Polypropylene fiber reinforced ultra-fine cement-based grouting full-length anchoring material and preparation method thereof

Abstract

The application belongs to the technical field of grouting materials, and particularly relates to a polypropylene fiber reinforced ultra-fine cement-based grouting full-length anchoring material and a preparation method thereof. The grouting full-length anchoring material comprises 950-1050 mass parts of reference cement, 2-2.5 mass parts of a water reducing agent, 80-100 mass parts of an expanding agent, 35-65 mass parts of a quick-setting agent and 1-7 mass parts of polypropylene fibers. Compared with the existing cement grouting material, the grouting material has high slurry stability, good fluidity, strong injectability, almost no weeping phenomenon, and as an anchoring agent, the grouting material has higher anchoring strength, enhanced coordinated deformation capacity and better durability in the full-length grouting system.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of grouting materials, and particularly relates to a polypropylene fiber reinforced ultra-fine cement-based grouting full-length anchoring material and a preparation method thereof. BACKGROUND

[0002] The shallow coal resources in China are gradually exhausted, and safe and efficient deep well coal mining is the current trend of coal development. However, the geological conditions in China are relatively complex, and when developing deep coal resources, high stress soft rock roadway is relatively widely distributed. In view of the deformation of broken roadway surrounding rock, it is difficult to achieve ideal supporting effect by simply using traditional resin anchoring agent end anchor bolt / anchor cable supporting technology.

[0003] Practice shows that full-length anchoring technology has more advantages in controlling the deformation of surrounding rock and regulating the overall stress, which is mainly due to the bonding of grouting material to the interface of rock and anchor cable, anchor rod and other stress bearing rock, anti-seepage and leakage prevention, etc., so that the full-length anchoring bolt can play a better anchoring effect in engineering practice. Among them, the selection of grouting full-length anchoring material is the key link. At present, the available grouting materials mainly include organic slurry and inorganic slurry. The organic slurry has good injectability, low viscosity and is easy to inject into cracks, but it has defects such as toxicity, high price and low anchoring strength, and high reaction temperature, which can cause coal spontaneous combustion. Compared with the most commonly used cement slurry, the inorganic grouting material has the advantages of high stone strength, strong anti-deformation ability, low reaction temperature, non-toxicity, rich material sources and low cost, and has a wide application prospect in the field of coal mine roadway surrounding rock support.

[0004] However, the current inorganic grouting full-length anchoring material has the following technical defects:

[0005] 1. The slurry stability is poor, and the segregation and precipitation easily occur, and the bleeding phenomenon is serious;

[0006] 2. The mechanical strength of cement solid is low and the toughness is poor, which causes the low slip amount and low pulling strength in the pulling process of the anchoring system, and the overall anchoring performance of the bolt and anchor cable is greatly reduced;

[0007] 3. The traditional cement slurry has obvious dry shrinkage in the solidification process, which reduces the volume of the grouting body, reduces the friction with the borehole, and reduces the bonding strength of the grouting body with the bolt and surrounding rock, which significantly affects the overall bearing capacity of the bolt and anchor cable anchoring system. SUMMARY

[0008] In order to overcome the defects in the prior art, the present application provides a polypropylene fiber reinforced ultra-fine cement-based grouting full-length anchoring material and a preparation method thereof. The present application has the advantages of good fluidity, low shrinkage, low bleeding, high strength, etc., and can be used as an anchoring agent in the field of roadway surrounding rock support.

[0009] To achieve one of the above objectives, the present invention adopts the following technical solution:

[0010] A polypropylene fiber reinforced ultrafine cement-based grouting full-length anchoring material, comprising 950-1050 parts by weight of reference cement, 2-2.5 parts by weight of water-reducing agent, 80-100 parts by weight of expansion agent, 35-65 parts by weight of quick-setting agent and 1-7 parts by weight of polypropylene fiber.

[0011] Preferably, the reference cement is one or more of silicate cements with strength grade 32.5 and strength grade 32.5R.

[0012] Preferably, the silicate cement has a particle size of one or more of 1-5 μm, 5-10 μm, or 10-16 μm, and the specific surface area of ​​the silicate cement is greater than 600 m². 2 / kg, by reducing the cement particle size, the injectability of cement is improved, and it can be injected into microcracks with a crack aperture of less than 20μm.

