Filler for red-bed soft rock roadbed and preparation method thereof

Abstract

The application relates to the technical field of civil engineering materials, and discloses a filler for red-layer soft rock roadbed and a preparation method thereof. The method comprises raw material pretreatment, step-by-step composite mixing, stabilization treatment and vibration compaction forming. Through accurate progressive control of the step-by-step composite mixing process, mechanical interlocking fusion of coarse aggregate strengthening components and red-layer soft rock fragments is first realized, then an active curing agent is introduced to activate deep reaction, and finally molecular-level coating of a hydrophobic modification material is realized, so that the problem of weak interface bonding caused by uneven mixing of components in traditional processes is solved, a continuous three-dimensional network structure is formed in the filler, and the overall deformation coordination and structural compactness are improved; through dynamic balance of temperature field distribution, the risk of molecular chain rupture caused by heat accumulation in local areas is inhibited, so that the filler still maintains stable hydrophobic properties and volume integrity under an extreme dry-wet cycle environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of civil engineering materials, in particular to a filler for red-layer soft rock subgrade and a preparation method thereof. BACKGROUND

[0002] As the foundation structure of highway and railway engineering, the stability and deformation resistance of subgrade directly affect the driving safety and operation quality. To ensure the safe and smooth operation of vehicles, the subgrade structure must meet the following key performance requirements: high strength characteristics, excellent durability, good stability, and the ability to resist settlement deformation caused by various environmental factors. It is worth noting that red-layer soft rock, as a special geological material, has a wide distribution characteristic worldwide. With the continuous expansion of modern transportation networks to mountainous areas, the construction of subgrade engineering in red-layer areas has become an important technical problem to be solved in the field of geotechnical engineering.

[0003] Currently, in the industrialized preparation process of red-layer soft rock subgrade filler, due to the significant difference in activity of raw material components and the lack of process synergy, when the residual water content of rock debris fluctuates beyond the standard or the environmental temperature and humidity is out of control during the raw material mixing stage, it will directly lead to the violent fluctuation of the hydration reaction of active curing agents. Due to the density difference, the coarse aggregate strengthening components will produce serious segregation during the mixing process.

[0004] Therefore, the present application provides a filler for red-layer soft rock subgrade and a preparation method thereof to solve the above problems. SUMMARY

[0005] (I) Technical problems solved

[0006] In view of the deficiencies in the prior art, the present application provides a filler for red-layer soft rock subgrade and a preparation method thereof, which solves the problems raised in the background art.

[0007] (II) Technical solutions

[0008] To achieve the above purpose, the present application provides the following technical solutions: a filler for red-layer soft rock subgrade and a preparation method thereof, the method comprising the following steps:

[0009] Step 1: raw material pretreatment, crushing and screening red-layer soft rock fragments, controlling the particle size to be 0.075-40mm, and the proportion of fine particles with a particle size ≤0.075mm being ≤20wt%;

[0010] The crushed and screened material is placed in a drying device and dried at 105±5℃ until the moisture content is ≤1.5%;

[0011] Step 2: step-by-step composite mixing:

[0012] I. The dry red layer soft rock crushed material and coarse aggregate strengthening component are added into a high-speed mixer at a mass ratio of 5:1-10:1, and stirred at 200-400 r / min for 5-10 min;

[0013] II. The active curing agent is added, and the mass ratio of the red layer soft rock crushed material to the active curing agent is controlled to be 100:8-15, and the stirring is continued for 10-15 min;

[0014] III. The hydrophobic modification material is sprayed, and the mass ratio of the hydrophobic modification material to the red layer soft rock crushed material is controlled to be 1:20-1:30, and the spraying is uniformly carried out in the form of atomization during the stirring process, and the stirring speed is maintained at 300-500 r / min until the mixed material is in the form of uniform granules;

[0015] Step three: stabilization treatment, the mixed material is placed in a vacuum microwave reaction kettle, vacuum extraction is carried out to 0.05-0.08 MPa, 3-5 kW microwave is applied at 60-80℃ for 20-30 min, and the material is left to mature for 24-48 h;

[0016] Step four: vibration compaction forming, the matured material is filled into a mold, and is pressed and formed at a vibration frequency of 25-40 Hz and a vertical pressure of 1.5-2.5 MPa;

[0017] The active curing agent is composed of slag powder, carbide slag and sulphoaluminate cement at a mass ratio of 5:3:2, the coarse aggregate strengthening component is a mixture of basalt particles and steel slag particles with a particle size range of 2-10 mm, and the mass ratio of the basalt particles to the steel slag particles is 7:3, and the hydrophobic modification material is compounded by organosilane coupling agent, paraffin emulsion and water at a mass ratio of 1:2:7.

