apart. Experienced crews can stamp as much as 60 to 70 m² / hr. and achieve daily rates of 150 m². The ready-mix concrete producer should be notified of special mix requirements.

Initial finishing

After placement, concrete should be struck-off and bull-floated. Vibrating screeds or hand tampers may be needed if aggregates larger than 20mm sizes are used in the concrete to embed coarse aggregates below the concrete surface, making it easier to stamp deep patterns. No troweling should be done after completion of the coloring process.

Coloring concrete

Stamped concrete coloring may be achieved by two alternative methods, the integral color procedure, where the entire volume of concrete is colored by adding the color in liquid or powder form to the concrete mixing or cast on color procedure, where the color hardener is spread onto the surface of the wet concrete and the colored layer floated onto the top layer of the wet concrete. After the bleed water has disappeared, about half the color hardener is spread on the surface and floated on the concrete. When no surface bleed water is visible, more color is spread and floated. At least two spreading and floating operations are required, but some contractors spread hardener and float three or four times to achieve a surface of uniform color. The integral color procedure offers the advantage of the entire volume being colored while the cast on color increases the wear resistance of the surface treated. A stamped concrete system may combine the above two methods.

Stamping

Judgment is required to decide when to start stamping. Typically, it is recommended pushing a finger into the plastic concrete to determine when to start; if the hole keeps its shape and does not fill with water, stamping can begin. Concrete is frequently stamped through plastic sheeting laid on the surface. Thicker sheets will wrinkle and mar the surface. When placing plastic sheeting, use a soft broom or trowel to smooth it over the concrete surface. When texturing is done with rubber mats, the powdered release agent is dusted by-hand. Note that the powder is extremely fine, and workers should avoid breathing it by wearing double-layered painter masks.

Jointing

One way to joint stamped concrete is with leave-in-place wood strips. Another way is to use cold chisels, hand stamping joints that conform to the pattern. However, when this is done, the owner should be alerted to the possibility that cracks would not follow the joints. Leave-in-place headers can be used as construction joints between adjacent pours. When there are continuous straight lines in the pattern, such as with running bond bricks, simply run the stamp up to the irregular edge of the pour.

Final texturing

Wet surface brooming should eliminate most stamping imperfections. Some contractors mix 20 parts of water with one part color hardener and dip the broom in this mixture before gently brooming the surface (check with the color hardener manufacturer for recommendations concerning use of product). Workers may have to walk on the concrete and should wrap their boots with polyethylene film so they don’t mar the surface. Care must be taken not to over-broom or to start brooming when the surface is too soft.

Curing and sealing

Colored wax curing agents must be used because other curing methods are likely to cause surface color variations. Use a color curing membrane that matches the color of concrete. Applying wax produces a shiny surface, promotes cement hydration, and reduces shrinkage cracks. Periodic waxing is required to maintain a shiny surface, but many owners opt for the appearance of naturally weathered surface after the initial coating has worn off. When powdered release agent is used, concrete-curing operations must be delayed because the wax-curing compound cannot be applied until the release agent is removed.

To beautify existing or new concrete surfaces, a highly durable wear resistant mortar overlay in thickness of 0.5 to 1 cm may be colored and stamped to match various design schemes and specifications using procedures outlined herein above. It is commonly used in applications ranging from pool decks, patios and driveways to hotel lobbies, shopping centers and retail stores. It may also be applied, without stamping on it a pattern, if the design so requires.

A popular alternative to covering existing concrete with thin mortar that is gaining in popularity is to spray or trowel, over new or existing concrete surfaces, a two-part deck product that includes a liquid resin and cement-based powder product. In many instances, old surfaces may be also cleaned and polished with special cleaning and polishing products to extend their service lives and improve their appearance.

Exposed aggregate finishes to create texture can be used in conjunction with stamped concrete techniques to create various decorative options on regular or stamped concrete surfaces. The product reacts with the upper concrete surface to delay its setting, thus exposing the aggregate particles with distinctive permanent color together with high durability surface.

When properly applied, stamped concrete yields high durability surfaces with colors and shapes similar to natural building materials. As in all decorative systems, it is always recommended a concrete sample be produced first to ensure it meets the designer’s specifications and expectation.

