Pavement base material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of solid waste resource utilization, and discloses a pavement base material which comprises the following components in parts by weight: 80-95 parts of harmless barium slag, 5-20 parts of a solid waste-based cementing material and 10-15 parts of externally doped water, and a preparation method of the pavement base material comprises the following steps: uniformly mixing the barium slag, desulfurized gypsum and water to obtain a mixture; drying and sieving after the materials are covered, so as to obtain harmless barium slag; and uniformly mixing the harmless barium slag, the solid waste-based cementing material and water to obtain the pavement base material. In the pavement base material disclosed by the invention, the stable cementing material is a solid waste-based cementing material, and the stabilized material is only harmless barium slag, so that resource utilization of various industrial waste residues is realized, large-scale utilization of barium slag is realized, the resource utilization rate of barium slag is improved, the tension of road engineering gravel materials is relieved, and the use amount of cement is reduced; and the related preparation process is simple and wide in applicability, and has remarkable economic and environmental benefits.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste resource utilization, and in particular to a road base material and a preparation method and application thereof. Background Art

[0002] Barium sulfate is an important chemical substance obtained from barite, which is mainly produced by the carbonization reduction method. A large amount of barium slag is generated in the production process of barium sulfate. The barium slag pollution coefficient of the carbonization reduction process is about 0.8, that is, for every ton of barium salt produced, 0.8 to 1 ton of barium slag is produced. At present, the annual emission of barium slag in my country exceeds 1 million tons, and the total accumulated stockpile has exceeded 10 million tons.

[0003] Barium slag mainly contains acid-soluble barium and water-soluble barium, with a high barium ion content and toxicity. It belongs to HW47 hazardous waste. Long-term stacking not only occupies a large amount of land, but also pollutes the environment. Especially at high temperatures, it is easy to spontaneously combust and release toxic gases. After rainwater infiltration, a large amount of yellow wastewater containing sulfide is produced, which flows into surface water and groundwater, polluting water bodies. In addition, the barium sulfide and acid-soluble barium in the waste slag also have a toxic effect on the soil. The existing technology for the comprehensive utilization of barium slag is mainly concentrated in the fields of building materials and chemical products, but the current technical process is complicated, and the actual consumption of barium slag is limited.

[0004] Therefore, how to provide a method for resource utilization of barium slag with simple technology and high consumption is an urgent problem to be solved by technicians in this field. Summary of the invention

[0005] In view of this, the present invention provides a road base material to solve the problem that the existing resource utilization method of barium slag has complex technical processes and limited actual consumption of barium slag.

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

[0007] On the one hand, the present invention provides a road base material, comprising the following components in parts by weight: 80-95 parts of harmless barium slag, 5-20 parts of solid waste-based cementitious materials, and 10-15 parts of external water.

[0008] Preferably, the solid waste-based cementitious material comprises the following components in parts by weight: 60-70 parts of slag, 20-30 parts of steel slag and 10-20 parts of desulfurized gypsum.

[0009] Preferably, the specific surface area of ​​the solid waste-based cementitious material is 450-500m 2 / kg.

[0010] Preferably, the harmless barium slag comprises the following components in parts by weight: 70-90 parts of barium slag and 10-30 parts of desulfurized gypsum.

[0011] Preferably, the particle size of the harmless barium slag is ≤4.75 mm; further preferably, the particle size of the harmless barium slag is 0.075-2.36 mm.

[0012] Preferably, the pH is 6-9.

[0013] Preferably, the toxic leaching concentration of barium ions in the harmless barium slag is less than 10 mg / L.

[0014] Preferably, the barium slag is solid waste discharged from a barium salt chemical process, and the desulfurization gypsum is solid waste produced by a desulfurization workshop.

[0015] On the other hand, the present invention also provides a method for preparing the pavement base material described in any one of the above, comprising the following steps:

[0016] (1) mixing barium slag, desulfurized gypsum and water uniformly, drying and sieving after steaming to obtain harmless barium slag;

[0017] (2) The harmless barium slag, solid waste-based cementitious material and water are mixed evenly to obtain a road base material.

[0018] Preferably, the stewing time is 20-28 hours.

