A high-temperature resistant concrete and its preparation method

Abstract

This invention relates to the field of high-temperature resistant concrete technology, and discloses a high-temperature resistant concrete and its preparation method. The steps are: precast porous concrete; autoclaving; curing with sodium carbonate or potassium carbonate solution; inserting reinforcing bars into the interconnecting holes of the concrete and injecting grout. The concrete components are: 500-900 parts of nickel-iron slag aggregate, 150-400 parts of water-slag sand, 100-200 parts of cement clinker, 200-300 parts of lithium slag powder, 50-100 parts of mineral powder, 30-50 parts of rice husk ash, 30-50 parts of steel fiber, 5-20 parts of plant fiber, 50-100 parts of activator, 160-180 parts of water, and 4-8 parts of water-reducing agent. This invention, without reducing the concrete strength, artificially creates pores using steel and plant fibers to provide channels for water vapor transport at high temperatures, and improves the high-temperature resistance of the concrete by altering the composition of hydration products through autoclaving and carbonate solution curing.

Description

Technical Field

[0001] This invention relates to the field of high-temperature resistant concrete technology, and in particular to a high-temperature resistant concrete and its preparation method. Background Technology

[0002] Currently, certain structural components of industrial buildings require long-term service in high-temperature environments, such as flue walls and slag discharge outlets in heating plants, slag pools in steel plants, and foundation structures of electric furnaces. The main causes of damage to ordinary concrete after exposure to high temperatures include: 1) Inconsistent volume deformation between aggregates or between aggregates and the paste after high temperatures, leading to internal cracking; 2) The main component of river sand is quartz, which transforms from the α-phase to the β-phase at 573℃, causing volume expansion; 3) The hydration products of cementitious materials in concrete, such as ettringite, decompose above 80℃, Ca(OH)2 above 450℃, hydrated calcium silicate above 600℃, and calcium carbonate and calcium carbonate aggregates above 800℃, resulting in a loose concrete structure and a significant reduction in strength; 4) Concrete is a three-phase material (solid, liquid, and vapor). At high temperatures, the liquid phase in concrete vaporizes, increasing in volume, but the concrete structure remains relatively dense, leading to cracking.

[0003] Currently, the main methods to improve the high-temperature resistance of concrete are to use high-temperature resistant aggregates: refractory bricks as aggregates, recycled materials from heating furnace walls as coarse aggregates, waste electrical porcelain as coarse aggregates, blast furnace slag as fine aggregates, stainless steel electric furnace slag as fine aggregates, heat-treated steel slag as fine aggregates, vanadium-titanium slag as coarse and fine aggregates, nickel-iron slag as aggregates, glass slag as coarse and fine aggregates, and other high-alumina waste as aggregates, etc.

[0004] Patent 202210901162.7 discloses a high-temperature resistant concrete, mainly composed of cement, fly ash, mineral powder, volcanic rock, slag, coal-to-oil, silica fume, water-reducing agent, steel slag powder, titanium carbide silicon powder, ferrochrome slag, fiber, and water. The high-temperature resistance of the concrete is improved by using silica fume, ferrochrome slag, and titanium carbide.

[0005] Patent 202210236773.4 discloses a high-alkalinity, high-temperature resistant, ultra-high-performance concrete material and its preparation method. The high-temperature resistance of the concrete is improved by using 4% to 8% silicon-rich mineral admixtures, 3% to 8% high-alumina mineral admixtures, and steel fibers and synthetic fibers.

[0006] Patent 201910794953.2 discloses an energy-saving and high-temperature resistant concrete and its preparation method, wherein the composition and proportion of the raw materials are as follows: cement 310-330 kg / m³ 3 ; fly ash 50-60 kg / m³ 3 Crushed stone 600-800 kg / m³ 3River sand 700-730 kg / m³ 3 Polycarboxylate high-performance water-reducing agent 5-5.5 kg / m³ 3 300-400 kg / m³ of recycled coarse aggregate 3 Porous nanomaterials 10-30 kg / m 3 Nanofiller 20-40 kg / m 3 High-temperature resistant fiber 50~100kg / m 3 Nanomaterials and nanofillers are used to improve the high-temperature resistance of concrete.

