Insulating mineral foam

Abstract

A process for producing a mineral foam includes (i) separately preparing one or more slurries of cement, and an aqueous foam for which a D50 of bubbles is less than or equal to 400 m; (ii) homogenizing the one or more slurries of cement with the aqueous foam to obtain a slurry of foamed cement; (iii) casting the slurry of foamed cement and leaving the cast slurry of foamed cement to set.

Claims

1. A process for production of a mineral foam continuously comprising: (i) separately preparing one or more slurries of cement, and an aqueous foam for which a D50 of bubbles is less than or equal to 400 m; (ii) homogenizing the one or more slurries of cement with the aqueous foam to obtain a slurry of foamed cement; (iii) casting the slurry of foamed cement without interruption and leaving the cast slurry of foamed cement to set, wherein said slurry of foamed cement comprises at least, in % by mass relative to the mass of the slurry of foamed cement: from 20 to 70% of cement; from 1 to 5% of calcium sulfate; from 0.5 to 10% of calcium aluminate cement; from 0.05 to 3% of a water reducer, a plasticizer or a superplasticizer; from 0.001 to 0.5% of a retarder; from 0.1 to 5% of a foaming agent; from 15 to 40% of water; the calcium aluminate cement/calcium sulphate ratio being from 0.5 to 2.5, wherein said calcium aluminate cement and said calcium sulphate are expressed in mass percentage; the calcium sulphate/cement ratio being from 0.03 to 0.09; wherein said calcium sulphate and said cement are expressed in mass percentage.

2. The process for production of a mineral foam according to claim 1, wherein step (i) comprises the preparation of two slurries of cement, one of which is a slurry of calcium aluminate cement.

3. The process for production of a mineral foam according to claim 1, wherein step (ii) comprises the introduction of the slurry or slurries of cement and the aqueous foam into a static mixer to obtain a slurry of foamed cement.

4. The process for production of a mineral foam according to claim 1, wherein the aqueous foam is generated continuously.

5. The process for production of a mineral foam according to claim 1, wherein the one or more slurries of cement is/are generated continuously.

6. The process for production of a mineral foam according to claim 3, wherein the static mixer includes elements in the form of a propeller to ensure complete radial mixing and successive divisions of flow for each combination of liquids and gas.

7. The process for production of a mineral foam according to claim 3, wherein the static mixer includes helical elements which transmit a radial speed to fluid, which is directed alternatively towards a side of the mixer, then towards a centre of the mixer.

8. The process for production of a mineral foam according to claim 1, wherein the slurry of foamed cement comprises a foaming agent that is a protein.

9. The process for production of a mineral foam according to claim 8, wherein the foaming agent is keratin.

10. A process for production of a mineral foam continuously comprising: (i) separately preparing one or more slurries of cement, and an aqueous foam for which the D50 of the bubbles is less than or equal to 400 m; (ii) homogenizing the one or more slurries of cement with the aqueous foam to obtain a slurry of foamed cement; (iii) casting the slurry of foamed cement without interruption and leave it to set; wherein said slurry of foamed cement comprises at least, in % by mass relative to the mass of the slurry of foamed cement: from 30 to 75% of cement described according to the European NF EN 197-1 Standard of February 2001 or mixtures thereof; from 10 to 70% of fine mineral particles with a D50 less than or equal to 5 m; from 0 to 15% of ultrafine mineral particles with a D50 less than or equal to 1 m; from 0.05 to 3% of a water reducer, a plasticizer or a superplasticizer; from 0.0001 to 1% of a retarder; from 0 to 0.1% of a thickening agent; from 0.01 to 5% of a foaming agent; from 0 to 0.5% of alkaline sulphates; from 0 to 1% of an accelerator; from 10 to 70% of water; the fine mineral particles/cement ratio being comprised from 0.27 to 0.6, wherein said fine mineral particles and said cement are expressed in mass percentage; the ultrafine mineral particles/fine particles ratio being comprised from 0 to 0.5, wherein said ultrafine mineral particles and said fine mineral particles are expressed in mass percentage.

11. The process for production of a mineral foam according to claim 10, wherein step (ii) comprises the introduction of the slurry or slurries of cement and the aqueous foam into a static mixer to obtain a slurry of foamed cement.

12. The process for production of a mineral foam according to claim 10, wherein the aqueous foam is generated continuously.

