A fiber-reinforced geopolymer composite material, and a method of making and using the same

Abstract

The application discloses a kind of fiber reinforced geopolymer composite material and its preparation method and application, belong to geopolymer material technical field.The application takes red mud and blast furnace slag as main cementing material, combines bamboo fiber and sisal fiber, constructs plant fiber reinforced geopolymer mortar green composite system, and the influence law of alkali equivalent, fiber type and fiber content on the statics performance of material is systematically analyzed.The difference of the reinforcing effect of bamboo fiber and sisal fiber is compared and studied, and it is found that sisal fiber has more advantages in crack inhibition, energy dissipation toughening and impact resistance performance improvement, which provides a basis for fiber selection of plant fiber reinforced geopolymer material.Combining with SHPB test, drop hammer impact test, the impact resistance performance of plant fiber geopolymer material is systematically evaluated from material, specimen to component level, and the sisal fiber geopolymer material provided by the application has potential application value in impact resistance engineering components.

Description

Technical Field

[0001] This invention belongs to the field of geopolymer materials technology, and in particular relates to a fiber-reinforced geopolymer composite material, its preparation method and application. Background Technology

[0002] During tunnel operation and maintenance, drainage manhole covers often require frequent manual opening and repositioning to meet the inspection and repair needs of the underground drainage system. During repeated "lifting and placing" operations, the edges of ordinary concrete manhole covers are easily impacted, leading to localized stress concentration and problems such as edge damage, breakage, and crack propagation. Simultaneously, the tunnel interior is subjected to complex environmental conditions including water seepage, wet-dry cycles, and aging drainage systems, making the concrete structure prone to durability defects such as cracking, leakage, and surface spalling.

[0003] Compared to traditional silicate cement concrete, geopolymer concrete typically exhibits higher mechanical strength and demonstrates excellent high-temperature resistance, good thermal insulation, a stable and adjustable coefficient of thermal expansion, and superior resistance to acid corrosion and fire. Leveraging these advantages, geopolymer materials have found applications in grouting reinforcement, rapid repair, and concrete engineering, showing promising development prospects.

[0004] In recent years, with the deepening research on green building materials, geopolymer materials have gradually received widespread attention from the academic and engineering communities, and their development and application research are increasing. These materials have shown good application potential in multiple fields, and plant fibers, as an environmentally friendly and economical fiber, can indeed improve the mechanical properties of concrete or cement mortar, enhance their ductility, and meet more construction requirements. However, in actual engineering applications, the promotion of related materials is often mainly based on laboratory test indicators for evaluation and use. Overall, there is still a lack of systematic and comprehensive industry standards and technical specifications for fiber-reinforced geopolymer materials, therefore, more in-depth research is urgently needed to promote the establishment of relevant standard systems and the development of engineering applications. Research on the ductility and impact resistance of plant fiber geopolymer mortar materials is limited. Domestic research mainly focuses on the impact resistance of plant fibers and concrete materials, with little clarification on the amount of impact energy absorbed by new mortar materials and their failure modes. Regarding methods combining both, research on the mechanical properties and impact resistance of new specimens is scarce in domestic literature. Therefore, further research into the effects of bamboo fiber and sisal fiber on increasing the impact resistance of geopolymers is of great significance for the study of mechanical properties and durability. Summary of the Invention

[0005] To address the above problems, this invention provides a fiber-reinforced geopolymer composite material, its preparation method, and its applications.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a fiber-reinforced geopolymer composite material comprising the following raw materials: precursor materials, quartz sand, plant fibers and composite alkali activator; the precursor materials include red mud and blast furnace slag; the plant fibers are selected from sisal fibers or bamboo fibers.

[0007] Furthermore, the fiber-reinforced geopolymer composite material has a sand-to-cement ratio (mass ratio of quartz sand to cementitious material) of 0.36 and an alkali-to-cement ratio (mass ratio of composite alkali activator to cementitious material) of 0.55.

