WO2009066185A2

WO2009066185A2 - Method for triggering and/or accelerating the setting of a hydrosetting non-refractory pasty material

Info

Publication number: WO2009066185A2
Application number: PCT/IB2008/003917
Authority: WO
Inventors: Vincent Morin; Laurent Meunier; Serge Sabio; Véronique COLLIN
Original assignee: Lafarge
Priority date: 2007-09-11
Filing date: 2008-09-05
Publication date: 2009-05-28
Also published as: WO2009066185A3

Abstract

The invention relates to a method for triggering and/or accelerating the setting of a hydrosetting non-refractory pasty material selected from the group consisting of concrete, mortar and a cement paste. According to said method, acoustic waves are applied to the material, said acoustic waves inducing the triggering and/or acceleration of the setting.

Description

METHOD FOR TRIPPING AND / OR ACCELERATING THE TAKING OF A NON-REFRACTORY PASTE MATERIAL WITH A HYDRAULIC RECEPTACLE

The present invention relates to a method for triggering and / or accelerating the setting of a non-refractory pasty material with a hydraulic setting, selected from the group consisting of a concrete, a mortar and a cement paste. The present invention also relates to a process triggering and / or accelerating setting of a material selected from the group consisting of a concrete, a mortar and a cement, the setting of said material having been previously retarded by the administration of a retarding agent

Ultrasontc Activation of Hardening of High-Alumma Cements, Russian Journal of Applied Chemistry, Vol 72 No 6, 1999, pp 949-951, mentions the use of ultrasound as a curing agent for a cement alummeux The hardening test is carried out on pure paste, at a water / cement ratio of 0.4 Three power levels (90, 120 and 150 watts) are used on a small cell (10 x 10 x 10 mm) The treatment time varies from 30 seconds to 1 minute 30 seconds While below 30 seconds no treatment efficiency is visible, the experimenter notes that above 1 minute 30 seconds there is a phenomenon of taking However, the use of pure paste and the reaction conditions described in this document (namely low power ultrasound and a very small cell) do not allow any consideration of an industrialization of the process object of said document In addition, the pr The invention disclosed in this document relates exclusively to a cement paste of the alumina type and not of the Portland type.

A refractory cement is a hydraulic-setting binder for obtaining refractory concrete, that is, having a melting point high enough to withstand very high temperatures. A refractory cement of this nature has a minimum content. in lime, to the extent that this compound lowers the melting point of the concrete obtained m fine

Unlike a Portland cement, an alumina cement (or refractory cement), as previously described, is by nature very specific and very reactive Its hardening under the action of acoustic waves is consequently theoretically much easier to implement than for Portland cement

The Applicant has discovered, surprisingly, that a pasty non-refractory material with hydraulic setting, selected from the group consisting of a concrete, a mortar and a cement paste, and having physicochemical properties quite distinct from those of the cements alummeux, can be activated and / or accelerated by application of high power acoustic waves

Therefore, one of the objects of the present invention is a method of triggering and / or accelerating the setting of a non-refractory, hydraulically-setting pasty material selected from the group consisting of a concrete, a mortar and a paste of cement, in which acoustic waves of low frequencies and / or ultrasonic high power are applied to said material, said acoustic waves inducing said triggering and / or said acceleration setting According to a preferred embodiment of the invention, the acoustic waves according to the invention Invention Induce a Cavitation Phenomenon

According to a preferred embodiment of the invention, the acoustic waves are ultrasound

According to a second preferred embodiment of the invention, the acoustic waves are low frequency acoustic waves

A pasty material designates a material having an intermediate consistency between the liquid and the solid, a paste. In other words, the pasty qualifier designates a material whose state is between the "fresh" state and the fully hardened state. An acoustic wave refers to the propagation of a disturbance producing in its path a reversible variation of local physical properties. It is characterized in particular by its frequency. An acoustic wave of frequency greater than 15 kHz corresponds to the ultrasound, that is to say to the sounds not audible to the human ear An acoustic wave with a frequency lower than 15 kHz corresponds to acoustic waves called "low frequencies" For these two frequency ranges, it is possible to obtain the birth and the radial oscillation of gas bubbles and of vapor in a liquid subjected to a depression This phenomenon is called cavitation In particular, concretes, mortars and pastes of cement contain liquid water that may give rise to cavitation bubbles.