13. The process for production of a mineral foam according to claim 10, wherein the one or more slurries of cement is/are generated continuously.

14. The process for production of a mineral foam according to claim 11, wherein the static mixer have elements in the form of a propeller to ensure complete radial mixing and successive divisions of flow for each combination of liquids and gas.

15. The process for production of a mineral foam according to claim 11, wherein the static mixer have helical elements which transmit a radial speed to fluid, which is directed alternatively towards a side of the mixer, then towards a centre of the mixer.

16. The process for production of a mineral foam according to claim 10, wherein the slurry of foamed cement comprises a foaming agent that is a protein.

17. The process for production of a mineral foam according to claim 16, wherein the foaming agent is keratin.

Description

EXAMPLES

(1) Laser Granulometry Method

(2) In this specification, including the accompanying claims, particle size distributions and particle sizes are as measured using a Malvern MS2000 laser granulometer. Measurement is effected in ethanol. The light source consists of a red HeNe laser (632 nm) and a blue diode (466 nm). The optical model is that of Mie and the calculation matrix is of the polydisperse type.

(3) The apparatus is checked before each working session by means of a standard sample (Sibelco 010 silica) for which the particle size distribution is known.

(4) Measurements are performed with the following parameters: pump speed 2300 rpm and stirrer speed 800 rpm. The sample is introduced in order to establish an obscuration between 10 and 20%. Measurement is effected after stabilisation of the obscuration. Ultrasound at 80% is first applied for 1 minute to ensure the de-agglomeration of the sample. After about 30 s (for possible air bubbles to clear), a measurement is carried out for 15 s (15000 analysed images). Without emptying the cell, measurement is repeated at least twice to verify the stability of the result and elimination of possible bubbles.

(5) All values given in the description and the specified ranges correspond to average values obtained with ultrasound.

(6) Particle sizes greater than 200 m are generally determined by sieving.

(7) Materials:

(8) The cement is a Portland CEM 152.5 R cement from the Lafarge cement plant of Le Havre (Batch number: LHY-4062).

(9) The calcium sulphate is ground anhydrous calcium sulphate from the plant of Le Pin worked by Etex.

(10) The calcium aluminate cement is a Fondu cement from the Pyrallis company.

(11) The plasticizer is a mixture comprising a polycarboxylate polyoxide (PCP) from the Chryso company under the brand name of Chrysolab EPB 530-017; it is based on Premia 180 which does not comprise an anti-foaming agent.

(12) The retarder is a pure anhydrous citric acid from the Verre Labo Mule company.

(13) The foaming agent is the Propump 26, an animal protein from the Propump company: the molecular weight of Propump 26 is 6000 Daltons.

(14) The mineral particles are calcium carbonate supplied by OMYA under the following brand names: Betocarb HP Entrains wherein the D50 is 7.8 m, and having a maximum particle size of 200 m (Batch number: ADD-0549); Durcal 1 wherein the D.sub.50 is 2.5 m, and having a maximum particle size of 20 m (Batch number: ADD-0613); Durcal 1 wherein the D.sub.50 is 3.5 m, and having a maximum particle size of 20 m (Batch number: ADD-00662); Socal 31 wherein the D.sub.50 is 90 nm, (Batch number: MCC-265).

(15) The thickening agent is either a biopolymer from the CP Kelco company commercialised under the brand name of Kelco-Crete 200.

(16) The accelerator is calcium nitrite from Chryso commercialised under the brand name of SET 02.

(17) The LiCO3 is lithium carbonate from the Aldrich company.

(18) Water: tap water.

(19) Materials:

(20) The Rayneri Mixers: A mixer: model R 602 EV (2003) supplied by the Rayneri company. The mixer is composed of a chassis on which vessels are positioned (capacity: 10 to 60 liters). The 60-liter blade was used with a paddle type of blade adapted to the volume of the vessel. This paddle is entrained by an electric motor operating on 380 Volts at a variable speed. The blade exerts a rotation movement around itself, accompanied by a planetary movement around the axis of the vessel. A Turbotest mixer (MEXP-101, model: Turbotest 33/300, Serial N: 123861) supplied by the Rayneri company. It was a mixer with a vertical axis.

(21) In the following examples, 9 mineral foams according to the invention were produced. They are numbered 1 to 9. Each cement slurry and each aqueous foam carries the same number as the obtained mineral foam.

