CN116444216A

CN116444216A - Recycled concrete and preparation method thereof

Info

Publication number: CN116444216A
Application number: CN202310448233.7A
Authority: CN
Inventors: 胡水忠; 林松涛
Original assignee: Hangzhou Zhouqiao Building Materials Co ltd
Current assignee: Hangzhou Zhouqiao Building Materials Co ltd
Priority date: 2023-04-24
Filing date: 2023-04-24
Publication date: 2023-07-18

Abstract

The application relates to recycled concrete and a preparation method thereof, and relates to the technical field of concrete, wherein raw materials of the recycled concrete comprise recycled coarse aggregate filler, reinforcing fibers, natural fine aggregate, cement, a water reducing agent and water, and the filler is adhered and filled on the surface and in cracks of the recycled coarse aggregate; the raw materials of the filler comprise silicate, nano silicon dioxide, modified carbon fiber, glass beads and water. According to the method, the filling modification of the recycled coarse aggregate is performed through the filling agent, microcracks and surface pores on the recycled coarse aggregate can be plugged to a certain extent, the porosity of the recycled coarse aggregate is reduced, meanwhile, the filling agent attached to the surface of the recycled coarse aggregate can further reduce the contact between the recycled coarse aggregate and external water, the water absorption rate of the recycled coarse aggregate is reduced through mutual cooperation, and the strength of recycled concrete is further improved.

Description

Recycled concrete and preparation method thereof

Technical Field

The application relates to the field of concrete technology, in particular to recycled concrete and a preparation method thereof.

Background

The recycled concrete is novel concrete prepared by crushing, cleaning and grading waste concrete blocks, mixing the crushed, cleaned and graded concrete blocks with the graded concrete blocks according to a certain proportion, partially or completely replacing natural aggregates such as sand and stone, and adding cement, water and the like. The recycled concrete can be in the form of aggregate combinations in the following cases: the aggregate is all regenerated aggregate; the coarse aggregate is regenerated aggregate, and the fine aggregate is natural sand; the coarse aggregate is natural broken stone or pebble, and the fine aggregate is regenerated aggregate; the regenerated aggregate replaces part of the coarse aggregate or the fine aggregate.

Because the waste concrete is subjected to larger external force in the crushing process, compared with the natural aggregate, the regenerated coarse aggregate can generate a large number of cracks in the interior and the surface of the aggregate, so that the water absorption rate and the water absorption rate of the regenerated aggregate are far higher than those of the natural aggregate, and the defects of high porosity, high water absorption rate, low strength and the like exist, so that the strength of the obtained concrete is obviously insufficient. In the prior art, the strength of the recycled concrete is improved by adding excessive water reducer and compounding small-particle fine aggregate, but the problem of high porosity of the recycled aggregate is not solved effectively, so that the improvement of the strength of the concrete is limited.

Disclosure of Invention

According to the technical problems, the application provides the recycled concrete and the preparation method thereof, and the recycled concrete with high strength and good durability is obtained by improving the porosity of the recycled coarse aggregate and reducing the water absorption of the concrete.

In a first aspect, the present application provides a recycled concrete, which adopts the following technical scheme:

the recycled concrete comprises the following raw materials in parts by weight:

65-80 parts of recycled coarse aggregate;

5-10 parts of filler;

3-10 parts of reinforcing fiber;

20-30 parts of natural fine aggregate;

25-30 parts of cement;

1-3 parts of water reducer;

5-15 parts of water;

the filler is adhered and filled on the surface of the recycled coarse aggregate and in cracks.

By adopting the technical scheme, a large number of pores existing in the recycled coarse aggregate and on the surface are one of the main factors causing high water absorption rate, micro-cracks and surface pores on the recycled coarse aggregate can be blocked to a certain extent by filling the filler in cracks of the recycled coarse aggregate, the porosity of the recycled coarse aggregate is reduced, meanwhile, the filler attached to the surface of the recycled coarse aggregate can further reduce the contact between the recycled coarse aggregate and external water, and the water absorption rate of the recycled coarse aggregate is reduced by mutual cooperation, so that the strength of the recycled concrete is improved. The reinforced fiber has excellent performances of high modulus, high strength, high temperature resistance, corrosion resistance and the like, can improve the strength of concrete after being added into the concrete, can play a certain constraint role on the recycled coarse aggregate, inhibit the expansion and extension of cracks of the recycled coarse aggregate in the slow water absorption process, and improve the crack resistance of the concrete. The natural fine aggregate can be matched with the filler to fill cracks and pores of the recycled coarse aggregate through the matching with the recycled coarse aggregate, so that the overall strength of the concrete is improved.

Optionally, the filler comprises the following raw materials in parts by weight:

20-30 parts of silicate;

15-20 parts of nano silicon dioxide;

5-15 parts of modified carbon fiber;

10-15 parts of glass beads;

20-35 parts of water.

