Slag-based clay curing agent as well as preparation method and application thereof

Abstract

The invention relates to the technical field of building engineering materials, and discloses a slag-based clay curing agent, which is prepared from the following raw materials in parts by weight: 15 to 25 parts of cement, 30 to 40 parts of slag powder, 20 to 30 parts of steel slag powder, 10 to 20 parts of regenerated micro powder, 10 to 15 parts of phosphogypsum and 5 to 10 parts of additives. The slag-based clay curing agent can be prepared into a cured soil mixture for road engineering roadbed filler, can also be prepared into liquid cured soil with high flowability to be applied to underground engineering parts such as narrow fat grooves and holes where plain soil is difficult to backfill, and can be used as a cementing material for replacing cement to be used for producing regenerated products such as regenerated baking-free bricks. Industrial solid wastes (blast furnace slag, steel slag, ardealite and the like) are mainly adopted as main raw materials to prepare the clay curing agent, and compared with a common cement curing agent, resource utilization of bulk solid wastes such as steel slag, ardealite and the like in the industrial solid wastes, waste clay and construction waste regenerated micro powder is achieved, and the purpose of carbon reduction is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of building engineering materials, and in particular to a slag-based clay curing agent, a preparation method and application thereof. Background Art

[0002] With the continuous development of urbanization, tens of millions of cubic meters of waste soil are generated every year in urban construction projects such as highway and house foundation construction, among which clay accounts for a relatively high proportion. This type of waste soil has the characteristics of high natural moisture content, low bearing capacity and high compressibility. It cannot be used as the natural foundation bearing layer of the proposed building. Traditional disposal methods such as open-air stacking or landfill will cause a large waste of land resources and will also bring extremely high pollution risks.

[0003] At the same time, my country produces billions of tons of industrial solid waste every year. The storage of major industrial solid wastes such as fly ash, blast furnace slag, steel slag, phosphogypsum, etc. not only occupies land resources, but also easily damages the surrounding environment and endangers human health. Therefore, under the premise of ensuring environmental safety, we should actively explore ways to utilize industrial solid waste in the fields of soil improvement, roadbed materials, construction projects, etc.

[0004] As the most widely used soil solidifier, cement is widely used in engineering construction. However, the production cost of cement is high, and the manufacture of cement consumes a lot of coal and electricity energy, and the production process will produce a lot of carbon dioxide. In addition, there are large differences in the solidification effect of cement on different types of soil. Studies have found that cement is not effective in solidifying clay with a large plasticity index. Simply increasing the amount of cement has limited effect on improving the strength of clay in the later stage of solidification, and is prone to shrinkage and cracking. Therefore, choosing a suitable solidifying agent material according to the characteristics of the soil can achieve the best solidification effect. Industrial solid wastes such as fly ash and slag have certain activity. The combination of cement and industrial solid waste will stimulate the active substances in the soil and undergo hydration reactions to generate cementitious materials such as calcium vanadium, which can achieve the effect of improved solidification and greatly reduce the amount of cement in the solidifying agent.

[0005] Therefore, developing a high-performance clay curing agent with industrial solid waste as the main component can not only effectively improve the strength of clay in the later stage of curing and reduce the cost of curing agent materials, but also reduce energy consumption and improve the level of resource utilization of industrial solid waste and construction waste. Summary of the invention

[0006] 1. Technical issues to be resolved

[0007] In view of the deficiencies in the prior art, the present invention provides a slag-based clay curing agent, a preparation method and an application thereof. The slag-based clay curing agent can improve the resource utilization rate of clay and industrial solid waste, and reduce the amount of cement used in traditional curing agents and their carbon emissions.

[0008] (II) Technical solution

[0009] To achieve the above object, the present invention provides the following technical solution: a slag-based clay curing agent, comprising the following raw materials in proportion by weight:

[0010] 15-25 parts of cement, 30-40 parts of slag powder, 20-30 parts of steel slag powder, 10-20 parts of recycled micro powder, 10-15 parts of phosphogypsum and 5-10 parts of admixture.

