Reinforced concrete base material and applications

Abstract

This invention belongs to the field of concrete materials technology, specifically relating to a reinforced concrete base material and its application. The method involves mixing cement, fly ash, and aggregates, adding water, and stirring to obtain a concrete mixture. Polyvinyl alcohol fiber, polystyrene particles, antifreeze, and waterproofing agent are added to the concrete mixture, and after stirring, a water-reducing agent is added, followed by continued stirring to obtain a concrete cement paste. Foam is added to the concrete cement paste, and after stirring, an accelerator is added, followed by continued stirring to obtain a foamed concrete slurry. The prepared reinforced concrete base material enhances the strength of the foamed concrete material and improves its buffering and energy absorption performance. When applied to underground engineering support systems, it can reduce the stress on other support structures and ensure the long-term stability of underground engineering projects.

Description

Technical Field

[0001] This invention belongs to the field of concrete materials technology, specifically relating to a reinforced concrete matrix material and its application. Background Technology

[0002] With the continuous development of underground infrastructure construction in my country, the number of major geotechnical engineering projects, such as transportation tunnel construction, coal mine mining, and large-scale water resource development, is increasing. Simultaneously, the depth of underground engineering construction is increasing, and the problems arising in underground engineering are becoming more prominent. Taking tunnel engineering as an example, completed tunnels are usually surrounded by surrounding rock masses, and the characteristics of the surrounding rock are a key factor affecting the structural stability of the tunnel. Extensive field measurements and laboratory test data show that the stress and deformation of the surrounding rock is a time-dependent process, and the mechanical properties of the surrounding rock not only exhibit common elasticity and plasticity but also rheological characteristics. Among the rheological properties of rocks, rock creep has the greatest impact on tunnel engineering and is an important reason affecting the long-term stability of the tunnel's surrounding rock.

[0003] In soft rock underground engineering surrounding rock support systems, setting up a buffer layer with good deformation capacity is an effective means to improve the self-supporting capacity of the surrounding rock and reduce support costs. The buffer layer is mainly used to absorb the deformation of the surrounding rock, reduce the stress on other support structures, and ensure the long-term stability of the underground project. Therefore, its filling material needs to have a strong deformation absorption capacity and still maintain a certain strength and integrity after deformation. Foamed concrete is widely used in various fields of construction due to its advantages such as low density, excellent thermal conductivity, good sound insulation, significant seismic effect, and good fire resistance, but it also has problems such as low strength, large shrinkage, and poor energy absorption performance. Summary of the Invention

[0004] This invention provides a reinforced concrete matrix material and its application.

[0005] The technical solution of the present invention is as follows:

[0006] This invention provides a reinforced concrete matrix material, comprising the following raw materials and their amounts:

[0007] The addition amount of fly ash is 0%-50% of the cement weight, the addition amount of aggregate is 15-45% of the cement weight, the water-cement ratio is 30%-50%, the addition amount of polyvinyl alcohol fiber is 0.8%-1.6% of the concrete mixture weight, the volume addition amount of polystyrene particles is 3%-10% of the concrete mixture weight, the addition amount of antifreeze agent is 1.8%-2.2% of the cement weight, the addition amount of waterproofing agent is 0.2%-0.8% of the concrete mixture weight, the addition amount of water-reducing agent is 0.8%-1.2% of the cement weight, the addition amount of accelerator is 3%-4% of the cement weight, and the volume addition amount of foam is 100%-160% of the cement weight.

[0008] The reinforced concrete matrix material is prepared through the following steps:

[0009] (1) Mix cement, fly ash and aggregate, add water and stir to obtain concrete mixture;

[0010] (2) Add polyvinyl alcohol fiber, polystyrene particles, antifreeze agent and waterproofing agent to the concrete mixture, stir, add water-reducing agent, and continue stirring to obtain concrete cement paste.

