METHOD FOR THE CONTINUOUS PRODUCTION OF A LOW-DENSITY MINERAL FOAM

Abstract

A method for the continuous production of a mineral foam of which the density in the dry state (d) is from 40 to 600 kg/m.sup.3, includes (i) mixing cement; a water reducing agent; 0.5 to 10%, % by weight with respect to the total weight of cement, of ultrafine particles having a liquid-solid contact angle comprised from 30° to 140°, and of which the D50 is from 10 to 600 nm; water, with a water/cement weight ratio from 0.3 to 2.5; (ii) adding to the mixture from 0.5 to 10% of a pore-forming agent, % by weight with respect to the weight of cement; (iii) applying the mixture obtained at step (ii) on a support; (iv) leaving the mixture to expand on the support.

Claims

1-13. (canceled)

14- A method for the continuous production of a mineral foam of which the density in the dry state (d) is comprised from 40 to 600 kg/m.sup.3, comprising the following steps: (i) mixing cement; a water reducing agent; 0.5 to 10%, % by weight with respect to the total weight of cement, of ultrafine particles having a liquid-solid contact angle comprised from 30° to 140°, and of which the D50 is comprised from 10 to 600 nm; water, with a water/cement weight ratio comprised from 0.3 to 2.5; (ii) adding to the mixture from 0.5 to 10% of a pore-forming agent, % by weight with respect to the weight of cement; (iii) applying the mixture obtained at step (ii) on a support; (iv) leaving the mixture to expand on the support.

15- The method according to claim 14, wherein the cement of the mixture of step (i) is a cement of which the Blaine specific surface area is comprised from 5000 to 9000 cm.sup.2/g.

16- The method according to claim 14, wherein there is no foaming agent in the mixture of step (i) or (ii).

17- The method according to claim 14, wherein the mixture of step (i) or step (ii) further comprises a transition metal salt.

18- The method according to claim 17, wherein the transition metal salt is a manganese salt or an iron salt.

19- The method according to claim 14, wherein the mixture of step (i) further comprises a mineral addition of which the particles have a D50 comprised from 0.1 to 4 mm.

20- The method according to claim 19, wherein the mineral addition is selected from the group consisting of a pozzolan, a slag, calcium carbonate, a fly ash, a sand and mixtures thereof.

21- The method according to claim 14, wherein the pore-forming agent added at step (ii) is a solution of hydrogen peroxide, a solution of peroxomonosulphuric acid, a solution of peroxodisulfphuric acid, a solution of alkaline peroxides, a solution of alkaline earth peroxides, a solution of organic peroxide, a suspension of particles of aluminium or mixtures thereof.

22- The method according to claim 21, wherein the organic peroxide is peroxoacetic acid or peroxobenzoic acid.

23- The method according to claim 14, wherein the mixture of step (i) further comprises a hydration accelerator of the cement.

24- The method according to claim 23, wherein the hydration accelerator is calcium chloride.

25- The method according to claim 14, wherein the mixture obtained at step (ii) is not fractionated.

26- The method according to claim 14, wherein at step (iii), the mixture is applied without using a spray nozzle.

27- The method according to claim 14 wherein step (iii) is carried out without a spray.

28- The method according to claim 14, wherein the support used at step (iii) is treated prior to the application of the mixture obtained at step (ii).

29- A mineral foam capable of being obtained according to the method of claim 14.

30- A method comprising utilizing the mineral foam according to claim 29 as insulation material.

31- The method according to claim 30, wherein the insulation material is a thermal or phonic insulation material.

Description

[0122] FIG. 1 is a diagram illustrating the principle of measuring a contact angle between a drop of water and a surface.

[0123] FIG. 2 is a diagram illustrating an exemplary embodiment of a device for implementing the method according to the invention.

