WO2015055878A1

WO2015055878A1 - High-strength self-compacting concrete and method for the production thereof

Info

Publication number: WO2015055878A1
Application number: PCT/ES2014/070775
Authority: WO
Inventors: Edouard Gonzalez Roubaud; David Perez Osorio; Cristina Prieto Rios; José RODRIGUEZ MONTERO; Lázaro José BAILÓN PÉREZ
Original assignee: Abengoa Solar New Technologies, S.A.
Priority date: 2013-10-14
Filing date: 2014-10-13
Publication date: 2015-04-23
Also published as: ES2535782B1; ES2535782A1

Abstract

The invention relates to the composition of a self-compacting concrete with high compressive strength. Said concrete reaches compressive strength levels of higher than 100 MPa after 28 days, maintaining its self-compacting property. The invention also relates to the method for producing the high-strength self-compacting concrete and to the use of same as structural concrete for structures such as pre-stressed and post-stressed structures, bridges, tunnels, foundations, buildings, nuclear reactors, accumulators, and storage facilities and tanks.

Description

HIGH RESISTANCE SELF-COMFORTABLE CONCRETE AND ITS

OBTAINING PROCEDURE

DESCRIPTION

The present invention relates to the composition of a self-compacting concrete of high compressive strength. This concrete reaches compressive strengths greater than 100 MPa at 28 days while maintaining its self-compacting property. In addition, the present invention relates to the process of obtaining high-strength self-compacting concrete and its use as structural concrete for structures such as prestressed and post-tensioned structures, bridges, tunnels, foundations, buildings, nuclear reactors, accumulators, tanks and tanks. storage. Therefore, the invention could be framed in the field of construction, in architectural and engineering works.

STATE OF THE TECHNIQUE

Currently, there are, on the one hand, high strength concretes such as those described in ES2360003 and ES2076129 that exceed 50 MPa and 80 MPa at 28 days respectively but do not meet the requirements of 50 MPa at 28 days, nor do they have the self compactability feature.

Those described in US20120037045 and US4588443 have compressive strengths of 100 MPa and 128 MPa at 28 days respectively, and that described in WO02083590 that reaches 200 MPa at 28 days of age, however, they still do not have the desired self-compactability characteristic

Finally, there is a patented high strength concrete (GB 0109686.6 patent) and registered under the CARDIFRC ^® brand, which is framed in high performance concrete reinforced with steel fibers, being able to reach compressive strengths of 200 MPa at 28 days, however it does not have self-compacting properties.

On the other hand, there are currently self-compacting concrete, such as the one described in US201 1/0219987, but that do not reach strengths greater than 50 MPa at 28 days, an essential requirement to be called high-strength concrete.

Very few compositions are those that combine properties of high compressive strength and self-compactability:

US20080153942 describes a polymer concrete that combines the properties of self-compactability and compressive strength, and which is characterized by the total removal of Portland cement as a binding or bonding agent, and the total removal of water as a catalyst or hardening agent. This composition represents an alternative to concrete rather than being considered a type of concrete, since it forms a compound that does not contain the usual component materials of a concrete.

And EP0934915 describes a self-compacting calcined bauxite concrete reinforced with steel fibers that reaches up to 200 MPa at 28 days. The use of an unconventional aggregate (calcined bauxite) and steel fibers, raises the cost of supply and manufacture of concrete. It also performs the runoff test on a vibrating table, which is outside the UNE-EN 12350-8 standard that governs said test and, consequently, outside the specifications of the Concrete Instruction for self-compacting concrete. Therefore, it is necessary to develop new concretes that combine the properties of self-compactability and compressive strength and are economically viable. DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a composition of a self-compacting concrete of high compressive strength, greater than 100 MPa at 28 days, and the method of obtaining said composition. It is composed of materials of economic cost for what supposes a very profitable product. Regarding the procedure for obtaining, one of the advantages to highlight is that this procedure is carried out at room temperature, specifically at temperatures between 10 and 35 ° C.