[0011] (3) Add foam to the concrete cement paste, stir, add accelerator, and continue stirring to obtain foamed concrete paste.

[0012] The reinforced concrete matrix material described in this invention has a density of 1012-1141 kg / m³. 3 The compressive strength is 7.5-7.83 MPa, the elastic modulus is 1225-1382 MPa, and the energy absorption of strain within 0-45% is 2.547-2.7143 MPa.

[0013] The aggregate in step (1) of this invention is sand with a particle size of 0.2-0.5 mm.

[0014] The polyvinyl alcohol fiber in step (2) of the present invention has a length of 6-10 mm.

[0015] The polystyrene particles in step (2) of this invention have a particle size of 4-6 mm.

[0016] The foam in step (3) of the present invention is obtained by foaming with an animal protein foaming agent, and the foam diameter is less than 1 mm.

[0017] In step (3) of this invention, foam is added in two steps, with the amount of foam added in the first step being 20%-25% of the total amount of foam.

[0018] The present invention also includes the pouring, molding, and curing of foamed concrete slurry.

[0019] This invention also provides an application of reinforced concrete-based materials in underground engineering support systems.

[0020] The application described in this invention is the use of a reinforced concrete matrix material in underground engineering support systems to improve concrete strength and provide energy absorption and buffering.

[0021] Beneficial effects

[0022] In the preparation process of reinforced concrete matrix materials, this invention adds sand with a particle size of 0.2-0.5mm as aggregate, which can better fill the voids in the concrete, making the formed structure denser, increasing the concrete density, and thus enhancing the strength of the concrete.

[0023] This invention selects polyvinyl alcohol fibers with a length of 6-10mm, which are easy to disperse evenly and can better prevent concrete from cracking and spalling under stress. It can also improve the impact resistance and load-bearing capacity of concrete, thereby helping to improve the durability of concrete materials.

[0024] This invention adds polystyrene particles with a particle size of 4-6mm to the raw materials. The polystyrene particles have certain toughness, elasticity and light weight, which helps to improve the deformation capacity of concrete and increase energy absorption.

[0025] In the preparation process, the present invention directly adds foam obtained by foaming with animal protein foaming agent. The foam used is fine, dense and uniform, with low water bleeding rate and no emulsified foam, so as to ensure that the foam is fully mixed with the concrete cementitious paste.

[0026] The reinforced concrete matrix material prepared by this invention has a density of 1012-1141 kg / m³. 3 It has a compressive strength of 7.5-7.83 MPa, an elastic modulus of 1225-1382 MPa, and an energy absorption of 2.547-2.7143 MPa within a strain range of 0-45%. As a buffer layer, its application in underground engineering support systems can reduce the cost of underground engineering support, effectively improve the problem of low strength of foamed concrete, increase the energy absorption of foamed concrete, improve the support level of major geotechnical and underground engineering projects such as underground tunnel construction, coal mining, and large-scale water resource development, and improve the long-term stability of soft rock underground engineering and the ability of the support structure to resist the rheology of the surrounding rock. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a test specimen model for engineering applications.

[0028] Figure 2 The diagrams show the uniaxial compression failure process of the test specimens for engineering applications. (a) is a schematic diagram of the uniaxial compression failure process of the control group, and (b) is a schematic diagram of the uniaxial compression failure process of the experimental group 1. Detailed Implementation

[0029] The following examples are intended to illustrate the present invention, and not to further limit the invention.

[0030] This invention provides a reinforced concrete matrix material, comprising the following raw materials and their amounts:

[0031] The addition amount of fly ash is 0%-50% of the cement weight, the addition amount of aggregate is 15-45% of the cement weight, the water-cement ratio is 30%-50%, the addition amount of polyvinyl alcohol fiber is 0.8%-1.6% of the concrete mixture weight, the volume addition amount of polystyrene particles is 3%-10% of the concrete mixture weight, the addition amount of antifreeze agent is 1.8%-2.2% of the cement weight, the addition amount of waterproofing agent is 0.2%-0.8% of the concrete mixture weight, the addition amount of water-reducing agent is 0.8%-1.2% of the cement weight, the addition amount of accelerator is 3%-4% of the cement weight, and the volume addition amount of foam is 100%-160% of the cement weight.

