SK24993A3 - Substance for creation multipurposed barrier contrary to contamination and method of creation this barrier - Google Patents

Abstract

Composition based on water, cement and clay, making it possible to produce a durable barrier against the diffusion of polluting substances consisting of metal cations, especially of heavy metals and/or of toxic organic products. It additionally comprises active carbon and a soluble basic salt capable of buffering the aqueous phase of the composition at a pH of at least 9 for a period of at least about ten years.

Description

BACKGROUND OF THE INVENTION The present invention relates to a composition for forming a multipurpose anti-fouling barrier and a method of forming such a barrier.

The state of the art

It is known that in most cases the polluting waste is stored on pile covered with soil. Around these heaps, it is necessary to build barriers to prevent leakage of waste, especially into groundwater.

It is also known that polluting waste is principally divided into two types, namely cations of heavy metals, which may be radioactive, and, on the other hand, toxic organic compounds.

From FR 81 / 21.025 an injection mortar is known which can be used to form protective walls in the soil against the spread of radioactive waste consisting of a mixture of water, cement, clay and silica (silica). If the silica is formed by at least partially fly ash, it is further known according to this patent to add to the mixture sodium carbonate, which acts as a clay deflocculant and a silicon dioxide activator.

However, these known compositions do not make it possible to form effective barriers against organic pollutants.

Patent FR 84/11863 discloses a mortar allowing the formation in the soil of walls which prevent or retard the migration of metal cations. This mortar consists of water, cement, clay, silica. sodium carbonate and sodium pyrophosphate and / or potassium tartrate. On the one hand, the presence of sodium carbonate and, on the other hand, potassium pyrophosphate and / or potassium tartrate allows the formation of insoluble compounds, while sodium carbonate simultaneously acts as a silica activator.

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A disadvantage of known masses of this type is. that after a longer or shorter time they lose their effectiveness.

Patent FR 90/00087 also discloses a material useful in the soil for forming walls capable of preventing or retarding the spread of toxic organic substances, consisting of a mixture of water, cement or hydraulic binder. bentonite and activated carbon.

SUMMARY OF THE INVENTION

The subject of the invention is a water, cement and clay based material. allowing the formation of a long-lasting barrier against the spreading substances formed by both metal cations, especially heavy metals, and organic products. The essence of this composition is that it further comprises activated carbon and a soluble basic salt capable of buffering the aqueous phase of the composition to a pH of at least 9 for at least about 10 years.

The aqueous phase of the mass is understood to be the interstitial liquid which remains in the mass after inducing its solidification and forming a barrier against contamination.

According to the invention, the basic salt must, on the one hand, maintain a pH greater than 9 in the aqueous phase and, on the other hand, must be present in the mass in sufficient concentration to provide this function for at least 10 years, preferably 50 to 100 years.

The activated carbon may be of a known type according to the invention, for example a CECA product sold under the name Aktlcarbon TK.

The buffer salt of the invention may be formed, for example, by sodium carbonate or sodium bicarbonate (Na 2 CO 3 or NaCl 3). which is present or further burnt or slaked lime (CaO or CA10H12) in an amount sufficient to provide a buffering effect.

The weight ratios of the components of the mass according to the invention are preferably as follows ^:

Water 1000 cement or binder 40 until 2000 clay 25 until 1000 activated carbon 5 until 500 soluble buffer salt of pH> 9 ³⁰ until 500

According to the invention, the composition may optionally contain silica. for example, sublimed silica or fly ash, for example in a weight ratio of 25 to 1500 kg per 1000 L of water. This additive makes it possible, as is known, to reduce the permeability of the mass.

The composition according to the invention may further comprise known additives, for example wetting agents, such as naphthalenesulfonate, in a weight ratio of up to 20 kg per 1000 l of water, or retardants, such as sodium ignosulfonate, in a weight ratio of up to 50 kg per 1000 l of water, or plasticizers. a water-reducing product such as the product sold by Chryso under the name Cerplast, in a weight ratio of up to 30 kg per 1000 l of water.

The liner according to the invention may also contain salts, precipitating metal cations, such as sodium tartrate and / or sodium pyrophosphate, in a weight ratio of up to 20 kg per 1000 l of water.

In a particular embodiment, the composition of the invention comprises aggregates, such as sand or gravel, to obtain mortar or concrete having excellent anti-fouling barrier properties.

Due to its interstitial buffer, which ensures a pH of at least 9, preferably between 9 and 12, the composition according to the invention is characterized by the secured and preserved long-term insolubility of cationic contaminants and the elimination of their later sustained release.

The compositions of the invention may take the form of self-setting mortars, plastics or hard concrete.

They make it possible to build non-leaking walls against the spread of pollutants by traditional methods in the soil.

They also allow injection into the voids in the soil to prevent the spread of these pollutants.

Finally, the materials according to the invention make it possible to build concrete waste storage boxes as well as other constructions of this kind, such as walls, storage containers and the like.

