Residual silty clay polymer solidified soil as well as preparation method and application thereof

Abstract

The invention relates to residual silty clay polymer stabilized soil and a preparation method and application thereof, and belongs to the field of geotechnical engineering and waste resource utilization, the residual silty clay polymer stabilized soil is prepared from the following raw materials by mass: 90%-96.85% of residual silty clay, 0.5%-1.6% of water glass, 0.15%-0.4% of a ladyes path liquid diluent, 1.25%-4% of calcareous lime, and 1.25%-4% of Portland cement, the sum of the mass percentages of the materials is 100%. The invention further provides a preparation method and application of the residual silty clay polymer solidified soil. The method can consume the waste residual silty clay, reduces the cement consumption, has the advantages of low carbon, environmental protection, short construction period, low cost and the like, is suitable for scattered soft soil roadbed treatment, and economically and efficiently improves the overall stability and durability of the roadbed.

Description

Technical Field

[0001] The present invention relates to the fields of geotechnical engineering and waste resource utilization, and particularly relates to a residual silty clay geopolymer solidified soil, a preparation method thereof, and an application thereof. Background Art

[0003] In the southern region, the water system is developed and soft soil is widely distributed. Its main type is residual silty clay, which is brownish red, hard plastic, without shaking reaction, slightly shiny, medium dry strength, medium toughness, easy to soften when soaked in water, and easy to crack when losing water. There are many Fe 3+ ions, and the distribution is uneven. It is often classified as special geotechnical in geological exploration and often needs to be treated.

[0004] When dealing with scattered and thin residual silty clay layers by traditional subgrade treatment methods, such as using soil replacement, it will cause waste of earthwork and long transportation distance; using cement mixing piles, it is necessary to deal with unknown underground conditions, with high cost and a large amount of cement used causing soil and water pollution; using the drainage consolidation method, the treatment period is long and the effect is poor; using dynamic compaction method, it disturbs residents and has a great impact on the environment. Therefore, it is necessary to develop a method that can not only realize the utilization of waste earthwork but also treat scattered residual silty clay. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a residual silty clay geopolymer solidified soil, a preparation method thereof, and an application thereof, which can solve the problems of waste of earthwork, high cost, long period, and environmental pollution existing in traditional subgrade treatment methods. The present invention can directly consume residual silty clay as subgrade soil, and is particularly suitable for the situation where it is widely distributed but the soil layer is not thick.

[0006] The technical solution adopted by the present invention to solve its technical problem is as follows: The residual silty clay geopolymer solidified soil of the present invention is prepared from the following raw materials by mass percentage: 90%-96.85% of residual silty clay, 0.5%-1.6% of water glass, 0.15%-0.4% of roadyes road liquid diluent, 1.25%-4% of calcareous lime, and 1.25%-4% of portland cement. The sum of the mass percentages of each material is 100%.

[0007] Further, the modulus of the water glass is 1.5-3.5.

[0008] Further, the roadyes road liquid diluent is a diluent obtained by adding water to roadyes road liquid according to a mass ratio of 1:100. The roadyes road liquid used is a water-resistant and strong-base environmental protection material introduced from abroad and produced by Jiangsu Road Industry Construction Co., Ltd.

[0009] Further, the effective CaO content in the calcareous lime is ≥45wt%.

[0010] Further, the portland cement preferably uses ordinary portland cement or slag portland cement, and other types can also be used, but rapid hardening and rapid strength cement cannot be used.

