Channel bodies and materials

A drainage channel system consists of various components that are coordinated with one another: the channel body (with or without a slope), the inlet points (inlet boxes or drains), the covers (grates, slotted covers), and various accessories (end caps, seals, connection spigots, etc.). The most important design features and current standard requirements of these components are described below.

The channel bodies of modern drainage channels are manufactured from materials that withstand high mechanical and chemical stresses. Common materials include concrete (or reinforced concrete), polymer concrete (synthetic resin concrete), and plastic. According to the earlier DIN 19580 standard, concrete, reinforced concrete, synthetic resin concrete, and fiber-reinforced concrete were permitted; the current EN 1433 standard does not specify strict material limits but requires proof of load-bearing capacity and durability. In Germany, national requirements (DIN 19580:2010), for example regarding freeze-thaw resistance, supplement the EN standard.

Polymer concrete has established itself today as the preferred material for channel bodies, especially for channels subjected to heavier loads. This material, a composite of synthetic resin (e.g., unsaturated polyester resin) and mineral aggregates, offers superior advantages over conventional concrete, including high flexural and compressive strength, virtually no water absorption (< 1%) and therefore frost resistance, smooth surfaces (low roughness for improved self-cleaning), and excellent chemical resistance. Polymer concrete channels achieve compressive strengths of >90 N/mm² and flexural strengths of >20 N/mm², are watertight (water penetration depth ~0 mm), and comparatively lightweight. They are therefore suitable for almost all applications, including those with high mechanical and chemical loads.

Conventional concrete channels are now manufactured from high-strength concrete. Previously, grades such as B 35 and B 45 (DIN 4281) were required, corresponding to approximately C35/45 and C45/55 according to current standards. Concrete channels must be watertight (water penetration depth < 30 mm). Weight reduction and increased strength are often achieved through glass fiber reinforcement (fiber-reinforced concrete). These channels are robust and relatively inexpensive, but heavier than polymer concrete and have a rougher surface. They are frequently found in standard applications of classes A 15 – C250. Concrete can reach its limits under heavy de-icing salt exposure or aggressive wastewater; in such cases, polymer concrete or coated systems are preferable.

For lower load applications (up to approximately class C 250), plastic channel bodies are also used, for example, those made of high-density polyethylene (HDPE). Their advantage lies in their very low weight and ease of handling on the construction site. High-quality plastic channels are often UV-resistant and chemical-resistant. However, they are more elastic and less dimensionally stable; therefore, plastic channels tend to deform under high loads and are rarely used in heavy-duty applications. Newer developments such as carbon fiber-reinforced plastics can enable higher load classes. In addition, there are monolithic plastic channel bodies with integrated covers that are vandal-proof and quiet (commonly used in stadiums and parks).

GRP channels consist of thermosetting resins (usually unsaturated polyurethane resin) reinforced with glass fibers and mineral fillers. They combine very low weight with high strength and excellent corrosion and chemical resistance, making them ideal for use in areas exposed to de-icing salt, acids/alkalis in splash zones, or marine environments. The smooth inner surface promotes high flow rates and good self-cleaning properties. Thanks to their fiber-reinforced construction, GRP channels are impact-resistant and dimensionally stable; at the same time, the lightweight components reduce installation effort, transport costs, and the load on the substrate. In practice, depending on the design, GRP systems reliably cover load classes from A 15 to D 400, and occasionally even higher, and are frequently used in parking garages, logistics areas, gas station areas, industrial yards, and other chemically demanding environments. Material-specific points must be considered: The coefficient of thermal expansion is higher than that of mineral materials, therefore a continuous, load-bearing bedding (e.g., concrete backing) and controlled expansion joints in the connecting surface are essential. Under prolonged static loading, creep deformation must be taken into account; the system approval/manufacturer's structural analysis defines the limits for this. For installations with increased heat loads (asphalt work), the manufacturer's specifications for temperature management and the timing of grating installation must be followed. Overall, GRP channels offer a robust, durable, and low-maintenance solution when low weight, chemical resistance, and ease of installation are paramount, especially where concrete reaches its limits or where polymer concrete would be disadvantageous due to weight or handling considerations.

All channel bodies must undergo quality control at the factory. In Germany, for example, the German Association for Quality Assurance in Drainage Technology (GET) awards test marks in accordance with DIN EN 1433/DIN 19580. The Federal Institute for Materials Research and Testing (BAM) also maintains lists of resistances that document the chemical resistance of various materials to oils, alkalis, etc.