An airport pavement high flexural strength pumping c40 / 20 concrete and a preparation method thereof

Abstract

The application discloses an airport pavement high-bending-resistance pumping C40 / 20 concrete and a preparation method thereof. 300 kg of P.O 52.5 grade cement, 100 kg of I grade fly ash, 160 kg of water, 750-800 kg of mountain sand, 1890 kg of three-grade gravel and 8.0-9.5 kg of TY-J25 additive are used to prepare the concrete, the water-binder ratio is 0.40, and the slump is 150 mm. The application adopts a composite cementing system, three-grade aggregate and a special additive, and matches a customized roughening process, so that the problems of poor adaptation of 52.5 cement and mountain sand, pumping pipe blockage, difficult simultaneous consideration of anti-skid and strength are solved. The finished product has a 28d compressive strength of greater than or equal to 40 MPa, a bending strength of greater than or equal to 4.5 MPa, a pumping distance of 50-80 m, an anti-skid coefficient of greater than or equal to 0.65 after roughening, a strength loss of less than or equal to 3 %, and a significantly reduced broken slab rate, and is suitable for pavement engineering of airport runways, taxiways, heavy load stations and the like.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a high flexural strength pumpable C40 / 20 concrete for airport pavements and its preparation method. Background Technology

[0002] Airport pavement projects in some regions impose multiple stringent requirements on concrete: the concrete grade must reach C40 or above, the 28-day flexural strength must not be less than 4.5MPa, and it must also meet requirements such as on-site pumping construction, surface roughening for anti-skid properties, and long-term heavy load durability. Due to the limitation of regional resources, river sand resources are scarce in some areas, and mountain sand is generally used as fine aggregate for concrete in the projects. Furthermore, the airport pavement specifications mandate the use of 52.5 grade cement as the core cementing material.

[0003] Most publicly available C40 grade concrete technical solutions for airport pavements use 42.5 grade cement and ordinary river sand as raw materials, combined with single-size crushed stone and general-purpose admixtures, and are constructed using conventional roughening techniques. A typical existing technical mix proportion is as follows: per cubic meter of concrete, there are 320 kg of 42.5 grade cement, 80 kg of Grade I fly ash, 180 kg of water, 780 kg of ordinary river sand, 1890 kg of single 20mm crushed stone, and 8.0 kg of general-purpose admixtures, with a water-cement ratio of 0.45 and a sand ratio of 35%.

[0004] Existing technologies have several shortcomings and cannot adapt to the special working conditions and material conditions of airport pavements in some regions: Poor material compatibility: Existing solutions are designed for 42.5 grade cement and ordinary river sand, failing to consider the characteristics of local mountain sand in some areas, such as high mud content, coarse particles, and high water demand. When directly applied to a 52.5 grade cement and mountain sand system, the rapid hydration rate and high heat of hydration of 52.5 grade cement easily cause concrete shrinkage cracking, and the flexural strength cannot stably reach 4.5 MPa, failing to leverage the performance advantages of high-grade cement; Pumping performance defects: The aggregate gradation and admixture system have not been optimized for the characteristics of mountain sand, using single-size crushed stone and ordinary admixtures, resulting in poor concrete pumping performance. The soil is prone to problems such as insufficient slump and pumping pipe blockage, or excessive slump and aggregate segregation, which cannot meet the needs of large-area and long-distance pumping construction at airports; the roughening process is unreasonable: the conventional roughening process has not been optimized in combination with the setting characteristics of 52.5 grade cement concrete and the surface characteristics of mountain sand. Improper control of roughening time and depth can easily lead to surface sanding, insufficient anti-skid coefficient, or damage to the internal structure of concrete and a significant decrease in flexural strength, making it impossible to simultaneously achieve anti-skid performance and structural strength; the overall coordination is insufficient: the concrete strength, workability, surface performance and durability are difficult to achieve in a coordinated manner, the pavement breakage rate is high, and it cannot meet the long-term use requirements of heavy-load airport pavements.

