Environment-friendly high and low temperature resistant concrete and application thereof

Abstract

The invention provides environment-friendly high and low temperature resistant concrete and application thereof, and the concrete is prepared from 250-280 Kg of Portland cement, 60-80 Kg of fly ash, 15-20 Kg of fully-densified silica fume, 1-2 Kg of synthetic fiber and 5-8 Kg of a water reducing agent on the basis of per cubic meter of concrete. The specific surface area of silicon dioxide in the fully-densified micro-silicon powder is 50000-70000 cm < 2 > / g, the breaking strength of the synthetic fiber is 1000-1100 MPa, the elastic modulus of the synthetic fiber is 10000-11000 MPa, and the elongation at break of the synthetic fiber is 28-32%. The concrete provided by the invention is simple in formula and low in construction requirement, can improve the crack resistance of the concrete, meet the bending and tensile strength of the concrete and reduce the generation of cement concrete surface cracks in extreme weather under the condition of reducing the cement consumption, can be successfully suitable for fields with high pavement requirements such as airports, and is long in service life, energy-saving and environment-friendly.

Description

Technical Field

[0001] This invention belongs to the field of concrete technology, specifically providing an environmentally friendly high and low temperature resistant concrete and its application. Background Technology

[0002] Airport concrete pavements are mainly used in projects such as aprons, runways, taxiways, and patrol roads. Concrete pavements are large in volume and require a high amount of cement. Using low-carbon concrete can significantly reduce cement usage, thereby reducing carbon emissions and environmental pollution. In tropical regions, the Middle East, and other areas with high summer temperatures, concrete surfaces are prone to drying shrinkage cracks during construction. In winter, the freeze-thaw cycle can cause microstructural damage and surface cracks in concrete pavements.

[0003] Airport pavements bear significant aircraft loads, and for busy airports with frequent takeoffs and landings, high flexural strength is required. Existing low-carbon concrete mixes for airport pavements are complex, involving numerous additives, increasing implementation difficulty and operational complexity. A major drawback of current low-carbon concrete technology is that reducing cement usage lowers the durability of the concrete, especially under extreme weather conditions such as high temperatures and extreme cold, where concrete performance fails to meet requirements. Ensuring the durability of low-carbon cement concrete pavements is a key factor affecting their application.

[0004] Therefore, it is of great significance to develop a type of concrete that has excellent performance in extreme high and low temperature environments, has a simple and easy-to-construct formula, and meets low carbon requirements. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in the prior art. Therefore, one object of this invention is to provide an environmentally friendly, high and low temperature resistant concrete and its applications.

[0006] In existing airport pavement construction, the national standard requires at least 310 kg of cement to be added to every cubic meter of concrete. This results in low carbon and environmental performance, and airport pavement has relatively high requirements, especially in extreme environments, where ensuring the safe operation of the pavement is essential.

[0007] In view of this, in a first aspect, the present invention provides an environmentally friendly high and low temperature resistant concrete, wherein per cubic meter of concrete, the concrete comprises: 250-280 kg of silicate cement, 60-80 kg of fly ash, 15-20 kg of fully densified microsilica powder, 1-2 kg of synthetic fiber, and 5-8 kg of water-reducing agent; wherein the specific surface area of ​​silica in the fully densified microsilica powder is 50,000-70,000 cm². 2 / g, the tensile strength of the synthetic fiber is 1000-1100MPa, the elastic modulus of the synthetic fiber is 10000-11000MPa, and the elongation at break of the synthetic fiber is 28-32%.

[0008] The environmentally friendly high and low temperature resistant concrete provided by this invention, by adding a certain amount of fly ash, achieves the requirement of only 250-280 kg of silicate cement per cubic meter of concrete to meet the construction requirements of airport pavement, thus realizing low-carbon and environmentally friendly performance. Simultaneously, the use of fully densified microsilica powder with high specific surface area and synthetic fibers with special mechanical strength improves the flexural strength, compressive strength, and crack resistance of the cement concrete, ensuring excellent performance in extreme environments and extending the service life of the airport pavement. The water-reducing agent optimizes the workability of the fully densified microsilica powder. This invention, through the selection of the above-mentioned materials, has a simple formula, is easy to construct, and through the optimization of the addition amount of various materials, obtains high-performance low-carbon concrete suitable for extreme weather conditions.