[0013] Preferably, the water-reducing agent is a polycarboxylate water-reducing agent, the main component of which is a polycarboxylate polymer, with a bulk density of 500-550 g / L, a pH range of 6-8 (25% solution), and a chloride ion concentration of 100 g / L. - The content of ) is less than 0.01%, the appearance is white powder, the solid content is greater than 98%, the water reduction rate is greater than 15%, and it improves the fluidity of cement paste.

[0014] Preferably, the expanding agent is one or more of calcium sulfoaluminate expanding agents, calcium oxide expanding agents, and metal expanding agents; more preferably, it is a calcium sulfoaluminate expanding agent.

[0015] Preferably, the accelerator is one or more of sodium silicate, aluminate accelerator, alkaline earth metal carbonate or alkaline earth metal hydroxide, and alkali-free accelerator; more preferably, sodium silicate or aluminate accelerator can promote the setting and hardening speed of cement and regulate the setting time.

[0016] Preferably, the specific gravity of the polypropylene fiber is 0.7-1.1 g / cm³. 3 It has a melting point of 155-165℃, a tensile strength of 450-550MPa, an elastic modulus of 3800-4000MPa, a length of 1-6mm, and strong alkali resistance.

[0017] To achieve the second objective mentioned above, this invention provides a method for preparing a polypropylene fiber-reinforced ultrafine cement-based grouting full-length anchoring material, comprising the following steps:

[0018] S1. Weigh the raw materials according to the proportions, and grind the reference cement sequentially through crushing and ball milling until the specific surface area is greater than 600 m². 2 / kg;

[0019] S2. Place the weighed quick-setting agent, expanding agent, water-reducing agent, polypropylene fiber, and reference cement from step S1 into a powder mixer and mix for 5-8 minutes. After thorough mixing, the grouting anchoring material for the entire length is obtained.

[0020] The advantages of this invention are:

[0021] (1) The grouting anchoring material prepared by the present invention uses silicate cement as the base material. After mechanical activation treatment, the particle size is reduced and the specific surface area is increased. Under the action of water-reducing agent, expansion agent and quick-setting agent, the water consumption is reduced, the grout fluidity is improved, the volume shrinkage is suppressed, and the setting time is controllable.

[0022] (2) The reference cement of the present invention is mainly composed of compounds such as MgO, Al2O3, SiO2, CaO, Fe2O3, C3S, and C3A. The content of SiO2 in the cement is between 15% and 30%, the content of Al2O3 is between 3% and 7.5%, and the Al2O3 / SiO2 ratio is between 0.2 and 0.25. This invention utilizes the hydration reaction mechanism of silicate cement to react four main clinker minerals—tricalcium silicate, dicalcium silicate, tricalcium aluminate, and iron-phase solid solution—with water to generate hydration products such as hydrated calcium silicate, calcium hydroxide, hydrogarnet, ettringite, and monosulfide-type hydrated calcium sulfoaluminate. The grout gradually solidifies and hardens from a plastic slurry into a hard cement stone. The silicate cement is crushed and ground to achieve a high specific surface area and small particle size, giving the raw materials better fluidity and injectability into surrounding rock fissures, and improving reactivity. A quick-setting agent promotes the hydration reaction of the reference cement and controls the setting time of the grouting anchor material. A polycarboxylate superplasticizer reduces agglomeration by adhering to the surface of cement particles, thus reducing water consumption. An expansive agent reduces the drying shrinkage effect of cement, achieving micro-expansion characteristics and improving the bonding strength between the material and the surrounding rock interface.

[0023] (3) In this invention, polypropylene fiber is selected as a toughening material to enhance and toughen the cement-based grout. The compressive strength of the grout reaches 44.6 MPa after 3 days and 61.1 MPa after 14 days. The flexural strength after 3 days is 8.59 MPa, showing significantly enhanced mechanical properties. Polypropylene fiber can bridge the hydration gel products, inhibit the stress expansion caused by gel expansion, improve the strength and stone rate of the grouting material, and prevent the expansion of existing defects (microcracks) in the matrix and delay the appearance of new cracks, effectively improving the toughness and durability of the cement-based full-length anchoring system. In addition, during the cement hydration process, the water-reducing agent, expansion agent, quick-setting agent and polypropylene fiber of this invention will also have a synergistic coupling effect, jointly promoting the hydration reaction process and further improving the coordinated deformation capacity of the full-length anchoring system.

