Jet type high-toughness fiber reinforced cement-based composite material and preparation method thereof

Abstract

The invention discloses a jet type high-toughness fiber reinforced cement-based composite material and a preparation method thereof, and belongs to the technical field of material preparation. The invention provides a jet type high-toughness fiber reinforced cement-based composite material, which is prepared from the following raw materials in parts by mass: 320 to 400 parts of coarse aggregate, 220 to 260 parts of fine aggregate, 90 to 110 parts of cement, 40 to 50 parts of water, 10 to 15 parts of modified fiber, 5 to 10 parts of zeolite powder, 5 to 10 parts of polymerizing agent, 4 to 7 parts of accelerator and 2 to 5 parts of water reducing agent. The chemical bonding force of the fiber and the concrete interface is improved, meanwhile, the mechanical property of a hydration product at the interface is improved, the dispersity of the fiber in the concrete is improved, and the stress transmission and dispersion capacity of the fiber is effectively enhanced, so that the mechanical property and durability of the fiber concrete are enhanced.

Description

Technical Field

[0001] The invention belongs to the technical field of material preparation, and in particular relates to a spray-type high-toughness fiber-reinforced cement-based composite material and a preparation method thereof. Background Art

[0002] Shotcrete is a construction method that uses a spraying machine and high pressure to transport the mixed materials in a certain proportion through a pipeline and a nozzle and spray them at high speed onto the sprayed surface to quickly (no more than 10 minutes) solidify and harden. The advantages of the concrete spraying construction method are fast construction speed and low requirements for the construction site environment (flatness, shape, etc.). Therefore, this construction method is often used in emergency operations, mine tunnel support, subway support, tunnel and culvert support, railway and highway slope treatment and other fields.

[0003] At present, the more commonly used construction processes are dry spraying and wet spraying. On this basis, through continuous engineering practice and research, new spraying concrete construction technologies such as fiber spraying concrete and cement-wrapped sand have been improved and developed, and research has been conducted from ordinary spraying concrete (mortar) to spraying high-performance / ultra-high-toughness fiber-reinforced cement-based composites (ECC / UHTCC) and spraying fiber geopolymers. However, steel fibers are not easy to disperse during the preparation of sprayed concrete, and due to their high rigidity, they are prone to peeling during the spraying construction process, especially during the construction of the arch in the tunnel, which leads to high rebound rate and concrete spalling of the sprayed concrete. Polypropylene fibers do not absorb water, are easy to agglomerate, and are difficult to mix with cement. They have poor dispersion in concrete, which is not conducive to forming a good fiber-concrete collective interface, and will cause problems such as pipe blockage or material failure to adhere to the structural surface. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a spray-type high-toughness fiber-reinforced cement-based composite material and a preparation method thereof, so as to solve the technical problems of poor dispersion of fibers in sprayed concrete and easy peeling of concrete.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: to provide a spray-type high-toughness fiber-reinforced cement-based composite material, the raw materials used include, by mass, 320-400 parts of coarse aggregate, 220-260 parts of fine aggregate, 90-110 parts of cement, 40-50 parts of water, 10-15 parts of modified fiber, 5-10 parts of zeolite powder, 5-10 parts of polymerizer, 4-7 parts of accelerator and 2-5 parts of water reducer.

[0006] On the basis of the above technical solution, the present invention can also be improved as follows:

[0007] Furthermore, the raw materials used include, by mass, 360 parts of coarse aggregate, 240 parts of fine aggregate, 100 parts of cement, 45 parts of water, 13 parts of modified fiber, 8 parts of zeolite powder, 8 parts of polymerizing agent, 5 parts of accelerating setting agent and 3 parts of water reducing agent.

[0008] The CaO in some unhydrated cement in concrete will generate Ca(OH)2 after it meets water in the later stage, which will easily cause the concrete volume to expand and generate internal stress. The present invention can promote the further transformation of cement hydration products by adding active mineral admixtures (zeolite powder), improve the strength, and can be used to replace a part of cement. The large amount of active SiO2 and Al2O3 contained can react with Ca(OH)2 and CaSO4 for secondary hydration to generate hydrated calcium silicate gel (CSH) and ettringite (AFt), making the cement stone structure more compact, and improving the compactness, compressive strength and durability of shotcrete. In addition, zeolite powder has a porous structure and can absorb water from cement paste. As hydration continues, the free water in the paste decreases, and the zeolite powder gradually releases zeolite water, which plays a role in self-maintenance.