The term "plug" according to the present invention means the passage of cement paste, mortar or hydrated concrete in the cured state. In this regard, one can for example refer to the publication of Nonat A. and Mutin J. entitled: "From hydration to setting". Proceeding of the international RILEM workshop. Edited by E & FN SPON. pp171-192. 1991.

The term "fresh state" according to the present invention is the first instants of hydration, where the cement paste, mortar or hydrated concrete is malleable.

The term "hardened state" according to the present invention the moment of hydration, where the hydraulic binder, mortar or concrete has mechanical strength.

Concrete is an agglomerated composite material consisting of hard aggregates of various sizes bonded together by a binder. Common concretes consist of fine aggregates (grains of sand) or coarse grains (gravel), a binder called cement, usually a Portland cement with or without cement additives, and water. The components are very different from each other: their density varies, in common concrete from 1 (water) to 3 (cement) t / m ³ . If the type of binder used is not a cement, then depending on the binder used, it is called resin concrete, hydrocarbon concrete, clay concrete, etc.

A grout (or cement paste) is obtained by mixing a binder, water and optionally additives / additives.

A mortar is obtained by mixing a binder (lime or cement), sand, water and possibly additives / additives.

Multiple compositions of grout, mortar or concrete can be obtained by varying the parameters: binder (type and dosage), additives and additives, water dosage. As regards the binder, all cements and lime are usable; their choice and the dosage depend on the work to be done and its environment.

The mixing time must be optimal, in order to obtain a homogeneous and regular mixture.

Grouts, mortars or concretes can be: - Prepared on site by dosing and mixing the various constituents including adjuvants,

- Prepared on site from pre-dosed dry industrial mortars or industrial concrete and before use, simply add the required amount of water, - Delivered by a central

Cement is a pulverulent product obtained by co-grinding calcium sulphate, fillers and clinker. The latter consists of a mixture of silicates and calcium aluminates heated to 1450-1550 ^° C., at which temperature this mixture combines to give different mineralogical phases called alite or C3S (major phase), belite (C2S), ferrites (C4AF), aluminate (C3A)

As a guide, it should be recalled that

- C = CaO

- S = SiO ₂ - A = AI ₂ O ₃

- F = Fe ₂ O ₃

The usual cement belongs to the class of hydraulic binders, because it has the property, by reacting with water, to form hydrates transforming the paste

(which has a consistency of starting more or less fluid) in a solid practically insoluble in water This hardening is due to the hydration of certain mineral compounds, in particular silicates and aluminates of calcium

The expressions "hardening" or "setting" are used to designate the transformation of the cement paste from a more or less fluid state into a solid state. The moment of activation of this process will be referred to indistinctly as "triggering" or "triggering". activation »Increasing the speed of" hardening "is called" acceleration "of setting (or hardening)

Portland cement is obtained by baking a mixture of sand and limestone Additions of bauxite, kaolin, iron are optionally carried out when necessary to correct, if necessary, the composition by adding iron or calcium. alumina

The chemical composition is generally described as the following

SιO2 19-22% AI2O3 3-5%

Fe2O3 3-5%

CaO 60-66%

MgO 0.5-5% TιO2 0.2%

SO3 2-4%

The main mineralogical phases are generally described as the following

• C3S (major phase 50-70%) • C2S (5-15%)

• C3A (0-15%)

• C4AF (0-15%)

The main hydrates formed are CSH (calcium silicate hydrates), Portlandite (hydrated calcium hydroxide), ettringite (hydrated calcium nitrosaluminate) and monosulfoalummate (hydrated calcium monosulfinalumate).

The structuring speed of such a material is much slower than the structuring speed of an aluminous material. If the setting time of the two types of material is comparable, the resistances evolve much more slowly (20-30 MPa at 1 day However, in Portland cement the hydrates formed are stable, with the exception of ettringite in monosulfoalummate But in this case, no significant loss of resistance is observed The setting trigger corresponds to the activation of the hydration process of a pasty material, so that a hardening of the pasty product becomes possible again according to a conventional hardening kinetics

