High-toughness waterproof self-repairing concrete, and preparation method and application thereof

Abstract

The application discloses a preparation and construction process of high-toughness waterproof self-repairing concrete for a sealing layer, and the high-toughness waterproof self-repairing concrete comprises fly ash, fine sand, an expanding agent, a repairing agent, heavy calcium powder, fibers, cellulose ether, dispersible latex powder, a water reducing agent, a hydrophobic agent, water and optional cement. The application further provides a construction process of applying the high-toughness waterproof self-repairing concrete to a sealing layer of a ballastless track of a high-speed railway. The application has the advantages that raw materials are simple and easy to obtain, the concrete has high toughness, high crack resistance, super waterproofness, self-repairing and the like, and the construction can be performed in a pumping mode, so that the construction is convenient.

Description

Technical Field

[0001] This invention relates to the field of waterproof sealing layer for ballastless tracks of high-speed railways, and specifically to the preparation and construction process of high-toughness waterproof self-healing concrete for sealing layers. Background Technology

[0002] With the rapid development of high-speed railways in my country, the ballastless track subgrade sealing layer effectively prevents rainwater intrusion, ensuring the strength and stability of the subgrade bed and the smoothness and durability of the track structure. Concrete, as the main sealing layer material, is prone to cracking during service due to its brittleness and drying shrinkage. To reduce the occurrence of waterproof sealing layer cracking failure caused by concrete shrinkage, expansion joints are typically installed every 4m-6m. However, in summer when temperatures are high, some of the sealing material melts and is squeezed out of the expansion joints. Similarly, in winter, cracking occurs when using asphalt-based caulking materials, leading to sealing material failure and loss of its sealing and waterproofing function. Water then enters the subgrade surface, creating dynamic hydraulic pressure under the repeated dynamic loads of high-speed trains, causing mud pumping and frost heave in the ballastless track bed or subgrade surface. Furthermore, the traditional sealing layer is located on the subgrade surface shoulder and between the track and the base plate, making the joint between them a weak point. To reduce the failure of waterproofing layers caused by expansion joints and seams, patent CN 215518173 U proposes a full-section waterproofing layer structure, which involves laying a waterproofing layer across the entire surface of the roadbed. This avoids problems such as joints between the base plate and the facade of structures, and uses fiber-reinforced concrete with an internal superhydrophobic agent as a rigid waterproofing layer. However, fiber-reinforced concrete still cracks during its service life. High-speed railways have short maintenance windows and short repair times, making passive repair difficult. Using active self-healing materials can save maintenance costs and repair internal cracks and micro-cracks. Therefore, developing a type of concrete for waterproofing layers that is highly tough, crack-resistant, waterproof, self-healing, easy to operate and construct, and low in cost is of great significance. Summary of the Invention

[0003] The purpose of this invention is to provide a high-toughness, high-crack-resistance, super-waterproof, self-healing concrete, its preparation method, and its construction process for application in the sealing layer of ballastless track of high-speed railways.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] In a first aspect, the present invention provides a high-toughness waterproof self-healing concrete, comprising fly ash, fine sand, an expanding agent, a repairing agent, heavy calcium carbonate powder, fiber, cellulose ether, dispersible latex powder, a water-reducing agent, a hydrophobic agent, water, and optionally cement.

[0006] In the concrete of this invention, the repair agent is a repair capsule. When the concrete cracks, the capsule wall ruptures, exposing the core material such as microorganisms or cement to the crack, forming inorganic salts or generating hydration products to fill the crack, thereby achieving the effect of repairing the crack.

[0007] In the concrete of this invention, the addition of fly ash can play a filling effect, a gradation effect and a later pozzolanic effect in the cement stone, which is beneficial to refine the pore structure of the cement stone in the later stage, improve the microstructure, and improve the mechanical strength and durability.

[0008] In the concrete of this invention, the addition of an expansive agent can reduce concrete shrinkage and the formation of cracks. Furthermore, the expansive agent reacts with water to generate crystals such as ettringite and calcium hydroxide, which can fill pores, improve early strength, and compensate for early shrinkage of concrete caused by changes in temperature and humidity. This inhibits early cracking of concrete while promoting better crack repair by the repair agent.

[0009] In the concrete of this invention, the addition of heavy calcium carbonate powder can increase the toughness and strength of the concrete while reducing production costs.