[0009] Furthermore, the coarse aggregate is crushed stone; the fine aggregate is river sand and / or fly ash; and the cement is silicate cement.

[0010] Further, the addition amount of river sand and fly ash is 1-2:1-2.

[0011] Furthermore, the crushed stone is 3-10mm single-grain graded limestone crushed stone with an apparent density of 2800-3000kg / m 3 ; The fineness modulus of river sand is 2-3, and the apparent density is 2500-2700kg / m 3 , the mud content is 0.5-1%.

[0012] Further, the preparation process of the modified fiber is:

[0013] S1. Soak the fiber in an acid solution with a pH value of 3-5 for 1-2 hours, then rinse it, dry it at 45-55°C for 20-40 minutes, and finally add a modifier, react it at 100-120°C for 1-2 hours to obtain a fiber intermediate; the ratio of fiber, acid solution and modifier is 20-30g:150-250mL:1-2g;

[0014] S2. The fiber intermediate and a silane coupling agent solution with a mass fraction of 1-5wt% are uniformly mixed in a mass ratio of 15-25:2-3, and then reacted at 30-50°C for 2-5h, and finally dried at 90-150°C for 1-2h to obtain modified fiber.

[0015] The activity of the fiber surface is increased by acid treatment, and the activity of the fiber is further improved by thermal modification, which is beneficial to the subsequent bonding ability of the silane coupling agent with the fiber surface, thereby improving the overall improvement effect. The modified fiber increases its contact area with the concrete. The failure form of the concrete mixed with the modified fiber is mainly the pull-out of the fiber. The rough fiber surface allows the concrete to absorb more energy in the later destruction process, thereby achieving the purpose of toughening and realizing the change of concrete from brittle failure to tough failure.

[0016] Furthermore, the fiber is at least one of polyvinyl alcohol fiber, polyethylene fiber, polypropylene fiber and basalt fiber; the acid is sulfuric acid, hydrochloric acid or tannic acid; and the modifier is maleic anhydride grafted polypropylene, maleic anhydride grafted polyethylene or polyethylene glycol.

[0017] The modifier provides hydrophilic groups for the fibers, improving the defect of the fibers not absorbing water, thereby increasing the affinity with concrete.

[0018] Furthermore, the silane coupling agent used in the silane coupling agent solution is at least one of Si-69, KH902, KH570, KH560, KH550, KH151, A172, silicone anti-adhesive agent and tetraethyl orthosilicate.

[0019] KH902 silane coupling agent can enhance the antistatic ability between fibers and improve the dispersion of fibers in concrete. In addition, KH902 can soften fibers to a certain extent. After the fibers become soft, the loss of fibers during concrete mixing can be reduced (for example, too hard may cause them to be broken), and the spraying efficiency can also be improved. The active groups of KH560 silane coupling agent can form hydrogen bonds or covalent bonds with the fiber surface, and each unit group dehydrates and condenses with the Si-O main chain, spreads on the fiber surface and forms a continuous new surface layer, repairs, fills, and wraps the defects on the fiber surface, and reduces its own weak links. A172 silane coupling agent can react on the fiber surface to make the fiber surface hydrophobic, thereby improving the dispersion performance of the fiber itself, fundamentally improving the dispersion of the fiber in the concrete system, and reducing the agglomeration rate.

[0020] Furthermore, the specific drying process in S2 is: firstly, the fiber intermediate after the reaction is placed at 90-110°C for drying for 30-60min, then heated to 140-150°C at a rate of 1-3°C / min, and continued to dry for 30-60min, and finally naturally cooled to room temperature to obtain modified fiber.

[0021] Furthermore, the quick-setting agent is an aluminum sulfate-based alkali-free quick-setting agent; the water-reducing agent is a polycarboxylic acid-based water-reducing agent; and the polymerizing agent is a mixture of polyurethane, polyvinyl pyrrolidone and water in a mass ratio of 1-2:1-2:10-400.

