Modified geopolymer cementing material preparation and soft soil reinforcement construction method

Abstract

The invention discloses a modified geopolymer cementing material preparation and soft soil reinforcement construction method. The modified geopolymer cementing material comprises the following raw materials in parts by weight: 65-75 parts of a polymer grouting material, 15-25 parts of F-type fly ash, 0.5-3 parts of an alkali activator and 5-15 parts of a fiber-based geopolymer. Wherein the polymer grouting material comprises industrial waste residues and mineral active components, the alkaline activator is a dry powder mixture material of CaO and Na2SiO3, and the fiber-based geopolymer is one of a basalt fiber geopolymer, a carbon fiber geopolymer and an aluminum / carbon fiber reinforced polymer; along with the increase of the mass fraction of the alkaline activator, the prolonging of the curing period and the reduction of the water-solid ratio, the compressive strength of the geopolymer cementing material is remarkably improved, and compared with an unmodified material, the modified geopolymer shows higher toughness and ductility when being pressed, and particularly has a more obvious improvement effect on the flexural strength.

Description

Technical Field

[0001] The invention relates to the technical field of soft soil foundation treatment, and in particular to a preparation method of a modified geopolymer gelling material and a soft soil reinforcement construction method. Background Art

[0002] Soft soils are clayey soils with high natural water content, high compressibility, low shear strength, and a soft-plastic to fluid-plastic state. They are primarily composed of fine-grained sediments such as silt and silty soils. These sediments, primarily formed in environments with stagnant or slow-flowing water, include silt, silty soils, peat, and peaty soils. Their natural water content approaches or exceeds the liquid limit, and their void ratio is often greater than one, resulting in high compressibility and low bearing capacity.

[0003] Soft soil reinforcement treatments are categorized into surface treatment and deep treatment. The former generally involves soil layers within 3 to 5 meters of the surface. Commonly used measures include excavation, soil replacement, cushioning, silt removal, compaction, compaction piles, root piles, drainage consolidation, and the addition of cementitious materials. Deep soft soil reinforcement methods primarily include drainage consolidation, compaction sand piles, dynamic tamping, vibration impaction, high-pressure jet grouting, deep mixing, and grouting. The first four methods primarily densify the soil, while the last three involve adding cementitious materials to the soil in various ways to solidify it. Other methods include freezing, heat treatment, electroosmosis drainage, and electrochemical reinforcement, which can be used under special conditions.

[0004] Geopolymers, a recycled polymer cementitious material, are widely used in the construction industry. Their advantages include rapid curing and efficient reinforcement, lightweight and environmentally friendly properties, impermeability and corrosion resistance, and precise construction control. Geopolymers are composed of a wide variety of materials, typically including industrial waste residue, fly ash, slag, lime, and other materials. Geopolymers are prepared using an alkaline activation process in an alkaline environment, resulting in a complex three-dimensional network structure. In many projects, replacing cement with geopolymers improves the material's physical and mechanical properties, high-temperature resistance, and shrinkage resistance. Furthermore, compared to conventional materials, they offer greater durability and corrosion resistance. This low-cost geopolymer material boasts low energy consumption and high performance during production, and holds great promise for future development.

[0005] Therefore, it is necessary to provide a method for preparing a modified geopolymer cementitious material and a soft soil reinforcement construction method. Summary of the Invention

