A lightweight sprayed engineering cement-based composite material, its preparation method and application

Abstract

This invention belongs to the field of civil engineering materials technology, specifically relating to a lightweight sprayed engineering cement-based composite material, its preparation method, and its application. The lightweight sprayed engineering cement-based composite material comprises the following components: cement, fly ash, silica fume, hollow fly ash microspheres, water, organic fibers, water-reducing agent, and thickener. By optimizing the raw material ratio, this invention not only significantly reduces the density of the sprayed ECC, achieving material lightweighting, but also greatly improves the material's flowability, adhesion, and mechanical properties. It solves the problems of poor adhesion, high rebound rate, and limited spray thickness inherent in traditional sprayed ECC, exhibiting a lower rebound rate and a larger spray thickness during the spraying process, thus providing a high-performance lightweight sprayed engineering cement-based composite material for engineering applications.

Description

Technical Field

[0001] This invention belongs to the field of civil engineering materials technology, specifically relating to a lightweight sprayed cement-based composite material, its preparation method, and its application. Background Technology

[0002] Engineering cement-based composites (ECCs) are cement-based composite materials with ultra-high ductility, achieving an ultimate tensile strain of over 3% under uniaxial loads and exhibiting excellent strain hardening properties. However, traditional casting processes suffer from drawbacks such as long construction periods and the need for formwork, limiting their widespread application in engineering projects. Sprayed ECC technology, by applying ECC material to the substrate surface in a sprayed form, not only overcomes the shortcomings of traditional cast ECC but also improves construction efficiency. However, traditional sprayed ECC suffers from poor adhesion, high rebound rate, and limited spray thickness. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a lightweight sprayed engineering cement-based composite material, its preparation method and application, which has excellent adhesion and mechanical properties, and exhibits low rebound rate and large spray thickness during the spraying process.

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

[0005] This invention provides a lightweight sprayed engineering cement-based composite material, comprising the following components by weight:

[0006] 210-600 parts cement, 100-700 parts fly ash, 70-100 parts silica fume, 110-385 parts hollow fly ash microspheres, 255-316 parts water, 15-20 parts organic fiber, 3.5-6 parts water-reducing agent, and 0.3-0.4 parts thickener.

[0007] Preferably, the cement is OPC type 525 ordinary Portland cement.

[0008] Preferably, the fly ash is Grade I fly ash.

[0009] Preferably, the particle size of the hollow fly ash microspheres is 1–300 μm.

[0010] Preferably, the organic fiber comprises polyethylene fiber; the length of the organic fiber comprises 6 mm and 12 mm.

[0011] Preferably, the water-reducing agent is a polycarboxylate high-efficiency water-reducing agent.

[0012] Preferably, the thickener comprises hydroxypropyl methylcellulose.

[0013] This invention also provides a method for preparing the lightweight sprayed engineering cement-based composite material described in the above technical solution, comprising the following steps:

[0014] Cement, fly ash, silica fume, and hollow fly ash microspheres are first mixed to obtain a dry powder mixture;

[0015] The dry powder mixture, a portion of water, and a portion of water-reducing agent are mixed in a second mixture. Then, the remaining water, the remaining water-reducing agent, and the thickener are added in a third mixture. Finally, organic fibers are added for dispersion to obtain the lightweight sprayed engineering cement-based composite material.

[0016] The present invention also provides the application of the lightweight sprayed engineering cement-based composite material described in the above technical solution or the lightweight sprayed engineering cement-based composite material prepared by the preparation method described in the above technical solution in building construction.

[0017] Preferably, the application method includes:

[0018] After the lightweight sprayed engineering cement-based composite material is sprayed onto the substrate surface, it is cured.

[0019] The nozzle used for the spray has a diameter of 6-10 mm; the airflow pressure of the spray is 0.6-1 MPa; the spray thickness is ≤25 mm; and the spray is a layered spray.

[0020] This invention provides a lightweight sprayed engineering cement-based composite material, comprising the following components by weight:

[0021] 210-600 parts cement, 100-700 parts fly ash, 70-100 parts silica fume, 110-385 parts hollow fly ash microspheres, 255-316 parts water, 15-20 parts organic fiber, 3.5-6 parts water-reducing agent, and 0.3-0.4 parts thickener.

