Foamed light soil based on shield muck as well as preparation method and application of foamed light soil

Abstract

The invention belongs to the technical field of building materials, and particularly relates to foamed light soil based on shield muck and a preparation method and application of the foamed light soil. The foamed light soil based on shield muck provided by the invention is prepared from the following components in parts by weight: 400 to 600 parts of shield muck, 32 to 60 parts of cement, 30 to 60 parts of slaked lime, 10 to 20 parts of gypsum, 0.2 to 0.8 part of foaming agent, 0.1 to 0.4 part of foam stabilizer, 1 to 3 parts of sodium metaaluminate, 1.5 to 2.5 parts of calcium chloride and 10 to 25 parts of water. The shield muck generated in the rail transit construction process is used as the main raw material, the brand-new preparation method of the foam light soil is developed, the application range of the shield muck is further expanded, and resource utilization of the shield muck is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and in particular relates to foamed lightweight soil based on shield slag, and a preparation method and application thereof. Background Art

[0002] As an environmentally friendly building material that has emerged in recent years, foam-mixed lightweight soil has been widely used in engineering practices such as roadbed widening and backfilling of platforms due to its light weight, efficient construction, strong controllability and excellent thermal insulation performance, effectively solving a series of engineering problems such as weak foundation and foundation settlement. However, compared with lightweight filling materials such as EPS blocks and EPS particles mixed lightweight soil, the current foam-mixed lightweight soil is still relatively high in cost and does not have a competitive advantage, which to a certain extent limits its widespread application in large-scale engineering projects.

[0003] With the rapid development of my country's rail transit industry, shield tunneling has become the mainstream technology in tunnel construction. It is widely popular because of its high safety, short construction period and low pollution. However, the large-scale application of this technology has also led to the increasingly prominent problem of shield slag as a solid waste. Due to its complex composition, high water content and low strength, shield slag is difficult to be directly applied to other fields, thus limiting the possibility of its resource utilization. At present, the main treatment method for shield slag is still transportation and disposal. However, the sites available for disposal in the city are extremely limited, resulting in a large amount of slag to be transported outside the city, which not only increases the high transportation cost and aggravates the financial burden of the construction unit, but also during the transportation and disposal process, the chemical substances contained in the shield slag may erode the soil and cause serious pollution to the local environment. At present, the solid waste utilization methods for shield slag are still relatively limited, and it is impossible to effectively exert the material properties of the shield slag itself, nor can it effectively consume the huge amount of abandoned slag. Therefore, developing new technologies for resource utilization of shield tunneling slag to achieve efficient utilization and environmental protection of shield tunneling slag has become an important issue that needs to be urgently addressed in the current field of rail transit construction.

[0004] Therefore, it is necessary to propose further solutions to the above problems. On the one hand, it can solve the problem of raw material demand for foam lightweight soil, and on the other hand, it can realize the resource utilization of shield slag and reduce environmental pollution. Moreover, through technological innovation and cost control, it is expected to reduce the manufacturing cost of foam mixed lightweight soil and improve its market competitiveness, thereby further promoting the widespread application of this material in the field of civil engineering materials. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention aims to provide a foamed lightweight soil based on shield slag, and a preparation method and application thereof. Using the shield slag generated during the rail transit construction process as the main raw material, a new preparation method of foamed lightweight soil has been developed, which further expands the application scope of shield slag and realizes the resource utilization of shield slag.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The first object of the present invention is to provide a foamed lightweight soil based on shield slag, which comprises the following components, in parts by weight: 400-600 parts of shield slag, 32-60 parts of cement, 30-60 parts of slaked lime, 10-20 parts of gypsum, 0.2-0.8 parts of foaming agent, 0.1-0.4 parts of foam stabilizer, 1-3 parts of sodium aluminate, 1.5-2.5 parts of calcium chloride and 10-25 parts of water.

[0008] Preferably, the initial moisture content of the shield slag is ≥25%; and the particle size of more than 90% of the shield slag is 0.075 mm to 1.5 mm.

[0009] Preferably, the foaming agent is a physical foaming agent, and the physical foaming agent is one of a plant protein foaming agent, an animal protein foaming agent and a composite foaming agent.

[0010] Preferably, the bubble group density of the foam blowing agent after foaming is 48-52 kg / m2, the water seepage rate is less than 6%, the sedimentation distance is less than 50 mm, and the pH is 8-12.