[0011] The preparation method of the residual silty clay geopolymer solidified soil of the present invention includes the following steps: (1) Select 3 representative points on-site to take a small amount of soil and mix it evenly. After removing the sundries, repeatedly crush and screen the soil blocks until they meet the design particle size requirements; conduct an orthogonal test to compare the 7-day unconfined compressive strength of specimens with different admixture dosages. The determination of the 7-day unconfined compressive strength should be carried out according to the "Test Regulations for Inorganic Binding Material Stabilized Materials in Highway Engineering" JTGE51. Considering the test results and economy comprehensively, determine the admixture dosage. The mass percentages of each raw material are as follows: residual silty clay 90%-96.85%, water glass 0.5%-1.6%, roadyes road liquid diluent 0.15%-0.4%, calcareous lime 1.25%-4%, portland cement 1.25%-4%. The sum of the mass percentages of each material is 100%; Prepare the soil sample according to the above ratio. After covering it with plastic film and standing for 4-6 hours, determine its maximum dry density and optimal moisture content through the compaction test in the "Test Regulations for Inorganic Binding Material Stabilized Materials in Highway Engineering" JTG E51. Taking this moisture content as the standard, control it within ±2% fluctuation in the subsequent processes; (2) After clearing the surface of the site, sun-dry the soil mass and measure the moisture content of the soil mass in real time. Stop sun-drying when the moisture content reaches the optimal moisture content ±2%. If there is abundant water resources on-site, take measures such as drainage ditch diversion, cofferdam pumping or well point dewatering; (3) Repeatedly crush and screen the soil blocks until the soil blocks meet the design particle size requirements; mix the soil mass with calcareous lime and portland cement evenly according to the ratio described in step (1); then, mix water glass and roadyes road liquid diluent according to the ratio described in step (1) and add them to the soil mass, and use a mixer to stir and mix; (4) Cover with plastic cloth and let the soil stand for 4-6 hours, measure the moisture content in real time, ensure that the moisture content of the soil mass during the standing process is within the range of the optimal moisture content ±2%, keep the soil temperature, and make the moisture in the soil mass fully participate in the reaction.

[0012] Its technical principle is: The addition of water glass, calcareous lime, and portland cement makes the soil mass enter an alkaline environment. At the same time, adding roadyes road liquid diluent stimulates the soil mass, causing the silicate in the soil mass to depolymerize, destroying the clay mineral structure, promoting the breakage of the Al-O-Si bond, and releasing active silicon-aluminum components Al 3+ and SiO4 4- , and OH -A series of ion exchanges and chemical bond reorganizations occur, gradually forming products of NaAl(OH)4 and Na2SiO3. Further, the products dissolve and undergo a polymerization reaction. The monomers in the sol are connected through dehydroxylation reactions (-OH condensation) to form a network skeleton of "-Si-O-Al-O-Si-", and finally, an amorphous N-A-S-H geopolymer gel is formed through the reaction, gradually densifying as the reaction progresses. The gel structure generated during the reaction fills the pores of the soil mass, displaces water and air, enhances the structural density, cements the soil particles, and forms a rigid skeleton. Moreover, portland cement and calcareous lime themselves can be used as admixtures, and the C-S-H gel and N-A-S-H geopolymer gel are intertwined with each other to further fix the soil mass.

[0013] The application of the residual silty clay geopolymer solidified soil of the present invention in subgrade construction can, while consuming residual silty clay, ensure the overall strength and stability of the subgrade and extend the service life of the subgrade. Specifically, it includes the following steps: (1) Layered filling: The obtained solidified soil is paved in layers, and initially compacted by a single-wheel roller and finally compacted by a rubber-tyred roller. (2) Curing: After compaction, a curing solution is sprayed on the surface of the subgrade and covered with non-woven fabric, and cured for 7 - 10 days, during which traffic is closed.

[0014] Further, during the layered filling in step (1), clay layers with a plasticity index of 10 - 17 are simultaneously filled on both sides of the subgrade, with a thickness ≥ 1 m, for restricting lateral deformation.

[0015] Further, during the layered filling in step (1), as the clay has difficulty in draining water, a road arch is made, and the cross slope is set at 2% - 4% for facilitating drainage. When necessary, auxiliary drainage measures are taken.

