Capillary storage base layer

Abstract

Capillary storage base layer, a base layer without binder (based on 'ToB' as defined in the applicable TL SoB-StB or EN 13285) for unsealed, open-pored surfaces in road construction / civil engineering, characterized in that it is designed to absorb rainwater in a structurally acceptable quantity in a decentralized manner, to temporarily store a relevant amount of water and to release it upwards towards the surface in dry conditions via capillary action.

Description

[0001] 1. Technical Field: The invention technically belongs to the field of road construction / civil engineering. In particular, it relates to innovative base courses for unsealed, open-pored surfaces such as water-bound surfaces, clay courts, gravel lawns, grass grid or honeycomb systems, and sports fields. The area of ​​application is primarily designed for pedestrian areas and low traffic loads up to a maximum load class of 0.3 according to the German Road Traffic Regulations (RStO).

[0002] 2. State of the Art: The state of the art known to the applicant comprises unbound base courses primarily designed for rapid drainage. Furthermore, construction methods based on the so-called "sponge city" concept exist, such as infiltration areas, drainage surfaces, or underground artificial storage chamber systems. These existing concepts aim to either drain water from beneath a technically constructed surface in a delayed manner or to temporarily store it and make it available in a controlled manner for other uses, but not to return water to the surface naturally on-site via capillary action. An example of this is Rummelsburg Bay. 1In Berlin, sunken, trough-shaped green spaces—so-called infiltration basins—ensure that rainwater is retained during heavy rainfall. Instead of draining the rainwater into the sewer system, it is temporarily stored in a lowered storage chamber beneath the green spaces. The release into the ground then occurs gradually, as does the replenishment of the groundwater. Other solutions include tree trenches and infiltration basins combined with tree planting.

[0003] Copenhagen is a pioneer in the field of sponge cities. 2 . But here too, construction measures such as unsealing, underground trenches, etc., were carried out to retain the water and release it gradually to the nearest stream or lake or to the port, or - if this is not possible - to drain it into the sewer system or allow it to evaporate.

[0004] Capillary-active load-bearing layers in the field of road construction / civil engineering are currently not state of the art.

[0005] 3. Problem Statement: The problem underlying the invention is that conventional base courses in road construction are designed for load-bearing capacity and rapid drainage (see also ZTV SoB-StB etc.) and do not offer any mechanisms for storing and capillaryly returning rainwater. This leads to the following problems, which the invention aims to solve: • Overloading or oversizing of wastewater systems during rain. • High levels of seepage water during prolonged periods of precipitation, especially in densely populated areas. • Lack of sustainable management of water resources and lack of water return to the natural cycle during dry periods. 1 https: / / www.gruen-in-die-stadt.de / schwammstadt / 2https: / / neuelandschaft.de / artikel / kopenhagen-vorreiter-beim-thema-ueberflutungsvorsorge-3350 • Insufficient support of the urban climate through evaporative cooling and humidification of air and vegetation. • The problem of unsealed road surfaces (such as water-bound surfaces) drying out during heat waves, which affects their stability and lifespan.

[0006] 4. The Invention: The underlying innovation is an unbound base course whose properties significantly exceed conventional requirements. Its unique feature is the ability to absorb rainwater decentrally in a quantity compatible with construction principles, to temporarily store a relevant amount of water, and to release it upwards again towards the surface (for example, via intermediate or surface layers) during dry periods. This creates a sustainable water cycle and increased evaporation capacity in the blue-green infrastructure, with the added benefit of enhanced evaporative cooling.

[0007] The capillary storage layer consists of various coordinated mineral and, if necessary, supplementary materials that exhibit different properties regarding hardness, shape, and surface structure (smooth / closed or porous / porous). For load-bearing capacity and the aggregate structure, natural or inert materials / aggregates such as crushed stone, chippings, crushed sand, gravel, natural sands, and / or materials from concrete or asphalt recycling or other recycled materials are used. For water-retaining and capillary-active properties, mineral materials such as coarse and fine silt, graded sands, volcanic porous rocks (e.g., tuff, lava), expanded porous materials (e.g., expanded clay), and / or suitable organic or textile aggregates can be used.

[0008] The invention fulfills the following technical objectives and performance characteristics: • Grain size distribution: 0 / 32-0 / 45 mm, for layer thicknesses less than 12 cm possibly also 0 / 22 mm. • Load-bearing capacity: A deformation modulus EV2 of at least 80 MN / m 2 , or 100 MN / m 2 for regularly used areas. • Water permeability: A permeability coefficient of at least Kf >= 3 × 10^-3 cm / s. • Water capacity (water storage capacity against gravity): >= 12 vol.%. • Capillary action (capillary suction): Minimum increase of +3 wt% water content to 20 cm layer thickness, and of +5 wt% to 12 cm layer thickness (with slightly damp starting material with 4% initial water content and Proctor density 100%). • Layer thickness: The capillary action should be achieved for layer thicknesses of up to 20 cm. This results, for example, in road construction, in a system structure of approximately 25-40 cm together with overlying layers. • Resistance and durability: High resistance and durability of the materials under stress and weather conditions, as well as stability during wet / dry cycles. • Frost resistance: Maximum possible frost resistance, although 100% frost protection is not required (as it is designed for unsealed structures without a rigid top layer). Maximum vertical expansion due to frost at an installation thickness of 20 cm: 0.5 cm. • Environmental compatibility: Groundwater protection and minimal environmental impact; ensuring that collected water is not contaminated by materials and that no harmful chemicals are released. • Stability of aggregates: The grain stability of a large proportion (at least 80 vol.%) of the inert or mineral aggregates must meet the following criteria according to TL Gestein-StB (based on the aggregate content >2 mm): SZ value: <= 28, LA value: <= 35.

