CN116535153B - Lepidolite slag road water-stable mixture and preparation method thereof - Google Patents

Abstract

The invention discloses a lepidolite slag road water stabilization mixture and a preparation method thereof, and belongs to the technical field of road construction base water stabilization. The lepidolite slag road water-stable mixture comprises the following raw materials in percentage by weight: 2 to 3 percent of cement, 1.5 to 2.5 percent of slag powder, 18.5 to 25.8 percent of modified lepidolite slag, 65 to 74 percent of graded aggregate, 0.06 to 0.18 percent of excitant and 3 to 5 percent of water; the modified lepidolite slag is formed by modifying lepidolite slag through calcium nitrite and aluminum sulfate. According to the invention, the lepidolite slag is modified by utilizing the calcium nitrite and the aluminum sulfate, so that the lepidolite slag is successfully applied to the road water-stable material, waste materials are changed into valuable materials, the industrial solid waste resources of the lepidolite slag are consumed, and the resource waste and the environmental pollution are avoided. The lepidolite slag road water-stable mixture prepared by the invention has the advantages of compact structure, high strength, good stability and 7d unconfined compressive strength exceeding 5MPa.

Description

A kind of lithium mica slag road water-stabilizing mixture and preparation method thereof

Technical Field

The invention belongs to the technical field of water-stabilizing materials for road construction base layers, and in particular relates to a lepidolite slag road water-stabilizing mixture and a preparation method thereof.

Background technique

The water-stabilizing layer is a cement-stabilized gravel layer, which uses graded gravel as aggregate, a certain amount of cementitious materials and sufficient mortar volume to fill the gaps in the aggregate, and is spread and compacted according to the principle of interlocking. Its compaction is close to its density, and its strength mainly depends on the interlocking principle between the gravel, and at the same time, there is enough mortar volume to fill the gaps in the aggregate. After the water-stabilizing layer is established, it will not be muddy when it rains, which can effectively improve the water-stabilizing performance, prevent the rise of groundwater and the decline of surface water. The unconfined compressive strength in 7 days can reach 1.5-4.0 MPa, which is higher than other roadbed materials. It is an ideal base material for high-grade pavement. The water-stabilizing materials currently used in the standard are mainly cement, lime, fly ash, coal slag and other materials.

In recent years, with the rapid increase in the use of lithium-ion batteries in electronic devices and electric vehicles, the production capacity of lithium has also increased significantly. More and more lithium mines are mined for lithium extraction, and a large amount of industrial by-product lithium slag is also produced. Acid smelting with lithium mica ore as raw material produces 20 to 25 tons of lithium mica slag for every ton of lithium carbonate produced. If these lithium slags are not utilized, they will not only occupy a large amount of land, but also cause serious pollution to the environment. At present, the comprehensive utilization rate of lithium slag in my country is extremely low, and it is mainly treated by open-air stacking or deep pit landfill. The stacking of a large amount of lithium mica slag not only wastes lithium slag resources but also causes environmental pollution. The resource utilization of lithium mica slag is imminent. If lithium mica slag can be used as the main material in the road water-stabilizing layer, it can not only solve the problem of resource utilization of lithium mica slag, but also reduce the cost of highway construction.

The chemical composition of lithium mica slag is similar to that of clay. The content of _{SiO2 and Al2O3} in lithium mica slag is relatively high, mainly existing in amorphous form. It has good volcanic ash activity, micro-aggregate effect and filling effect. However, lithium mica slag also contains a small amount of soluble fluoride salts and phosphates. The precipitation of these soluble salts will affect the density of the material and reduce the strength of the material. In view of this problem, Chinese patent CN114988741A discloses a modification method of lithium mica slag: by mass fraction, 40-50 parts of water, 40-60 parts of lithium mica slag, 1-2 parts of _CaCl2 , and 2-3 parts of active quicklime are mixed and aged for 7-24 hours to obtain an aged material; the aged material is then placed in a Maffei furnace for heat treatment, heated to 700-1000°C at 3°C/min and kept warm for 60-180 minutes, and cooled at room temperature to obtain a heat-treated lithium mica slag; the heat-treated lithium mica slag is repeatedly rinsed with water, and the obtained sediment is dried at 80-105°C and crushed to obtain a modified lithium mica slag. The modification method solidifies the soluble fluoride ions in the lithium mica slag into _CaF2 in advance by adding _CaCl2 and active quicklime, thereby eliminating its influence on the setting time of cement. However, calcium chloride solution is acidic and needs to be used with active quicklime to turn the solution into alkaline, making it easier for phosphates and fluorides to solidify. In addition, in the cement binder system, chloride ions are harmful components, so try to avoid introducing chloride salts when using them.

