CN114804773A - Composite solid waste pavement base course binder and preparation method thereof - Google Patents

Abstract

The invention discloses a composite solid waste pavement base course binder and a preparation method thereof, belonging to the technical field of road engineering. The composite solid waste pavement base course binder is formed by mixing pretreated alkaline phosphogypsum powder, fly ash, slag powder and cement. According to the invention, the industrial waste phosphogypsum slurry raw material is subjected to alkaline pretreatment to obtain alkaline phosphogypsum powder, and then the alkaline phosphogypsum powder is mixed with solid waste such as fly ash and slag and cement, and the mixture is applied to a semi-rigid base material to be used as a cementing binder, so that not only is an effective utilization way of the industrial waste residue material provided, but also the resource utilization rate of the industrial waste residue material can be improved, and the problem of environmental pollution caused by stockpiling and discharging of the industrial waste residue is solved. The prepared pavement base binder can improve the strength of the pavement base, reduce the shrinkage and cracking effects of the pavement base, reduce the cement consumption, reduce the cost and achieve the purposes of recycling solid wastes and being economic and environment-friendly.

Description

Composite solid waste pavement base course binder and preparation method thereof

Technical Field

The invention relates to the technical field of road engineering materials, in particular to a composite solid waste pavement base binder and a preparation method thereof.

Background

In recent years, with the rapid development of the phosphorus compound fertilizer industry and the phosphoric acid production in China, the discharge amount of the phosphogypsum in the industrial waste residue is continuously increased. The appearance of a large amount of phosphogypsum needs reasonable treatment on the storage of the phosphogypsum, and if the phosphogypsum is not treated properly, the storage has great influence on the environment. If the phosphogypsum is piled on the land, a large amount of land is occupied, and the environment is polluted; such as when poured into the sea or into water, the soluble phosphorus contained therein will permeate into the water body, resulting in severe eutrophication of the water body. Therefore, the comprehensive utilization of the phosphogypsum is enhanced, and the improvement of the comprehensive utilization efficiency of the phosphogypsum is very important.

Blast furnace slag is a waste slag discharged from a blast furnace when smelting pig iron. After the blast furnace slag is cooled by water quenching, the blast furnace slag contains a large amount of glass bodies inside and has latent hydraulicity. The slag mainly comprises CaO and SiO ₂ 、Al ₂ O ₃ And MgO. The grinding force of the blast furnace slag is increased, the specific surface area of the blast furnace slag is increased, the superfine blast furnace slag is obtained, and the activity of the slag can be obviously improved. Some scholars have conducted some research works on preparing pavement base materials from industrial solid wastes such as phosphogypsum. However, in the existing research, one or more solid wastes are added into the existing phosphogypsum waste, and are mixed and stirred to be used as a semi-rigid base cementing material, so that the solid waste pavement base binding material which replaces a cement material can be formed to a certain extent, but the existing solid waste pavement base binding material cannot fully exert the activity of each solid waste, and has a great space for improving the unconfined compressive strength, compressive resilience modulus and cleavage strength.

Therefore, the above-mentioned conventional composite solid waste pavement base binder still has inconvenience and defects, and needs to be further improved. How to create a new composite solid waste pavement base course binder and a preparation method thereof, which adopts a pH regulator to carry out alkaline pretreatment on phosphogypsum, exerts the alkaline phosphogypsum to improve the pozzolanic activity of fly ash and slag powder, provides necessary reference for the extensive application of phosphogypsum and other solid wastes in road engineering, and becomes an object which is greatly required to be improved in the industry at present.

Disclosure of Invention

The invention aims to solve the technical problem of providing a composite solid waste pavement base course binder, which adopts a pH regulator to perform alkaline pretreatment on phosphogypsum, exerts the alkaline phosphogypsum to improve the pozzolanic activity of fly ash and slag powder, and provides necessary reference for the extensive application of the phosphogypsum and other solid wastes in road engineering.

In order to solve the technical problems, the invention provides a composite solid waste pavement base course binder which is prepared by mixing pretreated alkaline phosphogypsum powder, fly ash, slag powder and cement.