[0019] Preferably, the drying temperature is 50-60° C., and the drying is performed until the moisture content is less than 2%.

[0020] Furthermore, the present invention also provides a use of the pavement base material described in any one of the above items or the pavement base material prepared by any one of the above methods in pavement materials.

[0021] The present invention provides a road base material and a preparation method thereof. Compared with the prior art, the present invention has the following beneficial effects:

[0022] In the pavement base material provided by the present invention, the only stabilized material is barium slag, which realizes large-scale utilization of barium slag, improves the resource utilization rate of barium slag, and effectively alleviates the shortage of sand and gravel in road projects; solid waste-based cementitious materials are used to replace cement as stabilizing materials, thereby reducing the amount of cement used in road projects. Since solid waste-based cementitious materials have good hydraulic properties, they are a new type of cement-like cementitious materials and can completely replace cement to produce various grades and types of concrete. The production cost of solid waste-based cementitious materials is about 50% of that of cement, which makes it have obvious economic advantages. In addition, the use of solid waste-based cementitious materials can save more than 10% of material costs, and each ton of solid waste-based cementitious materials can absorb 70%-95% of solid waste, which can reduce carbon emissions by more than 60% compared with cement.

[0023] The ecological pavement base material of the present invention can meet the requirements of medium and light traffic on expressways and first-class highways for cement-stabilized material bases in the "Technical Specifications for Highway Pavement Base Construction" (JTG / T G20-2015) after curing for 7 days, and the unconfined compressive strength can reach more than 3MPa. DETAILED DESCRIPTION

[0024] The present invention will be described below by specific examples, and it will be appreciated by those skilled in the art that the following specific examples are only for illustrative purposes, and do not limit the scope of the present invention in any way. In addition, in the following examples, unless otherwise specified, the reagents and equipment used are all commercially available. If in the following examples, specific treatment conditions and treatment methods are not clearly described, then conditions and methods known in the art can be used to process.

[0025] In one aspect of the present invention, the present invention provides a road base material, comprising the following components by weight: 80-95 parts of harmless barium slag, 5-20 parts of solid waste-based cementitious material and 10-15 parts of water.

[0026] In the pavement base material of the present invention, the only stabilized material is barium slag, which replaces natural sand and gravel, thereby achieving rapid and large-scale consumption of the barium slag, improving the resource utilization rate of the barium slag, and alleviating the shortage of sand and gravel in road engineering. In addition, solid waste-based cementitious materials are used instead of cement as stabilizing materials, thereby reducing the amount of cement used in road engineering and reducing the production cost of pavement base materials.

[0027] In some embodiments of the present invention, the solid waste-based cementitious material comprises slag, steel slag and desulfurized gypsum in a mass ratio of 60-70:20-30:10-20. Preferably, the specific surface area of ​​the solid waste-based cementitious material is 450-500m 2 / kg. The main components of the solid waste-based cementitious material are SiO2 25-30 parts, Al2O3 10-15 parts, CaO 30-40 parts, MgO 5-8 parts, SO3 0-5 parts, Fe2O3 8-12 parts, and ignition loss 3-8 parts.

[0028] The solid waste-based cementitious material in the present invention is mainly a steel slag-slag-desulfurized gypsum cementitious material system. The desulfurized gypsum can stimulate the activity of steel slag and slag. The steel slag and slag show a synergistic promotion effect when they are hydrated. The desulfurized gypsum is mainly composed of CaSO4·2H2O and a small amount of impurities. Since CaSO4 is slightly soluble in water, the soluble sulfate provided by the desulfurized gypsum can be used to fix the free barium ions in the barium slag through precipitation, and the soluble calcium ions can react with sulfides or hydroxide ions.

[0029] Among them, the main mineral phases of steel slag are RO phase (continuous solid solution formed by FeO, MgO, MnO and CaO), C2S, C3S, C4AF (calcium aluminoferrate), Fe2O3, and a small amount of Ca(OH)2, f-CaO (free calcium oxide) and f-MgO (free magnesium oxide). The divalent metal cations in steel slag are easily hydrated to make the system alkaline. These are the material basis for stimulating the formation of CSH gel in slag and tailings, and also the material basis for capturing Al2O3 and Fe2O3 in slag to form iron-containing calcium sulfonate complex salt minerals with the participation of desulfurized gypsum.