Summary of the invention

In view of the deficiencies in the above prior art, the purpose of the present invention is to provide a lithium mica slag road water-stabilizing mixture, eliminate the adverse effects of soluble fluoride salts and phosphates in the lithium mica slag, and successfully apply the lithium mica slag to road water-stabilizing materials. The lithium mica slag road water-stabilizing mixture has a compact structure, high strength and good stability.

In order to achieve the above purpose, the technical solution is as follows:

A lithium mica slag road water-stabilizing mixture comprises the following raw materials in percentage by weight: 2-3% cement, 1.5-2.5% blast furnace granulated slag powder, 18.5-25.8% modified lithium mica slag, 65-74% graded aggregate, 0.06-0.18% activator and 3-5% water.

The modified lepidolite slag is prepared by modifying the lepidolite slag with calcium nitrite and aluminum sulfate.

The mineral phase particles of lithium mica slag are sub-nanoscale and have high adsorption. They can fill smaller pores in water-stabilized mixtures. The excellent filling effect enables the water-stabilized mixture to obtain better density during rolling and increase the strength of the water-stabilized layer. As an industrial waste residue, lithium mica slag can replace stone powder in water-stabilized materials. Compared with inert ore materials, lithium mica slag treated at high temperature contains a large amount of amorphous silicon dioxide and aluminum oxide, and has good volcanic ash activity. The lithium mica slag also contains some soluble sulfates, which can react with the high-aluminum and high-calcium glass in the slag powder to form hydrated calcium sulfoaluminate and C-S-H gel; at the same time, the active aluminum components in the lithium mica slag are excited in the saturated calcium hydroxide solution of cement hydration, and can also react with sulfates. The hydrated calcium sulfoaluminate generated by the reaction can fill the pores, making the structure more compact and increasing the strength of the water-stabilized material.

With respect to the soluble fluoride salts and phosphates in the lithium mica slag, the present invention modifies them by adding calcium nitrite and aluminum sulfate, so that the fluoride salts and phosphates react with calcium nitrite in advance to generate insoluble calcium fluoride and calcium phosphate. On the one hand, aluminum sulfate can form a flocculant to quickly precipitate calcium fluoride and calcium phosphate, promote the reaction of calcium nitrite with soluble salts, and accelerate the solidification of soluble salts in the lithium mica slag; on the other hand, the hydrolyzed aluminum ions can also react with soluble phosphates and fluoride salts to solidify the soluble phosphates and fluoride salts. Calcium nitrite dissolves in water to make the solution alkaline. In an alkaline environment, the solidification of phosphates and fluoride salts is easier to carry out. Under the joint action of calcium nitrite and aluminum sulfate, the precipitation of soluble salts in the lithium slag in the water-stable mixture can be prevented, and the dissolution of soluble salts after the water-stable mixture is solidified and meets water can be avoided, thereby increasing the stability of the water-stable mixture after solidification.

Preferably, the amounts of calcium nitrite and aluminum sulfate are 0.5-0.8% and 0.2-0.5% of the mass of the lithium mica slag.

Preferably, the lepidolite slag is waste residue produced by extracting lithium carbonate from lepidolite ore, and the moisture content of the lepidolite slag waste residue is 20% to 25%.

Preferably, the modified lithium mica slag is prepared by the following preparation method:

S1. Mix the lithium mica slag and water in a ratio of 1:1, then add calcium nitrite and aluminum sulfate, and stir at room temperature for 1 to 1.5 hours to obtain a modified lithium mica slag slurry;

S2. The modified lithium mica residue slurry obtained in step S1 is subjected to filter pressing, and the moisture content of the filter residue is controlled at 18 to 25%;

S3. putting the lepidolite residue obtained in step S2 into a rotary kiln for baking, wherein the temperature in the rotary kiln is controlled at 500° C. to 650° C., and the moisture content of the lepidolite residue after baking is controlled at 5% to 8%.

Baking the lithium mica slag at a high temperature of 500℃ to 650℃ can accelerate the reaction between soluble salts and calcium nitrite. On the other hand, some high-temperature unstable fluorides and sulfides in the lithium slag decompose at high temperatures, making the performance of the lithium slag more stable and increasing the volcanic ash activity of the lithium slag. Baking the lithium mica slag to 5% to 8% is conducive to the production of water-stabilized mixtures, avoiding excessive moisture in the lithium mica slag causing it to stick to the inside of the equipment and increase the equipment load; it also avoids the water in the lithium mica slag being squeezed out under high pressure during the rolling process of the water-stabilized mixture, taking away part of the bonding slurry and forming capillary channels.

