Alkali residue-gangue-coal gasification residue concrete for hardening coal mine tunnel bottom plate and paving method thereof

Abstract

The invention belongs to the technical field of underground coal mine engineering, and particularly discloses alkali residue-gangue-coal gasification residue concrete for hardening a coal mine roadway bottom plate and a paving method thereof, and the concrete is prepared from the following raw materials in parts by weight: 2.5-4.5 parts of fine aggregate, 4-7 parts of coarse aggregate, 1-3 parts of cement, 0.5-1.5 parts of water and alkali residue; the use amount of the alkaline residues is 0-9% of the mass of the cement; the fine aggregate is composed of coal gasification coarse slag and yellow sand, and the mass ratio of the coal gasification coarse slag to the yellow sand is 1: (1-2); the coarse aggregate is composed of gangue and broken stone, and the using amount of the gangue is 0-30% of the mass of the coarse aggregate. The reasonable gangue replacement rate is determined by preparing gangue coal gasification slag concrete with different gangue replacement rates and testing the compressive strength of the gangue coal gasification slag concrete, the compressive strength and breaking strength of the alkali residue gangue coal gasification slag concrete are improved by further doping the alkali residues, and a concrete hardening paving process is provided. In order to construct a high-strength, flat and durable roadway foundation, the essential transformation from passive repair to active guarantee is realized.

Description

Technical Field

[0001] This invention belongs to the field of coal mine underground engineering technology, and relates to the hardening material for coal mine roadway floor slabs, specifically to an alkaline slag-gangue-coal gasification slag concrete for hardening coal mine roadway floor slabs and its paving method. Background Technology

[0002] Coal gangue is a solid waste generated during coal mining and washing, with an annual discharge exceeding 700 million tons. Its accumulation not only occupies vast amounts of land but also poses a series of environmental problems, such as spontaneous combustion, soil pollution, and water resource contamination. my country's annual tunnel excavation volume reaches 150,000 kilometers, and the hardening of the foundation concrete requires a huge amount of sand and gravel aggregate. Years of mining have led to a sharp depletion of crushed stone resources. Coal gangue's mineral composition and properties are similar to natural crushed stone. Utilizing gangue to replace crushed stone coarse aggregate in the preparation of gangue concrete has become a research hotspot in the building materials field in recent years. Concrete prepared based on coal gangue aggregate can alleviate the problem of coal gangue accumulation and reduce the amount of crushed stone used, resulting in significant economic and environmental benefits.

[0003] my country is the world's largest producer of soda ash, with over 50% produced using the ammonia-soda process. Each ton of soda ash produced generates approximately 0.6 tons of soda ash residue, resulting in over 8 million tons of residue annually and hundreds of millions of tons stockpiled. Currently, the main methods for treating soda ash residue include discharging the clear liquid into the sea and surface accumulation, causing severe water pollution and soil salinization. Soluble salts account for over 20% of the soda ash residue, primarily CaCl2 and NaCl chlorides. - The content of alkali residue is extremely high, and the current comprehensive utilization rate of solid waste alkali residue is less than 4%, which is far below the national requirement for the utilization rate of bulk solid waste. With increasingly stringent regulatory policies for solid waste management, many alkali production enterprises have been forced to suspend production or close down because they are unable to dispose of alkali residue. The reduction and resource utilization of solid waste alkali residue is now urgent.

[0004] The construction of the tunnel floor slab is a systematic project, and its quality directly affects the tunnel's service life, transportation efficiency, and operational safety. Research revealed that unlike common surface concrete pavement defects such as breakage, subsidence, and corner fractures, tunnel floor slabs experience floor bulging under high-level stress, inducing simultaneous floor bulging damage to the hardened gangue concrete pavement. In some cases, the bulging depth exceeds 1.5 meters, requiring frequent repairs and making floor removal extremely difficult, severely impacting underground vehicle safety and production efficiency. The stress characteristics and environment determine that the core strength indicator of the pavement is flexural strength. While the compressive strength of the floor slab pavement meets or even exceeds requirements, the primary cause of pavement damage is insufficient flexural strength. The high-level stress of floor bulging places higher demands on the flexural strength of the gangue concrete pavement; therefore, improving the flexural strength of the gangue concrete is crucial to ensuring the long-term stability of the floor slab pavement. The physical and mechanical properties of coal gangue are inferior to those of crushed stone. Using gangue to prepare concrete may lead to varying degrees of reduction in the concrete's mechanical properties; the addition of alkaline slag can compensate for this strength degradation. Therefore, in order to reduce the cost of hardening the roadway floor and simultaneously dispose of solid waste gangue, coal gasification coarse slag and alkali slag, this study on alkali slag-gangue-coal gasification slag concrete for hardening coal mine roadway floors and its paving method can provide a reference for the subsequent mix design and on-site construction of solid waste concrete for mining. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an alkali slag-gangue-coal gasification slag concrete for hardening coal mine roadway floors. This invention effectively utilizes coal gangue and alkali slag, reduces the amount of crushed stone aggregate used while improving the flexural and compressive strength of the concrete, reduces the cost of hardening mine roadway floors, and standardizes the paving process. It provides solid strategic support for the safe, efficient, and sustainable development of coal mines. It solves the problems of coal gangue and alkali slag management, as well as the challenge of insufficient flexural strength in roadway floor paving concrete.