[0024] (4) Compared with existing cement grouting materials, the present invention has high grout stability, good fluidity, strong injectability, and almost no bleeding phenomenon. As an anchoring agent, it exhibits higher anchoring strength, enhanced coordinated deformation ability and better durability in the full-length grouting system.

[0025] (5) The preparation process of this invention is simple, does not involve complex operations, has a wide range of raw material sources, is low in cost, and has excellent product performance. It is suitable for the fields of anchor bolt / anchor cable full-length anchoring, soft rock tunnel grouting reinforcement, split grouting, tunnel filling and repair technology.

[0026] (6) Traditional silicate cement slurry, as the most typical inorganic grouting material, is favored due to its low price, good durability, and high aggregate strength. However, it suffers from problems such as poor injectability, low early strength, long setting time, poor volume stability, and large particle size, making it difficult to inject into the fine pores of the surrounding rock. This invention modifies the physicochemical properties of silicate cement slurry to obtain a high-quality cement-based grouting material with good injectability, volume stability, controllable setting time, and high anchoring force, thereby meeting the engineering requirements of current full-length anchoring technology. Attached Figure Description

[0027] Figure 1 The XRD patterns are of the 3d structures of the polypropylene fiber reinforced ultrafine cement-based grouting full-length anchoring materials prepared in Examples 1-4 of this invention.

[0028] Figure 2 The images are SEM images of the 3D structures of the polypropylene fiber-reinforced ultrafine cement-based grouting full-length anchoring materials prepared in Examples 1-4 of this invention.

[0029] Figure 3 The FTIR spectra of the 3d structures of the polypropylene fiber-reinforced ultrafine cement-based grouting full-length anchoring materials prepared in Examples 1 and 2 of this invention are shown.

[0030] Figure 4Optical photographs of the polypropylene fiber-reinforced ultrafine cement-based grouting full-length anchoring materials prepared in Examples 1-4 of this invention in a mold.

[0031] Figure 5 The flowability test diagrams are for the polypropylene fiber reinforced ultrafine cement-based grouting full-length anchoring materials prepared in Examples 1-4 of this invention.

[0032] Figure 6 Cross-sectional photographs of the 7-day structures of the polypropylene fiber-reinforced ultrafine cement-based grouting full-length anchoring materials prepared in Examples 1-4 of this invention.

[0033] Figure 7 The polypropylene fiber-reinforced ultrafine cement-based grouting full-length anchoring material prepared in Examples 1-4 of this invention was used as an anchoring agent in the load-slip results of the indoor simulated full-length anchoring pull-out test of the surrounding rock matrix.

[0034] Figure 8 Using the polypropylene fiber reinforced ultrafine cement-based grouting full-length anchoring material prepared in Examples 1-4 of this invention as an anchoring agent, the performance characteristics of the full-length anchored specimen in the pull-out test of the surrounding rock matrix were simulated: (a) mechanical parameter characteristics, (b) corresponding growth characteristics of peak load and slip.

[0035] Figure 9 The polypropylene fiber-reinforced ultrafine cement-based grouting full-length anchoring material prepared in Examples 1-4 of this invention was used as an anchoring agent to simulate the acoustic emission ring count and energy characteristics of the full-length anchored specimen in the pull-out test of the surrounding rock matrix.

[0036] Figure 10 (a) Using the polypropylene fiber reinforced ultrafine cement-based grouting full-length anchoring material prepared in Examples 1-4 of the present invention as an anchoring agent, the peak load corresponding time and cumulative acoustic emission energy characteristics of the full-length anchored specimen in the pull-out test of the surrounding rock matrix were simulated. (b) The peak load corresponding time growth characteristics of Examples 1-4 of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the following description is provided in conjunction with the appendix. Figures 1-4 The present invention will be further described in detail with reference to the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0038] Example 1

[0039] A control group of ultrafine cement-based grouting anchoring material without polypropylene fiber comprises the following components in parts by weight: 1000 parts by weight of reference cement (32.5R silicate cement), 2.5 parts by weight of water-reducing agent (polycarboxylate high-efficiency water-reducing agent), 90 parts by weight of expansion agent (calcium sulfoaluminate expansion agent), and 50 parts by weight of quick-setting agent (sodium silicate).

