Method for reducing or avoiding alkali-aggregate reaction in set concrete

Abstract

A method for reducing or avoiding an alkali-aggregate reaction in a cured concrete. The method includes providing a curable concrete mixture which includes alkali-sensitive aggregates (A), at least one organosilicon compound (B) and/or at least one siloxane (B2). Mass hydrophobization of the curable concrete mixture is achieved by way of adding at least one organosilicon compound (B) to the curable concrete mixture prior to its curing thereby reducing or avoiding an alkali-aggregate reaction in the cured concrete.

Claims

1-15. (canceled)

16. A method for reducing or avoiding an alkali-silica reaction in cured concrete, comprising: providing a curable concrete mixture, wherein the curable concrete mixture comprises alkali-sensitive aggregates (A), at least one organosilicon compound (B) and/or at least one siloxane (B2); wherein the at least one organosilicon compound (B) is selected from among at least one silane (B1) having a formula (1)
R.sub.aR.sup.1Si(OR.sup.2).sub.3-a   (1); wherein R is a monovalent SiC-bonded hydrocarbon radical having from 1 to 3 carbon atoms; wherein R.sup.1 is a monovalent SiC-bonded hydrocarbon radical having from 4 to 22 carbon atoms; wherein radicals R.sup.2 can be identical or different and are each a hydrogen atom or a monovalent hydrocarbon radical; and wherein a is 0 or 1, wherein the at least one siloxane (B2) comprises units having the formula (2)
R.sup.3.sub.bR.sup.4.sub.c(OR.sup.5).sub.dSiO.sub.(4-b-c-d)/2   (2); where radicals R.sup.3 can be identical or different and are each a monovalent, SiC-bonded, optionally substituted aliphatic hydrocarbon radical having from 1 to 3 carbon atoms or a divalent, optionally substituted, aliphatic hydrocarbon radical which has from 1 to 3 carbon atoms and bridges two units of the formula (2); wherein radicals R.sup.4 can be identical or different and are each a hydrogen atom or a monovalent, optionally substituted hydrocarbon radical; wherein radicals R.sup.5 can be identical or different and are each a monovalent, SiC-bonded, optionally substituted aromatic or aliphatic hydrocarbon radical having from 4 to 22 carbon atoms; wherein b is 0, 1, 2 or 3; wherein c is 0, 1, 2 or 3; wherein d is 0 or 1; wherein the sum of b+c+d is less than or equal to 3 and the sum b+d in at least 40% of the units of the formula (2) is 0 or 1; wherein at least one organosilicon compound (B) is an aqueous preparation which comprises at least one silane (B1) of the formula (1) and at least one siloxane (B2) of the formula (2); wherein the alkali sensitivity of the alkali-sensitive aggregates (A) is determined in accordance with the test method A set forth in the description (method using 3% strength NaCl solution) by means of the average swelling of three test specimens composed of the cured concrete mixture which are stored in a 3% strength NaCl solution; and wherein the average swelling of the three test specimens composed of a cured concrete mixture which contains alkali-sensitive aggregates (A) but no (B) (=reference specimen) is at least 0.1 mm/m after 168 days (steps A-1 to A-5 and repetition of the steps (B-1 to B4) ten times).

17. The method of claim 16, wherein the average swelling of the test specimens of a cured concrete mixture which contains alkali-sensitive aggregates (A) but no (B) (=reference specimen) is at least 0.2 mm/m after 168 days (steps A-1 to A-5 and repetition of the steps (B-1 to B4) ten times).

18. The method of claim 16, wherein the average swelling of the test specimens of a cured concrete mixture which contains alkali-sensitive aggregates (A) but no (B) (=reference specimen) is at least 0.3 mm/m after 168 days (steps A-1 to A-5 and repetition of the steps (B-1 to B4) ten times).

