WO1991008995A1

WO1991008995A1 - Backfill based on a foam binder, and method for producing same

Info

Publication number: WO1991008995A1
Application number: PCT/FR1990/000913
Authority: WO
Inventors: René HUTT; Emile Ledeuil
Original assignee: Hutt Rene; Emile Ledeuil
Priority date: 1989-12-15
Filing date: 1990-12-14
Publication date: 1991-06-27
Also published as: YU235990A; AU6972491A; CN1054635A; FR2666271B1; TNSN90150A1; FR2666271A1; MA22020A1

Abstract

Aggregate backfill wherein the aggregate binder is a foam, especially an organic or hydraulic foam, which can be used particularly in large scale workings. A method for producing same is also described.

Description

Embankments based on a foaming binder and their production process.

The present invention relates to new embankments based on a foam binder and their production process. Conventional embankments are already known, in particular embankments made of compacted and: or rolled concrete. Embankments, in general, are stacks of materials in different layers, generally intended to fill an excavation. However, conventional embankments have a certain number of drawbacks: they require the use of a large amount of cement and good aggregates must be used, which are expensive because they must meet demanding quality standards both on the in terms of hardness than in terms of the regularity of their particle size. If the aggregates are of poor quality, these break when the cement (binder) hardens and the concrete breaks up.

However, certain works, in particular works of large masses do not really require an embankment material such as concrete which, remember, has an average compressive strength of 20 to 25 Mpa, while 0.5 Mpa could be sufficient for an embankment 20 m high.

This is why the present invention relates to new aggregates embankments, characterized in that the binder of the aggregates is a foam. Foams are binders considered to be of lower quality than concrete, but, however, as the Applicant has discovered, are perfectly suitable for making embankments of structures of large masses.

By works of large masses, we mean works whose implementation is usually carried out by public works vehicles, such as the bulldozer and the compactor roller. As foams which can be used, mention may be made of organic foams and hydraulic foams. Among these, we can cite in particular:

- stable foams with completed formation, capable of wetting the aggregates and filling the voids between said aggregates, of the cement foam type,

- stable foam with delayed formation with internal thrust; if desired, a limitation of the amount of foam used makes it possible to simply bridge the aggregates,

- unstable foams (shelf life of 1 to 5 hours, for example) capable of transporting the binder between the aggregate grains.

In all of the above cases, and this is one of the advantages of the present invention, the foaming effect allows adhesion to the aggregates even in a humid environment.

Among the foams which can be used as a binder, there may be mentioned more particularly:

- cement foam (grout expanded from 2 to 4 times the initial volume or more). This foam can be reinforced by resins or setting accelerators such as concrete additives. The cement foam can be generated continuously or produced in batches. The use of a cement-rich grout allows acceleration and hardening, favored by the presence of air or gas bubbles in the foam. The foam binder can in particular be generated on site, continuously, by extraction of a mixture of cement slurry and foaming additions brewed in a mixing vessel under air pressure, at constant weight despite the inflows and outflows, weighing being done continuously, such a technique ensures the regularity of the quality of the expected product. Such foam does not grow and has no shrinkage,

- Polyurethane foams with an expansion coefficient of 20 or more or phenolic foams with an expansion coefficient of 50 or even 150 allow light backfilling. Of such foams have a high wetting power on even wet aggregates, and good residual mechanical characteristics. Used in limited quantities, a residual drainage value can be retained. Mixing and dosing generators suitable for such manufacture exist commercially. Such binders based on organic foams have a delayed expansion after implementation.

The foam-based binder is sprayed, dosed and mixed on the aggregate, either during the fall of the aggregate from a conveyor, or by coating in a hopper receiving the aggregates in relay, or even on dry aggregates with resins derivatives insoluble in water, for uses with taking underwater, - acrylic foams, which can be treated as unstable foam, therefore serve as a binder-carrying agent, transport cement and promote the setting of said cement by the presence of water. - elastic foams which can respond to certain specific stresses, with deformation of mediocre foundations, for example.

The aggregates used, and this is another advantage of the invention, can be of any kind, natural or not, heavy or light, and of any size. Preferably, they will be deprived of their fines (less than 15 or 25 mm); large blocks, or even riprap, are quite usable.

The mechanical qualities of the aggregates used will be advantageously proportional to those of the foams used and to the needs of the structure.

We can thus use for example bad pebbles (prohibited for concrete), even during decomposition, since the foam coating may be the only one to meet the expected mechanical standards. The foam may be generated in particular: - on site with incorporation of aggregates by gravity, placement and tightening (not essential if the aggregates are very open, placement alone will suffice), according to the usual compaction techniques. - by projection onto the aggregates for example from a conveyor pouring the aggregates into a curtain in free fall, then installation,

- by coating for example in a hopper receiving in aggregate the aggregates, then extraction and placement, - by concrete mixer, preferably by road, in particular continuously,

- by spraying using a "sprayed concrete" type gun at the same time as the aggregates are put in place. Among the advantages of the invention, we can cite: - The possibility, thanks to the foams, of giving cohesion to granular materials;

- thanks to the low densities obtained, of the order of 0.5 or 0.4 (or even less), thermal conductivity by using molded blocks or by branched casting will then be sought.