[0011] Preferably, the cement comprises ordinary Portland cement; and the foam stabilizer comprises silicone polyether microemulsion.

[0012] The second object of the present invention is to provide a method for preparing the foamed lightweight soil based on shield slag as described above, comprising the following steps:

[0013] S1. Foam preparation: foaming agent and water in a volume ratio of 1:30-60, stirring at a high speed of 300-2000 r / min for 10-30s, to obtain a prefabricated foam with a bubble group density of 48-52 kg / m2, a water bleeding rate of <6%, a settling distance of <50 mm, and a pH of 8-12;

[0014] S2. Material mixing: Mix the shield slag and cement in the formula amount and add them into a mixing pot, stir for 3 to 10 minutes at 600 to 800 r / min to obtain slurry A;

[0015] Add the formulated amount of water, slaked lime, gypsum, sodium aluminate and calcium chloride to the slurry A, and stir at 1200-1600 r / min for 3-10 min to obtain slurry B;

[0016] S3, foam mixing: the prefabricated foam obtained in step S1 is pumped into the slurry B in the stirring pot, and after being fully stirred and mixed, it is poured into the mold;

[0017] S4, casting and molding: The casting is carried out in layers and blocks. The thickness of a single layer should be controlled at 0.3-0.8m. The next layer of casting can be carried out after the upper layer is finally set.

[0018] S5. Curing and demoulding: After the top layer is constructed, the surface is immediately covered with a plastic film for moisturizing and curing. After demoulding, foamed lightweight soil is obtained.

[0019] Preferably, in the foam preparation of step S1, a fast mixer with a speed regulating function is used as a foaming device to prepare the foam, and the prepared foam is stored for no more than 1 hour.

[0020] Preferably, in the material mixing of step S2, the stirring pot comprises a cement mortar stirring pot.

[0021] Preferably, in the step S5 of curing and demoulding, the curing time is not less than 7 days and the curing temperature is 25±1°C.

[0022] Another object of the present invention is to provide the application of the above-mentioned foamed lightweight soil in roadbed engineering and structure backfill engineering.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention successfully prepares a foamed lightweight soil with qualified key properties such as fluidity, compressive strength, and bulk density. It not only efficiently solves the problem of shield slag treatment, but also opens up a new economically feasible way of solid waste utilization based on material properties, which is of great significance to promoting the development of environmentally friendly building materials.

[0025] (2) The method for preparing foamed lightweight soil based on shield slag provided by the present invention can recycle and reuse the shield slag generated during the construction of a tunnel using the shield method. In addition to producing foamed lightweight soil that meets the requirements of construction, it further reduces the impact of shield slag on the environment, thereby achieving resource recycling and reuse, which is more environmentally friendly.

[0026] (3) The foamed lightweight soil based on shield slag provided by the present invention can not only meet the use requirements in multiple scenarios, but also can be used locally, especially at the site of rail transit projects, greatly reducing the project cost. At the same time, it also realizes the green recycling of solid waste materials and contributes to environmental protection construction. DETAILED DESCRIPTION

[0027] The above contents of the present invention are further described in detail below by means of specific implementation methods in the form of examples, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples.

[0028] 1. Reagents and raw materials

[0029] product Buy from manufacturers model Ordinary Portland Cement Foshan Runhe Building Materials Co., Ltd. PO42.5R Slaked lime Guangxi Huitong New Building Materials Co., Ltd. Slaked lime plaster Zaozhuang Jinhai Gypsum Products Factory plaster Animal and plant protein foaming agent Shandong Yantai Chilong Building Energy Saving Technology Co., Ltd. Composite foaming agent Silicone resin polyether microemulsion Shandong Yousuo Chemical Technology Co., Ltd. FM-550 Sodium aluminate Shandong Gaotai Chemical Technology Co., Ltd. Sodium aluminate-A Calcium chloride Jiaxing Changli Chemical Co., Ltd. Calcium Chloride Anhydrous Bentonite Shandong Hongsheng Chemical Co., Ltd. BP183

[0030] 2. Instruments and Equipment

[0031] The foaming equipment was purchased from Changzhou Su Rui Instrument Co., Ltd., model JJ-1B 300W;

[0032] The pumping equipment was purchased from Shanghai Sunshine Pump Industry Co., Ltd., model G20-1;

[0033] The cement mortar mixing pot is purchased from Zhejiang Dedong Electric Motor Co., Ltd., model YDT90S. The measurement deviation of the mixing pot for cement, admixture and water does not exceed 2%, and the calculation deviation for fine aggregate does not exceed 3%.