Further improved, the weight ratio of the alkaline phosphogypsum powder, the fly ash, the slag powder and the cement is as follows: 20-40 parts of alkaline phosphogypsum powder, 20-35 parts of fly ash, 20-35 parts of slag powder and 5-15 parts of cement.

Further improved, the alkaline phosphogypsum powder is pretreated by the following steps:

s1, putting the phosphogypsum slurry raw material and a pH value regulator into high-speed stirring equipment together, wherein the rotating speed is 2000-2500r/min, the stirring time is 60-90s, and the pH value of the slurry after stirring is within the range of 11-13;

wherein, the pH value of the phosphogypsum slurry raw material is less than 7, and the water content is 30-50%;

s2, drying the stirred phosphogypsum slurry obtained in the step S1 at the drying temperature of 45-60 ℃ for 24-36h, cooling to room temperature, and grinding to obtain the alkaline phosphogypsum powder with the particle size of less than 0.03 mm.

Further improved, the pH value regulator adopts one or more of potassium hydroxide, sodium hydroxide and calcium hydroxide, and the form is powder.

The further improvement is that the fly ash adopts I-grade fly ash, wherein the f-CaO content is more than 10%.

Further improvement, the slag powder adopts slag powder with the technical grade of S105.

The further improvement is that the composite solid waste pavement base course binder is mixed with stone which has light reaction with alkali aggregate or does not have alkali aggregate reaction, and is used for preparing the inorganic binder stabilizing material with compact framework.

In a further improvement, the stone is granite or limestone.

As another improvement, the present invention further provides a preparation method of the composite solid waste pavement base course binder, which comprises the following steps:

y1. putting the phosphogypsum slurry raw material and the pH value regulator into a high-speed stirring device, wherein the rotating speed is 2000 and 2500r/min, the stirring time is 60-90s, and the pH value of the slurry after stirring is within the range of 11-13;

wherein, the pH value of the phosphogypsum slurry raw material is less than 7, and the water content is 30-50%;

y2., drying the stirred phosphogypsum slurry obtained in the step Y1 at the drying temperature of 45-60 ℃ for 24-36h, cooling to room temperature, and grinding to obtain the alkaline phosphogypsum powder with the particle size of less than 0.03 mm;

y3., fully mixing the alkaline phosphogypsum powder obtained in the step Y2 with fly ash, slag powder and cement, and uniformly mixing to obtain the composite solid waste pavement base course binder.

After adopting such design, the invention has at least the following advantages:

the composite solid waste pavement base course binder is prepared by alkaline pretreatment of industrial waste phosphogypsum, mixing the industrial waste phosphogypsum with solid waste such as fly ash and slag and cement, exerting the alkaline phosphogypsum to improve the pozzolanic activity of the fly ash and slag powder, and being applied to semi-rigid base course materials to be used as a cementing binder, so that the effective utilization of the industrial waste residue phosphogypsum, blast furnace slag and fly ash can be enlarged, the resource utilization rate of the industrial waste residue is improved, the problem of environmental pollution caused by stacking and discharging the industrial waste residue is solved, and the problem of unobvious performance improvement effect of the fly ash and the slag when being applied to a road base course is solved. The composite solid waste pavement base course binder plays a role of replacing cement in a traditional semi-rigid base course as a cementing material, can improve the application proportion of phosphogypsum, fly ash and slag in the pavement base course, improve the strength of the pavement base course, reduce the shrinkage cracking effect of the pavement base course, reduce the cement consumption, reduce the cost and finally achieve the purposes of recycling solid waste, economy and environmental protection under the condition of ensuring that the pavement performance meets the requirements and no environmental pollution.

Drawings

The foregoing is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and the detailed description.

FIG. 1 is a flow chart of the process for preparing the composite solid waste pavement base binder of the present invention.

Detailed Description

The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, the present invention is not limited to the examples listed below.

Example 1

The composite solid waste pavement base course binder is prepared by mixing pretreated alkaline phosphogypsum powder, fly ash, slag powder and cement. The alkaline phosphogypsum powder is alkaline powder obtained by pretreating the existing phosphogypsum slurry raw material. Wherein, the pH value of the phosphogypsum slurry raw material is less than 7, and the water content is 30-50%. The alkaline phosphogypsum powder is obtained by adding a pH value regulator, stirring at a high speed, drying and grinding. The pH value regulator adopts one or more of potassium hydroxide, sodium hydroxide and calcium hydroxide, and is in the form of powder.