[0022] This invention significantly reduces the density of sprayed ECC by adding hollow fly ash microspheres (FAC), making it meet the density requirement of less than 1950 kg / m³ in the "Technical Specification for Lightweight Aggregate Concrete" JGJ-51-2002. 3 To meet the requirements of lightweight concrete, this material achieves lightweighting and significantly improves its fluidity, adhesion, and mechanical properties (tensile strength). It solves the problems of poor adhesion, high rebound rate, and limited spraying thickness of traditional sprayed ECC. During the spraying process, it exhibits a low rebound rate and a large spraying thickness, providing a high-performance lightweight sprayed engineering cement-based composite material for engineering applications. Attached Figure Description

[0023] Figure 1 A schematic diagram illustrating the spraying principle of lightweight sprayed cement-based composite materials;

[0024] Figure 2 A diagram showing the density testing method;

[0025] Figure 3 This is a diagram of a cube compression test.

[0026] Figure 4 Diagram of the tensile testing apparatus;

[0027] Figure 5 This is a test diagram for a four-point bending test;

[0028] Figure 6 The images show the spraying morphology and spraying thickness of the lightweight sprayed engineering cement-based composite materials prepared in Examples 1-3.

[0029] Figure 7 The images show the spraying morphology and spraying thickness of the lightweight sprayed engineering cement-based composite materials prepared in Examples 4-6.

[0030] Figure 8 The image shows the floatability test results of the lightweight sprayed engineering cement-based composite material prepared in Example 6. Detailed Implementation

[0031] This invention provides a lightweight sprayed engineering cement-based composite material, comprising the following components by weight:

[0032] 210-600 parts cement, 100-700 parts fly ash, 70-100 parts silica fume, 110-385 parts hollow fly ash microspheres, 255-316 parts water, 15-20 parts organic fiber, 3.5-6 parts water-reducing agent, and 0.3-0.4 parts thickener.

[0033] Unless otherwise specified, the present invention does not have special requirements on the source of raw materials used, and commercially available products well known to those skilled in the art can be used.

[0034] The lightweight sprayed engineering cement-based composite material provided by this invention comprises 210 to 600 parts by weight of cement, preferably 300 to 600 parts. In this invention, the cement is preferably OPC type 525 ordinary Portland cement.

[0035] Based on 1 part by weight of cement, the lightweight sprayed engineering cement-based composite material provided by this invention comprises 100 to 700 parts by weight of fly ash, preferably 200 to 420 parts by weight. In this invention, the fly ash is preferably Grade I fly ash; the particle size of the fly ash is preferably 1 to 100 μm, more preferably 10 to 50 μm; the specific surface area of ​​the fly ash is preferably 200 to 500 cm². 2 / g, more preferably 300-400cm 2 / g, with a density preferably between 2.1 and 2.6 g / cm³.3 .

[0036] Fly ash typically has a low density (2.1–2.6 g / cm³). 3 Compared to ordinary Portland cement (3.1~3.2g / cm³), 3 It is much lighter. Therefore, using fly ash can reduce the overall density of materials, thus achieving a lightweight effect. The fine and spherical particles of fly ash can act as a lubricant, reducing the viscosity of the mixture and significantly improving its fluidity. This helps to make pumping and pouring easier during construction, reducing construction difficulty and time. Fly ash can improve the adhesion properties of materials because its fine particles can fill the pores in the cement matrix, increasing the density and bonding strength of the material. For shotcrete, good adhesion properties can ensure that the material adheres better to the substrate, reducing the possibility of detachment and cracking. The active components of fly ash (such as silicates and aluminates) can react with calcium hydroxide in cement during the hydration reaction to form secondary hydration products (such as CSH gel), enhancing the strength and durability of concrete. Rebound properties: The fine particles and good lubricity of fly ash can reduce the amount of rebound of the material during the spraying process, reducing material waste and improving construction efficiency. The improved fluidity and adhesion properties of fly ash help to control the thickness of the sprayed layer. Good fluidity allows shotcrete to be distributed more evenly, while good adhesion ensures that the material does not easily fall off when the required thickness is achieved.