[0008] Furthermore, the composite alkali activator comprises sodium silicate solution, sodium hydroxide, and water, and the modulus of the composite alkali activator is 1.4.

[0009] Furthermore, the sisal fiber has an average length of 18 mm, an average diameter of 0.40 µm, an ultimate elongation of 3.6%, a breaking strength of 11.3 cN / dtex, and a breaking force of 568 cN. The bamboo fiber has an average length of 20 mm, an average diameter of 0.22 µm, an ultimate elongation of 3.4%, a breaking strength of 6.7 cN / dtex, and a breaking tensile strength of 372 cN.

[0010] Sisal fiber is a common natural plant fiber material, derived from the leaves of the sisal plant. This fiber possesses high strength and good abrasion resistance, while also exhibiting strong resistance to salt and alkali and corrosion. Introducing sisal fiber into building materials systems not only aligns with the development direction of green building materials but also provides a new way to utilize this renewable resource, playing a positive role in reducing energy consumption and alleviating environmental pollution. The sisal fiber used in this invention has an initial length of approximately 1600 mm and a diameter ranging from 0.15 to 0.20 mm. Before the formal experiment, the fiber needs to be combed to disperse the fiber bundles, and then manually cut to the required experimental length of 18 mm using scissors. 2mm.

[0011] As a reinforcing material derived from natural plants, bamboo fiber possesses high mechanical properties, along with advantages such as strong resource sustainability, relatively low price, and short growth cycle, making it a promising candidate for application in cement-based composite materials. The bamboo fiber used in this invention is prepared from moso bamboo, with an initial length of approximately 164 mm and a diameter ranging from 0.18 to 0.25 mm. Before the experiment, the bamboo fiber needs to be combed to ensure uniform fiber dispersion, and then cut to the required length using scissors.

[0012] Furthermore, the red mud and blast furnace slag account for 20% and 80% of the mass of the precursor material, respectively.

[0013] Furthermore, the plant fiber accounts for 0.5-1.0% of the fiber-reinforced geopolymer composite material, and the alkali equivalent of the fiber-reinforced geopolymer composite material is 8-10%.

[0014] Furthermore, when the plant fiber is sisal fiber, it accounts for 1.0% of the fiber-reinforced geopolymer composite material, and the alkali equivalent of the fiber-reinforced geopolymer composite material is 9%.

[0015] Secondly, the present invention provides a method for preparing the fiber-reinforced geopolymer composite material, comprising the following steps: weighing red mud, blast furnace slag, quartz sand, plant fiber and composite alkali activator respectively; mixing the red mud and blast furnace slag evenly for the first time; adding the composite alkali activator; mixing evenly a second time; adding quartz sand; mixing evenly a third time; adding plant fiber; mixing evenly a fourth time; pouring the slurry into a mold; compacting the slurry; leveling the slurry; covering it with plastic wrap; allowing it to stand at room temperature; demolding the slurry; and curing the slurry after demolding.

[0016] Thirdly, the present invention provides an application of the fiber-reinforced geopolymer composite material described above in the construction of drainage well covers.

[0017] Compared with the prior art, the present invention has the following advantages and technical effects: This invention uses red mud and blast furnace slag as the main cementing materials, combined with bamboo fiber and sisal fiber, to construct a green composite system of plant fiber reinforced geopolymer mortar. The influence of alkali equivalent, fiber type, and fiber content on the static properties of the material was systematically analyzed. A comparative study of the reinforcing effects of bamboo fiber and sisal fiber revealed that sisal fiber has greater advantages in crack suppression, energy dissipation toughening, and impact resistance improvement, providing a basis for fiber selection in plant fiber reinforced geopolymer materials. Combining SHPB and drop hammer impact tests, the impact resistance of the plant fiber geopolymer material was systematically evaluated from the material, specimen, and component levels. The sisal fiber geopolymer material provided by this invention has potential application value in impact-resistant engineering components. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly described below.