[0032] Preferably, the amount of fly ash added is 13%-17% of the cement weight, the amount of aggregate added is 29%-32% of the cement weight, the water-cement ratio is 46%-50%, and the volumetric volume of foam added is 130%-145% of the cement weight; the reinforced concrete matrix material is prepared through the following steps:

[0033] (1) Mix cement, fly ash and aggregate, add water and stir to obtain concrete mixture;

[0034] (2) Add polyvinyl alcohol fiber, polystyrene particles, antifreeze, and waterproofing agent to the concrete mixture. After stirring, add water-reducing agent and continue stirring to obtain concrete cementitious slurry. The concrete cementitious slurry has a uniform consistency, neither too thick nor too thin, is delicate and smooth, has good viscosity and dispersibility, and does not retard setting. (3) Add foam to the concrete cementitious slurry and stir. Add accelerator half a minute before the end of stirring and continue stirring. When no layer of floating foam is visible on the slurry surface, foamed concrete slurry is obtained. There is no floating foam accumulation at the top of the foamed concrete slurry and no material clumps deposited at the bottom. There are no 3-10mm granular slurry particles in the slurry, and the foam loss rate is ≤10%. The slurry is stable, has a suitable consistency, and good material suspension.

[0035] This invention improves the strength of foamed concrete by adding polyvinyl alcohol fibers to the concrete base material. In addition, the addition of polystyrene particles and aggregates enhances the energy absorption performance of the concrete base material, thereby ensuring that the reinforced concrete base material, as a buffer layer, can absorb the deformation of the surrounding rock, reduce the stress on other support structures, and ensure the long-term stability of underground engineering.

[0036] In order to further enhance the stability of the reinforced concrete base material, it is necessary to ensure the density of the material. The aggregate in step (1) is sand with a particle size of 0.2-0.5 mm. Aggregates with this particle size can better fill the voids in the concrete, making the structure more compact, increasing the density of the concrete, and thus enhancing the strength of the concrete.

[0037] Furthermore, to extend the lifespan of the reinforced concrete matrix material, the polyvinyl alcohol fibers in step (2) are 6-10 mm in length. With the same fiber content, shorter polyvinyl alcohol fibers are easier to disperse evenly, better preventing cracking and spalling of the concrete under stress. They also improve the impact resistance and load-bearing capacity of the concrete, thereby contributing to improved durability.

[0038] Furthermore, in order to improve the buffer energy absorption performance of the reinforced concrete matrix material, the polystyrene particles in step (2) have a particle size of 4-6 mm. Under the premise of meeting the concrete strength requirements, given that polystyrene particles have certain toughness, elasticity and light weight, adding an appropriate amount of polystyrene particles can help improve the deformation capacity of the concrete and increase the energy absorption.

[0039] This invention uses low-speed mixing to obtain concrete cement paste, thereby ensuring that the cement paste has good fluidity and uniformity. Specifically, in step (2), the mixing speed is 30-40 r / min and the mixing time is 1-3 min; the continued mixing time is 1-1.5 min.

[0040] To ensure the porosity of the reinforced concrete matrix material, the foam in step (3) is obtained by foaming with an animal protein foaming agent, with a foam diameter of less than 1 mm. The foam used is fine, dense, and uniform, with low bleeding rate and no emulsified foam, to ensure that the foam is fully mixed with the concrete cementitious paste.

[0041] Furthermore, in order to ensure the utilization rate of foam, the foam is added in step (3) in two steps. The amount of foam added in the first step is 20%-25% of the total amount of foam. A small amount of foam is added first to ensure that the foam and concrete cement paste are mixed evenly and to make the concrete cement paste thinner and easier to disperse. The remaining foam is then added, which can reduce the amount of foam loss and save reaction time.