[0005] Based on the above situation, we will develop a special concrete and matching preparation process that is compatible with 52.5 grade cement and mountain sand, and has high flexural strength, excellent pumpability, anti-slip and durable properties. Summary of the Invention

[0006] The purpose of this invention is to provide a high-flexural-strength pumpable C40 / 20 concrete for airport pavements and its preparation method. Addressing the characteristics of 52.5 grade cement and local mountain sand in some regions, which have high mud content, coarse particles, and high water demand, the mix proportion is optimized. This involves combining three-grade crushed stone with a special compound admixture, along with customized roughening and curing processes. This solves problems such as poor compatibility between 52.5 cement and mountain sand, pumping pipe blockage, and the inability to simultaneously achieve both strength and skid resistance after roughening, thereby improving the construction efficiency and service life of airport pavements.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A type of high flexural strength pumpable C40 / 20 concrete for airport pavements, wherein each cubic meter of concrete is prepared from the following raw materials by weight: 300 kg of P.O52.5 grade cement, 100 kg of Grade I fly ash, 160 kg of tap water, 750-800 kg of mountain sand, 1890 kg of graded crushed stone, and 8.0-9.5 kg of TY-J25 polycarboxylate-based compound pumping admixture; wherein the graded crushed stone consists of 923 kg of 20 mm crushed stone, 230 kg of 10 mm crushed stone, and 737 kg of 5 mm crushed stone; the mass ratio of P.O52.5 grade cement to Grade I fly ash is 3:1, the overall water-cement ratio is 0.40, the sand ratio is 34%-36%, and the concrete slump is 150 mm; the P.O52.5 grade cement... Grade 5 cement meets the following requirements: initial setting time ≥ 4h, final setting time ≤ 8h, alkali content ≤ 0.6%, 3-day compressive strength ≥ 28MPa, 28-day compressive strength ≥ 40MPa; mountain sand meets the following requirements: fineness modulus 2.6~2.8, mud content ≤ 1.5%, mud lump content ≤ 0.5%, chloride ion content ≤ 0.03%; the three-grade crushed stone meets the following requirements: crushing value ≤ 22%, continuous particle size distribution; the TY-J25 type polycarboxylate-based compound pumpable admixture has a water reduction rate ≥ 25%, and is composed of 1.5%~2.0% water-reducing component, 0.2%~0.3% retarding component, and 0.2%~0.3% plasticizing component based on the total mass of the admixture; the admixture dosage is 2.0%~2.5% of the total mass of cementitious materials.

[0008] Furthermore, the amount of mountain sand is preferably 780 kg, and the amount of TY-J25 type polycarboxylate compound pumping admixture is preferably 8.8 kg.

[0009] Furthermore, the P・O52.5 grade cement can be replaced with P・Ⅱ52.5 grade cement, and the cement dosage can be adjusted within the range of 290~310kg.

[0010] Furthermore, the Class I fly ash can be replaced with Class II fly ash, with the fly ash dosage adjusted within the range of 90–110 kg, the cement to fly ash mass ratio maintained at 2.7:1–3.3:1, and the total mass of cementitious materials controlled at 390–410 kg.

[0011] Furthermore, the TY-J25 polycarboxylate-based compound pumping admixture is replaced with a polycarboxylate-based pumping admixture of equivalent performance, with the admixture dosage adjusted within the range of 1.9% to 2.6%, and the concrete slump maintained at 145 to 155 mm.