[0006] In response to the problems existing in the above-mentioned prior art, the present invention provides a method for preparing a modified geopolymer cementitious material and for soft soil reinforcement construction. The purpose is to achieve a significant improvement in the compressive strength of the alkaline activator-fly ash cementitious material as the mass fraction of the dry powder mixture of CaO and Na2SiO3 increases, the curing age is extended, and the water-solid ratio is reduced; the modified geopolymer exhibits higher toughness and ductility when under pressure, especially a more obvious effect on improving the flexural strength.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions: a modified geopolymer gelling material is prepared, the modified geopolymer gelling material comprising the following raw materials in parts by weight: 65-75 parts of polymer grouting material, 15-25 parts of Class F fly ash, 0.5-3 parts of alkaline activator, and 5-15 parts of fiber-based geopolymer; wherein the polymer grouting material comprises industrial waste residue and mineral active ingredients, the alkaline activator is a dry powder mixture of CaO and Na2SiO3, and the fiber-based geopolymer is one of basalt fiber geopolymer, carbon fiber geopolymer, and aluminum / carbon fiber reinforced polymer; The preparation method of modified geopolymer gelling material is: Step 1: The polymer grouting materials are selected and screened for use, and the large-particle-size polymer grouting materials are screened out and discarded to reduce the increase in pores in the preparation of the geopolymer slurry and reduce the bubbles inside the slurry; Step 2: Put the polymer grouting material and alkaline activator dry material into the mixer in a certain proportion, mix them evenly, and then add all the water according to the water-solid ratio; after mixing evenly, the geopolymer slurry is successfully prepared; Step 3: Pour the prepared slurry into the prepared cylindrical mold. When pouring, pay attention to filling and vibrating at the same time to minimize the presence of bubbles inside the slurry. The number of cylindrical molds should be no less than three to perform pressure tests at different specified ages. Step 4: Place the mold filled with geopolymer slurry in a FY-YS constant temperature curing box and cure it at 25°C until initial setting. After demoulding, seal it with plastic wrap and continue curing until the specified age. Step 5: Clay from a specific project was dried in a CWH-9140A electric blast drying oven at 105°C. The dried clay was crushed, and the large particles were sieved out and discarded. Remolded soft soil with a moisture content of 50% was then prepared for testing. Step 6: Mix the geopolymer slurry prepared in steps 1 to 4 with the reshaped soft soil for 4-6 minutes, and pour it into a mold coated with vaseline in advance in three batches. Each time, compact it more than 10 times with an IHMJ-Ш compactor to vibrate and smooth the mixture. Step 7: Seal the upper and lower surfaces of the soil sample with plastic wrap and place it in a constant temperature curing box for curing. The preparation process takes 35-55 minutes. The curing temperature and humidity are 21°C and 95% respectively. After curing for 24 hours, remove the sample from the mold, number it, and continue curing until the specified age. Step 8: The geopolymer slurry and reshaped soft soil are mixed and stirred and solidified into different curing periods of 3d, 7d, and 21d; the soft soil solidified in different periods is subjected to unconfined compressive strength test and shear strength test.

[0008] Preferably, the polymer grouting material comprises 65 parts, Class F fly ash comprises 23 parts, an alkaline activator comprises 2 parts, and a fiber-based geopolymer comprises 10 parts.

[0009] Preferably, the polymer grouting material comprises 70 parts, Class F fly ash 20 parts, alkaline activator 3 parts, and fiber-based geopolymer 7 parts.

[0010] Preferably, the fiber-based geopolymer is a carbon fiber geopolymer.

[0011] A soft soil reinforcement construction method, based on a modified geopolymer cementitious material according to claims 1 to 4, the soft soil reinforcement construction method is: Step Ⅰ: Select the construction equipment: powerful mixing head, matching excavator, intelligent proportioning workbench, powder silo; Step II: The modified geopolymer cementitious material is stored in a powder silo and a soft soil reinforcement slurry is prepared through an intelligent proportioning workbench. Before the material is fed and mixed, the material needs to be screened at least twice to reduce impurities and large particles in the material. Step III: Install the slurry using a high-pressure pump, matching excavator, and powerful mixing head. During the delivery process, a slurry control pressure gauge is required to monitor the slurry delivery pressure in the soft soil in-situ solidification system and stabilize the soft soil consolidation treatment. Step IV: Testing the compressive strength and shear strength of the cured product.

[0012] In summary, the present invention provides a method for preparing a modified geopolymer cementitious material and for soft soil reinforcement construction. The beneficial effects achieved by the present invention are: The compressive strength of geopolymer cementitious materials is strongly affected by factors such as the mass fraction of alkaline activator (dry powder mixture of CaO and Na2SiO3), curing age and water-solid ratio. With the increase of the mass fraction of alkaline activator, the extension of curing age and the decrease of water-solid ratio, the compressive strength of geopolymer cementitious materials increases significantly.

[0013] Comparing the tensile and shear strengths of different geopolymer slurry systems revealed that carbon fibers, combined with geopolymers to form a high-strength inorganic skeleton structure, significantly improve the compressive strength and elastic modulus of soft soil. The addition of carbon fibers effectively inhibits crack propagation, delaying or preventing crack formation and propagation through the synergistic effect of the fibers and the matrix. Compared to unmodified materials, the modified geopolymer exhibits greater toughness and ductility under compression, with a particularly significant improvement in flexural strength (approximately a two-fold increase).

[0014] The dry powder mixture of CaO and Na2SiO3 - the product of alkali-activated binder in an alkaline environment fills the pores between soil particles, making the soil system more compact; the addition of carbon fiber further enhances the integrity of the system and slows down the growth of system damage and deformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the preparation process of the modified geopolymer gelling material of the present invention; Figure 2 Schematic diagram of the relationship between water-solid ratio and compressive strength of the present invention; Figure 3 Schematic diagram of the compressive strength change of the polymer grouting material of the present invention; DETAILED DESCRIPTION

[0016] The present invention will be further described below with reference to the accompanying drawings.