[0016] Its technical principle is as follows: After crushing and screening the original residual silty clay, calcareous lime, portland cement, and water glass are added to the base soil to create an alkaline environment, increasing the calcium and silicon components in the soil mass. At the same time, a roadyes road liquid diluent is added to stimulate the soil mass, and a depolymerization reaction occurs to release active silica and alumina components. Subsequently, the soil mass is covered with a plastic sheet for stewing. During the process, a geopolymerization reaction occurs to generate a low-polymer gel mainly composed of ionic bonds and covalent bonds, filling the pores of the soil mass, reducing the friction between soil particles, and facilitating compaction. After the solidified soil is filled in layers, the gel material undergoes drainage and curing, further consuming the water in the soil mass during the polycondensation hardening process, reducing the thickness of the water film layer, and forming high-polymer N-A-S-H and C-S-H gels. These gels are intertwined with each other to form a stable three-dimensional network structure, effectively locking the soil particles and enhancing the overall strength and stability of the subgrade.

[0017] Compared with the prior art, the beneficial effects of the present invention are: (1)Resource utilization of solid waste: By using waste residual silty clay as subgrade material, earthwork waste is significantly reduced and carbon emissions are lowered.

[0018] (2)Improving subgrade bearing capacity through chemical curing: The N-A-S-H gel and C-S-H gel formed by the geopolymer reaction interweave to form a three-dimensional network structure, filling pores and cementing soil particles, significantly improving strength and impermeability, and reducing the risks of acid rain erosion and freeze-thaw damage.

[0019] (3)Controllable quality throughout the process: Guided by indoor experiments and produced through an industrialized process, key parameters (water content, admixture dosage, compaction degree) are controlled manually throughout the process to ensure controllable subgrade quality.

[0020] (4)Improving subgrade deformation and crack resistance: Through the constraint of clay edging, cracks and lateral deformation during construction are reduced. Description of the Drawings

[0021] Figure 1 It is a three-dimensional structure microscopic schematic diagram of an embodiment of the present invention; Figure 2 It is a subgrade structure maintenance profile schematic diagram of an embodiment of the present invention; Explanation of the reference numerals in the drawings: 1, soil particles; 2, pores; 3, geopolymer gel; 4, reaction product precipitate; 5, subgrade; 6, non-woven fabric; 7, clay edging; 8, curing liquid. Detailed Embodiments

[0022] The technical solutions of the present invention will be clearly and completely described below in conjunction with the drawings and embodiments.

[0023] The roadyes road liquid dilution used in the embodiment is a dilution of roadyes road liquid with water in a mass ratio of 1:100. The roadyes road liquid used is a water-resistant strong base environmental protection material introduced from abroad and produced by Jiangsu Road Industry Construction Co., Ltd., and the model is selected as R600.

[0024] Example 1 This embodiment provides a residual silty clay geopolymer solidified soil, which is prepared from the following raw materials by mass percentage: residual silty clay 93.75%, water glass 1%, roadyes road liquid dilution 0.25%, calcareous lime 2.5%, portland cement 2.5%.

[0025] The residual silty clay is taken from the Songya Lake area in Changsha, Hunan. It is brownish-red, with relatively high Fe 3+ It is hard plastic, without shaking reaction, with a slightly shiny reaction, medium dry strength, medium toughness, weathered and residual from the underlying argillaceous siltstone, easy to soften when soaked in water, easy to crack when losing water, and unevenly distributed. Its main physical and mechanical property indexes are shown in Table 1.

[0026] Statistics of Main Physical and Mechanical Property Indexes of Residual Silty Clay in Table 1

[0027] The modulus of water glass is 2. The effective CaO content in calcareous lime is ≥45 wt%, the residue on the 0.2 mm sieve of calcareous lime is less than or equal to 2%, and the residue on the 90 μm sieve is less than or equal to 7%. Portland cement with a strength grade of 42.5 is selected as the Portland cement.