[0124] In the example shown in FIG. 2, the device comprises a tank provided with a stirrer (1), a first pump (3), a first pipe (4), a static mixer (5), a second pump (6), a recipient (7), a second pipe (8), an output element (9) and a support (10). The mixture (2) is the mixture of step (i), and is contained in the tank (1). The pore-forming agent is contained in the recipient (7). They are continuously pumped independently by the pumps (3) and (6) and mixed by means of the static mixer (5). The pipe (8) and the output element (9) form a piping which may comprise additional elements of different sections and of different lengths. The dimensions (L1) and (D1) of the pipe (8) and the dimensions (L2) and (D2) of the output element (9) are chosen in such a way that the head losses in the piping remain compatible with the characteristics of the discharges, such as the flow rates and the speeds at the output of the piping, and with the pumping means. The pipe (8) and the output element (9) are also chosen as a function of the speed of release of oxygen in the piping, and in particular the ratio between the expected release in the piping and that expected after the output (11) of the piping, and the regularity of the flow. Generally, the diameter (D2) of the final part of the piping (output (11)) is chosen as a means of regulating the speed of ejection of the foam while maintaining the integrity of the jet. In the density range according to the invention, the expansion is not complete at the output of the piping (11), and ends on the support (10). Generally, at least 20% of the expansion remains to occur on the support (10).

[0125] Other embodiments of a device for applying the method according to the invention may be envisaged.

[0126] Method for Measuring a Wetting or Contact Angle:

[0127] FIG. 1 illustrates the principle for measuring a wetting angle between a solid surface 10 of a sample 12 made of concrete and a drop 14 of a liquid deposited on the surface 10. The reference 16 designates the liquid/gas interface between the drop 14 and ambient air. FIG. 1 is a cross-section along a plane perpendicular to the surface 10. In the section plane, the wetting angle α corresponds to the angle, measured from the inside of the drop 14 of liquid, between the surface 10 and the tangent T to the interface 16 at the point of intersection between the solid 10 and the interface 16.

[0128] To carry out the measurement of the wetting angle, the sample 12 is placed in a room at a temperature of 20° C. and a relative humidity of 50%. A drop of water 14 having a volume of 2.5 μL is placed on the surface 10 of the sample 12. The angle measurement is carried out by an optical method, for example using a drop shape analysis device, for example the DSA 100 device commercialised by Krüss. The measurements are repeated five times and the value of the contact angle measured between the drop of water and the support is equal to the average of these five measurements.

[0129] Particle Size Laser Method

[0130] The particle size curves of the different powders are obtained from a Mastersizer 2000 (year 2008, series MALI 020429) type laser particle size analyser sold by the Malvern Company.

[0131] The measurement is carried out in an appropriate medium (for example, in aqueous medium) in order to disperse the particles; the size of the particles must be comprised from 1 μm to 2 mm. The luminous source is constituted of a red He—Ne laser (632 nm) and a blue diode (466 nm). The optical model is that of Fraunhofer, the calculation matrix is of polydisperse type.

[0132] A background noise measurement is firstly carried out with a pump speed of 2000 rpm, a stirrer speed of 800 rpm and a noise measurement over 10 s, in the absence of ultrasounds. It is then checked that the luminous intensity of the laser is at least equal to 80%, and that a decreasing exponential curve is obtained for the background noise. If this is not the case, the lenses of the cell have to be cleaned.

[0133] A first measurement is next carried out on the sample with the following parameters: pump speed of 2000 rpm, stirrer speed of 800 rpm, absence of ultrasounds, obscuration limit between 10 and 20%. The sample is introduced to have an obscuration slightly greater than 10%. After stabilisation of the obscuration, the measurement is carried out with a duration between the immersion and the measurement set at 10 s. The measurement time is 30 s (30000 diffraction images analysed). In the granulogram obtained, it is necessary to take account of the fact that a part of the population of the powder may be agglomerated.

[0134] A second measurement is then carried out (without emptying the tank) with ultrasounds. The pump speed is taken to 2500 rpm, the stirring to 1000 rpm, the ultrasounds are emitted at 100% (30 watts). This regime is maintained for 3 minutes, then the initial parameters are returned to: pump speed of 2000 rpm, stirrer speed of 800 rpm, absence of ultrasounds. At the end of 10 s (to evacuate potential air bubbles), a 30 s measurement (30000 images analysed) is carried out. This second measurement corresponds to a powder de-agglomerated by ultrasound dispersion.