[0010] In the concrete of this invention, the addition of a hydrophobic agent can form a water droplet effect on the surface and inside of the concrete, and significantly reduce the water absorption and chloride ion diffusion coefficient of the concrete. Furthermore, the water-repelling effect of the hydrophobic agent stores water in the cracks, and the repair agent fully contacts the water in the cracks and reacts to generate hydration products that fill the cracks.

[0011] In the concrete of this invention, the incorporation of fibers, particularly polyvinyl alcohol fibers, results in high strength, high modulus, wear resistance, acid and alkali resistance, and good weather resistance, significantly improving the toughness and crack resistance of the concrete. The hydrophilicity of the polyvinyl alcohol fiber surface effectively limits crack propagation, leading to multiple cracks in the concrete matrix. These cracks are dense and narrow, having minimal impact on concrete durability. Furthermore, the narrow cracks provide a prerequisite for self-healing, offering stable grid support for self-healing.

[0012] In the concrete of this invention, the addition of dispersible latex powder can form a film inside the concrete to block the internal capillary pores, thereby increasing the toughness of the concrete and improving its impermeability.

[0013] In some embodiments, the concrete, by weight, comprises: 250-350 parts fly ash, 500-600 parts fine sand, 30-40 parts expansion agent, 50-100 parts repair agent, 200-300 parts heavy calcium carbonate powder, 10-20 parts fiber, 0.1-0.2 parts cellulose ether, 10-20 parts dispersible latex powder, 10-20 parts water-reducing agent, 10-20 parts hydrophobic agent, and 200-300 parts water, and optionally 500-600 parts cement.

[0014] In some embodiments, the concrete, by weight, comprises: 280-330 parts fly ash, 530-580 parts fine sand, 33-38 parts expansion agent, 65-90 parts repair agent, 230-280 parts heavy calcium carbonate powder, 13-18 parts fiber, 0.13-0.18 parts cellulose ether, 13-18 parts dispersible latex powder, 13-18 parts water-reducing agent, 13-18 parts hydrophobic agent, 230-280 parts water, and optionally 530-580 parts cement.

[0015] In some embodiments, the concrete, by weight, comprises: 290-310 parts fly ash, 540-560 parts fine sand, 34-36 parts expansion agent, 70-80 parts repair agent, 240-260 parts heavy calcium carbonate powder, 14-16 parts fiber, 0.14-0.16 parts cellulose ether, 14-16 parts dispersible latex powder, 14-16 parts water-reducing agent, 14-16 parts hydrophobic agent, 240-260 parts water, and optionally 540-560 parts cement.

[0016] In some embodiments, by weight, the concrete contains 250 parts, 270 parts, 290 parts, 310 parts, 330 parts, 350 parts, or any value between thereof. In some embodiments, by weight, the concrete contains 500 parts, 520 parts, 540 parts, 560 parts, 580 parts, 600 parts, or any value between thereof. In some embodiments, by weight, the concrete contains 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, 40 parts, or any value between thereof. In some embodiments, by weight, the concrete contains 50 parts, 60 parts, 70 parts, 80 parts, 90 parts, 100 parts, or any value between thereof. In some embodiments, by weight, the concrete contains 200 parts, 220 parts, 240 parts, 260 parts, 280 parts, 300 parts, or any value between thereof. In some embodiments, by weight, the concrete contains 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, or any value between thereof. In some embodiments, by weight, the concrete contains 0.1 parts, 0.12 parts, 0.14 parts, 0.16 parts, 0.18 parts, 0.2 parts, or any value between thereof. In some embodiments, by weight, the concrete contains 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, or any value between thereof. In some embodiments, by weight, the concrete contains 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, or any value between thereof. In some embodiments, by weight, the concrete contains 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, or any value between thereof. In some embodiments, by weight, the concrete contains 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, or any value between thereof. In some embodiments, the concrete contains, by weight, 200 parts, 220 parts, 240 parts, 260 parts, 280 parts, 300 parts, or any value between thereof. In some embodiments, the concrete contains, by weight, 500 parts, 520 parts, 540 parts, 560 parts, 580 parts, 600 parts, or any value between thereof.

[0017] In some embodiments, the fly ash is selected from type F fly ash.

[0018] In some embodiments, the fine sand is selected from natural fine sand, preferably, the fineness modulus of the fine sand is 1.6-2.2, and the mud content is ≤3wt%.