(22) 1/Production of Mineral Foams 1 to 5 According to the Invention Comprising Cement and Calcium Aluminate Cement (Variant 1):

(23) Production of Slurries of Cement and Calcium Aluminate Cement:

(24) Tables 1 and 2 herein below give the chemical compositions of the different cement slurries and of the aqueous foam which were used.

(25) The slurry of Portland cement and the slurry of calcium aluminate cement were produced using the Rayneri R 602 EV mixer.

(26) TABLE-US-00001 TABLE 1 Formulations of cement slurries and slurries of calcium aluminate cement.sup.(1) 1 2 3 4 5 Slurry of CEM I 52.5 R 42.34 42.34 55.7 56.15 56.15 cement Cement Betocarb HP Entrains 38.48 38.48 0 0 0 Durcal 1 (batch ADD- 0 0 22.41 22.59 22.59 0613) calcium sulphate 2.12 2.12 3.90 2.81 2.81 (CaSO.sub.4) Water 16.94 16.94 17.82 18.02 18.02 Plasticizer 0.13 0.13 0.16 0.17 0.17 Slurry of Calcium aluminate 73.8 73.8 73.8 73.8 73.8 calcium cement aluminate Water 25.83 25.83 25.83 25.83 25.83 cement Citric acid 0.37 0.37 0.37 0.37 0.37 .sup.(1)The quantities in Table 1 are given in % by mass relative to the total mass of each slurry.

(27) TABLE-US-00002 TABLE 2 Formulation of the aqueous foam.sup.(3) 1 2 3 4 5 Foaming agent: Propump 26.sup.(2) 4.5 4.5 4.5 4.5 4.5 Water 95.5 95.5 95.5 95.5 95.5 .sup.(2)the quantity of Propump 26 is the quantity of active material for the commercial product. .sup.(3)the quantities of Table 2 are given in % by mass relative to the total mass of aqueous foam (water + foaming agent)

(28) Production of a Slurry of Foamed Cement According to the Invention:

(29) The production of slurries of foamed cement (1 to 5) was carried out in a continuous manner. The cement slurries, obtained beforehand, were each poured separately into a buffer vessel whilst being stirred in a Rayneri Turbotest mixer (MEXP-101) comprising a deflocculating blade (the speed of the blade could vary from 1000 rpm to 400 rpm depending on the volume of the slurry). The slurries were pumped for the flow rates given in Table 3 using a Moineau volumetric pump: Seepex MD 003-12 helical rotor pumpcommission N: 245928 for the slurry of calcium aluminate cement; and Seepex BN025-12 helical rotor pumpcommission N 244921 for the cement slurry;

(30) Table 3 herein below presents the flow values of each ingredient (cement slurry and aqueous foam) used to produce the slurries of foamed cement according to the invention.

(31) TABLE-US-00003 TABLE 3 Flow rates of the cement slurries and the slurries of calcium aluminate cement and the aqueous foam 1 2 3 4 5 Cement slurry.sup.(4) 1584 2906 3197 3302 3370 Slurry of calcium 30.95 58.4 124.28 124.28 184.67 aluminate cement.sup.(4) Aqueous foam.sup.(4) 288.18 288.18 263.4 279.92 288.18 Average D50 of the 250 250 250 250 250 bubbles of the mineral foam (m) Air flow rate in L/min 4.5 4.5 4.5 4.5 4.5 .sup.(4)the flow rates are given in g/min

(32) Production of the Aqueous Foam: The aqueous solution of the foaming agent was co-introduced through the foamer.sup.(*) with the pressurized air (within a range of 1 to 6 bars) using a T junction. The aqueous foam was generated in a continuous manner at the flow rate given in Table 3, .sup.(*) (bed of SB30 glass beads with a diameter comprised from 0.8 to 1.4 mm, packed in a tube: length 100 mm and diameter 12 mm).

(33) The slurry of cement and the slurry of calcium aluminate cement were combined to obtain a third slurry of cement. Then, the third slurry of cement was combined with the aqueous foam already circulating in the circuit of the process. The slurry of foamed cement according to the invention was thus generated. The static mixer was the Kenics type of mixer, supplied by Robbins & Myers Inc., with 16 elements, interior diameter: 20 mm, length: 260 mm.

(34) Five slurries of foamed cement were obtained, numbered from 1 to 5; their compositions are given in Table 4 herein below.