[0019] Figure 1 The flowchart shows the processing of sisal fibers, where (a) raw sisal fibers, (b) combed fibers, (c) sheared fibers, and (d) ready for testing. Figure 2 The flowchart shows the processing of bamboo raw fibers, where (a) raw bamboo raw fibers, (b) combed fibers, (c) sheared fibers, and (d) ready for testing. Figure 3 This is a flowchart of the experiment in Example 1; Figure 4 This represents the typical failure mode of FRGC under tensile stress. Figure 5 The variation law of ultimate tensile strain of each specimen under different variable conditions; Figure 6 These represent the ultimate compressive strength of FRGC under different alkali equivalents in 3D. Figure 7 The values ​​represent the ultimate compressive strength of FRGC under different alkali equivalents at 7D. Figure 8 The ultimate compressive strength of FRGC under different alkali equivalents at 28D is shown below. Figure 9 The ultimate compressive strength of specimens with different fiber types and fiber content in 3D; Figure 10 The ultimate compressive strength of specimens with different fiber types and fiber content in 7D; Figure 11 The ultimate compressive strength of specimens with different fiber types and fiber content at 28D; Figure 12 Schematic diagram of a split Hopkinson strut; Figure 13 Stress / strain rate-strain curves for (a) JM-10%-1%, (b) JM-9%-1%, (c) ZY-9%-1% and (d) CG-9%; Figure 14 Stress / strain rate-strain curves for (a) C25, (b) RC25, (c) JM and (d) ZY / CG; Figure 15 This is a schematic diagram of the specimen for the drop hammer test; Figure 16 The failure modes of the specimens in the drop hammer test are (a) JM-9%-1%, (b) plain concrete, and (c) reinforced concrete. Figure 17In the table, (a) represents the maximum displacement of the top surface of the plain concrete, (b) represents the maximum displacement of the bottom surface of the plain concrete, (c) represents the maximum displacement of the top surface of the reinforced concrete, and (d) represents the maximum displacement of the bottom surface of the reinforced concrete. Figure 18 (a) Maximum displacement value of the top surface of the geopolymer (JM-9%-1%), (b) Maximum displacement value of the bottom surface of the geopolymer, (c) Comparison of maximum displacement values ​​of concrete, reinforced concrete and geopolymer, (d) Comparison of peak impact force of concrete, reinforced concrete and geopolymer. Detailed Implementation

[0020] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0021] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0022] The room temperature in this invention refers to 25±2℃.

[0023] The red mud used in the embodiments of the present invention is Bayer process red mud produced by Shandong Yizhu Foundry Materials Factory. Table 1 shows the chemical composition (wt.%) of the red mud.

[0024] The slag is supplied by Henan Borun Foundry Materials Co., Ltd. in two specifications: S95 and S105. The chemical composition of the slag is shown in Table 2 (Main Physical Indicators and Chemical Composition of S95 Blast Furnace Slag) and Table 3 (Main Physical Indicators and Chemical Composition of S105 Blast Furnace Slag).

[0025] The quartz sand comes from Runjia Quartz Sand Factory, and its basic physical properties are shown in Table 4.

[0026] A composite alkaline activator was used, comprising sodium silicate solution (water glass), flake solid sodium hydroxide, and tap water. The sodium silicate solution was produced by Jiangsu Wuxi Yourui Building Materials Co., Ltd., with a modulus of 3.3, classifying it as a weakly alkaline water glass solution. The sodium hydroxide was a flake solid reagent produced by Guangdong Dongguan Xilong Science Co., Ltd., with a purity of 96%. Table 5 shows the physicochemical properties (wt.%) of the sodium silicate solution.

[0027] The sisal fibers used were sourced from raw materials provided by Qiancong Hemp Rope and Xu Wangfeng Garment Accessories Company. Their original length was approximately 1600 mm, and their diameter ranged from 0.15 to 0.20 mm. The preparation process is detailed below. Figure 1 The process flow chart for sisal fiber processing includes (a) raw sisal fiber, (b) carded fiber, (c) sheared fiber, and (d) ready for testing. Performance parameters are shown in Table 6, Performance Indicators of Sisal Fiber.