19. The method of claim 16, wherein the at least one organosilicon compound (B) is used in such an amount that the average swelling determined by the test method A of the test specimens composed of a cured concrete mixture which contains alkali-sensitive aggregates (A) and (B) is at least 20% lower than the average swelling of a cured concrete mixture which contains alkali-sensitive aggregates (A) but no (B) (=reference specimen) after a storage time of 168 days (steps A-1 to A-5 and repetition of the steps (B-1 to B4) ten times).

20. The method of claim 16, wherein the at least one organosilicon compound (B) is used in such an amount that the average swelling determined by the test method A of the test specimens composed of a cured concrete mixture which contains alkali-sensitive aggregates (A) and (B) is at least 30% lower than the average swelling of a cured concrete mixture which contains alkali-sensitive aggregates (A) but no (B) (=reference specimen) after a storage time of 168 days (steps A-1 to A-5 and repetition of the steps (B-1 to B4) ten times).

21. The method of claim 16, wherein the at least one organosilicon compound (B) is used in such an amount that the average swelling determined by the test method A of the test specimens composed of a cured concrete mixture which contains alkali-sensitive aggregates (A) and (B) is at least 40% lower than the average swelling of a cured concrete mixture which contains alkali-sensitive aggregates (A) but no (B) (=reference specimen) after a storage time of 168 days (steps A-1 to A-5 and repetition of the steps (B-1 to B4) ten times).

22. The method of claim 16, wherein the at least one organosilicon compound (B) is used in such an amount that the average swelling determined by the test method B of the test specimens composed of a cured concrete mixture which contains alkali-sensitive aggregates (A) and (B) is at least 20% lower than the average swelling of a cured concrete mixture which contains alkali-sensitive aggregates (A) but no (B) (=reference specimen) after a storage time of 168 days (steps A-1 to A-5 and repetition of the steps (B-1 to B4) ten times).

23. The method of claim 16, wherein the at least one organosilicon compound (B) is used in such an amount that the average swelling determined by the test method B of the test specimens composed of a cured concrete mixture which contains alkali-sensitive aggregates (A) and (B) is at least 30% lower than the average swelling of a cured concrete mixture which contains alkali-sensitive aggregates (A) but no (B) (=reference specimen) after a storage time of 168 days (steps A-1 to A-5 and repetition of the steps (B-1 to B4) ten times).

24. The method of claim 16, wherein the at least one organosilicon compound (B) is used in such an amount that the average swelling determined by the test method B of the test specimens composed of a cured concrete mixture which contains alkali-sensitive aggregates (A) and (B) is at least 40% lower than the average swelling of a cured concrete mixture which contains alkali-sensitive aggregates (A) but no (B) (=reference specimen) after a storage time of 168 days (steps A-1 to A-5 and repetition of the steps (B-1 to B4) ten times).

25. The method of claim 16, wherein the at least one organosilicon compound (B) is used in such an amount that both the average swelling determined by the test method A and the average swelling determined by the test method B of the test specimens composed of a cured concrete mixture which contains alkali-sensitive aggregates (A) and (B) are at least 20% lower than the average swelling of a cured concrete mixture which contains alkali-sensitive aggregates (A) but no (B) (=reference specimen) after a storage time of 168 days (steps A-1 to A-5 and repetition of the steps (B-1 to B4) ten times).

26. The method of claim 16, wherein the at least one organosilicon compound (B) is used in such an amount that both the average swelling determined by the test method A and the average swelling determined by the test method B of the test specimens composed of a cured concrete mixture which contains alkali-sensitive aggregates (A) and (B) are at least 30% lower than the average swelling of a cured concrete mixture which contains alkali-sensitive aggregates (A) but no (B) (=reference specimen) after a storage time of 168 days (steps A-1 to A-5 and repetition of the steps (B-1 to B4) ten times).