[0037] Based on 1 part by weight of cement, the lightweight sprayed cement-based composite material provided by this invention comprises 70 to 100 parts by weight of silica fume, preferably 80 to 100 parts by weight. In this invention, the particle size of the silica fume is preferably 0.01 to 1.0 μm, more preferably 0.1 to 1.0 μm; the specific surface area of ​​the silica fume is preferably 15,000 to 30,000 m². 2 / kg, more preferably 20000-25000m 2 / kg; the mass percentage of SiO2 in the silica fume is preferably 90-95%, more preferably 91-92.26%.

[0038] The ultrafine particles of silica fume can improve the viscosity of the slurry, reduce segregation and bleeding, and thus significantly improve the fluidity of the mixture when combined with appropriate water-reducing agents. This facilitates easier pumping and pouring during construction, reducing construction difficulty and time. Silica fume can significantly improve the adhesion properties of materials because its extremely fine particles can fill the tiny pores in the cement matrix, increasing the density and bonding strength of the material. For shotcrete, good adhesion properties ensure better adhesion of the material to the substrate, reducing the possibility of detachment and cracking. The highly active components of silica fume can undergo a secondary reaction with calcium hydroxide generated during cement hydration, producing more CSH gel, thereby significantly improving the compressive strength, flexural strength, and durability of concrete. Silica fume can also improve the crack resistance and impermeability of the material, enhancing its overall mechanical properties. In shotcrete, rebound rate is an important performance indicator. The fine particles and high viscosity of silica fume can reduce the amount of rebound during the spraying process, reducing material waste and improving construction efficiency. The improved fluidity and adhesion properties of silica fume help control the thickness of the sprayed layer. Good fluidity allows shotcrete to be distributed more evenly, while good adhesion ensures that the material does not easily fall off when the required thickness is achieved.

[0039] Based on 1 part by weight of cement, the lightweight sprayed engineering cement-based composite material provided by this invention comprises 110 to 385 parts by weight of hollow fly ash microspheres, preferably 165 to 300 parts by weight. In this invention, the particle size of the hollow fly ash microspheres is preferably 1 to 300 μm, more preferably 100 to 200 μm; the wall thickness of the hollow fly ash microspheres is preferably 2 to 5 μm, more preferably 3 to 4 μm; and the specific surface area of ​​the hollow fly ash microspheres is preferably 350 to 500 m². 2 / kg, more preferably 400-450mg 2 / kg, with a preferred density of 0.6–0.8 g / cm³. 3 More preferably, it is 0.65–0.75 g / cm³. 3 The bulk density of the hollow fly ash microspheres is preferably 500-600 kg / m³. 3 More preferably, it is 520–550 kg / m³. 3 The apparent specific gravity of the hollow fly ash microspheres is preferably 1100–1300 kg / m³. 3 More preferably, it is 1150–1200 kg / m³. 3 .

[0040] Hollow fly ash microspheres have an extremely low density (typically 0.6–0.8 g / cm³). 3 The content of this material is far lower than that of ordinary cement (approximately 3.1–3.2 g / cm³). 3Hollow fly ash microspheres, along with other conventional aggregates, can significantly reduce the overall density of materials, thus achieving a lightweight effect. This is particularly important for reducing structural self-weight and improving the seismic performance of buildings. Flowability: The spherical particle structure of hollow fly ash microspheres helps improve the flowability of the mixture. Its smooth surface and spherical structure reduce internal friction, making the slurry easier to flow during mixing and pumping, improving the convenience and efficiency of construction. Adhesion Properties: Hollow fly ash microspheres can fill the pores in the cement matrix, improving the material's density and adhesion. Their spherical structure also increases the lubricity of the slurry, improving the adhesion between the material and the substrate. This is especially important for shotcrete, reducing material detachment and waste during construction. Mechanical Properties: Although hollow fly ash microspheres are mainly used to reduce material density, their high-strength shell structure can also improve the compressive strength and crack resistance of the material to some extent. Furthermore, hollow fly ash microspheres can optimize the particle size distribution of the material, improving its overall mechanical properties. Resilience: In shotcrete construction, rebound rate is a key performance indicator. The addition of hollow fly ash microspheres can significantly reduce the rebound of the material during spraying because its spherical particles can better embed into the substrate surface, improving material adhesion, thereby reducing material waste and increasing construction efficiency. Thickness control: The improved flowability and adhesion properties of hollow fly ash microspheres help to better control the thickness of the sprayed layer. Its good flowability allows for more uniform distribution of sprayed concrete, while its excellent adhesion ensures that the material is not easily detached when the required thickness is achieved.