Without being bound by the theory, it is accepted that the propagation of an acoustic wave - such as an ultrasonic or low frequency wave - in a fluid (generally liquid) creates alternately zones of pressures and depressions. depression is sufficiently high, the interparticular distance becomes greater than the maximum cohesion distance of the liquid The space thus created allows the birth of bubbles called cavitation bubbles The bubbles formed during a cavitation contain only gases and For the cavitation to take place, a power threshold must be reached. This threshold is for example of the order of 0.5 watts / cm ² (surface of the vibrating source) to 20 kHz for the water L the amount of vacuum required to reach the cavitation threshold depends on several parameters - the higher the frequency, the shorter the vacuum period (it may be too short to form a cavity),

The higher the viscosity of the treated medium, the more difficult the cavitation is to obtain because the particles are more difficult to separate,

The presence of microparticles or dissolved gases are all elements of heterogeneity that constitute zones of disorganization of the liquid medium favoring the formation of cavitation bubbles. This is called lowering of the cavitation threshold. These cavitation bubbles have a lifetime. short Their volume increases strongly during the depression phase then they implode suddenly during the compression phase by fragmenting to give many microbubbles, new germs subjected to cavitation

This cavitation is, for example, at the origin of the effects of power ultrasound on the media they pass through. The implosion of a cavitation bubble also causes the emission of a jet of liquid at high speed (approximately 400 km / h) Thus, if a liquid / solid heterogeneous medium is irradiated, the liquid jet will play a very important role for cleaning but will also induce erosion on the surface of the solid. The mechanical and chemical effects appear to be induced by such a phenomenon. cavitation and the uses that can be made of it appear to be the following: - The cleaning and / or erosion of solid surfaces in a liquid medium, for example the destruction of a coating (or "coatmg"),

- The dispersion of solids in a liquid medium and the disagglomeration,

- The size reduction of solid particles,

- the intimate mixture of immiscible liquids, - the acceleration of chemical reactions,

- Other purely chemical effects, called sonochemical effects

It should also be noted that after a few cycles, implosion of cavitation bubbles leads to an increase in temperatures and pressures. As an illustration, it has been calculated that in micro-domains implosion, pressures of the order of 1000 to 10 000 bar and temperatures of 10 000 K are reached, under the assumption of adiabatic conditions, that is to say when no amount of heat is exchanged with the external environment

Triggering (or activating) and / or accelerating the setting of a concrete comprising a Portland cement may be extremely interesting in that the setting of a concrete may be delayed. by a variety of factors, including a low outdoor temperature In fact, the hydration slows down when the temperature decreases Thus, a process to trigger or accelerate the setting could be useful in cold weather (5-10 ⁰ C) This would in particular make it possible to avoid long set-up times and would allow the timely removal of concrete from low temperature cast concrete.

In addition, the present invention also makes it possible to increase the efficiency of accelerating agents (and especially chemical accelerators), when the latter are stimulated by acoustic waves, and in particular ultrasounds.

Preferably, the acoustic waves according to the invention have a frequency of between 100 Hz and 100 kHz, advantageously between 100 Hz and 60 kHz, preferably between 100 Hz and 40 kHz, and preferably between 200 Hz and 40 kHz According to one embodiment Preferably, the acoustic waves are ultrasound. Preferably, the ultrasound frequency is between 15 kHz and 100 kHz, preferably between 20 kHz and 60 kHz, advantageously between 20 kHz and 40 kHz.

According to a second preferred embodiment, the acoustic waves are low frequency acoustic waves. Preferably, the frequency of these acoustic waves is greater than or equal to 100 Hz and strictly inferior to

15 kHz, advantageously between 100 Hz and 10 kHz, preferably between 100 Hz and 35 kHz, and particularly preferably between 200 Hz and

2000 Hz These acoustic waves are preferably used for concrete treatment

Preferably, the power of the acoustic waves according to the invention is between 0.5 and 20 kW, advantageously between 1 kW and 10 kW, preferably between 2 kW and 6 kW. According to a preferred embodiment, the power of ultrasonic acoustic waves is between 1 kW and 20 kW, preferably between 2 kW and 10 kW, advantageously between 4 and 6 kW

Advantageously, such frequencies and such powers can make it possible to obtain very energetic cavitation bubbles as well as a satisfactory propagation of the cavitation wave within the pasty material

The acoustic waves used are called high-power acoustic waves. This high power can make it possible to induce the abovementioned cavitation phenomenon and thus to obtain the triggering and / or the acceleration of the setting of one of the abovementioned materials. to be defined as a power making it possible to trigger a cavitation phenomenon in the medium to which it is applied. It may especially be between 0.5 kW and 20 kW, preferably between 1 kW and 10 kW, advantageously between 2 and 6 kW.