[0007] Patent 202110509816.7 discloses a high-temperature resistant concrete and its preparation method. The concrete is modified by phenolic epoxy phenolic resin, phenolic amine, defoamer and filler to improve the high-temperature resistance of aggregates. Then, the high-temperature resistant concrete is prepared by aggregates, binders (water glass and sodium fluorosilicate), admixtures (burnt clay and brick powder), water and so on.

[0008] Patent 202111671704.8 discloses a high-temperature high-strength heat-resistant concrete, its preparation method and application. The heat-resistant materials, such as alumina-containing refractory aggregate, refractory recycled material, aluminate cement, refractory clay powder, as well as silica powder, fly ash, boric acid, and nano silica sol, compensate for the strength loss of the heat-resistant concrete in the high-temperature stage and enhance its long-lasting heat resistance. Summary of the Invention

[0009] Purpose of the invention: To address the problems existing in the prior art, this invention provides a high-temperature resistant concrete and its preparation method, solving the problem that traditional concrete is not resistant to high temperatures.

[0010] Technical solution: This invention provides a method for preparing high-temperature resistant concrete, comprising the following steps:

[0011] S1. Precast porous concrete, wherein the pores in the porous concrete penetrate both inside and outside the porous concrete and the volume of the pores accounts for 5% to 15% of the total volume of the porous concrete;

[0012] S2. Perform autoclaving;

[0013] S3. After demolding, the porous concrete is immersed in a Na2CO3 or K2CO3 solution for curing for 1-3 days; the concentration of the Na2CO3 or K2CO3 solution is 0.1%-2.0%;

[0014] S4. Insert reinforcing bars into the holes of the porous concrete and pour in grout.

[0015] Further, in S1, the concrete is composed of the following parts by weight: 500-900 parts of nickel-iron slag aggregate, 150-400 parts of water-slag sand, 100-200 parts of cement clinker, 200-300 parts of lithium slag powder, 50-100 parts of mineral powder, 30-50 parts of rice husk ash, 30-50 parts of steel fiber, 5-20 parts of plant fiber, 50-100 parts of activator, 160-180 parts of water, and 4-8 parts of water-reducing agent.

[0016] Furthermore, the steel fiber has a hollow structure, and there are communicating holes between the hollow structure and the outer surface of the steel fiber.

[0017] Furthermore, the activator, by mass, consists of 30-70 parts NaOH and 30-70 parts Na2SiO3.

[0018] Preferably, in S2, the steam pressure for autoclaving is 1.5~2.5MPa, and the curing time is 3~5 hours.

[0019] Beneficial effects: Without reducing the strength of concrete, this invention creates artificial pores using steel fibers and plant fibers to provide channels for the transmission of water vapor at high temperatures, and improves the high-temperature resistance of concrete by altering the composition of hydration products through autoclaving and carbonate solution curing.

[0020] The specific beneficial effects of this invention are as follows:

[0021] 1) By creating holes in the concrete and curing it with sodium carbonate solution, the coarse calcium hydroxide crystals generated under autoclaving conditions can be reacted into calcium carbonate, thereby increasing the density of the autoclaved concrete.

[0022] 2) In addition to improving crack resistance, the presence of steel fibers and plant fibers also provides a transmission path for the migration of moisture and the reduction of vapor pressure in concrete at high temperatures, thus preventing the concrete from cracking due to excessive vapor pressure. At high temperatures, plant fibers carbonize and reduce in volume, which can absorb the energy brought by the expansion of concrete at high temperatures. At the same time, hot steam is also transmitted outward through the channels of plant fiber carbonization, which also prevents the concrete from cracking.

[0023] 3) Autoclaving can change the composition of cement hydration products and increase the proportion of tobermorite in cement hydration products, thereby improving the heat resistance of hydration products. In addition, lithium slag contains a large amount of low-activity spodumene. Under high temperature conditions, unreacted spodumene reacts with calcium hydroxide, a cement hydration product, to form more stable tobermorite, which can improve the high temperature resistance of concrete.

[0024] 4) The cement content in the cementitious material is relatively low while the lithium slag powder and rice husk ash are relatively high, which can reduce the calcium hydroxide content in the cement. In order to avoid the prolonged setting time caused by the high content of lithium slag powder and rice husk ash, this invention directly uses cement clinker to replace cement, and uses an activator to improve the hydration activity of the cementitious material and change the composition of the hydration products.

