ES2895755B2 - SUSTAINABLE DRY CONSISTENCY CONCRETE AND ITS PRODUCTION PROCEDURE - Google Patents

Description

DESCRIPTION

SUSTAINABLE CONCRETE OF DRY CONSISTENCY AND ITS PROCEDURE

ELABORATION

TECHNICAL FIELD OF THE INVENTION

The present invention is encompassed in the field of construction materials, specifically concrete with a dry consistency, also called dry concrete, and with recovered components, from other processes or substances, such as waste from the concrete prefabrication industry. , making them sustainable.

BACKGROUND OF THE INVENTION

Roller-compacted dry concrete is a concrete that has a very low workability in its fresh state, so that the only way it can be put on site is through the use of compacting rollers, such as those commonly used on roads for paving roads. base and subbase layers. This reduced workability means that it presents very high initial strengths and is capable of supporting loads immediately after compaction, not being necessary to wait for a setting time, as is the case with other concretes such as vibrated concrete or self-compacting concrete. This reduced workability means that the consumption of energy and fuel during its installation is very high, making it a very useful material, but traditionally very aggressive with the environment.

Recycled concrete aggregate is a traditional waste from the prefabrication industry of concrete elements. Many precast concrete elements, after their manufacture, are rejected due to aesthetic or geometric defects. In addition, during the elaboration of these elements there is leftover concrete that is not used later. The crushing and grinding of these elements and the leftover concrete once hardened allows obtaining an artificial aggregate with a continuous granulometry from 0.1 to 30 mm that can be used as a substitute for limestone or siliceous natural aggregate. The recycled concrete aggregate is fundamentally characterized by having a lower density than the natural aggregate, and its much higher water absorption. This greater absorption of water can be favorable for the production of dry, roller-compacted concrete, since it allows the workability of the concrete to be reduced more quickly, thus achieving a more rapid acquisition of strength, an aspect of great interest in this type of concrete.

Ground granulated steel slag, from the steel industry, is produced during the steelmaking process. Ground granulated iron and steel slag is obtained by immersing the blast furnace slag in water so that it is abruptly cooled, followed by a grinding process. The ground granulated iron and steel slag is characterized by having a micrometric size, and conglomerating properties, that is, it is capable of hardening and acquiring resistance when mixed with water. In accordance with all this, it is a product of great value, since it can be used as a substitute for cement clinker, thus contributing to the reduction of CO ² emissions into the atmosphere (on average, for each ton of clinker produced 0.9 tons of CO ² are emitted into the atmosphere).

White ladle furnace slag is a residue generated during the steel refining process (secondary metallurgy), which is carried out in an electric ladle furnace. It is a powdery residue. White ladle furnace slag not only has conglomerating properties, but also has expansive characteristics (lime and free magnesia), so that, in the presence of water, heat and with the passage of time, its volume can increase considerably. These expansive characteristics make it very useful for reducing concrete shrinkage and the cracking associated with this phenomenon, which is one of the main aspects that must be avoided both in pavements (to guarantee comfortable and safe driving) and in dams (to avoid possible water leakage and collapse of the entire structure), fields of application of dry roller-compacted concrete.

Concrete made from fibers has been developed mainly in recent years. Its use is fundamentally linked to the cracking of concrete, since that its addition causes a sewing effect of the fissures, which reduces this phenomenon. In addition, they allow shrinkage to be reduced, since they act as rigid elements inside the concrete mass, increasing its dimensional stability. Both metal fibers, steel fibers, and synthetic fibers, generally plastic, such as polyethylene or polypropylene, are valid. The use of fibers in the concrete reduces its workability, which makes it difficult to obtain a dry roller-compacted concrete that is workable enough for optimal placement (the workability of dry roller-compacted concrete must be low, but not null, since otherwise its implementation is not possible).

The existing state of the art describes the composition and procedure for preparing roller-compacted dry concrete with natural aggregate in all fractions (ACI-309.5R-06, 2006. Compaction of Roller-Compacted Concrete ; ACI-327R-14, 2014 Guide to Roller-Compacted Concrete Pavements). The requirements that roller-compacted dry concrete must meet are included, among others, in the Spanish Instruction on Structural Concrete EHE-08 (EHE-08, 2010. Instruction on Structural Concrete EHE-08. Ministry of Development, Government of Spain ).

