NL2017166B1

NL2017166B1 - Laid-out area foundation layer system containing a layer of bottom ash particles for liquid drainage, infiltration, storage and/or reuse

Info

Publication number: NL2017166B1
Application number: NL2017166A
Authority: NL
Inventors: Petrus Van Vliet Joannes
Original assignee: Suez Recycling & Recovery Nederland B V
Priority date: 2016-07-14
Filing date: 2016-07-14
Publication date: 2018-01-18

Abstract

The present invention is in the field of civil engineering and concerns a layer system for use as foundation for a laid-out area, comprising at least one layer of bottom ash particles, wherein the layer system is located under a part or the whole surface of a laid-out area and wherein at least 80 wt% of the bottom ash particles have a size in the range from 2 mm to 50 mm. The layer system according to the invention is particularly suitable for liquid, such as rainwater, drainage, infiltration, storage and/or reuse.

Description

Laid-out area foundation layer system containing a layer of bottom ash particles for liquid drainage, infiltration, storage and/or reuse [0001] The present invention relates to the technical field of civil engineering, more in particular the construction of laid-out areas, especially sport and urban areas, and to sustainable resource management. It combines the useful application of otherwise unusable waste products with sustainable management of a liquid resource that comes into contact with the surface of laid-out areas, draining and infiltrating the liquid, while enabling storage and reuse of such liquid.

Background [0002] Current aspects of environmental concern are the increasing energy consumption and increasing waste production from an ever-growing world population. The International Energy Statistics published by the US Energy Information Administration indicate that in 2012 the world consumed a total of 8,186,103,000 Short Tons (approximately 7,500 billion kg) of coal. According to a 2013 Nature paper (vol. 502, issue 7473, pages 615-617), waste production will peak this century, expecting a daily production of 6 million tonnes of solid waste per day by 2025. To deal with the waste problem, much effort is made to find new and useful applications for waste, one of them being waste-to-energy (WtE) or energy-from-waste (EfW) plants, which in turn address part of the energy demand problem. WtE plants produce electricity and/or heat directly through combustion of (municipal) solid waste, just like coal fired power plants do by combusting coal.

[0003] A problem associated therewith is that both coal fired power plants and WtE plants are examples of major producers of bottom ash, respectively coal bottom ash and WtE bottom ash. Bottom ash is part of the non-combustible residue of combustion e.g. in a furnace or incinerator, meaning that combustion yields yet another waste product. The coal and WtE bottom ash yielded is a granular material. In the case of coal bottom ash it comprises mainly ash from burnt materials, in the case of WtE bottom ash it further contains a mix of inert materials such as sand, stone, glass, porcelain, metals etc.

[0004] To reduce environmental burden, practical uses for coal and WtE bottom ash are highly sought after. If permitted by national legislation, coal and WtE bottom ash is nowadays applied as a fill material in road construction, as a foundation and fill material in all works involving large areas of asphalt pavement and where there is no danger of direct contact with groundwater (e.g. huge car parks or large store hangars), in construction of noise barriers, as an aggregate in asphalt and concrete and as for capping dumping grounds where waste materials are disposed for storage purposes. The bottom ash grain sizes used in these applications always range from a lower limit of 0 mm to an upper limit that varies among nations. Denmark, for instance, uses 0-50 mm well-graded bottom ashes; for Sweden this is 0-45 mm and for Spain 0-40 mm. Granova, a product made by Heros Sluiskil, The Netherlands, for applications in concrete or asphalt, contains WtE bottom ash particles having sizes 0-11.2 mm. W02014013515 describes a composition comprising WtE bottom ash, at least 2 wt% of at least one stabilizing additive comprising an alkali or alkaline earth silicate and at least one alkali or alkaline earth sulphide or phosphate. It mentions admixing WtE bottom ash particle sizes of 0.1 mm - 10 mm with said additive to obtain a final composition with a particle size comprised between 30 and 100 microns, which can be conveniently used as a recycled material for the preparation of: mortars, concrete, tiles, edges, surfaces of squares, road bases, street curbs, grouts, plasters and the like.

[0005] A problem associated with applying such bottom ash fractions as used in the art is that when it becomes wet by coming into contact with a liquid, it will lose support and pressure strength and will become sloppy. This still poses disadvantages for maintaining ground integrity and stability in the current applications of bottom ash in ground structures. For example, during and after rain falls, it is currently a problem to have an adequate water management (e.g. drainage, infiltration, preventing of flooding), while maintaining the same pressure strength of the ground as under dry conditions.

[0006] Also, with regard to the wettening of the laid-out area by liquid, depending on the type of laid-out area, there are different needs to be met. On one hand, in some laid-out areas it is undesirable to have liquid coming into contact with the surface and are preferably dry. When these laid-out areas are exposed to liquid, e.g. during rain falls, they require for adequate drainage and infiltration. Other laid-out areas, especially sports fields, parks or playgrounds such as tennis and athletics courts, field hockey fields, golf courts, soccer, and football fields, etc, need a certain degree of moisture in order to create a perfect playing field. Still another group of laid-out areas, such as urban areas, are exposed to heat and ways to reduce (urban) heating e.g. with a heat absorbing liquid such as water, would be desirable. Dealing with liquid coming into contact with the surface of a laid-out area has the challenge of meeting these laid-out area dependent requirements while maintaining the soil’s pressure strength and preventing the soil from becoming sloppy upon moisturization, which currently happens to sand-based laid-out areas and laid-out areas applying bottom ash size fractions used in the art. Since the vast majority of laid-out areas, including sport fields, are built on a sand layer, these disadvantages are commonly faced. Also Desso AquaMaster, a water management system for field hockey fields known in the art, uses sand as a base.

[0007] In a world where currently much concern is given to the environment and natural resources become scarce, there is a need for sustainable solutions. It is thus highly desirable that the drained liquid from the areas often exposed to said liquid is not wasted, but is stored and reused in some way as a useful resource.

[0008] KR2014000880 describes a method for drainage in ground cross-sections having a top soil layer of 300 mm thick by using bottom porous bioceramic ash aggregate gravel, containing large amounts of minerals and having efficient permeability. KR2014000880 shows a tank basin below the ground cross-section to store water and a recycling water pipeline running from the tank basin to the surface of the ground.