[0034] 3. Shield Muck

[0035] The shield slag used in the present invention comes from the section between Shiyong Station and Wanqingsha Station of Guangzhou Metro, with an initial moisture content of ≥25%, more than 90% of the particle sizes being greater than 0.075 mm and less than 1.5 mm, and having the characteristics of a loose structure and more fine particles.

[0036] According to the relevant provisions of CJJT177-2012 "Technical Specifications for Bubble Mixed Lightweight Soil Filling Engineering", the particle size of the soil used shall not be greater than 4.75mm; according to GB50021-2001 "Geotechnical Engineering Investigation Code", the soil with a particle size greater than 0.075mm and a mass exceeding 50% of the total mass shall be named as silt soil. Therefore, the shield slag used in the present invention is silt soil.

[0037] 4. The inventive concept or design principle of the present invention:

[0038] With the rapid development of my country's rail transit industry and the widespread application of shield equipment, while the engineering efficiency has been improved, the generation of a large amount of shield slag has also become an environmental problem that cannot be ignored. At present, it is mainly treated by stacking in a disposal site, but this method still has the disadvantages of occupying urban land resources, polluting the land of the disposal site, and failing to fully utilize solid waste resources. At the same time, the resulting underground projects require a large amount of lightweight backfill soil. In past engineering practices, foamed lightweight soil made of high-quality clay was often used for backfilling. However, with the consumption of resources, the stock of high-quality clay is getting lower and lower, and the economic efficiency is declining. Shield slag has the characteristics of loose and porous materials, and has the material adaptability to be made into foamed lightweight soil. It is the best choice that takes into account both economy and environmental protection.

[0039] Shield slag has the material characteristics of loose structure, fine particles and rich content. The present invention introduces key regulators such as foaming agents and foam stabilizers. As air entraining agents, it not only reduces the density of shield slag, but also makes the foam lightweight soil light after careful proportioning. Secondly, the present invention uses shield slag as the main raw material, slaked lime as an activator, and cement, gypsum, sodium aluminate and calcium chloride as strength enhancers. Through scientific proportioning and process optimization, the mechanical properties and stability of the product are significantly improved.

[0040] It can be seen that the present invention utilizes the loose and porous structural characteristics of shield slag itself and adds air-entraining agent to further reduce the bulk density of the sample, so that the material properties can be fully utilized and the performance requirements of foam lightweight soil can be accurately met.

[0041] Example 1 Preparation of foamed lightweight soil based on shield slag of the present invention

[0042] The foamed lightweight soil based on shield slag of the present invention comprises the following components in parts by weight: 500 parts of shield slag, 40 parts of Portland cement, 40 parts of slaked lime, 15 parts of gypsum, 0.6 parts of animal and plant protein foaming agent, 0.3 parts of silicone resin polyether microemulsion, 3 parts of sodium metaaluminate, 2 parts of calcium chloride and 18 parts of water.

[0043] The method for preparing foamed lightweight soil based on shield slag of the present invention comprises the following steps:

[0044] S1. Foam preparation: The foaming agent and water are foamed in a volume ratio of 1:30, and stirred at a high speed of 1000 r / min for 20 seconds to obtain a bubble group density of 50 kg / m 2 , prefabricated foam with water bleeding rate <6%, settling distance <50mm, pH 8-12;

[0045] S2. Material mixing: Mix the shield slag and cement in the formula amount and add them into a mixing pot, stir at 700r / min for 3min to obtain slurry A;

[0046] Add the formulated amount of water, slaked lime, gypsum, sodium aluminate and calcium chloride to the slurry A, and stir at 1400 r / min for 5 min to obtain slurry B;

[0047] S3, foam mixing: the prefabricated foam obtained in step S1 is pumped into the slurry B in the stirring pot, and after being fully stirred and mixed, it is poured into the mold;

[0048] S4, casting and molding: The casting is carried out in layers and blocks. The thickness of a single layer should be controlled within 0.5m. The next layer of casting can be carried out after the upper layer is finally set.

[0049] S5. Curing and demoulding: After the top layer is constructed, the surface is immediately covered with a plastic film for moisturizing and curing, and foamed lightweight soil is obtained after demoulding.