[0012] A method for preparing high flexural strength pumpable C40 / 20 concrete for airport pavement includes the following steps: Step 1, Raw material preparation: Accurately weigh each raw material according to the proportions; Step 2, mixing: Add P·O52.5 grade cement, grade I fly ash, mountain sand, and grade III crushed stone to a forced mixing equipment and dry mix for 2-3 minutes; then add tap water and TY-J25 type polycarboxylate compound pumpable admixture evenly to the mixing equipment and continue wet mixing for 3-4 minutes to obtain a uniform concrete mixture with a slump of 150mm. Step 3, Pumping and Pouring: Concrete pump trucks are used to transport the mixture, and the pumping pressure is controlled at 10-15MPa. Continuous pumping is carried out, and an immersion vibrator is used to compact the mixture during the pouring process. Step 4, roughening treatment: After the concrete is poured and vibrated, before the initial setting of the concrete and within 2 hours after pouring, a comb-type roughening machine is used to roughen the surface. The roughening direction is perpendicular to the driving direction of the pavement. The spacing between the comb teeth of the roughening machine is 5-8mm, the depth of the comb teeth is 1.0-1.5mm, and the texture depth of the concrete surface after roughening is controlled at 0.7-1.2mm. Step 5, Moisturizing and Maintenance: Immediately after the texturing is completed, cover with geotextile for moisturizing and maintenance, which should last for no less than 10 days.

[0013] Furthermore, in step 2, the dry mixing time is preferably 2.5 min, and the wet mixing time is preferably 3.5 min.

[0014] Furthermore, in step 3, the preferred pumping pressure is 12 MPa, the pumping speed is 20 m³ / h, and the single-stage continuous pumping distance is 50–80 m.

[0015] Furthermore, in step 4, the roughening time is 1.5 hours after concrete pouring, the preferred spacing of the roughening machine comb teeth is 6mm, the preferred depth of the comb teeth is 1.2mm, and the preferred depth of the texture on the concrete surface after roughening is 1.0mm.

[0016] Furthermore, in step 5, the maintenance period is 10 to 15 days, during which water is sprayed 2 to 3 times a day.

[0017] Compared with the prior art, the present invention has the following features and beneficial effects: This invention employs a composite cementitious system, optimizing the mix proportions based on the particle size and mud content characteristics of local mountain sand in certain regions. The water-cement ratio is controlled at 0.40, effectively alleviating the problems of rapid hydration, high heat of hydration, and easy cracking of 52.5 grade cement. The finished concrete has a 28-day compressive strength ≥48MPa and a 28-day flexural strength ≥4.5MPa. The flexural strength is improved compared to existing technologies, with strong raw material compatibility and stable strength indicators that fully meet the airport C40 / 20 high flexural strength pavement standard.

[0018] This invention uses a three-grade crushed stone combination, combined with TY-J25 special compound admixture, to precisely control the slump to 150mm, the concrete pumping pressure to 10-15MPa, and the continuous pumping distance to 50-80m. There is no pipe blockage or aggregate segregation throughout the process, and the pumping efficiency is improved. It is perfectly suited for large-area, long-distance pumping construction scenarios at airports, with excellent pumping performance and suitability for large-area construction.

[0019] Customized texturing process precisely controls the timing of texturing, comb tooth parameters and texture depth. After texturing, the texture depth of the concrete surface is 0.7-1.2mm, and the anti-skid coefficient is ≥0.65, which meets the anti-skid specifications for airport pavement. At the same time, the flexural strength loss caused by texturing is ≤3%, avoiding the defects of conventional texturing process that damage the structure.

[0020] The concrete of this invention has a permeability grade of ≥P6, a freeze-thaw cycle resistance of ≥300 times, a reduced pavement breakage rate, and is suitable for climates characterized by high temperature, high humidity, and heavy rainfall. It exhibits excellent durability, a long service life, and significantly improves the heavy-load durability of airport pavements, reducing subsequent maintenance costs. It is safe, applicable, and has great promotional and practical value. Its widespread application will generate good economic benefits. Attached Figure Description

[0021] Figure 1 This is a flowchart of the preparation process of the present invention; Figure 2 This is a block diagram illustrating the synergistic effect of concrete components in this invention. Detailed Implementation

[0022] To make the technical means, innovative features, objectives and effects of this invention easier to understand, the invention will be further described below.