[0006] This invention is achieved through the following technical solution: An alkaline slag-gangue-coal gasification slag concrete for hardening the floor slab of coal mine roadways is composed of the following raw materials in parts by weight: 2.5-4.5 parts fine aggregate, 4-7 parts coarse aggregate, 1-3 parts cement, 0.5-1.5 parts water, and alkaline slag; the amount of alkaline slag is 0-9% of the cement mass; the fine aggregate is composed of coal gasification slag and yellow sand, wherein the mass ratio of coal gasification slag to yellow sand is 1:1-2; the coarse aggregate is composed of gangue and crushed stone, wherein the amount of gangue is 0-30% of the coarse aggregate mass.

[0007] A further improvement to the present invention is as follows: The concrete is composed of the following raw materials in parts by weight: 3.065 parts fine aggregate, 5.69 parts coarse aggregate, 2 parts cement, 1 part water, and alkali residue; the amount of alkali residue is 3-9% of the cement mass; the fine aggregate is composed of gasification coarse slag and yellow sand, wherein the mass ratio of gasification coarse slag to yellow sand is 1:1.5; the coarse aggregate is composed of gangue and crushed stone, wherein the amount of gangue is 10-30% of the coarse aggregate mass.

[0008] Furthermore, the amount of alkaline slag used is 6% of the cement mass; the amount of gangue used is 30% of the coarse aggregate mass.

[0009] Furthermore, the particle size of the alkaline slag is 2-3 mm; the particle size of the coal gasification slag is 4-5 mm; and the gradation of the gangue is 9.5-13.2 mm, 13.2-16 mm, and 16-19 mm.

[0010] A further improvement of the present invention is as follows: A method for paving alkaline slag-gangue-coal gasification slag concrete for hardening the floor slab of coal mine roadways includes the following steps: (1) Mixing and transportation Mixing: A mobile coal mine concrete mixer is used for underground mixing. The mixer is located approximately 5-10 meters away from the hardening slab location. For each slab hardening project, the optimal mixing time should be determined through trial mixing based on the cohesiveness, homogeneity, and strength stability of the mixture. Before mixing, a small amount of cement mortar (with the same water-cement ratio as the final mix proportion) should be used to rinse the mixer drum. This rinsed mortar should then be scraped off to prevent cement mortar from adhering to the mixer drum wall during the final concrete mixing. Weigh all raw materials according to regulations and add them to the mixer in the following order: cement, crushed stone, gangue, yellow sand, alkali residue, and coal gasification slag. The amount of material mixed at one time should not exceed 90% of the mixer's rated capacity. Start the mixer and mix the raw materials evenly. During the mixing process, add water at a uniform rate, and the total addition time should not exceed 2 minutes. After all the water has been added, continue mixing for approximately the same time as the optimal mixing time determined by the trial.

[0011] Transportation: Use self-unloading trucks equipped with underground dump trucks to transport concrete from the mixer to the roadway hardening paving site. The number and type of trucks should be determined based on the specific paving length, width, and thickness of the hardened road surface sections. The total transport capacity of the trucks should be slightly more than the total mixing capacity to ensure that the fresh concrete arrives at the roadway hardening paving site within the specified time for paving. During transportation, prevent grout leakage and material spillage. Minimize bumps during transport to prevent segregation of the mixture. Vehicles should start and stop smoothly. Collisions between transport vehicles and templates or baselines are strictly prohibited. If a collision occurs, corrective measures should be taken.