In addition, the present invention relates to the use of this composition as structural concrete structures such as prestressed and post-tensioned structures, bridges, tunnels, foundations, buildings, nuclear reactors, accumulators, tanks and storage tanks.

Therefore, in a first aspect, the present invention relates to a composition of a high strength concrete, greater than 100 MPa at 28 days, and self compacting comprising:

• an aggregate, consisting of washed sand and gravel, in a proportion between 900 to 3000 kg / m ³ ,

• at least one conventional cement in a proportion between 300 to 800 kg / m ³ ,

• water in a proportion between 90 to 200 kg / m3,

• fly ash in a proportion between 40 to 150 kg / m ³ ,

• at least one limestone filler in a proportion between 15 to 80 kg / m ³ ,

• silica fume at a ratio between 40 to 80 kg / m ³ ,

• metacaolin in a proportion between 40 to 80 kg / m ³ ,

• at least one active dispersing agent in a proportion between 10 to 20 kg / m ³ ,

• polypropylene fibers in a proportion between 0.1 to 2 kg / m ³ , In order to obtain a self-compacting concrete of ultra high strength, greater than 100 MPa at 28 days, it is obliged that the composition of the invention contain washed sand, a term known to any person skilled in the art, where the sand has a very low fine content, preferably less than about 15%.

In the present invention, "fine aggregate" means one with a grain size of less than 4 mm and "coarse aggregate" means one with a grain size of less than 1.2 mm.

The presence of a large amount of fines in the aggregate is negative for the manufacture of concrete since it forces us to add a greater amount of water to effect the mixing, the greater the amount of water the less the resistance of the concrete.

So that this washing of the sand does not penalize other properties of the concrete of the invention, other fines of different nature are added to the composition such as limestone filler, metacaolin, fly ash and silica smoke, to replace this fine fraction removed from aggregates. .

In the present invention, the aggregate is preferably a limestone aggregate.

In a preferred embodiment, the aggregate is a combination of washed sand with a granulometry of 0 to 4 mm (0/4 sand) and gravel with a granulometry of 2 to 8 mm (gravel 2/8). More preferably, it is a combination of between 650 and 950 kg / m ³ of washed sand, preferably 0/4 sand and between 850 and 1 100 kg / m ³ of gravel, preferably gravel 2/8. Even more preferably, it is a combination of 788 kg / m ³ of washed sand 0/4 and 928 kg / m ³ of gravel 2/8. By "conventional or common cement" is understood in the present invention as that cement with a low alkali content that has a low chemical vulnerability and a high compressive strength. As an example of conventional cement, mention the CEM I 52.5R / SR cement, which is a high-strength 52.5 MPa Portland Type I cement at 28 days with high initial resistance R and sulfate / SR resistant.

In a preferred embodiment, the conventional cement used in the present invention is a Portland cement, even more preferably a CEM I 52.5R / SR category Portland cement. More preferably the composition of the invention contains between 400 and 600 kg / m ³ of Portland cement CEM I 52.5R / SR. Even more preferably, the composition of the invention contains 500 kg / m ³ of Portland cement CEM I 52.5R / SR. Fly ash comes from the combustion residues of pulverized coal, for example, from thermal power plants producing electricity. In a preferred embodiment, the composition of the invention contains between 75 and 125 kg / m ³ of fly ash. More preferably, the composition of the invention contains 100 kg / m ³ of fly ash.

The limestone filler of the invention has a particle size that complies with article 28.4.1 of instruction EHE-08 and that corresponds to a 90% effective separation in a 0.063 sieve. Preferably, the composition of the invention contains between 20 and 50 kg / m ³ of limestone filler. More preferably, the composition of the invention contains 30 kg / m ³ of limestone filler.