[0023] The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the invention, and are illustrative and exemplary, and should not be construed as limiting the implementation or scope of the invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0024] This invention provides concrete specifically for use in certain airport pavement projects, including airport runways, taxiways, and heavy-duty apron areas where stringent requirements for strength, flexural strength, skid resistance, and pumpability are necessary. This invention can be used in any heavy-duty building material project that uses 52.5 grade cement and mountain sand as main raw materials and requires pumpable construction, high flexural strength, and high skid resistance.

[0025] A type of high flexural strength pumpable C40 / 20 concrete for airport pavement, wherein each cubic meter of concrete is composed of the following raw materials by weight: 300 kg of P.O52.5 grade cement, 100 kg of grade I fly ash, 160 kg of tap water, 750-800 kg of mountain sand, 1890 kg of grade III crushed stone, and 8.0-9.5 kg of TY-J25 type polycarboxylate compound pumpable admixture.

[0026] The specific proportions of the three-grade crushed stone are as follows: 923 kg of 20 mm crushed stone, 230 kg of 10 mm crushed stone, and 737 kg of 5 mm crushed stone; the mass ratio of P·O52.5 grade cement to grade I fly ash is 3:1, the water-cement ratio is fixed at 0.40, the sand ratio is 34% to 36%, and the slump of the concrete at the factory is strictly controlled at 150 mm.

[0027] Limitations and functions of each raw material: P・O52.5 grade cement (300kg): core cementitious material, providing the strength of the concrete foundation. Technical parameters: initial setting time ≥4h, final setting time ≤8h, alkali content ≤0.6%, 3d compressive strength ≥28MPa, 28d compressive strength ≥40MPa; precise matching of fly ash dosage to suppress the problem of excessively rapid hydration.

[0028] Grade I fly ash (100kg): A mineral admixture that forms a 3:1 composite cementitious system with cement, reducing the heat of cement hydration, improving the workability of concrete, filling the voids between cement particles, and enhancing overall density and durability.

[0029] Tap water (160kg): The mixing water meets the standards for drinking water, is free of impurities, and has a water-cement ratio of 0.40, which ensures that the cement is fully hydrated while avoiding excessive water consumption that could lead to decreased strength and increased shrinkage.

[0030] Mountain sand (750-800kg): fine aggregate, fills the voids in coarse aggregate, optimizes the workability of concrete. Technical parameters: fineness modulus 2.6-2.8, mud content ≤1.5%, mud lump content ≤0.5%, chloride ion content ≤0.03%.

[0031] Grade 3 crushed stone (total 1890kg): coarse aggregate, bearing the main external load, improving the strength, density and flexural strength of concrete, crushing value ≤22%, continuous gradation can maximize the filling of internal voids, while improving pumping smoothness, suitable for heavy-load airport conditions.

[0032] TY-J25 polycarboxylate-based compound pumping admixture (8.0~9.5kg): A special admixture, the dosage is 2.0%~2.5% of the total mass of cementitious materials; water reduction rate ≥25%, composed of water-reducing component (1.5%~2.0%), retarding component (0.2%~0.3%), and plasticizing component (0.2%~0.3%). It can effectively improve the workability of sand concrete, slow down the hydration rate of 52.5 grade cement, maintain slump stability, and completely solve the problems of pumping pipe blockage and segregation.

[0033] As the preferred option, 780 kg of sand and 8.8 kg of TY-J25 admixture should be used per cubic meter of concrete, which is the optimal construction mix ratio.

[0034] This invention allows for reasonable substitution of raw materials: P・O52.5 grade cement can be replaced with P・Ⅱ52.5 grade cement, at a dosage of 290~310kg / m³; Grade I fly ash can be replaced with Grade II fly ash, at a dosage of 90~110kg / m³, ensuring a cement to fly ash ratio of 2.7:1~3.3:1; TY-J25 admixture can be replaced with a polycarboxylate-based pumpable admixture of equivalent performance, at a dosage of 1.9%~2.6%, maintaining a slump of 145~155mm.