27. A method for reducing or avoiding an alkali-silica reaction in cured concrete, comprising: providing a curable concrete mixture, wherein the curable concrete mixture comprises alkali-sensitive aggregates (A), at least one organosilicon compound (B) and/or at least one siloxane (B2); wherein the at least one organosilicon compound (B) is selected from among at least one silane (B1) having a formula (1)
R.sub.aR.sup.1 Si(OR.sup.2).sub.3-a   (1), wherein R is a monovalent, SiC-bonded hydrocarbon radical having from 1 to 3 carbon atoms; wherein R.sup.1 is a monovalent, SiC-bonded hydrocarbon radical having from 4 to 22 carbon atoms; wherein radicals R.sup.2 can be identical or different and are each a hydrogen atom or a monovalent hydrocarbon radical; and wherein a is 0 or 1; wherein the at least one siloxane (B2) comprises units having the formula (2)
R.sup.3.sub.b(R.sup.4O).sub.cR.sup.5.sub.dSiO.sub.(4-b-c-d)/2   (2), wherein the radicals R.sup.3 can be identical or different and are each a monovalent, SiC-bonded, optionally substituted aliphatic hydrocarbon radical having from 1 to 3 carbon atoms or a divalent, optionally substituted, aliphatic hydrocarbon radical which has from 1 to 3 carbon atoms and bridges two units of the formula (2); wherein the radicals R.sup.4 can be identical or different and are each a hydrogen atom or a monovalent, optionally substituted hydrocarbon radical; wherein the radicals R.sup.5 can be identical or different and are each a monovalent, SiC-bonded, optionally substituted aromatic or aliphatic hydrocarbon radical having from 4 to 22 carbon atoms; wherein b is 0, 1, 2 or 3; wherein c is 0, 1, 2 or 3; wherein d is 0 or 1; wherein the sum of b+c+d is less than or equal to 3 and the sum b+d in at least 40% of the units of the formula (2) is 0 or 1; wherein the at least one organosilicon compound (B) is an aqueous preparation which contains at least one silane (B1) of the formula (1) and at least one siloxane (B2) of the formula (2); where this alkali sensitivity of the aggregate (A) is determined in accordance with the test method B set forth in the description (method using 10% strength NaCl solution) by means of the average swelling of three test specimens composed of the cured concrete mixture which are stored in a 10% strength NaCl solution; and wherein the average swelling of the three test specimens composed of a cured concrete mixture which contains alkali-sensitive aggregates (A) but no (B) (=reference specimen) is at least 0.2 mm/m after 168 days (steps A-1 to A-5 and repetition of the steps (B-1 to B4) ten times).

28. The method of claim 27, wherein the average swelling of the test specimens of a cured concrete mixture which contains alkali-sensitive aggregates (A) but no (B) (=reference specimen) is at least 0.3 mm/m after 168 days (steps A-1 to A-5 and repetition of the steps (B-1 to B4) ten times).

29. The method of claim 27, wherein the average swelling of the test specimens of a cured concrete mixture which contains alkali-sensitive aggregates (A) but no (B) (=reference specimen) is at least 0.4 mm/m after 168 days (steps A-1 to A-5 and repetition of the steps (B-1 to B4) ten times).

30. The method of claim 27, wherein the at least one organosilicon compound (B) is used in such an amount that the average swelling determined by the test method A of the test specimens composed of a cured concrete mixture which contains alkali-sensitive aggregates (A) and (B) is at least 20% lower than the average swelling of a cured concrete mixture which contains alkali-sensitive aggregates (A) but no (B) (=reference specimen) after a storage time of 168 days (steps A-1 to A-5 and repetition of the steps (B-1 to B4) ten times).

31. The method of claim 27, wherein the at least one organosilicon compound (B) is used in such an amount that the average swelling determined by the test method A of the test specimens composed of a cured concrete mixture which contains alkali-sensitive aggregates (A) and (B) is at least 30% lower than the average swelling of a cured concrete mixture which contains alkali-sensitive aggregates (A) but no (B) (=reference specimen) after a storage time of 168 days (steps A-1 to A-5 and repetition of the steps (B-1 to B4) ten times).

