CN112897915B

CN112897915B - Preparation method of high-alumina fly ash chloride ion combined ceramic sand with core-shell structure

Info

Publication number: CN112897915B
Application number: CN202110131760.6A
Authority: CN
Inventors: 严建华; 罗占勇; 孙大伟; 崔素萍; 唐鑫科
Original assignee: Beijing University of Technology
Current assignee: Beijing University of Technology
Priority date: 2021-01-30
Filing date: 2021-01-30
Publication date: 2022-06-24
Anticipated expiration: 2041-01-30
Also published as: CN112897915A

Abstract

A preparation method of high-alumina fly ash chloride ion combined ceramic sand with a core-shell structure belongs to the technical field of concrete materials. The ceramic sand is divided into a core and a shell; the core comprises the following components in percentage by mass: 25-35 wt% of fly ash and 65-75 wt% of carbide slag; the shell layer comprises the following components in percentage by weight: 35-41 wt% of red mud, 31-34 wt% of fly ash, 10-13 wt% of clay and 15-25 wt% of quartz powder; mixing the raw materials with water in a balling disk to prepare core-shell ceramic sand with the core diameter of 2.5-3mm and the overall external diameter of 5-6 mm; drying the core-shell ceramic sand, and then putting the core-shell ceramic sand into a high-temperature furnace for sintering; the sintering system is as follows: heating to 200 deg.C from room temperature, holding at 200 deg.C for 2h, heating to 1200 deg.C from 200 deg.C, holding at 1200 deg.C for 30min, and furnace cooling. The chloride ion binding amount of the chloride ion-bound ceramsite is 22.9-25 mg/g. The pottery sand is used for preparing concrete, the problem of reinforcement corrosion caused by chloride ions in the concrete can be solved, and the durability of the reinforced concrete is prolonged.

Description

Preparation method of high-alumina fly ash chloride ion combined ceramic sand with core-shell structure

The technical field is as follows:

the invention belongs to the technical field of concrete materials, solves the problem of stability of concrete in a chloride ion binding age period, and relates to a preparation technology of concrete artificial aggregate.

Background art:

according to various publications, chloride ions are one of the important causes of corrosion of reinforced concrete reinforcements. The hydration product of the concrete cementing material has the functions of reducing the diffusion coefficient of concrete chloride ions and reducing the concentration of the chloride ions around the reinforcing steel bars in the combination of the chloride ions in the concrete, and has the functions of delaying the corrosion of the reinforcing steel bars and protecting the reinforced concrete from the aspect of effect. There are two main mechanisms for binding chloride ions by concrete cement hydration products-physical binding and chemical binding. The physical binding capacity is in direct correlation with C-S-H gel content and Ca/Si, while the chemical binding and AFm are associated with chloride ion binding to form F salt. The results reported in the existing documents show that the chloride ion combination of the concrete is mainly related to the formation of F salt, so that the raw material with higher content of activated alumina is adopted to be doped into the concrete gelling system to promote the chloride ion combination of the concrete. However, from the literature and the research results of the applicant, the measures only increase the effect of concrete chloride ion combination in a shorter age, such as 28d and 56d, no matter what kind of admixture is added to the concrete, and the chloride ion combination amount of the concrete decreases with the increase of the age. The reason for this is that extended age results in consumption of calcium hydroxide in the concrete cement hydrate, lowering the Ca/Si of the concrete hydrate C-S-H and resulting in a decrease in pH which promotes decomposition of the F salt. Therefore, the concrete cementing material has higher specific gravity of calcium hydroxide, namely, the higher ratio of Ca/Si and Ca/Al is beneficial to maintaining better chloride ion binding capacity. However, the addition of a large amount of calcium hydroxide as an engineering material has an effect of lowering the strength of concrete.

In order to solve the contradiction, the applicant proposes a core-shell structure fine aggregate structure for isolating a system with high chloride ion binding capacity from cement slurry, and the core-shell structure fine aggregate structure is basically characterized in that a chloride ion binding system with high active calcium oxide content is wrapped by a porous fired shell structure, aiming at improving the chloride ion binding capacity of concrete and maintaining the chloride ion binding capacity of long-term concrete. On one hand, the structure can keep the combination state stable for a long time by absorbing chloride ions in concrete through the porous structure, and on the other hand, the aggregate shell structure can provide better strength support for the concrete.

