Roadbed slope protection composition based on solid waste-geopolymer and construction method thereof

Abstract

The invention relates to the technical field of roadbed slope protection, discloses a roadbed slope protection composition based on solid waste-geopolymer and a construction method of the roadbed slope protection composition, and aims to solve the problems of high carbon emission, low solid waste utilization rate, strong ecological destructiveness and weak disaster resistance of a traditional roadbed slope protection material. According to the invention, fly ash, desulfurized gypsum, mineral powder and pretreated red mud are taken as core raw materials, and are matched with a geopolymer activator and a heavy metal stabilizer to form a cement-free flow state system with a high solid waste mixing ratio; during construction, a casing pipe is not needed, through the drilling-layered pouring technology, the solidification body is naturally attached to soil through the fluidity, a multi-deformation solidification structure without rigid cutting is formed, the anti-scouring and anti-collapse capacity of a roadbed slope can be enhanced through the structure, damage of natural disasters such as flood to a roadbed can be effectively resisted, and the construction period is shortened. Meanwhile, the ecological compatibility of the mechanical property and the plant root system penetration rate is considered.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of roadbed slope protection, in particular to a roadbed slope protection composition based on solid waste-geopolymer and a construction method thereof. BACKGROUND

[0002] The roadbed slope protection is a key structure for ensuring the safe operation of highways and railways. Traditional technologies mostly use rigid materials such as mortar rubble and concrete precast piles, and rely on cement as the core cementitious material. However, these traditional technologies have the problems of high carbon emission, low solid waste utilization rate, and insufficient ecological compatibility, and also have significant defects in natural disaster prevention and control.

[0003] 1. Weak disaster resistance: The traditional precast pile has a "rigid split interface" with the soil, which is easy to form a water flow channel during flood erosion, leading to the separation of the pile body and the soil, and further causing slope collapse. The mortar rubble structure has large gaps, which are easy to cause the mortar to loosen after the flood penetrates, and are difficult to resist continuous erosion.

[0004] 2. Difficulty in post-disaster repair: The traditional slope protection structure needs to be demolished and rebuilt after damage, which consumes materials and time, and the repair process is easy to aggravate the secondary damage to the roadbed.

[0005] 3. Insufficient adaptability: The roadbed slope in flood-prone areas needs to balance the "erosion resistance" and "ecological water permeability". Traditional materials are either too rigid and easy to break, or have poor water permeability, leading to soil water accumulation, and cannot balance the two requirements.

[0006] 4. Reliance on cement and low solid waste utilization rate: Existing flow state solidified soil technology mostly needs cement to improve strength, but the cement-based structure has limited anti-freezing and anti-erosion performance, and the solid waste mixing ratio is low, making it difficult to achieve the goals of "disaster resistance, low carbon, and solid waste utilization" simultaneously. SUMMARY

[0007] In view of the above technical deficiencies, the present application aims to provide a roadbed slope protection composition based on solid waste-geopolymer and a construction method thereof, which optimizes the geopolymer activation system and multi-solid waste ratio embedding, removes cement, and constructs a multi-deformation structure that cooperates with the soil to resist disasters, thereby improving the roadbed's resistance to disasters such as floods and landslides.

[0008] To solve the above technical problems, the present application adopts the following technical solutions:

[0009] The roadbed slope protection composition based on solid waste-geopolymer, by weight, the raw material composition includes: fly ash 38-48 parts, desulfurization gypsum 16-22 parts, S95 grade mineral powder 12-16 parts, pretreated red mud 9-13 parts, geopolymer activator 7-9 parts, water 19-23 parts, and sodium sulfide 0.6-1.2 parts.

[0010] Further, the pretreated red mud is red mud neutralized by 5%-8% ferrous sulfate for 24 hours and screened to a particle size of less than or equal to 5 mm; and the geopolymer activator is a composite system of sodium water glass and sodium hydroxide, wherein the mass ratio of sodium water glass to sodium hydroxide is 2:1-1.8:1.