[0022] The bonding force between particles in shotcrete mixture is very small, and the density and particle size of each component are also different. Due to the effects of water and self-weight, concrete is very easy to disperse and fall off the spray wall. The polymerizer contains a long-chain structure of high molecular compounds, which adsorbs fine particles onto the molecular chain, connects many particles together through the vertical and horizontal cross-sections between fine particles, and forms a stable network structure; and the surfactant in the polymerizer can change the potential on the surface of the particles, reducing the repulsion between particles and increasing the attraction between particles. As a result of the above two effects, it manifests as a cohesion effect on a macro scale, with almost no water seepage, which improves the viscosity of the mixture and enhances the anti-dispersion ability, thus playing a key role in reducing the rebound rate and dust rate of shotcrete.

[0023] Furthermore, the quick-setting agent is a mixture of aluminum sulfate, fluorosilicate, sodium aluminate, silica fume, solid alcohol amine and triisopropanolamine in a mass ratio of 50-80:3-7:3-7:6-10:2-5:1-3.

[0024] The present invention also discloses a method for preparing a spray-type high-toughness fiber-reinforced cement-based composite material, comprising the following steps:

[0025] S1. Spray the surface of the crushed stone with water, then add cement and mix evenly, and finally add the raw materials except water, and stir at a speed of 20-60r / min for 5-10min to obtain a dry mix;

[0026] S2. Evenly mix the dry mixture and the remaining water to obtain a spray-type high-toughness fiber-reinforced cement-based composite material.

[0027] The beneficial effects of the present invention are:

[0028] 1. The present invention improves the chemical bonding force of the fiber and concrete interface by modifying the fiber, and at the same time improves the mechanical properties of the hydration products at the interface, and improves the dispersion of the fiber in the concrete, effectively enhancing the fiber's ability to transfer and disperse stress, improving the deformation capacity of the fiber concrete, and increasing the total amount of energy absorbed when the fiber concrete is destroyed, thereby enhancing the mechanical and durability properties of the fiber concrete. In addition, the modification method of the present invention is simple, the raw material source is wide and the price is cheap, and it has good economy and ease of construction.

[0029] 2. The present invention improves the bonding force of shotcrete by adding an accelerating setting agent, balances the viscosity and workability of shotcrete, improves the dispersion effect of modified fibers and the anti-stripping performance during construction, and forms a dense structure after the shotcrete is constructed, thereby achieving the purpose of improving the anti-seepage and anti-compression performance of concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The change of water penetration resistance performance;

[0031] Figure 2 This is the change of anti-carbonization performance. DETAILED DESCRIPTION

[0032] The specific embodiments of the present invention are described below to facilitate the understanding of the present invention by those skilled in the art. If the specific conditions are not specified in the examples, the methods are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturers are not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

[0033] The crushed stone used in the following embodiments is 3-10 mm single-grain graded limestone crushed stone with an apparent density of 2800-3000 kg / m 3 ; The fineness modulus of river sand is 2-3, and the apparent density is 2500-2700kg / m 3 , mud content is 0.5-1%; fly ash is F class I fly ash; cement is silicate cement, purchased from Jinyu Cement Co., Ltd. and sold P·O42.5 grade ordinary silicate cement; polycarboxylic acid water reducer is YM-1 type water reducer, purchased from Tianjin Yueming Technology Development Co., Ltd.

[0034] Example 1

[0035] A spray-type high-toughness fiber-reinforced cement-based composite material, the raw materials used include, by weight: 360 parts of crushed stone, 160 parts of river sand, 80 parts of fly ash, 100 parts of cement, 45 parts of water, 13 parts of modified fiber, 8 parts of zeolite powder, 7 parts of polymerizing agent, 5 parts of accelerating agent and 3 parts of polycarboxylic acid water reducing agent;

[0036] The polymerizing agent is a mixture of polyurethane, polyvinyl pyrrolidone and water in a mass ratio of 1:1:100, and the accelerating setting agent is a mixture of aluminum sulfate, fluorosilicate, sodium aluminate, silica fume, solid alcoholamine and triisopropanolamine in a mass ratio of 65:5:5:8:3:2.

[0037] The preparation process of modified fiber is:

[0038] S1. Soak 25 g of polyvinyl alcohol fiber in 200 mL of sulfuric acid solution with a pH value of 4 for 1.5 h, then rinse with water, dry at 50 ° C for 30 min, and finally add 1.5 g of maleic anhydride grafted polypropylene, react at 110 ° C for 1.5 h to obtain a fiber intermediate;

[0039] S2. The fiber intermediate was mixed evenly with a KH902 solution with a mass fraction of 3wt% in a mass ratio of 10:1, and the reaction was carried out at 40°C for 3h. The fiber intermediate after the reaction was then dried at 100°C for 45min, then heated to 145°C at a rate of 2°C / min, and continued to be dried for 45min, and finally naturally cooled to room temperature to obtain modified fiber.