[0012] (2) Cleaning and leveling the base plate; Before paving, clean up the debris in the roadway and remove loose coal and gravel from the unpaved base plate. During the roadway excavation process, unevenness is likely to occur in the roadway. Before hardening the base plate, the severely uneven areas of the base plate need to be leveled. Severely protruding areas can be leveled, and larger depressions can be filled and compacted with filler to prevent local voids during later use, which could cause local stress concentration and slab fracture damage to the concrete surface layer.

[0013] (3) Steel formwork (guide rail) installation; steel formwork is installed on both sides of the hardened pavement width of the base plate, with the distance between the two steel formworks being the width of the hardened pavement ( B-2a The height of the steel formwork is the same as the thickness of the hardened road surface. The outside of the steel formwork is fixed to the tunnel floor slab with tie rods and steel rods, with the steel rods driven into the tunnel floor slab to a depth of about 15-20cm; the inside of the steel formwork is directly inserted into the floor slab with steel rods, with the steel rods driven into the tunnel floor slab to a depth of about 10-15cm.

[0014] (4) Mixing and unloading concrete; When the lateral steel formwork of the work unit is installed, spray water to fully wet the tunnel floor and the inside of the steel formwork, ensuring that there is no water accumulation, so as to ensure good bonding between the steel formwork, the floor and the paving concrete. Use a transport vehicle to unload the ash and gangue-based solid waste cement concrete mixed evenly by the mixer from the inside to the outside in the work unit in the backward direction. A dedicated person should direct the even unloading. The unloading speed should be controlled at 30~40m / h and should be adapted to the paving speed.

[0015] (5) Manual concrete placement: After the transport vehicle unloads the concrete, remove the steel rods inside the steel formwork and fill the gaps in the base plate with concrete. Use a shovel to roughly level the surface. When manually adding material, it is advisable to use a shovel to spread it. Throwing and stepping on the concrete is strictly prohibited to prevent segregation of the concrete mixture. Since the paving capacity of the three-roller screed is relatively weak, special attention should be paid to the uniformity of the concrete placement and the placement height should be accurately controlled. The loose laying coefficient of the concrete should be controlled at 1.05~1.10, and the placement height should be slightly higher than the top surface of the steel formwork by 10~20mm.

[0016] (6) Intensive Vibration and Initial Leveling: After the concrete is manually laid within the length of the roadway floor hardening unit, adjust the insertion depth of the vibrator and begin vibration. When the vibrator is continuously dragged for vibration, the operating speed should be controlled at 4 m / min. The vibrator should move forward slowly and continuously at a uniform speed. The operating speed should be such that the coarse aggregate of gangue is not exposed on the surface of the mixture, and the liquefied surface no longer emits gas and cement slurry appears.

[0017] (7) Paver leveling: Paver leveling should be carried out within 15 minutes after the paver has completed the vibration work of the work unit. The compacted material level of the paver's three rollers should be 5-20mm higher than the top surface of the steel formwork. If it is too high, it should be removed; if it is too low, it should be replenished in time. Within the length of one work unit, it is advisable to use forward vibration and backward static rolling, preferably 2-3 times each. The optimal number of rolling passes should be determined by testing. During paving and leveling operations, a dedicated person should handle the material level in front of the rollers. After rolling, lift the vibrating rollers away from the steel formwork and use the leveling shaft to statically roll back and forth to level. Continue until the flatness meets the requirements and the surface mortar thickness is uniform.

[0018] (8) Manual finishing and roughening; the thickness of the surface mortar should be controlled at (4±1) mm. Excessively thick or thin mortar on the surface in front of the paver roller leveler must be cut off and discarded. A 3-5m scraper should be used to perform static leveling in both longitudinal and transverse directions, with no less than two passes in each direction. Alternatively, a rotary trowel can be used to compact and level the surface twice. The latest time for finishing with a scraper, scraper, or trowel should not be later than the maximum allowable time for paving completion, generally not exceeding 1.5-2.0 hours. After finishing, when the concrete surface sinks to about 5mm under slight finger pressure, a plastic brush should be used to roughen the transverse surface of the bridge. The roughening should be uniform in line and the depth should be controlled at 2-3mm. Roughening must be completed before initial setting and should be done on a pedestrian work platform.

[0019] (9) Transverse construction joint sawing: In order to prevent the concrete slab from being too large and causing excessive temperature stress or volume stress, sawing operations can begin when the surface of the concrete slab has hardened sufficiently to withstand the sawing equipment. Transverse sawing operations are carried out every 5 to 10 meters depending on the width of the concrete pavement in the work unit. After the sawing operation is completed, all sawdust and debris should be cleaned up immediately and the joint should be filled with a specific jointing material.