[0040] A method for preparing a control group of ultrafine cement-based grouting full-length anchoring material without polypropylene fiber doping is described below:

[0041] First, the silicate cement is crushed and ground in a ball mill until it has a specific surface area of ​​600 m². 2 / kg, particle size 10μm; weigh silicate cement, quick-setting agent, expansion agent and polycarboxylate superplasticizer raw materials according to a certain preparation ratio, add them to the powder mixer, stir for 5 minutes, mix thoroughly and then package for use.

[0042] Example 2

[0043] A polypropylene fiber reinforced ultrafine cement-based grouting full-length anchoring material comprises the following components in parts by weight: 1000 parts by weight of reference cement (32.5R silicate cement), 2.5 parts by weight of water-reducing agent (polycarboxylate high-efficiency water-reducing agent), 90 parts by weight of expansion agent (calcium sulfoaluminate expansion agent), 50 parts by weight of quick-setting agent (sodium silicate), and 1 part by weight of polypropylene fiber (3 mm in length).

[0044] A method for preparing a polypropylene fiber-reinforced ultrafine cement-based grouting full-length anchoring material, the specific steps of which are as follows:

[0045] First, the silicate cement is crushed and ground in a ball mill until it has a specific surface area of ​​600 m². 2 / kg, particle size 10μm; weigh silicate cement, quick-setting agent, expanding agent, polycarboxylate superplasticizer and polypropylene fiber raw materials according to a certain preparation ratio, add them to the powder mixer, stir for 5 minutes, mix thoroughly and then package for use.

[0046] Example 3

[0047] A polypropylene fiber reinforced ultrafine cement-based grouting full-length anchoring material comprises the following components in parts by weight: 1000 parts by weight of reference cement (32.5 silicate cement), 2 parts by weight of water-reducing agent (polycarboxylate high-efficiency water-reducing agent), 100 parts by weight of expansion agent (calcium oxide expansion agent), 60 parts by weight of quick-setting agent (sodium silicate), and 4 parts by weight of polypropylene fiber (3 mm in length).

[0048] A method for preparing a polypropylene fiber-reinforced ultrafine cement-based grouting full-length anchoring material, the specific steps of which are as follows:

[0049] First, the silicate cement is crushed and ground in a ball mill until it has a specific surface area of ​​600 m². 2 / kg, particle size 10μm; weigh silicate cement, quick-setting agent, expanding agent, polycarboxylate superplasticizer and polypropylene fiber raw materials according to a certain preparation ratio, add them to the powder mixer, stir for 5 minutes, mix thoroughly and then package for use.

[0050] Example 4

[0051] A polypropylene fiber reinforced ultrafine cement-based grouting full-length anchoring material comprises the following components in parts by weight: 1050 parts by weight of reference cement (32.5 silicate cement), 2.5 parts by weight of water-reducing agent (polycarboxylate high-efficiency water-reducing agent), 90 parts by weight of expansion agent (metal expansion agent), 45 parts by weight of quick-setting agent (sodium silicate), and 7 parts by weight of polypropylene fiber (6 mm in length).

[0052] A method for preparing a polypropylene fiber-reinforced ultrafine cement-based grouting full-length anchoring material, the specific steps of which are as follows:

[0053] First, the silicate cement is crushed and ground in a ball mill until it has a specific surface area of ​​600 m². 2 / kg, particle size 10μm; weigh silicate cement, quick-setting agent, expanding agent, polycarboxylate superplasticizer and polypropylene fiber raw materials according to a certain preparation ratio, add them to the powder mixer, stir for 5 minutes, mix thoroughly and then package for use.

[0054] The testing process and data of the polypropylene fiber-reinforced ultrafine cement-based grouting full-length anchoring materials prepared in Examples 1-4 are as follows:

[0055] I. Preparation of the test slurry

[0056] With a water-cement ratio of 0.35, the control group of ultrafine cement-based grouting full-length anchoring material prepared in Example 1, the polypropylene fiber reinforced ultrafine cement-based grouting full-length anchoring material prepared in Examples 2-4, and water were added to a container in sequence. After stirring at low speed for 120s, stirring was stopped for 15s, and then stirred at high speed for 120s to prepare cement-based composite slurry.