[0009] In some embodiments of the present invention, the length of the synthetic fiber is 20-30 mm.

[0010] In some embodiments of the present invention, the fineness of the synthetic fiber is 6-18 dtex.

[0011] In some embodiments of the present invention, the density of the synthetic fiber is 1.2-1.4 g / cm³. 3 .

[0012] Preferably, the concrete comprises: 260-270 kg of silicate cement, 68-72 kg of fly ash, 16-18 kg of fully densified silica fume, 1.3-1.5 kg of synthetic fiber, and 6-7 kg of water-reducing agent; the silica in the fully densified silica fume has a specific surface area of ​​58,000-62,000 cm². 2 / g, the tensile strength of the synthetic fiber is 1050-1070MPa, the elastic modulus of the synthetic fiber is 10500-10900MPa, and the elongation at break of the synthetic fiber is 29-31%.

[0013] In some embodiments of the present invention, the silica content in the fully densified microsilica powder is 90-95%. Using a silica content of 90-95% can significantly improve the early and later strength of concrete, and enhance its impermeability, chemical resistance, freeze-thaw cycle resistance, and abrasion resistance.

[0014] In some embodiments of the present invention, the particle size of silica in the fully encrypted micro silica powder is 3-5 μm.

[0015] In some embodiments of the present invention, the calcination content of the fly ash is no more than 6%, and preferably the fly ash is Class II dry-discharged fly ash. Using fly ash with a calcination content of no more than 6% can improve the workability of concrete, increase workability, reduce bleeding and segregation, significantly reduce the heat of hydration, effectively prevent temperature cracks, and improve the durability of concrete.

[0016] In some embodiments of the present invention, the 28-day flexural strength of the silicate cement is greater than 8.0 MPa, and preferably the silicate cement is 42.5 grade cement.

[0017] In some embodiments of the present invention, the water-reducing agent is selected from shrinkage-reducing polycarboxylate high-efficiency water-reducing agents.

[0018] In some embodiments of the present invention, the water-reducing agent has a water reduction rate greater than 14%.

[0019] In some embodiments of the present invention, the concrete further includes excess coarse aggregate and fine aggregate. Those skilled in the art will understand that coarse aggregate and fine aggregate are commonly added components in concrete; for example, coarse aggregate is crushed stone, and fine aggregate is sand. Typical mix design: aggregate particle size 5~20cm, addition amount 450kg / m³. 3 Approximately 20-40cm aggregate particle size, with an addition rate of 800kg / m³. 3 Approximately 600 kg / m³ of medium to coarse sand was added. 3 The mix ratio is determined on-site based on the condition of the stone and sand materials, and the mix ratio is different for different rocks.

[0020] In a second aspect, the present invention proposes the application of the above-mentioned environmentally friendly high and low temperature resistant concrete in airport pavement.

[0021] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: The concrete formula provided by this invention is simple and has low construction requirements. It can improve the crack resistance of concrete while reducing the amount of cement used, meet the flexural strength requirements of concrete, reduce the generation of surface cracks in cement concrete under extreme weather conditions, and can be successfully applied to sites with high pavement requirements such as airports. It has a long service life and is energy-saving and environmentally friendly. Detailed Implementation

[0022] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. The invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the invention in any way.

[0023] Example 1 This embodiment provides a type of concrete, with the following specific composition per cubic meter: 265 kg of Portland cement, cement grade 42.5; 70 kg fly ash, Grade II dry fly ash; 17kg of fully encrypted microsilica powder, with a silica content of 92% and a silica specific surface area of ​​60,000 cm². 2 / gm; 1.4 kg synthetic fiber, with a breaking strength of 1060 MPa, an elastic modulus of 10870 MPa, a breaking elongation of 30%, a length of 20-30 mm, a fineness of 6-18 dtex, and a density of 1.3 g / cm³. 3 ; 6kg water-reducing agent, shrinkage-reducing polycarboxylate high-efficiency water-reducing agent.

[0024] 470 kg of coarse aggregate (5-20 cm thick); 820 kg of coarse aggregate (20-40 cm thick); 610 kg of medium-coarse sand.