The duration of application of the acoustic waves to the material can be expressed in cubic meter of treated material per minute This parameter is closely related to the preceding parameter, namely the power of the acoustic waves used, insofar as a lower power can theoretically be compensated by a longer application time (or treatment time) and vice versa The duration of application of the acoustic waves to the pasty material with hydraulic setting varies according to the amount of material to be treated

Thus, one of the advantages of the invention is that the use of low frequency and / or ultrasonic acoustic waves of high power according to the invention allows a short enough processing time to allow the industrialization of the method according to the invention.

Preferably, the material is a concrete Advantageously it is a concrete based on Portland cement

The treatment of the pasty material with hydraulic setting is carried out continuously, for example within a device such as an ultrasonic channel, or in batches ("batch" treatment)

According to a particularly preferred embodiment, the treatment of the pasty material with hydraulic setting is carried out continuously Preferably, the amount of material treated per minute is between at least 0.2 and 4 m ³ / min, preferably between 1 and 2 m ³ / min.

Of course, the skilled person can, using routine tests, determine the optimal torque power / flow

According to a preferred embodiment, the material is introduced into a chamber emitting acoustic waves, in particular ultrasonic waves. This chamber may be of different shapes such as a tank, a pipe, or the like. Advantageously, the enclosure is a According to a first embodiment, the emission source of the acoustic waves comprises at least one emitting plate, and preferably two emitting plates.

According to a second embodiment, a plunging acoustic wave emitting system, comprising at least one body immersed in the material to be sonified, is used for the purposes of the present invention.

Such a channel emitted acoustic waves, as mentioned above, allows to industrialize the process optimally, and thanks to such a device, yields of between about 1 m ³ and about 2 m ³ of material treated with It may also be advantageous to administer a retarding agent to a concrete, a mortar or a cement in order to obtain retardation of setting (or retardation of hydration). US 4,964,917 teaches a method for reusing ready-mixed concrete, firstly comprising the steps of retarding hydration and then accelerating hydration, with a view to possible future reuse. The retarding agent and the accelerator are both chemical agents This method makes it possible to recover the excess of already poured concrete, by introducing a retarding agent, and to restart the hydration at the opportune moment by the addition of an accelerated agent. However, as mentioned above, this document only discloses the use of a chemical accelerating agent or the addition of fresh concrete, which imposes binding weighing operations as well as an adjustment to temperature function, which avoids the present invention

This is why another subject of the present invention relates to a method for triggering and / or accelerating the setting of a pasty material which is not hydraulic setting refractory, selected from the group consisting of a concrete, a mortar and a cement paste, wherein low frequency and / or ultrasonic acoustic waves of high power are applied to said material, said acoustic waves inducing said tripping and / or said acceleration of setting, the setting of said material having been previously delayed by the administration of a retarding agent

According to a preferred embodiment of the invention, the acoustic waves according to the invention induce a cavitation phenomenon

The delay in setting after the administration of a retarding agent (or retarder) will obviously depend on the type of retarding agent used but also on its concentration, ie the dosage of retarding agent in the material of which one wish to delay taking This delay can be of the order of a few hours (2 or 3 hours) up to a week or more

Preferably, the material will be delayed by at least 24 hours. Optimally, the setting delay will be between about 24 hours and about 72 hours.

The addition of a retarding agent makes it possible to limit the problems related to storage and / or delivery. This therefore provides a comfort of use and in particular allows a satisfactory period of time to make the delivery of the material while limiting the possible losses

According to a variant of the present invention, the retarding agent is added to the cement when the latter is in the form of a powder. Such an addition may in particular be carried out after the cementing step by grinding the clmker by a retarding agent (or retarder). ) is understood to mean any agent that makes it possible to obtain the desired result, namely retardation of setting (or hydration). The known chemical retarders are in particular the following: a) Sugars and derivatives thereof

The most used sugars are • Sucrose (or sucrose in English)

• Glucose

• Reducing sugars (lactose, maltose etc.)