32. The method of claim 27, wherein the at least one organosilicon compound (B) is used in such an amount that the average swelling determined by the test method A of the test specimens composed of a cured concrete mixture which contains alkali-sensitive aggregates (A) and (B) is at least 40% lower than the average swelling of a cured concrete mixture which contains alkali-sensitive aggregates (A) but no (B) (=reference specimen) after a storage time of 168 days (steps A-1 to A-5 and repetition of the steps (B-1 to B4) ten times).

33. The method of claim 27, wherein the at least one organosilicon compound (B) is used in such an amount that the average swelling determined by the test method B of the test specimens composed of a cured concrete mixture which contains alkali-sensitive aggregates (A) and (B) is at least 20% lower than the average swelling of a cured concrete mixture which contains alkali-sensitive aggregates (A) but no (B) (=reference specimen) after a storage time of 168 days (steps A-1 to A-5 and repetition of the steps (B-1 to B4) ten times).

34. The method of claim 27, wherein the at least one organosilicon compound (B) is used in such an amount that the average swelling determined by the test method B of the test specimens composed of a cured concrete mixture which contains alkali-sensitive aggregates (A) and (B) is at least 30% lower than the average swelling of a cured concrete mixture which contains alkali-sensitive aggregates (A) but no (B) (=reference specimen) after a storage time of 168 days (steps A-1 to A-5 and repetition of the steps (B-1 to B4) ten times).

35. The method of claim 27, wherein the at least one organosilicon compound (B) is used in such an amount that the average swelling determined by the test method B of the test specimens composed of a cured concrete mixture which contains alkali-sensitive aggregates (A) and (B) is at least 40% lower than the average swelling of a cured concrete mixture which contains alkali-sensitive aggregates (A) but no (B) (=reference specimen) after a storage time of 168 days (steps A-1 to A-5 and repetition of the steps (B-1 to B4) ten times).

36. The method of claim 27, wherein the at least one organosilicon compound (B) is used in such an amount that both the average swelling determined by the test method A and the average swelling determined by the test method B of the test specimens composed of a cured concrete mixture which contains alkali-sensitive aggregates (A) and (B) are at least 20% lower than the average swelling of a cured concrete mixture which contains alkali-sensitive aggregates (A) but no (B) (=reference specimen) after a storage time of 168 days (steps A-1 to A-5 and repetition of the steps (B-1 to B4) ten times).

37. The method of claim 27, wherein the at least one organosilicon compound (B) is used in such an amount that both the average swelling determined by the test method A and the average swelling determined by the test method B of the test specimens composed of a cured concrete mixture which contains alkali-sensitive aggregates (A) and (B) are at least 30% lower than the average swelling of a cured concrete mixture which contains alkali-sensitive aggregates (A) but no (B) (=reference specimen) after a storage time of 168 days (steps A-1 to A-5 and repetition of the steps (B-1 to B4) ten times).

Description

EXAMPLES

Production Example 1: Production of a Dispersion Containing Silane (B1) and Siloxane (B2)

[0136] 38.4 g of water, 38.4 g of emulsifier (POE(16)isotridecyl ether, obtainable under the name Arlypon® IT 16 from BASF AG, D-Ludwigshafen), are placed in a 2 liter beaker and mixed with 4.3 g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (obtainable under the name Geniosil® GF 91 from Wacker Chemie AG, D-Burghausen) by means of a rotor-stator homogenizer (Ultra-Turrax T50, IKA-Werke GmbH 6 Co.KG, D-Staufen) for 0.5 min at 4000 rpm. 100 g of 2,2,4-trimethylpentyltriethoxysilane (obtainable under the name SILRES® BS 1701 from Wacker Chemie AG, D-Burghausen) are subsequently added and the mixture is mixed for 2 min at 4000 rpm, forming a gel-like paste.