[0135] Each measurement is repeated at least twice to check the stability of the result. The apparatus is calibrated before each working session by means of a standard sample (silica C10 Sifraco) of which the particle size curve is known. All the measurements presented in the description and the ranges announced correspond to the values obtained with ultrasounds.

[0136] Method for Measuring the BLAINE Specific Surface Area

[0137] The specific surface of the different materials is measured as follows.

[0138] The Blaine method at 20° C. with a relative humidity not exceeding 65% using a Blaine Euromatest Sintco apparatus complying with the European standard EN 196-6. Before the measurement of the specific surface, the wet samples are dried in an oven until a constant weight is obtained at a temperature from 50 to 150° C. (the dried product is next ground to obtain a powder of which the maximum size of the particles is less than or equal to 80 μm).

EXAMPLES

[0139] The method according to the invention was put into effect to prepare mineral foams of formulas 391, 390-a, 390-b and 400. A comparative example 389 was also prepared in such a way as to highlight the advantageous aspects of the method according to the invention.

[0140] Materials:

[0141] The cement used is a Portland CEMI 52.R cement from the Lafarge Saint Pierre la Cour cement plant. The letter “R” corresponds to the definition of the Standard NF EN 197-1, version of April 2012. This cement was ground until a Blaine specific surface area of 8000 cm.sup.2/g was obtained.

[0142] The water reducing agent is a new generation high water reducing superplastifier, based on modified polycarboxylate sold under the name of Chryso Fluid Premia 180 and supplied by the Chryso Company. The dry content of Premia 180 is 50%, percentage by weight. The water reducing agent does not contain antifoaming agent.

[0143] The ultrafine particles are particles of precipitated calcium carbonate sold under the name Socal 312 and supplied by the Solvay PCC Company. These ultrafine particles have a contact angle varying from 90° to 130° as measured according to the method described above and a D50 of the particles of 40 nm as measured with the method described in the document EP1 740 649.

[0144] The transition metal salt is manganese sulphate monohydrate supplied by the Sigma Aldrich Company.

[0145] The mineral addition is a calcareous powder sold under the name of BL200 Orgon and supplied by the Omya Company for the formulas 389, 391, 390-a and 390-b and a Dunkirk slag (Origin Arcelor) for the formula 400. The D50 of BL200 is 6 μm and the D50 of the slag is 14.2 μm.

[0146] The hydration accelerator of the cement is aluminium sulphate of concentration 1 mole/l prepared from hydrated aluminium sulphate (14H.sub.20) in powder supplied by the VWR Company.

[0147] The pore-forming agent is 30% hydrogen peroxide supplied by the VWR Company.

[0148] The water is tap water.

[0149] Equipment Used:

[0150] Rayneri Mixers: [0151] A R 602 EV (2003) model mixer supplied by the Rayneri Company. The mixer is composed of a frame on which tanks ranging from 10 to 60 litres are positioned. The 10 L tank was used with a paddle type blade adapted to the volume of the tank. This blade exerts a rotational movement on itself accompanied by a planetary movement around the axis of the tank.

[0152] Pumps: [0153] A Seepex™ eccentric screw pump (I) of MD 006-24 type, commission n° 244920. [0154] A Seepex™ eccentric screw pump (II) of MD 006-24 type, commission n° 278702.

[0155] Static Mixer: [0156] A static mixer composed of 32 helicoidal elements of Kenics type of 19 mm diameter referenced 16La632 from ISOJET

[0157] I. Production of Mineral Foams

[0158] Preparation of the Paste for the Formulas 389, 391, 390-a and 390-b:

[0159] The paste is prepared by mixing the compounds of table I in the respective proportions indicated in said table. The paste is next mixed with water in a planetary mixer (Rayneri brand) for 5 min. The density of the foam in the fresh state after expansion is measured.

