Concrete composition

Abstract

A concrete composition having, in a mixture with water, a hydraulic binder, sand, aggregates, an expanding agent and a shrinkage reducing admixture, wherein the expanding agent is calcium oxide having a low reactivity such that the concrete casted using the composition does not expand by more than 0.05 vol. % during the first 10 days, preferably not expanding more than 0.05 vol. % during the first 7 days, after having been cast.

Claims

1. A concrete composition that is (a) a concrete composition comprising, in a mixture with water, a hydraulic binder, sand, aggregates, an expanding agent, and a shrinkage reducing admixture, wherein the expanding agent is calcium oxide having a low reactivity wherein the concrete does not expand by more than 0.05 vol. %, during the first 10 days, after having been casted; or (b) a concrete composition comprising, in a mixture with water, a hydraulic binder, sand, aggregates, an expanding agent, and a shrinkage reducing admixture, wherein the expanding agent is calcium oxide having a low reactivity wherein the concrete does not expand by more than 0.05 vol. %, during the first 7 days, after having been casted, wherein the concrete composition of (a) and the concrete composition of (b) satisfy at least one of the following: (i) the calcium oxide has a reactivity that is characterized by a conductivity of <11 mS/cm when dissolved in water, (ii) the calcium oxide has a reactivity that is characterized by an average temperature increase of <0.5 C./min during the first 15 minutes after the addition of the calcium oxide into water, or (iii) the calcium oxide has a reactivity that is characterized by a temperature increase of <10 C. during the first 5 minutes after the addition of the calcium oxide into water.

2. The concrete composition according to claim 1, wherein the calcium oxide has a particle size distribution characterized by a residue of at least 6 wt. % on a 45 m mesh sieve.

3. The concrete composition according to claim 1, wherein the hydraulic binder comprises ordinary Portland cement and optionally supplementary cementitious material.

4. The concrete composition according to claim 1, wherein the shrinkage reducing admixture is an organic admixture.

5. The concrete composition according to claim 1, wherein the mixture further comprises a water reducing agent in an amount of 20-60 ml/100 kg hydraulic binder.

6. The concrete composition according to claim 1, wherein the volume change of the concrete is between +0.01 and 0.01 vol. % after 365 days after having been casted.

7. The concrete composition according to claim 1, wherein the concrete composition contains the expanding agent in an amount of 2-6 wt. % of the hydraulic binder.

8. The concrete composition according to claim 1, wherein the concrete composition contains the shrinkage reducing admixture in an amount of 1-2 wt. % of the hydraulic binder.

9. The concrete composition according to claim 1, wherein the concrete composition has a water/binder ratio is 0.15-0.50.

10. The concrete composition according to claim 1, wherein the hydraulic binder is present in an amount of 280-700 kg per cubic meter of concrete.

11. A construction element comprising concrete obtained from a concrete composition according to claim 1.

12. The concrete composition according to claim 1, wherein when the concrete composition is (a), the expanding agent is calcium oxide having a low reactivity, and wherein the concrete does not expand by more than 0.03 vol. % during the first 10 days; or when the concrete composition is (b), the expanding agent is calcium oxide having a low reactivity, and wherein the concrete does not expand by more than 0.03 vol. % during the first 7 days.

13. The concrete composition according to claim 3, wherein the optionally supplementary cementitious material comprises granulated blast furnace slag, fly ash, pozzolans or mixtures thereof.

14. The concrete composition according to claim 5, wherein the water reducing agent comprises a polycarbonate ether based plasticizer admixture or a polynaphthalene sulfonate based plasticizing admixture.

15. The concrete composition according to claim 4, wherein the shrinkage reducing admixture is an organic admixture based on polypropylene glycol, polyethylene glycol and/or a glycol ether derivative, optionally in a liquid mixture with surfactants.

16. The concrete composition according to claim 1, wherein the concrete composition of (a) satisfies (i), (ii) and (iii).

17. The concrete composition according to claim 1, wherein the concrete composition of (b) satisfies (i), (ii) and (iii).

Description

EXAMPLE 1

(1) Concrete was mixed in four different mix designs. In order to determine, which type of calcium oxide is suitable for use in the mix designs, the following tests have been performed.

(2) Two different types of calcium oxide were tested with regard to their dissolution rate. To this aim, the conductivity of two dispersions of diluted calcium oxide was tested. The following test procedure was followed: A glass beaker is filled with 45 mL water at a temperature of 20 C., A stirrer was used at a stirring velocity of 450 rpm, Conductivity was initially measured, 1.5 g of calcium oxide was quickly added with a small spoon, Conductivity was measured as a function of time until it stabilizes.

(3) The results of the test are shown in FIG. 1. As can be gathered from FIG. 1 the conductivity values in both cases are always below 11 mS/cm, which make both sources suitable for the inventive use.

(4) In another test, calcium oxides of four other sources were tested with regard to their heat of hydration. The following test procedure was used: A glass beaker is filled with 200 mL water at a temperature of 20 C., A stirrer was used at a stirring velocity of 450 rpm, Conductivity was initially measured, 1.5 g of calcium oxide was quickly added with a small spoon, Conductivity was measured as a function of time until it stabilizes.