[0011] Further, the composition forms a gradient transition layer with a thickness of 10-20 mm after contacting with the soil, and retains micro pores with a pore size of 0.1-0.5 mm after hardening.

[0012] The application also relates to a construction method of the roadbed slope protection composition.

[0013] S1: solid waste pretreatment: red mud is neutralized by ferrous sulfate in a proportion, and screened; desulfurized gypsum is dried to a water content of less than or equal to 15%; and pulverized coal ash and mineral powder are screened through an 80-mesh sieve;

[0014] S2: preparation of a solidified body: the pulverized coal ash, desulfurized gypsum, mineral powder and pretreated red mud are dry-mixed for 2-3 minutes, the geopolymer activator and water are wet-mixed for 5-8 minutes, the slump and initial setting time are detected, and the solidified body is ready for use after meeting the standards;

[0015] S3: drilling and pouring: a spiral drill is used to drill holes in a plum blossom shape along the roadbed slope, the hole diameter is 120-150 mm, the hole depth is 1.5-2.0 m, after hole cleaning, the roadbed slope protection composition is poured in layers, each layer has a height of 30-40 cm, the composition is naturally attached to the soil by gravity to form a scour-resistant structure; the plum blossom-shaped holes are densified by 10%-15% at the slope toe area to form a reinforced disaster-resistant belt, the lateral spacing is 700-850 mm, and the longitudinal spacing is 900-1050 mm;

[0016] S4: maintenance and detection: a breathable and moisture-retaining film is covered for maintenance for 10-14 days, the compressive strength, shear strength and scour loss rate are detected after 28 days, and the slope vegetation is restored after meeting the standards.

[0017] Further, in the step S3, the lateral spacing of the conventional area drilling is 800-1000 mm, the longitudinal spacing is 1000-1200 mm, the residual slag soil after hole cleaning is less than or equal to 5%, and the roadbed slope protection composition and the soil form a continuous disaster-resistant protective layer after pouring, without the need for vibration and casing.

[0018] Further, in the step S4, the soil is watered once a day for 3 days before maintenance, the drilling core integrity is greater than or equal to 90% when detected, the scour loss rate is less than or equal to 5%, and the difference in the permeability coefficient is less than or equal to 1x10 -8 cm / s.

[0019] The application has the beneficial effects that: the application constructs a multi-deformation structure that cooperates with the soil to resist disasters by strengthening the compactness of the geopolymer gel product and the embedding degree of the multiple solid wastes, removes cement, and improves the resistance of the roadbed to disasters such as floods and landslides; both solid waste reduction, low-carbon reinforcement, and ecological restoration are achieved, and the roadbed slope resistance to flood scouring and landslides is enhanced, and the damage of natural disasters to highway and railway construction is reduced. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0021] EMBODIMENT

[0022] The roadbed slope protection composition based on solid waste-geopolymer includes, in parts by weight, fly ash 38-48 parts, desulfurization gypsum 16-22 parts, S95 grade mineral powder 12-16 parts, pretreated red mud 9-13 parts, geopolymer activator 7-9 parts, water 19-23 parts, and sodium sulfide 0.6-1.2 parts; the pretreated red mud is red mud neutralized by 5%-8% ferrous sulfate for 24 hours and sieved to a particle size of less than or equal to 5 mm; the geopolymer activator is a composite system of sodium water glass and sodium hydroxide (mass ratio 2:1-1.8:1); the roadbed slope protection composition has a slump of 160-190 mm, an initial setting time of 4-6 hours, a 28-day compressive strength of greater than or equal to 4.8 MPa, a shear strength of greater than or equal to 1.1 MPa, a scouring loss rate of less than or equal to 5% (after a simulated flood scouring test), and a heavy metal leaching amount of less than or equal to 0.1 mg / L; after the roadbed slope protection composition contacts the soil, a “gradient transition layer” (thickness 10-20 mm) is formed, the hardened composition retains micro-pores with a pore size of 0.1-0.5 mm, the plant root penetration rate is greater than or equal to 80%, the difference in the permeability coefficient between the solidified body and the soil interface is less than or equal to 1x10 -8 cm / s, and the overall structure can cooperate with the soil to resist flood scouring and prevent landslides.

