CN112341091A

CN112341091A - Paving brick prepared from construction waste recycled aggregate and preparation process thereof

Info

Publication number: CN112341091A
Application number: CN202011279787.1A
Authority: CN
Inventors: 王淼; 李岩凌; 周伟; 刘文才; 何强
Original assignee: BCEG Resources Recycling Co Ltd
Current assignee: BCEG Resources Recycling Co Ltd
Priority date: 2020-11-16
Filing date: 2020-11-16
Publication date: 2021-02-09

Abstract

The invention provides a pavement brick prepared from construction waste recycled aggregate and a preparation process thereof, wherein the pavement brick is a recycled aggregate pavement brick with a surface layer; wherein, the surface layer mainly comprises the following raw materials in percentage by mass: 22-29% of cement, 62-70% of natural aggregate and 6-13% of water. The bottom layer mainly comprises the following raw materials in percentage by mass: 12-15% of cement, 46-52% of brick-concrete mixed recycled aggregate, 21-29% of concrete recycled aggregate, 3-6% of mineral admixture and 8-10% of water. The pavement brick provided by the invention has good appearance quality, high compressive strength, frost resistance and low water absorption, and can be used for preparing the pavement brick with excellent performance and simultaneously fully utilizing building wastes, thereby ensuring the full utilization of resources.

Description

Paving brick prepared from construction waste recycled aggregate and preparation process thereof

Technical Field

The invention relates to the field of building materials, in particular to a pavement brick prepared from building garbage recycled aggregate and a preparation process thereof.

Background

With the rapid development of urban infrastructure and the continuous enhancement of environmental protection awareness of people, the effective treatment of construction waste has become one of the important contents which cannot be ignored in urban development. Construction waste has been gradually recognized as a solid material having a certain strength, and is regarded as "a resource misplaced".

The cement-based materials (common concrete, lightweight aggregate concrete, cement mortar and the like), sintering materials (sintered bricks, clay tiles, ceramic tiles and the like) and natural stone materials contained in the construction waste can be used as new concrete and products thereof, novel wall materials, road structure foundations or auxiliary foundations through recycling, processing and strengthening treatment to obtain regenerated products.

The regeneration raw materials of the construction waste can be mainly divided into concrete regeneration aggregate and brick and tile regeneration aggregate according to the source. The concrete recycled aggregate is recycled aggregate formed by crushing old concrete, belongs to crushed stone and is basically in a multi-edge-angle shape. According to different aggregate particle size ranges, the concrete recycled aggregate is divided into recycled coarse aggregate and recycled fine aggregate. The surface of the recycled concrete aggregate is usually adhered with a certain amount of primary mortar, so that the performance of the recycled aggregate is obviously different from that of the primary aggregate.

The brick and tile recycled aggregate is from broken brick and tile waste, and is mainly used for breaking broken bricks and tiles to finally become the brick and tile recycled aggregate. Because the brick and tile recycled aggregate has the characteristics of large water absorption capacity, high crushing index value, poor performance stability, high impurity content and the like, the brick and tile recycled aggregate can only be used for configuring recycled products with medium and low strength. Therefore, the application and popularization range of the brick and tile recycled aggregate is greatly influenced.

As a conventional cement product on the market, the compression strength of the pavement brick comprises three strength grades of Cc40, Cc50 and Cc60 according to the standard requirement of the concrete pavement brick, the strength requirement of the pavement brick of a pedestrian road is Cc30, the requirement of a square parking lot is Cc40, and the demand of the pavement bricks of Cc30 and Cc40 grades on the market is the largest. For the pavement brick with the Cc30 strength grade, a certain research foundation exists, the pavement brick meeting the 30MPa strength can be prepared by using cement and recycled aggregate of bricks and tiles, but the pavement brick with the Cc40 grade has higher preparation difficulty by using recycled aggregate of bricks and tiles.