[0050] Example 2 Preparation of foamed lightweight soil based on shield slag of the present invention

[0051] The foamed lightweight soil based on shield slag of the present invention comprises the following components in parts by weight: 500 parts of shield slag, 32 parts of Portland cement, 45 parts of slaked lime, 11 parts of gypsum, 0.4 parts of animal and plant protein foaming agent, 0.2 parts of silicone resin polyether microemulsion, 3 parts of sodium metaaluminate, 2.4 parts of calcium chloride and 12 parts of water.

[0052] The method for preparing foamed lightweight soil based on shield slag of the present invention comprises the following steps:

[0053] S1. Foam preparation: The foaming agent and water were foamed in a volume ratio of 1:30, and stirred at a high speed of 800 r / min for 20 seconds to obtain a bubble group density of 48 kg / m 2 , prefabricated foam with water bleeding rate <6%, settling distance <50mm, pH 8-12;

[0054] S2. Material mixing: Mix the shield slag and cement in the formula amount and add them into a mixing pot, stir at 700r / min for 3min to obtain slurry A;

[0055] Add the formulated amount of water, slaked lime, gypsum, sodium aluminate and calcium chloride to the slurry A, and stir at 1400 r / min for 5 min to obtain slurry B;

[0056] S3, foam mixing: the prefabricated foam obtained in step S1 is pumped into the slurry B in the stirring pot, and after being fully stirred and mixed, it is poured into the mold;

[0057] S4, casting and molding: The casting is carried out in layers and blocks. The thickness of a single layer should be controlled within 0.5m. The next layer of casting can be carried out after the upper layer is finally set.

[0058] S5. Curing and demoulding: After the top layer is constructed, the surface is immediately covered with a plastic film for moisturizing and curing. After demoulding, foamed lightweight soil is obtained.

[0059] Example 3 Preparation of foamed lightweight soil based on shield slag of the present invention

[0060] The foamed lightweight soil based on shield slag of the present invention comprises the following components in parts by weight: 500 parts of shield slag, 40 parts of Portland cement, 30 parts of slaked lime, 16 parts of gypsum, 0.4 parts of animal and plant protein foaming agent, 0.2 parts of silicone resin polyether microemulsion, 2 parts of sodium metaaluminate, 1.6 parts of calcium chloride and 20 parts of water.

[0061] The method for preparing foamed lightweight soil based on shield slag of the present invention comprises the following steps:

[0062] S1. Foam preparation: The foaming agent and water were foamed in a volume ratio of 1:50, and stirred at a high speed of 1500r / min for 30s to obtain a bubble group density of 52kg / m 2 , prefabricated foam with water bleeding rate <6%, settling distance <50mm, pH 8-12;

[0063] S2. Material mixing: Mix the shield slag and cement in the formula amount and add them into a mixing pot, stir at 700r / min for 3min to obtain slurry A;

[0064] Add the formulated amount of water, slaked lime, gypsum, sodium aluminate and calcium chloride to the slurry A, and stir at 1400 r / min for 5 min to obtain slurry B;

[0065] S3, foam mixing: the prefabricated foam obtained in step S1 is pumped into the slurry B in the stirring pot, and after being fully stirred and mixed, it is poured into the mold;

[0066] S4, casting and molding: The casting is carried out in layers and blocks. The thickness of a single layer should be controlled within 0.5m. The next layer of casting can be carried out after the upper layer is finally set.

[0067] S5. Curing and demoulding: After the top layer is constructed, the surface is immediately covered with a plastic film for moisturizing and curing. After demoulding, foamed lightweight soil is obtained.

[0068] Example 4 Preparation of foamed lightweight soil based on shield slag of the present invention

[0069] The foamed lightweight soil based on shield slag of the present invention comprises the following components in parts by weight: 500 parts of shield slag, 40 parts of Portland cement, 30 parts of slaked lime, 15 parts of gypsum, 0.2 parts of animal and plant protein foaming agent, 0.1 parts of silicone resin polyether microemulsion, 1 part of sodium metaaluminate, 1.6 parts of calcium chloride and 12 parts of water.