[0042] This invention uses high-speed mixing to obtain foamed concrete slurry. Specifically, in step (3), the mixing speed is 60-120 r / min and the mixing time is 1-5 min. High-speed mixing can ensure that the foam is quickly and evenly mixed with the concrete cementitious slurry, reducing foam loss, and also reducing the mixing time.

[0043] To ensure the performance of the reinforced concrete base material, the process also includes pouring, molding, and curing the foamed concrete slurry. Specifically, a release agent is applied inside the mold during pouring. If the surface of the product is required to be free of bubbles, dense, and smooth, a water-based release agent with a certain defoaming ability should be applied. After applying the release agent, the mold should be checked to ensure it is tight, free of micro-cracks, and free of water leakage. Otherwise, the gaps should be sealed with sealant.

[0044] When pouring, do not pour into one part continuously. Instead, pour into different parts of the mold in a circular manner. Do not vibrate. For parts where the grout is not fully poured, gently press them with a small stick, but do not pat them. The poured grout should be 2-5mm higher than the top of the mold, and then gently scrape it level with a scraper.

[0045] After pouring, carefully observe the changes in the grout to see if it settles, leaks, or seeps. If it settles, measure and record the height and speed of settlement, and adjust the formula accordingly. If there is leakage or seepage, take remedial measures promptly. If formwork collapse occurs, remove the waste grout and re-pour. After the grout has initially set, cover the mold with plastic sheeting to prevent moisture evaporation from affecting hydration. Demold after 48 hours and cure for 28 days according to standard.

[0046] The resulting reinforced concrete matrix material has a density of 1012-1141 kg / m³. 3 The compressive strength is 7.5-7.83 MPa, the elastic modulus is 1225-1382 MPa, and the energy absorption of strain within 0-45% is 2.547-2.7143 MPa.

[0047] This invention also provides an application of reinforced concrete-based materials in underground engineering support systems.

[0048] Furthermore, the application described herein is an application of reinforced concrete matrix materials in underground engineering support systems to improve concrete strength and provide energy absorption and buffering.

[0049] The reinforced concrete matrix material prepared by this invention can reduce the support cost of underground engineering, effectively improve the problem of low strength of foamed concrete, increase the energy absorption of foamed concrete, improve the support level of major geotechnical and underground engineering projects such as underground tunnel construction, coal mining, and large-scale water resource development, and improve the long-term stability of soft rock underground engineering and the ability of the support structure to resist the rheology of the surrounding rock.

[0050] Example 1

[0051] (1) Mix cement, fly ash and sand, add water and stir to obtain concrete mixture; the amount of fly ash added is 15% of the weight of cement, the particle size of sand is 0.2-0.5mm, the amount of sand added is 30% of the weight of cement, and the water-cement ratio is 50%.

[0052] (2) Add polyvinyl alcohol fiber, polystyrene particles, antifreeze agent, and waterproofing agent to the concrete mixture. Stir at a stirring speed of 35 r / min for 2 min, then add water-reducing agent and continue stirring for 1.2 min to obtain concrete cement paste. The polyvinyl alcohol fiber has a length of 6 mm and the amount of polyvinyl alcohol fiber added is 0.8% of the weight of the concrete mixture. The polystyrene particles have a particle size of 4 mm and the volume (L) of the polystyrene particles added is 7% of the mass (kg) of the concrete mixture. The amount of antifreeze agent added is 2% of the weight of cement, the amount of waterproofing agent added is 0.6% of the weight of the concrete mixture, and the amount of water-reducing agent added is 1% of the weight of cement.