[0018] Preferably, in the step one:

[0019] The crushing and screening adopts a two-stage crushing process: the red layer soft rock crushed material is coarsely crushed to a particle size of ≤50 mm by a jaw crusher, and then is finely crushed to a target particle size by a cone crusher;

[0020] The screening adopts a double-layer vibrating screen, the upper layer has a screen hole size of 40 mm, and the lower layer has a screen hole size of 0.075 mm, and the screening efficiency is ≥95%;

[0021] The drying equipment is a double-heat-source circulating dryer, the hot air temperature error range is ±3℃, and the material is turned over every 20 min during the drying process.

[0022] Preferably, the preparation of the active curing agent comprises:

[0023] The slag powder: specific surface area ≥420 m 2 / kg is mixed and ground with the carbide slag: Ca(OH)2 content ≥80% to a specific surface area ≥450 m 2 / kg;

[0024] Add sulphoaluminate cement: Al203content ≥ 30% after placed in constant humidity curing box, control humidity 70% ± 5%, temperature 25 ± 2 ℃ under aging 12h;

[0025] After aging, pass 0.08mm square hole sieve, sieve residue amount ≤5%.

[0026] Preferably, in the coarse aggregate reinforcing component:

[0027] Basalt particles Mohs hardness ≥ 6, water absorption rate ≤ 1%, needle flake particle content ≤ 8%;

[0028] Steel slag particles are iron-removed by two-stage magnetic separation: magnetic induction intensity 1.2T, free calcium oxide content ≤ 3%, crushing value ≤ 15%;

[0029] Before mixing, need to be dried at 150℃ for 2h, water content control ≤ 0.5%.

[0030] Preferably, the compounding method of the hydrophobic modified material is:

[0031] Add organosilane coupling agent: KH-570 and paraffin emulsion: solid content 40% into reaction kettle, heat to 50-60℃;

[0032] After stirring at 300r / min for 20min, process by high-pressure homogenizer: pressure 35MPa for 3 times;

[0033] Slowly add deionized water and cool to 30℃, continue to stir for 40min to form uniform milky white liquid, viscosity range 80-120mPa·s.

[0034] Preferably, in the step two:

[0035] Stepwise compounding is carried out in airtight negative pressure stirring bin: pressure -0.01MPa;

[0036] When adding active curing agent in step II, spray activator at the same time, the activator is sodium hydroxide solution with concentration 5%, spraying amount is 0.5-1% of red layer soft rock crushed material mass;

[0037] The atomizing nozzle aperture in step III is 0.3mm, atomizing pressure is 0.4MPa, spraying time is 8-12min.

[0038] Preferably, in the step three:

[0039] The vacuum microwave reaction kettle is equipped with multi-mode resonant cavity, microwave frequency 2.45±0.05GHz;

[0040] During the treatment process, apply reverse pulse air pressure 0.1MPa for 30s every 5min;

[0041] Curing environment temperature 25±3℃, relative humidity ≤60%, turn over every 6h.

[0042] Preferably, in the step four:

[0043] Pre-coat the mold surface with release agent, the release agent is mixed with water-based epoxy resin: EPI-350 and methyl silicone oil at a mass ratio of 1:1, the coating thickness is 0.1-0.2mm;

[0044] Vibration compaction uses a variable frequency vibration table, the amplitude is 3-5mm, and the pressure is added in three stages:

[0045] 0-30s: pressure 1.0MPa;

[0046] 30-90s: pressure 2.0MPa;

[0047] 90-120s: pressure 2.5MPa.

[0048] Preferably, the roadbed filler includes, by mass fraction:

[0049] Red layer soft rock debris: 100 parts, coarse aggregate reinforcing component: 10-20 parts, active curing agent: 8-15 parts, hydrophobic modified material: 3.3-5 parts, and activator: 0.5-1 part.

[0050] Preferably, the performance indicators of the roadbed filler meet:

[0051] 7-day unconfined compressive strength ≥8MPa;

[0052] Saturation water state anti-disintegration rate: 48h ≤5%;

[0053] CBR value: 96h immersion ≥35%;

[0054] Freeze-thaw cycle: 15 times mass loss rate ≤3%;

[0055] Volume resistivity: wet state ≥1×10 4 Ω·m.

[0056] (Three) beneficial effects

[0057] Compared with the prior art, the present application provides a red layer soft rock roadbed filler and a preparation method thereof, which has the following beneficial effects:

[0058] 1. In the present application, through the precise process control of the step-by-step composite mixing process, the mechanical interlocking effect of the coarse aggregate strengthening component and the rock debris is first realized, then the active curing agent is introduced to stimulate the deep cementation reaction, and finally the molecular level coating of the hydrophobic modified material is cooperated, which solves the problem of weak interface bonding caused by uneven mixing of components in traditional process, forms a continuous three-dimensional network structure inside the filler, and improves the overall deformation coordination and structural density.

[0059] 2. In the present application, in the vacuum microwave stabilization treatment stage, the vacuum negative pressure environment and the multi-frequency microwave energy field are innovatively coupled to real-time control the water molecule migration rate and heat conduction efficiency inside the rock debris, inhibit the risk of molecular chain rupture caused by heat accumulation in local area by dynamic balance of temperature field distribution, and use pulse air pressure impact to strengthen the directional penetration of hydrophobic material to micropores, so that the filler still maintains stable hydrophobic performance and volume integrity under extreme wet-dry cycle environment.

