Ultralight inorganic foam and manufacture method thereof

Abstract

A process for manufacturing an inorganic foam includes (i) separately preparing an aqueous foam and a cement slurry, the cement slurry including water W, a cement C, a water-reducing agent, a water-soluble calcium salt, a water-soluble silicate salt, the calcium/silicon molar ratio being 0.7 to 1.7 and the W/C weight ratio being 0.25 to 0.40, and given that the calcium ion concentration is 0.03 to 0.97%, expressed as weight percent relative to the weight of the cement, and that the silicate ion concentration is 0.04 to 1.67%, expressed as weight percent relative to the weight of the cement; (ii) contacting the cement slurry obtained with the aqueous foam to obtain a foamed cement slurry; and (iii) shaping the foamed cement slurry obtained in step (ii) and allowing setting to occur.

Claims

1. A process for manufacturing an inorganic foam comprising the following steps: (i) separately preparing an aqueous foam and a cement slurry, the cement slurry comprising water W, a cement C, a water-reducing agent, a water-soluble calcium salt, a water-soluble silicate salt, the calcium/silicon molar ratio being 0.7 to 1.7 and the W/C weight ratio being 0.25 to 0.40, wherein the calcium ion concentration is 0.03 to 0.97%, expressed as weight percent relative to the weight of the cement C, and the silicate ion concentration is 0.04 to 1.67%, expressed as weight percent relative to the weight of the cement C; (ii) contacting the cement slurry obtained with the aqueous foam to obtain a foamed cement slurry; and (iii) shaping the foamed cement slurry obtained in step (ii) and allowing setting to occur.

2. The process according to claim 1, wherein the calcium/silicon molar ratio is 0.8 to 1.5.

3. The process according to claim 1, wherein the W/C ratio is 0.28 to 0.35, expressed by weight.

4. The process according to claim 1, wherein the cement C is a cement of type CEM I, CEM II, CEM III, CEM IV or CEM V.

5. The process according to claim 1, wherein the cement has a Blaine specific surface area of 3,000 to 10,000 cm.sup.2/g.

6. The process according to claim 1, wherein the water-reducing agent comprises a plasticizer or superplasticizer.

7. The process according to claim 1, wherein the inorganic foam comprises a mineral addition.

8. The process according to claim 1, wherein the inorganic foam comprises substantially no fine particles.

9. The process according to claim 1, wherein the water-soluble calcium salt is selected from the group consisting of calcium chloride, calcium nitrate, calcium formate, calcium acetate, calcium chlorate, calcium bromide, calcium lactate, calcium nitrite, calcium propionate, calcium hydrogen carbonate, calcium iodide and mixtures thereof.

10. The process according to claim 1, wherein the water-soluble silicate salt is selected from the group consisting of the family of sodium silicates (metasilicate, orthosilicate, pyrosilicate), the family of potassium silicates (metasilicate, orthosilicate, pyrosilicate), silicic acid and mixtures thereof.

11. The process according to claim 5, wherein the cement has a Blaine specific surface area of 3,500 to 6,000 cm.sup.2/g.

12. An inorganic foam manufactured by the process according to claim 1.

13. The foam according to claim 12, wherein the foam has a dry density of 20 to 300 kg/m.sup.3.

14. The foam according to claim 12, wherein the foam has a thermal conductivity of 0.030 to 0.150 W/(m.Math.K).

15. A construction element comprising an inorganic foam according to claim 12.

16. A method comprising manufacturing an insulating material with the inorganic foam according to claim 12.

17. The method according to claim 16, wherein the insulating material is a thermal or sound insulator.

Description

EXEMPLARY EMBODIMENTS

(1) The process of the invention was put into practice to prepare inorganic foams according to the invention B, D, F, H, J, L, N, O from cement slurry of formulas II, IV, VI, VIII and X. Comparative examples of cement foams G, I, K, M obtained using cement slurries V, VII and IX were also prepared so as to show the advantageous aspects of the process of the invention.

(2) Materials:

(3) The cements used are Portland cements from various Lafarge cement plants identified by location name as specified in Table (I). These cements are standard type cements. The letters R and N correspond to the definition of standard NF EN 197-1, version of April 2012.

(4) The superplasticizer used is a mixture comprising a polycarboxylate polyoxide (PCP) from the Company Chryso called Chrysolab EPB530-017 and not comprising anti-foaming agent. The dry extract of Chrysolab EPB530-017 is 48%, percentage by weight.

(5) The calcium salt used is a mixture of calcium chloride and calcium nitrate from the Company Chryso called ChrysoXel CBP. The dry extract of Chrysoxel CBP is 52%, percentage by weight.