[0070] The method for preparing foamed lightweight soil based on shield slag of the present invention comprises the following steps:

[0071] S1. Foam preparation: The foaming agent and water are foamed at a volume ratio of 1:60, and stirred at a high speed of 500 r / min for 20 seconds to obtain a bubble group density of 50 kg / m 2 , prefabricated foam with water bleeding rate <6%, settling distance <50mm, pH 8-12;

[0072] S2. Material mixing: Mix the shield slag and cement in the formula amount and add them into a mixing pot, stir at 700r / min for 3min to obtain slurry A;

[0073] Add the formulated amount of water, slaked lime, gypsum, sodium aluminate and calcium chloride to the slurry A, and stir at 1400 r / min for 5 min to obtain slurry B;

[0074] S3, foam mixing: the prefabricated foam obtained in step S1 is pumped into the slurry B in the stirring pot, and after being fully stirred and mixed, it is poured into the mold;

[0075] S4, casting and molding: The casting is carried out in layers and blocks. The thickness of a single layer should be controlled within 0.5m. The next layer of casting can be carried out after the upper layer is finally set.

[0076] S5. Curing and demoulding: After the top layer is constructed, the surface is immediately covered with a plastic film for moisturizing and curing. After demoulding, foamed lightweight soil is obtained.

[0077] Example 5 Preparation of foamed lightweight soil based on shield slag of the present invention

[0078] The foamed lightweight soil based on shield slag of the present invention comprises the following components in parts by weight: 400 parts of shield slag, 50 parts of Portland cement, 40 parts of slaked lime, 12 parts of gypsum, 0.4 parts of animal and plant protein foaming agent, 0.2 parts of silicone resin polyether microemulsion, 4 parts of sodium metaaluminate, 2 parts of calcium chloride and 16 parts of water.

[0079] The method for preparing foamed lightweight soil based on shield slag of the present invention comprises the following steps:

[0080] S1. Foam preparation: The foaming agent and water are foamed in a volume ratio of 1:40, and stirred at a high speed of 1000 r / min for 10 seconds to obtain a bubble group density of 50 kg / m 2 , prefabricated foam with water bleeding rate <6%, settling distance <50mm, pH 8-12;

[0081] S2. Material mixing: Mix the shield slag and cement in the formula amount and add them into a mixing pot, stir at 700r / min for 3min to obtain slurry A;

[0082] Add the formulated amount of water, slaked lime, gypsum, sodium aluminate and calcium chloride to the slurry A, and stir at 1400 r / min for 5 min to obtain slurry B;

[0083] S3, foam mixing: the prefabricated foam obtained in step S1 is pumped into the slurry B in the stirring pot, and after being fully stirred and mixed, it is poured into the mold;

[0084] S4, casting and molding: The casting is carried out in layers and blocks. The thickness of a single layer should be controlled within 0.5m. The next layer of casting can be carried out after the upper layer is finally set.

[0085] S5. Curing and demoulding: After the top layer is constructed, the surface is immediately covered with a plastic film for moisturizing and curing. After demoulding, foamed lightweight soil is obtained.

[0086] Example 6 Preparation of foamed lightweight soil based on shield slag of the present invention

[0087] The foamed lightweight soil based on shield slag of the present invention comprises the following components, measured in parts by weight: 600 parts of shield slag, 60 parts of Portland cement, 60 parts of slaked lime, 10 parts of gypsum, 0.8 parts of animal and plant protein foaming agent, 0.4 parts of silicone resin polyether microemulsion, 1 part of sodium metaaluminate, 2.5 parts of calcium chloride and 24 parts of water.

[0088] The method for preparing foamed lightweight soil based on shield slag of the present invention comprises the following steps:

[0089] S1. Foam preparation: The foaming agent and water are foamed in a volume ratio of 1:30, and stirred at a high speed of 1000 r / min for 20 seconds to obtain a bubble group density of 50 kg / m 2 , prefabricated foam with water bleeding rate <6%, settling distance <50mm, pH 8-12;

[0090] S2. Material mixing: Mix the shield slag and cement in the formula amount and add them into a mixing pot, stir at 800r / min for 3min to obtain slurry A;

[0091] Add the formulated amount of water, slaked lime, gypsum, sodium aluminate and calcium chloride to the slurry A, and stir at 1500 r / min for 5 min to obtain slurry B;

[0092] S3, foam mixing: the prefabricated foam obtained in step S1 is pumped into the slurry B in the stirring pot, and after being fully stirred and mixed, it is poured into the mold;

[0093] S4, casting and molding: The casting is carried out in layers and blocks. The thickness of a single layer should be controlled within 0.5m. The next layer of casting can be carried out after the upper layer is finally set.

[0094] S5. Curing and demoulding: After the top layer is constructed, the surface is immediately covered with a plastic film for moisturizing and curing. After demoulding, foamed lightweight soil is obtained.