[0030] Desulfurized gypsum provides a large amount of Ca for the reaction of steel slag-slag-desulfurized gypsum cementitious material system. 2+ and SO4 2- Under this condition, the slag slowly hydrates to form CHS gel and Ca 2+ and OH - At the same time, it can quickly increase the alkalinity in the slurry. At this time, a large amount of desulfurized gypsum and alkaline environment will promote the dissociation of silicon (aluminum) oxygen tetrahedrons in the slag, dissolving part of the soluble silicon (aluminum) and Ca in the system. 2+ Hydration products such as CSH gel and hydrated calcium sulfoaluminate (AFt) are formed. As the hydration age increases, the slag continues to hydrate to generate a small amount of CSH gel and maintain the alkalinity in the slurry, making the slurry more compact as a whole and improving its water stability.

[0031] Ca in slag continuous hydration absorption system 2+ 、SO4 2- and OH - , which can further promote the hydration of steel slag and promote OH - With the continuous reaction of steel slag and the deepening of hydration degree, the needle-shaped AFt crystals of hydration product are interspersed in CSH gel, making the structure of hardened paste more compact and the compressive strength increases accordingly.

[0032] The present invention utilizes the synergistic effect of steel slag, desulfurized gypsum and blast furnace water-quenched slag to form a large number of needle-rod-shaped complex salt crystals while also forming a large number of nearly amorphous CSH gels and zeolite-like phases, and tightly wrap the needle-rod-shaped complex salt crystals, making the originally loose structure become tight, improving the density and enhancing the water stability.

[0033] The present invention uses solid waste-based cementitious materials to replace cement for the preparation of road base materials. Various indicators meet or even exceed those of cement concrete. At the same time, solid waste-based cementitious materials are mainly composed of minerals such as silicon, calcium, and aluminum, which are similar to soil geology, have lower alkalinity than cement-based materials, and have less impact on the ecological environment. They have the advantages of good curing strength and low engineering cost. They can be widely used as road base stabilization materials to make up for the shortcomings of low early strength of lime-stabilized materials, large shrinkage of cement-stabilized materials, and poor water stability of fly ash-stabilized materials.

[0034] In some embodiments of the present invention, the harmless barium slag comprises barium slag and desulfurized gypsum in a mass ratio of 70-90:10-30, wherein the barium slag is solid waste discharged from a barium salt chemical process, and the desulfurized gypsum is solid waste produced by a desulfurization workshop. The harmless barium slag of the present invention is composed of solid waste, which realizes the resource utilization of solid waste and greatly reduces production costs.

[0035] Optionally, the particle size of the harmless barium slag is ≤4.75 mm; preferably, most of the particle sizes of the harmless barium slag are 0.075-2.36 mm, with fine particles, uniform distribution and reasonable gradation.

[0036] Optionally, the pH is 6-9, for example, pH=6, pH=7, pH=8 or pH=9.

[0037] Optionally, the toxic leaching concentration of barium ions in the harmless barium slag is less than 10 mg / L.

[0038] The limitation of particle size, pH value and toxic leaching concentration of barium ions in harmless barium slag can ensure that the leaching concentration of barium ions will not exceed the standard, and the strength of the harmless barium slag as aggregate can be guaranteed within the above range.

[0039] In another aspect of the present invention, the present invention further provides a method for preparing the pavement base material as described in any one of the above, comprising the following steps:

[0040] S100. Mix barium slag, desulfurized gypsum and water in proportion, dry and sieve after steaming to obtain harmless barium slag.

[0041] In this step, the steaming time is 20-28 hours, for example, 20 hours, 22 hours, 25 hours, 28 hours, etc. The drying temperature is 50-60°C, for example, 50°C, 55°C, 60°C, etc.

[0042] S200. Weigh harmless barium slag and solid waste-based cementitious materials according to mass proportion, mix them evenly, and then conduct compaction test to measure the maximum dry density and optimum moisture content.

[0043] S300. The harmless barium slag, solid waste-based cementitious material and water are mixed evenly in proportion to obtain a road base material.