[0019] In some embodiments, the expanding agent is selected from one or more of calcium oxide type expanding agents, magnesium oxide type expanding agents, or calcium sulfoaluminate type expanding agents.

[0020] In some embodiments, the heavy calcium carbonate powder is selected from calcium carbonate powder. Preferably, the heavy calcium carbonate powder has a particle size of less than 0.045 mm and a calcium carbonate content of ≥98%. In some specific embodiments, the heavy calcium carbonate powder has a particle size of 0.035-0.045 mm.

[0021] In some embodiments, the fiber is selected from polyvinyl alcohol fibers. Preferably, the fiber diameter is 30-45 μm, for example, 30 μm, 32.5 μm, 35 μm, 37.5 μm, 40 μm, 42.5 μm, 45 μm, or any value between therewith. Preferably, the fiber length is 5-20 mm. In some embodiments, the fiber is selected from one or more fibers with lengths of 9 mm, 12 mm, and 18 mm.

[0022] In some embodiments, the cellulose ether is selected from one or more of hydroxypropyl methylcellulose, methylcellulose ether, and hydroxyethylcellulose ether.

[0023] In some embodiments, the water-reducing agent is selected from one or more of naphthalene-based water-reducing agents or polycarboxylate water-reducing agents. Preferably, the polycarboxylate water-reducing agent is a polyether-based polycarboxylate water-reducing agent.

[0024] In some embodiments, the hydrophobic agent is selected from silicone emulsion hydrophobic agents.

[0025] In some embodiments, the repair material is selected from repair capsules, preferably one or more of microbial capsules, inorganic repair capsules, or polymeric material repair capsules, and more preferably selected from cement particle microcapsules.

[0026] In some embodiments, the cement is selected from one or more of ordinary silicate cement, early-strength silicate cement, or sulfoaluminate cement.

[0027] In a second aspect, the present invention provides a method for preparing the concrete described in the first aspect, comprising mixing fly ash, fine sand, an expanding agent, a repairing agent, heavy calcium carbonate powder, fiber, cellulose ether, dispersible latex powder, a water-reducing agent, a hydrophobic agent, water, and optionally cement.

[0028] In some embodiments, the preparation method includes the following steps:

[0029] (1) Mix fly ash, fine sand, expansion agent, dispersible latex powder, heavy calcium carbonate powder, cellulose ether and optional cement. It is preferable to stir for 2-3 minutes and then stir evenly to obtain the first mixture.

[0030] (2) Dilute the hydrophobic agent, water-reducing agent and water at a ratio of 1:10-1:100 and add them to the first mixture. Then add water (excluding dilution water) according to the water-cement ratio and stir for 2-3 minutes to obtain the second mixture.

[0031] (3) While stirring the second mixture, add polyvinyl alcohol fibers evenly in multiple batches. Stirring is preferably done for 5 min-6 min to obtain the third mixture.

[0032] (4) Finally, add the repair agent to the third mixture and stir for 2-3 minutes to obtain the concrete of the mixed slurry.

[0033] In a third aspect, the present invention provides an on-site construction method for a waterproof sealing layer for ballastless track of a high-speed railway, which includes pouring the concrete described in the first aspect onto the sealing layer of the high-speed railway.

[0034] In some embodiments, the concrete is poured into the area to be poured for the ballastless track enclosure of a high-speed railway.

[0035] In some embodiments, the method further includes curing the poured concrete, preferably within 12 hours of pouring, and more preferably, the curing time is 28 days.

[0036] In some embodiments, the construction method includes the following steps:

[0037] Step 1: Place the concrete in a concrete mixer truck, continuously rotate and mix it, and transport it to the sealed layer area to be poured.

[0038] Step 2: Set transverse and longitudinal templates across the entire cross section of the graded crushed stone layer in the subgrade, and reserve expansion joints;

[0039] Step 3: Pour concrete into the area to be poured. After reaching the pouring height, vibrate the concrete and finish the surface after initial setting and before final setting.

[0040] Step 4: Roughen the sealed layer area below the base plate. Preferably, the roughening depth is 2-4mm.

[0041] Step 5: Curing of the concrete within 12 hours of pouring.

[0042] Preferably, in step 1, the dispersible latex powder, heavy calcium carbonate powder, repair agent, and cellulose ether are premixed to obtain dry powder 1. During stirring, cement, fly ash, expansion agent, and dry powder 1 are separately proportioned according to the mass of each component to obtain a mixture.