- _t leveling compounds or facades of mortars may be set to 1 • foamed according to the method above, for example; given that ieselgur (very fine fossil silica with 50% of particles between 0 and 5 micrometers) increases the resistance to compression, and to traction, the mixture:

1 part of cement (very fine H.R.I.)

1 part of lime live

2 parts of kieselgur will serve as a reference for the development.

Among the foam binders used in the embankments according to the invention, cement foam (or other hydraulic products such as lime) appears to be one of the most promising binders, both by its derivatives, its cost and its Implementation.

Embankments in which the aggregate binder is a foam above, being relatively fragile, should preferably be protected by surface structures such as those described in European patent N ° 0.248.725. The present application also relates to the above embankments, characterized in that they are embankments under water and in that the foam is deferred and obtained by spraying on the aggregates of a mixture sparingly soluble in Water leading to foam. Such a mixture can for example be constituted by a mixture of a polyurethane resin and water, the amount of water used determining the delay in the delayed formation of the foam. By soluble is meant that the mixture remains substantially on the immersed aggregates and that 1 • water does not alter its qualities of adhesion and generation of foam. The aggregates covered with the mixture are placed in an embankment; then, the foam forms after a certain delay, leading to the desired embankments. They can be covered by soaking but preferably by spraying. We know the great advantages brought by cellular mortars (whose base is a foam): very good thermal insulation, absence of cracking, low coefficient of thermal expansion, etc ... Currently, most of these mortars are manufactured by chemical. Sand-cement-lime is mixed, aluminum powder is added, and the resulting evolution of hydrogen leads to cellular mortar. Another way to get the cellular mortar is to mix the hydraulic mortar with a foaming agent. In principle, this method of making cellular mortars (up to expansion rates of one hundred percent, i.e. one hundred liters of air per one hundred liters of initial mixture) is very simple.

During the manufacture of the normal mortar, a surface-active agent (for example, of the alkylaryl-sulfonate type) is also added to it and, under the effect of the mixing, bubbles form in the mixture. It is recognized that mortars cell phones made in this last way are better than those made with aluminum powder (at the same dosage of cement they are more resistant and at equal resistance they are lighter); however, their development has hardly exceeded laboratory level. In practical terms, their current method of preparation leads to two major drawbacks: The rate of preparation is much lower than that of a conventional or cellular mortar with aluminum powder: with each waste the occlusion of air by brewing requires several additional minutes of brewing.

Even when all the components are dosed correctly, the rate of occluded gas is inconsistent. It would be desirable to obtain foam binders of predetermined constant quality, according to a rapid manufacturing process.

This is why the present application also relates to embankments, characterized in that the foam is hydraulic, and generated continuously. It is desirable that the foam, generated continuously, be of constant quality. The foam can in particular be prepared by blowing a gas under pressure into the hydraulic material and by simultaneously agitating, under pressure, said hydraulic material so that the blown gas cannot escape, the constant quality being obtained by weighing so that the supply of new hydraulic material is substantially equal in quantity at the outlet of the hydraulic material in the foam state. The above hydraulic foam is preferably based on a mortar coming out of a conventional manufacture, mortar which is weighed in a limited volume and into which a gas, carbon dioxide or air is preferably blown, under a determined pressure . Simultaneously, said material is agitated under conditions such that the blown air cannot escape. Agitation is done in a vacuum, and under pressure, the dosage of the mixture is constantly monitored by weighing.

The above foam production, when carried out continuously, requires a controlled and regulated weighing of the foam producing assembly. Weighing allows you to know at any time how much, for example mortar (weight element and very well defined elsewhere) is present in the closed vessel, called a pressure chamber, to be mixed with the rest of the volume available in gas (element not weight and regulated by the remaining volume available and by its only pressure).

It is thus possible to determine the weight of the binder entering into the composition of the foam, the volume of gas and the pressure, the weighing continuously allowing the regulation of the supply of gas and binder.

In conventional manufacturing, surfactants are used which can also be used in the present process. The agent can be incorporated into the binder before or after its introduction into the pressure chamber. the surfactant can be fogged and incorporated into the gas blown under pressure.

According to this new technology in terms of cellular hydraulic binders in particular, the gas is regulated under pressure before being introduced into a predetermined binder weight.

Among the hydraulic binders used, such as mortar, cement (preferably very fine grind) we will note the specific advantages linked to lime, quick or slaked, which will confer a greater lightness, therefore better sealing and thermal insulation. The lime-cement mixture will adjust the setting and hardening times. For lime, it is then advantageous to use carbon dioxide instead of air in order to favor the reactions of structuring of the bubbles. As an example of a mixture, quicklime (or slaked ground lime, delivered in aqueous phase) and fly ash (example, Gardanne, even delivered in aqueous phase) and some doping products like acrylic.