[0035] A high flexural strength pumpable C40 / 20 concrete for airport pavement and its preparation method, such as Figure 1 and Figure 2 As shown, the process includes five main steps in sequence: raw material preparation, mixing, pumping and pouring, roughening treatment, and moisture retention and curing. The details are as follows: Raw material preparation: Weigh all raw materials accurately according to the design ratio, verify all indicators of raw materials to ensure that they meet the specifications, and prevent unqualified raw materials from being used.

[0036] Mixing: Using a forced mixing device, first add cement, fly ash, mountain sand, and graded crushed stone and dry mix for 2-3 minutes to ensure uniform mixing of solid materials; then premix tap water and TY-J25 admixture evenly, and slowly add them to the mixing device, and continue wet mixing for 3-4 minutes to finally obtain a concrete mixture with a slump of 150mm. It is preferred to dry mix for 2.5 minutes and wet mix for 3.5 minutes to ensure that all components are fully mixed to form a uniform and stable concrete mixture and ensure workability.

[0037] Pumping and pouring: Concrete pump trucks are used to transport the mixture, with pumping pressure controlled at 10-15MPa, preferably 12MPa, pumping speed at 20m³ / h, and continuous pumping distance of 50-80m in a single section. There is no pipe blockage or segregation throughout the process. After pouring, an immersion vibrator is used to compact the mixture and eliminate defects such as honeycomb and pitting.

[0038] Roughening treatment: After the concrete is poured and vibrated, roughening operation should be carried out within 2 hours before initial setting and after pouring (preferably 1.5 hours after pouring); a comb-type roughening machine should be used, with a comb tooth spacing of 5-8mm (preferably 6mm) and a comb tooth depth of 1.0-1.5mm (preferably 1.2mm), and the roughening direction should be perpendicular to the driving direction of the pavement; after roughening, the texture depth of the concrete surface should be controlled at 0.7-1.2mm to ensure anti-skid performance. This timing and parameters can avoid damage to the internal structure of the concrete and control the flexural strength loss to ≤3%.

[0039] Moisturizing and curing: Immediately after roughening, cover with geotextile for moisturizing and curing. During rainy and humid seasons, cure for 10 to 12 days, and during dry seasons, cure for 12 to 15 days. Spray water 2 to 3 times a day to ensure stable growth of concrete strength and prevent shrinkage cracking.

[0040] Hydration reaction principle: 52.5 grade cement undergoes a hydration reaction with water, generating cementitious substances such as hydrated calcium silicate and hydrated calcium aluminate, which bind aggregates such as sand and graded crushed stone together to form a high-strength, high-durability concrete structure. The core hydration reaction formula is as follows: 3CaO·SiO2+nH2O→xCaO·SiO2·yH2O (hydrated calcium silicate, gelling core)+(3-x)Ca(OH)2; 2CaO·SiO2+nH2O→xCaO·SiO2·yH2O (hydrated calcium silicate)+(2-x)Ca(OH)2; 3CaO·Al2O3+6H2O→3CaO·Al2O3·6H2O (hydrated calcium aluminate).

[0041] (2) Component synergistic working principle: 1. Synergistic effect of cementitious system: 52.5 cement provides a high-strength foundation, and Grade I fly ash fills the voids between cement particles, reducing heat of hydration and shrinkage cracking. The two are mixed in a 3:1 ratio, which not only gives full play to the high strength advantage of 52.5 cement, but also improves the crack resistance and durability of concrete, solving the pain points of rapid hydration and easy cracking of 52.5 cement.

[0042] 2. Aggregate Synergy: Mountain sand, as fine aggregate, fills the voids in the three-grade crushed stone. The three-grade crushed stone (20mm+10mm+5mm) is continuously graded, which maximizes the density of concrete and reduces internal pores. At the same time, the particle characteristics of mountain sand synergize with the crushed stone to optimize the workability of concrete and provide a guarantee for pumping construction.