[0028] The bamboo fiber used was provided by Jiangxi Zhuxin New Material Technology Co., Ltd., and the raw material is bamboo fiber prepared from moso bamboo. The preparation process is detailed below. Figure 2 The process flow chart for bamboo raw fiber processing includes (a) raw bamboo raw fiber, (b) combed fiber, (c) sheared fiber, and (d) ready for testing. Performance indicators are shown in Table 7.

[0029] Table 1 Table 2 Table 3 Table 4 Table 5 Table 6 Table 7 In this embodiment of the invention, the modulus of sodium silicate-type water glass is adjusted by adding sodium hydroxide solution. The modulus refers to the molar ratio of SiO2 to Na2O in the water glass system. Before preparing the fiber-reinforced geopolymer composite material, an alkali activation solution needs to be prepared approximately 4-5 hours in advance, according to the alkali equivalent and activator modulus requirements, and thoroughly stirred with a glass rod to ensure uniform mixing.

[0030] Example 1 The specific steps for preparing the fiber-reinforced geopolymer composite material (FRGC) in this embodiment are as follows: (1) Material preparation: Weigh out red mud, blast furnace slag (including S95 slag content and S105 slag content), quartz sand, sisal fiber and bamboo fiber respectively, fix the sand-to-binder ratio (0.36), alkali-to-binder ratio (0.55), red mud content (20%, mass percentage in the precursor), S95 blast furnace slag content (35%, mass percentage in the precursor), S105 blast furnace slag content (45%, mass percentage in the precursor) and composite alkali activator (modulus of 1.4), and design different mix proportion schemes with fiber type, fiber content and alkali equivalent as variables (see Table 8); (2) Material mixing: Red mud and blast furnace slag powder materials are put into the mixing equipment for dry mixing to make them fully and evenly mixed. After the dry materials are evenly mixed, the pre-prepared composite alkali activator is slowly added and the mixing continues to be carried out to make the powder and the activating liquid initially combine. Then, quartz sand is gradually added and the mixing continues to be carried out to make the system further evenly dispersed. Finally, the pre-weighed fiber material is artificially pre-dispersed to avoid the fiber from agglomerating during the mixing process. Then it is added to the mixing pot and the mixing time is appropriately extended to ensure that the fiber is evenly distributed in the matrix. (3) Specimen molding: Pour the mixed slurry into a pre-prepared mold and compact it using a vibrating table to remove internal air bubbles and voids, thereby increasing the density of the specimen. After compaction, smooth the surface of the specimen and cover it with a layer of plastic wrap to reduce direct contact between the specimen and the outside air; (4) Demolding of specimens: After the specimens have been left to stand at room temperature for about 24 hours, they are demolded. When the ambient temperature is low, the demolding time can be extended appropriately to ensure that the specimens have sufficient initial strength.

[0031] (5) Curing of specimens: After demolding, the specimens should be placed in a standard curing chamber for curing. The curing environment temperature should be controlled at 20±2℃ and the relative humidity should be maintained at 90%±5% until the specified age is reached before subsequent performance monitoring. Figure 3 This is a flowchart of the experiment in Example 1.

[0032] Table 8 Note: The sisal fiber, bamboo fiber content, and precursor materials in the table are all mass ratios. Mixing ratio naming: CG indicates the fiber-free group; JM8%-0.5% indicates an alkali equivalent of 8% and a sisal fiber content of 0.5%; ZY8%-0.5% indicates an alkali content of 8% and a bamboo fiber content of 0.5%. Precursor materials include S95 blast furnace slag, S105 blast furnace slag, and red mud, with 3 specimens per group.

[0033] Performance testing 1. Uniaxial tensile test The mechanical properties were tested using a WDW-10D microcomputer-controlled electronic universal testing machine. The maximum loading capacity of the machine is 20 kN. The test adopted a displacement-controlled loading method with a loading rate set at 0.2 mm / min. The test was terminated when the specimen's load-bearing capacity dropped to 60% of the peak load.