[0009] A drawback of using bottom porous bioceramic ash aggregate gravel, is its porous, bioceramic nature, implying that the aggregate material has poor toughness and abrasion characteristics. The bottom porous, bioceramic ash is thus relatively easily crushed and desintegrates when pressure is applied on it, meaning that it will provide low support and pressure strength when used in ground structures, posing disadvantages for maintaining ground integrity and stability. To alleviate these disadvantages in part, a relatively thick soil layer is currently applied on top of the bottom porous, bioceramic ash, which top soil layer will then receive and intercept the largest part of the pressure applied on the ground, so that the lower lying bottom porous bioceramic ash is less exposed to the applied pressure and loss in stability and integrity is minimized.

[0010] The present invention provides a solution to prevent the sloppiness and low pressure strength, integrity and stability of a ground structure with a bottom ash foundation layer, in dry form and upon coming into contact with liquid or upon moisturization. This is realized all at the same time while providing for excellent drainage and infiltration properties when used in laid-out areas exposed to liquid and for liquid storage and reuse properties. Like this, the present invention makes it possible to meet all types of needs of laid-out areas: the laid-out areas that require to be dry are adequately drained, the laid-out areas that require a certain degree of moisture, such as sports fields, playgrounds or parks, may be remoisturized with liquid stored and recycled to the laid-out area and the heat may be absorbed by the stored liquid for laid-out areas exposed to heat, such as urban areas. The liquid may also be stored and reused for energy production purposes, e.g. electrolysis. These functional uses of the stored liquid meet the general need for sustainable use of resources.

Summary of the invention [0011] The invention relates to a laid-out area and a layer system that forms the foundation for a laid-out area and is located under a part or the whole surface of a laid-out area comprising at least one layer of bottom ash particles for liquid drainage, infiltration, storage and/or reuse, to a method for constructing a laid-out area according to the invention and to the use thereof.

[0012] The inventors surprisingly found that by using a bottom ash fraction from which the bottom ash particles having sizes smaller than about 2 mm are substantially absent, in a layer system that is located under a part or the whole surface of a laid-out area, the properties when coming into contact with liquid drastically change. In the art, bottom ashes are always applied including the smallest bottom ash particles having sizes of 0 - 2 mm (also called ‘the sand fraction’ or ‘bottom ash fines’) and the larger bottom ash particles having sizes of 2 mm and up (also called ‘bottom ash granulate fraction’). The inventors surprisingly found that bottom ash layers used as foundation, not comprising the 0-2 mm fraction, remain rigid and firm and keep their pressure strength and stability upon loading. Even more surprising, all these features were maintained and even improved upon moisturizing, i.e. when substantial amounts of water are present within the layer of bottom ash particles. As such, the construction integrity and stability of the laid-out area is guaranteed even at high liquid moisture levels. Without wishing to be bound by a theory, the inventors believe that when liquid permeates the surface of the laid-out area and enters the layer of bottom ash according to the invention, and increases the grain pressure of the bottom ash particles, causing a force in upwards direction, towards the surface and thereby increasing the strength of the construction.

[0013] An important technical contribution made by the present invention is the capability of liquid drainage, infiltration, storage and/or reuse by a layer system being located under a part or the whole surface of a laid-out area all while at least substantially maintaining its pressure strength, whether the at least one bottom ash layer in said layer system is in dry form, at maximal liquid storage capacity or at any liquid level in between. This means that the layer does not become sloppy or unstable, making it possible to use the laid-out area for any application desired, including those that impose a heavy load on the area, such as construction, transportation, building and so on. The layer system according to the invention thus serves multiple uses at the same time: as a foundation and as a liquid management system (for drainage, infiltration, storage and/or reuse). A further advantage is that a cheap, abundantly available waste material is used in the present invention: bottom ash, thereby providing a practical and handy application for waste and alleviating the environmental burden. Yet another advantage is that the layer system according to the present invention succeeds in quickly and easily draining and infiltrating liquid from the surface of the laid-out area, thereby serving areas where exposure to liquid is undesirable and areas that are exposed to excess liquid. The invention thus serves to prevent flooding of the laid-out area, for liquid removal from the surface of the laid-out area, or for regulating the moisture level of the laid-out area.

[0014] A further advantage of the layer system according to the invention is that its total weight is less compared to foundation layers of bottom ash from which the particles having a size below 2 mm are not substantially removed. This reduced weight leaves more room to load the laid-out area, e.g. by building heavier structures or by storing heavier vehicles. In other words, the total weight of the vehicles parked on a laid-out area can be higher when the layer system according to the invention is used as foundation. Further, the reduced weight enables storage of liquid without the need of additional constructive elements, as the total weight of a (partly) liquid-filled layer system according to the invention has more or less the same weight as conventional foundations in the absence of liquid. The inventors have found that the weight can be reduced from about 1750 kg/m3 for regular bottom ash to about 1550 kg/m3 for the layer of bottom ash particles according to the invention (determined using NEN-EN 1097-3).

[0015] Yet another advantage of the layer system according to the present invention is that it is capable of storing significant amounts of liquid and that this liquid storage occurs within the at least one layer of bottom ash particles comprised in the layer system, so that there is no need for further technical means such as tank basins or other collecting means to collect and store the liquid, thereby saving technical efforts, time and costs in constructing the laid-out area according to the invention. A further advantage of the invention is that the stored liquid can be reused. This enables sustainable use of the liquid as resources are not wasted and costs are kept low. For sport fields, parks and playgrounds where a certain level of moisture is required for a perfect playing field, such as field hockey fields, soccer and football fields, tennis courts, golf courts, athletics courts, paddocks, etc, this is an outcome: liquid may be stored in the layer system according to the invention, which forms at least part of the foundation of the sport field, park or playground, and the liquid may be removed from the layer of bottom ash particles and recycled to the surface of the sport field, park or playground for irrigation whenever this is desired, such as for regulating the desired moisture level or during dry weather circumstances. As such, a sustainable way of recycling liquid is provided. It is also envisionable to transport the liquid stored in the layer system according to the invention to other parts of the laid-out area or to other laid-out areas nearby for irrigation or regulating the desired moisture level, preferably under dry weather circumstances. This enables a redistribution of moisture from one (part of a) laid-out area to another (part of a) laid out area. This is advantageous if for instance a certain (part of a) laid-out area comes in contact with a lot of rain, whereas another (part of a) laid-out area is less exposed to rain, so that the first laid-out area receives an excess liquid, while the other is too dry. Such situations may for example occur following (heavy) rain falls in one (part of a) laid-out area, while the other (part of a) laid-out area has less (heavy) rain falls. For areas exposed to heat, such as urban areas, storing liquid in the layer system according to the invention is also an outcome: the liquid may be used to absorb heat and thus reduce the temperature of the environment, e.g. for reducing urban heating. For areas where energy generation is necessary, the invention also provides an outcome: the liquid stored in the layer system according to the invention may be used for energy generation, e.g. via electrolysis. If the liquid stored in the layer system according to the invention originates from a natural source, such as water, typically water from rain, snow, hail, ground water, river water, creek water, lake water and/or sea water, most preferably water from rain, snow and/or hail, an even more sustainable application of the invention is achieved for the sport fields, parks, playgrounds and urban areas described above as no resources are wasted and cost is reduced.