[0137] While continuing to mix at 4000 rpm, 10 g of water and 122.4 g of an organopolysiloxane of the formula (CH.sub.3).sub.0.7(2,2,4-trimethylpentyl).sub.0.3Si(OCH.sub.3).sub.1.3O.sub.0.85 having an average molecular weight of about 800 g/mol and a viscosity of about 17 mm.sup.2/s are subsequently added alternately within 2 minutes, with the paste-like consistency of the mixture being maintained. Finally, while continuing to mix at 4000 rpm, 25 g of water and 389.6 g of 2,2,4-trimethylpentyltriethoxysilane are added alternately within 3 minutes, with the paste-like consistency of the mixture likewise being maintained. The mixture is subsequently stirred for a further 5 minutes at 4000 rpm.

[0138] While continuing to mix at 4000 rpm, 467.8 g of water are then added alternately within 5 minutes, forming a liquid emulsion. Finally, 1.1 g of 99% strength acetic acid, 2.64 g of a first preservative (“Acticide MV”, obtainable from Thor GmbH, D-Speyer) and 0.36 g of a second preservative (MIT 10, likewise obtainable from Thor GmbH, D-Speyer) are added and stirred in for 0.5 min at 4000 rpm.

[0139] Building Materials and Test Methods

[0140] Concrete Compositions and Test Specimens

[0141] The concrete compositions are shown in table 3 and table 4. The formulations of comparative example 1 (C-Ex. 1) and examples 1a & 1b (Ex. 1a & Ex. 1b) are identical with the exception of the addition of the respective hydrophobizing agent. The same applies to the concretes of comparative example 2 (C-Ex. 2) and examples 2a & 2b (Ex. 2a & Ex. 2b). With the exception of the air pore former which was not used in the model experiments, all formulations correspond to the standard composition “Oberbeton (0/8)” which according to the general circular Straßenbau No. 04/2013 is to be used for the WS basic testing of coarse rock particle size fractions.

TABLE-US-00003 TABLE 3 concrete compositions for comparative example 1 and examples 1a & 1b Raw material Unit C-Ex. 1 Ex. 1a Ex. 1b Cement CEM I 42.5N [kg/m.sup.3] 430 430 430 Water [kg/m.sup.3] 193.5 193.5 193.5 Sand (0/2 mm) [kg/m.sup.3] 525 525 525 Crushed graywacke (5/8 mm) [kg/m.sup.3] 1253 1253 1253 Water-cement value [—] 0.45 0.45 0.45 2,2,4-Trimethylpentyl- [% by — 0.2 — triethoxysilane weight of the cement] Emulsion corresponding to [% by — — 0.5 production example 1 weight of the cement]

TABLE-US-00004 TABLE 4 concrete compositions for comparative example 2 and examples 2a & 2b Raw material Unit C-Ex. 2 Ex. 2a Ex. 2b Cement CEM I 42.5N [kg/m.sup.3] 430 430 430 Water [kg/m.sup.3] 193.5 193.5 193.5 Sand (0/2 mm) [kg/m.sup.3] 525 525 525 Crushed rhyolite (5/8 mm) [kg/m.sup.3] 1211 1211 1211 Water-cement value [—] 0.45 0.45 0.45 2,2,4-Trimethylpentyl- [% by — 0.2 — triethoxysilane weight of the cement] Emulsion corresponding to [% by — — 0.5 production example 1 weight of the cement]

[0142] The production of the concretes was carried out by the following mixing method:

[0143] 1. mixing of the dry components (about 10 seconds)

[0144] 2. addition of water

[0145] 3. addition of the additives (only examples 1a, 1b, 2a & 2b)

[0146] 4. mixing for two minutes

[0147] The following test specimens were produced in steel molds from each concrete and compacted on a shaking table:

[0148] Six prisms (75 mm×75 mm×280 mm) for the 60° C. concrete tests according to test methods A and B with introduction of alkali from the outside.