More preferably, the temperature in the rotary kiln in step S3 is 600-650°C.

Preferably, the cement is ordinary silicate P·O42.5 cement or slag silicate P·S42.5 cement.

Preferably, the performance index of the slag powder is not lower than the S95 grade requirement.

Preferably, the graded aggregate includes at least one of limestone, granite and basalt; the graded aggregate includes two particle sizes of 5 mm to 15 mm and 15 mm to 31.5 mm.

Preferably, the activator is potassium thiocyanate and polymer aluminum.

When cement is hydrated, calcium hydroxide will precipitate, but the solubility of calcium hydroxide is very low. When potassium thiocyanate is added to the water-stabilized mixture, the potassium ions in potassium thiocyanate will replace part of the calcium due to the different ion potentials, which increases the OH ^- ion concentration in the liquid phase. The increase of OH ^- ions in the solution will accelerate the reaction between the active aluminum oxide in the lithium slag and the gypsum in the lithium slag, which is beneficial to the crystallization of ettringite and promotes the formation of ettringite, a hydration product. The accelerated formation of ettringite improves the early strength of the cementitious system. As a good concrete cohesive material, high molecular weight polyaluminum can make the combination of hydration products more compact and further increase the density of the water-stabilized mixture.

Preferably, the mass ratio of potassium thiocyanate to high molecular weight polymer aluminum in the activator is 1:(2-3).

Preferably, the method for preparing the lepidolite slag road water-stabilizing mixture comprises the following steps:

P1. Weigh the activator in proportion and add it to water, stirring to form a solution;

P2. Take the graded aggregate and modified lepidolite slag and mix them, stir them evenly, then add the cement and slag powder, spray the solution obtained in step P1 while stirring, and after all the materials are mixed evenly, the lepidolite slag road water-stabilizing mixture can be obtained.

Compared with the prior art, the present invention is beneficial in that:

1. The present invention utilizes calcium nitrite and aluminum sulfate to modify lithium mica slag, and successfully prepares a road water-stabilizing material with a compact structure, high strength, good stability, and a 7d unconfined compressive strength exceeding 5MPa.

2. The present invention applies lithium mica slag to road water-stabilizing materials, turning waste into treasure, reducing the consumption of natural stone powder and other resources, while consuming the lithium mica slag industrial solid waste resources, avoiding resource waste and environmental pollution.

3. The preparation method of the present invention is simple and only requires operations such as mixing and stirring, and requires less equipment and operations, which is conducive to mass production.

Detailed ways

The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

It should be noted that the methods described in the following embodiments are all conventional methods, and the reagents and materials, unless otherwise specified, can be obtained from commercial sources.

The slag powder in each embodiment is of S95 grade, and the 28d activity index is 98%.

The graded aggregate is natural aggregate, and the aggregate material is granite; among them, the grading range of 5mm~15mm particle size aggregate is below 9.5mm accounting for 50.7%, 9.5mm~13.2mm accounting for 40.5%, and above 13.2mm accounting for 8.8%; the grading range of 15mm~31.5mm particle size aggregate is 15mm~19mm accounting for 4.7%, 19mm~26.5mm accounting for 48.5%, and the part above 26.5mm accounts for 46.8%.

Example 1

The present embodiment provides a lithium mica slag road water-stabilizing mixture, which is made of the following raw materials in percentage by weight: 2% cement, 2.5% blast furnace granulated slag powder, 25% modified lithium mica slag, 30% aggregate with a particle size of 5mm to 15mm, 37% aggregate with a particle size of 15mm to 31.5mm, 0.06% activator, and 3.44% water.

The modified lithium mica slag preparation method is:

S1. The lithium mica slag and water were mixed in a ratio of 1:1, 0.6% calcium nitrite and 0.4% aluminum sulfate of the lithium mica slag were added, and stirred at room temperature for 1h to obtain a modified lithium mica slag slurry;

S2. The modified lithium mica slag slurry obtained in step S1 was filtered under a pressure of 0.5MPa, and the moisture content of the filter residue was controlled at 20%;

S3: placing the lepidolite residue obtained in step S2 into a rotary kiln for baking, wherein the temperature in the rotary kiln is controlled at 650° C. and the baking is performed for 1.5 hours. After baking, the moisture content of the modified lepidolite residue is 6.5%.