List of preferred embodiments 1. Layer system that forms the foundation for a laid-out area, comprising at least one layer of bottom ash particles for liquid drainage, infiltration, storage and/or reuse, wherein the layer system is located under a part or the whole surface of a laid-out area and wherein at least 80 wt% of the bottom ash particles have a size in the range from 2 mm to 50 mm. 2. Layer system according to embodiment 1, wherein at least 80 wt% of said bottom ash particles have a size in the range from 2 mm to 45 mm, preferably 2 mm to 16 mm. 3. Layer system according to embodiment 1 or 2, wherein at least 85 wt%, preferably 90 - 98 wt% of the bottom ash particles have a size in said range. 4. Layer system according to any one of the preceding embodiments, wherein less than 20 wt%, preferably less than 10 wt%, most preferably 2-8 wt% of the bottom ash particles have a size smaller than 2 mm. 5. Layer system according to any one of the preceding embodiments, where the bottom ash particles are formed by bottom ash particles obtained from a furnace or incinerator from which the particles having a size below 2 mm are substantially removed. 6. Layer system according to any one of the preceding embodiments, wherein the layer of bottom ash particles comprised in the layer of bottom ash have a coefficient of uniformity Cu in the range of 1.5 - 10. 7. Layer system according to any one of the preceding embodiments, wherein the layer of bottom ash particles has a thickness of 10 - 100 cm, preferably 25 - 60 cm, more preferably 30 - 45 cm. 8. Layer system according to any one of the preceding embodiments, wherein the bottom ash is bottom ash from waste-to-energy plants, preferably incineration bottom ash. 9. Layer system according to any one of the preceding embodiments, wherein the layer of bottom ash particles has a liquid storage capacity relative to said layer’s volume of at least 5%, preferably at least 10%, more preferably at least 20%. 10. Layer system according to any of the preceding embodiments, wherein the bottom ash particles have a Los Angeles coefficient of 60 or lower, preferably in the range of 10 - 40, more preferably in the range of 30 - 38. 11. Layer system according to any one of the preceding embodiments, further comprising a liquid-impermeable layer, preferably a water-impermeable foil, located under at least part of the at least one layer of bottom ash particles. 12. Layer system according to any one of the preceding embodiments, further comprising a pump capable of removing liquid from the layer of bottom ash particles for reuse of said liquid. 13. Layer system according to any one of the preceding embodiments, wherein the laid-out area is a soil, grass, paved, asphalt, and/or gravel area, more preferably a sport field, playground, park, urban ground, road, street, lane, trail, promenade, parking area and/or square. 14. A laid-out area, comprising the layer system according to any one of embodiments 1-13, wherein the layer system is located under at least a part of the surface of the area. 15. Use of the layer system according to any one of embodiments 1 - 14 as foundation of at least part of a laid-out area. 16. Use according to embodiment 15, where the laid-out area is a soil, grass, paved, asphalt, and/or gravel area, more preferably a sport field, playground, park, urban ground, road, street, lane, trail, promenade, parking area and/or square. 17. Use according to any one of embodiments 15 - 16, which is for liquid drainage, infiltration, storage within the layer of bottom ash particles and/or reuse of a liquid. 18. Use according to any one of embodiments 15 - 17, which is for preventing flooding of the laid-out area, for liquid removal from the surface of the laid-out area, and/or for regulating the moisture level of the laid-out area. 19. Use according to embodiment 17, which is for reuse, wherein reuse involves removal of the liquid from the layer of bottom ash particles and recycling thereof to the surface of the laid-out area and/or transported to another (part of) the laid-out area, where it is preferably used for irrigation, more preferably for regulating the moisture level of the laid-out area. 20. Use according to embodiment 17, which is for reuse, wherein reuse involves removal of the liquid from the layer of bottom ash particles and use thereof for energy production, preferably by electrolysis. 21. Use according to embodiment 17, which is for reuse, wherein reuse involves storing the liquid within the layer of bottom ash particles and us thereof for heat absorption, preferably for reduction of urban heating. 22. Use according to any one of embodiments 15-21, wherein the liquid is water, even more preferably water from rain, snow, hail, ground water, river water, creek water, lake water and/or sea water, most preferably water from rain, snow and/or hail. 23. Method for constructing a laid-out area, comprising: - providing a layer system according to any one of embodiments 1 - 13 to obtain a foundation for the laid-out area; and - providing the surface of the laid-out area on top of at least part of the foundation. 24. Method according to embodiment 25, wherein the laid-out area is a soil, grass, paved, asphalt, and/or gravel area, more preferably a sport field, playground, park, urban ground, road, street, lane, trail, promenade, parking area and/or square.

Detailed description [0016] The term about’ is used to indicate deviations from the value specified, which fall within the error margin of practising the invention and which the skilled person would readily recognize and at forehand expect that they do not affect the technical result. Typically, ‘about’ means a deviation of ±5% of the value specified.

[0017] The term ‘substantially’ in the context of ‘substantially maintains’ is used to indicate that the value specified stays approximately the same. This means that deviations are possible to the extent that they do not significantly and practically change the technical result. Typically, ‘substantially’ in the context of ‘substantially maintains’ means that the value minimally stays 90% the same. In the context of the present invention, “substantially absent” or “substantially removed” typically means that at most 10 wt% of the specified component is present or remains, unless indicated otherwise.