[0053] (3) Add foam with a diameter of less than 1 mm obtained by foaming with animal protein foaming agent to the concrete cement paste in two batches. The amount of foam added in the first batch is 23% of the total amount of foam. Stir at a stirring speed of 90 r / min for 3 min. Add accelerator half a minute before the end of stirring and continue stirring. When no layer of floating foam can be seen on the surface of the paste, foamed concrete paste is obtained. The volume (L) of the foam added accounts for 140% of the weight (kg) of cement, and the amount of accelerator added is 3.5% of the weight of cement. (4) Pour the foamed concrete paste into shape, demold after 48 h, and cure for 28 days according to standard to obtain reinforced concrete base material.

[0054] Example 2

[0055] (1) Mix cement, fly ash and sand, add water and stir to obtain concrete mixture; the amount of fly ash added is 50% of the weight of cement, the particle size of sand is 0.2-0.5mm, the amount of sand added is 45% of the weight of cement, and the water-cement ratio is 40%.

[0056] (2) Add polyvinyl alcohol fiber, polystyrene particles, antifreeze agent, and waterproofing agent to the concrete mixture. Stir at a stirring speed of 40 r / min for 1 min, then add water-reducing agent and continue stirring for 1 min to obtain concrete cement paste. The length of the polyvinyl alcohol fiber is 10 mm, and the amount of polyvinyl alcohol fiber added is 1.6% of the weight of the concrete mixture. The particle size of the polystyrene particles is 4 mm, and the volume (L) of the polystyrene particles added is 10% of the mass (kg) of the concrete mixture. The amount of antifreeze agent added is 2.2% of the weight of cement, the amount of waterproofing agent added is 0.8% of the weight of the concrete mixture, and the amount of water-reducing agent added is 1.2% of the weight of cement.

[0057] (3) Add foam with a diameter of less than 1 mm obtained by foaming with animal protein foaming agent in two batches to the concrete cement paste. The amount of foam added in the first batch is 25% of the total amount of foam. Stir at a stirring speed of 120 r / min for 1 min. Add accelerator half a minute before the end of stirring and continue stirring. When no layer of floating foam can be seen on the surface of the paste, foamed concrete paste is obtained. The volume (L) of the foam added accounts for 160% of the weight (kg) of the cement, and the amount of accelerator added is 4% of the weight of the cement.

[0058] (4) The foamed concrete slurry is poured and molded, demolded after 48 hours, and cured for 28 days to obtain reinforced concrete base material.

[0059] Example 3

[0060] (1) Mix cement and sand, add water and stir to obtain concrete mixture; the sand has a particle size of 0.2-0.5mm, the amount of sand added is 15% of the weight of cement, and the water-cement ratio is 30%.

[0061] (2) Polyvinyl alcohol fiber, polystyrene particles, antifreeze agent, and waterproofing agent are added to the concrete mixture. After stirring at a speed of 30 r / min for 3 min, water-reducing agent is added, and stirring is continued for 1.5 min to obtain concrete cement paste. The length of the polyvinyl alcohol fiber is 8 mm, and the amount of polyvinyl alcohol fiber added is 1.3% of the weight of the concrete mixture. The particle size of the polystyrene particles is 5 mm, and the volume (L) of the polystyrene particles added is 3% of the mass (kg) of the concrete mixture. The amount of antifreeze agent added is 1.8% of the weight of cement, the amount of waterproofing agent added is 0.2% of the weight of the concrete mixture, and the amount of water-reducing agent added is 0.8% of the weight of cement.

[0062] (3) Add foam with a diameter of less than 1 mm obtained by foaming with animal protein foaming agent to the concrete cement paste in two batches. The amount of foam added in the first batch is 20% of the total amount of foam. Stir at a stirring speed of 60 r / min for 5 min. Add accelerator half a minute before the end of stirring and continue stirring. When no layer of floating foam can be seen on the surface of the paste, foamed concrete paste is obtained. The volume (L) of the foam added accounts for 100% of the weight (kg) of cement, and the amount of accelerator added is 3% of the weight of cement. (4) Pour the foamed concrete paste into shape, demold after 48 h, and cure for 28 days according to standard to obtain reinforced concrete base material.