Therefore, it is necessary to develop a pavement brick with high compressive strength grade by using recycled aggregate of brick and tile, and to widen the range of the existing construction waste raw materials.

Disclosure of Invention

Therefore, the invention provides the pavement brick prepared from the construction waste recycled aggregate with high compressive strength, and also provides a preparation process of the pavement brick in the technical scheme of the invention, aiming at the problem that the pavement brick prepared from the existing brick and tile recycled aggregate has low strength grade.

Therefore, the first technical scheme provided by the invention is as follows:

a pavement brick prepared from construction waste recycled aggregate is a recycled aggregate pavement brick with a surface layer, and is prepared from two materials of the surface layer and a bottom layer in different proportions.

The recycled aggregate contains part of cement mortar, so that the recycled aggregate is greatly different from natural coarse aggregate, and meanwhile, the content of the mortar in the recycled aggregate is also one of the main factors influencing the performance of the recycled aggregate.

In order to improve the compressive strength of the pavement brick prepared by the brick-concrete mixed recycled aggregate, in the technical scheme of the invention, the surface layer of the pavement brick is preferably prepared by natural aggregate, wherein:

the surface layer mainly comprises the following raw materials in percentage by mass: 22-29% of cement, 62-70% of natural aggregate and 6-13% of water.

Because the water absorption and crushing of the brick-concrete mixed recycled aggregate have larger differences compared with the concrete recycled aggregate and the natural aggregate, when the pavement brick containing the brick-concrete mixed recycled aggregate is developed, the composition and the proportion of raw materials need to be reasonably designed by mainly considering the superposition effect among the recycled aggregates from different sources so as to improve the compressive strength of the brick-concrete mixed recycled aggregate product.

In the technical scheme of the invention, the bottom layer of the pavement brick is prepared by combining main components such as brick-concrete mixed recycled aggregate, concrete recycled aggregate, mineral admixture, cement and the like.

Wherein, the bottom layer preferably comprises the following raw materials in percentage by mass: 12-15% of cement, 46-52% of brick-concrete mixed recycled aggregate, 21-29% of concrete recycled aggregate, 3-6% of mineral admixture and 8-10% of water.

By the surface layer and the bottom layer with reasonable formula, the pavement brick provided by the technical scheme of the invention has the compression strength range of 40-46 MPa.

Preferably, the thickness range of the pavement brick prepared by the technical scheme of the invention is 50-63 mm.

Preferably, in the technical scheme of the invention, the thickness ratio of the surface layer to the bottom layer in the pavement brick is preferably 1 (4-6). When the thickness ratio of the surface layer to the bottom layer is smaller than the ratio, the compressive strength of the prepared pavement brick cannot meet more than 40 MPa; if the thickness of the surface layer and the bottom layer is larger than the ratio, the needed natural aggregate is too much, and the waste of natural resources is caused. Through repeated tests, the thickness ratio in the range can meet the requirement of the pavement brick on the compressive strength, and meanwhile, the consumption of natural aggregate can be saved to the greatest extent.

In the technical scheme of the invention, the natural aggregate of the pavement brick can be from one of tailing sand or river sand.

Preferably, the natural aggregate of the surface layer in the technical scheme of the invention is tailing sand; the pavement brick surface layer prepared from the tailing sand presents granular feeling, and the cement coating effect and the wear resistance are good. Meanwhile, the yield of the pavement bricks prepared from the tailing sand is high.

Preferably, the particle size of the natural aggregate in the technical scheme of the invention is less than 5mm, and the pavement brick surface layer prepared by mixing the natural aggregate with the particle size and the cement has excellent compressive strength and appearance.

In the technical scheme of the invention, the recycled aggregate of the bottom layer of the pavement brick is obtained after screening treatment, for example, the recycled aggregate mixed with brick and concrete and the recycled aggregate of concrete can be respectively cleaned, crushed and screened. At present, most of the production processes of recycled aggregate organically combine cutting and crushing equipment, conveying machinery, screening equipment and impurity removing equipment to complete the procedures of crushing, impurity removal, classification and the like.