[0028] Its main reaction process is as follows: The addition of water glass, calcareous lime, and Portland cement makes the soil enter an alkaline environment, causing the silicate in the soil to depolymerize, promoting the breakage of the Al-O-Si bond, and releasing active silicon-aluminum components Al 3+ and SiO4 4- , gradually forming the products NaAl(OH)4 and Na2SiO3. Further, the products dissolve and undergo a polymerization reaction, and finally react to form amorphous N-A-S-H geopolymer gel 3, which gradually densifies as the reaction proceeds.

[0029] The geopolymer gel 3 generated in the reaction fills the soil pores 2, squeezes out water and air, enhances the structural density, cements the soil particles 1, and forms a skeleton. A series of complex reactions occur between the gel in the geopolymer and other components in the soil after the reaction, and then extremely insoluble salts such as CaSiO3 are produced, forming reaction product precipitates 4, as Figure 1 shown.

[0030] Its preparation method includes the following steps: (1) Select 3 representative points on-site, take a small amount of soil and mix it evenly. After removing the sundries, repeatedly crush and screen the soil blocks until all the soil blocks are less than 40 mm; conduct an orthogonal test, compare the 7-day unconfined compressive strength of specimens with different admixture dosages. The determination of the 7-day unconfined compressive strength should be carried out according to the "Test Regulations for Inorganic Binding Material Stabilized Materials in Highway Engineering" JTGE51. Considering the test results and economy comprehensively, determine the admixture dosage. The mass percentages of each raw material are: residual silty clay 93.75%, water glass 1%, roadyes road liquid diluent 0.25%, calcareous lime 2.5%, and Portland cement 2.5%; Prepare the solidified soil according to the above ratio. After covering it with a plastic film and standing for 4 h, determine the maximum dry density of the solidified soil as 1.74 g / cm 3 through the compaction test in the "Test Regulations for Inorganic Binding Material Stabilized Materials in Highway Engineering" JTG E51, and the optimum moisture content is 20.3%. Taking this moisture content as the standard, control it within ±2% fluctuation in the subsequent process; (2)Refer to the geological exploration report and confirm on-site that the distribution range of the in-situ residual silty clay is from section K0+575 - K0+675, K0+750 - K0+825, K1+000 - K1+100, K1+200 - K1+300, K1+325 - K1+400 of Songsan Road; from section K0+500 - K0+775 of Songqi Road; from section K0+360 - K0+400, K0+420 - K0+460, K0+490 - K0+600, K0+660 - K0+700, K1+660 - K1+700 of Yayi Road; from section K0+825 - K0+916 of Yasan Road, with an average depth of 0.95m; considering the comprehensive solidification section, the surrounding earthwork location and traffic, set up a solidification plant at K0+700 of Yasan Road, test equipment, and planned production capacity; according to the on-site situation, conduct surface cleaning, remove sundries such as tree roots, turf, and rocky debris from the soil, then sun-dry the earthwork, and test the moisture content by the alcohol combustion method in the "Code for Highway Geotechnical Tests" JTG3430. Stop sun-drying the soil when the moisture content reaches 20.3% ± 2%. (3)Excavate the soil layer, use a crawler crusher to repeatedly crush and screen the soil clods until all soil clods are less than 40mm; unload the soil into a prefabricated soil pit; add calcareous lime and portland cement according to the ratio described in step (1), and use an excavator to mix evenly until the surface of the mixed soil shows a grayish-white color; dilute the roadyes road liquid by adding water and stirring at a mass ratio of 1:100, and uniformly store it in the road liquid storage bin; mix the water glass with the diluted roadyes road liquid according to the ratio described in step (1) and add it to the soil, and use a mixer to conduct secondary mixing of the soil and the admixture to ensure uniform distribution of the admixture; in an alkaline environment, geopolymers begin to form in the improved soil. (4)Avoid the rainy season and the period of moisture return for soil curing; stack the improved soil on the curing site, cover it with plastic sheeting, and let it stand for 4h. Measure the moisture content in real time to ensure that the moisture content of the soil during the curing process is within the range of the optimal moisture content ± 2%, and maintain the soil temperature to enable the water in the soil to fully participate in the reaction.