[0017] like Figures 1 to 3 As shown: A modified geopolymer cementitious material is prepared using the following equipment: a laboratory planetary mixer, an FYL-YS constant temperature curing chamber, a GWH-9140A electric forced air drying oven, an LHMJI compactor, and a YYW-I strain-controlled unconfined compression tester. The modified geopolymer cementitious material comprises the following raw materials in parts by weight: 65 parts polymer grouting material, 23 parts Class F fly ash, 2 parts alkaline activator, and 10 parts fiber-based geopolymer. The polymer grouting material comprises industrial waste residue and mineral active ingredients; the alkaline activator is a dry powder mixture of CaO and Na₂SiO₃; and the fiber-based geopolymer is selected from the group consisting of basalt fiber geopolymer, carbon fiber geopolymer, and aluminum / carbon fiber reinforced polymer. The modified geopolymer cementitious material is prepared as follows: polymer grouting materials are selected and screened for standby use, and large-particle-size polymer grouting materials are screened out and discarded to reduce the increase in pores in the geopolymer slurry preparation and reduce bubbles in the slurry; the polymer grouting materials and alkaline activator dry materials are placed in a blender in a certain proportion, mixed evenly, and then all water is added according to the water-solid ratio; after mixing evenly, the geopolymer slurry is successfully prepared; the prepared slurry is poured into a prepared cylindrical mold, and attention is paid to vibrating while pouring to minimize the presence of bubbles in the slurry, wherein the number of cylindrical molds is not less than three, so as to conduct pressure tests at different specified ages; The mold filled with geopolymer slurry was placed in an FY-YS constant temperature curing chamber and cured at 25°C until initial setting. After demolding, the mold was sealed with plastic wrap and continued to cure until the specified age. Clay from a certain project was dried in a CWH-9140A electric heated blast drying oven at 105°C. The dried clay was crushed, and the large particles were screened out and discarded. Remolded soft soil with a moisture content of 50% was then prepared for testing. According to the above preparation, the geopolymer slurry and the reshaped soft soil are mixed and stirred for 4-6 minutes, and poured into a mold coated with vaseline in advance in three times. Each time the mixture is poured, it needs to be compacted more than 10 times under the action of the IHMJ-Ш type compactor to vibrate and flatten the mixture; the upper and lower surfaces of the soil sample are sealed with plastic wrap and placed in a constant temperature curing box for curing. The preparation process is 35-55 minutes, and the curing temperature and humidity are 21°C and 95% respectively. After curing for 24 hours, the sample is demoulded and numbered, and the curing is continued to the specified age; the geopolymer slurry and the reshaped soft soil are mixed and stirred and condensed into different curing periods of 3d, 7d, and 21d; the soft soil condensed at different periods is subjected to unconfined compressive strength test and shear strength test.

[0018] Preferably, the polymer grouting material comprises 70 parts, Class F fly ash 20 parts, an alkaline activator 3 parts, and a fiber-based geopolymer 7 parts; wherein the polymer grouting material comprises industrial waste residue and mineral active ingredients, the alkaline activator is a dry powder mixture of CaO and Na2SiO3, and the fiber-based geopolymer is one of basalt fiber geopolymer, carbon fiber geopolymer, and aluminum / carbon fiber reinforced polymer.

[0019] Specifically: Figure 2 and Figure 3As shown in the figure, the optimal preparation conditions of geopolymer are: the optimal ratio of polymer grouting material to fly ash is 3:1, and the water-solid ratio is preferably 0.4. At this time, the 21-day compressive strength of the geopolymer sample is 2.26 MPa. When the mass fraction of the alkaline activator is fixed, the compressive strength of the alkaline activator-fly ash cementitious material sample is distributed between 0.18 and 1.82 MPa at a curing age of 3 days and the water-solid ratio is 0.6, and increases with the curing age. At a curing age of 7 days, when the water-solid ratio is reduced to 0.5, the compressive strength of the alkaline activator-fly ash cementitious material sample is distributed between 1.33 and 3.57 MPa. MPa, at the 21-day curing age, when the water-solid ratio decreased to 0.4, the compressive strength of the alkaline activator-fly ash cementitious material sample increased sharply to 2.26 MPa, which was much greater than the compressive strength of the sample at the 3-day curing age of 1.82 MPa when the water-solid ratio was 0.7. It can be concluded that the strength of the alkaline activator-fly ash cementitious material is significantly affected by the water-solid ratio, and a low water-solid ratio corresponds to a higher compressive strength.

[0020] Preferably, the fiber-based geopolymer is a carbon fiber geopolymer.