Silica smoke is composed in the present invention of microscopic particles of reactive silica, of approximately 0.1 microns, are spherical particles caused by the reduction of quartz with coal in blast furnaces. Preferably, the composition of the invention contains between 45 and 75 kg / m ³ of silica smoke. More preferably, the composition of the invention contains 55 kg / m ³ of silica smoke. In the present invention, ground metacaolin is used, preferably it is a dehydroxylated aluminosilicate. In a preferred embodiment, the composition of the invention contains between 45 and 75 kg / m ³ of metacaolin. More preferably, the composition of the invention contains 55 kg / m ³ of metacaolin.

In the present invention, "active dispersing agent" is understood as that additive capable of strongly reducing the water content of a given composition without modifying the consistency. Preferably, in the present invention a concrete superplasticizer is used that is capable of giving the fresh concrete a better performance in terms of workability and pumpability. This superplasticizer can be of the type lignosulfonates, naphthalene sulfonates, melamine sulfonates or polycarboxylates. The composition of the present invention preferably contains between 12 and 18 kg / m ³ of superplasticizer and more preferably between 12 and 15 kg / m ³ .

In another preferred embodiment the polypropylene fibers of the composition of the invention are multifilaments of lengths less than 20 mm, more preferably 12 mm. In another preferred embodiment, the composition of the invention contains between 0.2 and 1 kg / m ³ of polypropylene fibers. More preferably, the composition of the invention contains 0.6 kg / m ³ of polypropylene fibers.

In another preferred embodiment, the composition further comprises at least one setting retarder in a proportion less than or equal to 10 kg / m ³ .

In another preferred embodiment, the composition of the invention contains between 2 and 8 kg / m ³ of setting retarder, more preferably it contains 5 kg / m ³ of setting retarder. In a second aspect the present invention relates to a method of obtaining the composition of the invention described above, at temperatures between 10 and 35 ° C comprising the following steps: a) measure the moisture of the aggregate and adjust the amount of water and aggregate with respect to the final composition;

b) add, in the order described, the aggregate and the limestone filler to a kneading device,

c) add 2/3 of the total amount of water in the composition and, optionally, the setting retarder on the mixture obtained in step b),

d) add, in the order described, polypropylene fibers, conventional cement, silica smoke, fly ash and metacaolin over the mixture obtained in step c),

e) knead the mixture obtained in d) for at least 2 minutes,

f) add, in the order described, the remaining third of the total amount of water of the composition and the active dispersing agent on the mixture obtained in step e),

g) knead for at least 10 minutes.

Before proceeding with the preparation of the composition of the invention, for its use as concrete the moisture of the aggregate must be measured previously, that is, the humidity of the washed sand and the gravel that form it, in order to, in case of if necessary, adjust or correct the dosage of the final composition by redosing the sand, gravel and water in the mixture. If these had moisture, the excess of it must be deducted from the total amount of water necessary to obtain the composition and, in turn, replace it with more washed sand and gravel in the same amount, until the amount of water is obtained, Washed sand and gravel mentioned corresponding to the final composition.

The humidity of the aggregate is corrected by determining its moisture content, for example by burning aggregates or scales hygrometric of a previous sample. Subsequently, the dosage of the amount of water, sand and gravel is adjusted or readjusted. This adjustment or readjustment of the dosage consists in deducting from the dosage water added in steps (c) and (f), the amount measured in determining the degree of moisture in the aggregate. That same amount, by weight, will be added to the corresponding aggregate that is added in step (b).

The order in which the steps of the process are carried out is essential for the composition of the invention to exhibit the properties that characterize it.

Preferably, the kneading device of step b) is selected from the list comprising a planetary mixer with vertical axis or concrete mixer, concrete mixer truck or concrete plant.

A third aspect of the invention relates to the use of the composition described above as structural concrete due to its high strength and self-compacting properties. Preferably, the concrete of the invention is used as structural concrete in prestressed and post-tensioned structures, bridges, tunnels, foundations, buildings, nuclear reactors, accumulators, warehouses and storage tanks. In another preferred embodiment, the composition of the invention is used as the structural concrete of a storage tank of a pressurized fluid.