[0009] 5. Industrial Applicability: The invention is industrially applicable due to its use in road construction / civil engineering for unsealed, open-pored surfaces such as water-bound surfaces, clay courts, gravel lawns, grass grid or honeycomb systems, and sports fields. It offers economic efficiency through a longer service life of the infrastructure and reduced maintenance costs, since unsealed surfaces function significantly better in moderately moist conditions than in dry conditions. Indirect cost savings also result from reduced seepage water in the subsoil. The creation of attractive and naturally designed environments is facilitated by the reduction in drying, leading to aesthetic advantages.

[0010] 6. Advantageous effects of the invention: The capillary storage base layer surpasses the state of the art (conventional unbound base layers, which are primarily designed for rapid drainage) significantly through its additional storage function for rainwater in line with the sponge city concept.

[0011] The beneficial effects are as follows: • Reduction of the burden on the sewage system: Rainwater is absorbed and stored directly on site. • Reduction of seepage water volumes during prolonged periods of precipitation, especially in densely populated areas. • Improved water quality through stronger filtration of the outflow. • Sustainable management of water resources: Return of water through capillary rise and evaporation during dry periods. • Improvement of the urban climate: Support of evaporative cooling, humidification of plants and promotion of the microclimate. • Economic efficiency: Longer lifespan of the road infrastructure and lower maintenance costs. • Aesthetic advantages: Facilitating the realization of attractive and naturally designed urban environments, as the problem of drying out, which increasingly occurs due to heat waves, is reduced.

[0012] In comparison to existing sponge city concepts, the specific innovation lies in the novelty of not only draining water, but also returning a relevant amount of water to the urban air and living space at the same location through capillary transport.

[0013] 7. Detailed description of how to implement the claimed invention: The capillary storage base course is constructed by specifically selecting and mixing its materials and adhering to technical parameters. It is used as a base course in non-rigid road structures under open-pore surfaces (e.g., water-bound surfaces, gravel turf). It is produced by mixing mineral and, if necessary, supplementary materials that possess the required properties for load-bearing capacity (gravel, chippings, crushed sand, etc.) and for water storage and capillarity (silt, sand, volcanic rocks, expanded clay, organic aggregates, etc.). The precise particle size distribution is based on the grading curves 0 / 32–0 / 45 mm or 0 / 22 mm according to TL-SoB StB, but allows deviations of up to 5 percentage points, particularly in the fine and medium-grained range.The material composition and installation must be carried out in such a way as to ensure the required values ​​for load-bearing capacity (deformation modulus EV2), water permeability (Kf value), water capacity (Wk), and in particular the capillary action (see above target criteria), as well as the resistance, durability, and the above relative frost resistance. The layer thickness can be up to 20 cm. The materials used must also be environmentally compatible and meet the required stability criteria (SZ value, LA value). QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited non-patent literature

[0000] https: / / www.gruen-in-die-stadt.de / schwammstadt /

[0005] https: / / neuelandschaft.de / artikel / kopenhagen-vorreiter-beim-thema-ueberflutungsvorsorge-3350

[0005]

Claims

[1] Capillary storage base course, a base course without binder (based on ‘ToB’ as defined in the applicable TL SoB-StB or EN 13285) for unsealed, open-pored surfaces in road construction / civil engineering, characterized by that it is designed to absorb rainwater decentrally in a structurally acceptable quantity, to temporarily store a relevant amount of water and to release it again upwards towards the surface via capillary action when dry. [2] Base layer according to claim 1, characterized by that it consists of various coordinated mineral and, where applicable, complementary substances that have different properties with regard to hardness, shape and surface structure. [3] Base layer according to claim 2, characterized bythat natural or inert materials such as gravel, chippings, crushed sand, pebble material, natural sands and / or materials from concrete or asphalt recycling or other recycled materials are used for the load-bearing capacity and the grain structure. [4] Base layer according to claim 2 or 3, characterized by , that mineral materials such as coarse and fine silt, graded sands, volcanic porous rocks (e.g. tuff, lava), expanded porous materials (e.g. expanded clay) and / or suitable organic or textile additives are used for the water-storing and capillary-active properties. [5] Base layer according to any one of the preceding claims, characterized by , that their grain size distribution is 0 / 32-0 / 45 mm, whereby a grain size distribution of 0 / 22 mm may also be provided for layer thicknesses of less than 12 cm. [6] Base layer according to any one of the preceding claims, characterized bythat, when installed, they have a deformation modulus EV2 of at least 80 MN / m 2 achieved, or of at least 100 MN / m 2 for regularly used areas. [7] Base layer according to one of the preceding claims, characterized by that, when installed, it has a water capacity (water storage capacity against gravity) of at least 12 vol.%. [8] Base layer according to any one of the preceding claims, characterized by that, when installed, it has a capillary action that allows a minimum increase of +3 wt% water content to 20 cm layer thickness or of +5 wt% to 12 cm layer thickness (based on approximately 4% initial water content). [9] Base layer according to any one of the preceding claims, characterized by , that effective capillarity is ensured at least up to a layer thickness of 20 cm. [10] Base layer according to any one of the preceding claims, characterized by, that the grain stability of a large part (at least 80 vol.%) of the inert or mineral aggregates meets the following criteria according to TL Gestein-StB: impact crushing value less than or equal to 28 and Los Angeles coefficient less than or equal to 35 (each according to DIN EN 1097-2, measured on the specified aggregate grain fraction).