Another object of the present invention is to provide a method for making soil barriers by pouring or injecting a solidifying material of the type described above into the soil.

A variation of the method consists in making receptacles, walls or storage containers with this mass.

DETAILED DESCRIPTION OF THE INVENTION

The following examples are provided to illustrate the invention in more detail, but do not limit its scope.

Example 1

To build an underground boundary wall to enrich the polluted zone. in which the aqueous layer contains heavy metals and organic pollutants, according to the invention, a plastic concrete having the following composition by weight is used:

water 1000 clay <25 montmorillonite, 100 illit) 20 to 100 binder <CLK 45 or slag-based binder with 80% slag) 300 activated carbon (Akticarbon TK by CECA) 25 alkaline salt (Na2CO3>, 10 aggregates (sand) + round gravel 5/15) 3000

- 5 - e.í! i à}. (7 Wall made of concrete of this composition, has these ' features: s strength after 28 days 0.5 to 1 MPa permeability after 28 days K = 10 ^-9 / ° ^_1 10 m / a lead retention at least 20 kg / m ^{3 of} concrete mercury retention at least 20 kg / m ^{3 of} concrete ' retention of phenol at least 3 kg / m ^{3 of} concrete 1. As a variation, the mass additionally comprises: silicon dioxide (sublimed) 30 Additive (sodium lignosulfonate as wetting agent í and retarder) 5 ’ precipitating salt (sodium tartrate) 8

the influence these ingredients the throughput reduce to 10 ^-10 / 10 ^-11 m / s. Example 2 by invention are made walls or storage containers capable stop it mIGRATION even in radioactive cations

and organic pollutants using concrete of the following composition:

water 1000 clay (vermi ku1 it) 5 binder (CLK 45 or CPJ 45 or CPA 454) 2200 activated carbon (Akticarbon TK by CECA) 50 alkaline buffer (Nna2CCh) 30 aggregates (sand + gravel 5/15 and 15/25) 9000

After setting, the concrete has a mechanical strength after 28 days of 300 MPa and a permeability after 28 days of ^10-11 m / s. The cesium retention is 30 kg / m ^{3 of} concrete, the strontium retention is 30 kg / m ^{3 of} concrete, and the retention of dichloroethane is greater than 5 kg / m ^{3 of} concrete.

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As a variation, the following compounds may be added to the mass:

silicon dioxide (fly ash)

300 water-reducing plasticizer (Cerplast f i lhryso) precipitating salt (sodium pyrophosphate)

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The permeability is reduced to approximately 10 ¹² m / s and the mechanical strength is changed to 60 MPa.

Example 3

According to the invention, a self-setting mortar for a non-leaking wall.

intended for the isolation of a zone in which groundwater has been contaminated.

obtained from a mixture of the following composition:

Water

1000 i;

L · £

f · f? t foil (montmori 1lonit or bentonite type CVIS) binder (CLK 45 or slag-based cement)

200 activated carbon alkaline salt (CAE0H12)

100

This mortar can also be injected into the substrate.

It is to be understood that these examples are not limiting in nature and that they can be modified in various ways without departing from the scope of the invention.

Claims (11)

1. Water-based cement and clay. allowing the construction of a long-life barrier against the spread of pollutants. formed of cationic metals. above all. heavy metals, and / or organic products, characterized by containing activated carbon and a soluble basic salt. the aqueous phase of the mass to a pH of at least 9 for at least 10 years. toxic team. that they're able to damp Compound according to claim 1, characterized in that. that its components are present in a weight ratio Water 1000 cement or binder 40 until 2000 clay 25 until 1000 activated carbon 5 until 500 soluble buffer salt of pH> 9 30 until 500 from The composition according to any one of the preceding claims, further comprising silica, as characterized by sublimed silica or fly ash, in a weight ratio of up to 1500 kg per 1000 l of water. Compound according to any one of the preceding claims, characterized in that it contains a wetting agent, such as naphthalenesulphonate, in a weight ratio of up to 20 kg per 1000 5. Mass according to any of the preceding 1 water. claims. The composition comprises a retarder, such as sodium lignosulfonate, in a weight ratio of up to 50 kg per 1000 L of water. Material according to any one of the preceding claims, characterized in that. The composition of claim 1, wherein said composition comprises a plasticizer which reduces the water content in a weight ratio of up to 30 kg per 1000 l of water. Compound according to any one of the preceding claims, characterized in that. The composition comprises a salt precipitating metal cations such as sodium tartrate or sodium pyrophosphate. in a weight ratio of up to 20 kg per 1000 l of water. Compound according to any one of the preceding claims, characterized in that. it contains aggregates, sand or gravel to make mortar or concrete. Compound according to any one of the preceding claims, characterized in that the buffer ensures that the pH is maintained between 9 and 12. 10. A method of making a pollution barrier, characterized by. the composition according to any one of claims 1 to 9 being poured or injected into the soil. Method for producing anti-fouling containers, walls or storage containers, characterized in that a mass according to claim 8 is used.