In the technical scheme of the invention, the brick-concrete mixed recycled aggregate is preferably crushed and screened to form a raw material with the particle size of less than 5mm, and simultaneously, the mass ratio of concrete in the brick-concrete mixed recycled aggregate is 30%.

The brick-concrete mixed recycled aggregate in the technical scheme of the invention has the water absorption of 6.32-7.41%, the crushing ratio of 28.9-32.1% and the apparent density of 2.51-2.61g.cm^-3。

In the technical scheme of the invention, the recycled concrete aggregate is preferably crushed and screened into the raw material with the particle size of 3-8 mm.

In the technical scheme of the invention, the water absorption of the concrete recycled aggregate is 4.26-4.45%, the crushing ratio is 22.1-23.8%, and the apparent density is 2.65-2.69g.cm^-3。

Because the recycled concrete aggregate has more edges and corners, rough surface and hardened cement mortar contained on the surface, a great amount of microcracks are caused in the recycled concrete aggregate due to loss accumulation in the crushing process, so that the recycled concrete aggregate has the defects of large porosity, large water absorption, small stacking density, high crushing index value and the like, and in addition, the brick-concrete mixed recycled aggregate has the reasons of large water absorption, high crushing index value, poor performance stability and the like, when the recycled aggregate is used for preparing the pavement brick, how to improve the compressive strength of the bottom layer of the pavement brick is the key.

In the technical scheme of the invention, in order to improve the strength and elastic modulus of the concrete recycled aggregate, the brick-concrete mixed recycled aggregate and the cement after mixing and hardening and reduce the shrinkage rate of the pavement brick, the mineral admixture is added into the bottom layer material.

The mineral admixture in the technical scheme of the invention mainly comprises limestone powder, volcanic ash and slag.

The limestone powder is mainly calcium carbonate, and is easy to grind. Volcanic ash is an active material, and a certain amount of active silica, active alumina and the like exist, and can react with calcium oxide at normal temperature and in the presence of water to generate a hydraulic gel material. The volcanic ash in the technical scheme of the invention is preferably natural volcanic ash.

The slag of the invention is preferably industrial slag of high-temperature steel making, the main component of the slag is aluminosilicate, and the slag has high activity after being excited by alkalinity or sulfate.

The invention adopts the composite mineral admixture, avoids the problems of product cracking, early strength reduction, large product shrinkage and the like caused by a single mineral admixture raw material, simultaneously fully utilizes various industrial waste residues, reduces the environmental pollution, reduces the production cost, enables the pavement brick to be more compact and improves the durability of the pavement brick.

In the technical scheme of the invention, the mineral admixture mainly comprises 45-55% of limestone powder, 31-35% of volcanic ash and 17-22% of slag by mass percent.

In addition, the invention also provides another technical scheme, which is a production process for preparing the pavior brick by using the construction waste recycled aggregate, and the preparation process comprises the following steps:

(1) preparing a bottom layer raw material and a surface layer raw material. The construction waste is respectively cleaned, crushed and screened according to the concrete and brick-concrete mixture, the brick-concrete mixed recycled aggregate is screened into raw materials with the particle size of less than 5mm, the concrete recycled aggregate is screened into raw materials with the particle size of 3-8mm, and the two recycled aggregates are classified and stored for later use.

(2) Respectively mixing and stirring the raw materials of the bottom layer and the surface layer, placing a mold of the pavement brick on a vibrating table, filling the mixed raw materials of the bottom layer into the mold for multiple times, and spraying water mist after filling each layer, so that the humidity is kept at 40-45% after compaction, and each layer vibrates for 3-5 s.

Preferably, in the technical scheme of the invention, the raw materials of the bottom layer of the pavement brick can be stirred by firstly stirring the brick-concrete mixed recycled aggregate and the concrete recycled aggregate for 1-2min by a stirrer, then adding the cement and continuously stirring for 1min, then adding the mineral admixture and stirring for 30s, then adding 40% of the total amount of water and stirring for 2min, and then adding the rest 60% of water and continuously stirring for 1.5 min. The final humidity was maintained at 40-41%.