[0044] In yet another aspect of the present invention, the present invention further provides an application of the pavement base material described in any one of the above items or the pavement base material prepared by any one of the above methods in pavement materials.

[0045] Example 1

[0046] The present embodiment provides an ecological pavement base material, comprising the following components by weight: 94 parts of harmless barium slag, 6 parts of solid waste-based cementitious material, and 12.0 parts of tap water.

[0047] The composition of solid waste-based cementitious materials by weight is: 6 parts slag, 3 parts steel slag, 1 part desulfurized gypsum, with a specific surface area of ​​450m 2 / kg; the particle size of the harmless barium slag is below 4.75mm, the composition of the harmless barium slag by mass: 10 parts of barium slag, 1 part of desulfurized gypsum, the pH of the harmless barium slag is 6, and the toxic leaching concentration of barium ions is <10mg / L.

[0048] The preparation method of the above-mentioned road base material is as follows:

[0049] (1) Mix barium slag and desulfurized gypsum in proportion, add water, stir evenly, and then simmer for 20 hours, then dry at 50°C. After drying, the material is sieved to leave fine barium slag (85% of the particle size is between 0.075-4.75 mm), which is harmless barium slag;

[0050] (2) Weigh the harmless barium slag and solid waste-based cementitious materials according to the mass ratio, mix them evenly, and then conduct a compaction test to measure the maximum dry density ρ max 1.90g / cm 3 , the best moisture content MC 最佳 12.4%

[0051] (3) weighing the harmless barium slag and the solid waste-based cementitious material and mixing them uniformly to obtain a mixture, adding water to the uniformly stirred mixture, and mixing them uniformly to obtain a mixture;

[0052] (4) stirring the mixture evenly and pouring it into a mold, and demolding to obtain an ecological pavement base material;

[0053] The ecological pavement base material prepared as above is used for molding, the molded product is demoulded, and then placed in a standard curing box with a temperature of 20±1°C and a relative humidity of 95% for curing for 7d and 28d, and water curing for 1d for subsequent test.

[0054] Example 2

[0055] The present embodiment provides an ecological pavement base material, comprising the following components by weight: 92 parts of harmless barium slag, 8 parts of solid waste-based cementitious material, and 12.8 parts of external water.

[0056] The composition of solid waste-based cementitious materials by weight is: 6 parts slag, 3 parts steel slag, 1 part desulfurized gypsum, with a specific surface area of ​​460m 2 / kg; the particle size of the harmless barium slag is below 4.75mm, the composition of the harmless barium slag by mass: 10 parts of barium slag, 1 part of desulfurized gypsum, the pH of the harmless barium slag is 8, and the toxic leaching concentration of barium ions is <10mg / L.

[0057] The preparation method of the above-mentioned road base material is as follows:

[0058] (1) Mix barium slag and desulfurized gypsum in proportion, add water, stir evenly, and then stew for 22 hours, then dry at 52°C. After drying, sieve the dried material to leave fine particles of barium slag, which is harmless barium slag;

[0059] (2) Weigh the harmless barium slag and solid waste-based cementitious materials according to the mass ratio, mix them evenly, and then conduct a compaction test to measure the maximum dry density ρ max 1.92g / cm 3 , the best moisture content MC 最佳 12.8%

[0060] (3) weighing the harmless barium slag and the solid waste-based cementitious material and mixing them uniformly to obtain a mixture, adding water to the uniformly stirred mixture, and mixing them uniformly to obtain a mixture;

[0061] (4) The mixture is stirred evenly and poured into a mold, and the ecological pavement base material is obtained after demolding.

[0062] The ecological pavement base material prepared as above is used for molding, the molded product is demoulded, and then placed in a standard curing box with a temperature of 20±1°C and a relative humidity of 95% for curing for 7d and 28d, and water curing for 1d for subsequent test.

[0063] Example 3

[0064] The present embodiment provides an ecological pavement base material, comprising the following components by weight: 90 parts of harmless barium slag, 10 parts of solid waste-based cementitious material, and 13.2 parts of tap water.