• Cellobiose, Gallactose etc

• Derivatives such as glucolactone etc. b) The carboxylates

Among the carboxylates, gluconate is currently one of the most used retardant plasticisers Its mechanism of action can be generalized to other carboxylates (acid or salified form) However, gluconate approaches a sugar by its constitution, which makes it confers a certain specificity

The other carboxylic acids commonly used are

• Tartπque acid

• Citric acid • Gallic acid

• Salicylic acid

The associated salts may be

• calcium

• sodium • potassium

• lithium

However, other salts can obviously be used. C) Phosphonates

The main phosphonates are commercial products of the company Solutia, such as

• Dequest 2000 amino acid (methylenephosphonic acid)

• Dequest 2006 pentasodium salt of aminotrene (methylenephosphoniac)

• Dequest 2046 hexamethylene-diene-tetra (methylene-phosphonic acid)

• Dequest 2060 and 2066 diethylene thalamine penta (methylenephosphonic acid and its sodium salt)

An exception is known under the name "Optima 100" (marketed by Chryso) whose structure contains a chain of ethylene polyoxides giving this product a more soluble character d) Zinc salts

This category includes

• Zinc oxide • Zinc borate

• Soluble salts of zinc (nitrate, chloride) e) Borates

This category includes: • Boric acid

• Zinc borate

• Boron salts f) Surface agents suitable for coating the surface of cement grains The known coating agents comprise in particular:

• cellulose ethers,

• acrylates,

• Alginates,

• Stearates. The Applicant has surprisingly found that flaxseed oil is an excellent surfactant suitable for coating the surface of cement grains. Indeed, this compound acts after a prior treatment of the cement (mixing the oil with the cement and heating at 60 ⁰ C) and allows the formation of clusters of particles coated with the oil. This, by drying - that is to say by crosslinking under the action of oxygen in the air - will form a relatively tight film on the surface of the cement grains. When this mixture is introduced into the water, the specific surface of the cement in contact with the water is less important than in the case of untreated cement, which results in a decrease in the speed of its hydration. Other compounds have a similar mechanism of action (particle coating) but have a lower dosage / effect efficiency than that of flaxseed oil.

All the retarders do not have an identical operation, hence the effectiveness of the acoustic wave treatment variable according to the self-timer used. Nevertheless it is generally found that the treatment according to the invention always induces an effect. The different types of retarders mentioned above can be used alone or in combination with each other.

According to a particularly preferred embodiment, the material is a concrete. Optimally, it is a concrete based on Portland cement. Advantageously, the retarding agent is introduced during the formation of concrete or in a limited period of time - preferably less than 3 hours - after this formation.

An alternative is to make a conventional concrete and then introduce at least one retarder in the concrete manufactured to avoid or stop the hydration process (or setting process) and thus recover the concrete for a storage and / or subsequent reuse

Preferably, the retarding agent is selected from the group consisting of sugars and derivatives, carboxylates, phosphonates, zinc salts, borates and surfactants adapted to coat the surface of cement grains such as Im oil, stearates, cellulose ethers, alginates, acrylates

As surfactant suitable for coating the surface of the cement grains, it is preferable to use the oil in addition to this preferred solution, are used in the sense of the present invention, from the least effective to the most effective at least one sugar. , preferably at least one phosphonate, preferably at least one borate, advantageously a zinc salt and optimally a gluconate or a mixture of gluconate and borate or a mixture of phosphonate and borate In fact, the gluconate has, besides its known function of delaying agent, a function of fluidizer which allows an interesting maintenance of the rheology of the treated material over time

Preferably, the acoustic waves according to the invention have a frequency of between 100 Hz and 100 kHz, advantageously between 100 Hz and 60 kHz, preferably between 200 Hz and 40 kHz.

According to one embodiment of the invention, the ultrasonic acoustic waves have a frequency of between 15 kHz and 100 kHz, preferably between 20 kHz and 60 kHz, advantageously between 20 kHz and 40 kHz.

According to a second embodiment of the invention, the frequencies are greater than or equal to 100 Hz and strictly less than 15 kHz, advantageously between 100 Hz and 10 kHz, preferably between 100 Hz and 35 kHz, particularly preferably between 200 Hz and 2000 Hz These acoustic waves are used in a preferred manner for the treatment of concretes The benefits of using such frequencies have been mentioned previously

Preferably, the power of the acoustic waves according to the invention is between 0.5 kW and 20 kW, advantageously between 1 kW and 10 kW, preferably between 2 kW and 6 kW.