[0031] On this basis, a construction method for a residual silty clay geopolymer solidified soil subgrade is provided, including the following steps: (1) Use the obtained solidified soil as the replacement fill material and construct the roadbed 5 by layered filling using the traditional replacement filling method. The construction scope is widened by 500 mm on each side of the road for filling. Use the pre-soaked soil for layered filling, and the loose thickness of a single-layer soil layer shall not exceed 300 mm (about 200 mm after compaction). After being leveled by a bulldozer, first compact it with a single-wheel roller "slow first and then fast" (speed: 1.5 km / h - 1.7 km / h), and then use a rubber-tired roller for surface leveling (speed: 2.0 km / h - 2.5 km / h). At the same time, fill the clay side slopes 7 with a plastic index of 10 - 17 on both sides synchronously; since the clay has difficulty in draining water, make a road arch with a transverse slope of 4%; each operation unit needs to be completed within the setting time of the mixture. (2) After the roadbed is compacted and formed, dilute the roadyes road liquid according to a mass ratio of 1:1000 as the curing liquid 8 to moisten the surface layer, and cover it with non-woven fabric 6 for curing. As Figure 2 shown, cure for 7 days according to the average temperature during the construction period, close the traffic during this period, and control vehicle passage; the geopolymer gel 3 in the roadbed gradually takes shape, occupies its own position in the pores between soil particles, displaces the original water or air in the pores 2, and forms a three-dimensional network structure, improving the bearing capacity of the soil mass.

[0032] The lowest value of the compactness detected by the field sand replacement method is 95.4%, and the average compactness value is 96.5%, meeting the design standard of 95% compactness.

[0033] Economic Benefits When treating residual eluvial silty clay with a treatment area of 5 hm 2 and an average thickness of 1 m, by comparing the direct costs of this solution (already including the factory construction cost), replacing with transported soil (hauling distance: 20 km), and cement mixing pile reinforcement (pile length: 5 m, pile diameter: 0.7 m, pile spacing: 1.5 m), the economy of this solution in treating shallow residual eluvial silty clay can be shown. The comparison of the construction cost and the relative cost based on this solution is shown in Table 3.

[0034] Table 3 Comparison of Construction Costs of 3 Solutions and Their Relative Costs to This Solution

[0035] The solidification method of the present invention has a clear principle, excellent proportioning, convenient and fast construction. It not only realizes the reuse of waste residual eluvial silty clay, but also economically and efficiently improves the bearing capacity and durability of the roadbed.

[0036] Example 2 This example provides a residual eluvial silty clay geopolymer solidified soil, which is prepared from the following raw materials by mass percentage: residual eluvial silty clay 96.85%, water glass 0.5%, diluted roadyes road liquid 0.15%, calcareous lime 1.25%, portland cement 1.25%.

[0037] The preparation method and application are the same as those in Example 1.

[0038] Example 3 This example provides a residual silty clay geopolymer solidified soil, which is prepared from the following raw materials by mass percentage: 90% of residual silty clay, 1.6% of water glass; 0.4% of roadyes road liquid diluent; 4% of calcareous lime; 4% of portland cement.

[0039] The preparation method and application are the same as those in Example 1.

[0040] Although the preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present invention, those skilled in the art can also make many forms without departing from the purpose of the present invention and the scope protected by the claims. All of these fall within the protection scope of the present invention.

Claims

1. A residual silty clay geopolymer solidified soil, characterized in that: It is prepared from raw materials with the following mass percentages: residual silty clay 90% - 96.85%, sodium silicate 0.5% - 1.6%, roadyes road liquid diluent 0.15% - 0.4%, calcareous lime 1.25% - 4%, portland cement 1.25% - 4%. The sum of the mass percentages of all materials is 100%.

2. The residual silty clay geopolymer solidified soil according to claim 1, wherein: The modulus of the sodium silicate is 1.5 - 3.

5.