The most similar concretes to those proposed in this invention are vibrated concretes made with recycled concrete aggregate and fibers that used ordinary Portland cement as a binder (Ak?a, KR, Qakir, O., Ipek, M., 2015. Properties of polypropylene fiber reinforced concrete using recycled aggregates. Constr. Build. Mater. 98, 620-630. DOI: 10.1016/j.conbuildmat.2015.08.133; N. Kachouh, H. El-Hassan, T. El-Maaddawy 2019. Effect of steel fibers on the performance of concrete made with recycled concrete aggregates and dune sand. Constr. Build. Mater. 213, 348-359. DOI: 10.1016/j.conbuildmat.2019.04.087). Therefore, neither ground granulated iron and steel slag nor white ladle furnace slag were used in these.

In relation to roller compacted dry concrete made with recycled concrete aggregate, there are only three studies that address this material (Fardin, HE, dos Santos, AG, 2020. Roller compacted concrete with recycled concrete aggregate for paving bases. Sustainability. 12(8), 3154. DOI: 10.3390/SU12083154; Lopez-Uceda, A., Agrela, F., Cabrera, M., Ayuso, J., López, M., 2018. Mechanical performance of roller compacted concrete with recycled concrete aggregates. Road Materials and Pavement Design. 19(1), 36-55. DOI: 10.1080/14680629.2016.1232659; Lopez-Uceda, A., Ayuso, J., Jiménez, JR, Galvín, AP, Del Rey, I., 2020. Feasibility study of roller compacted concrete with recycled aggregates as base layer for light-traffic roads. Road Materials and Pavement Design.

21(1), 276-288. DOI: 10.1080/14680629.2018.1483257). These studies address only the use of recycled concrete aggregate only in the coarse fraction. There is no study in which all the coarse, medium and fine fractions are recycled concrete aggregate.

The field of application of ground granulated iron and steel slag has traditionally been soil stabilization (Du, YJ, Wu, J., Bo, YL, Jiang, NJ, 2020. Effects of acid rain on physical, mechanical and chemical properties of GGBS -MgO-solidified/stabilized Pb-contaminated clayey soil.Acta Geotechnica.15 (4), 923 932. DOI: 10.1007/s11440-019-00793-y;Wu, HL, Jin, F., Bo, YL, Du, YJ, Zheng, JX, 2018. Leaching and microstructural properties of lead contaminated kaolin stabilized by GGBS-MgO in semi-dynamic leaching tests. Constr. Build. Mater. 172, 626-634. DOI: 10.1016/j.conbuildmat.2018.03. 164) or the elaboration of embankment road bases and sub-bases (Abdollahnejad, Z., Luukkonen, T., Mastali, M., Giosue, C., Favoni, O., Ruello, ML, Kinnunen, P., Illikainen, M., 2020. Microstructural Analysis and Strength Development of One-Part Alkali-Activated Slag/Ceramic Binders Under Different Curing Regimes. Waste and Biomass Valoris. 11 (6), 3081 3096. DOI: 10.1007/s12649-019-0062 6-9). This residue has not traditionally been used for the production of concrete (Bondar, D., Basheer, M., Nanukuttan, S., 2019. Suitability of alkali activated slag/fly ash ( AA-GGBS/FA) concretes for chloride environments: Characterization based on mix design and compliance testing Constr Build Mater 216, 612-621 DOI: 10.1016/j.conbuildmat.

2019.05.043; Yang, KH, Hwang, YH, Lee, Y., Mun, JH, 2019. Feasibility test and evaluation models to develop sustainable insulation concrete using foam and bottom ash aggregates . build Build. Mother. 225, 620-632. DOI: 10.1016/j.conbuildmat.2019.07.130), and its use for the manufacture of dry roller-compacted concrete is even rarer (Aghaeipour, A., Madhkhan, M., 2017. Effect of ground granulated blast furnace slag ( GGBFS) on RCCP durability. build Build. Mother. 141, 533-541. DOI: 10.1016/j.conbuildmat.2017.03.019). There is no study in which dry roller-compacted concrete has been produced by simultaneously using recycled concrete aggregate and ground granulated iron and steel slag.