[0063] Comparative Example 1

[0064] Compared with Example 1, in step (2), polyvinyl alcohol fibers with a length of 18 mm are added. The amount of polyvinyl alcohol fibers added is 3% of the weight of the concrete mixture. The rest of the operation is the same as in Example 1, and the same raw materials and dosages are added as in Example 1.

[0065] Comparative Example 2

[0066] Compared with Example 1, in step (3), foam obtained by foaming with plant protein foaming agent is added. The volume (L) of the foam added accounts for 230% of the weight (kg) of cement. The rest of the operation is the same as in Example 1, and the same raw materials and dosages are added as in Example 1.

[0067] Comparative Example 3

[0068] Compared with Example 1, in step (2), polystyrene particles with a particle size of 2 mm are added, and the volume (L) of the polystyrene particles added is 20% of the weight (kg) of the concrete mixture. The rest of the operation is the same as in Example 1, and the same raw materials and dosages are added as in Example 1.

[0069] Comparative Example 4

[0070] Compared with Example 1, in step (1), sand with a particle size of 1-1.5 mm is added, and the amount of sand added is 65% of the weight of cement. The rest of the operation is the same as in Example 1, and the same raw materials and dosages are added as in Example 1.

[0071] Performance testing

[0072] Examples 1-3 and Comparative Examples 1-4 were prepared according to the relevant technical specifications of JG / T 266-2011 "Foamed Concrete", with cubic specimens of 100mm×100mm×100mm prepared for performance testing, including density, compressive strength, elastic modulus and energy absorption.

[0073] (1) Density

[0074] The physical performance tests of the test blocks were conducted in accordance with GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete".

[0075] (2) Compressive strength

[0076] The compressive strength was determined according to the relevant technical specifications of JG / T 266-2011 "Foamed Concrete". The measurement accuracy of the pressure machine should be ±1%, and the failure load of the specimen should be greater than 20% and less than 80% of the full range of the pressure machine. During the compressive strength test, the center of the specimen should be aligned with the center of the lower platen of the testing machine, and the bearing surface of the specimen should be perpendicular to the top surface during molding. The compressive strength of the specimen is the average of the compressive strengths of three specimens, accurate to 0.01 MPa.

[0077] (3) Elastic modulus

[0078] The elastic modulus of concrete was calculated according to the formula specified in the "Test Procedure for Hydraulic Concrete" (SL 352-2006). The elastic modulus of reinforced concrete matrix materials was taken as the average value of the measurements from three specimens.

[0079] (4) Energy absorption

[0080] The energy W absorbed by reinforced concrete matrix materials during uniaxial compression can be obtained by calculating the area under its uniaxial compressive stress-strain curve, as shown in the following formula:

[0081]

[0082] In the formula:

[0083] ε—Strain value at a certain moment;

[0084] σ—The stress value corresponding to the strain value, in MPa.

[0085] Since the amount of raw materials added to each group of test blocks is different, the failure mode and the degree of compaction are also different. In order to facilitate the comparison of the energy absorption of each group of test blocks, this experiment only calculates the energy absorption of the reinforced concrete matrix material during uniaxial compression when the strain ε is between 0-45%.

[0086] The performance test results are as follows:

[0087]

[0088] As shown in the table above, compared with Comparative Examples 1-4, the reinforced concrete matrix materials of Examples 1-3 have good strength and energy absorption buffering performance. This indicates that in the reinforced concrete matrix materials proposed in this application, the particle size of the sand is 0.2-0.5 mm, and the amount of sand added is 15%-45% of the cement weight; the particle size of the polystyrene particles is 4-6 mm, and the volume (L) of the polystyrene particles added is 3%-10% of the concrete mixture mass (kg); the foam added is obtained by foaming with animal protein foaming agent, and the volume (L) of the foam added accounts for 100%-160% of the cement weight (kg), which can improve the density, compressive strength, elastic modulus and energy absorption of concrete, and help improve the strength and energy absorption buffering performance of concrete.