(6) The silicate salt used is a sodium silicate from Chryso called ChrysoJet RS38. The dry extract of ChrysoJet RS38 is 38%, percentage by weight.

(7) The foaming agents used are derivatives of animal proteins as follows:

(8) Propump26 from the Company Propump having a dry extract of 26%;

(9) MAPEAIR L/LA from the Company MAPE having a dry extract of 26%, percentage by weight.

(10) The water is tap water.

(11) Equipment Used:

(12) Rayneri Mixer:

(13) A Turbotest mixer (MEXP-101, model Turbotest 33/300, serial number: 123861) provided by the Company Rayneri. It is a vertical-axis mixer.
Pumps: A Seepex MD 006-24 eccentric screw pump, commission no. 244920. A Seepex MD 006-24 eccentric screw pump, commission no. 278702.
Foamer: A foamer composed of a bed of SB30 glass beads having a diameter of 0.8 to 1.4 mm packed in a tube of length 100 mm and diameter 12 mm.
Static Mixer: A static mixer composed of 32 helical elements of type Kenics, diameter 19 mm, item number 16La632 by ISOJET.

(14) In the following examples, inorganic foams were prepared. Each cement slurry is listed with a number from II to X and each aqueous foam is numbered 1 or 2. The cement foam (or inorganic foam according to the invention) obtained is a combination of one of these cement slurries with one of these aqueous foams.

(15) I. Preparation of Inorganic Foams

(16) I.1 Preparation of a Cement Slurry

(17) The chemical compositions of the various cement slurries used to carry out the invention are presented in Table I. The slurries were prepared using the Rayneri Turbotest 33/300 mixer by first loading the liquid components (water, water-reducing agent, calcium salts and silicate salts). Under stirring (1000 rpm), the solids (cement and all the materials in powder form) are gradually added. The slurry was then mixed for another 2 minutes.

(18) TABLE-US-00001 TABLE I Formulation of the cement slurries II IV V VI VII VIII IX X Cement type CEM I 52,5N CEM I 52,5N CEM I 52,5N CEM I 52,5N CEM I 52,5N CEM I 52,5N CEM I 52,5N CEM I 52,5N Lafarge plant Le Havre Le Havre Saint Pierre Saint Pierre Austria Austria Val Val La Cour La Cour d'Azergues d'Azergues W/C ratio 0.29 0.33 0.29 0.29 0.33 0.33 0.29 0.29 (by weight) Soluble Na2O eq. 0.22 0.22 0.66 0.68 0.30 0.30 0.40 0.40 (%) Cement (weight % 76.54 74.28 77.43 75.65 75.10 74.26 77.44 76.52 in the slurry) Water (weight % in 20.69 23.06 22.34 19.25 24.71 23.02 22.38 20.88 the slurry) Superplasticizer 0.19 0.16 0.23 0.24 0.19 0.21 0.20 0.23 (weight % in the slurry) Calcium salt 1.19 1.35 0 2.03 0 1.14 0 1.18 (weight % in the slurry) Sodium silicate 1.39 1.16 0 1.83 0 1.37 0 1.41 (weight % in the slurry) Calcium ions (dry 0.24 0.28 0 0.42 0 0.24 0 0.24 weight % relative to the cement) Silicate ions (dry 0.43 0.37 0 0.57 0 0.44 0 0.44 weight % relative to the cement) Ca/Si 1.07 1.45 0 1.38 0 1.04 0 1.04 molar ratio

(19) I.2 Preparation of the Aqueous Foam

(20) An aqueous solution containing the foaming agent was placed in a vessel. The composition of this aqueous solution of foaming agent (in particular the concentration and the nature of the foaming agent) is presented in Table II. The foaming agent solution was pumped through the Seepex MD 006-24 volumetric eccentric screw pump (commission no.: 278702).

(21) This foaming agent solution was passed through the bead bed of the foamer together with pressurized air (range from 1 to 6 bar) using a T-junction. The aqueous foam was generated continuously at the flow rate indicated in Table II.

(22) TABLE-US-00002 TABLE II formulation of aqueous foams and flow rate Aqueous foam number 1 2 Foaming Agent Propump26 MapeAIR L/LA Concentration (weight % relative 3.5 2.5 to the water of the aqueous foam) Air Flow Rate (L/min) 8 8 Solution Flow Rate (L/min) 0.418 0.410

(23) I.3 Preparation of a Foamed Cement Slurry:

(24) The previously obtained cement slurry was poured into the mixing vessel under stirring (400 rpm). The slurry was pumped using a Seepex MD 006-24 volumetric eccentric screw pump (commission no.: 244920).