The last aspect of the invention relates to a thermal storage tank of a pressurized fluid, either liquid or gas, comprising an external layer of post-tensioned concrete and an internal layer of refractory concrete with a characteristic resistance greater than 10 MPa acting as a thermal barrier between the fluid and the post-tensioned concrete, characterized in that the external layer of post-tensioned concrete is manufactured with the high-strength and self-compacting concrete composition described above.

Throughout the description and the claims the word "comprises" and its variants are not intended to exclude other technical characteristics, additives, components or steps. For those skilled in the art, other objects, advantages and features of the invention will be derived partly from the description and partly from the practice of the invention. The following examples and figures are provided by way of illustration, and are not intended to be limiting of the present invention.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1: Vertical section and side view of the accumulator tank of example 2.

Figure 2: 90 ° cross section made to the accumulator tank of example 2.

EXAMPLES

The invention will now be illustrated by tests carried out by the inventors, which shows the self-compactability and compressive strength of more than 100 MPa at a 28-day age of the concrete of the invention.

Example 1: Composition and method of obtaining a self-compacting concrete with a compressive strength greater than 100 MPa at an age of 28 days. A concrete was prepared whose composition is that indicated in Table 1 according to the procedure for obtaining detailed below.

Table 1 . Example of concrete composition of the invention.

Before carrying out the preparation of the concrete, the humidity of the limestone aggregates that form it was measured, checking that they were exempt from it.

In a vertical axis planetary kneader and under constant and uninterrupted mixing, the quantities of the ingredients mentioned in Table 1 were added in the following order: Firstly a fraction of grain grain size 0/4, gravel size were added 2/8 grain and limestone filler in the mixer.

Then 2/3 of the total water that forms concrete and setting retarder was added. Subsequently, 12 mm long polypropylene fibers, Portland cement, silica smoke, fly ash and metacaolin were added in order, allowing the ingredients to mix for 2 minutes before adding the rest of the water, 1/3 of the water. Total forming concrete and superplastic.

Finally, concrete kneading was carried out for at least 10 minutes. Next, fresh concrete was characterized according to the instruction of structural concrete EHE 08 by performing the following tests (according to LINEEN 12390-2 and UNE-EN 12390-3):

• Runoff test, according to UNE-EN 12350-8

· V funnel test, according to UNE-EN 12350-9

• L-box method, according to UNE-EN 12350-10

• Test with the Japanese ring, according to UNE-EN 12350-12

• Segregation resistance test, according to ASTM C 161 1 These tests allow verifying and certifying whether the concrete is self-compacting, in addition to checking the homogeneity of the concrete from segregation.

The results that are compiled in Table 2 correspond to the tests of self-compactability, evaluating in turn the time during which the mixture can be considered self-compacting.

Table 2: Shows the results of the runoff, V-funnel, L-box and J-ring tests and the results of compressive strength at the ages of 7 and 28 days performed for the concrete example of the invention with different proportions of additives superplasticizer and setting retarder.

Self-compactability is considered when ensuring compliance with the parameters set out in Table 3:

Table 3: Permissible ranges to consider the self-compactability of a concrete according to runoff tests, V funnel, L-box and J ring.

As for the characterization in the hardened state, the compressive strengths have been determined, mainly at the ages of 7 and 28 days. The results are shown in Table 4, those kneaded that meet the requirements of Table 3 as well as compressive strengths greater than 100 MPa being acceptable. The kneaded ones are listed from 1 to 19 because they were prepared on different days; a humidity adjustment was made every day.

Table 4: Shows the results of the runoff and J-ring tests and the results of compressive strength at the ages of 7 and 28 days performed for the concrete example of the invention.