[0041] The lightweight sprayed engineering cement-based composite material provided by the present invention comprises 255 to 316 parts by weight of water, preferably 260 to 316 parts by weight, based on 1 part by weight of cement.

[0042] Based on 1 part by weight of cement, the lightweight sprayed engineering cement-based composite material provided by the present invention comprises 15 to 20 parts by weight of organic fiber, preferably 17 to 20 parts by weight. In the present invention, the organic fiber comprises polyethylene fiber; the length of the organic fiber comprises 6 mm and 12 mm; the mass ratio of 6 mm long organic fiber to 12 mm long organic fiber is preferably 0.8 to 1:1, more preferably 1:1; the diameter of the organic fiber is preferably 20 to 25 μm, more preferably 24 μm.

[0043] Flowability: Organic fibers have a dual impact on the flowability of materials. Although the addition of fibers increases the viscosity of the slurry, slightly reducing flowability, good flowability can still be maintained by properly controlling the fiber content and using appropriate water-reducing agents. Simultaneously, the presence of fibers can prevent segregation or bleeding during pumping and construction, improving "workability." "Workability" refers to the ease of handling and processing of materials during construction, specifically including the following aspects: Flowability: Whether the material flows easily, fills molds or structural voids, and is easy to construct and pump; Cohesiveness: Whether the material remains uniform during flow, preventing segregation or bleeding; Plasticity: The workability of the material during molding, such as ease of smoothing and compaction; Water Retention: Whether the material can retain appropriate moisture during construction, avoiding construction difficulties or quality problems caused by excessive water loss.

[0044] Adhesion Properties: Organic fibers enhance the adhesion between the material and the substrate. Dispersed within the material, the fibers form a three-dimensional network structure, contributing to improved overall adhesion. This reinforcing effect is particularly noticeable in shotcrete, ensuring better adhesion to the substrate and reducing material detachment during construction. Mechanical Properties: Organic fibers significantly improve the crack resistance and toughness of the material. The fibers act as a bridge within the material, preventing crack formation and propagation, thereby increasing tensile strength and fracture toughness. This is highly beneficial for the early strength development and long-term durability of shotcrete. Resilience: In shotcrete application, organic fibers reduce the rebound rate of the material. The presence of fibers increases internal friction, making it easier for the shotcrete to adhere to the substrate surface, reducing rebound during application, thus improving material utilization and reducing waste. Thickness Control: The reinforcing effect of organic fibers helps to better control the thickness of the shotcrete layer during application. Fiber-reinforced materials exhibit good adhesion and stability during layered spraying, ensuring good bonding between layers, preventing interlayer cracking or peeling, and ensuring the uniformity and required thickness of the sprayed layer.

[0045] Based on 1 part by weight of cement, the lightweight sprayed cement-based composite material provided by the present invention includes 3.5 to 6 parts by weight of a water-reducing agent, preferably 3.5 to 5 parts by weight. In the present invention, the water-reducing agent is preferably a polycarboxylate high-efficiency water-reducing agent; the water reduction rate of the water-reducing agent is preferably 20 to 30%, more preferably 22 to 25%.

[0046] Based on 1 part by weight of cement, the lightweight sprayed engineering cement-based composite material provided by the present invention includes 0.3 to 0.4 parts by weight of thickener, preferably 0.3 parts. In the present invention, the thickener preferably includes hydroxypropyl methylcellulose.

[0047] Flowability: One of the main functions of thickeners is to regulate the flowability of the slurry. Although thickeners increase the viscosity of the slurry and may slightly reduce its flowability, proper use of thickeners can prevent segregation or bleeding during pumping or spraying, thus maintaining good workability. Furthermore, thickeners can help maintain appropriate flowability at low water-cement ratios, optimizing the workability of the material. Adhesion Properties: Thickeners can significantly improve the adhesion properties of the material. By increasing the viscosity of the slurry, thickeners enhance the bond between the material and the substrate, ensuring better adhesion of the material to the substrate surface during spraying. This is crucial for ensuring the stability of shotcrete and reducing material detachment.