3. The residual silty clay geopolymer solidified soil according to claim 1 or 2, characterized in that: The roadyes road liquid diluent is a diluent obtained by adding water to roadyes road liquid at a mass ratio of 1:

100. The roadyes road liquid used is a water-resistant and strong-base environmental protection material introduced from abroad and produced by Jiangsu Road Industry Construction Co., Ltd. as an agent.

4. The residual silty clay geopolymer solidified soil according to claim 1 or 2, characterized in that: The effective CaO content in the calcareous lime is ≥ 45wt%.

5. The residual silty clay geopolymer solidified soil according to claim 1 or 2, characterized in that: Ordinary portland cement or slag portland cement is used as the portland cement.

6. The preparation method of the residual silty clay geopolymer solidified soil according to claim 1, characterized in that, It includes the following steps: (1) Select 3 representative points on-site to take a small amount of soil and mix it evenly. After removing the sundries, repeatedly crush and screen the soil blocks until they meet the design particle size requirements; conduct an orthogonal test to compare the 7-day unconfined compressive strength of specimens with different admixture dosages. The determination of the 7-day unconfined compressive strength should be carried out in accordance with the "Test Regulations for Inorganic Binding Material Stabilized Materials in Highway Engineering" JTG E51. Considering the test results and economy comprehensively, determine the admixture dosage. The mass percentages of each raw material are: residual silty clay 90% - 96.85%, sodium silicate 0.5% - 1.6%, roadyes road liquid diluent 0.15% - 0.4%, calcareous lime 1.25% - 4%, portland cement 1.25% - 4%. The sum of the mass percentages of all materials is 100%; Prepare the soil sample according to the above ratio, cover it with plastic film and let it stand for 4 - 6h. Then, determine its maximum dry density and optimum moisture content through the compaction test in the "Test Regulations for Inorganic Binding Material Stabilized Materials in Highway Engineering" JTG E51. Taking this moisture content as the standard, control it within ±2% fluctuation in the subsequent processes; (2) After clearing the surface of the site, sun-dry the soil mass and measure the moisture content of the soil mass in real time. Stop sun-drying when the moisture content reaches the optimum moisture content ±2%. If there is abundant water resources on-site, take measures such as drainage ditch diversion, cofferdam pumping or well point dewatering; (3) Repeatedly crush and screen the soil blocks until the soil blocks meet the design particle size requirements; mix the soil mass evenly with calcareous lime and portland cement according to the ratio described in step (1); then, mix sodium silicate and roadyes road liquid diluent according to the ratio described in step (1) and add them to the soil mass, and use a mixer to stir and mix; (4) Cover with plastic cloth and let the soil stand for 4 - 6h, measure the moisture content in real time, ensure that the moisture content of the soil mass during the standing process is within the range of the optimum moisture content ±2%, keep the soil temperature, and make the moisture in the soil mass fully participate in the reaction.

7. Application of the residual silty clay geopolymer solidified soil as described in claim 1 in subgrade construction.

8. The application of the residual silty clay geopolymer solidified soil according to claim 7 in subgrade construction, characterized in that, Specifically, it includes the following steps: (1) Layered filling: Spread the obtained solidified soil in layers, and use a single-wheel roller for primary compaction and a rubber-tyred roller for final compaction; (2) Maintenance: Sprinkle a maintenance liquid on the surface of the compacted subgrade and cover it with non-woven fabric, and maintain it for 7 - 10 days. During this period, traffic is closed.

9. The application of the residual silty clay geopolymer solidified soil according to claim 8 in subgrade construction, characterized in that: During the layered filling in step (5), a clay edging layer with a plastic index of 10 - 17 is filled simultaneously on both sides of the subgrade, with a thickness of ≥1 m, which is used to limit lateral deformation.

10. Application of residual silty clay geopolymer solidified soil according to claim 8 in subgrade construction, characterized in that: During the layered filling in step (5), it is inconvenient to drain the clay. A road crown is made in the middle, and the cross slope is set at 2% - 4% for easy drainage. Auxiliary drainage measures are taken if necessary.

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