Producers of upmarket concrete slabs and blocks increasingly provide their customers with top-class, premium-quality products that emphasize the sophisticated design of the property thanks to their visual appeal and texture in combination with a wide variety of laying patterns (Fig. 1). SR Schindler based in Regensburg, Germany, supplies a wide range of individual machines and production lines for manufacturing premium-quality products that stand out visibly and tangibly from high-volume, mass-produced items thanks to their custom concrete recipes and top-class surface quality. Using such equipment and machinery enables concrete companies to offer products for any design preference and area of application, thus expanding their business to new market segments.
When producing finished concrete slabs and blocks, we can generally distinguish between wet-side and dry-side surface finishing methods.
Wet-side surface finishing
On the wet side of the production line, products are treated immediately after the end of the manufacturing process, which means that they have not hardened yet. Methods in this category include washing as well as coloring and marbleizing, especially for slabs produced on hermetic presses.
Using various matrices or tamper heads during the production process is another appropriate option for turning a smooth-surface item into a textured slab or block, for instance in an authentic slate or wooden look (Fig. 2). Matrices are custom-made plates composed of steel and rubber inserted into the molds of hermetic presses in order to function as the negative profile of the envisaged surface texture (Fig. 3).
SR Schindler has been manufacturing these matrices for many years at its own production facility. The company’s portfolio currently includes over 1,500 designs of up to 1,200 mm × 1,200 mm in size.
Dry-side surface finishing
The dry side of the production line provides many more finishing options. This is where cured products are treated mechanically and/or chemically in order to create their final appearance.
Blocks and slabs are most commonly finished using one or more of the following methods:
Additional options for paving stones and masonry blocks include:
Finishing by grinding/polishing
In the grinding/polishing step, concrete products are treated using special grinding or polishing tools, such as high-performance industrial diamonds, in a wet or dry process so as to create a specific ground or polished finish, reaching from a slightly ground to a highly polished, glossy surface. Depending on the intended look and feel four to ten of these stations are in use to create the individual products.
Finishing by blasting and curling
Blasting using steel or stainless-steel microspheres exposes the aggregate particles by partially removing the cement layer in which they are embedded, thus slightly roughening the product surface. This is why blasted products are frequently used for outdoor spaces because they provide greater slip resistance (Fig. 5). Blasting can be performed either after slight polishing or as an intermediate step prior to curling, or as the only finishing process. Depending on the specific application and modification of process parameters such as conveyor speed, rotational velocity of the turbines and sphere diameter, a wide variety of surfaces can be created to expand the product portfolio considerably.
Blasting can be followed by curling in order to create a silky smooth surface. This method uses rotating brushes (Fig. 6) for removing excess cement and exposing and slightly polishing the aggregate particles. Curling is recommended not just as a finishing step but also as a virtually mandatory process prior to coating and printing. The brushes and optional high-performance cleaning system remove residual dust from the product surface. The dust-free surface then enables the coating agent to penetrate into the face mix, which is an indispensable prerequisite for creating a durable surface protection and long-lasting prints.
Post-treatment by impregnation or coating
Impregnation or coating is the last step in the surface finishing sequence. It protects finished products from weathering and soiling while making the items easier to clean. Depending on the specific chemical components, a primer coat may first have to be applied, followed by spraying or rolling the coating agent onto the surface (Fig. 7, Fig. 8). Infrared or UV modules ensure pre-heating or drying of the products (Fig. 9).
Bush hammering, ageing, splitting, and edge treatment
Paving stones, masonry blocks and block steps can additionally be aged/bush-hammered or split, or their edges can be broken if the surrounding architecture calls for an antique and/or historic appearance.
Maschinen- und Anlagentechnik GmbH
Hofer Str. 24
+49 941 69682-47