[0018] With the term “size” or “particle size” of the bottom ash particles in the context of the invention is meant the average diameter of said particles as obtained by sieving analysis of the bottom ash fraction. Sieving analysis may also be referred to as gradation test, and is well-known in the field of civil engineering. Suitably, the NEN-EN 933-1 test is used. Preferably, sieves having a sieve size of 2 mm, 4 mm, 8 mm, 16 mm, 22.4 mm and 31.5 mm are used.

[0019] The invention concerns a layer system that is especially suited to form a foundation of laid-out areas such as (sports)fields and urban areas. The layer system is typically located under a part or the whole surface of a laid-out area and is suitable for liquid drainage, infiltration, storage and/or reuse. The layer system comprises at least one layer of bottom ash particles, wherein the bottom ash particles comprises less than 20 wt%, preferably less than 10 wt%, more preferably bottom ash particles having sizes smaller than about 2 mm. Preferably, at least 80 wt% of the bottom ash particles have a size in the range of 2 - 50 mm. In one embodiment, 2-8 wt% of the bottom ash particles have a size smaller than 2 mm. In one embodiment, less than 5 wt%, more preferably less than 3 wt%, even more preferably less than 1 wt% have a size outside the range of 2 - 50 mm. Consequently, the at least one layer of bottom ash particles typically comprises at least 80 wt% of the bottom ash particles having sizes in a range from at least about 2 mm to about 50 mm, more preferably at least about 2 mm to about 40 mm, even more preferably at least about 2 mm to about 35 mm, even more preferably at least about 2 mm to about 25 mm, even more preferably at least about 2 mm to about 20 mm, most preferably at least about 2 mm to about 16 mm. Preferably at least 80 wt% of the bottom ash particles have sizes in said range, more preferably at least 85 wt%. In one embodiment, 90 - 98 wt% of the bottom ash particles have a size in said range. In one embodiment, at least 90 wt%, even more preferably at least 95 wt%, at least 96 wt%, at least 97 wt%, at least 98 wt%, at least 99 wt% and most preferably 100 wt% of the bottom ash particles have a size in said range.

[0020] Methods of separating bottom ash particles in size fractions are known in the art to the skilled person. As an example in this context, US20140202931 describes a process to separate bottom ash from the WtE industry in fractions of <0.75 mm (comprising the less soluble metals); < 2 mm but > 0.75 mm (comprising soluble non-ferrous metals, subject to restricted disposal) and > 2 mm - 6 mm (comprising removable ferrous and non-ferrous metals, glass, aggregates, minerals, partially incinerated debris).

[0021] The upper limits of the bottom ash particle sizes are not particularly important for executing the present invention and are typically limited by national regulations. However, in case larger sized bottom ash particles, say above 50 mm in size, are used in at least one layer of bottom ash particles in a layer system located under a part or the whole surface of a laid-out area, more coarse irregularities may be created in the surface of the laid-out area. This may be experienced as undesirable and uncomfortable for use of the area. Alternatively, this may require applying a (thick) cover layer between the at least one bottom ash layer in the layer system and the surface of the laid-out area to level the irregularities. However, this may have a negative effect on the liquid drainage and infiltration properties of the at least one bottom ash layer in the layer system. Also, using an additional or thicker cover layer in the layer system comes at extra resources and costs. Consequently, it is preferred that the at least one bottom ash layer in the layer system according to the invention is located directly under a part or the whole surface of a laid-out area. In other words: it is preferred that there are no other layers located between the surface of the laid-out area and the at least one bottom ash layer. In case an intermediate layer would be applied, this layer is preferably kept as thin as possible.

[0022] Regarding the distribution of bottom ash particle sizes in the at least one layer of bottom ash particles comprised in the layer system according to the invention, it is preferred that the layer of bottom ash particles has a uniform or homogeneous or normal distribution of bottom ash particle sizes throughout said layer. This may also be referred to as a homogeneous mixture of bottom ash particles.

[0023] Particle size distributions are typically defined by the coefficient of uniformity (Cu = Ü60 / Dio) and the coefficient of curvature (Cc = (D30)2 / (D10 * Deo); also referred to as the coefficient of graduation). Herein, Dy represents the diameter of the sieve through which y wt% of the particles pass. The bottom ash particles in the layer of bottom ash particles preferably have a broad particle size distribution within the preferred range of particle sizes. Such is broad distribution is highly preferred, since it typically comes naturally from the used bottom ash. As such, only the fraction of small particles below 2 mm of size need to be substantially removed, but no further selection within the remaining bottom ash particles is required. As such, the bottom ash fraction that is to be employed in the layer of bottom ash particles is easily obtained. Moreover, it is preferred that the bottom ash particles of different sizes are uniformly distributed throughout the layer of bottom ash particles. The broad particle size distribution is reflected in values for Cu, which is preferably in the range of 1.5 - 10, more preferably in the range of 1.8 - 8, more preferably in the range of 2 - 5, most preferably in the range of 2.4 - 3. Lower Cu values would mean a very uniform and narrow particle size distribution, which would require additional selection of a very specifically sized bottom ash particle fraction, whereas higher values would correspond to much too broad particle size distributions, i.e. bottom ash particle fractions from which the smallest particles are not removed. The value for Cc is preferably close to 1, such as in the range of 0.5 - 3, more preferably 0.8 - 1.5, most preferably 1-1.2. As such, all particles sizes within the desired range of bottom ash particle size are more or less equally present in the bottom ash particle fraction to be used in the layer of bottom ash particles.

[0024] Alternatively or additionally, the bottom ash particle fraction present in the layer of bottom ash particles comprises 0-20 wt%, preferably 1-5 wt% of particles having a size in the range of 16 - 31.5 mm, 10 - 50 wt%, preferably 20 - 40 wt% of particles having a size in the range of 8 - 16 mm and 40 - 90 wt%, preferably 55 - 75 wt% of particles having a size in the range of 2 - 8 mm. Such particle size distributions and Cu and Cc values as defined above are typically obtained from the naturally present particle size distribution of bottom ash, from which the particles having a size of below 2 mm are substantially removed and optionally the particles having a size of above 30 mm are ground, and without further alteration of the bottom ash particle size distribution. Thus, in one embodiment, the bottom ash particles are obtained from a furnace or incinerator from which the particles having a size below 2 mm are substantially removed.