[0023] The fly ash in the composition of the roadbed slope protection composition in this embodiment is a silicon-aluminum core source, which reacts with the geopolymer to generate a dense zeolite-like structure, thereby improving the scouring resistance of the solidified body; the spherical particle morphology optimizes the workability of the solidified body, ensures close adhesion with the soil, and avoids the penetration of flood into the interface; the desulfurization gypsum in the composition reacts with the geopolymer to generate ettringite, which fills the internal pores of the solidified body and reduces the water permeability (permeability coefficient less than or equal to 1x10 -7cm / s), reduce the flood penetration damage to the soil; At the same time, the initial setting time is prolonged to 4-6h, which ensures that the pouring is fully attached to the soil to form a continuous disaster-resistant layer; The S95 grade mineral powder is a high-activity calcium-silicon component, which improves the freeze-thaw resistance and fatigue resistance of the solidified body. Flood-prone areas are often accompanied by temperature changes, and the mineral powder can enhance the strength stability of the solidified body after dry-wet and freeze-thaw cycles, avoiding structural cracking; The composition pretreated red mud is neutralized (pH is reduced to 7.5-8.5) by ferrous sulfate, and the flaky particles can be interlaced and embedded with soil particles, enhancing the interfacial adhesion between the solidified body and the soil, and preventing peeling during flood erosion; The composition of the geopolymer activator is compounded by sodium water glass (modulus 3.2) and sodium hydroxide (concentration 30%) according to the mass ratio of 2:1-1.8:1, and the activation efficiency is improved by 30% compared with the traditional one. The generated cementitious product has excellent compressive and shear resistance, ensuring that the solidified body is not easily broken under flood impact; The composition of sodium sulfide stabilizes trace heavy metals in red mud, avoiding heavy metal leakage caused by flood erosion, and considering disaster resistance and environmental protection; The composition of water is used to control the slump of 160-190mm, ensuring the flowability of the solidified body to fill the soil pores and form a non-dead-angle anti-erosion structure, while avoiding excessive water quantity leading to strength reduction of the solidified body.

[0024] The construction method of the roadbed slope protection composition of the present embodiment is as follows:

[0025] S1: solid waste pretreatment;

[0026] Red mud treatment: 5%-8% ferrous sulfate powder is added according to the weight of red mud, and water is added for stirring until it is paste-like. After standing for 24h, the alkalinity is neutralized (pH is reduced to 7.5-8.5), and then it is crushed by a jaw crusher and sieved by an 80-mesh sieve to ensure that the particle size is ≤5mm;

[0027] Desulfurized gypsum treatment: put into a 105℃ drying oven and dry for 4h to remove free water to a water content of ≤15%, and screen out impurities with particle size >3mm;

[0028] Fly ash and mineral powder treatment: directly pass through an 80-mesh sieve to remove coarse particles and ensure uniformity of raw materials.

[0029] S2: solidified body preparation;

[0030] Dry mixing stage: put fly ash, desulfurized gypsum, mineral powder, and pretreated red mud into a forced mixer, rotate at 150r / min, and dry mix for 2-3min until the color is uniform;

[0031] Wet mixing stage: Add geopolymeric activator and water, adjust the speed to 200 r / min, wet mix for 5-8 min, take sample to detect slump (160-190 mm) and initial setting time (4-6 h) during the period, if the slump is insufficient, add 1-2 parts of water, if the initial setting time is too short, reduce 0.5-1 part of activator, reach the standard and transfer to the storage tank for standby (storage time ≤1 h).