(3) And adding the mixed surface layer raw material into a mould, and keeping the vibration time to be 3-4 s.

(4) And pressurizing and vibrating the pavement brick surface layer, wherein the pressure is 5.5-6.0MPa, and the vibration time is 5-6 s.

(5) And (3) putting the blank body with the mold into a curing box for curing for 48h, then demolding and stacking, and then putting into a saturated steam curing cellar for continuous curing for 24h to obtain the pavior brick.

In summary, the technical scheme of the invention has the following beneficial effects:

(1) in the technical scheme of the invention, the compression strength of the pavement brick prepared by using the brick-concrete mixed recycled aggregate is more than 40MPa by reasonably setting the components and the proportion of the raw materials of the surface layer and the bottom layer, the problem that the pavement brick with the Cc40 grade is difficult to prepare by using the brick-tile recycled aggregate is solved, and a solution is provided for solving the problems that the brick-concrete mixed recycled aggregate has high water absorption rate and high crushing ratio and is difficult to prepare the pavement brick with high compression strength.

(2) Meanwhile, in the technical scheme of the invention, the mineral admixture is added into the brick-concrete mixed recycled aggregate and the concrete recycled aggregate, and the various mineral admixtures, the brick-concrete mixed recycled aggregate and the concrete recycled aggregate are reasonably matched, so that the cracking of the pavement brick product is effectively reduced, and the compactness and the durability of the pavement brick are improved. Moreover, the industrial waste residue is fully utilized, the environmental pollution is reduced, and the production cost is reduced.

Detailed Description

The invention is further described below with reference to specific embodiments.

The main raw materials used in the embodiment of the invention are as follows:

the cement is PO42.5 cement produced by a Sanhe diamond cement factory; the recycled concrete aggregate is a raw material for simple line crushing treatment of east dam of the applicant; the brick and tile recycled aggregate is a raw material for crushing treatment of the project part of east dam of the applicant; the tailings sand and river sand in the natural aggregate are obtained by commercial purchase; the mineral admixture is self-made by the applicant.

Example 1

A pavement brick prepared from construction waste recycled aggregate comprises a surface layer and a bottom layer.

The surface layer is prepared from the following raw materials in percentage by mass: 25% of cement, 62% of tailing sand and 13% of water. Wherein the grain size of the tailing sand is less than 5 mm.

The bottom layer is prepared from the following raw materials in percentage by mass: 12% of cement, 48% of brick-concrete mixed recycled aggregate, 26% of concrete recycled aggregate, 4% of mineral admixture and 10% of water.

Wherein the mineral admixture consists of 47 mass percent of limestone powder, 33 mass percent of natural volcanic ash and 20 mass percent of slag.

The grain diameter of the brick-concrete mixed recycled aggregate is less than 5mm, and the grain diameter of the concrete recycled aggregate is 3-8 mm.

The total thickness of the pavement brick is 50mm, wherein the thickness of the surface layer is 10mm, and the thickness of the bottom layer is 40 mm. The concrete preparation process of the pavior brick comprises the following steps:

(2) The raw materials of the bottom layer and the surface layer of the pavement brick are respectively mixed and stirred. For the stirring of the bottom layer raw materials of the pavement bricks, firstly, the brick-concrete mixed recycled aggregate and the concrete recycled aggregate are stirred for 1min by a stirrer, then, the cement is added and stirred for 1min continuously, then, the mineral admixture is added and stirred for 30s, then, 40 percent of the total amount of water is added and stirred for 2min, and then, the rest 60 percent of the water is added and stirred for 1.5min continuously. The final humidity was maintained at 40%.