[0089] application

[0090] In this experiment, cement mortar was used as the lining in the underground project. The cement mortar was 150×150×75mm in size. Precast C30 concrete blocks were used as the rock in the underground project. The precast C30 concrete blocks were 150mm×150mm×75mm in size. These blocks formed the engineering application specimens. The total height of the engineering application specimens was 150mm.

[0091] The reinforced concrete matrix materials prepared in Examples 1-3 and Comparative Examples 1-4 were used as buffer layers and filled into engineering application specimens, serving as experimental groups 1-7 respectively. The heights of the cement mortar, reinforced concrete matrix material, and rock were 50 mm. The control group consisted of engineering application specimens without any filling material, with the heights of the cement mortar and rock being 75 mm. A schematic diagram of the engineering application specimen model is shown below. Figure 1 As shown.

[0092] Figure 2 This is a schematic diagram of the uniaxial compression failure process of the specimen for engineering application. The schematic diagram of the uniaxial compression failure process of the control group is shown below. Figure 2 (a) When the stress reaches the specimen's yield strength, vertical cracks parallel to the loading direction begin to appear on one side of the cement mortar layer surface. As the stress level increases, the cracks begin to expand. Simultaneously, multiple fine cracks appear on the other side of the cement mortar layer surface. With continued loading, the cracks gradually expand and extend to both ends of the cement mortar layer. When the axial load reaches the specimen's compressive strength, the cracks in the cement mortar layer increase rapidly, the cement mortar layer surface detaches from the specimen body, the stress level drops rapidly, and eventually, the specimen fails completely. The complete failure mode of the control group specimen is characterized by multiple vertical cracks appearing on the cement mortar layer surface, and part of the cement mortar layer detaching from the specimen surface. The energy absorption of the control group specimen within the strain range of 0-7.5% is 0.3475 MPa.

[0093] During uniaxial compression failure, in Experiments 1-3, the specimens reached their yield strength as stress was gradually applied. Experiment 1 showed a higher yield strength than Experiments 2 and 3, while Experiment 3 had the lowest. Once the stress reached the yield strength, the specimens began to yield, and an arc-shaped crack appeared at the junction of the reinforced concrete matrix layer and the cement mortar layer. With continued loading, the arc-shaped crack began to propagate. Two vertical cracks parallel to the loading direction appeared at the center of the reinforced concrete matrix layer surface, gradually expanding to the top of the cement mortar layer. The vertical cracks in Experiment 3 developed faster than in Experiments 1 and 2, exhibiting the fastest development. As the stress level increased, the arc-shaped crack at the junction of the reinforced concrete matrix layer and the cement mortar layer began to detach. The two vertical cracks at the center of the specimen surface began to expand, and the reinforced concrete matrix layer began to shrink, resulting in a smaller overall specimen volume. For safety reasons, loading was stopped when the axial strain of the specimen reached 25%. Among them, the overall volume shrinkage rate of the specimens in Experiments 1-3 showed a decreasing trend, and the overall integrity of the specimens in Experiments 1-3 also showed a decreasing trend. During the stress application process, apart from the differences in various mechanical parameters, the failure modes of the specimens in Experiments 1-3 were basically the same. Specifically, two vertical cracks appeared on the surface of the reinforced concrete matrix layer and the cement mortar layer, the overall volume decreased, bulges appeared on both sides of the cement mortar layer, and detachment occurred at the contact point with the upper bearing plate, indicating relatively high integrity. A schematic diagram of the uniaxial compression failure process of Experiment 1 is shown below. Figure 2 (b) The energy absorption of the specimens in Experiments 1-3 within the strain range of 0-22.5% was 0.937 MPa, 0.892 MPa, and 0.861 MPa, respectively.

