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www.cpi-worldwide.com CPI %u2013 Concrete Plant International | India Edition %u2013 5 | 2025Processing in the fresh and cured stateRound and square test specimens were extruded to characterise the processing parameters in the fresh state of the concrete. The surfaces of the rectangular specimen were processed with the different brushes. The round specimens were milled with a solid carbide milling cutter. The following parameters were refined experimentally.Table 1: Parameters for the processing of fresh concreteParameter Milling BrushingCutting speed up to 120 mm/s 50 mm/sRotary speed 4,500 - 5,000 rpm 1,200 - 1,800 rpmCutting depth up to 10 mm up to 10 mmProcessing time after extrusion2.5 - 6 hours 1 - 2 hoursCompared to milling, concrete is brushed at a lower feed rate and lower speed. Processing is possible with all brush hardness grades. The process window for brushing is significantly earlier than for milling, as a chip must be formed during milling. If the process window is too early, the surface will be smeared. The result of brushing and milling shows a lower surface quality if processing is too early. Smooth surfaces are finished two and five hours after extrusion (see Fig. 4). At the end of processing, a homogeneous, closed surface should be created in the fresh state so that measuring and referencing in the working area of the milling process can be carried out easily in the hardened state. After extrusion and machining in the fresh state, milling in the cured state (t > 24 h) was investigated using various test specimens with different surface structures to be produced. It was found that milling with a carbide milling cutter in the dry milling process is the most effective way to achieve the desired results. As a result, various test specimens were extruded and milled. These surfaces are of high quality and are suitable for moulding with a casting resin. The model for the formwork element was then machined after extrusion with a solid carbide ball nose end mill in the fresh state. The required reference surfaces were milled with an offset of 5 mm in the fresh state. The results for machining in the fresh state show enormous potential, including for the direct production of precast concrete parts using 3D printing.Fig. 4: Brushed (left) and milled (right) test specimensf = 50 mm/sn = 1800 rpmt = 2 hf = 50 mm/sn = 4800 rpmt = 5 hConcrete Pen www.concretepenfactory.comDiscover the new Concrete Pen!%u00bb New design%u00bb Enhanced surface quality%u00bb Personalization now possible in precise color printing