Inorganic cemented soil curing agent as well as preparation method and application thereof

Abstract

The invention provides an inorganic cemented soil curing agent as well as a preparation method and application thereof. The inorganic cemented soil curing agent is mainly composed of fly ash, mineral powder, ardealite and cement, by optimizing the material ratio, the inorganic cemented soil curing agent can obtain high strength and keep stable mechanical properties after long-term service, has excellent fluidity and construction adaptability, can be used in slurry formed by construction engineering soil such as engineering waste soil and construction muck and water, and can be used as a curing agent for the construction engineering soil. The formed flow-state solidified soil slurry has good rheological properties, can be filled in different application scenes according to actual requirements, and is solidified to form uniform solidified soil bodies, so that the shear resistance, the erosion resistance and the durability are improved, and efficient recycling of constructional engineering soil is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of mud solidification, and in particular to an inorganic cementitious soil solidifying agent and a preparation method and application thereof. Background Art

[0002] With the advancement of urbanization and the expansion of urban construction, a large amount of construction waste is generated every year. This type of construction waste, such as dredged silt, foundation pit mud, and shield tunneling waste, is often dumped and landfilled nearby, which not only wastes land resources but also seriously pollutes the ecological environment.

[0003] Currently, construction waste primarily consists of soil from foundation pit excavation, underground diaphragm wall trenching, pile foundation construction, and grouting reinforcement replacement. Excavation waste accounts for the largest volume of this waste. Construction waste, primarily clay and silty clay, is characterized by high viscosity and moisture content. It is often mixed with other waste, such as formwork and concrete blocks, and is typically transported for disposal. It is unsuitable for direct backfilling, especially in narrow spaces, such as fertilizer troughs (especially the area where support strips are replaced), special-shaped structures, core structures in renovation projects, and pipe trenches and corridors in municipal projects. Backfill is often difficult to compact and inefficient, and manual backfilling poses safety risks.

[0004] Solidifying raw soil with soil-solidifying materials is a common method for improving the overall performance of construction soil materials, such as engineering spoil and building debris. Soil solidifiers are new, green, environmentally friendly, and energy-saving engineering materials synthesized from one or more inorganic materials. When mixed with construction soil materials, they can reduce the distance between soil particles or, through a series of physical, chemical, and biological reactions within them, improve the soil's contact surface characteristics, filling the gaps between soil particles while generating new substances that can agglomerate and consolidate soil particles, thereby achieving the desired performance indicators in engineering projects.

[0005] Therefore, seeking a soil solidifier with simple components, simple preparation method, strong applicability and good solidification effect is of great significance to achieve efficient recycling of construction soil. Summary of the Invention

[0006] In response to the above-mentioned technical status, the present invention provides an inorganic cementitious soil solidifying agent, which has a simple and easy preparation method and can be used in slurries formed by construction engineering soil such as engineering waste soil and building debris and water. According to actual needs, it can be filled in different application scenarios to solidify into a uniform solidified soil body, thereby improving shear resistance, erosion resistance and durability, and realizing efficient recycling and reuse of construction engineering soil.

[0007] The technical solution provided by the present invention is: an inorganic cemented soil solidifying agent, which comprises the following raw materials in percentage by mass:

[0008] 40%-70% fly ash, 15%-30% mineral powder, 5%-15% phosphogypsum, 5%-15% cement, and 0.5%-1% additives.

[0009] The definition, requirements and classification of fly ash in the present invention comply with the definition, requirements and classification of fly ash described in the national standard GB / T 1596-2017 "Fly ash for cement and concrete".

[0010] The definition, requirements and classification of the mineral powder in the present invention conform to the definition, requirements and classification of granulated blast furnace slag powder described in the national standard GB / T18046-2000.

[0011] The definition, requirements and classification of the mineral powder in the present invention conform to the definition, requirements and classification of granulated blast furnace slag powder described in the national standard GB / T18046-2000.