[0020] (10) Concrete curing: After the concrete has set or when there are no traces of people standing on the concrete surface, cover it with a non-polluting geotextile with good water retention properties. The geotextile should be kept moist during the curing period. When the temperature underground is high, shrinkage cracks are likely to appear after the concrete has initially set. Before it is possible to cover the concrete with geotextile for saturated curing, early curing measures such as spraying should be taken. The specific curing specimens should be determined based on the concrete final set specimens. After curing, a special person should be assigned to use a broom to remove the residue from the roughening process to ensure that the paving layer is flat and clean.

[0021] (11) Fill the side ditches on both sides of the hardened road surface; after the hardened road surface of the tunnel has been fully hardened, remove the steel formwork on both sides of the road surface, and fill the hardened road surface concrete slabs and the remaining width on both sides of the tunnel completely by manual filling. If it is necessary to leave the tunnel drainage ditch, pay attention to the formwork laying according to the design width and depth.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention uses gangue to replace crushed stone and coal gasification slag to replace yellow sand, which reduces the amount of crushed stone and yellow sand used, and provides a theoretical reference for reducing material costs and resource utilization of solid waste.

[0023] (2) This invention uses coal gangue and alkali slag, two industrial solid wastes, to harden the mine floor road surface, which to a certain extent solves the problems of gangue and alkali slag treatment and environmental pollution, and also alleviates the demand for crushed stone for floor hardening.

[0024] (3) This invention clarifies the reasonable dosage of gangue to replace crushed stone, which can provide key reference and design basis for the use of gangue to replace crushed stone in similar projects.

[0025] (4) The alkali slag-gangue-coal gasification slag concrete provided by the present invention not only ensures the compressive strength, but also meets the requirements of the flexural strength of the coal mine roadway floor, making full use of solid waste and solving the problem of floor bulging damage. Attached Figure Description

[0026] Figure 1 Preparation diagram of the compression test specimen in Example 1; Figure 2 Schematic diagram of compressive strength at 28 days with different gangue replacement rates in Example 1; Figure 3 This is a diagram showing the preparation of the compressive strength specimen in Example 2. Figure 4 This is a schematic diagram of the 28-day compressive strength under different alkali residue dosages in Example 2; Figure 5 The images show the preparation of 28-day flexural strength specimens under different alkali slag dosages in Example 2. Figure 6 This is a schematic diagram of the 28-day flexural strength under different alkali residue dosages in Example 2; Figure 7 This is a flowchart illustrating the paving process of alkali slag-gangue-coal gasification slag concrete for hardening the floor slab of coal mine roadways according to the present invention. Detailed Implementation

[0027] The present invention will now be described in detail with reference to specific embodiments.

[0028] The alkali residue used in this invention was sourced from Jiangsu Huai'an Suyanjingshen Co., Ltd., and was used as an auxiliary cementing material. The alkali residue transported to the laboratory was air-dried, crushed, and passed through a 2.36mm standard sieve, with a moisture content of less than 31.45%. The coal gasification slag used was coarse slag with a rough surface and porous interior. The coarse coal gasification slag contained a large number of large-diameter impurities and was passed through a 4.75mm standard sieve before use. The cement was PO 42.5 grade ordinary Portland cement. The gangue gradation was divided into three types: 9.5~13.2mm, 13.2~16mm, and 16~19mm. The crushed stone was commercially purchased limestone crushed stone, and the water absorption rate and maximum dry density of the crushed stone were measured. The yellow sand was natural river sand, with quartz as its main component. The water was laboratory deionized water.

[0029] Example 1: Determining the maximum gangue replacement rate to ensure compressive strength In this embodiment, the concrete does not contain alkali slag. A control group (G0) is used, where gangue does not replace crushed stone. A control mix proportion is set, with a 40% replacement rate of yellow sand using coal gasification slag. Tests are conducted in groups 0 to 1, with the gangue replacement rate increasing progressively in each group. The compressive strength of the gangue-coal gasification slag concrete under different gangue replacement rates is tested. The goal is to achieve the highest possible gangue replacement rate while maintaining a compressive strength no less than 90% of the control group.

[0030] Specifically, the replacement rates of crushed stone with gangue were 0%, 10%, 20%, 30%, and 40% respectively, and the concrete mix proportions were water:cement:fine aggregate:coarse aggregate = 1:2:3.065:5.69. The gangue replacement ratio for coarse aggregate is shown in Table 1. Five groups of tests were designed, G0-G4. The water-cement ratio was water / cement = 1 / 2.