And then, placing a mold of the pavement brick on a vibration table, filling the mixed bottom raw materials into the mold for multiple times, and spraying water mist after filling each layer, so that the humidity is kept at 40% after compaction, and each layer vibrates for 3 s.

(3) And adding the mixed surface layer raw material into a mould, and keeping the vibration time for 3 s.

(4) And pressurizing and vibrating the pavement brick surface layer, wherein the pressure is 5.5MPa, and the vibration time is 5 s.

Example 2

The surface layer is prepared from the following raw materials in percentage by mass: 22% of cement, 68% of tailing sand and 10% of water. Wherein the grain size of the tailing sand is less than 5 mm.

The bottom layer is prepared from the following raw materials in percentage by mass: 14% of cement, 46% of brick-concrete mixed recycled aggregate, 29% of concrete recycled aggregate, 3% of mineral admixture and 8% of water.

Wherein the mineral admixture consists of 55 mass percent of limestone powder, 31 mass percent of natural volcanic ash and 14 mass percent of slag.

(2) The raw materials of the bottom layer and the surface layer of the pavement brick are respectively mixed and stirred. For the stirring of the bottom layer raw materials of the pavement bricks, firstly, the brick-concrete mixed recycled aggregate and the concrete recycled aggregate are stirred for 2min by a stirrer, then, the cement is added and stirred for 1min continuously, then, the mineral admixture is added and stirred for 30s, then, 40 percent of the total amount of water is added and stirred for 2min, and then, the rest 60 percent of the water is added and stirred for 1.5min continuously. The final humidity was maintained at 41%.

And then, placing a mold of the pavement brick on a vibration table, filling the mixed bottom raw materials into the mold for multiple times, and spraying water mist after filling each layer, so that the humidity is kept at 45% after jolt compaction, and each layer vibrates for 5 s.

(3) And adding the mixed surface layer raw material into a mould, and keeping the vibration time for 4 s.

(4) And pressurizing and vibrating the pavement brick surface layer, wherein the pressure is 6.0MPa, and the vibration time is 6 s.

Example 3

The surface layer is prepared from the following raw materials in percentage by mass: 29% of cement, 63% of tailing sand and 8% of water. Wherein the grain size of the tailing sand is less than 5 mm.

The bottom layer is prepared from the following raw materials in percentage by mass: 15% of cement, 47% of brick-concrete mixed recycled aggregate, 25% of concrete recycled aggregate, 5% of mineral admixture and 8% of water.

Wherein the mineral admixture consists of 45 mass percent of limestone powder, 34 mass percent of natural volcanic ash and 21 mass percent of slag.

The total thickness of the pavement brick is 63mm, wherein the thickness of the surface layer is 9mm, and the thickness of the bottom layer is 54 mm. The concrete preparation process of the pavior brick is the same as that of the example 1.

Example 4

The surface layer is prepared from the following raw materials in percentage by mass: 24% of cement, 70% of river sand and 6% of water. Wherein the grain size of the river sand is less than 5 mm.

The bottom layer is prepared from the following raw materials in percentage by mass: 13% of cement, 50% of brick-concrete mixed recycled aggregate, 21% of concrete recycled aggregate, 6% of mineral admixture and 10% of water.

Wherein the mineral admixture consists of 48 mass percent of limestone powder, 35 mass percent of natural volcanic ash and 17 mass percent of slag.

The total thickness of the pavement brick is 54mm, wherein the thickness of the surface layer is 9mm, and the thickness of the bottom layer is 45 mm. The concrete preparation process of the pavior brick is the same as that of the example 1.

Example 5

The surface layer is prepared from the following raw materials in percentage by mass: 27% of cement, 65% of river sand and 8% of water. Wherein the grain size of the river sand is less than 5 mm.

The bottom layer is prepared from the following raw materials in percentage by mass: 14% of cement, 52% of brick-concrete mixed recycled aggregate, 23% of concrete recycled aggregate, 3% of mineral admixture and 8% of water.