[0025] The layer system according to the invention may for example comprise up to 25, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2 or 1 layer(s) of bottom ash particles according to the invention. Preferably the layer system according to the invention comprises one layer of bottom ash particles.

[0026] It is preferred that the at least one bottom ash layer in the layer system according to the invention contains bottom ash which is bottom ash from waste-to-energy plants, also called WtE bottom ash. More preferably said bottom ash or said WtE bottom ash is bottom ash from incineration plants, also referred to as incinerator bottom ash (IBA). Preferably the bottom ash in the at least one bottom ash layer in the layer system according to the invention contains at least 50% WtE bottom ash relative to the total bottom ash content in the layer, more preferably, at least 60%, even more preferably at least 70%, 80%, 90%, 95% or 100%. Most preferably the only bottom ash in the at least one bottom ash layer in the layer system according to the invention is bottom ash from waste-to-energy plants. Bottom ash from coal fired power plants, also called coal bottom ash or E-bottom ash, may also be used, but is more expensive than WtE bottom ash. In dry form, coal bottom ash typically has a smaller hardness value, a smaller toughness value and smaller pressure strength than WtE bottom ash. WtE bottom ash also achieves better technical results in the current invention than coal bottom ash with regard to its liquid management properties. In one embodiment, the bottom ash particles are not bioceramic. The preferred embodiment of using WtE bottom ash in the layer system that forms the foundation for a laid-out area and is located under a part or the whole surface of a laid-out area, thus provides better constructional stability and integrity for using the laid-out area, also when the laid-out area is exposed to liquid and thus allows for the laid-out area to have a wider range of applications and possible constructions.

[0027] For measuring toughness and abrasion characteristics of particles, such as bottom ash particles, the Los Angeles (L.A.) coefficient is used. It shows how much the particles can resist crushing, degradation and disintegration. To determine the Los Angeles coefficient, the standard Los Angeles abrasion test is used, most suitably NEN-EN 1097-2. Preferably, the bottom ash particles in the at least one layer of bottom ash particles in the layer system according to the invention have a Los Angeles coefficient of 60 or lower, preferably in the range of 10 - 40, more preferably in the range of 30 - 38. The advantageous L.A. coefficient of the bottom ash particles comprised in the layer system according to the invention ensures that said bottom ash particles have good toughness and abrasion characteristics. The bottom ash particles according to the invention are thus relatively difficult to crush and consequently do not disintegrate when pressure is applied on them, meaning that the bottom ash particles according to the invention will provide excellent support and pressure strength when used in ground structures or foundations such as the layer system according to the invention. This advantageously makes it possible to maintain ground integrity and stability, without necessitating the application of a (thick) soil layer on top of the highest bottom ash particle layer in the layer system, since said bottom ash particle layer will be able to receive and intercept the largest part of the pressure applied on the ground by itself, both without and with storing liquid according to the invention described herein. Accordingly, it is preferred that the at least one bottom ash layer in the layer system according to the invention is located directly under a part or the whole surface of a laid-out area, preferably under the (whole of) the laid-out area. In other words: it is preferred that there are no other layers located between the surface of the laid-out area and the at least one bottom ash layer. By not requiring and not using a (thick) cover layer between the at least one bottom ash layer in the layer system and the surface of the laid-out area, extra resource and monetary cost for the extra material are saved. Also, any possible negative effect on the liquid drainage and infiltration properties of the at least one bottom ash layer in the layer system is prevented.

[0028] The bottom ash particles in one or more of the at least one layer of bottom ash particles in the layer system according to the invention may also be mixed with (minor amounts of) other materials, such as lava, rubber, although this is not preferred. Preferably at least 50 wt% of one or more of the at least one layer of bottom ash particles in the layer system according to the invention contains bottom ash, more preferably at least 60 wt%, even more preferably at least 70 wt%, 80 wt%, 90 wt%, 95 wt%, most preferably 100 wt% of said layer is formed by (i.e. consists of) bottom ash particles. With the highest content of bottom ash particles, the best drainage, infiltration, storage and/or reuse of liquid is achieved. Accordingly, it is preferred that the bottom ash used in the present invention is not mixed with other materials.

[0029] The at least one layer of bottom ash particles in the layer system according to the invention preferably has a thickness of at least 10 cm, such as at least 25 cm. In one embodiment, the thickness is in the range of about 10 cm to about 100 cm, preferably about 20 cm to about 80 cm, more preferably about 25 cm to about 70 cm, most preferably about 25 cm to about 60 cm, especially about 25 cm to 50 cm, or even about 30 cm to about 45 cm. Any intermediate layer that may be present in the layer system according to the invention directly below the laid-out are is preferably at most 100 cm thick, more preferably 1 - 25 cm, most preferably 1 - 5 cm thick.

[0030] In a preferred embodiment, at least one further layer is placed on the surface of the laid-out area according to the invention. The at least one further layer may be a (sport) field, a (urban) ground or a civil engineering structure, such as synthetic grass, natural grass, gravel, sand, soil, asphalt, brick, cobbled stones, grinded stones, dust etc. Preferably the at least one other layer is permeable to liquid, more preferably to the liquid as defined herein.

[0031] In the context of the invention, preferably the liquid is water, even more preferably water from rain, snow, hail, ground water, river water, creek water, lake water and/or sea water, most preferably water from rain, snow and/or hail.

[0032] The laid-out area according to the invention may be exposed to liquid. Preferably the surface of the laid-out area is permeable to liquid, preferably liquid according to the invention, in at least one area of the surface. More preferably the at least one area of the surface that is permeable to said liquid is located above the layer system according to the invention, most preferably above one or more of the at least one layer of bottom ash particles according to the invention. As such, said liquid may permeate the surface of the laid-out area and come into contact with the layer system, more specifically with one or more of the at least one layer of bottom ash particles according to the invention. Said liquid will then reside or be retained within the layer system, more specifically within one or more of the at least one layer of bottom ash particles according to the invention. Preferably said liquid is stored in the layer system, more specifically in one or more of the at least one layer of bottom ash particles according to the invention. Accordingly, the layer system according to the invention does not require and preferably does not comprise a tank, collector, basin or other collecting means to store liquid.

