A kind of high-strength stable anti-cracking concrete and its preparation method and application
By using high-strength, stable crack-proof concrete, the problem of crack-prone bed plates with ball-free tracks is solved, the strength and "patter" resistance of the track-bed plates are improved, maintenance costs are reduced, and operational safety is ensured.
Patent Information
- Application Number
- CN202211104142.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-09-09
- Publication Date
- 2024-12-27
- Estimated Expiration
- 2042-09-09
AI Technical Summary
The CRTSⅠ double-block ball-free tracks are prone to cracks, resulting in reduced strength during operation and increased maintenance costs, affecting operational safety.
High-strength and stable crack-proof concrete, including cement, alkaline wood ash, fly ash, sand, gravel and water reducers, are prepared through specific mixing and calcining methods to form high-strength and non-crackable concrete for use in the roadbed board Production.
It significantly improves the strength and "patter" resistance of the track bed plate, reduces cracks and maintenance costs, and ensures operational safety and the quality of high-speed rail operations.
Smart Images
Figure CN116283115B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of building materials, and in particular to high-strength stable anti-cracking concrete and a preparation method and application thereof. Background Art
[0002] CRTSⅠ double-block ballastless track consists of rails, fasteners, sleepers and ballast slabs. The ballast slabs are usually made of cast-in-place C40 reinforced concrete, which is prone to cracks. During operation, due to the "beating" of high-speed trains, the cracks will continue to develop and extend, which not only reduces the concrete strength of the ballast slabs, but also increases the cost of repairing the cracks. Summary of the invention
[0003] The purpose of the present invention is to provide a high-strength stable anti-cracking concrete and a preparation method and application thereof. The high-strength stable anti-cracking concrete provided by the present invention has high strength, will not produce cracks or fissures when used, can improve the ability to resist "slapping" during operation, improve the quality of the roadbed plate, reduce maintenance costs, and ensure operational safety.
[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:
[0005] The invention provides a high-strength stable anti-cracking concrete, which comprises the following raw materials, measured by weight: 307-345 parts of cement, 30-45 parts of alkaline plant ash, 95 parts of fly ash, 705 parts of sand, 1058 parts of crushed stone, 157 parts of water, and 4.65-5.94 parts of admixture.
[0006] Preferably, the fineness of the alkaline wood ash is 9.0 wt % on a 45 μm square mesh sieve.
[0007] Preferably, the method for preparing the alkaline wood ash comprises: calcining alkaline agricultural waste to obtain alkaline wood ash; the calcination temperature is greater than 700°C.
[0008] Preferably, the alkaline agricultural waste is straw and / or husk of alkaline crops.
[0009] Preferably, the fly ash is Class F Grade II fly ash.
[0010] Preferably, the sand has a fineness of 0.1 to 5 mm, wherein 10 to 15 wt% of the sand has a fineness of 2 to 5 mm.
[0011] Preferably, the particle size of the crushed stone is 5 to 20 mm.
[0012] Preferably, the admixture is a water reducing agent.
[0013] The present invention provides a method for preparing the high-strength, stable and crack-resistant concrete described in the above technical solution, comprising the following steps:
[0014] High-strength, stable and crack-resistant concrete is obtained by mixing crushed stone, cement, fly ash, alkaline plant ash, sand, water and admixtures.
[0015] The present invention provides the use of the high-strength stable anti-cracking concrete described in the above technical solution or the high-strength stable anti-cracking concrete prepared by the preparation method described in the above technical solution in a double-block ballastless track slab.
[0016] The present invention provides a high-strength, stable and crack-resistant concrete. The present invention adopts alkaline wood ash to fill concrete, which can reduce the amount of cement. Compared with ordinary concrete, the present invention has low hydration heat during the solidification process, stable strength, and significantly reduced cracks and fissures, thereby improving the quality of the roadbed slab and the ability to resist "slapping" during operation, reducing maintenance costs during operation, and ensuring operational safety. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 This is a process flow chart for preparing high-strength, stable and crack-resistant concrete according to Example 1 of the present invention;
[0018] Figure 2 Picture of ballastless track slab prepared for application example. DETAILED DESCRIPTION
[0019] The invention provides a high-strength stable anti-cracking concrete, which comprises the following raw materials, measured by weight: 307-345 parts of cement, 30-45 parts of alkaline plant ash, 95 parts of fly ash, 705 parts of sand, 1058 parts of crushed stone, 157 parts of water, and 4.65-5.94 parts of admixture.