[0012] Preferably, the fly ash is grade 3 fly ash, that is, the SiO2 content is less than 40%, the 45 μm square hole sieve residue is not more than 45%, the water requirement ratio is not more than 115%, and the loss on ignition is not more than 15%.

[0013] Preferably, the moisture content of the tertiary fly ash is less than 3%.

[0014] Preferably, the mineral powder is S95 mineral powder.

[0015] Preferably, the specific surface area of ​​S95 slag is greater than 500m 2 / kg, density less than 3g / cm 3 .

[0016] Preferably, the phosphogypsum is fourth-grade phosphogypsum.

[0017] Preferably, the cement is PO 42.5 ordinary Portland cement.

[0018] Preferably, the additive is one or more of cellulose ether, sodium polyacrylate, sodium polycarboxylate, xanthan gum, and sodium citrate.

[0019] The present invention also provides a method for preparing the inorganic cementitious soil solidifying agent, comprising the following steps:

[0020] Fly ash, mineral powder, phosphogypsum, cement and admixtures are weighed in proportion, and the components are placed in a drying device for mixing, so that the components are fully and evenly mixed to form a homogeneous curing agent powder, and the curing agent powder is placed in a constant temperature drying environment to obtain an inorganic cemented soil curing agent.

[0021] Preferably, the components are stirred and mixed in the equipment, more preferably, stirred at a stirring speed of 50 r / min-600 r / min for 2 min-3 min.

[0022] The inorganic cementing soil solidifying agent of the present invention can be used in a slurry formed by construction soil and water. It can be filled in different application scenarios according to actual needs to solidify into a uniform solidified soil, thereby improving shear resistance, scour resistance and durability, and realizing efficient recycling of construction soil. The details are as follows:

[0023] Construction soil such as construction waste soil and building debris is mixed with water to form slurry, and then an inorganic cementing soil solidifying agent is added to the slurry and mixed evenly to obtain fluidized solidified soil.

[0024] Preferably, the construction soil and water are mixed and stirred, the stirring rate is preferably 50 r / min-70 r / min, and the stirring time is preferably 1 min-10 min.

[0025] Preferably, the inorganic cementitious soil solidifying agent is added to the slurry, mixed and stirred, the stirring rate is preferably 50r / min-70r / min, and the stirring time is preferably 1min-10min.

[0026] Preferably, the engineering waste soil includes one or more of silty clay, sandy soil, and silty soil.

[0027] Preferably, the mass ratio of construction soil to water in the slurry is (0.5-1):1.

[0028] Preferably, in the fluidized solidified soil, the mass percentage of the construction soil is 80%-95%, and the mass percentage of the inorganic cementitious soil curing agent is 5%-20%.

[0029] The soil solidifying agent of the present invention is mainly composed of fly ash, mineral powder, phosphogypsum and cement, and the technical principle is as follows:

[0030] (1) The activation mechanism of fly ash and mineral powder improves the gelling ability of the curing agent. Fly ash and mineral powder are themselves potentially active materials. In an alkaline environment (cement contains calcium hydroxide, which is alkaline), their active materials SiO2 and Al2O3 react with calcium hydroxide to produce additional CSH and CAH gels. These secondary hydration products further enhance the cementing ability of the soil and reduce the precipitation of calcium hydroxide, thereby improving the durability of the solidified soil. In addition, the sulfate ions (SO4 2- ) reacts with calcium aluminate to form stable ettringite (AFt), which not only increases the early strength of the stabilized soil, but also improves the volume stability and reduces the risk of shrinkage and cracking.

[0031] (2) The mineral phase transformation process optimizes the microstructure and durability of the solidified soil. As the curing time increases, the CSH and CAH gels in the solidified soil gradually grow and combine with the soil particles to form a denser structure. In addition, the formation of calcium aluminate promoted by phosphogypsum and the action of admixtures allow the hydration products to further fill the pores at the micro level, improving the erosion resistance and durability of the solidified soil. Some admixtures can also regulate the hydration rate, avoid stress concentration during the solidification process, and ensure that the solidified soil maintains stable strength and volume properties during long-term service.