[0048] The lightweight sprayed cement-based composite material provided by this invention exhibits excellent flowability, good adhesion, and significant mechanical properties. Especially with a high content of hollow fly ash microspheres (FAC), it demonstrates buoyancy, making it suitable for engineering applications that reduce structural weight and improve construction efficiency, such as the reinforcement of beams, columns, beam-column joints, walls, and slabs. It has significant practical engineering application value.

[0049] The lightweight sprayed cement-based composite material provided by this invention is also suitable for the reinforcement of tunnels and underground structures. Tunnels and underground structures typically require materials with good flowability and rapid setting properties to enable effective construction in confined spaces. The material of this invention can quickly fill and reinforce these structures, enhancing their water resistance, impermeability, and compressive strength, reducing maintenance costs, and extending structural lifespan.

[0050] This invention also provides a method for preparing the lightweight sprayed engineering cement-based composite material described in the above technical solution, comprising the following steps:

[0051] Cement, fly ash, silica fume, and hollow fly ash microspheres are first mixed to obtain a dry powder mixture;

[0052] The dry powder mixture, a portion of water, and a portion of water-reducing agent are mixed in a second mixture. Then, the remaining water, the remaining water-reducing agent, and the thickener are added in a third mixture. Finally, organic fibers are added for dispersion to obtain the lightweight sprayed engineering cement-based composite material.

[0053] In this invention, the first mixing is preferably carried out at a low speed setting; the low speed setting is preferably 140 r / min rotation and 62 r / min revolution; the first mixing time is preferably 2 min.

[0054] In this invention, the second mixing is preferably carried out at a high speed; the high speed is preferably 285 r / min for rotation and 125 r / min for revolution; the second mixing time is preferably 3 min.

[0055] In this invention, the third mixing is preferably performed at a high speed; the high speed is preferably 285 r / min for rotation and 125 r / min for revolution; the third mixing time is preferably 3 min; the mass ratio of the partial water to the remaining water is preferably 0.8 to 1:1, more preferably 1:1; the mass ratio of the partial water-reducing agent to the remaining water-reducing agent is preferably 0.8 to 1:1, more preferably 1:1.

[0056] In this invention, the dispersion is preferably carried out at a low speed setting; the low speed setting is preferably 140 r / min for rotation and 62 r / min for revolution; the dispersion time is preferably 120 s.

[0057] The present invention also provides the application of the lightweight sprayed engineering cement-based composite material described in the above technical solution or the lightweight sprayed engineering cement-based composite material prepared by the preparation method described in the above technical solution in building construction.

[0058] In this invention, the preferred method of application includes: spraying the lightweight sprayed cement-based composite material onto the substrate surface and then curing it. In this invention, the spraying equipment is preferably a spray gun, more preferably a 9511 type handheld mortar spray gun; the diameter of the spray nozzle is preferably 6-10 mm, more preferably 8 mm; the distance between the spray nozzle and the substrate surface is preferably 20-40 cm, more preferably 30 cm; the airflow pressure is preferably 0.6-1 MPa, more preferably 0.8 MPa; the spray thickness is preferably ≤25 mm, more preferably 20 mm; the spraying is preferably layered; the thickness of each layer is preferably 10-15 mm, more preferably 12-14 mm; the curing is preferably carried out in a curing room; the curing temperature is preferably 20-25℃, more preferably 23℃; the relative humidity is preferably 90-95%, more preferably 95%; and the curing time is preferably 14-28 days, more preferably 28 days.

[0059] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0060] Examples 1-6

[0061] The component ratios of the lightweight sprayed engineering cement-based composite materials in Examples 1 to 6 are shown in Table 1.

[0062] Table 1. Component proportions (kg / m³) of lightweight sprayed cement-based composite materials in Examples 1-6 3 )

[0063]

[0064] The characteristics of the raw materials used are as follows:

[0065] The cement is OPC type 525 ordinary Portland cement, sourced from Zhucheng Yangchunshan Water Co., Ltd.