TABLE-US-00001 TABLE 1 Formulations 389 391 390-a 390-b 400 cement* 71.9 71.9 71.9 71.9 71.46 water reducing agent* 0.2 0.2 0.2 0.2 0.4 ultrafine particles* 4.83 4.83 4.83 4.83 4.8 transition metal salt* 0.72 1.43 0.36 0.36 1.6 mineral addition* 22.35 21.64 22.71 22.71 21.74 total 100 100 100 100 100 pore-forming agent** 7.1 4.6 3 5.6 4.5 water/cement*** 0.76 0.76 0.76 0.76 0.76 *the values are percentages expressed by weight with respect to the weight **percentages by weight with respect to the weight of cement ***ratio by weight

[0160] Before application of the foam on a breeze-block wall serving as support, the wall is treated, by means of a spray, by aspersion of a 1 mole/l solution of aluminium sulphate.

[0161] Then the paste is continuously pumped by means of a screw pump (Seepex (I) brand) in a main piping of 15 mm diameter. Simultaneously, the aqueous solution of hydrogen peroxide is pumped by means of another screw pump (Seepex (II) brand) and continuously injected into the piping in which the paste flows. The respective pumping flow rates are indicated in table 2. The mixing between the paste and the solution is accelerated by the presence of a static mixer placed in the main piping and located immediately downstream of the injection point of the hydrogen peroxide solution. The piping downstream of the mixer static is of a length of 5.5 m.

TABLE-US-00002 TABLE 2 Formulations 389 391 390-a 390-b Flow rate kg/min 5.5 5.5 5.5 5.5 Flow rate kg/min (H.sub.2O.sub.2) 0.590 0.37 0.24 0.52

[0162] The piping is equipped with an applicator (diameter adapter) which increases to 20 mm the diameter of the output tubing over a length of 20 cm.

[0163] It will be observed that the paste obtained at the output of the applicator is only partially aerated (less than 50% of the total fraction of oxygen is incorporated in the paste at this stage) and its expansion continues after deposition. The paste is deposited on the wall by the sole means of the output jet, which maintains its integrity up to the point of deposition. The density of the foam in the fresh state after expansion is measured.

[0164] The wall is covered by progressively varying the position of the deposition point, until the wall is entirely covered by the foam after complete expansion. A layer of around 3 cm is thereby obtained. The system is left as is until the setting of the cement has started, i.e. around 2.5 hours at ambient temperature.

[0165] The operation of deposition of foam is reiterated a second time, exactly in the same conditions as the first time. A second layer of around 3 cm is deposited. The paste is then floated to smooth out the unevenness and to give it a finished aspect.

[0166] Preparation of the Paste for the Formula 400:

[0167] The percentages being expressed by weight, the paste is prepared by mixing the following compounds:

[0168] 71.46% of cement ground until a Blaine specific surface area of 8000 cm.sup.2/g is reached.

[0169] 22.2% of Dunkirk slag

[0170] 4.80% of treated ultrafine particles (Socal 312 from Solvay PCC)

[0171] 1.6% of manganese sulphate monohydrate

[0172] 0.4% of Premia 180 superplastifier 4.5%, calculated with respect to the cement, of H.sub.2O.sub.2 are added in the form of a 30% solution.

[0173] II. Analysis of the Mineral Foam

[0174] II.1 Thermal Conductivity of Mineral Foams

[0175] The thermal conductivity (λ) was measured using a thermal conductivity measurement apparatus: CT-meter supplied by the Alphis-ERE Company (Resistance 50, 50 mm wire probe). The measurement was carried out on samples dried at 45° C. up to constant weight. The sample was next cut into two equal pieces using a saw. The measurement probe was placed between the two flat faces of these two halves of sample (sawn sides). Heat was transmitted from the source to the thermocouple through the material surrounding the probe. The rise in temperature of the thermocouple was measured as a function of time and made it possible to calculate the thermal conductivity of the sample.

[0176] II.2 Density of the Mineral Foams

[0177] The wet density of the foamed cement grouts was measured by weighing cubes at the moment of pouring and after complete expansion.

[0178] The dry density of the samples was measured on samples dried at 45° C. up to constant weight, still by weighing of cubes.

TABLE-US-00003 TABLE 3 Formulations 389 391 390-a 390-b 400 λ in W/m .Math. K 0.048 0.072 0.11 0.051 0.070 Density in the fresh state 80 200 340 98 189 in kg/m.sup.3 Density in the dry state 70 160 271 80 130 in kg/m.sup.3