[0025] 5) By setting steel bars in the holes of porous concrete, the strength of the concrete of the present invention can be guaranteed to be no less than that of traditional concrete. In addition, the connection channels between precast components are increased, which can improve the integrity of the precast components. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the embodiments.

[0027] Implementation method 1:

[0028] A method for preparing high-temperature resistant concrete includes the following steps:

[0029] 1) Precast porous concrete, wherein the pores in the porous concrete penetrate both inside and outside the porous concrete, and the volume of the pores accounts for 5% of the total volume of the porous concrete;

[0030] 2) Perform autoclaving;

[0031] 3) After demolding, the porous concrete is immersed in a 0.1% Na2CO3 solution for curing for 3 days;

[0032] 4) Insert steel bars into the holes of the porous concrete and pour in grout.

[0033] The porous concrete described in step 1) is composed of the following parts by weight: 900 parts nickel-iron slag aggregate, 150 parts water slag sand, 200 parts cement clinker, 200 parts lithium slag powder, 50 parts mineral powder, 50 parts rice husk ash, 50 parts steel fiber, 5 parts plant fiber, 50 parts activator, 180 parts water, and 4 parts water-reducing agent.

[0034] The activator, by mass, consists of 40 parts NaOH and 60 parts Na2SiO3.

[0035] The steel fiber has a hollow structure, and there are connecting holes between the hollow structure and the outer surface of the steel fiber.

[0036] The steam pressure for autoclaving is 1.5 MPa, and the curing time is 5 hours.

[0037] Implementation Method 2:

[0038] A method for preparing high-temperature resistant concrete includes the following steps:

[0039] 1) Precast porous concrete, wherein the pores in the porous concrete penetrate through the inside and outside of the porous concrete, and the volume of the pores accounts for 15% of the total volume of the porous concrete;

[0040] 2) Perform autoclaving;

[0041] 3) After demolding, the porous concrete is immersed in a 1.0% K2CO3 solution for curing for 2 days;

[0042] 4) Insert steel bars into the holes of the porous concrete and pour in grout.

[0043] The porous concrete described in step 1) consists of the following parts by weight: 500 parts nickel-iron slag aggregate, 400 parts water slag sand, 100 parts cement clinker, 300 parts lithium slag powder, 100 parts mineral powder, 50 parts rice husk ash, 50 parts steel fiber, 10 parts plant fiber, 100 parts activator, 170 parts water, and 7 parts water-reducing agent.

[0044] The activator, by mass, consists of 30 parts NaOH and 70 parts Na2SiO3.

[0045] The steel fiber has a hollow structure, and there are connecting holes between the hollow structure and the outer surface of the steel fiber.

[0046] The steam pressure for autoclaving is 1.5 MPa, and the curing time is 5 hours.

[0047] Implementation Method 3:

[0048] A method for preparing high-temperature resistant concrete includes the following steps:

[0049] 1) Precast porous concrete, wherein the pores in the porous concrete penetrate through the inside and outside of the porous concrete, and the volume of the pores accounts for 10% of the total volume of the porous concrete;

[0050] 2) Perform autoclaving;

[0051] 3) After demolding, the porous concrete is immersed in a 2.0% Na2CO3 solution for curing for 1 day;

[0052] 4) Insert steel bars into the holes of the porous concrete and pour in grout.

[0053] The porous concrete described in step 1) is composed of the following parts by weight: 800 parts of nickel-iron slag aggregate, 300 parts of water slag sand, 150 parts of cement clinker, 200 parts of lithium slag powder, 80 parts of mineral powder, 50 parts of rice husk ash, 30 parts of steel fiber, 15 parts of plant fiber, 70 parts of activator, 170 parts of water, and 7 parts of water-reducing agent.

[0054] The activator, by mass, consists of 40 parts NaOH and 60 parts Na2SiO3.

[0055] The steel fiber has a hollow structure, and there are connecting holes between the hollow structure and the outer surface of the steel fiber.

[0056] The steam pressure for autoclaving is 2.0 MPa, and the curing time is 4 hours.