[0040] The present invention also discloses a method for preparing a spray-type high-toughness fiber-reinforced cement-based composite material, comprising the following steps:

[0041] S1. Spray the surface of the crushed stone with water, then add cement and mix evenly, and finally add the raw materials except water, and stir at a speed of 40r / min for 8min to obtain a dry mix;

[0042] S2. Stir the dry mix and the remaining water for 10 minutes to mix them evenly to obtain a spray-type high-toughness fiber-reinforced cement-based composite material.

[0043] Example 2

[0044] A spray-type high-toughness fiber-reinforced cement-based composite material, the raw materials used include, by weight: 320 parts of crushed stone, 160 parts of river sand, 100 parts of fly ash, 90 parts of cement, 50 parts of water, 15 parts of modified fiber, 5 parts of zeolite powder, 5 parts of polymerizing agent, 4 parts of accelerating agent and 2 parts of polycarboxylic acid water reducing agent;

[0045] Among them, the polymerizing agent is a mixture of polyurethane, polyvinyl pyrrolidone and water in a mass ratio of 1:1:200, and the accelerator is a mixture of aluminum sulfate, fluorosilicate, sodium aluminate, silica fume, solid alcoholamine and triisopropanolamine in a mass ratio of 50:7:7:6:2:3.

[0046] The preparation process of modified fiber is:

[0047] S1. Soak 20 g of polyethylene fiber in 250 mL of hydrochloric acid solution with a pH value of 5 for 2 h, then rinse with water, dry at 45 ° C for 40 min, and finally add 1 g of maleic anhydride grafted polyethylene, react at 120 ° C for 1 h to obtain a fiber intermediate;

[0048] S2. The fiber intermediate was mixed evenly with a 5wt% KH560 solution in a mass ratio of 5:1, and the mixture was reacted at 30°C for 5h. The fiber intermediate was then dried at 90°C for 60min, and then heated to 140°C at a rate of 1°C / min, and dried for 30min. Finally, the mixture was naturally cooled to room temperature to obtain modified fiber.

[0049] The present invention also discloses a method for preparing a spray-type high-toughness fiber-reinforced cement-based composite material, comprising the following steps:

[0050] S1. Spray the surface of the crushed stone with water, then add cement and mix evenly, and finally add the raw materials except water, and stir at a speed of 60r / min for 5min to obtain a dry mix;

[0051] S2. Stir the dry mix and the remaining water for 10 minutes to mix them evenly to obtain a spray-type high-toughness fiber-reinforced cement-based composite material.

[0052] Example 3

[0053] A spray-type high-toughness fiber-reinforced cement-based composite material, the raw materials used include, by weight: 400 parts of crushed stone, 220 parts of river sand, 110 parts of cement, 40 parts of water, 10 parts of modified fiber, 10 parts of zeolite powder, 10 parts of polymerizing agent, 7 parts of accelerating agent and 5 parts of polycarboxylic acid water reducing agent;

[0054] The polymerizing agent is a mixture of polyurethane, polyvinyl pyrrolidone and water in a mass ratio of 1:2:10, and the accelerating setting agent is a mixture of aluminum sulfate, fluorosilicate, sodium aluminate, silica fume, solid alcohol amine and triisopropanolamine in a mass ratio of 80:3:3:10:5:1.

[0055] The preparation process of modified fiber is:

[0056] S1. Soak 30 g of polypropylene fiber in 150 mL of tannic acid solution with a pH value of 3 for 1 hour, then rinse with water, dry at 55°C for 20 minutes, and finally add 2 g of polyethylene glycol and react at 100°C for 2 hours to obtain a fiber intermediate;

[0057] S2. The fiber intermediate and the A172 solution with a mass fraction of 1wt% are mixed uniformly in a mass ratio of 25:2, and the reaction is carried out at 50°C for 2h. Then, the fiber intermediate after the reaction is dried at 110°C for 30min, and then the temperature is increased to 150°C at a rate of 3°C / min, and the drying is continued for 60min. Finally, it is naturally cooled to room temperature to obtain modified fiber.