[0032] (3) The hydration reaction of cementitious materials is the core of the strength formation of solidified soil. During the hydration process, cement reacts with water to produce calcium silicate hydrate (CSH), calcium hydroxide (Ca(OH)2), and calcium aluminate hydrate (CAH). CSH gel is the main source of solidified soil strength. It fills the pores between particles and forms a continuous gel network, improving the cohesion and density of the soil. At the same time, the release of calcium hydroxide provides an alkaline environment, creating conditions for the secondary hydration reaction of fly ash and mineral powder, thereby further enhancing the strength and stability of the solidified soil.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The soil solidifying agent of the present invention is mainly composed of fly ash, mineral powder, phosphogypsum and cement. By rationally optimizing the material ratio and adopting a specific excitation mechanism, the solidifying agent can obtain high strength in the early stage and maintain stable mechanical properties after long-term service. At the same time, it has excellent fluidity and construction adaptability.

[0035] (2) The soil solidifying agent of the present invention can be used to form a slurry with construction engineering soil such as engineering waste soil and building debris and water. The resulting fluidized solidified soil slurry has good rheological properties and can be filled in different application scenarios according to actual needs to solidify into a uniform solidified soil body, thereby improving shear resistance, scour resistance and durability, and realizing efficient recycling of construction engineering soil. Compared with traditional solidifying materials such as stone, crushed stone, gravel, etc., it has the following advantages:

[0036] (2-1) The material cost is significantly reduced, reducing the consumption of natural sand and gravel resources;

[0037] (2-2) The material has a gentle curing process, which can reduce the risk of secondary damage to infrastructure. Its reasonable rheological properties can reduce the hidden dangers of uneven filling during the filling process, improve the stability of the foundation, and reduce the additional costs of subsequent maintenance and repair.

[0038] (2-3) It reduces the demand for high-carbon emission materials such as cement, thereby alleviating resource shortages and environmental pollution problems;

[0039] (2-4) This material maintains good stability in humid environments and is suitable for a variety of complex foundation environments.

[0040] (3) The present invention can adjust the fluidity, hardening speed, and consolidation strength of the fluidized solidified soil slurry according to project requirements. Furthermore, the present invention can control the initial and final setting times of the material by optimizing the curing formula, ensuring its adaptability in different application scenarios and improving project quality. In terms of long-term stability, the material exhibits superior consolidation properties and can form a uniform solidified soil mass. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The fluidized solidified soil in the embodiment of the present invention is poured into a mold to prepare a test block.

[0042] Figure 2 This is the compressive strength test of the test block in the embodiment of the present invention. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below with reference to the embodiments. It should be pointed out that the embodiments described below are intended to facilitate understanding of the present invention, and non-essential improvements and adjustments made to the present invention by those skilled in the art based on the above-mentioned contents of the present invention still fall within the scope of protection of the present invention.

[0044] The words “include”, “including” and the like used in the present invention should be interpreted as including rather than exclusive or exhaustive, that is, as “including but not limited to”.

[0045] Example 1:

[0046] The material composition and mass percentage of the inorganic cementitious soil solidifying agent are as follows:

[0047] Fly ash 50%, mineral powder 20%, phosphogypsum 15%, cement 14.5%, admixture 0.5%.

[0048] The additive is one or more of cellulose ether, sodium polyacrylate, sodium polycarboxylate, xanthan gum and sodium citrate.

[0049] The preparation method of the inorganic cementing soil solidifying agent is as follows:

[0050] Fly ash, mineral powder, phosphogypsum, cement and admixtures are weighed according to the mass percentages, and each component is placed in a dry mixing device. The components are stirred at a stirring speed of 50 r / min for 2 minutes to fully and evenly mix the components to form a homogeneous curing agent powder. The curing agent powder is placed in a constant temperature drying environment to obtain an inorganic cemented soil curing agent.