[0031] Table 1. Proportion of Gangue Replacing Coarse Aggregate

[0032] The specific mass ratio of the test materials is shown in Table 2.

[0033] Table 2 Calculation Table of Mass of Compression Specimen

[0034] According to the set mix ratio, all dry materials were mixed evenly, and then deionized water was added. The compressive strength test specimens were prepared and cured according to the "Test Procedures for Cement and Cement Concrete in Highway Engineering" (JTG3420-2020) for unconfined compressive strength testing. The specimens were molded using a triple mold (100mm×100mm×100mm). After 24 hours, the specimens were formed and cured at (20±2)℃ and 95% humidity for 28 days. The specimens were then... Figure 1As shown in the figure, the WAW-1000 electro-hydraulic servo universal material testing machine was selected for compressive strength testing. The loading rate was 2kN / s. Three samples were prepared for each group, and the average value was taken as the final result. The concrete strength under different gangue replacement rates is shown in Table 3.

[0035] Table 3 Unconfined compressive strength of concrete under different gangue replacement rates

[0036] After incorporating gangue, the unconfined compressive strength of the specimens was not less than 90% of the compressive strength of the reference group concrete, i.e., the 28-day strength was higher than 33.66 MPa. Figure 2 It can be seen that the optimal replacement rate of gangue is 30%.

[0037] Example 2: Further determine the amount of alkali slag to simultaneously ensure compressive strength and flexural strength. The reference group (K0) was gangue-gasification slag concrete without alkali residue. The gangue replacement rate was 30%. The experimental groups were gangue-gasification slag concrete with different alkali residue contents. The experiment was set up into groups 0 to j, with alkali residue contents of 0%, 1 / 4y%, 1 / 2y%, 3 / 4y%, and y% respectively. The compressive strength and flexural strength of the specimens in each group were tested.

[0038] Specifically, when testing compressive strength, the alkali-slag content was 0%, 3%, 6%, 9%, and 12% respectively, and the concrete mix ratio was water:cement:fine aggregate:coarse aggregate = 1:2:3.065:5.69. The gangue replacement rate was 30%. Five groups of compressive strength tests were designed, K0-K4. The water-cement ratio was water / cement = 1 / 2. Tables 4 and 5 are the alkali-slag content ratio table and the compressive strength specimen mass calculation table, respectively. Table 6 shows the compressive strength of gangue-gasification slag concrete under different alkali-slag contents. The overall specimen is shown below. Figure 3 As shown.

[0039] Table 4. Alkali Slag Addition Ratio Table

[0040] Table 5 Calculation Table of Mass of Compression Specimen

[0041] Table 6 Unconfined compressive strength of gangue-gasification slag concrete with different alkali residue admixtures

[0042] From Table 6 and Figure 4 It can be seen that with the increase of alkali residue content, the 28-day compressive strength shows a trend of first increasing and then decreasing. The strength reaches the highest of 36.63 MPa at a content of 3%, which is 5.35% higher than that of the K0 group.

[0043] The same gradient alkali slag content and gangue replacement rate were used to test the flexural strength. Table 7 shows the specific mass ratio of the flexural specimen materials.

[0044] Table 7. Composition of Flexural Specimens

[0045] According to the set mix proportions, all dry materials were mixed evenly, and then deionized water was added. Prismatic specimens of 100mm × 100mm × 400mm were prepared according to the "Test Procedures for Cement and Cement Concrete in Highway Engineering" (JTG 3420-2020). Three specimens were formed for each mix proportion. After 24 hours, the specimens were formed and cured at (20±2)℃ and 95% humidity for 28 days. The specimens were prepared as follows. Figure 5 As shown in the table. A WAW-1000 electro-hydraulic servo universal testing machine was used for flexural strength testing. Three samples were prepared for each group, and the average value was taken as the final result. Table 8 shows the flexural strength results of gangue-gasification slag concrete under different alkali slag contents. The variation in flexural strength is shown in the table. Figure 6 As shown.

[0046] Table 8 Flexural strength under different alkali slag admixtures

[0047] Based on the above test results, the mix proportions can be selected. The gangue replacement rate can be 0%-30%, and the alkali residue content can be 0%-9%. While meeting the strength requirements, solid waste should be treated as much as possible. The optimal gangue replacement rate is 30%, and the alkali residue replacement rate is 6%.