Wherein the mineral admixture consists of 46 percent of limestone powder, 32 percent of natural volcanic ash and 22 percent of slag in percentage by mass.

Comparative example 1

A pavement brick comprising only the same base material as in example 1.

The total thickness of the pavement brick is 50 mm. The concrete preparation process of the pavior brick comprises the following steps:

(1) preparing raw materials of the pavior brick. The construction waste is respectively cleaned, crushed and screened according to the concrete and brick-concrete mixture, the brick-concrete mixed recycled aggregate is screened into raw materials with the particle size of less than 5mm, the concrete recycled aggregate is screened into raw materials with the particle size of 3-8mm, and the two recycled aggregates are classified and stored for later use.

(2) Mixing and stirring the raw materials of the pavior brick. Firstly stirring the brick-concrete mixed recycled aggregate and the concrete recycled aggregate by a stirrer for 1min, then adding the cement for continuously stirring for 1min, then adding the mineral admixture for stirring for 30s, then adding 40 percent of the total amount of water for stirring for 2min, and then adding the rest 60 percent of water for continuously stirring for 1.5 min. The final humidity was maintained at 40%.

And then, placing a mold of the pavement brick on a vibration table, filling the mixed raw materials into the mold for multiple times, and spraying water mist after filling each layer, so that the humidity is kept at 40% after compaction, and each layer vibrates for 3 s.

(3) And pressurizing and vibrating the pavement brick, wherein the pressure is 5.5MPa, and the vibration time is 5 s.

(4) And (3) putting the blank body with the mold into a curing box for curing for 48h, then demolding and stacking, and then putting into a saturated steam curing cellar for continuous curing for 24h to obtain the pavior brick.

Comparative example 2

A pavement brick is composed of a surface layer and a bottom layer.

The bottom layer is prepared from the following raw materials in percentage by mass: 14% of cement, 75% of brick-concrete mixed recycled aggregate, 3% of mineral admixture and 8% of water.

The grain diameter of the brick-concrete mixed recycled aggregate is less than 5 mm.

The main difference between comparative example 2 and example 2 is that the concrete recycled aggregate in example 2 was replaced with an equal amount of brick-concrete mixed recycled aggregate.

Comparative example 2 a pavior brick was prepared in substantially the same manner as in example 2. Since the concrete recycled aggregate was not added in comparative example 2, the step of adding the raw material was omitted.

Comparative example 3

A pavement brick is composed of a surface layer and a bottom layer.

The bottom layer is prepared from the following raw materials in percentage by mass: 20% of cement, 47% of brick-concrete mixed recycled aggregate, 25% of concrete recycled aggregate and 8% of water.

The main difference between comparative example 3 and example 3 is that the mineral admixture of example 3 was replaced with an equal amount of cement.

Comparative example 3 a pavior brick was prepared in substantially the same manner as in example 3. Since the mineral admixture was not added in comparative example 3, the step of adding the raw material was omitted.

Comparative example 4

A pavement brick is composed of a surface layer and a bottom layer.

The surface layer is prepared from the following raw materials in percentage by mass: 24% of cement, 70% of brick-concrete mixed recycled aggregate and 6% of water.

The main difference between comparative example 4 and example 4 is that the river sand of the surface course in example 4 was replaced with an equal amount of brick-concrete mixed recycled aggregate.

Comparative example 4 a pavior brick was prepared in substantially the same manner as in example 4.

Comparative example 5

A pavement brick is composed of a surface layer and a bottom layer.

The grain diameter of the brick-concrete mixed recycled aggregate is 10-15mm, and the grain diameter of the concrete recycled aggregate is 3-8 mm.

Comparative example 5 is different from example 5 in that the particle size of the brick-and-concrete mixed recycled aggregate in example 5 was increased to 10-15 mm.

Comparative example 5 a pavior brick was prepared in substantially the same manner as in example 5.

Comparative example 6

A pavement brick is composed of a surface layer and a bottom layer.