[0020] In parts by weight, the raw materials for preparing the high-strength stable anti-cracking concrete include 307 to 345 parts of cement, preferably 342 parts. In the present invention, the cement is preferably P·O 42.5 cement.
[0021] Based on the weight of the cement, the raw materials for preparing the high-strength stable anti-cracking concrete include 30 to 45 parts of alkaline plant ash, preferably 38 parts. In the present invention, the fineness of the alkaline plant ash is 9.0wt% of the residue on a 45μm square mesh sieve. In the present invention, the pH value of the aqueous dispersion of the alkaline plant ash is preferably 7.5 to 9; the concentration of the aqueous dispersion of the alkaline plant ash is preferably 5 to 7wt%.
[0022] In the present invention, the preparation method of alkaline plant ash preferably comprises: calcining alkaline agricultural waste to obtain alkaline plant ash; the calcination temperature is greater than 700° C. The present invention uses alkaline agricultural waste as raw materials to prepare alkaline plant ash, effectively utilizes waste materials, thereby reducing environmental pollution caused by farmland burning, and plays a role in energy conservation and emission reduction.
[0023] In the present invention, the alkaline agricultural waste is preferably the straw and / or husk of alkaline crops; the alkaline crops preferably include one or more of rice, cereals, wheat, buckwheat and corn, and are specifically preferably one or more of rice straw, rice husk, corn stalks, corn cobs, sesame stalks, buckwheat stalks and buckwheat husks. In the present invention, the calcination is preferably carried out under oxygen-free conditions; the calcination temperature is preferably 700-900°C. In the present invention, the calcination time is preferably 2-3h. In the present invention, the calcination is preferably carried out in a dedicated anaerobic furnace. The present invention adopts the above calcination temperature to obtain crystalline silica fume with low carbon content. In the present invention, the density of the alkaline plant ash is much lower than that of cement. Using 10.0% alkaline plant ash in concrete can control the density of the concrete to be reduced by 2.0% on average.
[0024] Based on the weight percentage of the cement, the raw materials for preparing the high-strength, stable and crack-resistant concrete include 95 parts of fly ash. In the present invention, the fly ash is preferably Class F Grade II fly ash, and specifically preferably Class F Grade II fly ash from Xiangyang Power Plant. In the present invention, the total content of silicon dioxide, aluminum oxide and iron oxide in the fly ash is preferably 85wt%; the chloride ion content is preferably 0.004wt%; the sulfur trioxide content is preferably 1.5wt%; the calcium oxide content is preferably 6wt%; the alkali content is preferably 1.73wt%; the fineness of the fly ash is preferably 9.8wt% on a 45μm square hole sieve; and the activity index of the fly ash is preferably 74%.
[0025] In the present invention, fly ash can improve the particle gradation of the cementitious material system, reduce the porosity, and release the "filling water" between cement particles; fly ash contains a large amount of spherical glass, which plays a "ball, bearing" lubrication effect and reduces the friction between particles; the activity of fly ash is much lower than that of cement, which can reduce the slump loss of concrete; the adsorption of high-quality fly ash on admixtures is lower than that of cement, and the use of high-quality fly ash is equivalent to increasing the amount of admixtures, and the initial slump and retention capacity of concrete are improved. The density of fly ash is less than that of cement. After replacing cement in equal amounts, the amount of slurry in concrete increases, the cohesiveness of concrete is improved, the anti-segregation ability is improved, and water seepage is reduced. Fly ash can greatly improve the working performance of concrete, make concrete have better fluidity, density, homogeneity, and facilitate the construction of concrete. Fly ash and cement hydration products undergo secondary hydration, and the early strength will be reduced. As the secondary hydration proceeds, the later strength increases rapidly, and the mid-to-late stage will reach or even exceed the concrete without fly ash. The present invention uses fly ash to replace part of cement, reduces the water-cement ratio or increases the amount of fly ash while keeping the water-cement ratio unchanged, so as to improve the anti-permeability of concrete. The early carbonization depth value of fly ash concrete increases rapidly, and the later growth of carbonization depth is relatively slow.