[0043] Preferably, in step 2, an expansion joint is set at a longitudinal interval of 15-20m, for example, 16.99m, between base plates, using polyethylene foam board as a transverse template and anchoring bars for fixation.

[0044] Preferably, in step 3, the pouring method can be pumping or pouring through a hopper, the vibration is performed using a plate vibrator, and the surface is finished manually.

[0045] Preferably, in step 4, the concrete can be roughened manually after final setting or mechanically after hardening.

[0046] Preferably, in step 5, the concrete is cured by sun-drying or by wetting the geotextile and then covering it with a plastic film for 28 days.

[0047] In a fourth aspect, the present invention provides the application of the concrete described in the first aspect, the concrete obtained by the preparation method described in the second aspect, or the construction method described in the third aspect in the sealing layer of a high-speed railway.

[0048] In some embodiments, the high-speed railway enclosure layer is a high-speed railway ballastless track enclosure layer.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] (1) The repair agent of the present invention is in capsule form. After concrete cracks, the capsule wall ruptures, and microorganisms or cement core material are exposed at the crack, forming inorganic salts or generating hydration products to fill the crack, thereby achieving the effect of repairing the crack.

[0051] (2) The concrete of the present invention incorporates polyvinyl alcohol fibers with high modulus and high tensile strength, which have a good bridging and limiting effect on cracks, and can significantly improve the toughness and crack resistance of concrete and reduce shrinkage. In addition, the addition of expansion agent and heavy calcium carbonate powder can reduce the heat of hydration in the early stage of concrete pouring while improving the toughness of concrete, and reduce the generation of early micro-cracks during large-volume pouring.

[0052] (3) The concrete of the present invention incorporates renewable latex powder, and the polymer film adheres to the cement hydration products and fills the pores and blocks the capillaries. The hydration products and the polymer form an interlocking network membrane structure. The good adhesion and ductility of the polymer and the active groups it has can improve the crack resistance and toughness of the network membrane structure and reduce the shrinkage value.

[0053] (4) The water-repellent agent added to the concrete of the present invention forms a water droplet effect on the concrete surface and inside, which has good waterproof effect and freeze-thaw resistance. Furthermore, by using the method of internal addition of water-repellent agent, the concrete as a whole is hydrophobically modified, which has a long-term waterproof effect and will not fail due to cracking or powdering of the surface concrete.

[0054] (5) Under the action of polyvinyl alcohol fibers, the concrete produces multiple cracks, which are fine and dense, providing a prerequisite for self-repair. Moreover, the hydrophobic effect of the hydrophobic agent causes the outer shell of the repair agent capsule at the crack to rupture, and the unhydrated cement in the core undergoes a hydration reaction with water to generate hydrated calcium silicate gel, calcium hydroxide and other hydration products to fill the crack.

[0055] (6) The present invention also provides a field construction process for high-toughness waterproof self-healing concrete for waterproof sealing layer of ballastless track of high-speed railway. The process of this construction process includes concrete preparation and curing. The construction process is simple and can be flexibly applied to various construction methods. Attached Figure Description

[0056] Figure 1 The load-displacement curves of the fiber-reinforced cementitious material in the performance test of this invention are shown.

[0057] Figure 2 The crack repair rates using Example 1, Comparative Example 1, and Comparative Example 2 are shown.

[0058] Figure 3 The results of crack repair using concrete from Example 1 are shown. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention in any way. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure. Such structures and techniques have also been described in many publications.

[0060] Raw materials used in the following examples:

[0061] The cement is ordinary Portland cement P·O 42.5;

[0062] The fly ash is Class F, Grade II ash provided by Beijing Ruierwei Technology Co., Ltd., with a particle size of 1-100μm;

[0063] The fine sand is single-graded dry natural river sand with a fineness modulus of 1.6-2.2 and a mud content of ≤3wt%, provided by Beijing Hengying Environmental Protection Technology Co., Ltd.

[0064] The expansive agent is ZY high-performance concrete expansive agent, a calcium sulfoaluminate concrete expansive agent;

[0065] Heavy calcium carbonate powder is heavy calcium carbonate. "Yinli" brand double-flying powder produced in Pengshui County, Chongqing, has a fineness of 0.038-0.045mm and a CaCO3 content of ≥98%.

[0066] The fiber used is polyvinyl alcohol fiber, with a diameter of 30-45μm and a length of 12mm;

[0067] The cellulose ether used is hydroxypropyl methylcellulose provided by Hebei Ruixin Kaimaoxing Cellulose Co., Ltd.