[0065] Among them, the composition of solid waste-based cementitious materials by mass: 6 parts of slag, 3 parts of steel slag, 1 part of desulfurized gypsum, with a specific surface area of ​​470m 2 / kg; the particle size of the harmless barium slag is below 4.75mm, the composition of the harmless barium slag by mass: 10 parts of barium slag, 1 part of desulfurized gypsum, the pH of the harmless barium slag is 7, and the toxic leaching concentration of barium ions is <10mg / L.

[0066] The preparation method of the above-mentioned road base material is:

[0067] (1) Mix barium slag and desulfurized gypsum in proportion, add water, stir evenly, and then stew for 23.5 hours, then dry at 55°C. After drying, sieve the dried material to leave fine particles of barium slag, which is harmless barium slag;

[0068] (2) Weigh the harmless barium slag and solid waste-based cementitious materials according to the mass ratio, mix them evenly, and then conduct a compaction test to measure the maximum dry density ρ max 1.94 g / cm 3 , optimal moisture content MC 最佳 13.2%

[0069] (3) weighing the harmless barium slag and the solid waste-based cementitious material and mixing them uniformly to obtain a mixture, adding water to the uniformly stirred mixture, and mixing them uniformly to obtain a mixture;

[0070] (4) The mixture is stirred evenly and poured into a mold, and the ecological pavement base material is obtained after demolding.

[0071] The ecological pavement base material prepared as above is used for molding, the molded product is demoulded, and then placed in a standard curing box with a temperature of 20±1°C and a relative humidity of 95% for curing for 7d and 28d, and water curing for 1d for subsequent test.

[0072] Example 4

[0073] The present embodiment provides an ecological pavement base material, comprising the following components by weight: 88 parts of harmless barium slag, 12 parts of solid waste-based cementitious material, and 13.6 parts of tap water.

[0074] Among them, the composition of solid waste-based cementitious materials by mass: 6 parts of slag, 3 parts of steel slag, 1 part of desulfurized gypsum, with a specific surface area of ​​490m 2 / kg; the particle size of the harmless barium slag is below 4.75mm, the composition of the harmless barium slag by mass: 10 parts of barium slag, 1 part of desulfurized gypsum, the pH of the harmless barium slag is 9, and the toxic leaching concentration of barium ions is <10mg / L.

[0075] The preparation method of the above-mentioned road base material is as follows:

[0076] (1) Mix barium slag and desulfurized gypsum in proportion, add water, stir evenly, and then stew for 26 hours, then dry at 58°C. After drying, sieve the dried material to leave fine particles of barium slag, which is harmless barium slag;

[0077] (2) Weigh the harmless barium slag and solid waste-based cementitious materials according to the mass ratio, mix them evenly, and then conduct a compaction test to measure the maximum dry density ρ max 1.97 g / cm 3 , the best moisture content MC 最佳 13.6%

[0078] (3) weighing the harmless barium slag and the solid waste-based cementitious material and mixing them uniformly to obtain a mixture, adding water to the uniformly stirred mixture, and mixing them uniformly to obtain a mixture;

[0079] (4) The mixture is stirred evenly and poured into a mold, and the ecological pavement base material is obtained after demolding.

[0080] The ecological pavement base material prepared as above is used for molding, the molded product is demoulded, and then placed in a standard curing box with a temperature of 20±1°C and a relative humidity of 95% for curing for 7d and 28d, and water curing for 1d for subsequent test.

[0081] Example 5

[0082] The present embodiment provides an ecological pavement base material, comprising the following components by weight: 86 parts of harmless barium slag, 14 parts of solid waste-based cementitious materials, and 14 parts of tap water.

[0083] The composition of solid waste-based cementitious materials by weight is: 6 parts slag, 3 parts steel slag, 1 part desulfurized gypsum, with a specific surface area of ​​500m 2 / kg; the particle size of the harmless barium slag is below 4.75mm, the composition of the harmless barium slag by mass: 10 parts of barium slag, 1 part of desulfurized gypsum, the pH of the harmless barium slag is 8, and the toxic leaching concentration of barium ions is <10mg / L.

