CONDUCTIVE MORTAR

Abstract

Methods including preparing a mixture including a binder composition containing at least one binder and at least one mineral filler, and curing the mixture to produce a material having improved electrical conductivity at 20° C., where at least 20% by weight of the at least one mineral filler is iron-containing slag.

Claims

1. A method comprising: preparing a mixture including a binder composition comprising at least one binder and at least one mineral filler, and curing the mixture to produce a material having improved electrical conductivity at 20° C., wherein at least 20% by weight of the at least one mineral filler is iron-containing slag, and the improved electrical conductivity is present when the electrical resistance of the material containing iron-containing slag is decreased by a factor of at least 1.5 compared to a material which has the same composition but contains silica sand of the same particle size instead of the iron-containing slag, wherein the electrical resistance is a surface resistance measured according to AASHTO 95-11 or a volume resistance measured according to an electrochemical impedance spectroscopy (EIS) method.

2. The method as claimed in claim 1, wherein the binder composition comprises from 30 to 95% by weight of the at least one mineral filler, based on the total weight of the dry binder composition.

3. The method of claim 1, wherein the iron-containing slag comprises at least 8% by weight of iron, calculated as FeO, based on the weight of the iron-containing slag.

4. The method of claim 1, wherein the iron-containing slag is steel slag, or slag from an electric arc furnace, a casting ladle, a Linz-Donawitz process or an oxygen blowing process.

5. The method of claim 1, wherein the iron-containing slag is copper slag.

6. The method of claim 1, wherein the iron-containing slag has a particle size of not more than 16 mm.

7. The method of claim 1, wherein the binder composition comprises fine filler having a particle size of not more than 0.1 mm, the fine filler being selected from the group consisting of ground limestone, quartz flour, fine titanium dioxide, ground barite, silica dust and fine aluminum oxide, and mixtures thereof.

8. The method of claim 1, wherein the at least one binder comprises at least one mineral binder.

9. The method of claim 1, wherein the at least one binder comprises at least one aluminum silicate and at least one alkali metal silicate.

10. The method of claim 1, wherein the at least one binder comprises at least one epoxy resin and at least one hardener for the epoxy resin or at least one polyisocyanate and at least one polyol and is free of mineral binders.

11. A process for producing materials having an improved electrical conductivity at 20° C. in which all constituents of a binder composition comprising at least one binder and at least one mineral filler are mixed and the mixture is allowed to cure, where at least 20% by weight of the at least one filler is iron-containing slag and water is present during mixing of binder compositions which contain a mineral binder.

12. The process as claimed in claim 11, wherein the curing of the binder composition occurs with application of an electric potential to electrodes which are installed or embedded in the binder composition to be cured.

13. A material having an improved electrical conductivity at 20° C. obtained by the process as claimed in claim 11.

14. A method comprising preparing a sacrificial anode that comprises the material as claimed in claim 13.

15. A method comprising applying the material as claimed in claim 13 to a substrate, the material being applied as mortar, repair mortar, equalization mortar, screed, embedding mortar, render, grout, coating, floor coating, or equalizing composition.

16. The method as claimed in claim 1, wherein at least 60% by weight of the at least one mineral filler is the iron-containing slag.

17. The method as claimed in claim 1, wherein the binder composition comprises from 40 to 90% by weight of the at least one mineral filler, based on the total weight of the dry binder composition.

18. The method as claimed in claim 1, wherein the binder composition comprises from 50 to 85% by weight of the at least one mineral filler, based on the total weight of the dry binder composition.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0217] FIG. 1 shows: a schematic depiction of illustrative cross sections of slag particles having an irregular shape.

EXAMPLES

[0218] Working examples which are intended to illustrate the invention as described are presented below. Of course, the invention is not restricted to these working examples described.

[0219] “Ref.” means reference example

[0220] “Ex.” means example according to the invention.

[0221] Materials

[0222] All sands and slags were dried before use and divided by sieving into the desired particle size fractions. The particle size fractions were subsequently mixed in such a way that the particle size distribution of the sands used corresponded to a prescribed particle size distribution (sieving curve).

[0223] EOS sand is an electric furnace slag from Stahl Gerlafingen, Switzerland. The material used had an apparent density of about 3.3 kg/I and a content of iron, calculated as FeO, of about 19% by weight.

[0224] CS is NAstra® iron silicate granules, a vitreous copper slag, obtainable from Sibelco, Germany, having an apparent density of about 3.7 kg/I and a content of iron, calculated as FeO, of about 51% by weight.