Am. 4 3.50 680 645 93.85 1 1 1, 15

Am. 5 3.28 660 650 90.30 108.95

Am. 6 4.90 645 700 79.95 101, 70

Am. 7 4.50 655 605 95.00 1 12.75

Am. 8 3.97 665 650 93.25 1 12.60

Am. 9 3.62 650 620 89.45 106.45

Am. 10 2.34 625 670 87.40 108.45

Am. 1 1 3.70 670 660 84.90 107.25

Am. 12 3.47 650 630 88.30 108.00

Am. 13 4.03 630 625 84.90 103.30

Am. 14 2.38 655 670 84, 10 103.55

Am. 15 2.85 625 665 91.00 105.65

Am. 16 4, 16 680 675 88.55 105.90

Am. 17 3.72 650 605 91, 20 104.70

Am. 18 3.94 635 615 99.95 1 19.80

Am. 19 4, 16 625 605 97, 15 107.45

Example 2: Use of the composition of the invention as structural concrete of a thermal storage tank of a pressurized fluid.

The composition of the invention of the previous example can be used as structural concrete for the manufacture of a thermal storage tank, and as a preferred embodiment example for a tank such as that described in the Spanish patent application with application number P201200796, dated of application 6 August 2012, is a cylindrical steam accumulator tank that is formed by two layers, an outer layer of post-tensioned concrete and an inner layer of refractory concrete.

Figure 1 shows the vertical section of a steam accumulator comprising the concrete composition of the invention. In it you can see the double layer formed by the cylindrical body of post-tensioned concrete composed of the composition of the invention (1) in its outer part and the cylindrical body of a refractory concrete (2) in its inner face. This cylindrical shape has two semi-ellipsoids at its ends, the semi-ellipsoidal body of post-tensioned concrete composed of the composition of the invention, in particular the composition of the previous example, (3) and the semi-ellipsoidal body of a refractory concrete (4), so that it allows a better distribution of the tensions generated by the pressure and the temperature inside the accumulator as well as minimizing the loss of useful volume with respect to the spherical cap.

Figure 2 shows the 90 ° cross-section made to the concrete accumulator where the post-tensioned concrete base composed of the composition of the invention, in particular the composition of the previous example (5), can be seen.

The use of the post-tensioned concrete of the invention with high compression resistance allows to achieve the necessary vacuum compression state, that is, without pressure or temperature taking into account that the forces acting on the inner wall produce expansions and tractions in the layer internal composed of a refractory concrete.

Claims

1 . - A composition that includes

• an aggregate, consisting of washed sand and gravel, in a proportion of between 900 to 3000 kg/m ³ ,

• at least one conventional cement in a proportion of between 300 to 800 kg/m ³ ,

• water in a proportion of between 90 to 200 kg/m ³ ,

• fly ash in a proportion of between 40 to 150 kg/m ³ ,

• at least one limestone filler in a proportion of between 15 to 80 kg/m ³ ,

• silica fume in a proportion of between 40 to 80 kg/m ³ ,

• metakaolin in a proportion of between 40 to 80 kg/m ³ ,

• at least one active water-reducing dispersing agent in a proportion of between 10 to 20 kg/m ³ ,

• polypropylene fibers in a proportion of between 0.1 to 2 kg/m ³ ,

2. - The composition, according to claim 1, where the aggregate is limestone in nature.

3. - The composition, according to claim 2, wherein the limestone aggregate is a combination of sand with a grain size of 0 to 4 mm and gravel with a grain size of 2 to 8 mm.

4. - The composition according to claim 3, where the proportion of sand 0/4 used is between 650 and 950 kg/m ³ and the proportion of gravel 2/8 used is between 850 and 1 100 kg/m ³ .

5. - The composition according to claim 4, where the proportion of 0/4 sand used is 788 kg/m ³ and the proportion of 2/8 gravel used is 928 kg/m ³ .

6. - The composition, according to any of claims 1 to 5, where the conventional cement used is a Portland cement of CEM I 52.5R/SR category.