[0051] Add the engineering spoil into a water pool and stir it at a soil-water mass ratio of 0.5:1 to form an engineering spoil slurry; add the inorganic cementing soil solidifying agent into the engineering spoil slurry, and the mass ratio of the added inorganic cementing soil solidifying agent to the mass of the engineering spoil in the engineering spoil slurry is 95:5. After stirring evenly at a stirring rate of 60 r / min and a stirring time of 5 min, fluidized solidified soil is obtained.

[0052] Example 2:

[0053] The material composition and mass percentage of the inorganic cementitious soil solidifying agent are as follows:

[0054] Fly ash 40%, mineral powder 30%, phosphogypsum 15%, cement 14.5%, admixture 0.5%.

[0055] The additive is one or more of cellulose ether, sodium polyacrylate, sodium polycarboxylate, xanthan gum and sodium citrate.

[0056] The preparation method of the inorganic cementing soil solidifying agent is as follows:

[0057] Fly ash, mineral powder, phosphogypsum, cement and admixtures are weighed according to the mass percentages, and each component is placed in a dry mixing device. The components are stirred at a stirring speed of 55 r / min for 2 minutes to fully and evenly mix the components to form a homogeneous curing agent powder. The curing agent powder is placed in a constant temperature drying environment to obtain an inorganic cemented soil curing agent.

[0058] Add the engineering spoil into a water pool and stir it at a soil-water mass ratio of 1:1 to form an engineering spoil slurry; add the inorganic cementing soil solidifying agent into the engineering spoil slurry, and the mass ratio of the added inorganic cementing soil solidifying agent to the mass of the engineering spoil in the engineering spoil slurry is 85:15. After stirring evenly at a stirring rate of 60 r / min and a stirring time of 5 min, fluidized solidified soil is obtained.

[0059] Example 3:

[0060] The material composition and mass percentage of the inorganic cementitious soil solidifying agent are as follows:

[0061] Fly ash 60%, mineral powder 15%, phosphogypsum 10%, cement 14.5%, admixture 0.5%.

[0062] The additive is one or more of cellulose ether, sodium polyacrylate, sodium polycarboxylate, xanthan gum and sodium citrate.

[0063] The preparation method of the inorganic cementing soil solidifying agent is as follows:

[0064] Fly ash, mineral powder, phosphogypsum, cement and admixtures are weighed according to the mass percentages, and each component is placed in a dry mixing device. The components are stirred at a stirring speed of 55 r / min for 2 minutes to fully and evenly mix the components to form a homogeneous curing agent powder. The curing agent powder is placed in a constant temperature drying environment to obtain an inorganic cemented soil curing agent.

[0065] Add the engineering spoil into a water pool and stir it at a soil-water mass ratio of 1:1 to form an engineering spoil slurry; add the inorganic cementing soil solidifying agent into the engineering spoil slurry, and the mass ratio of the added inorganic cementing soil solidifying agent to the mass of the engineering spoil in the engineering spoil slurry is 90:10. After stirring evenly at a stirring rate of 60 r / min and a stirring time of 5 min, fluidized solidified soil is obtained.

[0066] Example 4:

[0067] The material composition and mass percentage of the inorganic cementitious soil solidifying agent are as follows:

[0068] Fly ash 70%, mineral powder 15%, phosphogypsum 10%, cement 4.5%, admixture 0.5%.

[0069] The additive is one or more of cellulose ether, sodium polyacrylate, sodium polycarboxylate, xanthan gum and sodium citrate.

[0070] The preparation method of the inorganic cementing soil solidifying agent is as follows:

[0071] Fly ash, mineral powder, phosphogypsum, cement and admixtures are weighed according to the mass percentages, and the components are placed in a dry mixing device. The components are stirred at a stirring speed of 60 r / min for 2 minutes to fully and evenly mix the components to form a homogeneous curing agent powder. The curing agent powder is placed in a constant temperature drying environment to obtain an inorganic cemented soil curing agent.