[0021] A soft soil reinforcement construction method, based on a modified geopolymer cementitious material according to claims 1 to 4, the soft soil reinforcement construction method is: Step Ⅰ: Select the construction equipment: powerful mixing head, matching excavator, intelligent proportioning workbench, powder silo; Step II: The modified geopolymer cementitious material is stored in a powder silo and a soft soil reinforcement slurry is prepared through an intelligent proportioning workbench. Before the material is fed and mixed, the material needs to be screened at least twice to reduce impurities and large particles in the material. Step III: Install the slurry using a high-pressure pump, matching excavator, and powerful mixing head. During the delivery process, a slurry control pressure gauge is required to monitor the slurry delivery pressure in the soft soil in-situ solidification system and stabilize the soft soil consolidation treatment. Step IV: Testing the compressive strength and shear strength of the cured product.

[0022] The embodiments of the present invention are only used to illustrate the present invention and do not limit the scope of the claims. Other substantially equivalent alternatives that can be thought of by those skilled in the art are all within the scope of protection of the present invention.

Claims

1. A modified geopolymer gelling material preparation, characterized in that: The modified geopolymer cementitious material comprises the following raw materials in parts by weight: 65-75 parts of polymer grouting material, 15-25 parts of Class F fly ash, 0.5-3 parts of alkaline activator, and 5-15 parts of fiber-based geopolymer; wherein the polymer grouting material comprises industrial waste residue and mineral active ingredients, the alkaline activator is a dry powder mixture of CaO and Na2SiO3, and the fiber-based geopolymer is one of basalt fiber geopolymer, carbon fiber geopolymer, and aluminum / carbon fiber reinforced polymer. The preparation method of modified geopolymer gelling material is: Step 1: The polymer grouting materials are selected and screened for use, and the large-particle-size polymer grouting materials are screened out and discarded to reduce the increase in pores in the preparation of the geopolymer slurry and reduce the bubbles inside the slurry; Step 2: Put the polymer grouting material and alkaline activator dry material into the mixer in a certain proportion, mix them evenly, and then add all the water according to the water-solid ratio; after mixing evenly, the geopolymer slurry is successfully prepared; Step 3: Pour the prepared slurry into the prepared cylindrical mold. When pouring, pay attention to filling and vibrating at the same time to minimize the presence of bubbles inside the slurry. The number of cylindrical molds should be no less than three to perform pressure tests at different specified ages. Step 4: Place the mold filled with geopolymer slurry in a FY-YS constant temperature curing box and cure it at 25°C until initial setting. After demoulding, seal it with plastic wrap and continue curing until the specified age. Step 5: Clay from a specific project was dried in a CWH-9140A electric blast drying oven at 105°C. The dried clay was crushed, and the large particles were sieved out and discarded. Remolded soft soil with a moisture content of 50% was then prepared for testing. Step 6: Mix the geopolymer slurry prepared in steps 1 to 4 with the reshaped soft soil for 4-6 minutes, and pour it into a mold coated with vaseline in advance in three batches. Each time, compact it more than 10 times with an IHMJ-Ш compactor to vibrate and smooth the mixture. Step 7: Seal the upper and lower surfaces of the soil sample with plastic wrap and place it in a constant temperature curing box for curing. The preparation process takes 35-55 minutes. The curing temperature and humidity are 21°C and 95% respectively. After curing for 24 hours, remove the sample from the mold, number it, and continue curing until the specified age. Step 8: The geopolymer slurry and reshaped soft soil are mixed and stirred and solidified into different curing periods of 3d, 7d, and 21d; the soft soil solidified in different periods is subjected to unconfined compressive strength test and shear strength test.

2. The preparation method of a modified geopolymer gelling material according to claim 1, characterized in that: 65 parts of polymer grouting material, 23 parts of Class F fly ash, 2 parts of alkaline activator, and 10 parts of fiber-based geopolymer.

3. The preparation method of a modified geopolymer gelling material according to claim 1, characterized in that: 70 parts of polymer grouting material, 20 parts of Class F fly ash, 3 parts of alkaline activator, and 7 parts of fiber-based geopolymer.

4. The preparation method of a modified geopolymer gelling material according to claim 2 or 3, characterized in that: Fiber-based geopolymers are carbon fiber geopolymers.

5. A soft soil reinforcement construction method, characterized in that: Based on the modified geopolymer cementitious material described in claims 1 to 4, the soft soil reinforcement construction method is: Step Ⅰ: Select the construction equipment: powerful mixing head, matching excavator, intelligent proportioning workbench, powder silo; Step II: The modified geopolymer cementitious material is stored in a powder silo and a soft soil reinforcement slurry is prepared through an intelligent proportioning workbench. Before the material is fed and mixed, the material needs to be screened at least twice to reduce impurities and large particles in the material. Step III: Install the slurry using a high-pressure pump, matching excavator, and powerful mixing head. During the delivery process, a slurry control pressure gauge is required to monitor the slurry delivery pressure in the soft soil in-situ solidification system and stabilize the soft soil consolidation treatment. Step IV: Testing the compressive strength and shear strength of the cured product.

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