According to a preferred embodiment, the power of ultrasonic acoustic waves is between 1 kW and 20 kW, preferably between 2 kW and 10 kW, advantageously between 4 and 6 kW

Thus, one of the advantages of the invention is that the use of low frequency and / or ultrasonic acoustic waves of high power according to the invention allows a short enough processing time to allow the industrialization of the process according to the invention.

Of course, the skilled person can easily, using routine tests, determine the optimal torque power / flow

According to a preferred embodiment, the material is introduced into an acoustic wave emitting chamber, in particular ultrasonic waves. This chamber may be of various shapes such as a tank, a pipe, or the like. Advantageously, the enclosure is a channel for According to a first embodiment, the acoustic wave emission source comprises at least one emitting plate, and preferably two emitting plates.

An acoustic wave emitting pipe, as mentioned above, makes it possible to industrialize the process optimally, and thanks to such a device, yields of between 1 and 2 m ³ of treated material per minute can be obtained. also relates to a device for implementing the method according to the invention, such as the aforementioned acoustic wave emitting pipe

The characteristics and the mode of operation of the process and the device for implementing the method, according to the present invention, will appear more clearly on reading the description which follows, made with reference to the drawings.

These drawings are intended to illustrate the present invention. They do not constitute, in any way, any limitation of the scope of the present invention. FIG. 1 represents a side view of a device for implementing the method according to the invention. invention, this device for continuous treatment of non-refractory pastes material hydraulic setting FIG. 2 is a side view of a device for implementing the method according to the invention, adapted to a batch process (batch processing)

An ultrasonic pipe according to the invention is illustrated in FIG. 3. FIG. 4 shows a sectional view of this ultrasonic pipe.

Figure 5 shows the impact of acoustic wave frequency and concrete treatment time on the acceleration of hydration

In the case of a device for continuous treatment of the non-refractory, hydraulically setting pasty material 1, the concrete is poured into the feed hopper 1 1, directly from a spinning truck or from a mixer. Concrete arrives in the body 16 when the concrete reaches the level of the acoustic wave emission equipment 13, it is then subjected to acoustic wave treatment. 16 body through the worm 12, then out of the device through the pipe 14 The porthole 15 to control the good flow out of concrete The latter can be recovered either directly in a dumpster or in a truck spinning truck The body of the acoustic wave treatment device 16 is inclined because it is necessary to avoid the presence of free spaces or of air at the level of the acoustic wave treatment zone, for This device can easily be cleaned with water using the worm 12 It is important that the acoustic wave treatment area is cleaned properly between each use, so as not to reduce the effectiveness of the treatment

In a batch device 2, as shown in FIG. 2, the concrete is introduced through the hopper 21 until the body 25 is filled (it is important to avoid the presence of vacuum in the acoustic wave treatment) The concrete is kneaded by the endless screw 22 during the acoustic wave treatment which is carried out at the level of the acoustic wave emission equipment 23 Then, the body 25 is emptied thanks to the trapdoor. emptying 24

In any case, in the case of the device 1, as the device 2, stirring by the worm allows to treat the concrete more uniformly, resulting in an increase in the effectiveness of the treatment and a decrease the concrete setting time thus obtained. This is demonstrated by the data These data also show that an increase in the rotational speed of the worm induces a reduction in the setting time.

The ultrasonic channel 3a comprises in particular a hollow tube on which ultrasonic transmitters 32 with a power of 25 kHz are fixed. The non-refractory pasty material with hydraulic setting is introduced into the hollow tube 31, and is then subjected to ultrasonic acoustic waves during its passing near transmitters 32

Optimally, the emitters 32 are not aligned in the vertical plane, but are offset (advantageously arranged spirally) for better ultrasound diffusion, as shown in FIG. 4

The examples of embodiment presented below will make it possible to highlight the aims, objects and advantages of the invention, without however limiting the scope. Description / formulation of mortar and concrete

The characteristics of the mortar and the concrete used are presented in the appendix, in table 1

Tests A to D are carried out on mortar Only the ratio water / cement (E / C) can vary (0.6 or 0.68) The volume of mortar used is 1, 8 L The cement used is of type CEM 1 52 5 N

Tests E are carried out on concrete The ratio water / cement (E / C) is 0.68 The volume of concrete used is 8.6 L The cement used is of type CEM 1 52 5 N

All the tests are carried out at the temperature of 20 ⁰ C except that aiming to accelerate a concrete at low temperature