[0011] Preferably, the slag powder is a by-product produced during blast furnace ironmaking, and has a grade ≥ S95, a specific surface area ≥ 400 m2 / kg, and a 28d activity ≥ 95%.

[0012] Preferably, the steel slag powder is a by-product produced during steelmaking in the steel industry, with a specific surface area of ​​≥350 m2 / kg and a 28d activity of ≥65%.

[0013] Preferably, the regenerated fine powder is fine waste particles with a particle size of less than 0.075 mm produced in the process of preparing the regenerated aggregate, and the activity index is ≥60%.

[0014] Preferably, the cement is PO 42.5 silicate cement, and the admixtures include an activator and an activator.

[0015] Preferably, the activator is one or a combination of sodium sulfate, sodium silicate and sodium hydroxide.

[0016] Preferably, the active agent is sodium dodecyl sulfate powder.

[0017] The above slag-based clay curing agent can be used in underground backfill engineering, road engineering and recycled products, specifically:

[0018] Application in underground backfill engineering, the method is as follows:

[0019] Step 1: According to the strength and flow value requirements of the engineering backfill, determine the curing agent dosage and water ratio of the liquid solidified soil through experiments;

[0020] Step 2, pre-treating the waste clay by drying and crushing;

[0021] Step 3: Then, the slag-based curing agent (recommended dosage is 8%-16%) and water are mixed according to the weight ratio of the clay, and stirred evenly using a specific stirring device to form a fluid liquid curing soil mixture;

[0022] Step 4: According to the on-site construction conditions, select a chute or pump to pump the liquid solidified soil to the foundation pit, fertilizer trough, holes and other parts that need to be filled.

[0023] The application in road engineering is as follows:

[0024] Step 1: Determine the proportion of clay and gravel aggregate in the roadbed soil according to the road grade and roadbed depth, and determine the dosage of the slag-based curing agent in the roadbed soil through experiments;

[0025] Step 2, pre-treating the waste clay by drying and crushing;

[0026] Step 3, adding the curing agent to the roadbed soil composed of the above-mentioned clay and sand and gravel aggregates according to the mass ratio (recommended dosage 10%-20%), controlling the moisture content ≤15%, and using a specific mixing equipment to stir into a cured soil mixture;

[0027] Step 4: Use a paver and a roller to spread and compact the solidified soil mixture in layers. After the solidified roadbed is rolled into shape, it should be cured for at least 7 days.

[0028] The application method in unburned recycled brick products is as follows:

[0029] Step 1: According to the raw material ratio of MU10 recycled bricks (including cement, 0-5mm recycled stone chips, and water), the above-mentioned slag-based curing agent is used to completely replace cement;

[0030] Step 2: according to the above raw material ratio, cement, 0-5 mm stone chips and water are measured in sequence, and after measurement, they are stirred in a planetary mixer for 2 minutes to form a uniform mixture;

[0031] Step 3, the uniform mixture is conveyed to the brick making machine module through a belt, and the recycled bricks are formed by vibration and pressing;

[0032] Step 4: After the recycled bricks are formed for 2-3 days, they are immersed in water for curing. The immersion curing lasts for 10-20 minutes until the surface of the recycled bricks no longer absorbs water, and then they are naturally dried in a cool place.

[0033] A method for preparing a slag-based clay curing agent comprises the following steps:

[0034] S1. Curing agent ingredients: weigh the raw material components of cement, slag powder, steel slag powder, recycled micro powder, phosphogypsum, and admixtures according to the weight ratio;

[0035] S2, stirring: adding the raw materials weighed in step S1 into a mixer in batches, mixing and stirring thoroughly. The raw materials are mixed by dry mixing, and the dry mixing time should be no less than 2 minutes;

[0036] S3, bagging: placing the powder mixed and stirred in step S2 in a sealed bag for drying and storage at room temperature to form a slag-based clay curing agent.