[0066] The fly ash is grade I fly ash, with a particle size of 1–100 μm and a specific surface area of ​​200–500 cm³. 2 / g, density is 2.1~2.6g / cm³ 3 It originates from Gongyi Borun Refractory Materials Co., Ltd.

[0067] The particle size of silica fume is 0.01–1.0 μm, and the specific surface area is 15,000–30,000 m². 2 / kg, the mass percentage of SiO2 in the silica fume is 92.26%, and it comes from Henan Borun New Materials Co., Ltd.;

[0068] The hollow fly ash microspheres have a particle size of 1–300 μm, a wall thickness of 2–5 μm, and a specific surface area of ​​400 m². 2 / kg, with a preferred density of 0.6 g / cm³. 3 The bulk density is 550 kg / m³ 3 Apparent specific gravity is 1200 kg / m³ 3 It originates from Gongyi Borun Refractory Materials Co., Ltd.

[0069] The polyethylene fibers are 6mm and 12mm in length and 24μm in diameter, and are sourced from a domestic fiber material supplier.

[0070] Polycarboxylate superplasticizer with a water reduction rate of 30% is sourced from Sika (Jiangsu) Building Materials Co., Ltd.

[0071] The thickener is hydroxypropyl methylcellulose (CMC), sourced from Jinzhou Baoyi Building Materials Technology Co., Ltd.

[0072] The preparation method of the lightweight sprayed engineering cement-based composite material includes the following steps:

[0073] Cement, fly ash, silica fume, and hollow fly ash microspheres are added to a mixing pot and stirred at low speed (140 r / min rotation, 62 r / min revolution) for 2 minutes to fully mix all the dry powders and obtain a dry powder mixture. Half of the required amount of water and water-reducing agent are weighed and added to the mixing pot, and stirred at high speed (285 r / min rotation, 125 r / min revolution) for 3 minutes. Then, the remaining water, remaining water-reducing agent, and thickener are added, and stirred at high speed for another 3 minutes. After manually dispersing the polyethylene fibers, the polyethylene fibers are slowly added while running at low speed and stirred for 120 seconds. Check for fiber clumping to obtain the lightweight sprayed engineering cement-based composite material.

[0074] Comparative Example 1

[0075] 1) Raw material ratio: The raw materials are shown in Table 2.

[0076] Table 2 shows the raw material formulation in Comparative Example 1.

[0077] Material Name <![CDATA[Usage / (kg / m 3 )]]> mass ratio cement 489 1.00 fine aggregate / sand 852 1.74 Coarse aggregate / stone 670 1.37 Mixing water 215 0.44 Admixtures / Polycarboxylate superplasticizer 24.45 0.050 PVA fiber 1.2 0.0024

[0078] 2) Mixing: A mixture of gravel, sand, cement, fiber (mixed for 30-60 seconds) + water and polycarboxylate superplasticizer (mixed until finished); Alternatively, the fiber can be added to the mixture of water and polycarboxylate superplasticizer first and stirred to disperse before being added to the mixer and mixed with other materials.

[0079] 3) After mixing, take random samples. If the fibers have been evenly dispersed into monofilaments, the concrete can be used. If there are still bundles of fibers, the mixing time should be extended by 30 to 60 seconds.

[0080] Comparative Example 2

[0081] The difference from Example 5 is that hollow fly ash microspheres are not added.

[0082] Comparative Example 3

[0083] The difference from Example 5 is that no silica fume is added.

[0084] Application Example 1

[0085] The lightweight sprayed engineering cement-based composite material prepared in Example 1 was poured into a spray gun (9511 type handheld mortar spray gun, nozzle diameter 8mm, airflow pressure 0.8MPa). The spray gun was kept 30cm away from the substrate surface, and the spray thickness was controlled within 25mm. Layered spraying was carried out, with each layer controlled to a thickness of 10-15mm. During the spraying process, attention was paid to uniform spraying to avoid clogging of the spray gun. After spraying, the sprayed specimens were placed in a curing room (temperature 23℃, relative humidity 95%) and cured for 28 days to ensure that the specimens reached the optimal strength under constant temperature and humidity conditions.