[0043] 3. Synergistic effect of admixtures: The water-reducing component of TY-J25 admixture reduces water consumption and improves concrete strength; the retarding component inhibits the excessive hydration of 52.5 cement and avoids cracking caused by concentrated heat of hydration; the plasticizing component maintains stable slump and ensures no segregation or pipe blockage during pumping. It is specially adapted to the characteristics of mountain sand with high water demand, so as to achieve synergistic improvement of the overall performance of concrete by each component.

[0044] (3) Construction process coordination principle: The mixing step ensures that the components are evenly distributed, providing a guarantee for the full hydration reaction; the pumping and pouring step ensures the smooth delivery of the concrete mixture by controlling the pumping pressure and speed, and the vibration compaction avoids internal defects; the roughening process is carried out before the initial setting of the concrete, which not only ensures clear surface texture and anti-slip performance, but also does not damage the internal hydration product structure; the moisturizing and curing step provides sufficient moisture for the continuous hydration reaction, ensuring the stable growth of concrete strength, adapting to rainy and humid climates, and avoiding surface cracking.

[0045] Example 1 (Optimal Example, Standard Mix Proportion for Conventional Working Conditions) 1. Raw material ratio (per cubic meter of concrete) 300 kg of P·O52.5 grade cement, 100 kg of Grade I fly ash, 160 kg of tap water, 780 kg of mountain sand (fineness modulus 2.7, mud content 1.2%), 923 kg of 20 mm crushed stone, 230 kg of 10 mm crushed stone, 737 kg of 5 mm crushed stone (crushing value 20%), and 8.8 kg of TY-J25 type admixture (water reduction rate 26%).

[0046] The total amount of cementitious material is 400kg, the water-cement ratio is 0.40, the sand ratio is 35%, and the design slump is 150mm.

[0047] 2. Preparation steps (1) Raw material preparation: Verify all raw material specifications and weigh them accurately; (2) Mixing: Dry mix for 2.5 min, wet mix for 3.5 min, and check the slump to be 150 mm; (3) Pumping and pouring: Pumping pressure 12MPa, pumping speed 20m³ / h, continuous pumping for 60m, and compaction by vibration; (4) Roughening treatment: Roughen the surface 1.5 hours after pouring (before initial setting), with a comb tooth spacing of 6 mm and a comb tooth depth of 1.2 mm. The roughening direction is perpendicular to the direction of travel. (5) Moisturizing and maintenance: Cover with geotextile and spray water 2-3 times a day for 12 days.

[0048] 3. Performance test results 3d compressive strength 28MPa, 3d flexural strength 4.0MPa; 7d compressive strength 38MPa, 7d flexural strength 4.9MPa; 28d compressive strength 50MPa, 28d flexural strength 5.8MPa; Pumping performance: Flow time of 10s using the inverted cone method, 60m continuous pumping without pipe blockage or segregation; Performance after roughening: Surface texture depth 1.0mm, anti-slip coefficient 0.70, flexural strength loss 3%; Durability: Impermeability grade ≥P6, freeze-thaw cycle resistance ≥300 cycles.

[0049] Example 2 (Boundary Example, Lower Limit of Sand Ratio, Lower Limit of Admixture) 1. Raw material ratio (per cubic meter of concrete) 300 kg of P・O52.5 grade cement, 100 kg of Grade I fly ash, 160 kg of tap water, 750 kg of mountain sand (fineness modulus 2.6, mud content 1.4%), 1890 kg of graded crushed stone, 8.0 kg of TY-J25 admixture (water reduction rate 25%), and sand ratio 34%.

[0050] 2. Preparation steps The mixing and pumping steps are the same as in Example 1; the spacing between the comb teeth of the napping machine is 5mm, and the depth of the comb teeth is 1.0mm; the curing time is 10 days.