[0048] Example 3: Hardening and Paving of Roadway Floor The mix design uses a water:cement:fine aggregate:coarse aggregate ratio of 1:2:3.065:5.69. The fine aggregate consists of gasification slag and yellow sand, with a mass ratio of 1:1.5. The coarse aggregate consists of gangue and crushed stone, with a gangue replacement rate of 30%. The alkali residue content is 9% of the cement mass. The treated materials are mixed, transported, and laid. The laying process is as follows: Figure 7 As shown.

[0049] I. Mixing and Transportation Mixing: A mobile coal mine concrete mixer is used for underground mixing. The mixer is located approximately 5-10 meters away from the hardening slab location. For each slab hardening project, the optimal mixing time should be determined through trial mixing based on the cohesiveness, homogeneity, and strength stability of the mixture. Before mixing, a small amount of cement mortar (with the same water-cement ratio as the final mix proportion) should be used to rinse the mixer drum. This rinsed mortar should then be scraped off to prevent cement mortar from adhering to the mixer drum wall during the final concrete mixing. Weigh all raw materials according to regulations and add them to the mixer in the following order: cement, crushed stone, gangue, yellow sand, alkali residue, and coal gasification slag. The amount of material mixed at one time should not exceed 90% of the mixer's rated capacity. Start the mixer and mix the raw materials evenly. During the mixing process, add water at a uniform rate, and the total addition time should not exceed 2 minutes. After all the water has been added, continue mixing for approximately the same time as the optimal mixing time determined by the trial.

[0050] Transportation: Use self-unloading trucks equipped with underground dump trucks to transport concrete from the mixer to the roadway hardening paving site. The number and type of trucks should be determined based on the specific paving length, width, and thickness of the hardened road surface sections. The total transport capacity of the trucks should be slightly more than the total mixing capacity to ensure that the fresh concrete arrives at the roadway hardening paving site within the specified time for paving. During transportation, prevent grout leakage and material spillage. Minimize bumps during transport to prevent segregation of the mixture. Vehicles should start and stop smoothly. Collisions between transport vehicles and templates or baselines are strictly prohibited. If a collision occurs, corrective measures should be taken.

[0051] II. Paving Process and Technical Requirements Step 1: Cleaning and leveling the base slab; Before paving, clean up debris in the roadway and remove loose coal and gravel from the unpaved base slab. Unevenness is common during roadway excavation. Before hardening the base slab, severely uneven areas need to be leveled. Severely protruding areas can be leveled, while larger depressions should be filled and compacted with filler to prevent localized voids during later use, which could lead to stress concentration and slab fracture in the concrete surface.

[0052] Step 2: Steel formwork (guide rail) installation; install steel formwork on both sides of the hardened pavement width, with the distance between the two steel formworks being the width of the hardened pavement (…). B-2a The height of the steel formwork is the same as the thickness of the hardened road surface. The outside of the steel formwork is fixed to the tunnel floor slab with tie rods and steel rods, with the steel rods driven into the tunnel floor slab to a depth of about 15-20cm; the inside of the steel formwork is directly inserted into the floor slab with steel rods, with the steel rods driven into the tunnel floor slab to a depth of about 10-15cm.

[0053] Step 3: Mixing and unloading concrete; When the lateral steel formwork of the work unit is installed, spray water to thoroughly wet the tunnel floor and the inside of the steel formwork, ensuring no water accumulation, to guarantee a good bond between the steel formwork, floor, and paving concrete. Use a transport vehicle to evenly unload the uniformly mixed ash and gangue-based solid waste cement concrete from the inside to the outside in the work unit in a backward direction. A designated person should direct the even unloading, and the unloading speed should be controlled at 30-40 m / h, adapted to the paving speed.

[0054] Step 4: Manual Concrete Placement; After the transport vehicle unloads the concrete, remove the steel spikes inside the steel formwork and fill the gaps in the base slab with concrete. Use a shovel to roughly level the surface. When manually adding material, use a shovel to spread it evenly; throwing or stepping on the concrete is strictly prohibited to prevent segregation of the concrete mixture. Because the three-roller screed has relatively weak paving capacity, special attention must be paid to the uniformity of the concrete placement and the placement height must be accurately controlled. The loose-laying coefficient should be controlled between 1.05 and 1.10, and the placement height should be slightly higher than the top surface of the steel formwork by 10-20mm.