The bottom layer is prepared from the following raw materials in percentage by mass: 14% of cement, 52% of brick-concrete mixed recycled aggregate, 23% of concrete recycled aggregate, 3% of limestone powder and 8% of water.

Comparative example 6 differs from example 5 in that the mineral admixture of example 5 is replaced by limestone powder, a single mineral admixture.

Comparative example 6 a pavior brick was prepared in substantially the same manner as in example 5.

In order to better evaluate the excellence of the performance of the pavement brick prepared by the technical scheme of the invention, the invention carries out the following tests on the appearance quality, the compressive strength and the physical performance of the pavement brick.

1.1 pavement brick appearance quality

According to the technical requirements for the pavior bricks in the national standard GB28635-2012 concrete pavior bricks, the appearance quality requirements of the concrete pavior bricks are shown in Table 1.

TABLE 1 appearance quality requirements

Serial number	Item	Require that
			1	Maximum projection size/mm of skin sticking or defect of paving surface	≤5
2	Maximum projection size/mm of unfilled edge or corner of paving surface	≤5
			3	Paving crack cross	Is not allowed to
4	Color difference, mottle	Is not obvious
			5	Flatness/mm	≤2
6	Verticality/mm	≤2

The appearance quality of the pavior bricks prepared in the examples 1-5 and the comparative examples 1-6 of the invention obtained by adopting the national standard measurement method is shown in Table 2.

TABLE 2 quality of appearance of pavior bricks of examples and comparative examples of the invention

From table 2, it can be seen that the pavior brick prepared by the technical scheme of the invention can meet the requirements of GB28635-2012 concrete pavior brick on the appearance quality of the pavior brick in the aspects of anti-skin adhesion or defect, anti-edge deletion or corner drop, anti-cracking, color and color difference uniformity, flatness and verticality.

1.2 compressive Strength of pavior brick

The compressive strength of the paving bricks prepared in examples 1-5 and comparative examples 1-6 of the invention obtained by the measurement method of national standard GB28635-2012 is shown in Table 3.

TABLE 3 compression Strength of pavior bricks of examples and comparative examples of the invention

Serial number	Average value/MPa	Monoblock minimum/MPa
			Example 1	45.1	39.3
Example 2	43.3	38.9
			Example 3	46.5	40.1
Example 4	40.8	38.3
			Example 5	42.5	36.4
Comparative example 1	35.7	30.1
			Comparative example 2	38.6	34.2
Comparative example 3	36.5	33.8
			Comparison ofExample 4	35.1	30.5
Comparative example 5	34.3	31.2
			Comparative example 6	36.7	32.6

As can be seen from Table 3, the average values of the compressive strengths of the pavior bricks prepared by the technical scheme of the invention are all above 40MPa, and the minimum value of a single brick is more than or equal to 36.4MPa, so that the requirement of the Cc40 grade in the national standard GB28635-2012 on the strength of the pavior brick can be met.

1.3 physical Properties of the pavior brick

Physical properties of the pavior bricks prepared in examples 1-5 and comparative examples 1-6 of the present invention obtained by national standard measurement methods are shown in table 4.

TABLE 4 physical Properties of pavior bricks of examples and comparative examples of the present invention

Serial number	Freezing resistance/%)	Water absorption/%)
			Example 1	12.5	3.2
Example 2	14.1	4.6
			Example 3	13.1	4.1
Example 4	15.2	4.3
			Example 5	14.7	5.4
Comparative example 1	18.3	6.8
			Comparative example 2	19.6	7.1
Comparative example 3	22.5	6.4
			Comparative example 4	18.4	6.5
Comparative example 5	17.1	7.6
			Comparative example 6	20.3	6.3

As can be seen from Table 4, the pavement brick prepared by the technical scheme of the invention has the frost resistance of less than or equal to 15.2% and the water absorption of less than or equal to 5.4%, and can meet the requirements of national standard GB28635-2012 on the physical properties of the pavement brick.

