Method for managing inert waste of construction site and construction site

Abstract

A process for managing inert waste and soil from construction sites, comprising, on a first treatment area (2), the collection (5) and screening of clean inert waste and the pre-screening (3) of soily inert waste with the removal (F1) of the collected soil to a second treatment area (4), where there is a collection (19) of soil from external construction sites (17) and soil from the pre-screening (3), drying of the soil carried out under cover (23) which allows for the collection (28) of rainwater, and separate collection of leachate (34) from wet soil and, on a third treatment area (9), mixing (10) of a hydraulic binder with mixing water and aggregates formed from the screened inert waste (F2), recovery of wastewater from washing tools (14),said mixing and washing waters being formed at least partially from rainwater collected by the shelter cover (23), a separation (15) of the wastewater from washing (14) between a basic aqueous phase and a solid phase (16) and a recycling (F3) of the basic aqueous phase back to mixing and / or washing and a return (F4) of the solid phase back to the inert waste collection stage (5).

Description

[0001] The present invention relates to a method for managing inert waste and earth from construction sites.

[0002] It is known that during a demolition site, a lot of construction waste is produced, such as possibly reinforced concrete, tarmac, mixed waste, bricks, stones, etc. A simple landfill of this bulk waste is currently no longer feasible, beyond the fact that landfilling mixed waste is very expensive. Therefore, they are previously sorted (see for example EP1647331A1), because some of them can be revalued, such as scrap metal or certain stones. Waste is therefore classified and stored, then delivered for revaluation in the form of raw materials intended to be used elsewhere in the composition of new products.

[0003] On the other hand, it is also known that all earthworks require large movements of earth, whether in the form of excavation or embankment. Several of the aforementioned inert wastes can also be mixed with large proportions of earth, while some soils can still be used as arable land. Currently, it is planned to sort between recoverable soils that are stored on large areas and possibly treated for recovery by users and non-compliant soils that must then be removed to specialized treatment units.

[0004] The aim of the invention is to provide a method for managing inert construction site waste and earth from construction sites in a way that allows for the re-use of several of these wastes and earths, a reduction in their transport costs, and the exploitation of several of them on site close to their treatment and storage with simultaneously complementary water management that allows for the avoidance as much as possible of water consumption from the distribution network and environmental pollution.

[0005] This problem is solved according to the invention by a method for managing inert waste and earth from construction sites, comprising on a first treatment area, a collection of inert waste classified into several clean inert wastes, having less than 10% by weight of earth, and into several earthy inert wastes, which may contain up to 50% by weight of earth, a pre-screening of each of the earthy inert wastes with an evacuation of the collected earths towards a second treatment area close to the first treatment area and intended for an implementation of said earth management method, and a possible recovery of the pre-screened inert wastes in the clean inert waste, a crushing of each of the clean inert wastes, and a screening of each of the crushed clean inert wastes, in order to calibrate them and / or to separate different granulometric fractions, and a storage of each of these screened inert wastes, on said second treatment area,a collection of soil from external construction sites and said soil harvested during the aforementioned pre-screening stage, a separation and storage of arable land with a view to its departure, the land management process then including a) screening of remaining soils with return of the stones (21) resulting from this screening to the aforementioned collection step of the inert waste management process, and liming of the screened soils allowing storage of limed soils, and / or b) storage of remaining soils in the form of unlimed soils, and natural drying of said limed or unlimed soils carried out sheltered from the rain under a cover which allows collection of rainwater, a separate collection of leaching water from wet soils being carried out during the natural drying under said shelter, and on a third treatment area adjacent to the other two treatment areas, mixing mixing (10) of a hydraulic binder with mixing water and aggregates as well as possibly other concrete production components, with a view to departure of the produced concretes (12), aggregates being formed from said screened inert waste stored (F2), as gravel,gravels, grit and sand, washing of the mixing and transport tools with washing water, recovery of the washing waste water, said mixing and washing water being formed at least partially from said rain water collected by said shelter cover provided for said natural drying of the land, separation of the washing waste water between a basic aqueous phase and a solid phase comprising recovered aggregates and fresh concrete residues, and recycling of the basic aqueous phase to the mixing step and / or the washing step and return of the solid phase to said inert waste collection step.

[0006] It is known that concrete production is carried out in what is called a concrete production plant. According to the invention, this plant takes advantage of the interconnection of the three aforementioned neighboring treatment areas. The third treatment area is provided with at least one mixer in which water, aggregates and various additives are mixed with a hydraulic binder depending on the concrete to be produced. Aggregates, such as sand, chippings, gravel and gravel of various particle sizes are produced here inside the plant and can therefore be consumed directly for the production of concrete in the plant itself.