(25) The pumped slurry and the preceding aqueous foam, generated continuously, were placed in contact in the static mixer. The aqueous foam is generated by abiding by the flow rates specified in Table II.

(26) The cement slurry is pumped at a flow rate of about 0.285 L/min in order to obtain a foamed cement slurry with a wet density of about 110 kg/m.sup.3 (example B, D, F, G, H, I, J, K, L, M, N). The foamed cement slurry is thus generated. The volume of cement slurry used is at this density about 33 L/m.sup.3 and the volume of aqueous foam about 967 L/m.sup.3.

(27) The cement slurry is pumped at a flow rate of about 0.160 L/min in order to obtain a foamed cement slurry with a wet density of about 85 kg/m3 (example O). The foamed cement slurry is thus generated. The volume of cement slurry used is at this density about 19 L/m.sup.3 and the volume of aqueous foam about 981 L/m.sup.3.

(28) I.4 Production of an Inorganic Foam

(29) The foamed cement slurry was cast into polystyrene cubes having sides of 101010 cm and into cylindrical columns 2.50 m in height and 20 cm in diameter. Three cubes were prepared for each foamed slurry. The cubes were unmoulded after 1 day and then stored for 7 days at 100% relative humidity and 20 C. The cubes were then dried at 45 C. to constant weight. A column was formed with some of the foamed slurries. The columns were unmoulded between 3 and 7 days later and then cut into sections 25 cm in length. The sections were dried at 45 C. to constant weight.

(30) II. Analysis of the Inorganic Foam

II.1 Stability of the Inorganic Foam

(31) The stability of the foams was measured simply by visual inspection of the cubes generated before unmoulding. A foam was described as stable if the cube concerned had retained a height of 10 cm after setting. A foam was characterized as unstable if the cube concerned had collapsed when setting. Each test was carried out on 3 cubes of 101010 cm. The results show similar behaviour between the 3 cubes. When applicable, the results expressed are the mean of these 3 cubes.

(32) A column was considered stable if the difference in density between the bottom section and the top section of the column did not exceed 5 kg/m.sup.3.

II.2 Thermal Conductivity of the Inorganic Foams

(33) Thermal conductivity was measured using a thermal conductivity measuring device: TC-meter provided by the Company Alphis-ERE (Resistance 5, wire probe 50 mm). Measurement was performed on samples dried at 45 C. to constant weight. The sample was then cut into two equal pieces using a saw. The measuring probe was placed between the two flat surfaces of these two sample halves (sawn sides). Heat was transmitted from the source to the thermocouple through the material surrounding the probe. The temperature increase of the thermocouple was measured as a function of time and allowed the thermal conductivity of the sample to be calculated.

II.3 Density of the Inorganic Foams

(34) The wet density of the foamed cement slurries was measured by weighing the cubes at the time of casting.

(35) The dry density of the samples was measured on the samples dried at 45 C. to constant weight, again by weighing the cubes.

II.4 Results

(36) The results are presented in Table III below.

(37) TABLE-US-00003 TABLE III Formula of the inorganic foam of the invention B D F G H I J K L M N O Aqueous foam 1 2 1 1 1 2 2 1 1 1 1 1 number Cement slurry II II IV V VI V VI VII VIII IX X VI formula Inorganic foam wet 114 113 104 105 105 108 107 112 105 110 107 85 density (g/L) Inorganic foam dry 62 nm nm nm 63 nm nm nm 58 nm nm 43 density (g/L) Stability (cube) Stable Stable Stable Not stable Stable Not stable Stable Not stable Stable Not stable Stable Stable Bubble size (mm) 1 < x < 2 1 < x < 2 <1 na >2 na 1 < x < 2 na >2 >2 Stability (column) Stable nm nm Not stable Stable Not stable Stable Not stable nm Not stable nm stable Lambda (W/K .Math. m) 0.045 nm nm na 0.048 na nm na 0.051 na nm 0.038 (TC - meter measurement) nm means not measured. na means not applicable. Not stable means that the foam collapsed.

II.5 Conclusions

(38) These examples make it possible to assess the role of the calcium salt/silicate salt weight ratio in the stability of an inorganic foam. For example, when the calcium/silicon molar ratio is 1.07, 1.45, 1.38 or 1.04, the foam is stable. In the absence of water-soluble calcium salts or water-soluble silicate salts, the foam becomes destabilized and collapses. It can be noted that, for the inorganic foams obtained according to the invention, the nature of the cement used does not influence the stability of the foam.

(39) The invention is not limited to the embodiments presented and other embodiments will be clearly apparent to persons skilled in the art.