[0225] HOS is a blast furnace lump slag from Hüttenwerke Krupp Mannesmann, Germany, obtainable from Hermann Rauen GmbH & Co., Germany. The material used had an apparent density of 2.9 kg/I and a content of iron, calculated as FeO, of about 3% by weight.

[0226] Raulit® is a blast furnace slag from DK-Recycling and Roheisen GmbH, Germany, obtainable under the tradename Raulit®-Mineralbaustoffgemisch from Hermann Rauen GmbH & Co., Germany. The material used had an apparent density of about 2.9 kg/I and a content of iron, calculated as FeO, of about 1% by weight.

[0227] HS is a slag sand from voestalpine AG, Austria. The material used had an apparent density of about 2.9 kg/I and a content of iron, calculated as FeO, of less than 1% by weight.

[0228] Sikadur®-42 HE is a three-component embedding mortar based on epoxy resin, obtainable from Sika Schweiz AG.

[0229] Determination of the Specific Electrical Surface Resistance (R.sub.OF)

[0230] The electrical surface resistance of the test specimens was measured at regular time intervals. For this purpose, the resistance was determined on one of the longitudinal surfaces of a 40×40×160 mm test specimen using the resistance measuring instrument Resipod, obtainable from Proceq, Switzerland. This is a 4-point measuring instrument. The electrodes are arranged linearly at a spacing of 50 mm. An electric current is applied to the outer electrodes and the potential difference between the inner two electrodes is measured. The current amplitude is selected automatically by the instrument as a function of the electrical resistance of the specimen and is typically in the range from 10 to 200 μA. This method corresponds to AASHTO 95-11. To avoid contact problems between electrodes and surface, the surface at which the measurement was carried out was briefly wetted with a sponge impregnated with saturated Ca(OH).sub.2 solution before each measurement.

[0231] Determination of the Specific Electrical Volume Resistance (R.sub.DU)

[0232] The specific volume resistance of the 40×40×160 mm test specimens was determined by the EIS method. For this purpose, stainless steel electrodes were applied to the ends (40×40 mm faces) of the test specimens so as to completely cover the faces. In order to ensure good contact between test specimen and electrode, a sponge which had been impregnated with a saturated calcium hydroxide solution was in each case clamped between test surface and electrode. The volume resistance of the test specimens was subsequently determined over a period of about 15 seconds by application of an amplitude signal of 100 mV with a frequency of 1 kHz or 10 kHz to the two stainless steel electrodes.

[0233] Determination of Flexural Tensile Strength and Compressive Strength

[0234] The flexural tensile strength and the compressive strength of test specimens having a size of 40×40×160 mm was determined in accordance with DIN EN 196-1.

[0235] 1. Cement Mortars

[0236] The composition of the mortars is indicated in Table 1. The compositions of the mortars differ only in terms of the sand used. The particle size distribution of the sands and the additives added were the same in all mixtures.

TABLE-US-00001 TABLE 1 Composition of the mortars Amount in % by weight Cement (type CEM I) 33.5 Silica sand or slag sand 0.06-2.2 mm 60 Ground limestone 4 Additives 2.5

[0237] Production and Storage of the Test Specimens

[0238] The dry constituents of the mortars, as indicated in Table 1, were homogeneously mixed. Water was subsequently added in such an amount that a W/C (weight ratio of water to cement) of 0.45 was obtained. The fresh mortar was well and homogeneously mixed for 3 minutes using a mechanical mixer. The processability of the mortars M1 to M4 was comparable. The mortars were introduced into steel molds having a size of 40×40×160 mm and stored covered in the formwork for 24 hours at 20° C. The test specimens were then taken from the formwork and stored at 57% relative atmospheric humidity at 20° C. or at 68% relative atmospheric humidity at 20° C.

[0239] Table 2 shows the specific electrical surface resistance R.sub.oF of the mortars M1 and M2 in kΩ.Math.cm as a function of the storage time and relative atmospheric humidity (r.h.). The specimen age is the age of the test specimens in days. The measured values are averages of measurements on in each case three test specimens.

TABLE-US-00002 TABLE 2 Ref. 1 Ex. 1 Ref. 2 Ex. 2 Mortar M1 M2 M1 M2 Sand Silica EOS Silica EOS Specific resistance Specific resistance Specimen R.sub.OF [kΩ .Math. cm] Factor* R.sub.OF [kΩ .Math. cm] Factor* age [days] Storage at 57% r.h. Storage at 68% r.h. 7 66 36 1.8 56 35 1.6 14 92 50 1.8 83 48 1.7 21 109 60 1.8 94 56 1.7 28 369 75 4.9 118 69 1.7 *Factor by which the specific electrical surface resistance of the material according to the invention is reduced in comparison with the reference material (resistance of M1/resistance of M2)

[0240] Table 3 shows the specific electrical volume resistance R.sub.DU of the mortars M1 to M4 after storage of the test specimens at 57% relative atmospheric humidity.