[0057] II. Determination of Slurry Water Separation Rate

[0058] Take 100 mL of the composite slurry prepared in Examples 1-4 and pour it into three graduated cylinders. After standing for 60 min, read the scale reading corresponding to the interface between the upper clear water and the lower slurry and record it. Repeat the above steps and perform two measurements. Finally, take the average value.

[0059] III. Determination of slurry setting time

[0060] According to the "Standard Consistency Water Requirement, Setting Time and Soundness Test Method for Cement" (GB / T1346-2011), the setting time of the slurry was tested. The time from when all the ultrafine cement was added to the water until it reached the initial setting state and the final setting state were respectively expressed in minutes.

[0061] IV. Determination of Slurry Flowability

[0062] The flowability test of cement paste was conducted using a truncated conical mold. Cement paste was poured into the mold (the small circle at the top had a diameter of 36 mm, the large circle at the bottom had a diameter of 60 mm, and the height was 60 mm). After filling, the mold was pressed down to ensure complete filling, leveled, and then lifted vertically, slowly, and steadily. When the paste stopped flowing and began to expand, the diameters of the two conical molds in opposite directions were measured, and the average value was taken as the flowability.

[0063] V. Determination of Strength and Volume Stability of Full-Length Grouting Anchorage Material

[0064] The slurry was poured into 40×40×160mm molds, placed horizontally in a curing chamber, and cured for 24 hours before demolding. The molds were then placed at 20℃±1℃ and 95% relative humidity for further curing. Mechanical properties were tested after curing at different ages (3d±2h, 14d±2h, 28d±2h).

[0065] The test results are shown in Table 1 below:

[0066] Table 1

[0067]

[0068]

[0069] The products obtained in Examples 1-4 were characterized in terms of structure, microstructure, and properties. Specifically, X-ray powder diffraction (XRD) was used to test the crystal structure of Examples 1-4; scanning electron microscopy (SEM) was used to observe the microstructure of Examples 1-4; Fourier transform spectroscopy (FTIR) was used to test the surface functional group characteristics of Examples 1-2; the flowability of cement paste was tested using a truncated conical mold; and cylindrical surrounding rock specimens with a diameter of 200 mm and a height of 300 mm were prepared using cement, sand, and tap water as similar material proportions at a mass ratio of 1:0.7:0.5. A 32mm diameter central borehole is drilled as the base part of the full-length anchoring structure. A 22mm diameter and 400mm long mining anchor cable is inserted into the pre-drilled hole in the base. The cement grouting full-length anchoring material prepared in Examples 1-4 is prepared, stirred evenly, and injected into the rod body and surrounding rock gaps until the entire base is filled to achieve full-length anchoring of the anchor rod. After curing for 18 days, a pull-out test is carried out. The mechanical bearing characteristics of the full-length anchoring structure are tested using a universal testing machine, and the deformation characteristics and acoustic emission characteristics of the full-length anchoring structure during the pull-out process are tested using an acoustic emission measurement system.

[0070] from Figure 1 It can be seen that the characteristic diffraction peaks of the hydration products calcium silicate hydrate gel (CSH), calcium hydroxide (Ca(OH)2), ettringite (AFt), and sulfoaluminate (AFm) in cement can be observed, and these products together provide the mechanical strength of the product.

[0071] from Figure 2 It can be seen that, compared with the control sample of Example 1 without polypropylene fiber, the cement-bound density of the grouting materials prepared in Examples 2-4 is significantly improved, and the size of hydration products such as hydrated calcium silicate, calcium hydroxide, and ettringite is significantly increased. Due to the short hydration time, some unhydrated cement particles are still present between the gel clusters. At the same time, the hydration products are clearly wrapped with slender and coarse polypropylene fibers, and the interweaving effect of polypropylene fibers in the hydration products is enhanced with the increase of the dosage. A large amount of cement hydration products are bonded to the surface of the polypropylene fibers, indicating that they have a good bonding effect.