[0034] The test results show that for geopolymer mortar without any fiber incorporation, the specimen surface showed little change in the initial stage of the uniaxial tensile test. As loading continued, stress concentration gradually occurred inside the specimen, accompanied by slight cracking sounds. Subsequently, a crack penetrating the specimen surface formed at a certain moment, and the specimen immediately fractured. The load dropped rapidly after reaching its peak and lost its load-bearing capacity. The entire failure process was extremely rapid, with almost no obvious transition stage, exhibiting typical brittle failure characteristics. In contrast, geopolymer mortar incorporating plant fibers exhibited a significantly different failure mode during tensile loading. In the initial stage of the test, the specimen appearance also showed no significant change. As the tensile load gradually increased, fine cracks began to appear on the specimen surface. When the load reached its peak, the curve showed a brief decline, but the specimen could still bear the load. The cracks gradually increased and became clearer, while new cracks continuously formed. Subsequently, the load-bearing capacity decreased slowly after a brief fluctuation until final failure. Only then did a through crack form on the specimen surface, and the overall failure process exhibited obvious ductile characteristics. Figure 4 This represents the typical failure mode of FRGC under tensile stress.

[0035] Systematic tensile property tests were conducted on FRGC specimens with different mix proportions. Three parallel specimens were selected for each mix proportion, and the results were averaged (as shown in Tables 9 and 10 below). The test data show that the initial crack strength of the specimens ranged from 0.87 to 3.48 MPa, the ultimate tensile strength ranged from 0.93 to 3.62 MPa, and the maximum ultimate tensile strain exceeded 5%, which is more than 500 times that of traditional concrete materials.

[0036] Table 9 Table 10 Figure 5The variation of ultimate tensile strain in specimens under different variable conditions is shown. Comparative analysis of the data reveals that specimens in the JM-9%-1%, JM-9%-1.5%, JM-10%-1%, and JM-10%-1.5% groups exhibit relatively high ultimate tensile strain values. Further comparison of the influence of different fiber types on ultimate tensile strain shows that the bamboo fiber reinforced system generally exhibits a slightly lower ultimate tensile strain than the sisal fiber reinforced system. This is mainly related to the differences in the mechanical properties of the two plant fibers. Bamboo fiber itself has high stiffness and a relatively large elastic modulus, resulting in relatively limited deformation capacity during tension. Therefore, its ability to restrain crack propagation during crack development is relatively weak. In contrast, sisal fiber has better flexibility and deformation coordination. After crack formation, it can continuously bear part of the tensile stress through bridging and maintain effective stress transfer within a larger deformation range, thereby delaying crack propagation and improving the overall ductility of the material.

[0037] 2. Compressive strength test This invention utilizes a fully automated pressure testing system from Hualong Testing Instruments Co., Ltd., and refers to the "Standard for Test Methods of Basic Performance of Building Mortar" (JGJ / T 70-2009) for compressive strength testing. A continuous loading rate of 0.5 MPa / s is applied, and this rate is maintained at a constant rate until specimen failure during the failure phase. Specimens are standard cubes aged 3 days, 7 days, and 28 days, with dimensions of 70.7 mm × 70.7 mm × 70.7 mm and a size conversion factor of 0.95. Three specimens are used in each group. Compressive strength tests are conducted on EGC cube samples with different formulations. Origin data analysis software is used to construct a predictive model to systematically study the influence of various variables on the material's compressive strength. The test data is the average of the three parallel groups of specimens as the final test value. Detailed results are listed in Table 11.