[0058] The present invention also discloses a method for preparing a spray-type high-toughness fiber-reinforced cement-based composite material, comprising the following steps:

[0059] S1. Spray the surface of the crushed stone with water, then add cement and mix evenly, and finally add the raw materials except water, and stir at a speed of 20r / min for 10min to obtain a dry mix;

[0060] S2. Stir the dry mix and the remaining water for 10 minutes to mix them evenly to obtain a spray-type high-toughness fiber-reinforced cement-based composite material.

[0061] Comparative Example 1

[0062] The difference between this comparative example and Example 1 is that the modified fiber is omitted, and the remaining components and the preparation process are the same as those of Example 1 to prepare a sprayable cement-based composite material.

[0063] Comparative Example 2

[0064] The difference between this comparative example and Example 1 is that step S1 in the process of preparing the modified fiber is omitted, and the remaining components and the preparation process are the same as those in Example 1, thereby obtaining a spray-type high-toughness fiber-reinforced cement-based composite material.

[0065] Comparative Example 3

[0066] The difference between this comparative example and Example 1 is that the polymerizing agent is omitted, and the remaining components and the preparation process are the same as those of Example 1, and a spray-type high-toughness fiber-reinforced cement-based composite material is prepared.

[0067] Comparative Example 4

[0068] The difference between this comparative example and Example 1 is that the accelerator is replaced by an alkaline accelerator (sodium silicate), and the remaining components and the preparation process are the same as those in Example 1, to prepare a spray-type high-toughness fiber-reinforced cement-based composite material.

[0069] Experimental Example 1 Mechanical Properties

[0070] 1. Slump

[0071] The cement-based composite materials obtained in Examples 1-3 and Comparative Examples 1-4 were subjected to slump tests. During the test, a slump cone with a top diameter of 100 mm, a bottom diameter of 200 mm, and a height of 300 mm was used. The specific process is as follows: According to the national standard GB / T 50080-2016, the performance test method of ordinary concrete mixtures, the concrete casting material is evenly loaded into the slump cone in three layers. For each layer of concrete casting material, a tamping rod is used to evenly insert and tamp 25 times in a spiral shape from the edge to the center. After tamping, the height of each layer of concrete casting material is about one-third of the height of the cone. After the top layer is inserted and tamped, the charging funnel is removed, the excess concrete material is scraped off, and the surface is smoothed along the cone mouth; after removing the concrete on the bottom plate of the cone edge, the slump cone is lifted vertically and steadily, and gently placed next to the sample. When the sample no longer collapses or the slump time reaches 30s, the slump value is measured.

[0072] 2. Compressive strength

[0073] The cement-based composite materials prepared in Examples 1-3 and Comparative Examples 1-4 were respectively poured into molds with a size of 100 mm×100 mm×100 mm, and compacted by vibrating on a vibration table. The specimens were sealed with plastic film, left to stand in an indoor environment for 1 day before demolding. The specimens were then placed in a standard curing room with a temperature of 18-22° C. and a relative humidity of more than 95% for curing to obtain concrete specimens AG.

[0074] The compressive strength performance of concrete specimen AG was tested. A cubic specimen with a side length of 100 mm was used during the test. The specific method is as follows: According to the national standard GB / T 50081-20021 Test method for mechanical properties of ordinary concrete, the concrete specimen was taken out from the curing site and a SHT4106 computer-controlled electro-hydraulic servo universal testing machine was used to test the compressive strength of the concrete samples after curing for 1 day, 7 days and 28 days.

[0075] 3. Rebound rate

[0076] The spraying process is as follows: the delivery pressure is 45Mpa and the delivery flow rate is 3m 3 / min, the spraying distance is 0.8m, and the spraying thickness is controlled at 12mm per layer. The rebound rate of shotcrete is tested according to the "Test Method for Rebound Rate of Shotcrete" JSCE-F563-2005. The rebound rate of concrete is measured by laying colored strips on the construction site of shotcrete and weighing the dropped concrete. The calculation formula is as follows:

[0077] Rebound rate (%) = mass of dropped concrete / total mass of shotcrete × 100%.

[0078] The slump, compressive strength and rebound rate data of the cement-based composite materials prepared in Examples 1-3 and Comparative Examples 1-4 are shown in Table 1.