[0095] Comparative Example 1

[0096] Compared with Example 1, the shield slag in this comparative example is replaced by bentonite, and the rest is the same as Example 1.

[0097] The bentonite is sodium-based bentonite, a hydrous clay mineral mainly composed of montmorillonite, and its chemical composition and the proportion of each chemical component are similar to those of the shield slag used, but the bentonite has a higher viscosity.

[0098] Comparative Example 2

[0099] Compared with Example 1, the addition amount of shield slag in this comparative example is 800 parts, and the rest is the same as Example 1.

[0100] Comparative Example 3

[0101] Compared with Example 1, the amount of shield slag added in this comparative example is 200 parts, and the rest is the same as Example 1.

[0102] Comparative Example 4

[0103] Compared with Example 1, the amount of foaming agent added in this comparative example is 1.2 parts, and the rest is the same as Example 1.

[0104] Comparative Example 5

[0105] Compared with Example 1, the volume ratio of the foaming agent and water in the foam preparation of step S1 in the method for preparing foam lightweight soil in this comparative example is 1:10, and the rest is the same as Example 1.

[0106] Comparative Example 6

[0107] Compared with Example 1, the volume ratio of the foaming agent and water in the foam preparation of step S1 in the method for preparing foam lightweight soil in this comparative example is 1:60, and the rest is the same as Example 1.

[0108] Comparative Example 7

[0109] Compared with Example 1, the stirring time of the foam preparation in step S1 of the method for preparing foam lightweight soil in this comparative example is doubled to 40 seconds, and the rest is the same as Example 1.

[0110] Experiment 1 Performance Test

[0111] When used, the foamed lightweight soils prepared in Examples 1 to 6 and Comparative Examples 1 to 7 of the present invention were cured according to the method of CJJ / T 177-2012 "Technical Code for Filling Engineering of Bubble Mixed Lightweight Soil", and the wet bulk density, fluidity and compressive strength of the specimens with different formulas were tested.

[0112] Among them, fluidity is an important indicator to measure the fluidity of foam lightweight soil during the construction process, which directly affects the convenience of construction and the uniformity of pouring.

[0113] Compressive strength is the ability of foam lightweight soil to resist external compression damage and is a key indicator for evaluating its bearing capacity.

[0114] Bulk density refers to the weight of unit volume of foam lightweight soil and is an important indicator to measure its lightness.

[0115] The bulk density of foamed lightweight soil is much smaller than that of ordinary soil, which is one of the important reasons why it is widely used in various projects. In order to ensure the stability and reliability of engineering applications, the most important thing when preparing foamed lightweight soil is to ensure that its key properties such as fluidity, compressive strength, and bulk density are qualified.

[0116] (1) Test method:

[0117] The bulk density test was conducted using the method described in Appendix C of CJJ / T177-2012 "Technical Specifications for Foam-Mixed Lightweight Soil Filling Engineering" for wet bulk density test;

[0118] The fluidity test was conducted using the method described in Appendix D of CJJ / T 177-2012 "Technical Specifications for Foam-Mixed Lightweight Soil Filling Engineering";

[0119] The compressive strength test was carried out using the method described in Appendix F Strength Test of CJJ / T177-2012 “Technical Code for Foam Mixed Lightweight Soil Filling Engineering”.

[0120] (2) Technical requirements

[0121] Table 1

[0122] Experimental Project Technical requirements Wet bulk density test <![CDATA[The wet unit weight of the pattern should be between 4.5 and 6.5 kN / m 3 3.]]> Fluidity test The fluidity of the sample should be between 160 and 200 mm Strength test The sample strength should be greater than 0.6MPa

[0123] (3) Test results are shown in the following table:

[0124] Table 2

[0125]

[0126]

[0127] It can be seen from Table 1 above that the foamed lightweight soils prepared in Examples 1 to 6 of the present invention all meet the technical requirements and standards of "Technical Code for Bubble Mixed Lightweight Soil Filling Engineering" CJJ / T177-2012, ensuring the stability and reliability of engineering applications.