[0038] Table 11 Figure 6-8 The ultimate compressive strengths of FRGC at different alkali equivalents (3D, 7D, and 28D) are given by... Figure 6-8 It can be seen that as the alkali equivalent increases from 8% to 10%, the ultimate compressive strength of the geopolymer specimens generally shows an upward trend, indicating that increasing the alkali equivalent within a certain range is beneficial to enhancing the mechanical properties of the material. Figure 9-11The ultimate compressive strength of specimens with different fiber types and fiber contents at 3D, 7D, and 28D were measured. The results show that increasing fiber content significantly affects the ultimate compressive strength of the specimens. Within the low to medium fiber content range, the change in compressive strength is relatively limited; however, when the fiber content reaches 1.5% wt, the strength decreases significantly, almost halving, indicating that the increased porosity, fiber agglomeration, and interfacial weakening effects caused by high fiber content dominate. Furthermore, under the same mix proportions, the compressive strength decrease of the bamboo fiber system is greater than that of the sisal fiber system, indicating that different fiber types have significantly different effects on the continuity of the matrix structure and the stability of the interface.

[0039] 3. Impact resistance The Split Hopkinson Pressure Bar (SHPB) test is a widely used technique for testing the dynamic mechanical properties of materials, particularly suitable for studying the mechanical behavior of materials under high strain rates. The SHPB device used in this invention has an impact bar diameter of 50 mm. A schematic diagram and a physical image of the device are shown below. Figure 12 A schematic diagram of a split Hopkinson pressure bar is shown. As can be seen from the diagram, the SHPB impact testing apparatus mainly consists of three parts: the impact bar, the incident bar, the transmission bar, and the absorbing bar. All three bars are made of high-strength alloy steel of ASTM 2600 grade, with a bar density of 7710 kg / m³ and a Young's modulus of 210 GPa. This invention selected six groups of materials with different mix proportions for impact testing: JM-9%-1%, JM-10%-1%, ZY-9%-1%, CG-9% (geolithic polymer without fiber and with an alkali equivalent of 9%), C25 (plain concrete, i.e., concrete mortar without aggregate), and RC25 (plain concrete with added wire mesh). Three specimens were set up for each group, resulting in a total of 18 specimens tested. The test steps are as follows: (1) Take out the specimens that have been cured for 28 days in the standard curing room, wipe the surface of the specimens with a clean, dry cloth to dry them. Then place the specimens in the indoor environment to air dry naturally for about 24 hours, and use sandpaper or a grinder to polish the upper and lower surfaces of the specimens. (2) Before the test begins, the air in the gas tank should be completely purged. After the purging operation is completed, push the bullet into the bottom of the chamber and attach a circular rubber pad at the center of the end of the incident rod where the bullet is about to hit. (3) Apply a layer of Vaseline evenly to the end faces of the incident rod and the transmission rod, as well as the contact surface of the specimen, to reduce contact friction and improve the interface contact effect. Then place the specimen between the incident rod and the transmission rod and adjust its position so that the specimen and the pressure rods at both ends are on the same axis and fit tightly. At the same time, attach strain gauges to the surface of the incident rod and the transmission rod to collect the stress wave propagation signal in the rod in real time. (4) Set the required nitrogen pressure parameters in the control panel and perform initial balancing and zeroing of the system using signal acquisition and analysis software. (5) Start the launching device on the control panel to complete the launching process of the impact rod. Record the impact velocity after the launch, save the stress wave waveform data obtained by the acquisition system, and collect the concrete fragments generated during the test. (6) Calculate and analyze the stress and strain response of the specimen under dynamic loading conditions based on the strain signals obtained during the test.

[0040] Figure 13 Stress / strain rate-strain curves for (a) JM-10%-1%, (b) JM-9%-1%, (c) ZY-9%-1% and (d) CG-9%; Figure 14 Stress / strain rate-strain plots for (a) C25, (b) RC25, (c) JM, and (d) ZY / CG. From... Figure 13 and Figure 14 From the overall curve morphology, the stress-strain relationship curves of plant fiber-infused specimens, unfiber-infused specimens, and concrete specimens under impact loading show a generally consistent trend, all exhibiting a clear stress rise phase and a rapid decline phase after the peak stress. However, there are some differences in detail. The fiber-infused group has a significantly smoother curve and a larger peak stress than the unfiber-infused group. This indicates that the incorporation of fibers can effectively improve the impact resistance of the specimens. In contrast, the peak stress of the concrete specimens is significantly lower than that of the other two types of specimens, and its stress-strain curve is generally smoother. However, it loses its load-bearing capacity at a relatively small strain level, indicating that its resistance to damage under impact is weak. This result shows that the deformation capacity and load-bearing capacity of ordinary concrete under dynamic loading are inferior to those of fiber-infused polymer materials.