[0026] Based on the weight of the cement, the raw materials for preparing the high-strength, stable and crack-resistant concrete include 705 parts of sand. In the present invention, the fineness of the sand is 0.1-5 mm, of which 10-15wt% of the sand has a fineness of 2-5 mm. In the present invention, the sand is preferably Tangbai River sand. In the present invention, the quartz content of the sand is preferably 80-85wt%, the feldspar content is preferably 10-15wt%, and the total content of biotite and muscovite is preferably 2-3wt%. In the present invention, the mud content of the Tangbai River sand is preferably 0.5wt%. The present invention uses the above-mentioned sand and 5-20mm crushed stone to form a good gradation.
[0027] Based on the weight of the cement, the raw materials for preparing the high-strength stable anti-cracking concrete include 1058 parts of crushed stone. In the present invention, the particle size of the crushed stone is preferably 5 to 20 mm.
[0028] Based on the weight of the cement, the raw materials for preparing the high-strength stable anti-cracking concrete include 157 parts of water. In the present invention, the water is preferably groundwater.
[0029] Based on the weight of the cement, the raw materials for preparing the high-strength, stable and crack-resistant concrete include 4.65 to 5.94 parts of admixtures, preferably 4.75 parts. In the present invention, the admixture is preferably a water reducer. In the present invention, the water reducer is preferably a polycarboxylic acid high-efficiency water reducer, more preferably an HPCSC-S-7 water reducer. In the present invention, the water reduction rate of the water reducer is preferably 28% (greater than the standard 25%); the 7d compressive strength ratio is preferably 151% (greater than the standard 140%); the 28d compressive strength ratio is preferably 145% (greater than the standard 140%); the slump 1h change (pumped concrete) is preferably 40mm (less than the standard 60mm); the alkali content of the water reducer is preferably 4.78 (less than the standard 10); the setting time is greater than 100min (greater than the standard 90min).
[0030] In the present invention, the water reducer has a strong dispersing effect on cement, can greatly improve the fluidity of cement mixture and the slump of concrete, and at the same time greatly reduce the water consumption, significantly improve the workability of concrete; can greatly reduce the water consumption and thus significantly improve the strength of concrete at all ages. While keeping the strength constant, it can save 10% of cement or more. In the present invention, the chloride ion content in the water reducer is very small, does not produce rust effect on steel bars, can enhance the anti-seepage, anti-freeze and thaw and corrosion resistance of concrete, and improve the durability of concrete.
[0031] The present invention provides a method for preparing the high-strength, stable and crack-resistant concrete described in the above technical solution, comprising the following steps:
[0032] High-strength, stable and crack-resistant concrete is obtained by mixing crushed stone, cement, fly ash, alkaline plant ash, sand, water and admixtures.
[0033] In the present invention, the specific order of mixing is preferably: mixing crushed stone, cement and fly ash to obtain a first dry mix; mixing the first dry mix with alkaline wood ash and sand to obtain a second dry mix; mixing the second dry mix with water and an admixture to obtain high-strength, stable and crack-resistant concrete.
[0034] The invention puts in coarse aggregate first and then fine aggregate, which is easy to fully mix and improves the workability of concrete.
[0035] The present invention provides the application of the high-strength stable anti-cracking concrete described in the above technical solution or the high-strength stable anti-cracking concrete prepared by the preparation method described in the above technical solution in the double-block ballastless track ballast plate. The present invention can improve the strength of concrete, reduce the maintenance workload and maintenance costs during the operation of high-speed railways, and ensure the use function of concrete; the present invention uses alkaline plant ash to fill concrete, which can reduce the hydration heat, significantly reduce the cracks in the ballast plate, greatly reduce the cost of crack repair, improve the quality of ballastless track, and also ensure the safety of high-speed railway operation.