[0072] Add the engineering spoil into a water pool and stir it at a soil-water mass ratio of 1:1 to form an engineering spoil slurry; add the inorganic cementing soil solidifying agent into the engineering spoil slurry, and the mass ratio of the added inorganic cementing soil solidifying agent to the mass of the engineering spoil in the engineering spoil slurry is 90:10. After stirring evenly at a stirring rate of 60 r / min and a stirring time of 5 min, fluidized solidified soil is obtained.

[0073] Example 5:

[0074] The material composition and mass percentage of the inorganic cementitious soil solidifying agent are as follows:

[0075] Fly ash 65%, mineral powder 15%, phosphogypsum 5%, cement 14.5%, admixture 0.5%.

[0076] The additive is one or more of cellulose ether, sodium polyacrylate, sodium polycarboxylate, xanthan gum and sodium citrate.

[0077] The preparation method of the inorganic cementing soil solidifying agent is as follows:

[0078] Fly ash, mineral powder, phosphogypsum, cement and admixtures are weighed according to the mass percentages, and each component is placed in a dry mixing device. The components are stirred at a stirring speed of 55 r / min for 2 minutes to fully and evenly mix the components to form a homogeneous curing agent powder. The curing agent powder is placed in a constant temperature drying environment to obtain an inorganic cemented soil curing agent.

[0079] Add the engineering spoil into a water pool and stir it at a soil-water mass ratio of 1:1 to form an engineering spoil slurry; add the inorganic cementing soil solidifying agent into the engineering spoil slurry, and the mass ratio of the added inorganic cementing soil solidifying agent to the mass of the engineering spoil in the engineering spoil slurry is 90:10. After stirring evenly at a stirring rate of 60 r / min and a stirring time of 5 min, fluidized solidified soil is obtained.

[0080] The content of the soil solidifying agent material, the soil-water mass ratio in the engineering spoil slurry, and the mass ratio of the soil solidifying agent to the engineering spoil in the fluidized solidified soil in Examples 1-5 are shown in Table 1 below.

[0081] Table 1: Content of soil solidifying agent in Examples 1-5, soil-water ratio in engineering spoil slurry, and ratio of soil solidifying agent to engineering spoil in fluidized solidified soil

[0082]

[0083] like Figure 1 As shown, the fluidized solidified soil in Examples 1-5 has good rheological properties and can be filled in different application scenarios according to actual needs to solidify into a uniform solidified soil body, thereby improving shear resistance, erosion resistance and durability, and realizing efficient recycling of construction engineering soil. Figure 1 As shown, the fluidized solidified soil in Examples 1-5 was poured into a mold to prepare test blocks.

[0084] The fluidized solidified soil in Examples 1-5 was subjected to rheological testing. The fluidity of the mixture was tested according to the test method in GB / T 2419-2005 "Determination of fluidity of cement mortar": the mixture was quickly loaded into a fluid test mold in two layers. After compaction, the mold sleeve was removed and the surface of the mixture was scraped flat. The circular mold was gently lifted upward, and the maximum expansion diameter of the mixture was measured with a caliper.

[0085] The compressive strength and shrinkage properties of the fluidized solidified soil in Examples 1-5 after solidification were tested. The compressive strength test method is as follows:

[0086] like Figure 2 As shown, the test blocks were taken out and placed on the fixture of the automatic cement strength testing machine for compressive strength measurement. The loading speed of the testing machine was set to 2.4KN / S. Three test blocks with different admixture amounts were measured for each group. Based on the results obtained, the average value was taken as the compressive strength value of the test block.