[0051] 3. Performance test results 28-day compressive strength 48MPa, 28-day flexural strength 4.5MPa; pumping pressure 15MPa, 50m continuous pumping normal; texture depth after roughening 0.8mm, anti-slip coefficient 0.65, flexural strength loss 2.8%; all indicators meet the standards.

[0052] Example 3 (Boundary Example, Upper Limit of Sand Ratio, Upper Limit of Admixture) 1. Raw material ratio (per cubic meter of concrete) 300 kg of P·O52.5 grade cement, 100 kg of Grade I fly ash, 160 kg of tap water, 800 kg of mountain sand (fineness modulus 2.8, mud content 1.0%), 1890 kg of three-grade crushed stone, 9.5 kg of TY-J25 admixture (water reduction rate 27%), and sand ratio 36%.

[0053] 2. Preparation steps The mixing and pumping steps are the same as in Example 1; the spacing between the comb teeth of the napping machine is 8mm, and the depth of the comb teeth is 1.5mm; the curing time is 15 days.

[0054] 3. Performance test results 28-day compressive strength 51 MPa, 28-day flexural strength 5.9 MPa; pumping pressure 10 MPa, 80m continuous pumping normal; texture depth after roughening 1.2 mm, anti-slip coefficient 0.72, flexural strength loss 2.9%; all indicators meet the standards.

[0055] Comparative Example (Existing Technical Solution) 1. Raw material ratio (per cubic meter of concrete) 320kg of 42.5 grade cement, 80kg of Grade I fly ash, 180kg of water, 780kg of ordinary river sand, 1890kg of single 20mm crushed stone, 8.0kg of ordinary admixture, water-cement ratio 0.45, sand ratio 35%, slump 150mm.

[0056] 2. Preparation and Construction Steps The process involves conventional mixing, pumping, roughening, and curing.

[0057] 3. Performance test results The 28-day compressive strength is 42 MPa, and the 28-day flexural strength is 4.6 MPa (poor stability and large fluctuations); the pipe becomes blocked after pumping for 30m; the texture depth after roughening is 0.6mm, the anti-skid coefficient is 0.60, and the flexural strength loss is 6.5%; the impermeability grade is P4, and the freeze-thaw cycle resistance is only 200 cycles. Many indicators do not meet the requirements of airport pavement.

[0058] Through comparison of three sets of embodiments and comparative examples, it can be seen that the concrete of the present invention is significantly superior to the prior art in terms of mechanical strength, pumpability, anti-skid performance and durability. All schemes within the mix proportion range can stably meet the airport pavement specifications and technical requirements.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A type of high flexural strength pumpable C40 / 20 concrete for airport pavement, characterized in that, Each cubic meter of concrete is prepared from the following raw materials by weight: 300 kg of P·O52.5 grade cement, 100 kg of Grade I fly ash, 160 kg of tap water, 750-800 kg of mountain sand, 1890 kg of grade III crushed stone, and 8.0-9.5 kg of TY-J25 polycarboxylate-based compound pumping admixture; wherein the grade III crushed stone consists of 923 kg of 20 mm crushed stone, 230 kg of 10 mm crushed stone, and 737 kg of 5 mm crushed stone; the mass ratio of P·O52.5 grade cement to Grade I fly ash is 3:1, the overall water-cement ratio is 0.40, the sand ratio is 34%-36%, and the concrete slump is 150 mm; the P·O52.5 grade cement meets the following requirements for initial setting: The settling time is ≥4h, the final setting time is ≤8h, the alkali content is ≤0.6%, the 3-day compressive strength is ≥28MPa, and the 28-day compressive strength is ≥40MPa; the mountain sand meets the following requirements: fineness modulus 2.6~2.8, mud content ≤1.5%, mud lump content ≤0.5%, and chloride ion content ≤0.03%; the three-grade crushed stone meets the following requirements: crushing value ≤22%, and continuous particle size distribution; the TY-J25 type polycarboxylate-based compound pumpable admixture has a water reduction rate ≥25%, and is composed of 1.5%~2.0% water-reducing component, 0.2%~0.3% retarding component, and 0.2%~0.3% plasticizing component based on the total mass of the admixture; the admixture dosage is 2.0%~2.5% of the total mass of the cementitious material.