White slag has been used in a few studies for the development of self-compacting concrete (Sideris, KK, Tassos, C., Chatzopoulos, A., Manita, P., 2018. Mechanical characteristics and durability of self-compacting concretes produced with ladle furnace slag. Constr. Build. Mater. 170, 660-667. DOI: 10.1016/j.conbuildmat.2018.03.091), whose field of application is completely different from that of dry roller-compacted concrete. It is noteworthy, therefore, that there is no study in scientific databases in which this slag has been used for the production of roller-compacted concrete, regardless of the type of aggregate used.

Finally, there are studies that evaluate the behavior of roller-compacted dry concrete made with limestone or siliceous natural aggregate in all fractions and metallic or synthetic fibers (Rooholamini, H., Hassani, A., Aliha, MRM, 2018. Evaluating the Effect of macro-synthetic fiber on the mechanical properties of roller-compacted concrete pavement using response surface methodology. Constr. Build. Mater. 159, 517-529. DOI: 10.1016/j.conbuildmat.2017.11.002; Sukontasukkul, P., Chaisakulkiet, U., Jamsawang, P., Horpibulsuk, S., Jaturapitakkul, C., Chindaprasirt, P., 2019. Case investigation on application of steel fibers in roller compacted concrete pavement in Thailand. Case Stud. Constr. Mater. 11 , e00271. DOI: 10.1016/j.cscm.2019.e00271). There is no study in which the use of recycled concrete aggregate and fibers is combined for the production of dry roller-compacted concrete. All of the above leads to the conclusion that there is no study in which the following four elements are combined for the production of roller-compacted dry concrete: recycled concrete aggregate, ground granulated iron and steel slag, white ladle furnace slag and fibers. metallic and/or synthetic.

DESCRIPTION OF THE INVENTION

The present invention is set forth and characterized in the independent claims, while the dependent claims describe other features thereof.

The object of the invention is a sustainable concrete with a dry consistency and its production process. The technical problem to be solved is to constitute the components of the concrete and establish the stages of elaboration in such a way as to obtain a valid concrete for use in structural elements according to the applicable regulations, with high resistance and low shrinkage and cracking.

In view of the foregoing, the present invention refers to a sustainable concrete with a dry consistency that comprises Portland cement as the first binder, aggregates, water and additives, as is known in the state of the art. Concrete is characterized by that which comprises metallic and/or plastic fibres, ground granulated iron and steel slag as the second binder and white ladle furnace slag as the third binder. The aggregates comprise recycled concrete aggregate, with the entire coarse fraction being the entire the middle fraction and the total fine fraction of the concrete of said recycled concrete aggregate. That is, the entire coarse fraction, the medium fraction and the fine fraction is recycled concrete aggregate, there are no coarse, medium or fine fractions of other types of aggregate, that is, no natural aggregate is incorporated, either siliceous or limestone, to the coarse, medium or fine fractions of aggregate.

One advantage of concrete is that it maximizes the sustainability of a product that is traditionally very harmful to the environment. The dry concrete compacted with a roller with which pavements and dams are manufactured, among other elements, requires a very energetic vibration, by means of the traditional “rollers”, which supposes a great consumption of energy and fuel. The characteristics that this concrete must present mean that this workability cannot be modified, but it is possible to increase sustainability from the point of view of its composition by adding by-products to the mixture, such as recycled concrete aggregate, ground granulated iron and steel slag and white ladle furnace slag. Thus, it contributes to the reduction of climate change, while favoring a more circular economy, with the consequent reduction of the carbon footprint and preservation of the natural environment thanks to the reduction in waste dumping, clinker consumption and CO ² emissions. This last aspect is associated with the decrease in the production of cement clinker as it is replaced by alternative binders (ground granulated iron and steel slag and white ladle furnace slag).

Another advantage of concrete is its high initial strength as soon as it is compacted, without the need for setting. Its long-term resistance (the normalized value is established at 28 days) is very high, so that it would be valid for all construction and civil engineering applications where the use of this type of concrete is common.

Another advantage of concrete is that the shrinkage (shortening) of the concrete and the cracking associated with this phenomenon are minimized thanks to the white ladle furnace slag (with expansive characteristics) and the fibers. Applications where dry roller compacted concrete is useful require minimal cracking.