[0032] S3: Drilling and pouring (key step of disaster resistance);

[0033] Drilling positioning: Arrange hole positions in the form of plum blossom along the roadbed slope, the transverse spacing is 800-1000 mm and the longitudinal spacing is 1000-1200 mm in the conventional area, and the equilateral triangle arrangement is used to ensure that there is no dead angle; the key is to increase 10%-15% of the hole positions at the slope toe (the most serious area of flood scouring) to form a reinforced disaster resistance zone (the transverse spacing is 700-850 mm and the longitudinal spacing is 900-1050 mm), and the width of the reinforced zone is 1 / 3 of the slope height;

[0034] Drilling operation: Use a spiral drill to drill holes with a diameter of 120-150 mm and a depth of 1.5-2.0 m (ensure that the embedded stable soil layer is ≥0.5 m and the bearing capacity of the stable soil layer is ≥200 kPa through geological radar detection to form a disaster resistance bearing foundation and avoid the overall overturning of the solidified body caused by flood scouring), and the drilling perpendicularity deviation is ≤1%;

[0035] Hole cleaning treatment: Use compressed air (pressure 0.6 MPa) to blow out the soil in the hole until the residual soil thickness at the bottom of the hole is ≤5% of the hole depth to ensure that the solidified body is combined closely with the stable soil layer and the uplift resistance (resisting the upward impact of flood) is improved;

[0036] Layered pouring: Slowly inject the solidified body into the hole through a 50 mm diameter conduit, the layer height is 30-40 cm, and use the self-gravity of the solidified body to naturally flow and fill the soil gaps in the hole wall without vibration (avoid damaging the soil structure integrity and prevent forming a water permeable channel), pour until the surface of the slope is flush, and form a natural transition of the ground surface to reduce the direct scouring of the slope surface by flood.

[0037] S4: Maintenance and detection (disaster resistance performance verification);

[0038] Maintenance stage: Immediately cover the air-permeable and moisture-retaining film (air permeability ≥50%) after pouring, and sprinkle water 1 time at 9:00 and 15:00 every day for the first 3 days (watering amount 0.5 L / m 2 ), keep the surface wet but not waterlogged; when the environmental temperature is lower than 10℃, extend the maintenance to 14 days and cover the heat preservation quilt to ensure that the geopolymer reacts fully.

[0039] The roadbed slope protection composition of the embodiment of the present application is different from the traditional slope protection structure, and the present application realizes disaster resistance in cooperation with the soil through the design of "multi-deformation + gradient transition", and the structural advantages are as follows:

[0040] Multi-deformation scour-resistant structure: the roadbed slope protection composition fills the drill hole and soil pores naturally after pouring, forms a non-regular "multi-deformation structure" (the maximum diameter is 120-150 mm, and the overall length is 1.5-2.0 m), has no rigid interface, can disperse the water flow impact force (adapted to the flood with a flow speed of 1.5-2.5 m / s) when the flood is scoured, avoids the structure fracture caused by local stress concentration, and forms a "whole protection layer" with the soil, has no water flow channel, and can greatly reduce the risk of slope collapse;

[0041] Gradient transition layer anti-permeation: a transition layer with a thickness of 10-20 mm is formed at the contact position of the roadbed slope protection composition and the soil, the density of the layer decreases from the inside to the outside, the core strength is ensured to resist the flood impact, the soil is allowed to normally permeate (the difference in permeability coefficients is less than or equal to 1x10 -8 cm / s), the soil softening caused by accumulated water is avoided, and the requirements of "scour resistance" and "water permeability" are balanced;

[0042] Root system-composition synergistic reinforcement: the 0.1-0.5 mm small pores reserved by the roadbed slope protection composition can allow the plant root system (the penetration depth is greater than or equal to 300 mm) to penetrate and grow, the root system and the solidified body form a "three-dimensional network", and the soil scouring resistance is further enhanced, the soil loss can be reduced when the flood comes, and the slope recovery is faster after the disaster.

[0043] The roadbed slope protection composition of the present application is suitable for the roadbed slope of a highway or a railway, especially for a region where floods frequently occur and slope collapse easily occurs, and can realize the dual functions of roadbed reinforcement and natural disaster prevention and control.