[0060] 3. In the present application, based on the multi-stage pressurization strategy and mold interface optimization design of vibration compaction forming, the particle directional arrangement and interface bonding strength are controlled under high pressure vibration conditions, the basalt-steel slag skeleton effect in the coarse aggregate strengthening component and the secondary hydration reaction of the active curing agent are excited by means of specific frequency mechanical energy field input, so that the formed filler has high bearing strength and excellent stress diffusion capacity, thereby realizing long-term service stability in various extreme road environments. BRIEF DESCRIPTION OF DRAWINGS

[0061] Figure 1 The flowchart of the present application, a filler for red layer soft rock roadbed and a preparation method thereof. DETAILED DESCRIPTION

[0062] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0063] Embodiment 1: A filler for red layer soft rock roadbed and a preparation method thereof, the method comprising the following steps:

[0064] Step one: raw material pretreatment, crushing and screening the red layer soft rock debris, controlling the particle size to be 0.075 mm, and the proportion of fine particles with a particle size ≤0.075 mm being ≤20wt%;

[0065] The screened debris is placed in a drying equipment and dried at 100℃ to a moisture content ≤1.5%;

[0066] Step two: step-by-step composite mixing:

[0067] I. The dry red layer soft rock crushed material and coarse aggregate strengthening component are added to a high-speed mixer at a mass ratio of 5:1, and stirred at 200 r / min for 5 min;

[0068] II. Add active curing agent, control the mass ratio of red layer soft rock crushed material to active curing agent to be 100:8, continue to stir for 10 min;

[0069] III. Spray hydrophobic modification material, control the mass ratio of hydrophobic modification material to red layer soft rock crushed material to be 1:20, and uniformly spray in the form of atomization during stirring, maintain the stirring speed at 300 r / min until the mixed material becomes uniform granular;

[0070] Step three: stabilization treatment, place the mixed material in a vacuum microwave reaction kettle, vacuum to 0.05 MPa, apply 3 kW microwave at 60°C for 20 min, and stand for 24 h;

[0071] Step four: vibration compaction forming, fill the cured material into the mold, and press form at a vibration frequency of 25 Hz and a vertical pressure of 1.5 MPa;

[0072] The active curing agent is composed of slag powder, carbide slag and sulphoaluminate cement at a mass ratio of 5:3:2, the coarse aggregate strengthening component is a mixture of basalt particles and steel slag particles with a particle size range of 2-10 mm, and the mass ratio of basalt particles to steel slag particles is 7:3, and the hydrophobic modification material is compounded by organosilane coupling agent, paraffin emulsion and water at a mass ratio of 1:2:7.

[0073] In step one:

[0074] The crushing and screening adopts a two-stage crushing process: first, the red layer soft rock crushed material is coarsely crushed to a particle size of ≤50 mm by a jaw crusher, and then finely crushed to the target particle size by a cone crusher;

[0075] The screening adopts a double-layer vibrating screen, the upper layer screen hole size is 40 mm, and the lower layer screen hole size is 0.075 mm, and the screening efficiency is ≥95%;

[0076] The drying equipment is a double-heat source circulating dryer, the hot air temperature error range is ±3°C, and the material is turned over every 20 min during the drying process.

[0077] The preparation of the active curing agent includes:

[0078] Mix the slag powder with a specific surface area of ≥420 m 2 / kg and carbide slag with Ca(OH)2 content of ≥80% to a specific surface area of ≥450 m 2 / kg;

[0079] After adding sulphoaluminate cement: Al2O3 content ≥ 30%, place in a constant humidity curing box, control humidity 70% ± 5%, temperature 25 ± 2℃, and age for 12h;

[0080] After aging, pass through a 0.08mm square hole sieve, and the amount of sieve residue is ≤5%.

[0081] In the coarse aggregate strengthening component:

[0082] The Mohs hardness of the basalt particles is ≥ 6, the water absorption is ≤ 1%, and the content of needle and flake particles is ≤ 8%;

[0083] The steel slag particles are subjected to two-stage magnetic separation to remove iron: magnetic induction intensity 1.2T, free calcium oxide content ≤ 3%, and crushing value ≤ 15%;

[0084] Before mixing, dry at 150℃ for 2h, and control the water content to ≤ 0.5%.

[0085] The compounding method of the hydrophobic modification material is:

[0086] Add the organosilane coupling agent: KH-570 and the paraffin emulsion: solid content 40% into a reaction kettle, and heat to 50℃;

[0087] After stirring at 300r / min for 20min, treat by a high-pressure homogenizer: pressure 35MPa for 3 cycles;

[0088] Slowly add deionized water and cool to 30℃, continue stirring for 40min until a uniform milky white liquid is formed, and the viscosity is 80mPa·s.