[0068] The hydrophobic agent is ZG-S70 type silane emulsion provided by Beijing Zhonggui Heju New Material Co., Ltd., with an active ingredient content of 47% octyltriethoxysilane;

[0069] The polycarboxylate superplasticizer is a polyether-based ultra-high-efficiency polycarboxylate superplasticizer, purchased from Beijing Zhonggui Heju New Materials Co., Ltd.

[0070] The repair agent is a repair capsule, the capsule wall is a mixture of epoxy resin and polyacrylamide, and the capsule core is unhydrated cement, purchased from Beijing Zhonggui Poly New Materials Co., Ltd.

[0071] The preparation process of the high-toughness waterproof self-healing concrete described in the following embodiments and comparative examples is as follows:

[0072] (1) After stirring cement, fly ash, fine sand, expansion agent, dispersible latex powder, heavy calcium carbonate powder and cellulose ether for 2 minutes, mix them evenly to obtain mixture 1;

[0073] (2) Dilute the hydrophobic agent and water at a ratio of 1:10 and add them to mixture 1. Then add water (excluding dilution water) according to the water-cement ratio and stir for 2 minutes to obtain mixture 2.

[0074] (3) While stirring mixture 2, add polyvinyl alcohol fiber evenly to mixture 2 in multiple batches. After stirring for 5 minutes, mixture 3 is obtained.

[0075] (4) Finally, add the repair agent to mixture 3 and stir for 2 minutes to obtain the mixed slurry.

[0076] Example 1

[0077] A high-toughness, waterproof, self-healing concrete for sealing layers, comprising the following components by weight:

[0078] 600 parts cement, 300 parts fly ash, 500 parts fine sand, 10 parts fiber, 30 parts expanding agent, 200 parts heavy calcium carbonate powder, 10 parts dispersible latex powder, 10 parts polyvinyl alcohol fiber, 50 parts repair agent, 0.1 parts cellulose ether, 10 parts water-reducing agent, 10 parts hydrophobic agent, and 300 parts water.

[0079] Example 2

[0080] A high-toughness, waterproof, self-healing concrete for sealing layers, comprising the following components by weight:

[0081] 600 parts cement, 300 parts fly ash, 5000 parts fine sand, 1 part fiber, 30 parts expanding agent, 200 parts heavy calcium carbonate powder, 10 parts dispersible latex powder, 50 parts repair agent, 0.15 parts cellulose ether, 15 parts water-reducing agent, 10 parts hydrophobic agent, and 200 parts water.

[0082] Example 3

[0083] A high-toughness, waterproof, self-healing concrete for sealing layers, comprising the following components by weight:

[0084] 600 parts cement, 300 parts fly ash, 500 parts fine sand, 20 parts fiber, 30 parts expanding agent, 200 parts heavy calcium carbonate powder, 10 parts dispersible latex powder, 50 parts repair agent, 0.1 parts cellulose ether, 12 parts water-reducing agent, 10 parts hydrophobic agent, and 300 parts water.

[0085] Example 4

[0086] A high-toughness, waterproof, self-healing concrete for sealing layers, comprising the following components by weight:

[0087] 600 parts cement, 300 parts fly ash, 500 parts fine sand, 10 parts fiber, 60 parts expansion agent, 170 parts heavy calcium carbonate powder, 10 parts dispersible latex powder, 50 parts repair agent, 0.1 parts cellulose ether, 10 parts water-reducing agent, 10 parts hydrophobic agent, and 300 parts water.

[0088] Example 5

[0089] A high-toughness, waterproof, self-healing concrete for sealing layers, comprising the following components by weight:

[0090] 500 parts cement, 300 parts fly ash, 500 parts fine sand, 10 parts fiber, 30 parts expanding agent, 300 parts heavy calcium carbonate powder, 10 parts dispersible latex powder, 50 parts repair agent, 0.1 parts cellulose ether, 10 parts water-reducing agent, 10 parts hydrophobic agent, and 300 parts water.

[0091] Example 6

[0092] A high-toughness, waterproof, self-healing concrete for sealing layers, comprising the following components by weight:

[0093] 580 parts cement, 300 parts fly ash, 500 parts fine sand, 1 part fiber, 30 parts expansion agent, 200 parts heavy calcium carbonate powder, 10 parts dispersible latex powder, 100 parts repair agent, 0.1 parts cellulose ether, 10 parts water-reducing agent, 10 parts hydrophobic agent, and 300 parts water.