2. The high flexural strength pumpable C40 / 20 concrete for airport pavement according to claim 1, characterized in that, The preferred amount of mountain sand is 780 kg, and the preferred amount of TY-J25 polycarboxylate compound pumping admixture is 8.8 kg.

3. The high flexural strength pumpable C40 / 20 concrete for airport pavement according to claim 2, characterized in that, The P・O52.5 grade cement can be replaced with P・Ⅱ52.5 grade cement, and the cement dosage can be adjusted from 290 to 310 kg.

4. The high flexural strength pumpable C40 / 20 concrete for airport pavement according to claim 3, characterized in that, The Class I fly ash can be replaced with Class II fly ash. The fly ash dosage can be adjusted from 90 to 110 kg. The mass ratio of cement to fly ash should be maintained at 2.7:1 to 3.3:

1. The total mass of cementitious materials should be controlled at 390 to 410 kg.

5. The high flexural strength pumpable C40 / 20 concrete for airport pavement according to claim 4, characterized in that, The TY-J25 type polycarboxylate-based compound pumping admixture is replaced with a polycarboxylate-based pumping admixture with equivalent performance. The admixture dosage is adjusted within the range of 1.9% to 2.6%, and the concrete slump is maintained at 145 to 155 mm.

6. A method for preparing high flexural strength pumpable C40 / 20 concrete for airport pavement according to any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1, Raw material preparation: Accurately weigh each raw material according to the proportions; Step 2, mixing: Add P·O52.5 grade cement, grade I fly ash, mountain sand, and grade III crushed stone to a forced mixing equipment and dry mix for 2-3 minutes; then add tap water and TY-J25 type polycarboxylate compound pumpable admixture evenly to the mixing equipment and continue wet mixing for 3-4 minutes to obtain a uniform concrete mixture with a slump of 150mm. Step 3, Pumping and Pouring: The concrete mixture is transported by a concrete pump truck, and the pumping pressure is controlled at 10-15MPa. Continuous pumping is carried out, and an immersion vibrator is used to compact the mixture during the pouring process. Step 4, roughening treatment: After the concrete is poured and vibrated, before the initial setting of the concrete and within 2 hours after pouring, a comb-type roughening machine is used to roughen the surface. The roughening direction is perpendicular to the driving direction of the pavement. The spacing between the comb teeth of the roughening machine is 5-8mm, the depth of the comb teeth is 1.0-1.5mm, and the texture depth of the concrete surface after roughening is controlled at 0.7-1.2mm. Step 5, Moisturizing and Maintenance: Immediately after the texturing is completed, cover with geotextile for moisturizing and maintenance, which should last for no less than 10 days.

7. The method for preparing high flexural strength pumpable C40 / 20 concrete for airport pavement according to claim 6, characterized in that, In step 2, the dry mixing time is preferably 2.5 minutes, and the wet mixing time is preferably 3.5 minutes.

8. The method for preparing high flexural strength pumpable C40 / 20 concrete for airport pavement according to claim 6, characterized in that, In step 3, the preferred pumping pressure is 12 MPa, the pumping speed is 20 m³ / h, and the single-section continuous pumping distance is 50–80 m.

9. The method for preparing high flexural strength pumpable C40 / 20 concrete for airport pavement according to claim 6, characterized in that, In step 4, the roughening time is 1.5 hours after concrete pouring, the preferred spacing of the roughening machine comb teeth is 6mm, the preferred comb tooth depth is 1.2mm, and the preferred texture depth of the concrete surface after roughening is 1.0mm.

10. The method for preparing high flexural strength pumpable C40 / 20 concrete for airport pavement according to claim 6, characterized in that, In step 5, the maintenance period is 10 to 15 days, during which water is sprayed 2 to 3 times a day.

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