[0089] In step two:

[0090] The stepwise compounding is carried out in a closed negative pressure stirring bin: pressure -0.01MPa.

[0091] When the active curing agent is added in step II, simultaneously spray the activator, which is a sodium hydroxide solution with a concentration of 5%, and the spraying amount is 0.5% of the mass of the red layer soft rock fragments;

[0092] The atomizing nozzle aperture in step III is 0.3mm, the atomizing pressure is 0.4MPa, and the spraying time is 8min.

[0093] In step three:

[0094] The vacuum microwave reaction kettle is equipped with a multimode resonant cavity, and the microwave frequency is 2.45±0.05GHz;

[0095] During the treatment process, apply a reverse pulse gas pressure of 0.1MPa for 30s every 5min;

[0096] The curing environment temperature is 25±3℃, and the relative humidity is ≤ 60%, and turn over the heap every 6h.

[0097] In step four:

[0098] The mold surface is pre-coated with a release agent, which is a mixture of water-based epoxy resin: EPI-350 and methyl silicone oil at a mass ratio of 1:1, with a coating thickness of 0.1 mm;

[0099] Vibration compaction uses a variable frequency vibration table, with an amplitude of 3-5 mm, and three-stage pressure:

[0100] 0-30s: pressure 1.0 MPa;

[0101] 30-90s: pressure 2.0 MPa;

[0102] 90-120s: pressure 2.5 MPa.

[0103] The roadbed filler includes, by mass fraction:

[0104] Red layer soft rock fragments: 100 parts, coarse aggregate strengthening component: 10 parts, active curing agent: 8 parts, hydrophobic modified material: 3.3 parts, and activator: 0.5 parts.

[0105] The performance indicators of the roadbed filler meet:

[0106] 7-day unconfined compressive strength ≥ 8 MPa;

[0107] Saturation water state anti-disintegration rate: 48h ≤ 5%;

[0108] CBR value: 96h immersion ≥ 35%;

[0109] Freeze-thaw cycle: 15 times mass loss rate ≤ 3%;

[0110] Volume resistivity: wet state ≥ 1 × 10 4 Ω·m.

[0111] Example 2: A red layer soft rock roadbed filler and its preparation method, the method comprising the following steps:

[0112] Step one: raw material pretreatment, crushing and screening the red layer soft rock fragments, controlling the particle size to be 20 mm, and the fine particles with a particle size ≤ 0.075 mm accounting for ≤ 20wt%;

[0113] The screened fragments are placed in a drying equipment and dried at 105℃ to a moisture content ≤ 1.5%;

[0114] Step two: step-by-step composite mixing:

[0115] I. The dried red layer soft rock fragments and coarse aggregate strengthening component are added to a high-speed mixer at a mass ratio of 7:1, and stirred at 300r / min for 8min;

[0116] II. Add active curing agent, control the mass ratio of red layer soft rock aggregate and active curing agent to be 100:12, continue to stir for 13 min;

[0117] III. Spray hydrophobic modification material, control the mass ratio of hydrophobic modification material and red layer soft rock aggregate to be 1:25, and spray uniformly in atomized form during stirring, maintain the stirring speed at 400 r / min until the mixture is in uniform granular form;

[0118] Step three: stabilization treatment, place the mixture in a vacuum microwave reaction kettle, vacuum to 0.07 MPa, apply 4 kW microwave at 70°C for 25 min, and stand for 36 h;

[0119] Step four: vibration compaction forming, fill the cured material into the mold, and press form at a vibration frequency of 35 Hz and a vertical pressure of 2.0 MPa;

[0120] The active curing agent is composed of slag powder, carbide slag, and sulphoaluminate cement in a mass ratio of 5:3:2, the coarse aggregate strengthening component is a mixture of basalt particles and steel slag particles with a particle size range of 2-10 mm, and the mass ratio of basalt particles to steel slag particles is 7:3, and the hydrophobic modification material is compounded by organosilane coupling agent, paraffin emulsion, and water in a mass ratio of 1:2:7.

[0121] In step one:

[0122] The crushing and screening adopts a two-stage crushing process: first, the red layer soft rock aggregate is coarsely crushed to a particle size of ≤50 mm by a jaw crusher, and then finely crushed to the target particle size by a cone crusher;

[0123] The screening uses a double-layer vibrating screen with a screen size of 40 mm on the upper layer and 0.075 mm on the lower layer, and the screening efficiency is ≥95%;

[0124] The drying equipment is a double-heat source circulating dryer, and the hot air temperature error range is ±3°C, and the material is turned over every 20 min during the drying process.

[0125] The preparation of the active curing agent includes:

[0126] Mix slag powder with a specific surface area of ≥420 m 2 / kg and carbide slag with Ca(OH)2 content of ≥80% to a specific surface area of ≥450 m 2 / kg;

[0127] After adding sulphoaluminate cement with Al2O3 content of ≥30%, place it in a constant humidity curing box, control the humidity to 70%±5% and the temperature to 25±2°C, and age for 12 h;

[0128] After aging, pass through a 0.08 mm square hole screen, and the screen residue amount is ≤5%.