[0149] Three test specimens having an edge length of 150 mm for testing of the compressive strength and the apparent density.

[0150] After production, the test specimens were left in the mold, covered with a moist cloth and stored at 20±2° C. for 24±1 hours. After removal of the mold, the test specimens were stored for a further time in accordance with the intended test method.

[0151] Test Methods

[0152] Fresh Concrete Testing

[0153] The fresh concrete apparent density in accordance with DIN EN 12350-6 was determined about 10 minutes after mixing.

[0154] The degree of compaction in accordance with DIN EN 12350-4 and the slump flow in accordance with DIN EN 12350-5 were determined about 30 minutes after mixing.

[0155] Set Concrete Testing

[0156] The testing of the compressive strength of the concrete compositions in accordance with DIN EN 12390-3 was carried out after 28 days on three test specimens having an edge length of 150 mm. The set concrete apparent density was determined in accordance with DIN EN 12390-7. The test specimens were stored in accordance with the national appendix to DIN EN 12390-2 (7 days under water, then in a controlled atmosphere chamber at 20±2° C. and 65±5% RH).

[0157] 60° C. Concrete Test with Supply of Alkali from the Outside (ASR Performance Test)

[0158] The resistance of the three concretes to the alkali-silica reaction was examined by means of test method A or test method B with a 60° C. concrete test with supply of alkali from the outside.

[0159] 3 concrete test specimens in each case (prisms having the dimensions 75 mm×75 mm×280 mm) were stored as shown in table 5 in accordance with test method A or test method B. According to test method A, the test specimens are stored in a 3% strength aqueous NaCl solution in step B-2, while in the case of test method B a 10% strength NaCl solution is used here.

[0160] The expansion of the test specimens was measured after 28 days (step A-5) and also after each test cycle (step B-4). The exposure as per step B-1 to B-4 was repeated 14 times for each concrete.

[0161] A concrete suitable for road construction has to have an expansion of less than 0.3 mm/m according to test method A after 10 repetitions of the steps B-1 to B-4 (10 test cycles). In the case of test method B, the expansion must be not more than 0.5 mm/m.

TABLE-US-00005 TABLE 5 Storage conditions during the 60° C. concrete test with supply of alkali from the outside Step Phase No. Duration Storage conditions Preliminary storage A-1 1 day 20 ± 2° C. and covered in the mold A-2 6 days 20 ± 2° C. and ≥95% RH A-3 14 days 20 ± 2° C. and 65 ± 5% RH A-4 6 days 60 ± 2° C. and ≥98% RH A-5 1 day 20 ± 2° C. and ≥98% RH Cyclic treatment at B-1 5 days 60 ± 2° C. in a drying oven 60° C. with an B-2 2 days 20 ± 2° C. in an alkaline alkaline solution solution (repetition until the Test method A: 3% strength desired concrete age NaCl solution has been attained) Test method B: 10% strength NaCl solution B-3 6 days 60 ± 2° C. and ≥98% RH B-4 1 day 20 ± 2° C. and ≥98% RH

[0162] Fresh Concrete Properties

[0163] The properties of the fresh concretes are shown in table 6.

TABLE-US-00006 TABLE 6 fresh concrete properties Degree of Density in compaction in Slump flow in accordance with accordance with accordance with Concrete DIN EN 12350-6 DIN EN 12350-4 DIN EN 12350-5 C-Ex. 1 2410 kg/m.sup.3 1.33 — Ex. 1a 2400 kg/m.sup.3 1.33 — Ex. 1b 2390 kg/m.sup.3 1.33 — C-Ex. 2 2360 kg/m.sup.3 — 41 cm Ex. 2a 2350 kg/m.sup.3 — 39 cm Ex. 2b 2350 kg/m.sup.3 — 39 cm

[0164] Set Concrete Properties

[0165] The compressive strength fc and the apparent density D of the concretes are shown in table 7.