[0007] Concrete manufacturing facilities are used to supply products of several types, such as concretes meeting the specifications of the Bénor brand or rich concretes known as "on composition", lean concretes, or various mixtures based on cement and aggregates such as stabilized stone, stabilized sand, Rhine sand screeds, specific concretes (road, cavernous, etc.). Special admixtures are sometimes requested. Said other concrete production components include, for example, pigments, synthetic or metallic fibers, various admixtures or their mixture. Increasingly, it is sought to be able to recycle certain materials already previously used in concrete. According to the invention, these materials are therefore already available on site and do not require expensive transport costs for their reuse in the mixers.

[0008] Furthermore, the soils obtained by pre-screening certain inert earth wastes can be immediately transferred to the soil treatment area without requiring expensive transport costs. The production and consumption of concrete induce a high consumption of water, on the one hand for the production of the concrete itself and on the other hand for washing the mixing tools and transport tools. By transport tools we mean the tanks, pumps, pipes or trucks that are used to transport concrete and similar products to their destination of use. In a concrete plant, the wastewater consists mainly of the wash water from the installation's mixers and from the inside of the tanks of the mixer trucks transporting the produced concrete to their operating site. This wash water contains residual aggregates as well as fresh concrete residues.This wastewater cannot therefore be discharged as is into nature. According to the invention, not only is the basic liquid phase (pH of the order of 11-13) of the wastewater reused as is, but the solid waste from the mixing is also recovered on site by returning it to the first treatment area where the collection of the inert waste management process takes place.

[0009] The basic liquid phase of the wash water alone is not sufficient to provide the water needed for both concrete production and tool washing. It is of course necessary to constantly add fresh water to the circuit.

[0010] Advantageously, at least the natural drying stage is carried out sheltered from the rain under a roof covering which allows rainwater to be collected. The use of this rainwater allows fresh water to be introduced into the process water circuit, which makes it possible to compensate, with the recycled basic aqueous phase, for the consumption of water used to react, for example, with a hydraulic binder during the manufacture of concrete. For this purpose, said rainwater can be advantageously collected in a retention basin before use. Rainwater collected regularly with each downpour, in particular using the cover sheltering the soil stored for natural drying, therefore represents a significant addition which makes it possible to avoid, as far as possible, an external water supply.

[0011] The shelter provided to the stored soil for drying also prevents rainwater from percolating through the soil and eventually reaching the soil or even the water table in a contaminated state.

[0012] On the other hand, the soils brought to the stage of natural drying under cover can be very wet. Potentially contaminated water, called leaching water, then percolates through them. The method according to the invention comprises a separate collection of leaching waters from wet soils during drying, advantageously with a view to allowing their analysis, and this to prevent the penetration of these waters into the soil or even the water table.

[0013] According to one embodiment of the invention, the clean inert waste is classified into concrete waste, tarmac or hydrocarbon waste, mixed waste and natural stone, each of these wastes being able to undergo the crushing and screening stages independently. After screening, it is possible to obtain clean inert waste having several particle size sizes, corresponding or not to current standards, for example 0 / 80, 0 / 63, 31.5 / 63, 63 / 150, 0 / 20, 0 / 6.3, 6.3 / 20 etc., which will then be used independently depending on the finished product to be produced. These values ​​define the mesh openings of the sieves used to produce the particle sizes and are to be expressed in mm.

[0014] According to a particular embodiment of the method of the invention, before the step of crushing the clean inert waste, it comprises isolation of reinforced concrete waste from which scrap metal is separated and then stored with a view to dispatch, for example to a scrap metal dealer or a steelworks.

[0015] According to an advantageous embodiment of the invention, the step of separating the wash water consists of decanting this water in a settling tank, drawing off the supernatant aqueous phase and extracting the decanted solid phase formed from said recovered aggregates and fresh concrete residues. Drawing off can be carried out by any means known for this purpose, for example by pumping or using an overflow. Extraction of the solid phase can be envisaged for example by an Archimedes screw or by dredging using a bulldozer. Any other known means of separation can obviously also be envisaged, such as for example filtration.

[0016] In the event of drought, dust waves may be carried by the wind from the inert waste stored in the first treatment area. Advantageously, according to the invention, rainwater may be spread on the dusty roads of the treatment areas, in particular between the first and second treatment areas, in particular using a towed tank filled with rainwater collected by said shelter cover.

[0017] Other details and advantages of the present invention will emerge from the description given below, without limitation, and with the aid of the appended figures. There figure 1 schematically represents an example of an embodiment of a concrete production installation in which a method according to the invention is implemented. The figure 2 represents a perspective view of a drying hall for the earth treated according to the invention. The figure 3 represents a sectional view of the floor of the hall of the figure 2 .