The acoustic wave emission equipment used in the examples on mortar is an ultrasonic pipe which has a maximum electric power of 1000 W (1 kW) and volume 1, 5 L

The acoustic wave emission equipment used in the examples on concrete has the following characteristics

• diameter of the pipe 280 mm

• volume of the pipeline 8.6 L

• maximum electrical power 2000 W

• maximum frequency 20 kHz • manual agitation

A Impact of the duration of application of ultrasound 1) Gluconate retarder The results are presented in appendix, in Table 2

These results were obtained from a mortar comprising, as a retarder, gluconate dosed at 0.2 parts by weight of dry matter per 100 parts by weight of cement

The application of ultrasound is carried out at 8 minutes of mixing with agitation of the mortar.

It should be noted that the setting time is obtained from the hydration curves by thermal follow-up of the sample. In the so-called "dormant" period which follows the mixing, the minimum temperature is recorded. After this minimum, the temperature increases. again, and when reaching an elevation of + 1 ° C above the minimum, the corresponding time-out is chosen as the thermal setting time

The results presented in Table 2 make it possible to conclude that the ultrasound has an effect of acceleration of setting on a formulation delayed by gluconate, whatever the duration of the treatment Nevertheless, it is noted that the longer the treatment, the more catch acceleration is important

2) Zinc borate retarder

The results are presented in the appendix, in Table 3

These results were obtained on a mortar comprising, as retarder, zinc borate dosed at 0.5 part by weight of dry matter per 100 parts by weight of cement This assay allows a delay in hydration of about 48 hours

The application of ultrasound is done at 8 hours of mixing, with stirring of the mortar The mechanical strengths are measured at 1 day of the application of ultrasound, and are obtained on specimens 4x4x16 cm

From the results presented in Table 3, it can be seen that ultrasound has a setting acceleration effect on a formulation delayed by zinc borate However, the minimum treatment time must be between 10 seconds and 60 seconds

3) Phosphonate retarder (Dequest 2046) The results are presented in the appendix, in Table 4

These results were obtained from a mortar comprising, as a retarder, a phosphonate dosed at 0.25 parts by weight of dry matter per 100 parts by weight of cement This assay allows a retardation of hydration of about 48 hours The application of ultrasound is done at 24 hours of mixing, with agitation of the mortar

The mechanical strengths are measured to 1 day of the application of ultrasound, and are obtained on specimens 4x4x16 cm

The results presented in Table 4 indicate that ultrasound has an accelerating effect on a formulation previously delayed by phosphonate, regardless of the duration of treatment

Once again, it should be noted that the longer the treatment, the greater the rate of acceleration

4) Im oil retarder

The results are presented in the appendix, in Table 5 These results were obtained from a mortar comprising a cement coated with oil of Im The treatment consists in mixing the cement and the oil beforehand. Im oil with respect to the mass of cement is 3% The mixture is then heated at 60 ⁰ C for 2 hours to activate the oil siccativation reaction The mechanical strengths are obtained on specimens 4x4x16 cm

From the results presented in Table 5, it is found that ultrasound has a setting acceleration effect on a formulation delayed by

B Impact of the application deadline for ultrasound

The results are presented in the appendix, in Table 6 These results were obtained from a mortar comprising, as a retarder, gluconate dosed at 0.2 parts by weight of dry matter per 100 parts by weight of cement

The mechanical strengths are obtained on 4x4x16 cm samples. It is interesting to note that the setting acceleration is all the more effective when the treatment is carried out late after mixing.

C Mixed Ultrasonic Trigger System + Chemical Accelerator

The results are presented in the appendix, in Table 7 These results were obtained from a mortar comprising a cement coated with oil of Im. The mass of oil of Im with respect to the mass of cement is 3% The chemical accelerator is sodium metasilicate

The awakening is carried out at 1 day of the mixing In the first case, only the chemical accelerating agent is added to the awakening In the second case, the chemical agent is coupled to an ultrasonic treatment

The mechanical strengths are obtained on 4x4x16 cm test pieces. From the results of the table above, it can be seen that the chemical treatment alone has no effect of setting acceleration, whereas this same chemical treatment coupled with a treatment ultrasound induces the desired acceleration of the grip, through a synergy of action

D Tempering and hydration in cold weather

The results are presented in the appendix, in table 8 These results were obtained from a mortar without addition of retarder (or retarding agent) The application of ultrasounds is done at 5 minutes of the mixing

The mixing and the hydration are carried out at 10 ^° C.