[0086] Application Example 2

[0087] The difference from Application Example 1 is that the lightweight sprayed engineering cement-based composite material prepared in Example 1 is replaced with the lightweight sprayed engineering cement-based composite material prepared in Example 2.

[0088] Application Example 3

[0089] The difference from Application Example 1 is that the lightweight sprayed engineering cement-based composite material prepared in Example 1 is replaced with the lightweight sprayed engineering cement-based composite material prepared in Example 3.

[0090] Application Example 4

[0091] The difference from Application Example 1 is that the lightweight sprayed engineering cement-based composite material prepared in Example 1 is replaced with the lightweight sprayed engineering cement-based composite material prepared in Example 4.

[0092] Application Example 5

[0093] The difference from Application Example 1 is that the lightweight sprayed engineering cement-based composite material prepared in Example 1 is replaced with the lightweight sprayed engineering cement-based composite material prepared in Example 5.

[0094] Comparative Application Example 1

[0095] The difference from Application Example 5 is that the lightweight sprayed engineering cement-based composite material prepared in Example 1 is replaced with the cement-based composite material prepared in Comparative Example 1.

[0096] Comparative Application Example 2

[0097] The difference from Application Example 5 is that the lightweight sprayed engineering cement-based composite material prepared in Example 1 is replaced with the cement-based composite material prepared in Comparative Example 2.

[0098] Comparative Application Example 3

[0099] The difference from Application Example 5 is that the lightweight sprayed engineering cement-based composite material prepared in Example 1 is replaced with the cement-based composite material prepared in Comparative Example 3.

[0100] Performance testing

[0101] The properties of the lightweight sprayed engineering cement-based composite materials prepared in Examples 1-6 and the cement-based composite materials prepared in Comparative Examples 1-3 were tested, and the results are shown in Table 3. The test methods are as follows:

[0102] Flowability Test: The test was conducted according to GB / T2419-2005 "Method for Determination of Flowability of Cement Mortar," using an NLD-3 cement mortar flowability tester. Procedure: Following GB / T2419-2005, freshly mixed LSECC was filled into a conical mold in two layers, each layer being evenly compacted with a tamping rod. After compaction, the diameter of the dispersed material was measured with a ruler, and the average value was calculated as the flowability.

[0103] Maximum spray thickness test: Equipment: drywall, steel ruler. Procedure: Continuously spray LSECC onto the upright drywall until a certain thickness is achieved and the LSECC begins to slide off. Measure the maximum spray thickness with a steel ruler.

[0104] Density test: The water displacement method was used. Equipment: constant temperature drying oven, electronic scale, measuring cup. Procedure: After drying the sample to constant weight, its mass and volume were measured. The density was calculated based on the mass and volume, as detailed below. Figure 2 As shown.

[0105] Compressive strength test: Equipment: MTS200T compression testing machine. Procedure: Place the specimen at the loading center of the testing machine, using force control, with a loading rate of 200 N / s. Measure the ultimate compressive strength of the cubic specimen. Calculate the compressive strength using the formula σm = F / A, as detailed below. Figure 3 As shown.

[0106] Tensile strength test: Equipment: 300kN MTS microcomputer-controlled electronic universal testing machine. Procedure: Perform uniaxial tensile tests according to the recommendations of the Japan Society of Civil Engineers (JSCE). The gauge length of the dog bone specimen is 80mm, and the loading rate is 1mm / min. Measure the tensile force and elongation, and calculate the stress and strain, as follows. Figure 4 As shown.

[0107] Four-point flexural strength test: Equipment: 30t universal testing machine, VIC-3D system. Procedure: ECC was sprayed onto a fine aggregate concrete layer prepared in a mold, with a spray thickness of 20mm. After 28 days of curing, a four-point flexural strength test was conducted, with a displacement control rate of 0.5mm / min. The VIC-3D system was used for non-contact testing of strain and crack development, such as... Figure 5 As shown.

[0108] Table 3. Properties of the lightweight sprayed engineering cement-based composite materials prepared in Examples 1-6

[0109]

[0110] As shown in Table 3, the flowability range of the lightweight sprayed engineering cement-based composite materials prepared in Examples 1-6 is 135-190 mm, the maximum spraying thickness is 28-55 mm, and the density range is 960-1630 kg / m³. 3 The compressive strength ranges from 15.45 to 51.2 MPa, the tensile strength ranges from 2.4 to 5.6 MPa, and the ultimate tensile strain ranges from 4.4 to 6.6%.