[0055] Step 5: Intensive Vibration and Initial Leveling; After the concrete is manually placed within the hardened unit length of the tunnel floor, adjust the insertion depth of the vibrator and begin vibration. When the vibrator is continuously dragged along, the operating speed should be controlled at 4 m / min. The vibrator should move forward slowly and continuously at a uniform speed. The operating speed should be such that the coarse aggregate of gangue is not exposed on the surface of the mixture, and the liquefied surface no longer emits gas and cement slurry appears.

[0056] Step 6: Paver Leveling; Paver leveling should be performed within 15 minutes of the paver completing its vibration compaction work unit. The compacted material level after the paver's three rollers compaction should be 5-20mm higher than the top surface of the steel formwork. If it is too high, it should be removed; if it is too low, material should be added promptly. Within one work unit length, it is advisable to use a forward vibrating and backward static rolling method, preferably 2-3 passes. The optimal number of rolling passes should be determined through testing. During paving and leveling, a designated person should handle any unevenness in the material level in front of the rollers. After rolling, lift the vibrating rollers away from the steel formwork and use a leveling shaft to statically roll and level the surface until the flatness meets the requirements and the surface mortar thickness is uniform.

[0057] Step 7: Manual finishing and roughening; the surface mortar thickness should be controlled at (4±1)mm. Excessively thick or thin mortar on the surface in front of the paver roller leveler must be cut off and discarded. A 3-5m screed should be used to perform static leveling in both longitudinal and transverse directions, with at least two passes in each direction. Alternatively, a rotary trowel can be used to compact and level the surface twice. The finishing process using a screed, scraper, or trowel should not be later than the maximum allowable time for paving completion, generally not exceeding 1.5-2.0 hours. After finishing, when the concrete surface sinks to approximately 5mm under slight finger pressure, a plastic brush should be used to roughen the transverse surface of the bridge deck. The roughening should be uniform in line and controlled to a depth of 2-3mm. Roughening must be completed before initial setting and should be done on a scaffold.

[0058] Step 8: Sawing transverse construction joints; To prevent excessive temperature or volumetric stress caused by the large volume of the concrete slab, sawing can begin once the concrete slab surface has hardened sufficiently to withstand the sawing equipment. Transverse sawing should be performed every 5-10 meters across the width of the concrete pavement within the work unit. After sawing is completed, all sawdust and debris should be immediately removed, and the joints should be filled with a specific sealant.

[0059] Step 9: Concrete Curing; After the concrete has set or when there are no traces of people standing on the concrete surface, cover it with a non-polluting geotextile with good water retention properties. The geotextile should be kept moist throughout the curing period. When the underground temperature is high, shrinkage cracks are prone to appear after the initial setting of the concrete. Before it is possible to cover the concrete with geotextile and allow it to saturate with water for curing, early curing measures such as spraying should be taken. The specific curing test specimens should be determined based on the final set concrete test specimens. After curing, a designated person should use a broom to remove any residue from the roughening process to ensure the pavement layer is flat and clean.

[0060] Step 10: Fill the side ditches on both sides of the hardened road surface; after the hardened road surface of the tunnel has finally set, remove the steel formwork on both sides of the road surface, and fill the hardened road surface concrete slabs and the remaining width on both sides of the tunnel completely by manual filling. If it is necessary to leave the tunnel drainage ditch, pay attention to the formwork laying according to the design width and depth.

[0061] This invention first prepares gangue gasification slag concrete with different gangue replacement rates through preliminary experiments, and tests its compressive strength to determine the optimal gangue replacement rate. Then, by adding alkaline slag, the compressive strength and flexural strength of the alkaline slag gangue gasification slag concrete are improved. A set of roadway floor hardening paving process is designed to realize the essential transformation from passive repair to active protection for building a high-strength, flat and durable roadway "foundation".

[0062] The above description of the embodiments is only for illustrating the technical concept and features of the present invention. Its purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. Those skilled in the art can obviously easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative effort. Therefore, the above embodiments should not be used to limit the scope of protection of the present invention. All improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A type of alkaline slag-gangue-coal gasification slag concrete for hardening the floor slab of coal mine roadways, characterized in that, It is composed of the following raw materials in parts by weight: 2.5-4.5 parts fine aggregate, 4-7 parts coarse aggregate, 1-3 parts cement, 0.5-1.5 parts water, and alkali slag; the amount of alkali slag is 0-9% of the cement mass; the fine aggregate is composed of coal gasification slag and yellow sand, wherein the mass ratio of coal gasification slag to yellow sand is 1:1-2; the coarse aggregate is composed of gangue and crushed stone, wherein the amount of gangue is 0-30% of the coarse aggregate mass.