[0129] In the coarse aggregate strengthening component:

[0130] The basalt particles have a Mohs hardness of ≥6, a water absorption rate of ≤1%, and a content of needle-like and flaky particles of ≤8%.

[0131] Steel slag particles undergo two-stage magnetic separation to remove iron: magnetic induction intensity 1.2T, free calcium oxide content ≤3%, crushing value ≤15%;

[0132] Before mixing, the mixture needs to be dried at 150℃ for 2 hours, with a moisture content controlled at ≤0.5%.

[0133] The compounding method for hydrophobic modified materials is as follows:

[0134] The organosilane coupling agent KH-570 and paraffin emulsion with a solid content of 40% were added to the reaction vessel and heated to 55°C.

[0135] After stirring at 300 r / min for 20 min, the mixture was circulated three times using a high-pressure homogenizer at a pressure of 35 MPa.

[0136] Slowly add deionized water and cool to 30°C. Continue stirring for 40 minutes until a uniform milky white liquid with a viscosity of 100 mPa·s is formed.

[0137] In step two:

[0138] The stepwise compound mixing is carried out in a closed negative pressure mixing chamber at a pressure of -0.01 MPa;

[0139] When adding the active curing agent in step II, the activator is sprayed simultaneously. The activator is a 5% sodium hydroxide solution, and the spraying amount is 0.8% of the mass of the red bed soft rock fragments.

[0140] Step III uses an atomizing nozzle with an orifice diameter of 0.3 mm, an atomization pressure of 0.4 MPa, and an injection time of 10 min.

[0141] In step three:

[0142] The vacuum microwave reactor is equipped with a multimode resonant cavity and a microwave frequency of 2.45±0.05GHz;

[0143] During the treatment, a reverse pulse pressure of 0.1 MPa is applied every 5 minutes for 30 seconds.

[0144] The curing environment temperature is 25±3℃, the relative humidity is ≤60%, and the pile is turned over every 6 hours.

[0145] In step four:

[0146] The mold surface is pre-coated with a release agent, which is a mixture of water-based epoxy resin, EPI-350 and methyl silicone oil in a 1:1 mass ratio, with a coating thickness of 0.15 mm.

[0147] Vibration compaction adopts variable frequency vibration table, amplitude 3-5mm, three-stage pressure:

[0148] 0-30s: pressure 1.0MPa;

[0149] 30-90s: pressure 2.0MPa;

[0150] 90-120s: pressure 2.5MPa.

[0151] The filling material for subgrade comprises, by mass fraction:

[0152] Red layer soft rock fragments: 100 parts, coarse aggregate reinforcing component: 15 parts, active curing agent: 12 parts, hydrophobic modified material: 4.5 parts, and activator: 0.8 parts.

[0153] The performance index of the filling material for subgrade meets:

[0154] 7-day unconfined compressive strength ≥8MPa;

[0155] Saturation water state anti-disintegration rate: 48h≤5%;

[0156] CBR value: 96h immersion ≥35%;

[0157] Freeze-thaw cycle: 15 times mass loss rate ≤3%;

[0158] Volume resistivity: humid state ≥1×10 4 Ω·m.

[0159] Example 3: A red layer soft rock filling material for subgrade and a preparation method thereof, the method comprising the following steps:

[0160] Step one: raw material pretreatment, crushing and screening the red layer soft rock fragments, controlling the particle size to be 40mm, and the fine particles with particle size ≤0.075mm accounting for ≤20wt%;

[0161] The screened fragments are placed in a drying equipment and dried at 110℃ to a water content of ≤1.5%;

[0162] Step two: step-by-step composite mixing:

[0163] Ⅰ, the dried red layer soft rock fragments and the coarse aggregate reinforcing component are added into a high-speed mixer at a mass ratio of 10:1, and stirred at 400r / min for 10min;

[0164] Ⅱ, the active curing agent is added, and the mass ratio of the red layer soft rock fragments to the active curing agent is controlled to be 100:15, and the stirring is continued for 10-15min;

[0165] III. Spray hydrophobic modification material, control the mass ratio of hydrophobic modification material and red layer soft rock fragments to be 1:30, and spray uniformly in atomized form during stirring, and maintain the stirring speed to be 500 r / min until the mixture is in uniform pellet form;

[0166] Step three: stabilization treatment, place the mixture in a vacuum microwave reaction kettle, vacuumize to 0.08 MPa, apply 5 kW microwave at 80 DEG C for 30 min, and stand for 48 h;

[0167] Step four: vibration compaction forming, fill the cured material into a mold, and press form at a vibration frequency of 40 Hz and a vertical pressure of 2.5 MPa;