The preparation method of the lithium mica slag road water-stabilizing mixture is:

P1. Weigh potassium thiocyanate and polymer aluminum in proportion, add to water, and stir evenly to form a solution;

P2. Weigh the graded aggregate and modified lepidolite slag in proportion and mix them. After stirring evenly, add cement and slag powder, spray the solution obtained in step P1 while stirring. After all the materials are mixed evenly, a lepidolite slag road water-stabilizing mixture can be obtained.

The mass ratio of potassium thiocyanate to high molecular weight polymer aluminum in the activator is 1:2.2; the cement is P·O42.5 cement, and the 3d and 28d compressive strengths of the cement are 21.5MPa and 49.3MPa respectively.

Example 2

The lithium mica slag road water-stabilizing mixture provided in this embodiment is basically the same as that in Example 1, except that it is made of the following raw materials in weight percentage: 2.5% cement, 2% blast furnace granulated slag powder, 22% modified lithium mica slag, 30.7% aggregate with a particle size of 5mm to 15mm, 38% aggregate with a particle size of 15mm to 31.5mm, 0.18% activator, and 4.62% water.

The calcium nitrite and aluminum sulfate account for 0.5% and 0.3% of the mass of the lepidolite slag respectively; the mass ratio of potassium thiocyanate and high molecular weight polymer aluminum in the activator is 1:2.5.

Example 3

The lithium mica slag road water-stabilizing mixture provided in this embodiment is basically the same as that in Example 1, except that it is made of the following raw materials in the following weight ratio: 3% cement, 1.5% blast furnace granulated slag powder, 20% modified lithium mica slag, 33% aggregate with a particle size of 5mm to 15mm, 38.5% aggregate with a particle size of 15mm to 31.5mm, 0.16% activator, and 3.84% water.

The calcium nitrite and aluminum sulfate account for 0.8% and 0.5% of the mass of the lepidolite slag respectively; the mass ratio of potassium thiocyanate and high molecular weight polymer aluminum in the activator is 1:2.

Example 4

The lithium mica slag road water-stabilizing mixture provided in this embodiment is basically the same as that in Example 1, except that it is made of the following raw materials in the following weight ratio: 3% cement, 2% blast furnace granulated slag powder, 18% modified lithium mica slag, 33% aggregate with a particle size of 5mm to 15mm, 39% aggregate with a particle size of 15mm to 31.5mm, 0.12% activator, and 4.88% water.

The calcium nitrite and aluminum sulfate account for 0.7% and 0.2% of the mass of the lepidolite slag respectively; the mass ratio of the potassium thiocyanate to the high molecular weight polymer aluminum is 1:2.2.

The cement is P·S42.5 cement, and the 3d and 28d compressive strengths of the cement are 20.3MPa and 48.9MPa respectively.

Comparative Example 1

The lepidolite slag road water-stabilizing mixture provided in this comparative example is basically the same as that in Example 1, except that the lepidolite slag is not modified, that is, an equal amount of lepidolite slag is used instead of the modified lepidolite slag.

Comparative Example 2

The lithium mica slag road water-stabilizing mixture provided in this comparative example is basically the same as that in Example 1, except that an equal amount of calcium chloride is used instead of calcium nitrite.

Comparative Example 3

The lithium mica slag road water-stabilizing mixture provided in this comparative example is basically the same as that in Example 1, except that an equal amount of sodium hydroxide is used instead of the activator.

Application Example 1

The lepidolite slag road water-stabilized mixture obtained in Examples 1-4 and Comparative Examples 1-3 was tested for its 7d, 28d unconfined compressive strength and 7d splitting strength according to the "Test Procedure for Stabilized Materials of Inorganic Binders for Highway Engineering" (JTGE51-2009). The test results are shown in Table 1:

Table 1: Test results of unconfined compressive strength and splitting strength

It can be seen from the data in Table 1 that the lithium mica slag road water-stabilizing mixture prepared in Examples 1 to 4 has excellent 7d, 28d unconfined compressive strength and 7d splitting strength, indicating that the lithium mica slag road water-stabilizing mixture of the present invention has a compact structure and good stability. The 7d unconfined compressive strength of the mixture prepared in each embodiment exceeds 5MPa, meeting the 7d-age unconfined compressive strength requirements of the base cement stabilized material specified in the "Technical Specifications for Highway Pavement Base Construction" JTG/T F20-2015. The present invention uses calcium nitrite and aluminum sulfate to modify lithium mica slag, successfully applies lithium mica slag to road water-stabilizing materials, turns waste into treasure, consumes the resources of lithium mica slag industrial solid waste, avoids resource waste and environmental pollution, and greatly reduces production costs.