[0037] (III) Beneficial effects

[0038] Compared with the prior art, the present invention provides a slag-based clay curing agent, a preparation method and an application thereof, which have the following beneficial effects:

[0039] 1. Provide a way for the disposal and resource utilization of industrial solid waste and construction waste: The present invention mainly uses industrial solid waste (blast furnace slag, steel slag, phosphogypsum, etc.) as the main raw material to prepare clay curing agent. Compared with common cement curing agent, it realizes the resource utilization of bulk solid waste such as steel slag and phosphogypsum in industrial solid waste and waste clay, construction waste recycled micro powder and achieves the purpose of carbon reduction, reducing the serious pollution problem caused by the stacking of industrial solid waste such as phosphogypsum to the soil, atmosphere and water environment;

[0040] 2. High curing strength: Among the raw materials of the curing agent of the present invention, raw materials such as cement, blast furnace slag, steel slag, and recycled micropowder have hydration synergistic effects and particle filling effects. During the hydration process, phosphogypsum can react with cement and slag to form hydration products such as calcium vanadium (AFt). The activity of components such as slag powder and steel slag powder is further activated in the alkaline environment of the activator to form a large amount of hydration gelling products such as CSH. In the later stage, CSH gel wraps the calcium vanadium to form a dense composite structure, which greatly improves the strength of the cured clay. Sodium dodecyl sulfate has strong foaming and dispersing abilities, can be adsorbed on the surface of wet clay particles and replace the free water between soil particles, effectively reducing the viscosity of the clay and enhancing the permeability of the cured soil body;

[0041] 3. Wide application scenarios: After adding slag-based curing agent to clay, the curing agent dosage and water consumption are determined according to indoor tests, and liquid solidified soil with high fluidity can be prepared and applied to underground engineering parts such as narrow fertilizer troughs and holes where it is difficult to backfill with plain soil. It can also be prepared into solidified soil mixtures that can be used as roadbed fillers for road engineering, and can also be used as a cementitious material to replace cement for the production of recycled products such as recycled unburned bricks;

[0042] 4. Obvious economic benefits: The raw materials of the clay curing agent of the present invention are widely available and easy to obtain. The cost of bulk solid wastes such as slag, steel slag, and phosphogypsum is low. In addition, the amount of cement in the curing agent of the present invention is relatively low, and the cost of the curing agent material is significantly reduced, which has a high economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is the slag-based clay curing agent of the present invention;

[0044] Figure 2 It is a diagram of a solidified soil sample of the present invention;

[0045] Figure 3 It is a diagram of a recycled brick product of the present invention;

[0046] Figure 4This is an electron microscope scan of pure raw soil without solidification;

[0047] Figure 5 This is an electron microscope scanning image of the slag-based slag solidifying agent solidified soil after curing for 7 days in Example 3 of the present invention;

[0048] Figure 6 This is an electron microscope scanning image of the soil solidified with the slag-based slag solidifying agent after curing for 28 days in Example 3 of the present invention. DETAILED DESCRIPTION

[0049] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] See also Figure 1-6 In order to further illustrate the present invention, the following examples are used for detailed description. The regenerated micro powder in the following examples of the present invention is fine waste particles of 0.075 mm or less obtained by screening and grinding the regenerated fine aggregate of a construction waste material factory in Hanyang District, Wuhan City, with an activity index of ≥60%. The other raw materials used are all commercially purchased commodities. Among them, the main chemical component of phosphogypsum is calcium sulfate, which is taken from the solid waste of steel plant production. The slag powder is a by-product produced during blast furnace ironmaking, with a grade of ≥S95 and a specific surface area of ​​≥400m 2 / kg, 28d activity ≥95%, steel slag powder is a by-product produced during steelmaking in the steel industry, with a specific surface area ≥350m2 / kg, 28d activity ≥65%, cement is PO 42.5 silicate cement, admixtures include activators and activators, the activator is one or a combination of sodium sulfate, sodium silicate, sodium hydroxide, and the activator is sodium dodecyl sulfate powder.

[0051] Embodiment 1:

[0052] The clay curing agent is mainly composed of the following raw materials in the following mass proportions: 15 parts of cement, 30 parts of blast furnace slag powder, 20 parts of steel slag powder, 15 parts of recycled micropowder, 10 parts of phosphogypsum, and 10 parts of admixture.