[0094] Example 7

[0095] A high-toughness, waterproof, self-healing concrete for sealing layers, comprising the following components by weight:

[0096] 600 parts cement, 300 parts fly ash, 500 parts fine sand, 10 parts fiber, 30 parts expanding agent, 200 parts heavy calcium carbonate powder, 20 parts dispersible latex powder, 50 parts repair agent, 0.1 parts cellulose ether, 10 parts water-reducing agent, 10 parts hydrophobic agent, and 300 parts water.

[0097] Example 8

[0098] A high-toughness, waterproof, self-healing concrete for sealing layers, comprising the following components by weight:

[0099] 600 parts cement, 300 parts fly ash, 500 parts fine sand, 10 parts fiber, 30 parts expanding agent, 200 parts heavy calcium carbonate powder, 10 parts dispersible latex powder, 50 parts repair agent, 0.1 parts cellulose ether, 10 parts water-reducing agent, 20 parts hydrophobic agent, and 300 parts water.

[0100] Example 9

[0101] A high-toughness, waterproof, self-healing concrete for sealing layers, comprising the following components by weight:

[0102] 600 parts cement, 250 parts fly ash, 500 parts fine sand, 10 parts fiber, 30 parts expanding agent, 200 parts heavy calcium carbonate powder, 10 parts dispersible latex powder, 50 parts repair agent, 0.1 parts cellulose ether, 10 parts water-reducing agent, 10 parts hydrophobic agent, and 300 parts water.

[0103] Example 10

[0104] A high-toughness, waterproof, self-healing concrete for sealing layers, comprising the following components by weight:

[0105] 600 parts cement, 300 parts fly ash, 600 parts fine sand, 10 parts fiber, 30 parts expanding agent, 200 parts heavy calcium carbonate powder, 10 parts dispersible latex powder, 50 parts repair agent, 0.13 parts cellulose ether, 10 parts water-reducing agent, 10 parts hydrophobic agent, and 300 parts water.

[0106] Comparative Example 1

[0107] A high-toughness, waterproof, self-healing concrete for sealing layers, comprising the following components by weight:

[0108] 700 parts cement, 300 parts fly ash, 500 parts fine sand, 10 parts fiber, 30 parts expanding agent, 200 parts heavy calcium carbonate powder, 10 parts dispersible latex powder, 0 parts repair agent, 0.1 parts cellulose ether, 10 parts water-reducing agent, 10 parts hydrophobic agent, and 300 parts water.

[0109] Comparative Example 2

[0110] A high-toughness, waterproof, self-healing concrete for sealing layers, comprising the following components by weight:

[0111] 600 parts cement, 300 parts fly ash, 500 parts fine sand, 10 parts fiber, 30 parts expanding agent, 200 parts heavy calcium carbonate powder, 10 parts dispersible latex powder, 50 parts repair agent, 0.1 parts cellulose ether, 10 parts water-reducing agent, 0 parts hydrophobic agent, and 300 parts water.

[0112] The specific composition (number of parts) of the high-toughness waterproof self-healing concrete in each embodiment and comparative example is shown in Table 1.

[0113] Table 1

[0114]

[0115]

[0116] Performance testing:

[0117] Specimen preparation: The high-toughness waterproof self-healing concrete of the example and comparative proportions was prepared into prismatic specimens with a cross-sectional width of 40 mm and a height of 40 mm. After standard curing (20℃±3℃, relative humidity ≥95%) for 28 days, the following experiments were conducted.

[0118] Four-point bending toughness test: A WAW600 universal testing machine was used for four-point bending tests with a span of 150 mm and a loading rate of 0.2 mm / min. Three specimens were tested in each group of tests. The maximum bending load F can be read from the load-displacement curve obtained during the loading process. b and its corresponding displacement δ max ,like Figure 1 As shown, the bending toughness (Wu) of the specimen was calculated according to formula (1) and used to evaluate the bending performance of fiber-reinforced cementitious materials.

[0119]

[0120] In the formula, L is the span (mm); b and h are the specimen width and thickness (mm), respectively; Ω u 0.85F b2 The area under the load-displacement curve (N·mm).