[0087] The shrinkage of the specimens was measured according to the method specified in JGJ70-90, "Test Methods for Basic Properties of Building Mortar." The mold dimensions were 70.7 mm × 70.7 mm × 70.7 mm. The well-mixed specimens were poured into the mold, vibrated and smoothed, and then cured in a 20°C curing room. After 24 hours, the specimens were removed from the molds, and their original data were measured and recorded. After the measurements were completed, the specimens were returned to the curing room for further curing. The lengths of the specimens were then measured at 3, 7, and 28 days of curing.

[0088] The test results are shown in Table 2 below.

[0089] Table 2: Properties of the fluidized soil prepared in Examples 1-5

[0090]

[0091] As can be seen from Table 2, the fluidized solidified soils of Examples 1-5 exhibit significant rheological properties, compressive strength growth patterns, and volume stability under different mix ratio conditions.

[0092] The fluidity test shows that the fluidity of the solidified soil changes with the adjustment of the mix ratio, with the maximum fluidity reaching 460 mm and the minimum fluidity being 340 mm. Higher fluidity is conducive to construction operability, but may affect the early strength after consolidation.

[0093] The compressive strength test results show that the strength range at 3d age is 0.22MPa-0.47MPa, the strength range at 7d age is 0.53MPa-0.86MPa, and the strength range at 28d age is 0.86MPa-1.54MPa. The increase in age promotes the formation of hydration products and improves the bonding strength of the solidified soil.

[0094] The shrinkage rate test shows that the 7d shrinkage rate basically decreases with the increase of compressive strength, ranging from 0.37% to 0.76%. Low shrinkage rate helps to improve volume stability and reduce the risk of shrinkage cracking.

[0095] The experimental results verified the influence of curing agent ratio on the fluidity, mechanical strength and volume stability of fluidized solidified soil. Optimizing the component ratio can achieve a coordinated match of high fluidity, strength growth and low shrinkage performance, thereby improving engineering adaptability and durability.

[0096] The above embodiments provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An inorganic cementitious soil solidifying agent, characterized by: Calculated by mass percentage, it includes the following raw materials: 40%-70% fly ash, 15%-30% mineral powder, 5%-15% phosphogypsum, 5%-15% cement, and 0.5%-1% additives.

2. The inorganic cementitious soil solidifying agent according to claim 1, wherein: The fly ash is grade 3 fly ash, and its water content is preferably less than 3%.

3. The inorganic cementitious soil solidifying agent according to claim 1, wherein: The mineral powder is S95 mineral powder, and its specific surface area is preferably greater than 500m 2 / kg, and the density is preferably less than 3g / cm3.

4. The inorganic cementitious soil solidifying agent according to claim 1, wherein: The phosphogypsum is fourth-grade phosphogypsum.

5. The inorganic cementitious soil solidifying agent according to claim 1, wherein: The cement is PO 42.5 ordinary Portland cement.

6. The inorganic cementitious soil solidifying agent according to claim 1, wherein: The additive is one or more of cellulose ether, sodium polyacrylate, sodium polycarboxylate, xanthan gum and sodium citrate.

7. The method for preparing the inorganic cementitious soil solidifying agent according to any one of claims 1 to 6, wherein: The following steps are involved: Fly ash, mineral powder, phosphogypsum, cement and admixtures are weighed in proportion, and the components are placed in a drying device for mixing, so that the components are fully and evenly mixed to form a homogeneous curing agent powder, and the curing agent powder is placed in a constant temperature drying environment to obtain an inorganic cemented soil curing agent.

8. A method for preparing fluidized solidified soil, characterized by: Mix construction soil and water to form a slurry; add the inorganic cementing soil curing agent according to any one of claims 1 to 6 into the slurry, mix them evenly, and obtain fluidized solidified soil.

9. The method for preparing fluidized solidified soil according to claim 8, wherein: The mass ratio of construction soil to water in the slurry is (0.5-1):

1.

10. The method for preparing fluidized solidified soil according to claim 8, wherein: In the fluidized solidified soil, the mass percentage of construction engineering soil is 80%-95%, and the mass percentage of inorganic cemented soil solidifying agent is 5%-20%.

Images