Related Products:

Batimix Clear Seal 600
BATIMIX Clear Sealer 600 is a low VOC solvent-based concrete sealer formulated with crystal clear acrylic resins for use in regions with strict VOC limitations. It is specially designed to provide excellent penetration, flow, and cure characteristics.
Batimix Stain Sealer 610
BATIMIX Stain Sealer 610 is a unique pigmented solvent-based stain sealer designed specifically for concrete and other decorative surfaces. This product is non-yellowing and resistant to salt-spray, acids, alkali, water, ultraviolet rays, and wet and dry abrasion. It provides a cool surface on pool decks, restores old-looking concrete to a new luster, and eliminates staining while providing an easy to clean surface.
Batimix Color Hardener 620
BATIMIX Color Hardener 620 is a ready-to-use colored surface hardener for coloring and hardening freshly poured concrete. Typically used to provide the base color for stamped concrete, it is applied as a dry shake over freshly leveled and floated concrete in light industrial, commercial, and residential areas. BATIMIX Color Hardener 620 is composed of cement, wear-resistant specially-graded silica quartz aggregate, and finely ground inorganic coloring pigments and other propriety components, which improve the properties of the finished concrete surface.
Batimix Color Release P-650
BATIMIX Color Release P-650 is a release agent that forms a moisture barrier between the stamping tools and wet concrete. It facilitates the release of imprinting tools. It is a dry shake material applied directly on top of the concrete before stamping. The releasing agent, which is available in different colors, contains pigments that add color and depth to the stamped surface. For use on stamped concrete products only.
Batimix Release L-660
BATIMIX Release L-660 is a liquid release agent used in Stamped Overlay applications, and anywhere powdered release agents are impractical to use. This release agent conditions the stamping tool to prevent the concrete from sticking to it and allows for the best possible imprint without pulling up the surface.
Batimix Mortar SC-670
BATIMIX Mortar SC-670 is an easy to use polymer-modified, cementitious single-component re-surfacing compound ideal for renewing worn or spalled concrete. It is a highly durable wear-resistant mortar overlay that can be colored and stamped to match various design schemes and specifications, using procedures outlined hereinabove.
Batimix Mortar SC-690
BATIMIX Mortar SC-690 is a two-component, polymer-modified, cementitious compound applied in thin layers, whether on new or worn concrete substrates. It promotes excellent adhesion, toughness, and long-term durability together with high resistance to moisture penetration and degradation due to hydrolysis
Batimix Surface Retarder 730
BATIMIX Surface Retarder 730 is based on modified gluconate chemicals used to retard the setting of top concrete layers. It exposes the aggregate solid particles of structures after concrete surface washing.

Statement of Responsibility: The information and application advice contained in this document are based on the present state of scientific and practical knowledge of Holderchem SAL. It is provided with no warranty, implied or otherwise, as to its completeness or accuracy. Since methods and conditions of application and use are beyond the control of Holderchem, HOLDERCHEM MAKES NO WARRANTIES, IMPLIED OR OTHERWISE, AS TO THE MERCHANTABILITY OR FITNESS FOR ORDINARY OR PARTICULAR PURPOSES OF ITS PRODUCTS AND EXCLUDES THE SAME. Holderchem warrants that its products shall be of sound materials and workmanship. As products are applied, handled and stored in manners and site conditions over which Holderchem has no control, Holderchem’s liability in respect of any material which can be proven defective shall be limited to the replacement of such defective material or reimbursement of its cost at Holderchem’s option. Holderchem shall not be liable for any consequential or incidental damage or loss arising out of the use of its products.

Important Note: Holderchem shall have the right to modify product specification sheets at any time without previous notice. Buyers should always refer to the most recent data sheets, copies of which can be supplied upon request. The sale of products mentioned in this literature shall be subject to Holderchem’s General Conditions of Sale Delivery and Payment[Visit: https://holderchem.net/gcsdp]

Holderchem R&D
Holderchem R&D seeks to develop solutions to meet construction challenges by bringing to market innovative products and systems, which offer benefits across the complete life cycle of buildings and other constructions. The aim is to supply customers with high-performance products to help them achieve better productivity, lower overall costs, and achieve extended service life and functionality. Research also aims at developing the Holderchem range of Batimix products with a particular focus on polymer emulsions, polymer-inorganic interactions, and product applications.
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