[0025] Example 2 This embodiment provides a type of concrete, with the following specific composition per cubic meter: 270 kg of Portland cement, cement grade 42.5; 75 kg fly ash, Grade II dry fly ash; 20kg of fully encrypted microsilica powder, with a silica content of 90% and a silica specific surface area of ​​55,000 cm². 2 / gm, the average particle size of silica is 4μm; 1.8 kg synthetic fiber, with a breaking strength of 1060 MPa, an elastic modulus of 10870 MPa, a breaking elongation of 30%, a length of 20-30 mm, a fineness of 6-18 dtex, and a density of 1.3 g / cm³. 3 ; 7kg water-reducing agent, shrinkage-reducing polycarboxylate high-efficiency water-reducing agent.

[0026] 470 kg of coarse aggregate (5-20 cm thick); 820 kg of coarse aggregate (20-40 cm thick); 610 kg of medium-coarse sand.

[0027] Comparative Example 1 Comparative Example 1 provides a type of concrete that differs from Example 1 only in that it uses nano-silica with a particle size in the nanometer range.

[0028] Comparative Example 2 Comparative Example 2 provides a type of concrete that differs from Example 1 only in that it uses polyacrylonitrile fibers instead of the synthetic fibers in Example 1. The polyacrylonitrile fibers have a length of 6-20 mm, a fineness of 1.9 dtex, and a specific gravity of 1.18 g / cm³. 3 It has a tensile strength of 385 MPa, an elastic modulus of 17.1 MPa, and an elongation at break of 20%.

[0029] Comparative Example 3 Comparative Example 3 provides a conventional concrete without the addition of fly ash, silica fume, or fiber materials.

[0030] The concrete properties provided in the examples and comparative examples were tested, and the specific methods are as follows: 1. Standard Curing Small Beam Bending Tensile Strength Test: According to the "Test Procedures for Cement and Cement Concrete in Highway Engineering (JTG E30)" (T0551 / T0558), "Test Method for Bending Tensile Strength of Cement Concrete," a standard 150*150*550 small beam was used. A concrete bending tensile strength and bending tensile elastic modulus testing device with double-point loading at three-thirds points and three-point free support was employed. The arithmetic mean of the three specimen measurements was taken as the measured value. If the difference between the maximum or minimum value and the median value exceeds 15% of the median value, the maximum and minimum values ​​are discarded, and the median value is used as the bending tensile strength of the specimen. If the difference between the maximum and minimum values ​​and the median value both exceed 15% of the median value, the test results for that group are invalid.

[0031] 2. Freeze-thaw cycle test. According to the "Test Procedures for Cement and Cement Concrete in Highway Engineering.JTG E30" and T0565 "Test Method for Freeze-Thaw Resistance of Cement Concrete", 100mm x 100mm x 400mm column concrete specimens were used. After 28 days of curing, the specimens were subjected to freeze-thaw cycles between 3℃ and -16℃ for a total of 300 cycles. The relative dynamic modulus of elasticity and the mass loss rate of the specimens were tested.

[0032] 3. Early cracking test: According to the "Test Procedures for Cement and Cement Concrete in Highway Engineering.JTG E30" and T 0573 "Test Method for Early Cracking Sensitivity of Cement Concrete (Plate Method)", the test is conducted in a constant temperature and humidity chamber with a temperature of 30℃±2℃ and a relative humidity of 60%±5%. After the concrete is poured into the mold, it is smoothed and vibrated for curing. The position and speed of the fan are adjusted so that the wind speed at 100mm directly above the center of the specimen surface is 5m / s±0.5m / s, and the wind direction should be parallel to the specimen surface. The cracking process on the plate surface is observed, and the cracks should be measured and read after 24h±0.5h.

[0033] 4. Abrasion Resistance Test: Refer to the "Test Procedures for Cement and Cement Concrete in Highway Engineering (JTG E30)" and T 0567 "Test Method for Abrasion Resistance of Cement Concrete". Use standard 150mm x 150mm x 150mm cube specimens. After curing for 27 days, remove the specimens from the curing location, wipe off surface moisture, and allow them to air dry naturally for 12 hours. Then, place them in a 60℃ ± 5℃ oven for 12 hours until constant weight. Place the specimen on the horizontal turntable of the abrasion testing machine (the grinding surface should be perpendicular to the top surface from the initial molding stage) and gently secure it with clamps. Grind for 30 revolutions under a 200N load, then remove the specimen, clean off surface dust, weigh it, and record the corresponding mass m1. This mass is taken as the initial mass of the specimen. Then, grind for 60 revolutions under a 200N load, remove the specimen, clean off surface dust, weigh it, and record the remaining mass m2. The test results are expressed as wear per unit area.