TABLE-US-00007 TABLE 7 compressive strength and density of the concretes Compressive strength Apparent density fc in accordance with D in accordance with DIN EN 12390-3 DIN EN 12390-7 Concrete W 1 W 2 W 3 Av. W 1 W 2 W 3 Av. C-Ex. 1 70.1 67.3 70.2 69.2 2370 2370 2370 2370 Ex. 1a 62.7 63.5 62.1 62.8 2360 2360 2370 2360 Ex. 1b 62.7 60.4 61.9 61.7 2360 2350 2360 2360 C-Ex. 2 73.3 72.1 72.7 72.7 2330 2320 2330 2330 Ex. 2a 63.0 63.6 64.5 63.7 2320 2320 2330 2320 Ex. 2b 63.4 63.6 63.5 63.5 2320 2320 2320 2320 Av. = average; W = test specimen

[0166] 60° C. Concrete Tests with Supply of Alkali from the Outside

[0167] Concretes Containing Crushed Graywacke (Comparative Example 1, Examples 1a & 1b)

[0168] The average expansions of the concrete test specimens of comparative example 1 and of examples 1a & 1b during the 60° C. concrete test according to test method A, i.e. with supply of alkali from the outside by means of a 3% strength NaCl solution, are shown in FIG. 1. In the case of the concrete from comparative example 1, a continuous increase in the expansion up to an average value of 0.53 mm/m was observed after 14 test cycles. After 10 cycles, the expansion was 0.39 mm/m. The concretes from examples 1a & 1b had significantly lower expansion values up to a maximum of ≤0.10 mm/m (0.04 and 0.05 mm/m, respectively, after 10 cycles).

[0169] The average expansions of the concrete test specimens of comparative example 1 and examples 1a & 1b during the 60° C. concrete test according to test method B, i.e. with supply of alkali from the outside by means of a 10% strength NaCl solution, are shown in FIG. 2. The concrete from comparative example 1 had the highest expansion values after 14 test cycles and attained an average value of 2.72 mm/m. After 10 cycles, the expansion was 1.97 mm/m. In the case of the concrete from example 1a, an expansion value of 0.94 mm/m was determined after 10 test cycles and a value of 1.53 mm/m was determined after 14 cycles. In the case of the concrete from example lb, the value after 10 cycles was 0.34 mm/m and after 14 cycles was 0.54 mm/m.

[0170] Concretes Containing Crushed Rhyolite (Comparative Example 2, Examples 2a & 2b)

[0171] The average expansions of the concrete test specimens of comparative example 2 and of examples 2a & 2b during the 60° C. concrete test according to test method A, i.e. with supply of alkali from the outside by means of a 3% strength NaCl solution, are shown in FIG. 3. In the case of the concrete from comparative example 2, a continuous increase in the expansion values to 0.24 mm/m after 10 test cycles and 0.28 mm/m after 14 cycles was found. The expansion values of the concretes from examples 2a & 2b remain close to zero for the entire duration of the test.

[0172] The average expansions of the concrete test specimens of comparative example 2 and of examples 2a & 2b during the 60° C. concrete test according to test method B, i.e. with supply of alkali from the outside by means of a 10% strength NaCl solution, are shown in FIG. 4. In the case of the concrete of comparative example 2, a continuous, virtually linear increase in the expansion over the entire course of the test was found and after 10 test cycles it attained a value of 0.42 mm/m and after 14 cycles a maximum of 0.59 mm/m. The expansion increase for the concrete of example 2a over the course of the first 6 test cycles was significantly lower than for the concrete of comparative example 2. However, a higher expansion increase was then observed, so that an expansion value of 0.29 mm/m was attained after 10 test cycles and a value of 0.52 mm/m was attained after 14 cycles. The expansion of the concrete of example 2b remained close to zero during the course of the entire 14 test cycles.