7. - The composition, according to claim 6, where the proportion of the Portland cement CEM I 52.5R/SR used is between 400 to 600 kg/m ³

8. - The composition, according to claim 7, where the proportion of Portland cement CEM I 52.5R/SR used is 500 kg/m ³

9. - The composition according to any of claims 1 to 8, where the proportion of fly ash used is between 75 and 125 kg/m ³ .

10. - The composition according to claim 9, where the proportion of fly ash used is 100 kg/m ³ .

1 1 - The composition, according to any of claims 1 to 10, where the proportion of the limestone filler used is between 20 and 50 kg/m ³ .

12. - The composition according to claim 9, where the proportion of limestone filler used is 30 kg/m ³ .

13. - The composition according to any of claims 1 to 12, wherein the silica fume is formed by 0.1 micron particles of reactive silicon dioxide.

14. The composition according to claim 13, wherein the proportion of the silica fume used is between 45 and 75 kg/m ³ .

15. - The composition according to claim 14, where the proportion of the silica fume used is 55 kg/m ³ .

16. - The composition according to any of claims 1 to 15, where the proportion of metakaolin used is between 45 and 75 kg/m ³

17. - The composition according to claim 16, where the proportion of metakaolin used is 55 kg/m ³ .

18. - The composition according to any of claims 1 to 17, wherein the active water-reducing dispersing agent is a concrete superplasticizer.

19. - The composition according to claim 18, where the proportion of the concrete superplasticizer used is between 12 and 18 kg/m ³ .

20. - The composition according to claim 19, where the proportion of the concrete superplasticizer used is between 12 and 15 kg/m ³ .

twenty-one . - The composition, according to any of claims 1 to 20, where the polypropylene fibers are multifilaments of lengths less than 20 mm.

22.- The composition according to claim 21, where the polypropylene fibers are multifilaments with a length of 12 mm.

23. - The composition according to any of claims 21 or 22, where the proportion of polypropylene fibers used is between 0.2 and 1 kg/m ³ .

24. - The composition according to claim 23, where the proportion of polypropylene fibers is between 0.6 kg/m ³ .

25. - The composition, according to any of claims 1 to 24, which also comprises at least one setting retarder in a proportion less than or equal to 10 kg/m ³ ..

26. - The composition according to claim 25, where the proportion of the setting retarder used is between 2 and 8 kg/m ³

27. - The composition according to claim 26, where the proportion of the setting retarder used is 5 kg/m ³ .

28. - Procedure for obtaining the composition, according to claims 1 to 27, carried out at temperatures between 10 and 35 °C, which includes the following stages: a) measuring the humidity of the aggregate and adjusting the amount of water and arid with respect to the final composition;

c) add 2/3 of the total amount of water of the composition and, optionally, the setting retarder to the mixture obtained in step b),

d) add, in the order described, polypropylene fibers, conventional cement, silica fume, fly ash and metakaolin to the mixture obtained in step c),

e) knead the mixture obtained in d) for at least 2 minutes, f) add, in the order described, the remaining third of the total amount of water in the composition and the active dispersing agent to the mixture obtained in step e) ,

g) knead for at least 10 minutes.

29. - The procedure according to claim 28, wherein the mixing device of step b) is selected from the list that includes a vertical axis planetary mixer, concrete mixer truck or concrete plant.

30. - Use of the composition, according to any of claims 1 to 27, as structural concrete.

31. - Use of the composition, according to claim 30, as structural concrete in prestressed and post-tensioned structures, bridges, tunnels, foundations, buildings, nuclear reactors, accumulators, warehouses and storage tanks.

32. - Use of the composition, according to any of claims 30 or 31, as structural concrete for a thermal storage tank for a pressurized fluid.

33. Thermal storage tank for a pressurized fluid, whether liquid or gas, comprising an external layer of post-tensioned concrete and an internal layer of refractory concrete with a characteristic resistance greater than 10 MPa that acts as a thermal barrier between the fluid and the post-tensioned concrete, characterized in that the external layer is composed of the composition described according to any of claims 1 to 27.