[0072] from Figure 3 It can be seen that the absorption peak positions of the hydration products of the cement-based materials before and after polypropylene fiber doping are consistent, indicating that the doping of polypropylene fibers did not change the product composition. In the hydration products of the full-length grouting anchoring materials prepared in Examples 1 and 2, obvious ettringite characteristic absorption bands appeared. The wavelength was 2920 cm⁻¹. -1 The absorption peak can be attributed to the asymmetric stretching vibration of —CH2—, 3450 cm⁻¹ -1 and 1630cm -1 The two absorption peaks that appeared were from free water OH. -Vibration and lattice water OH - Bending vibration, 1430cm -1 The absorption peak observed at 1010 cm⁻¹ can be attributed to the antisymmetric stretching vibration of the C-O bond in the hydration product. -1 The absorption peak at 877 cm⁻¹ is due to the stretching vibration of Al-OH in gibbsite. -1 The absorption peak at that point represents the stretching vibration of the Al-O group.

[0073] from Figure 4 As can be seen from the optical photographs of the grouting materials in Examples 1 and 2-4 when they were injected into the mold, they show good uniformity and flowability.

[0074] from Figure 5 It can be seen that when the grouting materials of Examples 1 and 2-4 were tested for fluidity, the diameters of the grout forming circles were 206 mm, 225 mm, 210 mm, and 216 mm, respectively. The larger the grout diameter, the greater the fluidity. The results show that the ultrafine cement-based grouting materials, before and after polypropylene fiber doping, both have good grout flow characteristics. Meanwhile, Example 2 showed the best fluidity. Fluidity is closely related to injectability; the better the fluidity, the better the injectability of the grout, and the easier it is to inject into the cracks or pores of the matrix material.

[0075] from Figure 6 As can be seen, compared with Example 1, the pores and cracks in the hardened solid cross-section of the grouting materials prepared in Examples 2-4 are significantly reduced, indicating enhanced compactness. Meanwhile, with the increase of polypropylene fiber content in the matrix, more bridging fibers are clearly observed bonded within the hydration products at the cross-section.

[0076] from Figure 7It can be seen that in the pull-out tests, the loads of the four full-length anchored substrates prepared in Examples 1 and 2-4 showed a trend of first increasing and then decreasing with increasing displacement. The entire load-bearing process can be roughly divided into four stages: chemical debonding stage, microcrack propagation stage, shear failure stage, and friction failure stage. In Example 1, the post-peak load of the slip curve dropped rapidly and quickly reached zero, indicating low residual load-bearing capacity. In contrast, the post-peak load reduction slope of the full-length anchored specimens in Examples 2-4 was significantly slower, indicating enhanced post-peak load-bearing characteristics, especially Example 4, which showed the best residual load-bearing capacity. Meanwhile, the loads of the four full-length anchored specimens prepared in Examples 1-4 entering the friction failure stage were 3.88 kN, 13.7 kN, 4.2 kN, and 1.84 kN, respectively. Compared with Example 1, the pull-out load of the full-length anchorage specimens based on Examples 2 and 3 when entering the friction failure stage was significantly increased. This can be attributed to the fact that the doping of polypropylene fibers in the full-length anchorage material not only enhances the roughness of the failure anchorage interface and strengthens the friction effect at the failure interface, but also effectively improves the mechanical chain effect at the interface and suppresses the shear failure of the anchorage interface.

[0077] from Figure 8 It can be seen that the pull-out loads of the four full-length anchoring substrates prepared in Examples 1 and 2-4 were 27.78 kN, 37.68 kN, 28.9 kN, and 27.1 kN, respectively, with slip values ​​of 3.46 mm, 5.16 mm, 3.08 mm, and 18.46 mm, respectively. Compared with the control group of Example 1 without polypropylene fiber, the peak loads of Examples 2-4 increased by 1.36, 1.04, and 0.98 times, respectively, with corresponding slip value increases of 1.49, 0.89, and 5.34 times, respectively. The results show that appropriate polypropylene fiber doping can significantly enhance the load-bearing characteristics and failure resistance of the full-length anchoring system of ultrafine cement-based grouting materials, especially Example 2, which showed the best mechanical load-bearing performance. Furthermore, the higher the polypropylene fiber content in the grouting material, the greater the slip value corresponding to the pull-out load of the full-length anchoring substrate, indicating that the microcrack propagation rate at the full-length anchoring interface is slower, and the coupling of polypropylene fibers effectively inhibits or delays the development of microcracks at the anchoring interface.