[0041] 4. Drop weight test This invention refers to the impact test method recommended in CECS13-2009 "Standard for Test Methods of Fiber Reinforced Concrete" and uses a self-made drop hammer test device to carry out the concrete impact toughness test. During the test, the impact energy corresponding to the failure of the specimen is used as the evaluation index to characterize the impact resistance of the geopolymer material. Test steps and specimen selection: (1) For specimens that have completed 28 days of standard curing, demolding and surface cleaning are carried out before the test. Then, in order to unify the surface state of the specimen as much as possible, the surface wetness is appropriately controlled, and the specimen is placed in a constant temperature and humidity environment for 24 hours. (2) After the surface of the specimen is dried, it is placed in the center of the impact device chassis, and the impact ball is fixed in the designated position of the steel frame by the pin, so that the impact point of the drop hammer is as close as possible to the center of the specimen. Then the height of the movable crossbeam is adjusted and fixed at 0.6m. During the test, the drop hammer with a total mass of 2.2kg is released freely from a height of 0.6m, so that it impacts the center surface of the specimen vertically. Each free fall and contact with the specimen is recorded as one impact cycle. (3) During the impact loading process, when a through crack or a relatively obvious cracking failure occurs on the surface of the specimen, the number of impacts N corresponding to this state is recorded.

[0042] In this invention, the JM-9%-1% group, which exhibited the best overall performance in the aforementioned drop hammer impact test, was selected and compared with ordinary concrete specimens and reinforced concrete specimens. Considering the small size of the specimens and the difficulty in rationally arranging conventional reinforcing bars, wire mesh was used to equivalently replace the reinforcing bars in the concrete to simulate the restraining effect of the reinforcing bars. Figure 15 The diagram shows the specimens, from left to right: JM-9%-1% specimen, plain concrete specimen, and reinforced concrete specimen. The drop hammer test results for the three groups of specimens are summarized in Table 12. Because ordinary concrete, i.e., plain concrete, is used for drainage duct covers in tunnel engineering, this invention compares the prepared geopolymer material with materials used in actual applications.

[0043] Table 12 Note: Plain concrete in the table refers to concrete mortar without aggregate, while reinforced concrete refers to concrete mortar with wire mesh added to it.

[0044] As shown in Table 12, plain concrete exhibits the weakest impact resistance compared to the other two types of materials; reinforced concrete is second, while geopolymer materials incorporating sisal fibers demonstrate the best impact resistance. In terms of impact energy dissipation, the addition of sisal fibers increases the impact energy dissipation of geopolymer materials by nearly 300% compared to plain concrete (based on average failure count), and by approximately 200% compared to reinforced concrete (based on average failure count). This indicates that the introduction of sisal fibers effectively enhances the energy dissipation capacity and resistance to failure of geopolymer materials under impact loads. Although reinforced concrete is superior to plain concrete in impact resistance due to the ductility of the reinforcing steel and the synergistic stress effect, sisal fiber geopolymers also exhibit relatively outstanding impact resistance through fiber bridging, crack inhibition, and energy dissipation mechanisms, thus possessing excellent impact resistance.

[0045] Figure 16 The failure modes of the specimens in the drop hammer test are shown in (a) JM-9%-1%, (b) plain concrete, and (c) reinforced concrete. Comparative analysis shows that both the plain concrete specimen and the reinforced concrete specimen produced relatively obvious cracks after the impact load, indicating that both types of materials suffered cracking damage to different degrees, which reflects typical impact failure characteristics.