Another advantage of concrete derived from the aforementioned resistance is that it is suitable for applications in the field of infrastructure, such as pavements, and in the field of large structures, for the construction of dams of any kind, whether gravity, vault or arch

Likewise, the invention refers to a process for the production of sustainable concrete with a dry consistency as stated above, which comprises the following stages in sequence:

-addition of 90% by volume of the water and all the aggregates, including recycled concrete aggregate, and binders, with Portland cement being a first binder, ground granulated iron and steel slag a second binder, and white ladle furnace slag a third conglomerate;

- first mixed;

- first rest;

- second mixed

- addition of 10% by volume of water and additives;

- third mixed;

- second rest.

DETAILED DISCLOSURE OF THE INVENTION

The invention is a sustainable dry-consistency concrete comprising Portland cement as the first binder, aggregates, water and additives, metal and/or plastic fibers, ground granulated iron and steel slag as the second binder and white ladle furnace slag as the third binder, the aggregates they comprise recycled concrete aggregate, being the entire coarse fraction, the entire medium fraction and the entire fine fraction of the concrete of said recycled concrete aggregate.

Optionally, it comprises a powder fraction of a mixture of limestone and siliceous sand.

A dosage that is shown to be advantageous is that Portland cement as the first binder is between 40% and 55% by volume of the total binders, ground granulated iron and steel slag as the second binder is between 35% and 45% by volume. Of the total binders, white ladle furnace slag as the third binder is between 10% and 15% by volume of the total binders. That is, the binders complement each other to reach all the binders in the concrete. The sum of binders, first, second and third, can reach between 10% and 10.5% of the total volume of concrete.

Another advantageous option in the dosage of the fractions is that the fine fraction is between 15% and 20% of the total volume of concrete, the medium fraction is between 20% and 25% of the total volume of concrete, the coarse fraction is between 10% and 15% of the total volume of concrete. Additionally, the dust fraction can be between 15% and 25% of the total volume of concrete when it is limestone sand and between 10% and 20% of the total volume of concrete when it is siliceous sand.

Another advantageous option is that the metallic and/or plastic fibers are between 0.5% and 1.0% of the total volume of the concrete.

Another advantageous option is that the water is between 5% and 15% of the total volume of concrete, the additives comprise a plasticizing additive and it accounts for between 0.4% and 0.6% of the total volume of concrete.

A detail of concrete is that the dust fraction is particles of size less than or equal to 0.5 mm, the fine fraction is particles of size greater than 0.5 mm and less than or equal to 4 mm, the medium fraction are particles of size greater than 4 mm and less than or equal to 12 mm, the coarse fraction is particles with a size greater than 12 mm and less than or equal to 20 mm.

Another detail of the concrete is that the ground granulated iron and steel slag are particles of size up to 0.01 mm.

Another detail of the concrete is that the white ladle furnace slag is particles of size up to 0.1 mm.

Another detail of concrete is that the metallic and/or plastic fibers are particles with a length between 10 mm and 50 mm and an equivalent diameter between 0.2 mm and 1 mm.

The invention is also the process for making dry-consistency sustainable concrete as described in its most general manner above, comprising the following steps in sequence:

-addition of 90% by volume of the water and all the aggregates, including recycled concrete aggregate, and binders, with Portland cement being a first binder, ground granulated iron and steel slag a second binder, and white ladle furnace slag a third conglomerate;

- first mixed;

- first rest;

- second mixed;

- addition of 10% by volume of water and additives;

- third mixed;

- second rest.

An advantageous option on the mixing and standing times is that each stage of mixing lasts between 1 minute and 3 minutes, each resting stage lasts between 1 minute and 2 minutes. Specifically, each mixing stage lasts 2 minutes, each resting stage lasts 1 minute.

Following the proportions mentioned according to the aforementioned procedure, various mixtures for the dry-consistency sustainable concrete object of the invention can be obtained. All the mixtures were of dry consistency, with a seat in the Abrams cone of less than 2 mm, according to the international specifications for the characterization of dry roller-compacted concrete (EN 206). This made it necessary to carry out the Vebe consistometer test, evaluating the settling of the mixture and its density after being subjected to vibration. The vibration time values in the Vebe consistometer were between 5 and 6 s, the settlement between 4 and 5 cm and the density of the resulting mass between 2.2 and 2.3 Mg/m3.

The compressive strength of the mixtures at 1 day (early ages) was between 40 and 45 MPa, while the compressive strength values at 28 days (normalized age) were between 50 and 55 MPa.