[0078] from Figure 9It can be seen that the acoustic emission ring count distribution characteristics, acoustic emission activity intensity, and stress of the four full-length anchored substrates prepared in Examples 1 and 2-4 show a certain correspondence, reflecting the specimen's ability to resist failure. In the initial stage of pull-out loading, the acoustic emission ring count is relatively low, and the cumulative acoustic emission energy increases slowly. As the load increases, the acoustic emission activity gradually intensifies, the ring count gradually increases, and the cumulative energy grows rapidly and non-linearly. At this point, new microcracks begin to appear at the anchoring interface. With the continuous increase of the bearing pressure, the interface microcracks continuously develop, expand, and even gradually penetrate, resulting in cracking phenomena on the specimen surface. As the load further increases and the anchoring interface continues to break down, the specimen gradually loses its bearing capacity. Consequently, the acoustic emission activity gradually weakens, the ring count decreases, and the growth rate of the cumulative acoustic emission energy gradually weakens. When the stress reaches its maximum value, it drops rapidly. At this point, the specimen fails completely, the acoustic emission signal rapidly attenuates, and the cumulative acoustic emission energy hardly changes anymore.

[0079] from Figure 10 It can be seen that under pull-out load, the peak load times for the full-length anchorage substrates prepared in Examples 1 and 2-4 are 117.72s, 193.09s, 148.78s, and 140.16s, respectively, with corresponding cumulative acoustic emission energies of 74.918 × 10⁻⁶. 4 mV·mS, 94.66×10 4 mV·mS, 30.90×10 4 mV·mS and 83.19×10 4 Compared to Example 1, the peak load of the full-length anchorage specimens in Examples 2-4 was significantly increased, and the time corresponding to the peak load was also significantly increased, with the time corresponding to the peak load increasing by 1.64, 1.26, and 1.19 times, respectively. The results indicate that the full-length anchorage specimens based on polypropylene fiber-doped ultrafine cement-based composite grouting material not only exhibit excellent mechanical bearing characteristics but also significantly improve the durability of the anchorage system.

[0080] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A polypropylene fiber-reinforced ultrafine cement-based grouting full-length anchoring material, characterized in that, The grouting anchoring material consists of the following raw materials in parts by weight: 950-1050 parts by weight of reference cement, 2-2.5 parts by weight of water-reducing agent, 80-100 parts by weight of expansion agent, 35-65 parts by weight of quick-setting agent, and 1-7 parts by weight of polypropylene fiber; the length of the polypropylene fiber is 1-6 mm. The reference cement is one or more of silicate cements with strength grade 32.5 and strength grade 32.5R; The silicate cement is crushed and ground to a specific surface area greater than 600 m². 2 / kg, and its particle size is 10-16μm.

2. The polypropylene fiber reinforced ultrafine cement-based grouting full-length anchoring material according to claim 1, characterized in that: The water-reducing agent is a polycarboxylate water-reducing agent.

3. The polypropylene fiber reinforced ultrafine cement-based grouting full-length anchoring material according to claim 1, characterized in that: The expanding agent is one or more of the following: calcium sulfoaluminate expanding agent, calcium oxide expanding agent, and metal expanding agent.

4. The polypropylene fiber reinforced ultrafine cement-based grouting full-length anchoring material according to claim 1, characterized in that: The quick-setting agent is one or more of sodium silicate, aluminate quick-setting agent, alkaline earth metal carbonate or alkaline earth metal hydroxide, and alkali-free quick-setting agent.

5. The polypropylene fiber reinforced ultrafine cement-based grouting full-length anchoring material according to claim 1, characterized in that: The specific gravity of the polypropylene fiber is 0.7-1.1 g / cm³. 3 It has a melting point of 155-165℃, a tensile strength of 450-550MPa, and an elastic modulus of 3800-4000MPa.

6. A method for preparing a polypropylene fiber-reinforced ultrafine cement-based grouting full-length anchoring material as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Weigh the raw materials according to the proportions, and grind the reference cement sequentially through crushing and ball milling until the specific surface area is greater than 600 m². 2 / kg; S2. Place the weighed quick-setting agent, expanding agent, water-reducing agent, polypropylene fiber, and reference cement from step S1 into a powder mixer and mix for 5-8 minutes. After thorough mixing, the grouting anchoring material for the entire length is obtained.

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