[0053] The admixtures are 8 parts of stimulator and 2 parts of active agent, wherein the ratio of sodium sulfate to sodium hydroxide in the stimulator is 3:1.

[0054] The preparation process of clay curing agent is as follows:

[0055] The raw materials were weighed according to the dosage of this embodiment, added into a mixer in sequence, and stirred for 3-5 minutes. After mixing evenly, the materials were discharged to obtain a clay curing agent.

[0056] The application process of clay curing agent is as follows:

[0057] Step 1, take the following raw materials by weight: 100 parts of clay and 12 parts of clay curing agent, 40-45 parts of water;

[0058] Step 2: Add the above-mentioned clay, clay curing agent and water to a double-shaft horizontal mixer, mix for 3-5 minutes until the mixture is uniform, and control the flow value to be 140mm-200mm to obtain a liquid cured soil mixture. At the same time, prepare a cured soil sample using a 70.7mm*70.7mm*70.7mm test mold;

[0059] Step 3: Set up a chute or a mud pool on site according to the backfill location, and fill the liquid solidified soil mixture in step 2 through the chute or temporarily store it in the mud pool and then fill it through a pumping pipeline. During the filling process, the liquid solidified soil reaches the designated filling surface by gravity and is completely solidified 24 hours after the filling is completed.

[0060] Among them, the pretreatment method of clay is: take the original clay soil, determine its moisture content to be 35%, naturally air-dry or air-dry until the moisture content is less than 20%, first use an excavator to perform coarse screening to remove impurities such as stones over 20 cm, and then use a two-stage screenless crusher to crush it, and the particle size after crushing is ≤3mm.

[0061] Example 2

[0062] Other conditions are the same as those in Example 1, and the clay curing agent is mainly composed of the following raw materials in the following mass proportions:

[0063] 15 parts of cement, 35 parts of blast furnace slag powder, 20 parts of steel slag powder, 15 parts of recycled micropowder, 10 parts of phosphogypsum, and 5 parts of admixture.

[0064] The admixture is 4 parts of stimulator and 1 part of active agent, wherein the ratio of sodium sulfate to sodium hydroxide in the stimulator is 3:1.

[0065] Example 3

[0066] Other conditions were the same as in Example 1, and the ratio of sodium sulfate to sodium silicate in the admixture was 1:1.

[0067] Example 4

[0068] Other conditions are the same as those in Example 1. The clay curing agent is mainly composed of the following raw materials in the following weight ratios: 15 parts of cement, 30 parts of blast furnace slag powder, 30 parts of steel slag powder, 10 parts of recycled micropowder, 10 parts of phosphogypsum, and 5 parts of admixture.

[0069] The admixture is 4 parts of activator and 1 part of active agent, wherein the ratio of sodium silicate to sodium hydroxide in the activator is 1:1.

[0070] Example 5

[0071] Other conditions are the same as those in Example 1. The clay curing agent is mainly composed of the following raw materials in the following weight ratios: 25 parts of cement, 30 parts of blast furnace slag powder, 20 parts of steel slag powder, 10 parts of recycled micropowder, 10 parts of phosphogypsum, and 5 parts of admixture.

[0072] The admixture is 4 parts of stimulator and 1 part of active agent, wherein the ratio of sodium sulfate to sodium hydroxide in the stimulator is 3:1.

[0073] Among the raw materials of the present invention:

[0074] Cement is a commonly used soil solidifying agent, which can react with water to generate hydration products such as Ca(OH)2, CSH gel, and AFt, which play a role in solidifying the strength of the soil;

[0075] Blast furnace slag powder is a highly active mineral admixture with granulated blast furnace slag as the main component. Its main chemical composition is Cao, SiO2, Al2O3. It is similar to the chemical composition of silicate cement and can produce a volcanic ash effect with cement. In an alkaline environment, it can further react with cement hydration product Ca(OH)2 to form CSH gel, thereby improving the early strength of the solidified soil.

[0076] Steel slag contains active substances such as tricalcium silicate and aluminoferrite. The alkaline environment produced by the hydration of these active substances can promote the occurrence of volcanic ash reaction and generate cementitious products such as CSH, which can fill the pores of the soil.