[0033] The layer system according to the invention, more specifically, the at least one layer of bottom ash particles has a surprisingly high liquid storage capacity. Typically, each layer of bottom ash particles comprised in the layer system according to the invention has a liquid storage capacity relative to said layer’s volume of at least 5%, preferably at least 10%, more preferably at least 15, even more preferably at least 20%, most preferably at least 25% or at least 30%. The liquid storage capacity may be as high as 40 vol% or higher.

[0034] In one embodiment, the layer system according to the invention further comprises a liquid-impermeable layer, preferably a liquid-impermeable foil, more preferably a water-impermeable foil, located under at least part of the at least one layer of bottom ash particles. Any type of water-impermeable layer known in the art to be suitable in this respect can be used, including EPDM rubber, a layer of bentonite and concrete foundations. Conveniently, a layer of EPDM rubber is used. Said liquid impermeable layer may have smaller, the same or larger dimensions than said layer of bottom ash particles, which dimensions may be in height, length and thickness. The liquid impermeable layer serves to prevent the liquid that entered the layer system according to the invention, more specifically, the at least one layer of bottom ash particles, from the surface of the laid-out area from moving further through said layer system or said layer of bottom ash particles. If that would happen, the liquid would eventually end up in further ground layers and will get lost, which could be useful for some but not all applications. The liquid impermeable layer thus makes it possible to retain the liquid for a longer time period in the layer system according to the invention, more specifically in the at least one layer of bottom ash particles. This is advantageous for applications of liquid storage and/or reuse. Preferably said liquid storage occurs when the surface of the laid out area comes into contact with the liquid, more preferably during wet weather circumstances, such as during rain, snow and/or hail or during flooding, such as from a river, creek, lake or sea. The liquid may be removed or recovered from the layer system according to the invention, more specifically from the at least one layer of bottom ash particles, for example by using a pump. Consequently, in an embodiment, the layer system according to the invention further comprises a pump suitable for removing or recovering liquid from one or more of the at least one layer of bottom ash particles for reuse of said liquid, more preferably for pumping the liquid to the surface of the laid out area.

[0035] The reuse may be recycling of the liquid to the surface of the laid-out area or transporting the liquid to at least one other part of the laid out area or to at least one other laid-out area for irrigation or (re)moisturizing said surface, more preferably for regulating the moisture level of the laid-out area or other laid-out area, most preferably during dry weather circumstances. The embodiment where said liquid is transported to at least one other part of the laid out area or to at least one other laid-out area enables a redistribution of moisture from one (part of a) laid-out area to another (part of a) laid out area. This is advantageous if for instance there is a lot of liquid that comes into contact with a certain (part of a) laid-out area, but less liquid comes into contact with another (part of a) laid-out area, so that the first laid-out area receives an excess liquid, while the other is too dry. Such situations may for example occur following (heavy) rain falls in one (part of a) laid-out area, while the other (part of a) laid-out area has less (heavy) rain falls.

[0036] The reuse may also be using the liquid for energy production, preferably by electrolysis.

[0037] The reuse may also be, keeping or storing the liquid within the layer system, according to the invention, more specifically, within the at least one layer of bottom ash particles, for heat absorption, preferably for urban heat reduction.. Laid-out areas that need a certain degree of moisturization, such as sport fields, parks or playgrounds, e.g. field hockey fields, tennis courts, soccer and football fields, golf courts, athletics courts, paddocks, and laid-out areas where heat needs to be reduced and/or energy is needed, such as urban areas, e.g. roads, squares, parking areas etc, may suitably apply this embodiment. Especially preferred are water-based hockey fields, which require extensive irrigation before they can be played upon.

[0038] In another embodiment, said liquid impermeable layer is absent. In this embodiment, the liquid that entered the layer system according to the invention, more specifically, the at least one layer of bottom ash particles, from the surface of the laid-out area will move further through said layer system or said layer of bottom ash particles, eventually end up in further ground layers and get lost. This makes it possible to quickly transport liquid away from the surface of the laid-out area. This is advantageous for applications of liquid drainage and infiltration, e.g. for preventing flooding of the laid-out area, for liquid removal from the surface of the laid-out area, or for regulating the moisture level of the laid-out area. Laid-out areas that are exposed to liquid or are exposed to excess liquid and/or where it is undesirable to have or retain said liquid may suitably apply this embodiment. Examples are areas where (heavy) rain falls often occur, areas that are prone to flooding etc.

[0039] The advantage of the layer system according to the present invention, more specifically, of the at least one layer of bottom ash particles, is that it at least substantially maintains its pressure strength upon coming into contact with or storing of liquid. In an embodiment, the pressure strength of said layer system or layer of bottom ash particles increases upon coming into contact with or storing of liquid. Preferably pressure strength of the layer system or of one or more of the at least one layer of bottom ash particles is at least substantially maintained or increased when one or more of the at least one layer of bottom ash particles stores at least 5%, preferably at least 10%, more preferably at least 15, even more preferably at least 20%, most preferably at least 25% or at least 30% of liquid. These percentages are relative to the volume of the layer of bottom ash particles storing said liquid.

[0040] More preferably pressure strength is at least substantially maintained or increased when one or more of the at least one layer of bottom ash particle stores maximally about 100%, more preferably maximally about 90%, 80%, 70%, 60%, 50%, most preferably maximally about 40% of liquid relative to said layer’s volume. In an embodiment each layer of the at least one layer of bottom ash particles in the layer system according to the invention stores said liquid; in another embodiment one single layer stores said liquid, in yet another embodiment two or three layers store said liquid. This means that even at maximal liquid storage capacity of the layer system according to the present invention, more specifically, of the at least one layer of bottom ash particles, it remains stable. This makes the ground integrity of the laid-out area reliable under all circumstances (with or without liquid exposure) for constructions, transportation or other applications that pose heavy load on the surface of the laid-out area.

[0041] In order for bottom ash particles to be applied in a layer system according to the invention that is located under a part or the whole surface of a laid-out area, the used fraction of said bottom ash particles suitably complies with national regulations. Since the layer system according to the invention is to be used as a foundation located in the ground, care must be taken not to harm the environment. Consequently, amongst others, a point of attention is the content of contaminating substances in the bottom ash fraction, such as heavy metals, metals and minerals. These values are typically according to the legal requirement (e.g. BRL 2307-1 in The Netherlands). Preferably, the layer system according to the invention and each of the at least one layer of bottom ash particles complies with the legislations and regulations for open application.