[0168] The active curing agent is composed of slag powder, carbide slag and sulphoaluminate cement in a mass ratio of 5:3:2, the coarse aggregate strengthening component is a mixture of basalt particles and steel slag particles with a particle size range of 2-10 mm, and the mass ratio of basalt particles to steel slag particles is 7:3, and the hydrophobic modification material is compounded by organosilane coupling agent, paraffin emulsion and water in a mass ratio of 1:2:7

[0169] In step one:

[0170] The crushing and screening adopts a two-stage crushing process: the red layer soft rock fragments are coarsely crushed to a particle size of ≤50 mm by a jaw crusher, and then finely crushed to a target particle size by a cone crusher;

[0171] The screening adopts a double-layer vibrating screen, the upper layer has a screen hole size of 40 mm, and the lower layer has a screen hole size of 0.075 mm, and the screening efficiency is ≥95%;

[0172] The drying equipment is a double-heat-source circulating dryer, the hot air temperature error range is ±3 DEG C, and the material is turned over every 20 min during the drying process.

[0173] The preparation of the active curing agent includes:

[0174] The slag powder with a specific surface area of ≥420 m 2 / kg is mixed and ground with the carbide slag with a Ca(OH)2 content of ≥80% to a specific surface area of ≥450 m 2 / kg;

[0175] After the sulphoaluminate cement with an Al2O3 content of ≥30% is added, it is placed in a constant humidity curing box, and aged for 12 h under the conditions of a humidity of 70%±5% and a temperature of 25±2 DEG C;

[0176] After aging, pass through a 0.08 mm square hole screen, and the screen residue amount is ≤5%.

[0177] In the coarse aggregate strengthening component:

[0178] The Mohs hardness of the basalt particles is ≥6, the water absorption is ≤1%, and the content of needle and flaky particles is ≤8%.

[0179] The steel slag particles are subjected to two-stage magnetic separation for removing iron: magnetic induction intensity 1.2T, free calcium oxide content ≤3%, and crushing value ≤15%;

[0180] Before mixing, the mixture is dried at 150℃ for 2h, and the water content is controlled to be ≤0.5%.

[0181] The compounding method of the hydrophobic modified material is as follows:

[0182] The organosilane coupling agent KH-570 and the paraffin emulsion with a solid content of 40% are added into a reaction kettle, and the temperature is raised to 60℃;

[0183] After stirring at 300r / min for 20min, the mixture is subjected to circulation treatment for 3 times by a high-pressure homogenizer with a pressure of 35MPa.

[0184] Deionized water is slowly added, and the temperature is lowered to 30℃, and the stirring is continued for 40min until a uniform milky white liquid is formed, and the viscosity is 120mPa·s.

[0185] In step two:

[0186] The stepwise compounding and mixing are carried out in a closed negative pressure stirring bin with a pressure of-0.01MPa.

[0187] In step II, the active curing agent is added, and a trigger agent is sprayed synchronously, the trigger agent is a sodium hydroxide solution with a concentration of 5%, and the spraying amount is 1% of the mass of the red layer soft rock fragments;

[0188] In step III, the orifice diameter of the atomizing nozzle is 0.3mm, the atomizing pressure is 0.4MPa, and the spraying time is 12min.

[0189] In step three:

[0190] The vacuum microwave reaction kettle is equipped with a multimode resonant cavity, and the microwave frequency is 2.45±0.05GHz.

[0191] During the treatment process, a reverse pulse gas pressure of 0.1MPa is applied every 5min for 30s.

[0192] The curing environment temperature is 25±3℃, and the relative humidity is ≤60%, and the pile is turned over every 6h.

[0193] In step four:

[0194] The mold surface is pre-coated with a release agent, the release agent is a mixture of water-based epoxy resin EPI-350 and methyl silicone oil at a mass ratio of 1:1, and the coating thickness is 0.2mm.

[0195] The vibration compaction uses a variable frequency vibration table, and the amplitude is 3-5mm, and the pressure is added in three stages:

[0196] 0-30s: pressure 1.0MPa;

[0197] 30-90s: pressure 2.0 MPa;

[0198] 90-120s: pressure 2.5 MPa.

[0199] The filling material for subgrade comprises, by mass fraction:

[0200] Red-layer soft rock aggregate: 100 parts, coarse aggregate reinforcing component: 20 parts, active curing agent: 15 parts, hydrophobic modification material: 5 parts, and activator: 1 part.

[0201] The performance index of the filling material for subgrade satisfies:

[0202] 7-day unconfined compressive strength: ≥8 MPa;

[0203] Saturation water state anti-disintegration rate: 48h≤5%;

[0204] CBR value: 96h after immersion: ≥35%;

[0205] Freeze-thaw cycle: 15 times, mass loss rate: ≤3%;

[0206] Volume resistivity: in wet state: ≥1×10 4 Ω·m.

[0207] Comparative Example 1, which differs from Example 1 in that no coarse aggregate reinforcing component is added in the preparation process.

[0208] Comparative Example 2, which differs from Example 1 in that the vacuum microwave stabilization treatment is omitted in the stepwise composite mixing.