The pretreatment steps of the alkaline phosphogypsum powder in the embodiment are as follows: putting the phosphogypsum slurry raw material and the pH value regulator into high-speed stirring equipment, wherein the stirring speed is set to 2000r/min, and the stirring time is 90 seconds, so that the pH value of the stirred alkaline phosphogypsum slurry is in the range of 7-9.

And drying the obtained slurry at the drying temperature of 60 ℃ for 24h, taking out the slurry after the drying is finished, and cooling the slurry to room temperature to obtain the modified phosphogypsum. Grinding the modified phosphogypsum to obtain alkaline phosphogypsum powder with the grain size of less than 0.03 mm.

In this embodiment, the performance indexes of the alkaline phosphogypsum powder, the fly ash and the slag powder are also detected, and the measurement results are shown in tables 1, 2 and 3 below.

Table 1 performance index results for alkaline phosphogypsum powder

TABLE 2 fly ash Performance index results

TABLE 3 slag powder Performance index results

Referring to a preparation process flow chart shown in fig. 1, after the phosphogypsum slurry raw material is pretreated to obtain the alkaline phosphogypsum powder, the alkaline phosphogypsum powder is fully mixed with cement, fly ash and slag powder according to the following weight parts shown in table 4, and the mixture is uniformly dispersed to obtain the composite solid waste pavement base course binder 1.

Table 4 raw material ratio of composite solid waste pavement base binder 1 obtained in example 1

Raw materials	Parts by weight (g)
		Alkaline phosphogypsum powder (pH value 7-9)	30
Slag powder with technical grade S105	30
		Portland cement with strength grade of 42.5	5
Class I fly ash (f-Cao content is more than 10%)	35

Example 2

The difference between this embodiment and the above embodiment 1 is that the phosphogypsum pretreatment step is different, specifically:

putting the phosphogypsum slurry raw material and the pH value regulator into high-speed stirring equipment, wherein the stirring speed is set to 2000r/min, and the stirring time is 60 seconds, so that the pH value of the stirred alkaline phosphogypsum slurry is in the range of 11-13.

And drying the obtained slurry at the drying temperature of 60 ℃ for 24 hours, taking out the slurry after the drying is finished, and cooling the slurry to room temperature to obtain the modified phosphogypsum. Grinding the modified phosphogypsum to obtain alkaline phosphogypsum powder with the grain size of less than 0.03 mm.

And then, fully mixing the obtained alkaline phosphogypsum powder with cement, fly ash and slag powder according to the weight parts shown in the following table 5, and uniformly dispersing to obtain the composite solid waste pavement base course binder 2.

Table 5 raw material ratio of composite solid waste pavement base binder 2 obtained in example 2

Raw materials	Parts by weight (g)
		Alkaline phosphogypsum powder (pH value 11-13)	30
Slag powder with technical grade S105	30
		Portland cement with strength grade of 42.5	5
Class I fly ash (f-Cao content is more than 10%)	35

Example 3

The difference between this embodiment and the above embodiment 1 is that the phosphogypsum pretreatment step is different, specifically:

putting the phosphogypsum slurry raw material and the pH value regulator into high-speed stirring equipment, wherein the stirring speed is set to 2000r/min, and the stirring time is 90 seconds, so that the pH value of the stirred alkaline phosphogypsum slurry is in the range of 9-10.

And drying the obtained slurry at the drying temperature of 45 ℃ for 36h, taking out the slurry after the drying is finished, and cooling the slurry to room temperature to obtain the modified phosphogypsum. Grinding the modified phosphogypsum to obtain alkaline phosphogypsum powder with the particle size of less than 0.03 mm.

And then, fully mixing the obtained alkaline phosphogypsum powder with cement, fly ash and slag powder according to the weight parts shown in the following table 6, and uniformly dispersing to obtain the composite solid waste pavement base course binder 3.