[0084] The preparation method of the above-mentioned road base material is as follows:

[0085] (1) Mix barium slag and desulfurized gypsum in proportion, add water, stir evenly, and then stew for 28 hours, then dry at 60°C. After drying, sieve the dried material to leave fine particles of barium slag, which is harmless barium slag;

[0086] (2) Weigh the harmless barium slag and solid waste-based cementitious materials according to the mass ratio, mix them evenly, and then conduct a compaction test to measure the maximum dry density ρ max 1.98g / cm 3 , the best moisture content MC 最佳 14%;

[0087] (3) weighing the harmless barium slag and the solid waste-based cementitious material and mixing them uniformly to obtain a mixture, adding water to the uniformly stirred mixture, and mixing them uniformly to obtain a mixture;

[0088] (4) The mixture is stirred evenly and poured into a mold, and the ecological pavement base material is obtained after demolding.

[0089] The ecological pavement base material prepared as above is used for molding, the molded product is demoulded, and then placed in a standard curing box with a temperature of 20±1°C and a relative humidity of 95% for curing for 7d and 28d, and water curing for 1d for subsequent test.

[0090] The ecological pavement base materials prepared in Examples 1-5 were used to prepare cylindrical specimens of Ø50mm×50mm using a universal press according to the unconfined compressive strength test requirements for inorganic binder stabilized materials in the "Test Procedures for Inorganic Binder Stabilized Materials for Highway Engineering" (JTGE51-2009), with at least 6 specimens in each group; after preparation, they were sealed and placed in a curing box for curing (curing temperature of 20±1°C, curing humidity of 95%), and cured for 7d and 28d (immersed in water one day in advance). After completion, the moisture on the surface of the specimens was wiped off, and the compressive strength of the specimens was tested using a pavement strength meter. The test results are shown in Table 1.

[0091] Table 1

[0092]

[0093]

[0094] As can be seen from Table 1, the pavement base material prepared by using harmless barium slag and solid waste-based cementitious materials in the present invention has good compressive strength and can reach the standards of Class II and above highways or expressways and Class I highways.

[0095] In summary, in the pavement base material of the present invention, the stabilizing material is a solid waste-based cementitious material, and the stabilized material is only harmless barium slag, which realizes the resource utilization of various industrial waste slags, and effectively takes into account the mechanical properties, durability and water stability of the obtained pavement base material; and realizes the large-scale utilization of barium slag, improves the resource utilization rate of barium slag, alleviates the shortage of sand and gravel materials in road projects, and reduces the amount of cement. The preparation process involved is simple, has a wide applicability, and has significant economic and environmental benefits.

[0096] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A road base material, characterized in that: The invention comprises the following components in parts by weight: 80-95 parts of harmless barium slag, 5-20 parts of solid waste-based gelling materials and 10-15 parts of water.

2. The pavement base material according to claim 1, characterized in that: The solid waste-based cementitious material comprises the following components in parts by weight: 60-70 parts of slag, 20-30 parts of steel slag and 10-20 parts of desulfurized gypsum.

3. The pavement base material according to claim 1, characterized in that: The specific surface area of ​​the solid waste-based cementitious material is 450-500m 2 / kg.

4. The pavement base material according to claim 1, characterized in that: The harmless barium slag comprises the following components by weight: 70-90 parts of barium slag and 10-30 parts of desulfurized gypsum.

5. The pavement base material according to claim 1, characterized in that: The particle size of the harmless barium slag is ≤4.75mm, and the pH is 6-9; The toxic leaching concentration of barium ions in the harmless barium slag is less than 10 mg / L; The particle size of the harmless barium slag is 0.075-2.36 mm.

6. The pavement base material according to claim 2 or 4, characterized in that: The barium slag is solid waste discharged from the barium salt chemical process, and the desulfurization gypsum is solid waste produced by the desulfurization workshop.

7. A method for preparing a road base material according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) mixing barium slag, desulfurized gypsum and water uniformly, drying and sieving after steaming to obtain harmless barium slag; (2) The harmless barium slag, solid waste-based cementitious material and water are mixed evenly to obtain a road base material.

8. The method for preparing a road base material according to claim 7, characterized in that: The stuffing time is 20-28h; The drying temperature is 50-60° C., and the drying is performed until the moisture content is less than 2%.

9. Use of the pavement base material according to any one of claims 1 to 6 or the pavement base material prepared by the method according to any one of claims 7 to 8 in pavement materials.

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