In conclusion, the pavement brick with the surface layer, prepared by the technical scheme of the invention, has the advantages that through reasonably setting the raw materials and the proportion of the surface layer and the bottom layer and the thicknesses of the surface layer and the bottom layer, selecting proper particle sizes of the recycled aggregate and the natural aggregate, and through the synergistic effect of various raw materials such as cement, brick-mixed recycled aggregate, concrete recycled aggregate, mineral admixture, natural aggregate, water and the like, the prepared pavement brick has good appearance quality, no cracking and uniform color difference, has the compressive strength of more than or equal to 40MPa, has excellent frost resistance and smaller water absorption, and provides a good technical scheme for developing recycled products prepared from brick-tile recycled aggregates.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to make many variations and modifications without departing from the basic inventive concept, which falls within the scope of the appended claims.

Claims

1. A pavement brick prepared from construction waste recycled aggregate is characterized in that the pavement brick is a recycled aggregate pavement brick with a surface layer, and the pavement brick consists of a surface layer and a bottom layer;

wherein, the surface layer mainly comprises the following raw materials in percentage by mass: 22-29% of cement, 62-70% of natural aggregate and 6-13% of water;

the bottom layer mainly comprises the following raw materials in percentage by mass: 12-15% of cement, 46-52% of brick-concrete mixed recycled aggregate, 21-29% of concrete recycled aggregate, 3-6% of mineral admixture and 8-10% of water.

2. The paving brick prepared from the construction waste recycled aggregate according to claim 1, wherein the compression strength of the paving brick is 40-46 MPa.

3. The paving brick prepared from the construction waste recycled aggregate according to the claim 1, wherein the thickness ratio of the surface layer to the bottom layer in the paving brick is preferably 1 (4-6);

wherein the total thickness of the pavement brick is 50-63 mm.

4. The paving brick prepared from the construction waste recycled aggregate according to the claim 1, wherein the natural aggregate of the paving brick surface layer can be selected from one of tailings or river sand, preferably tailings.

5. The paving brick prepared from the construction waste recycled aggregate according to claim 1, wherein the particle size of the natural aggregate is less than 5 mm.

6. The paving brick prepared from the construction waste recycled aggregate according to claim 1, wherein the particle size of the brick-concrete mixed recycled aggregate is less than 5 mm;

wherein the mass ratio of concrete in the brick-concrete mixed recycled aggregate is 30%.

7. The paving brick prepared from the construction waste recycled aggregate according to claim 1, wherein the particle size of the concrete recycled aggregate is in the range of 3-8 mm.

8. The paving brick prepared from the construction waste recycled aggregate according to claim 1, wherein the mineral admixture comprises 45-55% of limestone powder, 31-35% of volcanic ash and 17-22% of slag by mass percent.

9. The paving brick prepared from the construction waste recycled aggregate according to claim 8, wherein the slag is industrial waste slag generated in steel making, and the volcanic ash is natural volcanic ash.

10. A process for preparing a paving brick made of construction waste recycled aggregate according to claims 1-9, characterized in that the preparation process comprises the following steps:

(1) preparing raw materials of a bottom layer and a surface layer; respectively crushing and screening the construction waste according to the concrete and brick-concrete mixture, and storing the construction waste in a classified manner according to the brick-concrete mixed recycled aggregate and the concrete recycled aggregate for later use;

(2) respectively mixing and stirring the raw materials of the bottom layer and the surface layer, placing a mold of the pavement brick on a vibration table, filling the mixed raw materials of the bottom layer into the mold for multiple times, and spraying water mist after each layer is filled, so that the humidity is kept at 40-45% after compaction, and each layer vibrates for 3-5 s;

(3) adding the mixed surface layer raw material into a mould, and keeping the vibration time to be 3-4 s;

(4) pressurizing and vibrating the pavement brick surface layer, wherein the pressure is 5.5-6.0MPa, and the vibration time is 5-6 s;