[0209] Comparative Example 3, which differs from Example 1 in that the stepwise mixing order is changed: the hydrophobic modification material is sprayed first, and then the active curing agent is added.

[0210] Comparative Example 4, which differs from Example 1 in that the hydrophobic modification material is not compounded with paraffin emulsion, but only uses an organic silane coupling agent.

[0211] The red-layer soft rock subgrade filling materials prepared in Examples 1-3 and Comparative Examples 1-4 are subjected to performance testing:

[0212] 7-day unconfined compressive strength: universal testing machine loading rate 1mm / min;

[0213] Saturation water anti-disintegration rate: after the sample is immersed in water for 48h, it is dried and the mass loss percentage is calculated;

[0214] CBR value: penetration test after immersion for 96h;

[0215] Freeze-thaw cycle mass loss rate: 15 times of freeze-thaw at-20℃.

[0216] The performance test data of the red layer soft rock subgrade filler prepared by Examples 1-3 and Comparative Examples 1-4 are recorded in the following table:

[0217]

[0218]

[0219] By comparing and analyzing the data in the table, it can be seen that the red layer soft rock subgrade filler prepared by the process of Examples 1-3 has more excellent performance than that of Comparative Examples 1-4, which shows that the slag micro-powder in the active curing agent releases the cementitious activity under the alkaline activation of the sulphoaluminate cement, and polymerizes with the silicoaluminate on the surface of the red layer soft rock to form a high-strength ettringite crystal structure; the basalt particles and steel slag particles of the coarse aggregate strengthening component form a gradient skeleton, which suppresses the displacement of rock particle during the vibration compaction process through the mechanical interlocking effect, and improves the deformation resistance; the water in the rock pore is forced to migrate directionally in the vacuum negative pressure environment, and the active curing agent is deeply hydrated by the synchronous microwave energy field, and the generated ettringite network penetrates the rock-particle interface; the periodic pulse air pressure breaks the disordered growth of the hydration product, and promotes the directional arrangement of the needle-shaped crystal, and builds a crack-resistant reinforced skeleton; the organosilane coupling agent forms a chemical bond hydrophobic layer by condensation of alkoxy with the hydroxyl group on the surface of the rock particle; the paraffin emulsion fills the micro-cracks after high-temperature melting, and forms a physical sealing barrier after cooling and solidification, and the two form a "molecule-pore" level synergistic waterproof system to block the water permeation path.

[0220] By comparing and analyzing the relevant data in the table, it can be seen that the red layer soft rock subgrade filler prepared by the forming process of the present application not only has high strength bearing property, excellent water stability and long-term durability. It is thus shown that the red layer soft rock subgrade filler and the preparation method thereof provided by the present application have a broader market prospect and are more suitable for promotion.

[0221] It should be noted that, in this text, relational terms such as first and second are used merely to distinguish one entity or action from another, and do not necessarily require or imply that there is any such actual relationship or order between these entities or actions. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. Without more limitations, the element defined by the statement "including a" does not exclude the presence of other identical elements in the process, method, article or equipment including the element.

[0222] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary of the principles and application of the present application. Numerous modifications and adaptions can be effected without departing from the spirit and scope of the present application, which is not limited to the exact construction and arrangement described. It is intended, therefore, to cover all modifications and adaptions that fall within the scope of the claims and their equivalents.

Claims

1. A method for preparing filler for red bed soft rock roadbed, characterized in that: Includes the following steps: Step 1: Raw material pretreatment. The red bed soft rock fragments are crushed and screened to control the particle size to 0.075-40mm, with fine particles ≤0.075mm accounting for ≤20wt%. The sieved fragments are placed in a drying device and dried at 105±5℃ until the moisture content is ≤1.5%; Step Two: Step-by-Step Compound Mixing Ⅰ. Add the dried red bed soft rock fragments and coarse aggregate reinforcing components to a high-speed mixer at a mass ratio of 5:1-10:1, and mix at 200-400 r / min for 5-10 min; II. Add the active curing agent, and control the mass ratio of red bed soft rock fragments to active curing agent to be 100:8-15, and continue stirring for 10-15 minutes; Ⅲ. Spray in the hydrophobic modifier, controlling the mass ratio of the hydrophobic modifier to the red bed soft rock fragments to be 1:20-1:30, and spray it in atomized form evenly during the mixing process, maintaining the mixing speed at 300-500 r / min until the mixture is in uniform granular form. Step 3: Stabilization treatment. Place the mixture in a vacuum microwave reactor, evacuate to 0.05-0.08 MPa, apply 3-5 kW microwaves at 60-80℃ for 20-30 min, and let it stand and mature for 24-48 h. Step 4: Vibration compaction molding. Fill the mold with the cured material and press it into shape with a vibration frequency of 25-40Hz and a vertical pressure of 1.5-2.5MPa. The active curing agent is composed of slag powder, carbide slag and sulfoaluminate cement in a mass ratio of 5:3:

2. The coarse aggregate reinforcing component is a mixture of basalt particles and steel slag particles with a particle size range of 2-10mm and a mass ratio of basalt particles to steel slag particles of 7:

3. The hydrophobic modification material is compounded by organosilane coupling agent, paraffin emulsion and water in a mass ratio of 1:2:

7. In step two: The stepwise compound mixing is carried out in a closed negative pressure mixing chamber at a pressure of -0.01 MPa; In step II, an activator is sprayed simultaneously when adding the active curing agent. The activator is a 5% sodium hydroxide solution, and the spraying amount is 0.5-1% of the mass of the red bed soft rock fragments. Step III uses an atomizing nozzle with an orifice diameter of 0.3 mm, an atomization pressure of 0.4 MPa, and an injection time of 8-12 min.

2. The method for preparing filler for red bed soft rock roadbed according to claim 1, characterized in that: In step one: The crushing and screening process adopts a two-stage crushing process: first, the red soft rock material is coarsely crushed to a particle size of ≤50mm by a jaw crusher, and then finely crushed to the target particle size by a cone crusher; The screening process uses a double-layer vibrating screen, with an upper screen aperture of 40mm and a lower screen aperture of 0.075mm, achieving a screening efficiency of ≥95%. The drying equipment is a dual-heat-source circulating dryer with a hot air temperature error range of ±3℃. The material is turned over every 20 minutes during the drying process.

3. The method for preparing filler for red bed soft rock roadbed according to claim 1, characterized in that: The preparation of the active curing agent includes: Mix slag powder (specific surface area ≥ 420 m² / kg) with calcium carbide slag. Mix and grind products with a content ≥80% until the specific surface area is ≥450m² / kg; Add sulfoaluminate cement: After the content is ≥30%, place it in a constant humidity curing box and age it for 12 hours at a humidity of 70%±5% and a temperature of 25±2℃. After aging, the residue after passing through a 0.08mm square hole sieve is ≤5%.

4. The method for preparing filler for red bed soft rock roadbed according to claim 1, characterized in that: In the coarse aggregate strengthening component: The basalt particles have a Mohs hardness of ≥6, a water absorption rate of ≤1%, and a content of needle-like and flaky particles of ≤8%. Steel slag particles undergo two-stage magnetic separation to remove iron: magnetic induction intensity 1.2T, free calcium oxide content ≤3%, crushing value ≤15%; Before mixing, the mixture needs to be dried at 150℃ for 2 hours, with the moisture content controlled to ≤0.5%.

5. The method for preparing filler for red bed soft rock roadbed according to claim 1, characterized in that: The compounding method of the hydrophobic modified material is as follows: Add organosilane coupling agent KH-570 and paraffin emulsion (solid content 40%) to the reactor and heat to 50-60℃. After stirring at 300 r / min for 20 min, the mixture was circulated three times using a high-pressure homogenizer at a pressure of 35 MPa. Slowly add deionized water and cool to 30°C. Continue stirring for 40 minutes until a uniform milky white liquid is formed with a viscosity range of 80-120 mPa·s.

6. The method for preparing filler for red bed soft rock roadbed according to claim 1, characterized in that: In step three: The vacuum microwave reactor is equipped with a multimode resonant cavity and a microwave frequency of 2.45±0.05GHz; During the treatment, a reverse pulse pressure of 0.1 MPa is applied every 5 minutes for 30 seconds. The curing environment temperature is 25±3℃, the relative humidity is ≤60%, and the pile is turned over every 6 hours.

7. The method for preparing filler for red bed soft rock roadbed according to claim 1, characterized in that: In step four: The mold surface is pre-coated with a release agent, which is a mixture of water-based epoxy resin, EPI-350 and methyl silicone oil in a 1:1 mass ratio, with a coating thickness of 0.1-0.2 mm. Vibratory compaction uses a variable frequency vibratory table with an amplitude of 3-5mm, applied in three stages: 0-30s: Pressure 1.0MPa; 30-90s: Pressure 2.0MPa; 90-120s: Pressure 2.5MPa.

8. A filler for red bed soft rock roadbed prepared by the method described in any one of claims 1-7, characterized in that: The filler material for the red bed soft rock roadbed comprises, by mass parts: Red bed soft rock aggregate: 100 parts, coarse aggregate reinforcing component: 10-20 parts, active curing agent: 8-15 parts, hydrophobic modifier: 3.3-5 parts, and activator: 0.5-1 parts.

9. A filler for red bed soft rock roadbed according to claim 8, characterized in that: Its performance indicators meet the following requirements: 7-day unconfined compressive strength ≥8MPa; Anti-disintegration rate in saturated water state: ≤5% after 48 hours; CBR value: ≥35% after immersion in water for 96 hours; Freeze-thaw cycles: mass loss rate ≤3% after 15 cycles; Volume resistivity: ≥1×10⁻⁶ under humid conditions 4 Ω·m.

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