(35) TABLE-US-00004 TABLE 4 Formulations of the slurries of foamed cement.sup.(6) 1 2 3 4 5 CEM I 52.5 R Cement 35.24 36.33 49.68 50.14 49.29 calcium sulphate (CaSO.sub.4) 1.76 1.82 3.48 2.51 2.46 Calcium aluminate cement 1.20 1.77 2.56 2.48 3.59 Betocarb HP Entrains 32.02 33.01 0 0 0 Durcal 1 (batch ADD-0613) 0 0 19.99 20.18 19.83 Plasticizer 0.11 0.11 0.15 0.15 0.15 Citric acid 0.01 0.01 0.01 0.01 0.02 Foaming agent.sup.(5) 0.68 0.53 0.33 0.34 0.34 Water 30.34 27.48 24.53 24.89 25.00 CaSO4/cement ratio 0.05 0.05 0.07 0.05 0.05 Calcium aluminate cement/ 0.68 0.97 0.73 0.98 1.46 CaSO4 ratio .sup.(5)the quantity of foaming agent is the quantity of active material for the commercial product. .sup.(6)the quantities of Table 4 are given in % by mass relative to the total mass of the slurry of foamed cement

(36) Production of Mineral Foams According to the Invention:

(37) The slurries of foamed cement 1 to 5 were then either poured into columns of Plexiglas: 1 or 2 meters in height and 10 cm diameter, or into 101010 cm-side cubes of polystyrene. The cubes were demoulded after 24 h00 and kept for 28 days at 100% of relative humidity and 20 C. The columns were demoulded after 24 h00, kept for 7 days at 100% of relative humidity and 20 C., then dried at 45 C. until their mass remained constant.

(38) Stability of the Mineral Foams According to the Invention:

(39) After drying at 45 C. and obtaining a constant mass, sections in the columns were cut at 2 cm from the bottom and 2 cm from the top of the column. The sections were 10 centimeters high. The sections were carefully measured and the densities were evaluated. The density obtained at the bottom of the column and the difference of density between the top and the bottom of the column are recorded in Table 5.

(40) TABLE-US-00005 TABLE 5 Stability of the columns 1 2 3 4 5 Dry density at the bottom of the 271 447 467 466 471 column (kg/m.sup.3) Difference of density between 0.4 7.5 n.d. n.d. n.d. the top and bottom on the 1-metre column (in %) Difference of density between n.d. n.d. 17.6 14 17.63 the top and bottom on the 2-metre column (in %) n.d. not determined

(41) Thermal Conductivity of the Mineral Foams According to the Invention:

(42) Thermal conductivity was measured using a thermal conductivity measuring device: the CT-meter (Resistance 5, probe wire 50 mm). The samples were dried in a drying oven at 45 C. until their mass remained constant. The sample was then cut into two equal pieces using a saw. The measurement probe was placed between the two flat sides of these two half samples (the sawed sides). Heat was transmitted from the source towards the thermocouple through the material surrounding the probe. The rise in temperature of the thermocouple was measured over time and the thermal conductivity of the sample was calculated.

(43) The values are given in Table 6.

(44) TABLE-US-00006 TABLE 6 Thermal conductivity 1 2 3 4 5 Thermal conductivity 0.114 0.188 0.159 0.166 0.164 (W/m .Math. K)

(45) Mechanical Compressive Strengths of the Mineral Foams:

(46) The mechanical strength was tested on the 101010 cm cubes. Each sample was submitted to mechanical compressive stress until failure of the sample using a Zwick press (PRES-0018-1997/03). The maximum force exerted on the surface of the sample was measured in this manner. A compressive strength was deduced. The measurements were carried out in a temperature-stabilised environment (23 C.) and 50% relative humidity. The results obtained are given in Table 7. Each value is an average of three measurements.

(47) TABLE-US-00007 TABLE 7 Compressive strength 1 2 3 4 5 Compressive strength (Pa) 0.21 1.29 2.73 2.66 2.83

(48) 2/Production of Mineral Foams 6 to 8 According to the Invention Comprising Cement and Fine Particles (Variant 2)

(49) Production of Slurries of Portland Cement:

(50) Tables 8 and 9 herein below present the chemical compositions of the slurries of cement (Table 8) and the aqueous foam (Table 9) which were used.