(5) As shown in FIG. 2, the sources of calcium oxide have two distinct behaviors. In the first series, the heat of hydration is high and causes a temperature increase of the dispersion of more than 15 C. in less than 5 minutes. The product Tradical SR from Rheinkalk has a lower heat of hydration, characterized by a maximum temperature increase of +12 C., and the average temperature increase is less than +0.5 C. per minute between 1 and 15 minutes. This latter source of calcium oxide is a preferred expanding agent within the scope of the invention.

(6) Subsequently, concrete was mixed in four different mix designs according to Table 1.

(7) TABLE-US-00001 TABLE 1 Water reducer Binder Slag Aggregate Combination SRA CaO mL/100 kg Mix # kg/m.sup.3 w/B wt-% Sand, % GR-20, % Lim-40, % wt-% wt-% binder 1 350 0.47 25 48 32 20 1.5 5.0 60 2 350 0.47 25 48 32 20 2.0 3.0 25 3 350 0.47 25 48 32 20 1.0 3.0 35 4 350 0.47 25 48 32 20 0.0 5.0 104

(8) In Table 1, w/B means water/binder ratio, SRA means shrinkage reducing admixture, GR-20 means 20 mm natural gravel and Lim-40 means 40 mm crushed limestone gravel. The amounts given in the column Binder represent the total amount of hydraulic binder, including Portland cement and granulated blast furnace slag. The slag content of the binder is indicated in the column Slag.

(9) As a water reducer the product Plastol 341 produced by The Euclid Chemical Company is used. Plastol 341 is a polycarboxylate based plasticizing admixture.

(10) SRA Floor supplied by Euclid Chemicals was used as shrinkage reducing agent.

(11) Any of the calcium oxides that have been identified as suitable in the conductivity test and/or the heat of hydration test as described above may be used in the example.

(12) The concrete compositions with the mix designs described in Table 1 were used to produce test blocks, which were cured and several parameters were measured as indicated in Table 2.

(13) TABLE-US-00002 TABLE 2 Plastic Performance Compressive Air Strength Mix Ambient Concrete Slump Content Density 7 d 28 d # C. C. mm % kg/m.sup.3 MPa 1 21.9 22.9 120 2.6 2417 33.0 43.8 2 21.9 23.6 130 4.0 2368 34.0 45.1 3 21.4 22.8 125 2.5 2405 36.0 48.2 4 21.5 23.1 115 2.4 2444 39.6 51.2

(14) Further, the volumetric change of the cured concrete was measured, as indicated in Table 3.

(15) TABLE-US-00003 TABLE 3 Concrete Shrinkage/Expansion (%, ASTM C 878/878M-09) Cured in water Cured in drying chamber Mix # 1 d 4 d 7 d 1 d 4 d 7 d 14 d 21 d 28 d 56 d 91 d 126 d 1 0.030 0.035 0.035 0.031 0.029 0.027 0.025 0.022 0.021 0.014 0.014 0.010 2 0.022 0.027 0.025 0.025 0.023 0.021 0.018 0.018 0.017 0.010 0.008 0.006 3 0.024 0.029 0.030 0.028 0.025 0.023 0.021 0.021 0.018 0.012 0.006 0.005 4 0.050 0.053 0.055 0.049 0.045 0.041 0.036 0.035 0.030 0.021 0.021 0.014

(16) Graphs of the volumetric change data are represented in FIG. 3. As can be seen from Table 3 and FIG. 3, the final volumetric change after 126 days is 0.01 vol.-% or below for mix designs Nos. 1, 2 and 3, in which a shrinkage reducing agent as well as a calcium oxide having a low reactivity have been used. In mix design No. 4 no shrinkage reducing agent was used at all. This evidences the synergistic effects of the combined use of the shrinkage reducing agent and the calcium oxide having a low reactivity.

EXAMPLE 2

(17) In a further example, ultra-performance concrete was mixed in two different mix designs according to Table 4. Mix #2 is a mix design according to the invention, whereas mix #1 is a conventional mix design without the use of CaO and without shrinkage reducing agent.

(18) TABLE-US-00004 TABLE 4 Binder W/B Water reducer Steel fibers CaO SRA Mix # kg/m.sup.3 wt-% kg/m.sup.3 wt-% wt-% 1 700 0.15 3.4 303 0 0 2 700 0.15 3.4 303 3.0 1.0

(19) In Table 4, W/B means water/binder ratio and SRA means shrinkage reducing admixture.

(20) As a water reducer the product Sika Viscocrete P5 produced by Sika is used.

(21) The steel fibers are Dramix OL 13/0.20.

(22) SRA Floor supplied by Euclid Chemicals was used as shrinkage reducing agent. Any other convention shrinkage reducing agent may also be used.

(23) Any of the calcium oxides that have been identified as suitable in the conductivity test and/or the heat of hydration test as described in Example 1 may be used in this example.

(24) The concrete compositions with the mix designs described in Table 4 were used to produce test blocks, which were cured and several parameters were measured as indicated in Table 5.

(25) TABLE-US-00005 TABLE 5 Plastic Performance Flow at Compressive strength Flow 30 min Air Density 1 d 7 d 28 d 56 d Mix # mm mm Vol.-% kg/m.sup.3 MPa 1 53 42 2.1 2400 11.7 31.3 37.1 40.4 2 46 41 1.6 2441 12.7 31.6 38 435

(26) As can be seen in the shrinkage values represented in FIG. 4, the mix design #2 according to the invention features a considerable lower shrinkage than mix design #1.