[0121] Freeze-thaw resistance test: The freeze-thaw resistance test refers to the provisions of the "Test Procedure for Hydraulic Concrete" (DL / T 5150-2017) and the "Test Procedure for Polymer Modified Cement Mortar" (DL / T 5126-2001) for the freeze-thaw resistance test of cement mortar. The test uses 40mm×40mm×160mm specimens after standard curing for 28 days. The specimens are immersed in water 3 days before the 28-day curing period. After immersion, the surface moisture of the specimens is wiped off, the initial mass is weighed and photographed. Then, the mass of the specimens is measured every 15 cycles, and the necessary appearance description or photographs are made until 150 cycles are completed. The freeze-thaw resistance is judged by the mass loss rate and the appearance damage morphology. The mass loss rate of the specimen is considered to be damaged if it exceeds 5%. The mass loss rate of the specimen is calculated according to formula (2):

[0122]

[0123] In the formula: W n —Sample mass loss rate after n freeze-thaw cycles, %;

[0124] m0—Mass of the specimen before freeze-thaw cycle, m n —The mass of the specimen after n freeze-thaw cycles, in grams.

[0125] The 28-day flexural toughness, freeze-thaw cycle mass loss rate, 28-day compressive strength, and compressive strength after cracking and re-curing for 14 days are measured for each embodiment and comparative example of high-toughness self-healing concrete. The results are shown in Table 2 below.

[0126] Pre-compression repair test: The test blocks cured for 28 days were pre-compressed with a load of 60% of the 28-day failure load. The pre-compression location was marked, and the test blocks were placed in a standard curing room for 14 days before a compressive strength failure test was conducted.

[0127] Table 2

[0128]

[0129] Table 2 shows the experimental results:

[0130] Comparing Examples 2 and 1, increasing the water-cement ratio can improve compressive strength and reduce mass loss rate, but it also reduces flexural toughness, which is detrimental to improving toughness. Comparing Examples 3 and 1, increasing the fiber content is beneficial for further improving flexural toughness, but it is detrimental to freeze-thaw resistance and compressive strength. Comparing Examples 4 and 1, increasing the amount of expanding agent can also improve toughness and freeze-thaw resistance. Comparing Examples 5 and 1, increasing the amount of heavy calcium carbonate powder also improves flexural toughness, but it reduces freeze-thaw resistance. Comparing Examples 6 and 1, increasing... Adding a repair agent can improve the compressive strength recovery rate; comparing Example 7 and Example 1, increasing the amount of dispersible latex powder can improve flexural toughness and freeze-thaw resistance, but it will reduce compressive strength; comparing Example 8 and Example 1, increasing the amount of hydrophobic agent not only improves freeze-thaw resistance, but also increases flexural toughness and self-healing performance; comparing Example 9 and Example 1, reducing the amount of fly ash can improve compressive strength, but it will reduce flexural toughness; comparing Example 10 and Example 1, increasing the sand-to-binder ratio will reduce flexural toughness and freeze-thaw resistance. Comparing Comparative Example 1 and Example 1, without the repair agent, the compressive strength recovery rate of concrete is less than 1, while with the repair agent, the compressive strength recovery rate is greater than 1; comparing Comparative Example 2 and Example 1, it was found that adding a hydrophobic agent is beneficial to improving the efficiency of self-healing (see Comparative Example 2). Figure 2 ).

[0131] Crack Repair Observation: Prismatic specimens with a length of 160 mm, a cross-sectional width of 40 mm, and a height of 40 mm were prepared using Example 1 as the self-healing concrete and Comparative Example 1 and Comparative Example 2 as controls. After standard curing (temperature 20℃±3℃, relative humidity ≥95%) for 3 days, the following experiments were conducted. A four-point flexural loading method was used to slowly load the prismatic specimens at a loading rate of 0.2 mm / min until the peak load was reached. The specimens were then immersed in tap water, and the crack repair was observed using a stereomicroscope. Images were taken and stored using a JM2000 camera.

[0132] Depend on Figure 2 It can be seen that the repair rate increases continuously over time, with the repair rate ranking as follows: Example 1 > Comparative Example 2 > Comparative Example 1. This indicates that incorporating a repair agent is key to improving the repair rate, and incorporating a hydrophobic agent is also beneficial for improving the repair rate.