(51) TABLE-US-00008 TABLE 8 Formulation of slurries of cement.sup.(7) 6 7 8 CEM I 52.5 R cement 58.88 58.88 56.42 Durcal 1 (batch: ADD-00662) 22.08 22.08 21.08 Socal 31 0 0 4.23 Plasticizer 0.26 0.26 0.34 Retarder 0.24 0.24 0.23 Water 18.53 18.53 17.71 W/C 0.31 0.31 0.31 Fines/cement ratio 0.375 0.375 0.373 Ultra fines/fines ratio 0 0 0.2 .sup.(7)The quantities in Table 8 are given in % by mass relative to the total mass of each slurry.

(52) TABLE-US-00009 TABLE 9 Formulation of aqueous foam .sup.(9) 6 7 8 Foaming agent Propump 26.sup.(8) 4.24 4.5 4.24 Accelerator 15.38 0 15.28 thickening agent 0.07 0 0 Water 80.32 95.5 80.47 .sup.(8)the quantity of Propump 26 is the quantity of active material of the commercial product. .sup.(9) The quantities in Table 9 are given in % by mass relative to the total mass of aqueous foam (water + foaming agent)

(53) Production of a Slurry of Foamed Cement According to the Invention:

(54) The production of slurries of foamed cement (6 to 8) was carried out in a continuous manner. The cement slurries, obtained beforehand, were poured into a buffer vessel whilst being stirred in a Rayneri Turbotest mixer (MEXP-101) comprising a deflocculating blade (the speed of the blade could vary from 1000 rpm to 400 rpm depending on the volume of the slurry). The slurries were pumped for the flow rates given in Table 10 using a Moineau volumetric pump (Seepex MD 003-12 helical rotor pumpcommission N: 245928).

(55) Table 10 herein below presents the flow rates for each ingredient (slurry of cement and aqueous foam) used to produce the slurries of foamed cement according to the invention.

(56) TABLE-US-00010 TABLE 10 6 7 8 Cement slurry (g/min) 3370 4296 4072 Aqueous foam (g/min) 296 276 314 Average D50 of the bubbles of the 251 250 250 aqueous foam (m) Air flow rate (L/min) 5.2 5.2 5.2

(57) Production of the Aqueous Foam: The aqueous solution of the foaming agent was co-introduced through the foamer.sup.(*) with the pressurized air (within a range of 1 to 6 bars) using a T junction. The aqueous foam was generated in a continuous manner at the flow rate given in Table 10; .sup.(*) (bed of SB30 glass beads with a diameter comprised from 0.8 to 1.4 mm, packed in a tube: length 100 mm and diameter 12 mm).

(58) The slurry of cement and the aqueous foam already circulating in the circuit of the process were combined. The slurries of foamed cement according to the invention were then generated. The static mixer was the Kenics type of mixer supplied by Robbins & Myers Inc., with 16 elements, interior diameter: 20 mm, length: 260 mm.

(59) TABLE-US-00011 TABLE 11 Formulation of the slurries of foamed cements .sup.(11) 6 7 8 CEM I 52.5 R cement 54.94 55.47 52.62 Durcal 1 (lot ADD-00662) 20.60 20.80 19.66 Socal 31 0 0 3.95 Plasticizer 0.12 0.12 0.16 Retarder 0.05 0.06 0.05 Thickening agent 0.005 0 0 Foaming agent.sup.(10) 0.08 0.07 0.08 Accelerator 0.31 0 0.26 Water 24.23 23.48 23.23 Fine mineral particles/cement ratio 0.37 0.37 0.37 Ultrafine mineral particles/ 0 0 0.20 fine mineral particles ratio .sup.(10)the quantity of foaming agent is the quantity of active material for the commercial product. .sup.(11) the quantities of Table 11 are given in % by mass relative to the total mass of foamed cement slurry

(60) Production of Mineral Foams According to the Invention:

(61) The slurries of foamed cement 6 to 8 were then either poured into columns of Plexiglas: 1, 2 or 3 meters in height and 20 cm diameter, or into 101010 cm-side cubes of polystyrene. The cubes were demoulded after 24 h00 and kept for 28 days at 100% of relative humidity and 20 C. The columns were demoulded after 24 h00, kept for 7 days at 100% of relative humidity and 20 C., then dried at 45 C. until their mass remained constant.