[0079] Table 1 Slump, compressive strength and rebound data

[0080]

[0081] (1) It can be seen from Table 1 that the slump of the spray-type high-toughness fiber-reinforced cement-based composite concrete prepared by the present invention is 110.7-141.6 mm. The slump has a certain influence on the rebound rate. If the slump is too large or too small, the working pressure of the sprayer will increase, the spraying distance will be difficult to control, and the rebound rate will also increase. When the slump is controlled at about 124.8 mm, the rebound rate is relatively good.

[0082] (2) For shotcrete that plays a structural support role, its early strength and 28d strength are usually required to be relatively high, and the early strength is generally based on the 1d strength. Comparing the compressive strength data of Example 1 and Comparative Example 4, it can be seen that the strength of shotcrete mixed with alkali-free accelerator is higher than that of alkali-containing accelerator at the same age, and the later strength retention rate is high. The reason for this phenomenon is mainly that the alkali-free accelerator used in the present invention contains sufficient sulfate, which can control the hydration process of tricalcium aluminate and react with cement particles to generate a large amount of calcium aluminate. Although it will cause the concrete to lose fluidity quickly, it will not completely cover the surface of the cement particles. Therefore, the alkali-free accelerator has little effect on the later hydration degree of cement particles. The hydration products generated by the reaction of alkali accelerator with cement particles are mainly composed of hydrated calcium aluminate and monosulfide hydrated calcium sulfoaluminate, and contain a small amount of CSH gel. These hydration products are wrapped on the surface of cement particles and have good thermal stability, which affects the further hydration of cement particles, thereby affecting the later strength development of concrete. Alkali accelerator can quickly consume Ca in the cement slurry solution. 2+ With SO4 2- , which causes tricalcium aluminate to further hydrate to form lower soluble calcium aluminate hydrate and monosulfide calcium sulfoaluminate hydrate, hindering the dissolution of tricalcium silicate and inhibiting its further hydration.

[0083] Experimental Example 2 Durability

[0084] The survey results of hydraulic tunnel projects that have been built and are under construction show that the number of hydraulic tunnels with cracking and water seepage problems has reached 70%, of which the number of hydraulic tunnels with serious leakage has reached about 1 / 3. Therefore, it is of great engineering significance to study the water penetration resistance of shotcrete. Since the internal environment of hydraulic tunnels is relatively closed, the concentration of carbon dioxide and the temperature and humidity in the air are high, and the degree of carbonization of shotcrete is higher. Carbonization reduces the alkalinity inside the concrete and easily causes steel corrosion, thus affecting the stability of the overall structure of the hydraulic tunnel. The durability performance is carried out in accordance with the standard GB / T50082-2009 Test Method for Long-term Performance and Durability of Ordinary Concrete. The main test contents are water penetration resistance and carbonization resistance. The water penetration resistance is measured by the water seepage height method, and the shotcrete specimens are formed by the wet spraying process. The specific preparation method refers to Appendix B of JGJ / T372-2016 Technical Specification for Application of Shotcrete.

[0085] Figure 1The water seepage of concrete specimens prepared in Examples 1-3 and Comparative Examples 1-4 after 24 hours of constant pressure of 1.2 MPa. The water seepage height of Comparative Example 1 is higher than that of Example 1 because the lack of fiber will make the cement hydration product loose in structure, increase microcracks, and contain more harmful pores, thereby reducing the strength and durability. The water seepage height of Comparative Example 3 is higher than that of the specimen prepared in Example 1 because after the polymerizer is omitted in Comparative Example 3, the overall strength and density of the sprayed concrete system are not as good as those of the concrete system prepared in the present invention, resulting in reduced water penetration resistance.

[0086] Depend on Figure 2 It can be seen that the carbonization speed of different specimens is faster in the early stage of carbonization, and the speed slows down in the later stage of carbonization. The carbonization depth of different concrete specimens in the early stage of carbonization is not much different, and the difference becomes more obvious as the carbonization time increases. The porosity of the concrete specimen lacking modified fibers (Comparative Example 1) increases, and the density decreases, which is conducive to the diffusion of CO2, and the carbonization speed is therefore accelerated. The carbonization depths of Example 1 and Comparative Example 4 at the 28d carbonization age are 7.4mm and 19.2mm, respectively. The anti-carbonization performance of the alkali system is slightly worse than that of the alkali-free system, and the 28d carbonization depth is increased by 159.46%. On the one hand, it is attributed to the lack of its own strength and density, which leads to a faster early diffusion rate of CO2. On the other hand, the effective ingredients of the alkali accelerator generate a large amount of alkaline compounds such as calcium hydroxide during the hydration process, which increases the content of carbonizable substances.