[0133] Depend on Figure 3 It can be seen that after one of the initial cracks, 117 μm wide, in the specimen of Example 1 was immersed in water for 14 days, the crack was basically completely healed. The crack filling material included cement particles in the repair capsule core that underwent a cement hydration reaction upon contact with water, generating hydration products that filled the crack; unhydrated cement particles in the matrix continued to hydrate and fill the crack; and calcium hydroxide in the matrix reacted with carbon dioxide in the air to form calcium carbonate.

[0134] The above description uses specific examples to illustrate the present invention and is not intended to limit the invention. Those skilled in the art can, based on the concept of the present invention, make simple deductions, modifications, or substitutions through creative effort. The scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A high-toughness, waterproof, self-healing concrete for sealing layers in high-speed railways, characterized in that, By weight, the concrete comprises: 250-350 parts fly ash, 500-600 parts fine sand, 30-40 parts expansion agent, 50-100 parts repair agent, 200-300 parts heavy calcium carbonate powder, 10-20 parts fiber, 0.1-0.2 parts cellulose ether, 10-20 parts dispersible latex powder, 10-20 parts water-reducing agent, 10-20 parts hydrophobic agent, 200-300 parts water, and 500-600 parts cement. The expanding agent is selected from one or more of calcium oxide type expanding agents, magnesium oxide type expanding agents, or calcium sulfoaluminate type expanding agents; The fiber is selected from polyvinyl alcohol fiber; The hydrophobic agent is selected from organosilicon emulsion hydrophobic agents; The repair agent is selected from cement particle microcapsules.

2. The concrete according to claim 1, characterized in that, By weight, the concrete comprises: 280-330 parts fly ash, 530-580 parts fine sand, 33-38 parts expansion agent, 65-90 parts repair agent, 230-280 parts heavy calcium carbonate powder, 13-18 parts fiber, 0.13-0.18 parts cellulose ether, 13-18 parts dispersible latex powder, 13-18 parts water-reducing agent, 13-18 parts hydrophobic agent, 230-280 parts water, and 530-580 parts cement.

3. The concrete according to claim 1, characterized in that, By weight, the concrete comprises: 290-310 parts fly ash, 540-560 parts fine sand, 34-36 parts expansion agent, 70-80 parts repair agent, 240-260 parts heavy calcium carbonate powder, 14-16 parts fiber, 0.14-0.16 parts cellulose ether, 14-16 parts dispersible latex powder, 14-16 parts water-reducing agent, 14-16 parts hydrophobic agent, 240-260 parts water, and 540-560 parts cement.

4. The concrete according to any one of claims 1-3, characterized in that, The fly ash is selected from Class F fly ash; and / or The fine sand is selected from natural fine sand; and / or The heavy calcium powder is selected from calcium carbonate powder; and / or The fibers are 5-20 mm in length and 30-45 μm in diameter; and / or The cellulose ether is selected from one or more of hydroxypropyl methylcellulose, methylcellulose ether, and hydroxyethyl cellulose ether; and / or The water-reducing agent is selected from one or more of naphthalene-based water-reducing agents or polycarboxylate water-reducing agents; and / or The cement is selected from one or more of ordinary silicate cement, early-strength silicate cement, or sulfoaluminate cement.

5. The concrete according to claim 4, characterized in that, The fine sand has a fineness modulus of 1.6-2.2 and a mud content ≤3wt%; and / or The heavy calcium carbonate powder has a particle size of less than 0.045 mm and a calcium carbonate content of ≥98%; and / or The polycarboxylate superplasticizer is a polyether-based polycarboxylate superplasticizer.

6. A method for preparing concrete according to any one of claims 1-5, comprising mixing fly ash, fine sand, expansion agent, repair agent, heavy calcium carbonate powder, fiber, cellulose ether, dispersible latex powder, water-reducing agent, hydrophobic agent, water and cement.

7. A construction method for a high-speed railway sealing layer, comprising pouring concrete according to any one of claims 1-5 onto the high-speed railway sealing layer.

8. The construction method according to claim 7, characterized in that, The concrete is poured into the area to be poured for the ballastless track enclosure layer of the high-speed railway.

9. The construction method according to claim 7 or 8, characterized in that, The method also includes curing the poured concrete.

10. The construction method according to claim 9, characterized in that, Curing should be carried out within 12 hours after the pouring is completed.

11. The construction method according to claim 9, characterized in that, The maintenance period is 28 days.

12. The application of the concrete according to any one of claims 1-5, or the concrete obtained by the preparation method according to claim 6, or the construction method according to any one of claims 7-11, in the sealing layer of a high-speed railway.

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