The mechanical strengths are obtained on 4x4x16 cm test specimens. From the results of Table 8, it can be seen that the ultrasound has a setting acceleration effect on a non-retarded mortar, at a temperature of 10 ^c C, regardless of the duration of treatment

It should be noted, however, that there is also a correlation between the duration of ultrasound treatment and the intensity of the acceleration of setting more the duration of treatment is long, the more the acceleration of setting is important E Tests on concrete Impact of acoustic wave frequency and treatment time on hydration gain

The term "hydration gain" according to the present invention the time of hydration gained from a concrete treated according to the invention compared to an untreated control concrete

The results are shown in FIG. 5 in the appendix. These results were obtained from a concrete comprising, as a retarder, sodium gluconate dosed at 0.28 parts by weight of dry matter per 100 parts by weight of cement L '. application of the acoustic waves is carried out at 18 hours of mixing and for varying periods of stirring Three frequencies have been tested (3.5 and 20 kHz), for a power of 750 or 2000 W

It should be noted that the setting time is obtained from the hydration curves by thermal follow-up of the sample. In the so-called "dormant" period which follows the mixing, the minimum temperature is recorded. After this minimum, the temperature increases. again, and when reaching an elevation of + 1 ° C from the minimum, the corresponding time-out is chosen as the thermal setting time

According to FIG. 5, the lower the frequency of the acoustic waves, the greater the gain in hydration, for the same duration of treatment.

For example, for a processing time of 90 seconds, acoustic waves of 20 kHz frequency allow 4 hours of hydration gain, while acoustic waves of 3.5 kHz frequency allow 7 hours of hydration gain D on the other hand, the decrease in the frequency of the acoustic waves makes it possible to reduce the treatment time of the concrete, for the same gain in hydration

Indeed, for a hydration gain of 10 hours, the use of acoustic waves of 20 kHz frequency allows a treatment time of 225 seconds, while the use of acoustic waves of 3.5 kHz frequency allows 170 seconds of processing time Table A

Table 3

Table 7

Claims

A method of triggering and / or accelerating setting of a water-resistant, non-refractory pasty material selected from the group consisting of concrete, mortar and cement paste, in which low frequency acoustic waves and / or or ultrasonic high power are applied to said material, said waves inducing said triggering and / or said setting acceleration.

2. The method of claim 1, wherein the setting of said material has been previously delayed by the administration of a retarding agent.

3. Method according to claim 1 or 2, wherein said acoustic waves induce a cavitation phenomenon.

4. Method according to any one of claims 1 to 3, wherein the acoustic waves have a frequency between 100 Hz and 100 kHz, preferably between 100 Hz and 60 kHz, preferably between 200 Hz and

40 kHz.

5. Method according to any one of claims 1 to 4, wherein the acoustic waves are ultrasound,

6. The method of claim 5, wherein the ultrasound has a frequency between 15 kHz and 100 kHz, preferably between 20 kHz and 60 kHz, preferably between 20 kHz and 40 kHz.

7. A method according to any one of claims 1 to 4, wherein the acoustic waves are low frequency acoustic waves.

8. The method of claim 7, wherein the low frequency acoustic waves have a frequency greater than or equal to 100 Hz and strictly less than 15 kHz, advantageously between 100 Hz and 10 kHz, particularly preferably between 100 Hz and 3.5 kHz

Process according to any one of 1 to 8, wherein the pasty material is a concrete

Method according to any one of claims 1 to 9, wherein the power of the acoustic waves is between 0 5 kW and 20 kW, preferably between 1 kW and 10 kW, preferably between 2 and 6 kW

Process according to one of Claims 1 to 10, in which the quantity of material treated per minute is between at least 0.2 and 4 m ³ / min, preferably between 1 and 2 m ³ / min.

Process according to any one of Claims 1 to 1 1, in which the said material is introduced into a chamber emitting acoustic waves.

A process according to any of claims 2 to 12, wherein said retarding agent is selected from the group consisting of sugars and derivatives, carboxylates, phosphonates, zinc salts, borates and surfactants suitable for coating the surface of cement grains such as Im oil, stearates, cellulose ethers, alginates, acrylates