[0077] Recycled micro powder is waste micro powder with a size of less than 0.075 mm obtained by screening and grinding recycled fine aggregate. After grinding, it has a high activity index. The unhydrated cement particles in the recycled micro powder can be further hydrated to form cementitious substances such as CSH under the stimulation of alkaline environment, and can fill the pores in the soil.

[0078] Phosphogypsum can provide the system with During the hydration process, it can react with cement and slag to promote the formation of products AFt and CSH, further improving the strength of the solidified soil;

[0079] Sodium sulfate, sodium silicate and sodium hydroxide are commonly used activators in activator cementitious materials. They dissolve in water to become alkaline. The alkaline environment can stimulate the reactivity of blast furnace slag, steel slag and recycled micro powder, and promote the hydration reaction of the above components.

[0080] Sodium dodecyl sulfate is a common anionic surfactant with strong foaming and dispersing abilities. It can be adsorbed on the surface of wet clay particles and replace the free water between soil particles. It can effectively reduce the viscosity of clay and enhance the permeability of solidified soil.

[0081] To illustrate the efficacy of the soil solidifying agent of the present invention, the inventors of the present application conducted the following performance tests with reference to the specification "Technical Standard for Application of Soil Solidifying Agents" (CJJ / T286-2018):

[0082] Comparative Example 1

[0083] Compared with Example 1, Comparative Example 1 is different in that the addition of blast furnace slag powder, steel slag powder, recycled micropowder, phosphogypsum and admixtures is eliminated, and ordinary Portland cement of Conch brand PO 42.5 is directly used as a control experiment.

[0084] Comparative Example 2

[0085] Compared with Example 1, Comparative Example 2 is different in that the addition of the admixture is eliminated, and the other components are the same as those of Example 1.

[0086] The clay excavated from the project was used as the basic soil sample, which was taken from the excavated slag from the foundation pit of a project under construction in Wuhan. The clay had a moisture content of about 25%, a liquid limit of 29.20, a plastic limit of 16.80, and an organic matter content of <5%. The clay curing agents prepared in the above five embodiments and comparative examples 1 and 2 were added to the clay at a dosage of 12%, respectively, and then the same amount of water was added to prepare liquid cured soil. The unconfined compressive strength and water stability coefficient of the cured soil samples at 7d and 28d were tested.

[0087] The preparation process of liquid solidified soil is as follows:

[0088] Step 1, take the following raw materials by weight: 100 parts of clay and 12 parts of clay curing agent, 40-45 parts of water;

[0089] Step 2: Add the above-mentioned clay, clay curing agent and water into a double-shaft horizontal mixer respectively, mix for 3-5 minutes until the mixture is uniform, and control the flow value at 140mm-200mm to obtain a liquid cured soil mixture. At the same time, use a 70.7mm*70.7mm*70.7mm test mold to prepare a cured soil sample.

[0090] Among them, the pretreatment method of clay is: take the original clay soil, determine its moisture content to be 35%, naturally air-dry or air-dry until the moisture content is less than 20%, first use an excavator to perform coarse screening to remove impurities such as stones over 20 cm, and then use a two-stage screenless crusher to crush it, and the particle size after crushing is ≤3mm.

[0091] The test results are shown in Table 1:

[0092] Table 1 Experimental data table of each embodiment

[0093]

[0094]

[0095] The test results in Table 1 show that the 7d and 28d unconfined compressive strength and water stability coefficient of the slag-based solidified soil in the embodiment of the present invention are improved compared with the cement-solidified soil in Comparative Example 1, indicating that multi-source solid waste has a synergistic effect and the slag-based solidifying agent system is superior to the pure cement system.