Table 6 raw material ratio of composite solid waste pavement base binder 3 obtained in example 3

Example 4

The difference between the embodiment and the embodiment 2 is that the alkaline phosphogypsum powder, the cement, the fly ash and the slag powder are fully mixed and uniformly dispersed according to the parts by weight shown in the following table 7 to obtain the composite solid waste pavement base course binder 4.

Table 7 raw material ratio of composite solid waste pavement base binder 4 obtained in example 4

Raw materials	Parts by weight (g)
		Alkaline phosphogypsum powder (pH value 11-13)	40
Slag powder with technical grade S105	35
		Portland cement with strength grade of 42.5	5
Class I fly ash (f-Cao content is more than 10%)	20

Example 5

The difference between the embodiment and the embodiment 2 is that the alkaline phosphogypsum powder, the cement, the fly ash and the slag powder are fully mixed and uniformly dispersed according to the parts by weight shown in the following table 8, so as to obtain the composite solid waste pavement base course binder 5.

Table 8 raw material ratio of composite solid waste pavement base binder 5 obtained in example 5

Comparative example 1

The difference between the comparative example 1 and the above example 1 is that the phosphogypsum slurry raw material is directly dried and ground to prepare the phosphogypsum powder without being pretreated. And then, fully mixing the solid waste, the cement, the fly ash and the slag powder according to the weight parts in the following table 9, and uniformly dispersing to obtain the composite solid waste pavement base course binder 6.

Table 9 raw material ratio of composite solid waste pavement base binder 6 obtained in comparative example 1

Raw materials	Parts by weight (g)
		Phosphogypsum powder (pH value less than 7)	30
Slag powder with technical grade S105	30
		Portland cement with strength grade of 42.5	5
Class I fly ash (f-Cao content is more than 10%)	35

Test examples

The composite solid waste pavement base binder 1-5 obtained in examples 1 to 5 and the composite solid waste pavement base binder 6 obtained in comparative example 1 were mixed with aggregate and water, subjected to static pressure forming to prepare cylindrical test pieces of inorganic binder stabilizing materials, and portland cement having an existing strength rating of 42.5 was used as a control binder (comparative example 2) to prepare control cylindrical test pieces. And carrying out 7d and 28d unconfined compressive strength tests, compressive resilience modulus tests and splitting tests on each cylindrical test piece, and measuring unconfined compressive strength, compressive resilience modulus and splitting strength.

The manufacturing method of the concrete cylindrical test piece refers to a manufacturing method of a cylindrical test piece in JTG E51-2019 test Specification for inorganic binder stabilizing materials for highway engineering. And a plurality of test pieces are prepared for each binder, and the average value is taken as test data. The results are given in Table 10 below.

TABLE 10 test results of the performance of the test pieces of the inorganic binder stabilizing material of each example

As can be seen from the test results of table 10, the performance of the inorganic binder stabilizing material test pieces obtained in comparative example 1 and comparative example 2 is not similar to the performance of the test pieces prepared from the inorganic binder stabilizing material obtained by performing alkaline treatment on the phosphogypsum slurry raw material at the pH value in examples 1 to 5 of the present application in the aspects of unconfined compressive strength, compressive resilience modulus and cleavage strength of 7d and 28d, which indicates that the present application performs alkaline pretreatment on phosphogypsum to adjust the pH value to alkaline, so that the mechanical properties of the inorganic binder stabilizing material can be effectively improved, and the analysis reason is that the sulfate in the alkaline phosphogypsum can significantly excite the pozzolanic activity of slag powder and fly ash, and improve the performance of the fly ash and the slag powder in the road base course.

And, through the comparison of examples 1, 2 and 3, it can be seen that the unconfined compressive strength, compressive resilience modulus and cleavage strength obtained in example 2 are the largest, and the analytical reason is that when the phosphogypsum is pretreated by adding a pH regulator, and the pH value of the phosphogypsum slurry raw material is regulated to be in the range of 11-13, the mixing effect of the alkaline phosphogypsum, the fly ash, the slag and the cement is the best.

In addition, from the comparison of the comparative example 2 with other examples and the comparative example 1, it can be seen that the addition of the solid wastes such as phosphogypsum can effectively improve the hydration activity of the cement, so that the cement hydration reaction is more sufficient, and more compact hydration products can be generated compared with common cement stabilized macadam materials, so that the prepared inorganic binder has stronger cementing capacity.