Example

Two mixtures are considered as an example, called RCC-AH-M (metal fibers in 0.7% of the total volume of concrete) and RCC-AH-P (plastic fibers in 0.7% of the total volume of concrete). These mixtures serve only as an illustrative example, the results depending on the particular characteristics of the materials used: characteristics of Portland cement, recycled concrete aggregate, the two types of slag used as binder and natural aggregates.

The chemical composition of recycled concrete aggregate (RCA), ground granulated iron and steel slag (GGBFS) and white ladle furnace slag (LFS) is shown in Table 1 (expressed in %):

Table 1. Recycled concrete aggregate chemical composition (RCA), iron and steel slag ground granulated (GGBFS) and white ladle furnace slag (LFS)

The characteristics of the metallic and plastic fibers used are shown in Table 2:

Table ^2. Characteristics of the fibers used

The dosage of the mixtures is shown in Table 3:

Table 3. Dosage of the mixtures (kg/m3)

The properties in the fresh state are shown in Table 4 (runoff class in parentheses):

Table 4. Properties in the fresh state

The properties in the hardened state that describe the behavior in the hardened state are described in Table 5:

Table 5. Properties in hardened state

Claims (15)

1. -Sustainable dry-consistency concrete comprising Portland cement as the first binder, aggregates, water and additives, characterized in that it comprises metal and/or plastic fibers, ground granulated iron and steel slag as the second binder and white ladle furnace slag as the third binder , the aggregates comprise recycled concrete aggregate, being the entire coarse fraction, the entire medium fraction and the entire fine fraction of the concrete of said recycled concrete aggregate. 2. -Concrete according to claim 1 comprising powder fraction of a mixture of limestone and siliceous sand. 3. -Concrete according to claim 1 in which the Portland cement as the first binder is between 40% and 55% by volume of the total binders, the ground granulated iron and steel slag as the second binder is between 35% and 45%. in volume of the total binders, white ladle furnace slag as the third binder is between 10% and 15% in volume of the total binders. 4. -Concrete according to claim 3 in which the sum of the binders, first, second and third, represents between 10% and 10.5% of the total volume of concrete. 5. -Concrete according to claim 1 in which the fine fraction is between 15% and 20% of the total volume of concrete, the average fraction is between 20% and 25% of the total volume of concrete, the coarse fraction is between 10% and 15% of the total volume of concrete. 6. -Concrete according to claim 2 in which the dust fraction is between 15% and 25% of the total volume of concrete when it is limestone sand and between 10% and 20% of the total volume of concrete when it is siliceous sand . 7. -Concrete according to claim 1 in which the metal and/or plastic fibers are between 0.5% and 1.0% of the total volume of the concrete. 8. -Concrete according to claim 1 in which the water is between 5% and 15% of the total volume of concrete, the additives comprise a plasticizer additive and represents between 0.4% and 0.6% of the volume total concrete. 9. -Concrete according to claim 2 in which the powder fraction is particles with a size less than or equal to 0.5 mm, the fine fraction is particles with a size greater than 0.5 mm and less than or equal to 4 mm, the fraction medium are particles with a size greater than 4 mm and less than or equal to 12 mm, the coarse fraction are particles with a size greater than 12 mm and less than or equal to 20 mm. 10. -Concrete according to claim 1 in which the ground granulated iron and steel slag are particles of size up to 0.01 mm. 11. -Concrete according to claim 1 in which the white ladle furnace slag are particles of size up to 0.1 mm. 12. -Concrete according to claim 1, in which the metallic and/or plastic fibers are particles with a length between 10 mm and 50 mm and an equivalent diameter between 0.2 mm and 1 mm. 13. -Procedure for the production of sustainable dry consistency concrete according to claim 1, characterized in that it comprises the following stages in sequence: - addition of 90% by volume of water and all aggregates, including recycled concrete aggregate, and binders, Portland cement being a first binder, ground granulated iron and steel slag a second binder, and white ladle furnace slag a third conglomerate; - first mixed; - first rest; - second mixed; - addition of 10% by volume of water and additives; - third mixed; - second rest. 14. -Procedure according to claim 13, wherein each mixing stage lasts between 1 minute and 3 minutes, each rest stage lasts between 1 minute and 2 minutes. 15. -Procedure according to claim 13, wherein each mixing stage lasts 2 minutes, each rest stage lasts 1 minute.