[0018] In the installation illustrated on the figure 1 Inert waste 1 from deconstruction sites or certain earthworks sites, for example containing a lot of natural stone, is entered in a classified manner into the treatment area 2. For example, concrete waste, tarmac waste, mixed waste such as bricks or plastics, and stones can be piled up separately in the collection area 5, provided that they contain less than 10% earth. This waste is called clean waste. Earthy waste containing more than 10% and up to a maximum of 50% by weight of earth is transferred and pre-screened in a pre-screening step 3. The material formed from the pre-screened earth is then, following arrow F1, removed by truck or simply by bulldozer to the nearby treatment area 4 which is intended for the management of earth from earthworks sites.The waste retained during pre-screening and therefore freed from soil is returned to the corresponding clean waste piles in collection area 5.

[0019] The waste from each of the clean waste piles, or at least from some of these piles, is then subjected to crushing using a conventional crusher 6. In the case of reinforced concrete waste, the scrap metal separated at this time is, for example, piled up in a container and removed. On the figure 1 , reference 8 illustrates all the starting products, i.e. those leaving the installation from treatment area 2. The scrap metal mentioned previously is therefore part of these products 8.

[0020] Each of the crushed wastes is then passed through one or more successive screens 7, in order to calibrate them and / or separate different granulometric fractions such as those already mentioned previously.

[0021] In a nearby treatment area 9, the installation illustrated on the figure 1 comprises at least one concrete plant intended to produce various concretes and similar products such as stabilized sands, stabilized stone, etc. To do this, the plant comprises at least one mixer 10 which must be supplied with several incoming components 11, in particular at least one hydraulic binder, water and aggregates, stones or sands. These concretes will require, depending on their destination or quality, the use of various aggregates, stones or sands with appropriate granulometries. These, in the process according to the invention, can be taken, at the appropriate size, from the calibrated inert waste piled up at 7 on the treatment area 2, as illustrated by arrow F2.

[0022] Some of these aggregates, stones or sands calibrated in 7 can also be directed towards the starting products 8 for their exploitation in external installations.

[0023] Other input components 11 may be provided for mixing concrete, such as pigments, synthetic or metallic fibers, various additives, etc. Aggregates of external origin to the installation according to the invention may also be considered as input components 11.

[0024] At the exit of the treatment area 9, the starting products 12 are obtained, usually from a concrete plant, which are then removed or delivered outside.

[0025] The mixer 10, but also all the tanks, pumps, pipes or trucks used for the delivery of concrete must be regularly washed with water. On the figure 1 , this washing step is represented globally by block 13 where washing water, introduced into the plant as input component 11, is used for this purpose. The washing wastewater 14 from this step is collected and discharged into a settling tank 15. From the latter, the supernatant liquid phase having a pH of 11-13 is extracted for example by an overflow system and, according to the invention, it is recycled as is, along arrow F3, among the input components 11 of the plant. A settled solid phase is regularly extracted from the settling tank 15, for example by an Archimedes screw, and piled up at 16. This solid phase is formed of recovered aggregates and fresh concrete which have not been carried away in the mass of concrete produced and have continued to adhere for example to the walls of the mixer or the mixer trucks intended for transporting the concrete.According to the invention, these recovered aggregates and these fresh concrete residues piled up at 16 are returned, following arrow F4, to the treatment area 2, in particular to the collection space 5, in particular to the corresponding pile of inert waste, i.e. the concrete waste. According to the invention, the dangers of pollution of the environment or of the water table at the outlet of the concrete plant are avoided since all the usual liquid or solid residues are reused.

[0026] In the installation illustrated on the figure 1 , the incoming products 17 brought to the treatment area 4 are mainly earth from earthworks sites. In general, after a certain control or analyses, certain earths are rejected because they do not comply or do not correspond to various administrative standards. The lands which can still be considered arable are separated. Reference 18 represents all the starting products, i.e. leaving the installation from the treatment area 4 in particular for external exploitation. Arable lands are therefore part of these products 18.

[0027] Following arrow F1, the pre-screened soils in 3 on the inert waste treatment area 2 are, as previously described, grouped in 19 in isolation in the treatment area 4 with the earthworks from the incoming products 17.

[0028] Among the incoming products 17, the presence of lime must also be considered, because, in the treatment area 4, certain earths will be limed. To do this, certain earths piled up at 19 are subjected to one or more successive screens 20, in particular to remove any stones they may contain and pile them up at 21. The screened earths are then limed in a mixer 22, then sent to a drying hall 23.

[0029] Other soils piled up in 19 are not screened or limed and are sent directly to the drying stage in hall 23.

[0030] After drying, these limed or unlimed soils are now finished products which can be considered as starting products 18 to be used outdoors.

[0031] The stones piled up at 21 are, following arrow F5, regularly returned to the inert waste treatment area 2, in particular to the collection area 5, in particular to the corresponding inert waste pile, i.e. the piles of stones.