[0128] However, compared with Example 1, Comparative Example 1 replaces the shield slag with bentonite, and the strength is improved but the bulk density is too large, and the fluidity is greatly reduced and does not meet the requirements; Comparative Examples 2 and 3 adjust the amount of shield slag added, the wet bulk density and strength of Comparative Example 2 are reduced, and the fluidity is improved, which cannot meet the requirements of the specification; the wet bulk density and strength of Comparative Example 3 are improved, and the fluidity is reduced, which does not meet the requirements of the specification; Comparative Example 4 increases the amount of foaming agent, which greatly reduces the wet bulk density and strength, and does not meet the requirements of the specification; Comparative Examples 5 and 6 adjust the mass ratio of foaming agent to water, and the strength of Comparative Examples 5 and 6 becomes higher, but the bulk density is too large, and the fluidity of Comparative Example 6 is too high and does not meet the requirements of the specification; Comparative Example 7 doubles the stirring time in the foaming stage, the bulk density is increased, does not meet the requirements of the specification, and the strength does not change significantly.

[0129] It can be seen that the preparation method of foamed lightweight soil of the present invention is for bentonite with the same or similar chemical components as shield slag. If the addition amount of the foaming agent and the foam stabilizer is changed, or the stirring time in the foaming preparation process is changed, the bulk density effect of the prepared foamed lightweight soil will be worse. It can be seen that in the preparation method of foamed lightweight soil based on shield slag of the present invention, the foaming agent, the foam stabilizer and the foam preparation process play a key role in the preparation method of the present invention.

[0130] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A foamed lightweight soil based on shield slag, characterized in that: Calculated in parts by weight, the composition includes: 400-600 parts of shield slag, 32-60 parts of cement, 30-60 parts of slaked lime, 10-20 parts of gypsum, 0.2-0.8 parts of foaming agent, 0.1-0.4 parts of foam stabilizer, 1-3 parts of sodium aluminate, 1.5-2.5 parts of calcium chloride and 10-25 parts of water.

2. The foamed lightweight soil according to claim 1, characterized in that: The initial moisture content of the shield slag is ≥25%; and the particle size of more than 90% of the shield slag is 0.075mm to 1.5mm.

3. The foamed lightweight soil according to claim 1, characterized in that: The foaming agent is a physical foaming agent, and the physical foaming agent is one of a plant protein foaming agent, an animal protein foaming agent and a composite foaming agent.

4. The foamed lightweight soil according to claim 3, characterized in that: The bubble group density of the foam blowing agent after foaming is 48-52 kg / m 2 , water seepage rate <6%, sedimentation distance <50mm, pH8-12.

5. The foamed lightweight soil according to claim 1, characterized in that: The cement includes ordinary Portland cement; the foam stabilizer includes silicone polyether microemulsion.

6. A method for preparing foamed lightweight soil based on shield slag as claimed in any one of claims 1 to 5, characterized in that: The steps include: S1. Foam preparation: The foaming agent and water are foamed at a volume ratio of 1:30-60, and stirred at a high speed of 300-2000 r / min for 10-30s to obtain a bubble group density of 48-52 kg / m 2 , prefabricated foam with water bleeding rate <6%, settling distance <50mm, pH8-12; S2. Material mixing: Mix the shield slag and cement in the formula amount and add them into a mixing pot, stir for 3 to 10 minutes at 600 to 800 r / min to obtain slurry A; Add the formulated amount of water, slaked lime, gypsum, sodium aluminate and calcium chloride to the slurry A, and stir at 1200-1600 r / min for 3-10 min to obtain slurry B; S3, foam mixing: the prefabricated foam obtained in step S1 is pumped into the slurry B in the stirring pot, and after being fully stirred and mixed, it is poured into the mold; S4, casting and molding: The casting is carried out in layers and blocks. The thickness of a single layer should be controlled at 0.3-0.8m. The next layer of casting can be carried out after the upper layer is finally set. S5. Curing and demoulding: After the top layer is constructed, the surface is immediately covered with a plastic film for moisturizing and curing. After demoulding, foamed lightweight soil is obtained.

7. The preparation method according to claim 6, characterized in that: In the foam preparation step S1, a fast mixer with a speed regulating function is used as a foaming device to prepare the foam, and the prepared foam is stored for no more than 1 hour.

8. The preparation method according to claim 7, characterized in that: In the material mixing step S2, the stirring pot includes a cement mortar stirring pot.

9. The preparation method according to claim 6, characterized in that: In the step S5 of curing and demoulding, the curing time is not less than 7 days and the curing temperature is 25±1°C.

10. Use of the foamed lightweight soil according to any one of claims 1 to 5 in roadbed engineering and structure backfill engineering.

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