[0036] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0037] Example 1
[0038] use Figure 1 The process of preparing high-strength, stable and crack-resistant concrete:
[0039] The rice straw, corn cob core and wheat straw were anaerobically calcined at 800℃ in a special closed large iron furnace for 3 hours to obtain alkaline wood ash;
[0040] Mix crushed stone, cement and fly ash to obtain a first dry mix; mix the first dry mix with alkaline wood ash and sand to obtain a second dry mix; mix the second dry mix with water and a water reducer to obtain high-strength, stable and crack-resistant concrete. The specifications and amounts of each raw material are shown in Table 1.
[0041] Table 1 Preparation materials of Example 1
[0042]
[0043] The high-strength, stable and crack-resistant concrete prepared in this embodiment has an average compressive strength of 40.8 MPa after 7 days, an average compressive strength of 45.1 MPa after 28 days, and an average compressive strength of 46.9 MPa after 90 days.
[0044] Comparative Example 1
[0045] Mix crushed stone, cement and fly ash to obtain a first dry mix; mix the first dry mix and sand to obtain a second dry mix; mix the second dry mix, water and a water reducing agent to obtain C40 reinforced concrete. The specifications and amounts of each raw material are shown in Table 2.
[0046] Table 2 Preparation materials of comparative example 1
[0047]
[0048] The average compressive strength of the C40 reinforced concrete prepared in this comparative example was 40.2 MPa after 7 days, 42.1 MPa after 28 days, and 43.5 MPa after 90 days.
[0049] This comparative example requires a large amount of cement as a binder when preparing concrete. The use of too much cement binder leads to many disadvantages in the performance of high-performance concrete. Due to the reaction between cement and water, concrete with a high cement content releases a large amount of hydration heat per unit volume. Each kilogram of cement added to concrete releases about 150kJ of heat. When the amount of cement increases, the temperature will increase significantly. This phenomenon is more obvious in large-volume concrete. This is the main reason for cracks in the concrete under high temperature conditions, especially in the early stage. In order to reduce concrete cracks, concrete maintenance must be strengthened, but the maintenance of concrete increases the total cost of concrete. In addition, the use of a large amount of cement in concrete leads to a large amount of self-calcium hydroxide compounds in the cement slurry, resulting in unstable volume of concrete and decreased water resistance of concrete. The use of this concrete to prepare the roadbed slab is likely to cause the roadbed slab to be insufficient in strength and crack resistance. There are many cracks in the roadbed slab in the later stage, especially many long through cracks.
[0050] It can be seen from the test results of the embodiment and the comparative example that the compressive strength of the 7-day-old cement was not different when alkaline plant ash was used to replace cement, but the embodiment was significantly improved compared with the comparative example at 28 days and 90 days, which increased by 6.5% and 7.5% respectively, and the compressive strength increase rate tended to increase continuously.
[0051] The present invention adopts alkaline wood ash with lower weight to fill concrete. When the alkaline wood ash replaces 10% of cement, the compressive strength of the concrete can meet the requirements. High-quality alkaline wood ash can be used as volcanic ash to be added to concrete to manufacture high-performance concrete. Using 10% alkaline wood ash to replace cement can greatly improve the properties of concrete, especially: compressive strength, water and chloride ion resistance.
[0052] Application Examples
[0053] A 1km section was selected as a test section at the Kongjiafan No. 1 double-track super-large bridge, and the high-strength, stable and crack-resistant concrete of Example 1 was used to prepare the ballastless track bed slab.