2. The alkaline slag-gangue-coal gasification slag concrete for hardening the floor slab of coal mine roadways according to claim 1, characterized in that: It is composed of the following raw materials in parts by weight: 3.065 parts fine aggregate, 5.69 parts coarse aggregate, 2 parts cement, 1 part water, and alkali slag; the amount of alkali slag is 3-9% of the cement mass; the fine aggregate is composed of coal gasification slag and yellow sand, wherein the mass ratio of coal gasification slag to yellow sand is 1:1.5; the coarse aggregate is composed of gangue and crushed stone, wherein the amount of gangue is 10-30% of the coarse aggregate mass.

3. The alkaline slag-gangue-coal gasification slag concrete for hardening the floor slab of coal mine roadways according to claim 1, characterized in that: The amount of alkaline residue used is 6% of the cement mass; the amount of gangue used is 30% of the coarse aggregate mass.

4. The alkaline slag-gangue-coal gasification slag concrete for hardening the floor slab of coal mine roadways according to claim 1, characterized in that: The particle size of the alkaline residue is 2-3 mm; the particle size of the coal gasification coarse slag is 4-5 mm; and the gradation of the gangue is 9.5-13.2 mm, 13.2-16 mm, and 16-19 mm.

5. The method for paving alkaline slag-gangue-coal gasification slag concrete for hardening the floor slab of coal mine roadways as described in claim 1, characterized in that, Includes the following steps: (1) Mixing and transportation: A mobile coal mine concrete mixer is used, and the mixer is 5-10m away from the hardening paving site; weigh all kinds of raw materials according to the proportion, and add cement, crushed stone, gangue, yellow sand, alkali slag and coal gasification slag into the mixer in sequence. Start the mixer and mix the raw materials evenly. Add water at a constant speed during the mixing process. After all the water has been added, continue mixing; select an underground explosion-proof mine material transport vehicle with self-unloading function to transport the material to the roadway hardening site in a timely manner. (2) Cleaning and leveling the bottom plate: Before paving, clean up the debris in the roadway, remove the loose coal and gravel on the unpaved bottom plate, and level the severely uneven areas of the bottom plate. (3) Steel formwork installation: Steel formwork is installed on both sides of the hardened pavement width of the base plate, with the distance between the two steel formworks being the width of the hardened pavement, and the height of the steel formwork being the same as the thickness of the hardened pavement; (4) Mixing and unloading concrete: When the side steel formwork of the work unit is installed, spray water to fully wet the bottom plate of the roadway and the inside of the steel formwork. With the standard of no water accumulation, use a transport vehicle to unload the ash and gangue-based solid waste cement concrete mixed evenly by the mixer from the inside to the outside in the work unit in the backward direction. (5) Manual concrete placement: After the transport vehicle has finished unloading, remove the steel rods inside the steel formwork and fill the gaps in the bottom plate with concrete. Use a shovel to roughly level the surface. (6) Dense Vibration Initial Leveling: After the concrete is manually placed within the length of the roadway floor hardening unit, the vibration operation is started after adjusting the insertion depth of the vibrator. The vibrator is continuously dragged to vibrate and compact. (7) Paver leveling: Paver leveling shall be carried out within 15 minutes after the paver has completed the vibration work of the work unit; (8) Artificial finishing and roughening: Use scraper, scraper or rotary finishing machine to make dense and smooth finish in both longitudinal and transverse directions; after finishing, when the concrete surface sinks to about 5mm under slight finger pressure, use plastic brush to roughen the transverse bridge surface. The roughening should be uniform and the depth should be controlled at 2~3mm. (9) Transverse construction joint sawing: When the concrete slab surface has hardened to a level sufficient to support the sawing equipment, the sawing operation begins. Transverse sawing is carried out every 5 to 10 meters depending on the width of the concrete pavement in the work unit. After the sawing operation is completed, the sawdust and debris are removed and the joint is filled with sealant. (10) Concrete curing: After the concrete has set or when there are no traces of people standing on the concrete surface, cover it with geotextile and cure it in a moist state. (11) Filling side ditches on both sides of the hardened road surface: After the hardened road surface of the tunnel is finally set, remove the steel formwork on both sides of the road surface, and fill the hardened road surface concrete slabs and the remaining width on both sides of the tunnel completely by manual filling. If it is necessary to leave a tunnel drainage ditch, lay it according to the design width and depth.

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