The unconfined compressive strength and splitting strength of Example 1 are relatively low mainly because the amount of cement used in the raw materials of Example 1 is slightly less, and the void filling rate between the graded aggregates is not as good as that of other examples, so the strength is relatively low.

Comparing Comparative Example 1 with Example 1, the 7d unconfined compressive strength and splitting strength of the road water-stabilized mixture prepared by using unmodified lepidolite slag are significantly reduced. This is because the soluble fluoride salts and phosphates in the lepidolite slag precipitate after the water-stabilized mixture is solidified, which reduces the compactness of the road water-stabilized mixture and makes the mixture more easily damaged by external forces.

Comparing Comparative Example 2 with Example 1, after calcium chloride was used instead of calcium nitrite, the 7d unconfined compressive strength and splitting strength of the road water-stabilized mixture also decreased significantly. Although calcium chloride can also react with fluoride salts and phosphates, calcium chloride is acidic when dissolved in water, and phosphates and fluoride salts are not easy to react to form precipitation under acidic conditions, thus resulting in poor performance of the mixture.

Comparing Comparative Example 3 and Example 1, the 7d unconfined compressive strength and splitting strength of the road water-stabilized mixture prepared using sodium hydroxide as an activator are similar to those of Example 1, but the 28d unconfined compressive strength is significantly reduced. This is because the addition of sodium hydroxide can increase the OH- ions in the system in the early stage, promote the formation of the hydration product calcium aluminate, and improve the strength of the material. However, sodium hydroxide will also react with calcium silicate to form soluble sodium silicate. As sodium silicate is continuously dissolved, the pores in the gelling system increase, resulting in a significant decrease in the 28d unconfined compressive strength.

The above specific embodiments describe the implementation of the present invention in detail, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the claims and technical concept of the present invention, the technical solution of the present invention can be modified and changed in many simple ways, and these simple modifications all belong to the protection scope of the present invention.

Claims (6)

1. A lithium mica slag road water-stabilizing mixture, characterized in that it comprises the following raw materials in weight percentage: 2-3% cement, 1.5-2.5% slag powder, 18.5-25.8% modified lithium mica slag, 65-74% graded aggregate, 0.06-0.18% activator, and 3-5% water; The modified lithium mica slag is prepared by the following preparation method: S1. The lithium mica slag is mixed with water, and then calcium nitrite and aluminum sulfate are added, and stirred at room temperature for 1 to 1.5 hours to obtain a modified lithium mica slag slurry; wherein the amount of calcium nitrite and aluminum sulfate is 0.5 to 0.8% and 0.2 to 0.5% of the mass of the lithium mica slag, respectively; S2. The modified lithium mica residue slurry obtained in step S1 is subjected to filter pressing, and the moisture content of the filter residue is controlled at 18 to 25%; S3. Put the modified lepidolite residue obtained in step S2 into a rotary kiln for baking, the temperature in the rotary kiln is controlled at 500° C. to 650° C., and the moisture content of the lepidolite residue after baking is controlled at 5% to 8%. 2. Lepidolite slag road water-stabilizing mixture according to claim 1, is characterized in that the cement is ordinary silicate P·O42.5 cement or slag silicate P·S42.5 cement. 3. The lithium mica slag road water-stabilizing mixture according to claim 1 is characterized in that the graded aggregate includes at least one of limestone, granite, and basalt; the graded aggregate includes two particle sizes of 5mm to 15mm and 15mm to 31.5mm. 4. Lepidolite slag road water-stabilizing mixture according to claim 1, is characterized in that the activator is potassium thiocyanate and macromolecular polymer aluminum. 5. The lepidolite slag road water-stabilizing mixture according to claim 4, characterized in that the mass ratio of potassium thiocyanate to high molecular polymer aluminum in the activator is 1:(2-3). 6. The method for preparing the lithium mica slag road water-stabilizing mixture according to any one of claims 1 to 5, characterized in that it comprises the following steps: P1. Weigh the activator in proportion and add it to water, stirring to form a solution; P2. Take the graded aggregate and modified lepidolite slag and mix them, stir them evenly, then add the cement and slag powder, spray the solution obtained in step P1 while stirring, and after all the materials are mixed evenly, the lepidolite slag road water-stabilizing mixture can be obtained.