[0044] The performance detection results of the embodiment of the present application are as follows:

[0045] 1. Mechanical properties: the compression testing machine is used to detect that the 28-day compressive strength is greater than or equal to 4.8 MPa, the shear strength is greater than or equal to 1.1 MPa, and the drill core integrity is greater than or equal to 90%, so that the flood impact load can be resisted;

[0046] 2. Disaster resistance: the simulated flood test device is used to detect that the scour loss rate is less than or equal to 5% (the loss rate of the traditional cement-based solidified body is about 12%-15%) when the water flow with a flow speed of 2 m / s scours the surface of the solidified body for 2 hours;

[0047] 3. Ecological performance: the water-resistant herbaceous plants such as dog tooth grass and reed are planted, the root penetration rate is greater than or equal to 80% after 2 weeks, and the difference in permeability coefficients between the solidified body and the soil interface is less than or equal to 1x10 -8 cm / s by using the permeameter;

[0048] 4. Environmental performance: according to HJ / T 299-2007 "Solid waste leaching toxicity leaching method-sulfuric acid and nitric acid method" to detect heavy metal dissolution ≤0.1 mg / L;

[0049] Vegetation restoration: after detection, grass seeds are sown on the surface of the slope to complete ecological restoration and further enhance the surface erosion resistance.

[0050] Application example:

[0051] A flood-prone area highway subgrade slope protection engineering (without cement system)

[0052] 1. Project overview: The highway is located along the tributaries of the middle and lower reaches of the Yangtze River and is prone to be washed by flood during the flood season (the maximum historical flood flow rate is 2.3 m / s). Three slope landslides have occurred. The slope to be reinforced this time has a slope of 1:1.5, a soil type of sandy soil (easy to lose), a slope height of 3 m, and a solidified body dosage of 250 m 3 .

[0053] 2. Solidified body formula (weight parts): fly ash 46 parts, desulfurization gypsum 21 parts, S95 mineral powder 14 parts, pretreated red mud 10 parts, geopolymer activator 8 parts, water 22 parts, and sodium sulfide 1.0 part.

[0054] 3. Construction process: according to the above construction methods S1-S4 steps, a 1 m wide reinforced disaster-resistant belt (hole position is densified by 12%) is arranged at the slope toe, the hole diameter is 130 mm, the hole depth is 1.9 m (embedded in the stable soil layer 0.6 m), and the maintenance is 13 days (environmental temperature 18℃); mixed grass seeds of dog tooth grass and reed are planted in the vegetation restoration stage.

[0055] 4. Test results: 28-day compressive strength 5.2 MPa, shear strength 1.25 MPa, simulated flood scour (flow rate 2 m / s, 2 h) loss rate 4.2%, root penetration rate 88%, heavy metal dissolution 0.06 mg / L, and permeability coefficient difference 7.

[0056] The "multi-deformation whole protection layer" formed by the composition has a scour loss rate of ≤5%, which is reduced by more than 60% compared with traditional slope protection structures; the design of embedding in the stable soil layer (depth ≥0.5 m) increases the pullout resistance of the solidified body by 30%, which can effectively resist the impact of flood with a flow rate of 1.5-2.5 m / s and avoid slope landslides; after the disaster, only vegetation needs to be replanted to quickly restore, and the repair cost is reduced by 70%.

[0057] The cement is removed in the present application, and the carbon emission of each ton of composition is reduced by 0.8-1.0 tons, and the single-kilometer engineering (slope area 1000 m 2)Carbon emissions are reduced by 160-200 tons; solid waste mixing ratio is up to 80%-97%, and single kilometer can consume fly ash 95-120 tons, desulfurization gypsum 40-55 tons, mineral powder 30-40 tons, and red mud 22-32 tons, greatly reducing solid waste storage pollution; at the same time, the structure formed by multiple solid wastes has excellent anti-freeze-thaw and anti-fatigue performance, is suitable for flood-prone and climate-variable areas, and realizes the win-win of "environmental protection + disaster resistance".