[0094] Furthermore, during uniaxial compression, as stress was gradually applied, the specimens in Experiments 4-7 reached their yield strength. Except for Experiment 7, whose yield strength was slightly higher, the yield strengths of Experiments 5-7 were all lower than those of Experiments 1-3. Once the stress reached the specimen's yield strength, multiple cracks appeared at the junction of the reinforced concrete matrix layer and the cement mortar layer, except for Experiment 7. With increasing stress levels, except for Experiment 4, the cracks in Experiments 5-7 expanded rapidly and gradually increased in size, with the cracks in Experiment 5 expanding rapidly. Experiment 6 showed significant lateral deformation, and cracking was evident at the junction of the reinforced concrete matrix layer and the cement mortar layer. Cracking also occurred at the junction of the reinforced concrete matrix layer and the cement mortar layer in Experiment 7. After loading, the failure mode of the specimens in Experiments 4-7 was partial collapse of the central area, with poorer overall integrity than that of Experiments 1-3. The energy absorption of specimens in experimental groups 4-6 within the strain range of 0-19.5% was 0.642 MPa, 0.628 MPa, and 0.685 MPa, respectively, while the energy absorption of specimens in experimental group 7 within the strain range of 0-15.5% was 0.584 MPa.

[0095] In summary, the integrity of the specimens in Experiments 1-7 after complete destruction is much stronger than that of the control group specimens. In addition, the integrity of the specimens in Experiments 1-3 after complete destruction is stronger than that of Experiments 4-7. Among them, the integrity of the specimens in Experiment 1 remains the highest after complete destruction. Therefore, the reinforced concrete matrix material provided in this application can improve the concrete strength and energy absorption buffer performance in underground engineering support systems.

Claims

1. A reinforced concrete matrix material, characterized in that, (1) Cement, fly ash, and sand are mixed, and water is added and stirred to obtain a concrete mixture; the amount of fly ash added is 15% of the weight of cement, the particle size of sand is 0.2-0.5mm, the amount of sand added is 30% of the weight of cement, and the water-cement ratio is 50%; (2) Polyvinyl alcohol fiber, polystyrene particles, antifreeze agent, and waterproofing agent are added to the concrete mixture, and stirred at a stirring speed of 35r / min for 2min. Then, water-reducing agent is added, and stirring is continued for 1.2min to obtain a concrete cement paste; the length of the polyvinyl alcohol fiber is 6mm, the amount of polyvinyl alcohol fiber added is 0.8% of the weight of the concrete mixture, the particle size of the polystyrene particles is 4mm, the volume L of the polystyrene particles added is 7% of the mass kg of the concrete mixture, and the amount of antifreeze added is 15% of the weight of cement. 2%, the amount of the waterproofing agent added is 0.6% of the weight of the concrete mixture, and the amount of the water-reducing agent added is 1% of the weight of the cement; (3) Add foam with a diameter of less than 1 mm obtained by foaming with animal protein foaming agent in two batches to the concrete cement paste. The amount of foam added in the first batch is 23% of the total amount of foam. Stir at a stirring speed of 90 r / min and a stirring time of 3 min. Add the accelerator half a minute before the end of stirring and continue stirring. When no layer of floating foam can be seen on the surface of the paste, foam concrete paste is obtained; the volume L of the foam added accounts for 140% of the weight of the cement kg, and the amount of the accelerator added is 3.5% of the weight of the cement; (4) Cast the foam concrete paste into shape, demold after 48 h, and cure for 28 days to obtain reinforced concrete base material.

2. The application of the reinforced concrete matrix material as described in claim 1 in an underground engineering support system.

3. The application according to claim 2, characterized in that, The aforementioned reinforced concrete matrix material is used in underground engineering support systems to improve concrete strength and provide energy absorption and buffering.

Images