TABLE-US-00003 TABLE 3 Ref. 3 Ref. 4 Ex. 3 Ex. 4 Mortar M1 M3 M2 M4 Sand Silica HOS Sample Spec. resistance EOS CS age days] R.sub.DU [kΩ .Math. cm] F* [kΩ .Math. cm] F* [kΩ .Math. cm] F* 28 28.0 32.0 0.9 10.2 2.7 7.0 4.0 *F = Factor by which the specific electrical volume resistance of the mortars M2, M3 and M4 has been reduced in comparison with reference mortar M1 (resistance of M1/resistance of M2, M3 or M4)

[0241] It can be seen from Tables 2 and 3 that the mortars M2 and M4, which contain the iron-containing steel slag, have a significantly lower specific electrical resistance than the mortars M1 and M3. A lower electrical resistance means a better electrical conductivity.

[0242] Table 4 shows the compressive strength of the test specimens in MPa after storage at 21° C. and 68% relative atmospheric humidity.

TABLE-US-00004 TABLE 4 Ref. 5 Ex. 5 Mortar M1 M2 Sand Silica EOS Age of the test specimens [days] Compressive strength [MPa] 1 22 26 7 50 54 28 66 71

[0243] 2. Embedding Mortar Based on Epoxy Resin Sikadur®-42 HE component A (containing the epoxy resin) was mixed well in a weight ratio of 3:1 with the associated component B (containing the hardener) and a solid component having the composition indicated in Table 5 was subsequently added and mixed in well. The weight ratio of component A to component B to solid component was 3:1:34.

[0244] Table 5 shows the composition of the solid component.

TABLE-US-00005 TABLE 5 Constituent % by weight Mixture of ground limestone and ground barite, 24.9 <0.1 mm Silica sand or slag sand 0.12-3.2 mm* 74.6 Polycarboxylate ether* solution (20% by weight of 0.5 polycarboxylate ether dissolved in 80% by weight of benzyl alcohol) *comb polymer with carboxylic acid groups and polyethylene glycol side chains

[0245] Table 6 shows the strength, the type of sand used and the specific volume resistance (R.sub.DU) of the mortars M5 to M10 after storage of the test specimens at 20° C. and 57% relative humidity for 7 days.

TABLE-US-00006 TABLE 6 Ref. 6 Ref. 7 Ref. 8 Ref. 9 Ex. 6 Ex. 7 Mortar M5 M6 M7 M8 M9 M10 Sand Silica HOS Raulit HS EOS CS Compressive 103.9 117.2 116.3 113.2 120.3 115.9 strength [MPa] Flexural tensile 26.3 26.8 28.2 27.0 29.9 31.2 strength [MPa] Specific electrical 175 121 137 187 40 27 resistance R.sub.DU [MΩ .Math. cm] at 1 kHz Factor* 1.4 1.3 0.9 4.3 6.5 Specific electrical 17 12 14 21 5.2 3.1 resistance R.sub.DU [MΩ .Math. cm] at 10 kHz Factor* 1.4 1.2 0.8 3.2 5.5 *Factor by which the specific electrical volume resistance of the mortars M6 to M10 has been reduced in comparison with reference mortar M5 (resistance of M5/resistance of the mortar containing slag)

[0246] 3. Thermal Conductivity of an Embedding Mortar M11 According to the Invention

[0247] Sikadur®-42 HE component A (resin component based on epoxy resin) was mixed well in a weight ratio of 3:1 with the associated component B (hardener component based on amine hardener). A solid component consisting of: [0248] 252 g of EOS sand having a particle size of 0.12-0.25 mm, [0249] 86 g of a mixture of ground limestone and ground barite having a particle size of less than 0.1 mm and [0250] 1.4 g of commercial wetting agent

[0251] were subsequently mixed well into 40 g of this epoxy mixture.

[0252] Test specimens having a diameter of 30 mm and a height of 2 mm were produced by casting into appropriate molds and allowing to cure at 20° C. for 7 days.

[0253] The thermal conductivity of the embedding mortar M11 was 2.06 W/(m.Math.K). This is significantly higher than the thermal conductivity of a cured commercial, filler-free epoxy resin of typically 0.20 W/(m.Math.K).