[0042] The layer system according to the invention is preferably applied in a laid-out area which is a field, soil, grass, paved, asphalt, and/or gravel area, more preferably a sport field, playground, park, garden (including roof garden), urban ground, cultivation floor, road, street, lane, trail, promenade, parking area and/or square. The grass may be natural or synthetic grass. The sport field, playground and/or park may be a paddocks, a soccer, football, hockey, golf, athletics and/or tennis field.

[0043] Preferably in the layer according to the present invention the liquid is water, even more preferably water from rain, snow, hail, ground water, river water, creek water, lake water and/or sea water, most preferably water from rain, snow and/or hail.

[0044] Another aspect of the present invention is a laid-out area comprising the layer system according to the invention, wherein the layer system is located under at least a part of the surface of the area. The laid-out area is preferably a field, soil, grass, paved, asphalt, and/or gravel area, more preferably a sport field, playground, park, garden (including roof garden), urban ground, cultivation floor, road, street, lane, trail, promenade, parking area and/or square. The grass may be natural or synthetic grass. The sport field, playground and/or park may be a paddocks, a soccer, football, hockey, golf, athletics and/or tennis field.

[0045] Further aspects of the present invention relate to the use of a layer system or laid-out area according to the invention. In the context of the invention, said uses are equivalent to methods for achieving the same purposes, comprising a method step of providing a layer system according to the invention located below at least part of a laid-out area.

[0046] An aspect of the invention is the use of the layer system according to the invention as foundation of at least part of a laid-out area. The laid-out area is preferably a field, soil, grass, paved, asphalt, and/or gravel area, more preferably a sport field, playground, park, garden (including roof garden), urban ground, cultivation floor, road, street, lane, trail, promenade, parking area and/or square. The grass may be natural or synthetic grass. The sport field, playground and/or park may be a paddocks, a soccer, football, hockey, golf, athletics and/or tennis field.

[0047] The invention also relates to the use of the layer system or laid out area according to the invention for drainage, infiltration, storage within the layer of bottom ash particles and/or reuse of a liquid. In an embodiment, said use or said drainage and/or infiltration is for preventing flooding of the laid-out area, for liquid removal from the surface of the laid-out area, or for regulating the moisture level of the laid-out area. Preferably said liquid storage occurs when the surface of the laid out area comes into contact with the liquid, more preferably during wet weather circumstances, such as during rain, snow and/or hail or during flooding, such as from a river, creek, lake or sea. In another embodiment, said use or said storage and/or reuse is that the liquid is removed or recovered from the layer of bottom ash particles and recycled to the surface of the laid-out area or transported to at least one other part of the laid-out area or to at least one other laid-out area for irrigation or moisturization, more preferably for regulating the moisture level of the laid-out area or other laid-out area, most preferably during dry weather circumstances.

[0048] The embodiment where said liquid is transported to at least one other part of the laid out area or to at least one other laid-out area enables a redistribution of moisture from one (part of a) laid-out area to another (part of a) laid out area. This is advantageous if for instance there is a lot of liquid that comes into contact with a certain (part of a) laid-out area, but less liquid comes into contact with another (part of a) laid-out area, so that the first laid-out area receives an excess liquid, while the other is too dry. Such situations may for example occur following (heavy) rain falls in one (part of a) laid-out area, while the other (part of a) laid-out area has less (heavy) rain falls.

[0049] In another embodiment, said use or said storage and/or reuse is that the liquid is removed or recovered from the layer of bottom ash particles and used for energy production, preferably by electrolysis. In yet another embodiment, the storage and/or reuse is that the liquid is stored within the layer of bottom ash particles and used for heat absorption, preferably for reduction of urban heating. Preferably the heat absorption occurs in the liquid in the at least one layer of bottom ash particles in the layer system.

[0050] Preferably for the uses according to the invention, the liquid is polar, preferably aqueous, more preferably water, even more preferably water from rain, snow, hail, ground water, river water, creek water, lake water and/or sea water, most preferably water from rain, snow and/or hail.

[0051] For removing or recovering liquid from the layer of bottom ash particles, the uses according to the invention preferably use a pump, more preferably for pumping the liquid to the surface of the laid out area.

[0052] The invention further relates to a method for constructing a laid-out area, comprising: - providing a layer system according to the invention to obtain a foundation for the laid-out area; and - providing the surface of the laid-out area on top of at least part of the foundation.

[0053] The laid-out area is preferably a field, soil, grass, paved, asphalt, and/or gravel area, more preferably a sport field, playground, park, garden (including roof garden), urban ground, cultivation floor, road, street, lane, trail, promenade, parking area and/or square. The grass may be natural or synthetic grass. The sport field, playground and/or park may be a paddocks, a soccer, football, hockey, golf, athletics and/or tennis field.

[0054] The method according to this aspect may further comprise a step of excavating a laid-out area before providing the layer system according to the invention as foundation. The method according to this aspect may further comprise a step of providing an intermediate layer, as defined herein, on top of at least part of the layer system according to the invention and then providing the surface of the laid-out area on top of at least part of the intermediate layer. The method according to this aspect may further comprise a step of providing a liquid-impermeable layer, as defined herein, below at least part of the layer system according to the invention and then providing the layer system according to the invention on top of at least part of the liquid-impermeable layer.

Examples

Example 1: Preparation and characteristics of the bottom ash layer [0055] A batch of bottom ash originating from a waste incineration plant was conventionally treated, i.e. removal of large (metallic) pieces, conventional washing steps were performed and large pieces of > 40 cm were grated, and the fraction of bottoms ash particles having a size of below 2 mm was removed by sieving. The particle size distribution of the thus obtained bottom ash fraction is determined by sieve analysis (NEN-EN 933-1) and provided in the table below (“Invention”) and compared to the particle size of a conventional bottom ash fraction which has not been subjected to the sieving step (“Control”). Values for Cu and Cc, obtained from the sieving analysis, are also provided.