The invention is characterized in that high alumina content in the high-alumina fly ash is utilized and is matched with calcium carbide slag mainly composed of calcium hydroxide to prepare a fine aggregate core part, then the fly ash, red mud, clay and quartz powder are prepared into mixed powder to wrap the core, and the core-shell structure chloride ion combined fine aggregate is formed by high-temperature firing. Due to the use of a large amount of solid waste in the formula, the solid waste is not typical of recycling.

Disclosure of Invention

Based on the above, the invention provides a process measure that the chloride ion binding hydration product is independent of the cement slurry, and the essential characteristic of the process measure is that the chloride ion binding hydration product formed by the reaction of the raw material with high protective activity alumina and calcium hydroxide can stably exist for a long time independent of the cement slurry.

The basic technical characteristics are as follows: a high-alumina fly ash chloride ion combined ceramic sand with a core-shell structure is divided into a core and a shell. The core part is a functional composition, can be hydrated automatically when meeting water to form a product with chloride ion binding capacity, and the shell part mainly plays a role in isolating the chloride ion binding functional hydration product of the core part from cement paste in which the shell part is positioned. The raw materials of each part are as follows:

the core-core mixture comprises the following components in percentage by weight: 25-35 wt% of fly ash and 65-75 wt% of carbide slag, wherein the sum of the use amount of the components is 100%.

The shell layer mixture comprises the following components in percentage by weight: 35-41 wt% of red mud, 31-34 wt% of fly ash, 10-13 wt% of clay and 15-25 wt% of quartz powder, wherein the sum of the use amount of each component is 100%.

The method comprises the following steps:

1) grinding the fly ash and the carbide slag, sieving the ground powder by a 200-mesh sieve, and uniformly mixing the following components in percentage by weight:

25-35 wt% of fly ash

65-75 wt% of carbide slag

The sum of the dosage of the components is 100 percent.

2) Grinding red mud, fly ash, clay and quartz powder, sieving with a 200-mesh sieve, and uniformly mixing the following components in percentage by weight:

the sum of the dosage of the components is 100 percent.

3) Putting the uniformly mixed powder obtained in the step 1) into a balling disk, atomizing deionized water by an atomizer, adding the atomized deionized water into the balling disk to ball the powder, and controlling the diameter of the ball formed by the core material to be 2.5-3 mm.

4) Sieving the core material balls prepared in the step 3), and selecting the core material balls with the diameter of 2.5-3mm for later use

5) Continuously adding the core material balls prepared in the step 4) into a ball forming disc, atomizing deionized water through an atomizer, and alternately adding the deionized water and the shell material powder obtained in the step 2 into the ball forming disc. The diameter of the ball is controlled to be 5-6 mm.

6) Sieving the material balls prepared in the step 5) and selecting the material balls with the diameter of 5-6mm for later use.

7) Putting the pellets obtained in the step 6) into a drying oven at 105 ℃ for drying for 3 hours, and taking out the drying oven.

8) Putting the pellets obtained in the step 7) into a sintering furnace, and sintering by the following procedure to form ceramic sand.

A preheating stage: heating from room temperature to 200 ℃ at a heating rate of 5-10 ℃/min, and staying at 200 ℃ for 1-2 hours.

A temperature rising stage: and (3) raising the furnace temperature from 200 ℃ to 1150-1200 ℃ at a temperature raising speed of 5-20 ℃/min, and preserving the temperature for 20-30 min.

And (3) cooling: naturally cooling to room temperature along with the furnace temperature, and taking out to obtain the chloride ion combined ceramic sand.

10 g of pottery sand is soaked in 100mL of 0.5mol/L chloride ion solution for seven days to determine the chloride ion binding performance of the pottery sand. The chloride ion binding amount of the chloride ion-bound ceramsite is 22.9-25 mg/g.

In the step 1) and the step 2), Al in the fly ash₂O₃The percentage content is higher than 30 percent.

Compared with the prior art, the invention has the following advantages: the invention provides a method for preparing chloride ion-combined ceramic sand by recycling wastes, realizes resource utilization of solid wastes such as fly ash, carbide slag and red mud, and provides a new application idea for the solid wastes. Particularly, the ceramic sand core part manufactured by the invention has stronger chloride ion binding performance, and the shell part has better strength and lower density, so that chloride ions in the environment can be easily adsorbed and enter the interior of the shell part through the shell layer to be bound and fixed. The pottery sand produced by the method can be widely applied to the fields of building, bridges, sea sand resource utilization and the like due to the performance of the pottery sand.

Description of the drawings:

FIG. 1 is a flow chart of ceramsite preparation.

FIG. 2 is a schematic diagram of a ceramsite structure.