[0096] By comparing Examples 1-5 and Comparative Example 2, it can be seen that in the clay curing agent of the present invention, the main function of the admixture is to stimulate the reaction activity of each component and promote the hydration synergy of each component to generate more cementitious products, so that the structure of the soil becomes denser. According to the test data in Table 1, the optimal mix ratio of the slag-based clay curing agent provided by the present invention is cement: blast furnace slag powder: steel slag powder: recycled micropowder: phosphogypsum: admixture = 15:30:20:15:10:10 (the ratio of sodium sulfate to sodium silicate in the activator is 1:1). When it is applied to clay curing, the 7d strength is 0.90MPa, the 28d strength is 1.35MPa, and the 28d water stability coefficient is 0.90.

[0097] The electron microscope observation of the state of the pure raw soil and the solidified soil samples of Example 3 after curing for 7 days and 28 days, the electron microscope scanning images are as follows Figure 2 , Figure 3 , Figure 4 As shown, it can be seen that the internal structure of the uncured pure raw soil is loose, the soil particles are loose, and there are many pores and irregular impurities between the particles. When the cured soil sample of Example 3 is cured to the age of 7 days, the sheet structure composed of clay particles on the surface of the soil particles has basically consolidated into a whole, and on the surface of the cured soil, it can be seen that the needle rod calcium vanadium (AFt) and calcium silicate hydrate (CSH) gel substances are obviously adhered and overlapped. These hydration products cover the surface of the soil particles or interweave and fill the pores between the soil skeleton. When the curing is to the age of 28 days, the hydration products inside the slag continue to increase, the interaction between the particles is significantly enhanced, the porosity of the soil is further reduced, and the soil particles are cemented to form a dense spatial network structure.

[0098] In combination with Examples 1-5, it can be seen that the present invention uses silicate cement, blast furnace slag powder, steel slag powder, recycled micropowder, phosphogypsum and admixtures, and adjusts the component formula to prepare a clay curing agent that meets the relevant performance requirements of "Soil Solidification Admixture" (CJ / T486-20152), which not only reduces the production cost of the curing agent, but also improves the resource utilization rate of solid waste. At the same time, the present application provides that clay is improved and used as engineering backfill material, which has a driving significance for effectively reducing engineering costs and realizing the resource utilization of slag.

[0099] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A slag-based clay curing agent, characterized in that: The invention comprises the following raw materials in proportion by weight: 15-25 parts of cement, 30-40 parts of slag powder, 20-30 parts of steel slag powder, 10-20 parts of recycled micro powder, 10-15 parts of phosphogypsum and 5-10 parts of admixture.

2. A slag-based clay curing agent according to claim 1, characterized in that: The slag powder is a by-product produced during blast furnace ironmaking, with a grade of ≥S95 and a specific surface area of ​​≥400m 2 / kg, 28d activity ≥95%.

3. A slag-based clay curing agent according to claim 1, characterized in that: The steel slag powder is a by-product produced during steelmaking in the steel industry, with a specific surface area of ​​≥350m2 / kg and a 28d activity of ≥65%.

4. The slag-based clay curing agent according to claim 1, characterized in that: The regenerated fine powder is fine waste particles with a particle size of less than 0.075 mm produced in the process of preparing the regenerated aggregate, and the activity index is ≥60%.

5. The slag-based clay curing agent according to claim 1, characterized in that: The cement is PO 42.5 silicate cement, and the admixtures include an activator and an activator.

6. The slag-based clay curing agent according to claim 5, characterized in that: The activator is one or a combination of sodium sulfate, sodium silicate and sodium hydroxide.

7. The slag-based clay curing agent according to claim 5, characterized in that: The active agent is sodium dodecyl sulfate powder.

8. A slag-based clay curing agent as claimed in any one of claims 1 to 7 which can be used in underground backfill engineering, road engineering and recycled products.

9. A method for preparing the slag-based clay curing agent according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Curing agent ingredients: weigh the raw material components of cement, slag powder, steel slag powder, recycled micro powder, phosphogypsum, and admixtures according to the weight ratio; S2, stirring: adding the raw materials weighed in step S1 into a mixer in batches, mixing and stirring thoroughly. The raw materials are mixed by dry mixing, and the dry mixing time should be no less than 2 minutes; S3, bagging: placing the powder mixed and stirred in step S2 in a sealed bag for drying and storage at room temperature to form a slag-based clay curing agent.

Images