Example 2: Evaluation of strength [0056] A field was excavated (4 x 4 m, 40 cm depth), lined with water-permeable geotextile and filled with the inventive bottom ash particles fraction according to example 1 and then condensed with a vibrating plate and levelled. The strength of the finished field was tested by loading it with trailer (weight 6 tonne). Various experiments were performed with large amounts of simulated rainwater (using a hose, buckets) to test the water infiltration rate and surface appearance. Buckets of 10 L water emptied on one spot in about 10 seconds with simultaneous loading (a person was standing on the location the bucket was emptied) does not show any loss in strength or stiffness of the foundation. Not even the slightest movement of the field was observed. Splashing of water was minimal, in view of the characteristic angular shape of the bottom ash particles. No puddles were formed.

Example 3: Evaluation of water retention

The top was removed from an IBC (size = 1 * 1 * 1 m = 1.000 L), which was then filled with the inventive bottom ash particles fraction according to example 1 (90 cm high, i.e. 0.9 m3), equipped with an infiltration pipe (Wavin, 100 cm long and a diameter of 30 cm). On the bottom ash particles a layer of foam (ProPlay Sport, Schmitz Foam Products) on top thereof an artificial turf (water-based hockey pitch, Greenfield Evolution). Within the infiltration pipe, a butt-pump system equipped with a timer is mounted, which is connected to a garden shower set (Gardena). The overflow of the IBC was connected to an external container (Kliko). The set-up was filled with 360 L tap water (i.e. 40 vol% of the layer of bottom ash particles) and located outside exposed to rain and the like. Twice a day, water from the bottom of the IBC was pumped through the infiltration pipe and the garden shower and sprayed for 15 minutes over the artificial turf. This set-up ran stably and without problems for more than 3 months already, and continues to run. The amount of water that could be retained in the bottom ash layer, amounted to at least 40 % of the total volume of bottom ash particles, without the formation of permanent puddles. No discolouring of the artificial turf by e.g. iron oxides (red) or lime (white) was observed during the entire duration of the experiment.

Claims

Amended Conclusions [unmarked]

A layer system which forms the basis for an engineered area, comprising at least one bottom ash particle layer for drainage, infiltration, storage and / or reuse of liquid, the layer system being located under a part or all of the surface of an engineered area, wherein at least 80% by weight of bottom ash particles have a size in the range of 2 mm - 50 mm; and wherein the bottom ash particle fraction present in the bottom ash particle layer comprises: 0-5% by weight of particles with a size in the range of 16 - 31.5 mm, 20 - 50% by weight of particles with a size in the range of 8-16 mm and 40 - 90% by weight of particles with a size in the range of 2-8 mm.

Layer system according to claim 1, wherein at least 80% by weight of the bottom ash particles have a size in the range of 2 mm - 45 mm, preferably 2 mm - 16 mm

3. Layer system according to claim 1 or 2, wherein at least 85% by weight, preferably 90 to 98% by weight of the bottom ash particles have a size in said range.

A layer system according to any one of the preceding claims, wherein less than 20% by weight, preferably less than 10% by weight, most preferably 2-8% by weight of the bottom ash particles have a size smaller than 2 mm.

A layer system according to any one of the preceding claims, wherein the bottom ash particles are formed by bottom ash particles obtained from an oven ("furnace") or incinerator ("incinerator") from which the particles with a size below 2 mm are substantially removed.

6. A layer system according to any one of the preceding claims, wherein the bottom ash particles included in the bottom ash particles layer have a coefficient of uniformity Cu in the range of 1.5-10.

A layer system according to any one of the preceding claims, wherein the bottom ash layer has a thickness of 10 - 100 cm, preferably 25 - 60 cm, more preferably 30 - 45 cm.

A layer system according to any one of the preceding claims, wherein the bottom ash is waste power plant bottom ash, preferably incinerator bottom ash.

9. Layer system as claimed in any of the foregoing claims, wherein the bottom ash particle layer has a liquid storage capacity relative to the volume of the layer of at least 5%, preferably at least 10%, more preferably at least 20%.

A layer system according to any one of the preceding claims, wherein the bottom ash particles have a Los Angeles coefficient of 60 or lower, preferably in the range of 10-40, more preferably in the range of 30-38.

A layer system according to any one of the preceding claims, further comprising a liquid-impermeable layer, preferably a water-impermeable film, which is located under at least a part of the at least one bottom ash particle layer.

A layer system according to any one of the preceding claims, further comprising a pump suitable for removing fluid from the bottom ash particle layer for reuse of the fluid.

A layer system according to any one of the preceding claims, wherein the landscaped area is earth, grass, paved, asphalt and / or gravel, more preferably a sports field, playground, park, built-up area, road, street, avenue, path, promenade, parking lot and / or square.

An engineered area comprising the layer system of any one of claims 1 to 13, wherein the layer system is located below at least a portion of the surface of the area.

Use of the layer system according to one of claims 1 to 13 as the foundation of at least a part of an engineered area.

The use according to claim 15, wherein the landscaped area is earth, grass, paved, asphalt and / or gravel, more preferably a sports field, playground, park, built-up area, road, street, avenue, path, promenade, parking lot and / or or square.

The use according to any of claims 15-16, which is for drainage, infiltration, storage in the bottom ash particle layer and / or reuse of liquid.

The use according to any of claims 15 to 17, which is for preventing flooding of the applied area, for liquid removal of the surface of the applied area and / or for regulating the moisture content of the applied area.

The use of claim 17, which for reuse, wherein reusing comprises removing the liquid from the bottom ash particle layer and recycling it to the surface of the engineered area and / or transported to another (part of the) engineered area, where the is preferably used for irrigation, more preferably for regulating the moisture content of the landscaped area.

Use according to claim 17, which is for reuse, wherein reuse comprises removing the liquid from the bottom ash particle layer and using it for energy production, preferably by electrolysis.

The use according to claim 17, which is for reuse, wherein reuse comprises storing the liquid in the bottom ash particle layer and using it for heat absorption, preferably for reducing city heating.

Use according to any of claims 15-21, wherein the liquid is water, even more preferably rain, snow or hail water, ground water, river water, stream water, lake water and / or sea water, most preferably rain, snow and / or hail water.

A method for constructing an engineered area, comprising: - providing a layer system according to any of claims 1-13 to obtain a foundation for the engineered area; and - providing the surface of the landscaped area on top of at least a portion of the foundation.

Method according to claim 23, wherein the landscaped area is earth, grass, paved, asphalt and / or gravel, more preferably a sports field, playground, park, built-up area, road, street, avenue, path, promenade, parking area and / or or square.