(62) Stability of the Mineral Foams 6 to 8 According to the Invention:

(63) After drying at 45 C. and obtaining a constant mass, sections in the columns were cut at 2 cm from the bottom and 2 cm from the top of the column. The sections were 10 centimeters high. The sections were carefully measured and the densities were evaluated. The density obtained at the bottom of the column and the difference of density between the top and the bottom of the column are recorded in Table 12.

(64) TABLE-US-00012 TABLE 12 6 7 8 Dry density at the bottom of the column 487 537 568 (kg/m.sup.3) Difference of density between the top 7.6 8.9 10.7 and bottom on the 1-metre column (in %) Difference of density between the top 16.4 15 17 and bottom on the 2-metre column (in %) Difference of density between the top 23 24 24 and bottom on the 3-metre column (in %)

(65) Thermal Conductivity of the Mineral Foams 6 to 8 According to the Invention:

(66) Thermal conductivity was measured using a thermal conductivity measuring device: the CT-meter (Resistance 5, probe wire 50 mm). The samples were dried in a drying oven at 45 C. until their mass remained constant. The sample was then cut into two equal pieces using a saw. The measurement probe was placed between the two flat sides of these two half samples (the sawed sides). Heat was transmitted from the source towards the thermocouple through the material surrounding the probe. The rise in temperature of the thermocouple was measured over time and the thermal conductivity of the sample was calculated. The values are given in Table 13.

(67) TABLE-US-00013 TABLE 13 Thermal conductivity 6 7 8 Thermal conductivity (W/m .Math. K) 0.132 0.172 0.168

(68) Mechanical Compressive Strengths of the Mineral Foams 6 to 8:

(69) The mechanical strength was tested on the 101010 cm cubes. Each sample was submitted to mechanical compressive stress until failure of the sample using a Zwick press (PRES-0018-1997/03). The maximum force exerted on the surface of the sample was measured in this manner. A compressive strength was deduced. The measurements were carried out in a temperature-stabilised environment (23 C.) and 50% relative humidity. The results obtained are given in Table 14. Each value is an average of three measurements.

(70) TABLE-US-00014 TABLE 14 Compressive strength 6 7 8 Compressive strength (Pa) n.d. 2.31 2.96 n.d. not determined

(71) 3/Production of a Mineral Foam 9 According to the Invention Comprising Cement (Variant 3)

(72) The mineral foam 9 was produced according to the same process as the foams 6 to 8. This mineral foam 9 was produced from cement obtained from the clinker described in patent application WO 2006/018569 (cement A).

(73) The chemical composition of the cement slurry was the following:

(74) TABLE-US-00015 9 .sup.(12) Cement A 72.22 Thickening agent 0.02 Plasticizer 0.65 Water 27.11 .sup.(12) The quantities are given in % by mass relative to the total mass of each slurry.
The chemical composition of the aqueous foam was the following:

(75) TABLE-US-00016 9 .sup.(14) Foaming agent: Propump 26.sup.(13) 4.5 LiCO3 0.11 Water 95.4 .sup.(13)the quantity of foaming agent is the quantity of active material for the commercial product. .sup.(14) the quantities of the table are given in % by mass relative to the total mass of the aqueous foam (water + foaming agent)
Flow Rates of the Slurry of Cement and the Aqueous Foam

(76) TABLE-US-00017 9 Cement slurry (g/min) 4016 Aqueous foam (g/min) 259 Average D50 of the bubbles of the aqueous foam (m) 250 Air flow rate (L/min) 5.3
Formulation of the Slurry of Foamed Cement

(77) TABLE-US-00018 9 .sup.(16) Cement A 67.84 Plasticizer 0.31 Thickening agent 0.005 Foaming agent .sup.(15) 0.07 Lithium carbonate 0.0016 Water 31.78 .sup.(15) the quantity of foaming agent is the quantity of active material for the commercial product. .sup.(16) the quantities are given in % by mass relative to the total mass of the slurry of foamed cement

(78) TABLE-US-00019 9 Dry density for the bottom of the column 536 (kg/m.sup.3) Difference of density between the top 1.3 and bottom of the 1-metre column (in %) Difference of density between the top 19.4 and bottom of the 2-metre column (in %) Difference of density between the top 21 and bottom of the 3-metre column (in %)

(79) The obtained thermal conductivity value was 0.117 W/m.Math.K. The obtained compressive strength was 1.88 Pa.