New method to add marbled textures to concrete products

This Colormix module for which KBH has submitted a patent application makes it possible to produce concrete paving blocks and slabs in a range of up to six shades. KBH Maschinenbau, a division of Baustoffwerke Gebhart & Söhne & Co. KG, identified a new approach to adding a marbled texture by a simple yet brilliant intervention in the face mix dosing system.
The issue of multi-colored surfaces has long been known in the manufacture of concrete products. In many cases, the desired shading or nuancing of the colors was hard to achieve in the production of multi-colored blocks and slabs without causing an unwanted mixing of all shades. There is a continuing trend in the industry towards producing a marbled texture that resembles the appearance of natural stone. This results in surfaces with an arbitrary color pattern that, on the other hand, remains within a defined spectrum and formation of the “veins”. This poses challenges in production with regard to the placing of the face mix. If the mixing of the individual batches becomes too significant, this leads to unwanted “foreign” shades, or a color blur is created. The processes usually applied in the past included a batch by batch feeding of the different pigmented mixes into the face mix hopper. From there the concrete slides directly into the feed box. When the face mix feed box begins to fill the first cycles, the color pattern is initially uniform and dominant. Only after a certain period of time the color blend starts to become visible in a gradual process. Up to this point, however, the paver machine will have produced dozens of cycles of rejects with improperly blended products.
KBH succeeded in using a complementary module to generate the desired shade right from the first production layer. In this process, the company benefited from in-house synergies between equipment manufacturing and paving stone production. Since spring 2008, the Colorist has been used to generate a great variety of Colormix shades, starting as part of a test setup and later in regular production. The new module has been installed in an in-line arrangement, and can be integrated in virtually any production line. Whenever single-colored products are manufactured, the Colorist will be idle. The complementary module is usually put on top of the face mix feed hopper and serves as an intermediate storage space for pigmented face mix batches. If, for example, the throughmixed concrete is to be shaded, too, a Colorist is also available for the base mix. The base concrete Colorist is primarily used for color blended retaining walls and split retaining walls. Its design enables the system to be retrofitted to nearly all concrete block machines. When the required color shades or pigmented (or colored) concretes have been fed into the Colorist in their respective proportions, the concrete is filled into the feed hopper below via a main and secondary mechanism. The main feature is the flexible pull plate attached to the bottom (between Colorist and face mix feed hopper). The second mechanism is controlled via a dosing gate. All requested batches are filled into the Colorist and show a relatively even distribution. When all face mixes have been fed into the Colorist, the dosing gate attached to the rear side is actuated first. This gate consists of a slotted rear wall and flexible closing flaps. This arrangement ensures that a controlled, small amount of concrete is transported into the feed box over the entire filling height. As a result, a portion of each type of colored concrete is simultaneously filled into the feed box. In the next step, the pull plate opens slowly in a gradual process. This novel filling process ensures that multi-colored concrete products with a marbled texture are produced right from the first layer. The variable-frequency control system is included in the standard package, and is also used to store the mix designs for various shades. The composition of the mix may be changed and stored as a new mix design. This ensures quick production changeover and a high degree of reproducibility. In order to perfectly fine tune the production line to the amount of face mix needed, KBH provides an Excel calculation tool to its customers that offers guidance on how to set the Colorist correctly. In the case of any production issues arising at the customer’s facility, the equipment supplier can provide online help via an Internet connection. Since the Colorist is a supplementary module, rather than a complete system, it can be installed at a low cost. Also, the process control unit installed at the customer factory need not be reprogrammed. When considering the higher price that can be achieved with multi-colored and marbled products, the investment in the module will pay off already within a very short period, according to Mr Gebhart, Managing Director at KBH.    

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