[0046] Impact comparison test between reinforced concrete and sisal fiber geopolymer cover plates: To better reflect the stress state of underground drainage ditch covers or manhole covers under loading, unloading, dropping, and accidental impact conditions in actual engineering projects, this invention uses simulation technology to compare and analyze the dynamic mechanical behavior of plain concrete covers, reinforced concrete covers, and sisal fiber geopolymer covers under different impact energy conditions. The relevant results are shown in Table 13, which shows the simulation results of sisal fiber geopolymer covers and reinforced concrete covers.

[0047] Figure 17 In the table, (a) represents the maximum displacement of the top surface of the plain concrete, (b) represents the maximum displacement of the bottom surface of the plain concrete, (c) represents the maximum displacement of the top surface of the reinforced concrete, and (d) represents the maximum displacement of the bottom surface of the reinforced concrete. Figure 18 (a) Maximum displacement of the top surface of the geopolymer (JM-9%-1%), (b) Maximum displacement of the bottom surface of the geopolymer, (c) Comparison of maximum displacement values ​​of concrete, reinforced concrete, and geopolymer, (d) Comparison of peak impact forces of concrete, reinforced concrete, and geopolymer. Figure 17-18 It is evident that, under the same impact conditions, the maximum displacement response of the sisal fiber geopolymer cover plate is significantly smaller than that of the reinforced concrete cover plate, which is smaller than that of the plain concrete cover plate, indicating that it has superior performance in resisting impact deformation.

[0048] Table 13 Note: C-2 to C-4 are plain concrete slabs, RC-2 to RC-4 are reinforced concrete slabs, and RSG-2-1.0 to RSG-4-1.0 are sisal fiber geopolymer (JM-9%-1%) slabs.

[0049] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A fiber-reinforced geopolymer composite material, characterized by, The raw materials include: precursor materials, quartz sand, plant fibers and composite alkali activator; the precursor materials include red mud and blast furnace slag; the plant fibers are selected from sisal fiber or bamboo fiber.

2. The fiber reinforced geopolymer composite according to claim 1, characterized in that, The fiber-reinforced geopolymer composite material has a sand-to-binder ratio of 0.36 and an alkali-to-binder ratio of 0.

55.

3. The fiber reinforced geopolymer composite according to claim 1, wherein, The composite alkali activator comprises sodium silicate solution, sodium hydroxide, and water, and the modulus of the composite alkali activator is 1.

4.

4. The fiber reinforced geopolymer composite according to claim 1, wherein, The sisal fiber has an average length of 18 mm, an average diameter of 0.40 µm, an ultimate elongation of 3.6%, a breaking strength of 11.3 cN / dtex, and a breaking force of 568 cN. The bamboo fiber has an average length of 20 mm, an average diameter of 0.22 µm, an ultimate elongation of 3.4%, a breaking strength of 6.7 cN / dtex, and a breaking tensile strength of 372 cN.

5. The fiber reinforced geopolymer composite according to claim 1, wherein, The red mud and blast furnace slag account for 20% and 80% of the mass of the precursor material, respectively.

6. The fiber reinforced geopolymer composite according to claim 1, wherein, The plant fiber accounts for 0.5-1.0% of the fiber-reinforced geopolymer composite material, and the alkali equivalent of the fiber-reinforced geopolymer composite material is 8-10%.

7. The fiber reinforced geopolymer composite according to claim 6, characterized in that, When the plant fiber is sisal fiber, it accounts for 1.0% of the fiber-reinforced geopolymer composite material, and the alkali equivalent of the fiber-reinforced geopolymer composite material is 9%.

8. A process for the production of a fibre reinforced geopolymer composite material as claimed in any one of claims 1 to 7, characterised in that, The process includes the following steps: weigh out red mud, blast furnace slag, quartz sand, and plant fiber respectively; mix the red mud and blast furnace slag evenly for the first time; add a compound alkali activator; mix evenly a second time; add quartz sand; mix evenly a third time; add plant fiber; mix evenly a fourth time; pour the slurry into a mold; compact it; level it; cover it with plastic wrap; let it stand at room temperature; demold it; and cure it after demolding.

9. The application of the fiber-reinforced geopolymer composite material according to any one of claims 1-8 in the construction of drainage well covers.

Images