Detailed Description

To further illustrate the technical means and effects of the present invention adopted for the predetermined purpose, the present invention will be further described in detail with reference to the following embodiments and drawings, but the present invention is not limited thereto. The mixing ratios of the materials used in the examples are shown in Table 1

Table 1 shows the mixing ratios of the materials used in the examples

Example 1:

the mix proportion data in this example are shown in table 1 above. The results of the pottery sand performance test are shown in table 2, the pottery sand structure is schematically shown in fig. 2. now, the technological process of the core-shell structure high-alumina fly ash chloride ion combined pottery sand disclosed by the invention is illustrated in the flow chart 1 by combining the pottery sand preparation technology, and the technological process comprises the following steps:

the mixture of the ceramic sand core comprises the following components in percentage by weight: 26 wt% of fly ash and 74 wt% of carbide slag, wherein the sum of the usage of the components is 100%.

The mixture proportion of the ceramic sand shell layer mixture is as follows: 39.7 wt% of red mud, 33.1 wt% of fly ash, 10.7 wt% of clay and 16.5 wt% of quartz powder, wherein the sum of the use amount of the components is 100%.

1) Respectively grinding the fly ash and the carbide slag, sieving the ground fly ash and the carbide slag by a sieve of 200 meshes, taking 56g of fly ash and 144g of carbide slag, and fully and uniformly mixing the fly ash and the carbide slag in a mixer to be used as core materials for standby.

2) Grinding red mud, quartz powder, clay and fly ash respectively, sieving with a 200-mesh sieve, taking 1200 g of red mud, 1000 g of fly ash, 324 g of clay and 500 g of quartz powder, and putting the mixture into a mixer to be fully and uniformly mixed to be used as a shell material for standby.

3) Placing the core material mixture in a balling disk, intermittently adding deionized water into the balling disk by atomizing with an atomizer, and controlling the core material to be balling.

4) Sieving the prepared core material ball, and taking the core material ball with the diameter interval of 2.5-3 mm.

5) Taking core material balls with the diameter range of 2.5-3mm, continuously putting the core material balls into a ball forming disc, and alternately adding deionized water and shell material into the ball forming disc by atomization of an atomizer to form the core-shell structure material balls.

6) Sieving the obtained core-shell structure material balls to select the material balls with the diameter of 5-6 mm.

7) Selecting pellets with the diameter of 5-6mm, and putting the pellets into a drying oven at 105 ℃ for drying for 3 hours.

8) And putting the dried pellets into a sintering furnace to be sintered according to the following procedure.

A preheating stage: the temperature was raised from room temperature to 200 ℃ at a heating rate of 10 ℃/min and left at 200 ℃ for 2 hours.

A temperature rising stage: and (3) keeping the temperature for 30min under the condition that the furnace temperature is increased from 200 ℃ to 1200 ℃ at the temperature increasing speed of 10 ℃/min.

And (3) cooling: and naturally cooling to room temperature along with the furnace temperature.

And taking the cooled ceramic sand out of the sintering furnace to obtain the chloride ion combined ceramic sand.

The water absorption and bulk density of the ceramic sand were measured by the method specified in GB/T1743.1-2010 "lightweight aggregate and test method thereof", and the results are shown in table 2.

10 g of pottery sand is soaked in 100mL of 0.5mol/L chloride ion solution for seven days to determine the chloride ion binding performance of the pottery sand, and the results are shown in Table 2.

Example 2:

the mixture of the ceramic sand core comprises the following components in percentage by weight: 30 wt% of fly ash and 70 wt% of carbide slag, wherein the sum of the use amount of each component is 100%.

The mixture proportion of the ceramic sand shell layer mixture is as follows: 39.7 wt% of red mud, 33.1 wt% of fly ash, 10.7 wt% of clay and 16.5 wt% of quartz powder, wherein the sum of the use amount of each component is 100%.

1) The fly ash and the carbide slag are respectively ground and sieved by a 200-mesh sieve, 60g of fly ash and 140g of carbide slag are taken and put into a mixer to be fully and uniformly mixed to be used as core materials for standby.

2) The red mud, the quartz powder, the clay and the fly ash are respectively ground and sieved by a 200-mesh sieve, 1200 g of red mud, 1000 g of fly ash, 324 g of clay and 500 g of quartz powder are taken and put into a mixer to be fully and uniformly mixed to be used as a shell material for standby.

3) Taking the core material mixture, placing the core material mixture in a balling disc, intermittently adding deionized water into the balling disc by atomization of an atomizer, and controlling the core material to be balling for later use.