Claims

1. A spray-type high-toughness fiber-reinforced cement-based composite material, characterized in that: The raw materials used include, by weight: 320-400 parts of coarse aggregate, 220-260 parts of fine aggregate, 90-110 parts of cement, 40-50 parts of water, 10-15 parts of modified fiber, 5-10 parts of zeolite powder, 5-10 parts of polymerizing agent, 4-7 parts of accelerating setting agent and 2-5 parts of water reducing agent.

2. The spray-type high-tenacity fiber-reinforced cement-based composite material according to claim 1, characterized in that: The raw materials used include, by mass, 360 parts of coarse aggregate, 240 parts of fine aggregate, 100 parts of cement, 45 parts of water, 13 parts of modified fiber, 8 parts of zeolite powder, 8 parts of polymerizing agent, 5 parts of accelerating setting agent and 3 parts of water reducing agent.

3. The spray-type high-tenacity fiber-reinforced cement-based composite material according to claim 1 or 2, characterized in that: The coarse aggregate is crushed stone; the fine aggregate is river sand and / or fly ash; and the cement is silicate cement.

4. The spray-type high-tenacity fiber-reinforced cement-based composite material according to claim 1 or 2, characterized in that: The preparation process of the modified fiber is as follows: S1. Soak the fiber in an acid solution with a pH value of 3-5 for 1-2 hours, then rinse it, dry it at 45-55°C for 20-40 minutes, and finally add a modifier, react it at 100-120°C for 1-2 hours to obtain a fiber intermediate; the ratio of the fiber, the acid solution and the modifier is 20-30g:150-250mL:1-2g; S2. The fiber intermediate and a silane coupling agent solution with a mass fraction of 1-5wt% are uniformly mixed in a mass ratio of 15-25:2-3, and then reacted at 30-50°C for 2-5h, and finally dried at 90-150°C for 1-2h to obtain modified fiber.

5. The spray-type high-tenacity fiber-reinforced cement-based composite material according to claim 4, characterized in that: The fiber is at least one of polyvinyl alcohol fiber, polyethylene fiber, polypropylene fiber and basalt fiber; the acid solution is sulfuric acid, hydrochloric acid or tannic acid; and the modifier is maleic anhydride grafted polypropylene, maleic anhydride grafted polyethylene or polyethylene glycol.

6. The spray-type high-tenacity fiber-reinforced cement-based composite material according to claim 4, characterized in that: The silane coupling agent used in the silane coupling agent solution is at least one of Si-69, KH902, KH570, KH560, KH550, KH151, A172, silicone anti-adhesion agent and tetraethyl orthosilicate.

7. The spray-type high-tenacity fiber-reinforced cement-based composite material according to claim 4, characterized in that: The specific drying process in S2 is: firstly drying the fiber intermediate after the reaction at 90-110°C for 30-60min, then heating to 140-150°C at a rate of 1-3°C / min, and continuing drying for 30-60min, and finally naturally cooling to room temperature to obtain modified fiber.

8. The spray-type high-tenacity fiber-reinforced cement-based composite material according to claim 1 or 2, characterized in that: The accelerator is an aluminum sulfate-based alkali-free accelerator; the water reducer is a polycarboxylic acid-based water reducer; and the polymerizer is a mixture of polyurethane, polyvinyl pyrrolidone and water in a mass ratio of 1-2:1-2:10-400.

9. The spray-type high-tenacity fiber-reinforced cement-based composite material according to claim 8, characterized in that: The accelerating setting agent is prepared by mixing aluminum sulfate, fluorosilicate, sodium aluminate, silica fume, solid alcohol amine and triisopropanolamine in a mass ratio of 50-80:3-7:3-7:6-10:2-5:1-3.

10. The method for preparing the spray-type high-tenacity fiber-reinforced cement-based composite material according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Spray the surface of the crushed stone with water, then add cement and mix evenly, and finally add the raw materials except water, and stir at a speed of 20-60r / min for 5-10min to obtain a dry mix; S2. Evenly mix the dry mixture and the remaining water to obtain a spray-type high-toughness fiber-reinforced cement-based composite material.

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