[0111] Figure 6 These are images showing the spraying morphology and spraying thickness of the lightweight sprayed engineering cement-based composite materials prepared in Examples 1-3. Figure 7 These are spray morphology and spray thickness images of the lightweight sprayed engineering cement-based composite materials prepared in Examples 4-6. Figures 6-7As can be seen, the maximum spraying thickness of the lightweight sprayed engineering cement-based composite material prepared by this invention can reach 25 mm. Moreover, according to the principle of layered and multiple spraying, a more considerable spraying thickness can be formed layer by layer. After the content of hollow fly ash microspheres reaches 50%, the maximum single spraying thickness is significantly improved, with the maximum spraying thickness of the LSECC70 formulation reaching 55 mm. The lightweight sprayed engineering cement-based composite material can adhere well to the substrate because the maximum adhesion force it can provide can maintain its own weight. Therefore, after the content of hollow fly ash microspheres exceeds 50%, its density decreases rapidly, and its own weight also decreases rapidly. Thus, under the condition of comparable adhesion force, it can maintain a greater spraying thickness.

[0112] Figure 8 The chart shows the buoyancy test results of the lightweight sprayed engineering cement-based composite material prepared in Example 6. Figure 8 As can be seen from the data, the density of the lightweight sprayed engineering cement-based composite material (LSECC70) prepared in Example 6 is 960 kg / m³. 3 It has the property of being able to float.

[0113] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A lightweight jet-engine cementitious composite material, characterized by, By mass parts, the following components are included: cement 210-600 parts, fly ash 100-700 parts, silica fume 70-100 parts, hollow fly ash cenospheres 110-385 parts, water 255-316 parts, organic fiber 15-20 parts, water reducing agent 3.5-6 parts, and thickening agent 0.3-0.4 parts; The particle size of the hollow fly ash microsphere is 1-300 microns; the specific surface area of the hollow fly ash microsphere is 350-500 m 2 / g; and the bulk density of the hollow fly ash microsphere is 500-600 kg / m 3 . the organic fiber includes polyethylene fiber; the length of the organic fiber includes 6 mm and 12 mm; the mass ratio of the organic fiber with a length of 6 mm to the organic fiber with a length of 12 mm is 0.8-1:1; the diameter of the organic fiber is 20-25 μm; The particle size of the silica fume is 0.01-1.0 μm; the specific surface area of the silica fume is 15000-30000 m 2 / kg.

2. The lightweight jet engineered cementitious composite material of claim 1, wherein, the cement is OPC type 525 ordinary Portland cement.

3. The lightweight jet engineered cementitious composite material of claim 1, wherein, the fly ash is first grade fly ash.

4. The lightweight jet engineered cementitious composite material of claim 1, wherein, the water reducing agent is polycarboxylate high efficiency water reducing agent.

5. The lightweight jet engineered cementitious composite material of claim 1, wherein, the thickening agent includes hydroxypropyl methyl cellulose.

6. The method of manufacturing a lightweight shotcrete cementitious composite material according to any one of claims 1 to 5, characterized in that, the following steps are included: first mixing cement, fly ash, silica fume, and hollow fly ash cenospheres to obtain dry powder mixture; second mixing the dry powder mixture, part of water, and part of water reducing agent, then third mixing the remaining water, the remaining water reducing agent, and thickening agent, and finally adding organic fiber for dispersion to obtain the lightweight sprayed engineering cement-based composite material.

7. Application of the lightweight sprayed engineering cement-based composite material of any one of claims 1-5 or the lightweight sprayed engineering cement-based composite material prepared by the preparation method of claim 6 in building construction.

8. Use according to claim 7, characterized in that, the application mode includes: after spraying the lightweight sprayed engineering cement-based composite material to the surface of a substrate, curing is performed; the diameter of the nozzle used for spraying is 6-10 mm; the air flow pressure of the spraying is 0.6-1 MPa; the spraying thickness of the spraying is ≤25 mm; and the spraying is layering spraying.

Images