[0058] The application has outstanding economy and applicability, saves cement procurement cost, reduces material cost by 15%-20%, does not need vibrating equipment and PVC sleeve, reduces construction process by 30% and construction cost by 25%, prolongs the service life of roadbed by 10-15 years due to the improved disaster resistance, reduces the later maintenance cost by 40%, saves 9-13 thousand yuan per kilometer in comprehensive cost, and is especially suitable for flood-prone highway and railway construction projects.

[0059] Obviously, those skilled in the art can make various modifications and variations to the application without departing from the spirit and scope of the application. Thus, if these modifications and variations of the application belong to the scope of the claims of the application and their equivalent technologies, the application also intends to include these modifications and variations.

Claims

1. A roadbed slope protection composition based on solid waste-geopolymer, characterized in that, By weight, the raw material composition includes: 38-48 parts fly ash, 16-22 parts desulfurized gypsum, 12-16 parts S95 grade mineral powder, 9-13 parts pretreated red mud, 7-9 parts geopolymer activator, 19-23 parts water, and 0.6-1.2 parts sodium sulfide; the pretreated red mud is red mud that has been neutralized with 5%-8% ferrous sulfate for 24 hours and sieved to a particle size ≤5mm; the geopolymer activator is a composite system of sodium silicate and sodium hydroxide, wherein the mass ratio of sodium silicate to sodium hydroxide is 2:1-1.8:

1.

2. The roadbed slope protection composition as described in claim 1, characterized in that, The composition forms a gradient transition layer with a thickness of 10-20 mm after contact with the soil, and retains micropores with a pore size of 0.1-0.5 mm after hardening.

3. A construction method based on the roadbed slope protection composition according to any one of claims 1-2, characterized in that, Includes the following steps: S1: Solid waste pretreatment: Red mud is neutralized by adding ferrous sulfate in proportion and then sieved; desulfurized gypsum is dried to a moisture content of ≤15%; fly ash and mineral powder are sieved through an 80-mesh sieve; S2: Preparation of solidified body: Dry mix fly ash, desulfurized gypsum, mineral powder and pretreated red mud for 2-3 minutes, add geopolymer activator and water and wet mix for 5-8 minutes, test slump and initial setting time, and use it after meeting the standards; S3: Drilling and Grouting: Using a spiral drilling rig, drill holes in a quincunx pattern along the roadbed slope, with a hole diameter of 120-150mm and a hole depth of 1.5-2.0m. After cleaning the holes, grout the roadbed slope protection composition in layers, with each layer being 30-40cm high. The mixture will naturally adhere to the soil under gravity to form an erosion-resistant structure. The quincunx-shaped drilling will be increased by 10%-15% in the slope toe area to form a reinforced disaster-resistant zone, with a lateral spacing of 700-85mm and a longitudinal spacing of 900-1050mm. S4: Maintenance and Inspection: Cover with a breathable and moisturizing membrane for 10-14 days, and test the compressive strength, shear strength, and erosion loss rate after 28 days. After meeting the standards, restore the slope vegetation.

4. The construction method as described in claim 3, characterized in that, In step S3, the horizontal spacing of the boreholes in the conventional area is 800-1000mm, and the vertical spacing is 1000-1200mm. After cleaning the boreholes, the residual slag is ≤5%. After grouting, the roadbed slope protection composition forms a continuous disaster-resistant protective layer with the soil, without the need for vibration and casing.

5. The construction method as described in claim 3 or 4, characterized in that, In step S4, water is sprayed once a day for the first 3 days of curing. During the test, the integrity of the core sample taken from the borehole is ≥90%, the erosion loss rate is ≤5%, and the permeability difference is ≤1×10-8cm / s.

6. The application of the roadbed slope protection composition as described in claims 1-2 in roadbed slope protection engineering.