The structure of an organic foam is on a basis of 3 to 5 microns; cements have 100 micron particles that are difficult to match. Very fine grinding is desirable for a good marriage. Lime is better able to provide a binder of 0 to 10 microns. The stabilization of a lime structure foam can be stiffened by an organic foam.

Finally, it should be noted that the pressure system in a vacuum above is compatible with all types of foaming agents (alkyl, aryl, non-ionic, proteins or proteins, etc.) and that it even allows use them at a lower dosage. Other structuring agents such as acrylic or other resins can give the finished product a framework guaranteeing non-shrinkage and limiting water absorption often linked to extreme porosity. The present invention also relates to a method for producing embankments described above, characterized in that the foam is poured onto the aggregates to obtain the expected embankment bound with the aid of the foam, and then if desired compact l 'together. Under preferential conditions for implementing the method described above, the above foam is produced in situ.

The present application equally has as its object a process for producing an embankment above, characterized in that a foaming mixture is sprayed onto the aggregates to obtain the expected embankment bound using a foam. This foam has delayed formation. The projection is advantageously carried out during the supply of aggregates.

The present application finally relates to a method of embodiment characterized in that the aggregates are coated and then the coated aggregates are poured to produce the expected fill.

The example which follows, with reference to the appended drawing, illustrates the present invention without however limiting it:

- A mortar being conventionally prepared in 1: 300 kg of cement are mixed in high turbulence with 166 1 of water with 6 kg of product favoring the creation of foam, 4 kg of bentonite as stabilizer and 10 1 of deflocculant Sylco ^R (soc. Syntress). It is sent continuously, at a pressure of approximately 3.5 bars, using a screw pump 2 to a pressure chamber 3, regulated by 0.4 Mpa of air, containing a rotary agitator 4 ( conventional device generally called a pipe agitator) and a tube 5 at the bottom which allows the continuous blowing of pressurized air of approximately 4.5 bar at a flow rate of approximately lm ³ / h of compressed air ( about 2.45 bar at normal pressure). The aerated mortar is also evacuated at 6 at a pressure of approximately 3.5 bars. The engine-mixer and mortar assembly is weighed continuously by a weighing device 7 and this weight regulates the mortar arrival rate so as to keep the weight of the assembly constant. A foam is thus obtained which is poured into an opening to be filled, then pours coarse aggregates to obtain, after hardening of the foam, the expected backfill.

Whether in discontinuous or continuous manufacturing, the amount of air introduced into the chamber corresponds to the desired expansion rate. And since the air is occluded in a vacuum, with no possibility of loss, the mortar leaves the mixing chamber at the expected expansion rate. During the preparation, a surfactant is advantageously added at any point on the circuit, this point possibly being: - the mortar mixer. In this case, the surfactant will be preferably added at the end of the mixing so that the tank does not overflow due to the start of foaming, or - in the pipe connecting the pump to the pressure chamber, or - by spraying in compressed gas.

It should be noted that the more one seeks a high rate of expansion, the more the rate of production is too, whereas it is the opposite in traditional system. Likewise, expansion rates of up to six hundred or seven hundred percent can very easily be obtained. Indeed, as the mortar is under pressure in the mixing chamber, the air bubbles have a reduced volume and we can therefore introduce much more than under ambient pressure. The above technique is also compatible with hydraulic binders other than conventional cement, namely without limitation pure cement, cement with fillers in the form of various very fine sterile materials, for example ash, pozzolans, various clays, mineral or organic colloids, lime-cement mixtures, quicklime or slaked lime, plaster, anhydrite.

Claims

1 / Aggregate backfill characterized in that the aggregate binder is a foam.

2 / embankment according to claim 1, characterized in that it is a large mass embankment.

3 / embankment according to claim 1 or 2, characterized in that the foam is an organic foam.

4 / embankment according to claim 1 or 2, characterized in that the foam is a hydraulic foam.

5 / embankment according to any one of claims 1,2 or 4, characterized in that the foam is hydraulic and generated continuously.

6 / embankment according to claim 5 characterized in that the foam is of constant quality and prepared by blowing a gas under pressure into the hydraulic material and by simultaneously agitating, under pressure, said hydraulic material so that the blown gas can not not escape, the constant quality being obtained by weighing, so that the supply of new hydraulic material is substantially equal in quantity at the outlet of the hydraulic material in the foam state.

7 / A method of making an embankment according to any one of claims 1 to 6, characterized in that the foam is poured, pours the aggregates on the foam then, if desired, the whole is compacted.

8 / Method of making an embankment according to one any one of claims 1 to 6, characterized in that a mixture producing a delayed foam is projected on the aggregates to obtain the expected backfill bound using a foam.

9 / embankment according to one of claims 1 to 5, charac¬ terized in that it is an embankment under water and in that the foam is deferred and obtained by spraying on the aggregates of a mixture slightly soluble in water, leading to a foam.