[0057] Implementation Method 4:

[0058] A method for preparing high-temperature resistant concrete includes the following steps:

[0059] 1) Precast porous concrete, wherein the pores in the porous concrete penetrate through the inside and outside of the porous concrete, and the volume of the pores accounts for 10% of the total volume of the porous concrete;

[0060] 2) Perform autoclaving;

[0061] 3) After demolding, the porous concrete is immersed in a 1.5% K2CO3 solution for curing for 3 days;

[0062] 4) Insert steel bars into the holes of the porous concrete and pour in grout.

[0063] The porous concrete described in step 1) consists of the following parts by weight: 800 parts nickel-iron slag aggregate, 400 parts water slag sand, 150 parts cement clinker, 250 parts lithium slag powder, 70 parts mineral powder, 40 parts rice husk ash, 40 parts steel fiber, 10 parts plant fiber, 60 parts activator, 160 parts water, and 8 parts water-reducing agent.

[0064] The activator, by mass, consists of 70 parts NaOH and 30 parts Na2SiO3.

[0065] The steel fiber has a hollow structure, and there are connecting holes between the hollow structure and the outer surface of the steel fiber.

[0066] The steam pressure for autoclaving described in step 3) is 2.5 MPa, and the curing time is 3 hours.

[0067] Performance testing

[0068] Table 1 shows the performance evaluation indicators of this invention. The test method for the mechanical properties of concrete after high temperature is as follows: The concrete prepared in Embodiments 1-4 and the concrete prepared in the comparative example are made into cubic specimens with a side length of 500 mm. After standard curing for 28 days, they are taken out and dried naturally, and then cut into 100 mm × 100 mm × 100 mm samples. They are subjected to high temperature tests at 200 °C, 500 °C and 800 °C for 3 hours respectively, with a heating rate of 10 °C / min. After that, the furnace door is opened and the concrete specimens are naturally cooled to room temperature to test the compressive strength of the concrete specimens. The number of cracks on the surface of the cube is observed and recorded by the naked eye.

[0069] For the compressive strength test, the sample needs to be cut into 100mm×100mm×100mm pieces for testing, and the test method refers to GB50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete". In addition, the concrete mix proportion prepared in the comparative ratio uses 395 parts of C50 concrete P·O42.5 cement, 60 parts of mineral powder, 50 parts of fly ash, 720 parts of river sand, 1100 parts of aggregate, 165 parts of water, and 10 parts of PCA water-reducing agent.

[0070]

[0071] As shown in Table 1, the initial strength of the concrete prepared by embodiments 1-4 is not lower than that of the comparative example. At the same time, in the compressive strength test, the strength of the concrete prepared by embodiments 1-4 decreased less than that of the comparative example, and there was no cracking or cracking at high temperature.

[0072] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing high-temperature resistant concrete, characterized in that, Includes the following steps: S1. Precast porous concrete, wherein the pores in the porous concrete penetrate both inside and outside the porous concrete and the volume of the pores accounts for 5% to 15% of the total volume of the porous concrete; S2. Perform autoclaving; S3. After demolding, the porous concrete is immersed in a Na2CO3 or K2CO3 solution for curing for 1-3 days; the concentration of the Na2CO3 or K2CO3 solution is 0.1%-2.0%; S4. Insert reinforcing bars into the holes of the porous concrete and pour in grout; In S1, the porous concrete is composed of the following parts by weight: 500-900 parts of nickel-iron slag aggregate, 150-400 parts of water slag sand, 100-200 parts of cement clinker, 200-300 parts of lithium slag powder, 50-100 parts of mineral powder, 30-50 parts of rice husk ash, 30-50 parts of steel fiber, 5-20 parts of plant fiber, 50-100 parts of activator, 160-180 parts of water, and 4-8 parts of water-reducing agent.

2. The method for preparing high-temperature resistant concrete according to claim 1, characterized in that: The steel fiber has a hollow structure, and there are connecting holes between the hollow structure and the outer surface of the steel fiber.

3. The method for preparing high-temperature resistant concrete according to claim 1, characterized in that: The activator, by mass, consists of 30-70 parts NaOH and 30-70 parts Na2SiO3.

4. The method for preparing high-temperature resistant concrete according to claim 1, characterized in that: In S2, the steam pressure for autoclaving is 1.5~2.5MPa, and the curing time is 3~5 hours.

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