4) Sieving the prepared core material ball, and taking the core material ball with the diameter interval of 2.5-3mm for later use.

5) Taking core material balls with the diameter range of 2.5-3mm, continuously putting the core material balls into a balling disk, and alternately adding deionized water and shell materials into the balling disk by atomization of an atomizer to form the core-shell structure material balls.

6) Sieving the obtained core-shell structure pellets to select pellets with the diameter of 5-6 mm.

8) And (4) placing the dried pellets into a sintering furnace and sintering according to the following procedure.

A preheating stage: the temperature was raised from room temperature to 200 ℃ at a heating rate of 10 ℃/min and left at 200 ℃ for 1 hour.

A temperature rising stage: and (4) keeping the temperature for 25min under the condition that the furnace temperature is increased from 200 ℃ to 1150 ℃ at the temperature increasing speed of 10 ℃/min.

10 g of ceramic sand is soaked in 100mL of 0.5mol/L chloride ion solution for seven days to measure the chloride ion binding performance of the ceramic sand, and the results are shown in Table 2.

Example 3:

the mixture of the ceramic sand core comprises the following components in percentage by weight: 27.5 wt% of fly ash and 72.5 wt% of carbide slag, wherein the sum of the usage amount of the components is 100%.

The mixture proportion of the ceramic sand shell layer mixture is as follows: 35.09 wt% of red mud, 31.58 wt% of fly ash, 12.28 wt% of clay and 21.05 wt% of quartz powder, wherein the sum of the use amount of the components is 100%.

1) The fly ash and the carbide slag are respectively ground and sieved by a 200-mesh sieve, 55g of fly ash and 145g of carbide slag are taken and put into a mixer to be fully and uniformly mixed to be used as core materials for standby.

2) The red mud, the quartz powder, the clay and the fly ash are respectively ground and sieved by a 200-mesh sieve, 1000 g of red mud, 900 g of fly ash, 350 g of clay and 600 g of quartz powder are taken and put into a mixer to be fully and uniformly mixed to be used as a shell material for standby.

3) Placing the core material mixture in a balling disk, intermittently adding deionized water into the balling disk by atomizing with an atomizer, and controlling the core material to be balled for later use.

Table 2 table of pottery sand performance test results

Claims

1. A preparation method of high-alumina fly ash chloride ion combined ceramic sand with a core-shell structure comprises the following steps of dividing the ceramic sand into a core and a shell; the method is characterized in that:

the core-core mixture comprises the following components in percentage by weight: 25-35 wt% of fly ash and 65-75 wt% of carbide slag, wherein the sum of the use amount of each component is 100%;

the shell layer mixture comprises the following components in percentage by weight: 35-41 wt% of red mud, 31-34 wt% of fly ash, 10-13 wt% of clay and 15-25 wt% of quartz powder, wherein the sum of the use amount of the components is 100%;

the method comprises the following steps:

25-35 wt% of fly ash

65-75 wt% of carbide slag

The sum of the using amount of the components is 100 percent;

35-41 wt% of red mud

31-34 wt% of fly ash

10-13 wt% of clay

15-25 wt% of quartz powder

The sum of the using amount of the components is 100%;

3) putting the uniformly mixed powder obtained in the step 1) into a balling disk, atomizing deionized water by an atomizer, adding the atomized deionized water into the balling disk to ball the powder, and controlling the diameter of the ball formed by the core material to be 2.5-3 mm;

5) Continuously adding the core material balls prepared in the step 4) into a ball forming disc, atomizing deionized water through an atomizer, and alternately adding the deionized water and the shell material powder obtained in the step 2) into the ball forming disc; controlling the diameter of the ball to be 5-6 mm;

6) sieving the material balls prepared in the step 5) to select 5-6mm material balls for later use;

7) putting the pellets obtained in the step 6) into a drying oven at 105 ℃ for drying for 3 hours, and taking out the drying oven;

8) putting the material balls obtained in the step 7) into a sintering furnace to be sintered according to the following procedures to form ceramic sand;

a preheating stage: heating from room temperature to 200 ℃ at a heating rate of 5-10 ℃/min, and staying at 200 ℃ for 1-2 hours;

a temperature rising stage: raising the furnace temperature from 200 ℃ to 1150-1200 ℃ at a temperature raising speed of 5-20 ℃/min, and preserving the temperature for 20-30 min;

2. The method of claim 1, wherein:

and soaking the pottery sand in 0.5mol/L chloride ion solution for seven days to determine the chloride ion binding performance of the pottery sand.