The phosphogypsum is pretreated to make the PH value of the phosphogypsum alkaline, and slag powder with the technical grade of S105 is doped, so that sulfate in the phosphogypsum can obviously stimulate the activity of the slag powder and the fly ash, and cement and the fly ash in the composite solid waste pavement base course binder have the alkali excitation function on the slag powder, so that the strength of the pavement base course can be enhanced, and the shrinkage cracking effect of the pavement base course is reduced. The inorganic binder stable material prepared by the invention has higher strength and water stability, not only can achieve the effect of reducing the cement consumption, but also can realize the purposes of recycling solid wastes and being economic and environment-friendly.

The invention provides a composite solid waste pavement base course binder. The principles and embodiments of the present invention are described herein with reference to specific examples. The above description of the embodiments is only intended to facilitate the understanding of the method and core idea of the invention; also, it will be apparent to those skilled in the art that changes in the embodiments and applications illustrated herein may be made without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims. In general, nothing in this specification should be construed as limiting the invention.

Claims (10)

1. The composite solid waste pavement base course binder is characterized by being prepared by mixing pretreated alkaline phosphogypsum powder, fly ash, slag powder and cement.

2. The composite solid waste pavement base course binder of claim 1, wherein the weight ratio of the alkaline phosphogypsum powder, the fly ash, the slag powder and the cement is as follows: 20-40 parts of alkaline phosphogypsum powder, 20-35 parts of fly ash, 20-35 parts of slag powder and 5-15 parts of cement.

3. The composite solid waste pavement base course binder of claim 2, wherein the weight ratio of the alkaline phosphogypsum powder, the fly ash, the slag powder and the cement is as follows: 30 parts of alkaline phosphogypsum powder, 35 parts of fly ash, 30 parts of slag powder and 5 parts of cement.

4. The composite solid waste pavement base binder of any one of claims 1 to 3, wherein the alkaline phosphogypsum powder is pretreated by the steps of:

s1, putting the phosphogypsum slurry raw material and a pH value regulator into high-speed stirring equipment, controlling the rotating speed to be 2000-2500r/min, stirring for 60-90s, and controlling the pH value of the slurry after stirring to be within the range of 11-13;

wherein, the pH value of the phosphogypsum slurry raw material is less than 7, and the water content is 30-50%;

s2, drying the stirred phosphogypsum slurry obtained in the step S1 at the drying temperature of 45-60 ℃ for 24-36h, cooling to room temperature, and grinding to obtain the alkaline phosphogypsum powder with the particle size of less than 0.03 mm.

5. The composite solid waste pavement base binder of claim 4, wherein the pH regulator is one or more of potassium hydroxide, sodium hydroxide and calcium hydroxide in the form of powder.

6. The composite solid waste pavement base binder of claim 5, wherein the fly ash is class I fly ash, wherein the f-CaO content is greater than 10%.

7. The composite solid waste pavement base course binder of claim 6, wherein the slag powder is S105 grade slag powder.

8. The composite solid waste pavement base binder of claim 7, wherein the composite solid waste pavement base binder is mixed with stone that is less or non-reactive with alkali aggregate for making a skeletal compact inorganic binder stabilizing material.

9. The composite solid waste pavement base binder of claim 8, wherein the stone is granite or limestone.

10. The method of making the composite solid waste pavement base binder of any of claims 1 to 9, comprising the steps of:

y1. putting the phosphogypsum slurry raw material and the pH value regulator into a high-speed stirring device, controlling the rotating speed to be 2000 and 2500r/min, stirring for 60-90s, and controlling the pH value of the slurry after stirring to be within the range of 11-13;

wherein, the pH value of the phosphogypsum slurry raw material is less than 7, and the water content is 30-50%;

y2., drying the stirred phosphogypsum slurry obtained in the step Y1 at the drying temperature of 45-60 ℃ for 24-36h, cooling to room temperature, and grinding to obtain the alkaline phosphogypsum powder with the particle size of less than 0.03 mm;

y3., fully mixing the alkaline phosphogypsum powder obtained in the step Y2 with fly ash, slag powder and cement, and uniformly mixing to obtain the composite solid waste pavement base course binder.

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