[0054] The time period of the day when the temperature change is the smallest from the beginning of concrete pouring to the final setting is selected, and the temperature change does not exceed 15℃. Concrete is mixed centrally, transported to the site by tank trucks, and pumped by car pumps or hoisted into the mold by crane hoppers; concrete is poured to the design elevation at one time, and the material needs to be laid continuously from one side of the sleeper to the other side. When the concrete automatically roams from under the sleeper to the next sleeper, it can be moved forward to the next sleeper to continue pouring; concrete tamping is done by manual hand-held vibrators, and the tamping is done synchronously along both sides of the rails. In particular, the tamping at the bottom of the sleeper should be strengthened to ensure that the concrete is dense. When the concrete enters the ballast bed, measures should be taken to avoid impact on the rails. During the tamping process, it is strictly forbidden to collide with the rail frame, sleepers, formwork, steel bars, etc. During the pouring process, the slump, mold temperature, air content and other indicators of the concrete are sampled as required to ensure that they meet the requirements of the specifications; the mold temperature of the concrete is controlled in the range of 5 to 30℃, and concrete specimens are retained as required by the specifications, and relevant records are kept.
[0055] After the concrete is vibrated for a certain length, the sleepers, fasteners and covers on the rails are promptly removed, and the cement slurry is cleaned to ensure the track is clean. The top surface of the ballast slab concrete is manually smoothed according to the designed slope, and the smoothing is carried out in three times. The first smoothing is to use a wooden trowel to complete the rough leveling in time after the concrete is vibrated into the mold. The second is to use a steel trowel to finely level the concrete surface. The third is to repeatedly calender the surface before the concrete begins to set. In order to prevent the concrete surface from losing water and producing fine cracks, it is strictly forbidden to sprinkle water to moisten the surface during the smoothing process, and excessive operation should be prevented from affecting the quality of the surface concrete. During the smoothing process, attention should be paid to strengthening the operation of the lower part of the tray and around the sleepers.
[0056] After the initial setting of the concrete (the specific time is determined by the tester based on the test results and notified to the on-site foreman), loosen the support bolts by 1 / 4 to 1 / 2 turn, and at the same time loosen the fasteners and fishplate bolts to prevent the expansion and contraction of the rails when the temperature changes and cause damage to the concrete. The picture of the ballastless track slab is as follows: Figure 2 shown.
[0057] After testing the concrete strength after 28 days, the average value was 44.7MPa, which met the design requirements. The cracks of the roadbed slab were observed after 28 days and 90 days, showing only a few small superficial cracks. Compared with C40 concrete, the concrete strength was increased by about 10%, the hydration heat was reduced, the larger and larger cracks of the roadbed slab were eliminated, and the small cracks of the roadbed slab were reduced by 50-70%. This shows that the present invention can improve the concrete strength, reduce cracks and cracks, ensure the quality of ballastless track, and reduce the cost of crack repair and the maintenance cost of high-speed rail operation.
[0058] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.
Claims
1. The application of high-strength stable anti-cracking concrete in the double-block ballastless track slab is characterized by: The high-strength stable anti-cracking concrete includes the following raw materials, by weight: 307-345 parts of cement, 30-45 parts of alkaline plant ash, 95 parts of fly ash, 705 parts of sand, 1058 parts of crushed stone, 157 parts of water, and 4.65-5.94 parts of admixture; The cement is P·O42.5 cement; The fineness of the alkaline plant ash is 9.0wt% on a 45μm square mesh sieve; The fineness of the sand is 0.1-5 mm, of which 10-15 wt% of the sand has a fineness of 2-5 mm; The particle size of the crushed stone is 5-20 mm; The fineness of the fly ash is 9.8wt% on a 45μm square mesh sieve; The preparation method of the alkaline plant ash comprises: calcining alkaline agricultural waste to obtain alkaline plant ash; the calcination temperature is greater than 700°C; The calcination is carried out under oxygen exclusion conditions.
2. The use according to claim 1, characterized in that: The alkaline agricultural waste is straw and / or husk of alkaline crops.
3. The use according to claim 1, characterized in that: The fly ash is Class F fly ash.
4. The use according to claim 1, characterized in that: The admixture is a water reducing agent.
5. The use according to claim 1, characterized in that: The method for preparing the high-strength stable anti-cracking concrete comprises the following steps: High-strength, stable and crack-resistant concrete is obtained by mixing crushed stone, cement, fly ash, alkaline plant ash, sand, water and admixtures.