[0034] 5. Impact Resistance Test. The impact resistance test method for concrete in GB / T 21120-2018, "Synthetic Fiber Concrete for Cement Concrete and Mortar," was adopted. 28-day-old fiber-reinforced concrete specimens and reference concrete specimens with the same mix proportions but without fiber were used. A layer of grease was evenly applied to the bottom surface of each specimen. A 63.5mm diameter hard steel ball was placed at the center of the upper surface of the specimen. A 4.5kg square steel hammer was dropped freely from a height of 600mm from the center of the hammer to the upper surface of the specimen, impacting the steel ball. After each impact, the crack propagation on the specimen surface was carefully observed until the specimen contacted any three of the four baffles on the impact base. This point was considered specimen failure. The number of impacts that caused failure was recorded. The ratio of the number of impacts that caused failure in the tested concrete to the number of impacts that caused failure in the reference concrete was called the impact resistance ratio.

[0035] The performance test results of the concrete in the examples and comparative examples are shown in Table 1.

[0036] Table 1

[0037] As can be seen from the data in Table 1, compared with the conventional concrete of Comparative Example 3, the present invention improves flexural strength by more than 10%, improves frost resistance by about 10%, significantly improves crack resistance, improves wear resistance by 20%, and improves impact resistance by 56%.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An environmentally friendly high and low temperature resistant concrete, characterized in that, Per cubic meter of concrete, the concrete comprises: 250-280 kg of silicate cement, 60-80 kg of fly ash, 15-20 kg of fully densified silica fume, 1-2 kg of synthetic fiber, and 5-8 kg of water-reducing agent; the specific surface area of ​​silica in the fully densified silica fume is 50,000-70,000 cm². 2 / g, the tensile strength of the synthetic fiber is 1000-1100MPa, the elastic modulus of the synthetic fiber is 10000-11000MPa, and the elongation at break of the synthetic fiber is 28-32%.

2. The concrete according to claim 1, characterized in that, The length of the synthetic fiber is 20-30 mm; And / or, the fineness of the synthetic fiber is 6-18 dtex.

3. The concrete according to claim 1, characterized in that, The density of the synthetic fiber is 1.2-1.4 g / cm³. 3 .

4. The concrete according to any one of claims 1-3, characterized in that, The concrete comprises: 260-270 kg of silicate cement, 68-72 kg of fly ash, 16-18 kg of fully densified silica fume, 1.3-1.5 kg of synthetic fiber, and 6-7 kg of water-reducing agent; the silica in the fully densified silica fume has a specific surface area of ​​58,000-62,000 cm². 2 / g, the tensile strength of the synthetic fiber is 1050-1070MPa, the elastic modulus of the synthetic fiber is 10500-10900MPa, and the elongation at break of the synthetic fiber is 29-31%.

5. The concrete according to any one of claims 1-3, characterized in that, The silica content in the fully encrypted microsilica powder is 90-95%; And / or, the particle size of silica in the fully encrypted micro silica powder is 3-5 μm.

6. The concrete according to any one of claims 1-3, characterized in that, The calcination coefficient of the fly ash is not greater than 6%, and preferably the fly ash is Class II dry-discharged fly ash.

7. The concrete according to any one of claims 1-3, characterized in that, The silicate cement has a 28-day flexural strength greater than 8.0 MPa, and preferably the silicate cement is 42.5 grade cement.

8. The concrete according to any one of claims 1-3, characterized in that, The water-reducing agent is selected from shrinkage-reducing polycarboxylate high-efficiency water-reducing agents; And / or, the water reduction rate of the water-reducing agent is greater than 14%.

9. The concrete according to any one of claims 1-3, characterized in that, The concrete also includes excess coarse and fine aggregates.

10. The application of the environmentally friendly high and low temperature resistant concrete according to any one of claims 1-9 in airport pavement.

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