[0032] Drying Hall 23 is shown in more detail on the figures 2 et 3 . In the example illustrated it comprises a metal frame 24 which supports a roof covering 25 below which the earth to be dried can be piled up to protect it from the rain. A cladding 26 can be mounted at the top of the lateral sides of the hall to increase the effectiveness of this shelter. Below these claddings 26 it is also possible to provide windbreak nets 27 which allow both ventilation of the hall and protection against driving rain. The roof covering 25 is provided with a standard drainage system which channels the rainwater towards a retention basin 28. The rainwater thus collected can be stored to be used in particular as water for the manufacture of concrete and / or for washing the concrete mixing and transport tools. For this purpose, the water from the retention basin 28 is, following the arrow F6, introduced into the plant as an incoming component 11.The concrete plant in treatment area 9 can then, under favorable conditions, become self-sufficient in its water supply.

[0033] As illustrated on the figure 3 , in hall 23, the earth to be dried is piled up on a concrete slab 29 sloping slightly outwards. It is surrounded by concrete plinths 30 so as to form a tank which is sealed by a membrane 31. This slab advantageously rests on a stabilized material 32, itself arranged on a stone base 33. The leaching water which percolates through the earth during its stay under the shelter of hall 23 cannot penetrate into the soil or the water table. It is collected separately in a collection basin 34 where it can possibly be analyzed before evacuation or treatment.

[0034] In the event of drought, streams of dust may be carried by the wind from the inert waste stored in the first treatment area 2. Advantageously, according to the invention, spreading on the roads of the installation may be carried out judiciously using rainwater collected in the retention basin 28, for example using tanker trucks.

[0035] It should be understood that the present invention is not limited to the illustrated embodiment and that many modifications may be made thereto without departing from the scope of the claims.

Claims

1. Method for managing inert waste products and soil from construction sites, comprising in a first treatment area (2), a collection (5) of inert waste products (1) classified into various clean inert waste products, having less than 10% by weight of soil, and into various earthy inert waste products, which may contain up to 50% by weight of soil, a pre-screening (3) of each of the earthy inert waste products with a removal (F1) of the collected soil to a second treatment area (4) adjacent to the first treatment area and intended for the implementation of said soil management method, and the possible recovery of the pre-screened inert waste products in the clean inert waste products, a crushing (6) of each of the clean inert waste products, and a screening (7) of each of the crushed clean inert waste products, in order to calibrate them and / or separate different granulometric fractions, and a storage of each of these screened inert waste products, on said second treatment area (4), a collection (19) of soil from external construction sites (17) and of said soil collected during the aforementioned pre-screening step (3), a separation and a storage of arable soil with a view to its departure (18), the soil management method then comprising a. a screening (20) of the remaining soil with the return of the stones (21) resulting from this screening to the aforementioned collection step of the inert waste management method, and the liming (22) of the screened soil allowing for the storage of limed soil, and / or b. a storage of the remaining soil in the form of unlimed soil, and natural drying of said limed or unlimed soil carried out while sheltered from the rain under a cover (23) that allows for a collection (28) of rainwater, a separate collection of leaching water (34) coming from wet soil being carried out during the natural drying under said shelter, and on a third treatment area (9) adjacent to the two other treatment areas, a mixing (10) of a hydraulic binder with mixing water and aggregates as well as optionally other concrete production components, with a view to removing the concretes produced (12), with aggregates being advantageously formed from said stored screened inert waste (F2), as gravelly soil, gravel, chippings and sand, a washing (13) of mixing and transport tools with washing water, and a recovering of washing wastewater (14), said mixing and washing water being formed at least partially from said rainwater collected by said shelter cover (23) provided for said natural drying of the soil (F6), a separation (15) of the washing wastewater (14) into a basic aqueous phase and a solid phase (16) comprising recovered aggregates and fresh concrete residues, and a recycling (F3) the basic aqueous phase towards the mixing step and / or the washing step and a return (F4) of the solid phase to said inert waste collection step (5).

2. Method according to claim 1, characterised in that the clean inert waste is classified into concrete waste, tarmac or hydrocarbon waste, mixed waste and natural stone waste, each of these waste products separately undergoing the steps of crushing and screening.

3. Method according to either of claims 1 and 2, characterised in that said other concrete production components comprise pigments, synthetic or metallic fibres, various additives or a mixture thereof.

4. Method according to any one of claims 1 to 3, characterised in that, before the step of crushing (6) the clean inert waste, it comprises an isolation of reinforced concrete waste from which scrap metal is separated and then stored for removal (8).

5. Method according to any one of claims 1 to 4, characterised in that the step of separating (15) the used washing water (14) consists of decanting this water in a decantation tank, withdrawing the supernatant aqueous phase and extracting the decanted solid phase formed from said recovered aggregates and fresh concrete residues.

6. Method according to any one of claims 1 to 5, characterised in that said rainwater collected by said shelter cover (23) provided for the natural drying of the soil is collected in a retention basin (28) before its use.

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