Through adopting above-mentioned technical scheme, silicate, nano silicon dioxide and water can form the adhesive that has good bonding effect after mixing, and rethread adds modified carbon fiber, and carbon fiber has advantages such as good corrosion-resistant, high strength, high modulus, mixes the back with silicate system gluing agent and fills in the gap of regeneration coarse aggregate, and the modified carbon fiber that will fill in regeneration coarse aggregate gap after the gluing agent solidification is further fixed, and modified carbon fiber can fully exert self high strength high modulus's advantage, plays constraint crack extension's effect to regeneration coarse aggregate, promotes the crack resistance of concrete. The glass beads have the characteristics of high strength, high dispersion, thermal stability, low water absorption and the like, and the glass beads and the modified carbon fibers are matched and filled in gaps of the recycled coarse aggregate, so that the compressive strength of the recycled coarse aggregate can be enhanced, and the compressive property of concrete is further improved. The filler is used for modifying and filling the recycled coarse aggregate, so that the water absorption rate of the recycled coarse aggregate can be effectively reduced, and the strength of the recycled coarse aggregate can be improved.

Optionally, the modified carbon fiber is a carbon fiber subjected to plasma surface treatment.

Alternatively to this, the method may comprise, the length of the modified carbon fiber is 0.5-5 mm.

By adopting the technical scheme, the carbon fiber is used as an organic fiber material, the surface hydrophilicity is poor, the dispersibility in an inorganic adhesive system is low, the hydrophilicity of the carbon fiber can be improved by carrying out surface modification treatment on the carbon fiber by plasma, and the carbon fiber is easier to disperse in the inorganic material system. Meanwhile, active organic groups can be introduced to the surface of the carbon fiber through ionization treatment of plasma, and in the subsequent mixing process with silicate and the like, active ions in the silicate and the active organic groups undergo substitution grafting reaction, so that the modified carbon fiber and the recycled coarse aggregate can be well fixedly connected after the silicate adhesive is cured, and the constraint effect on cracks of the recycled coarse aggregate is improved.

Optionally, the granularity of the glass beads is 30-80 μm.

By adopting the technical scheme, the granularity of the glass beads can influence the filling effect of the filler, the filling amount of the glass beads in the recycled coarse aggregate cracks is small when the granularity is too large, and the strength improvement effect on the recycled coarse aggregate is limited; the glass beads have poor dispersibility when the particle size is too small, and the distribution of the modified carbon fibers in the gaps of the recycled coarse aggregate can be influenced in the filling process, so that the cracking resistance of the concrete is influenced.

Optionally, the filler is prepared by the following method:

s1, placing the raw carbon fiber in a roller plasma cleaning machine for modification treatment to obtain modified carbon fiber, wherein the treatment time is 30-60 min, the temperature is 25-30 ℃, and the discharge power is 200-400W;

s2, dissolving silicate in water, then adding modified carbon fiber, nano silicon dioxide and glass beads, and stirring and mixing to obtain the filler.

By adopting the technical scheme, the surface modification treatment is carried out on the carbon fiber by the roller plasma cleaning machine, so that the surface modification of the carbon fiber is more sufficient, and the combination property of the modified carbon fiber and other components is better.

Optionally, the grain size of the recycled coarse aggregate is 5-15 mm.

Optionally, the fineness modulus of the natural fine aggregate is 2.0-3.0.

Optionally, the water reducer is a polycarboxylate water reducer.

Optionally, the reinforcing fiber is one or two of glass fiber and carbon fiber.

Further preferably, the reinforcing fiber is a carbon fiber subjected to plasma surface modification treatment, and the length of the carbon fiber is 15-30 mm.

By adopting the technical scheme, the reinforcing fibers are matched with the modified carbon fibers in the filler, so that the effect of restricting crack expansion of the recycled coarse aggregate is achieved, meanwhile, the reinforcing fibers can achieve the effect of reinforcing the internal strength of the concrete, and the cracking strength of the concrete is improved. The reinforcing fiber is preferably carbon fiber subjected to surface modification treatment, and the carbon fiber is easier to disperse in a concrete system after the modification treatment, and has higher bonding performance with each component of the concrete.

In a second aspect, the present application provides a method for preparing recycled concrete, which adopts the following technical scheme:

the preparation method of the recycled concrete comprises the following steps:

s1, preparing recycled coarse aggregate: crushing and screening the waste concrete to obtain recycled aggregate particles with a specified particle size range;

s2, filling and modifying the recycled coarse aggregate: drying the recycled coarse aggregate particles, mixing the dried recycled coarse aggregate particles with a filler in a vacuum environment, and drying to obtain the filled and modified recycled coarse aggregate;

and S3, stirring and mixing the filled and modified recycled coarse aggregate, the reinforced fiber, the natural fine aggregate, the cement, the water reducing agent and the water to obtain the recycled concrete.

Optionally, in the step S2, the recycled coarse aggregate and the filler are stirred and mixed in a vacuum environment, the vacuum degree is 0.1-0.2 Mpa, and the reaction time is 0.5-2 h.

Optionally, in step S2, the drying temperature is 120-150 ℃ and the drying time is 1-2 h.

Through adopting above-mentioned technical scheme, after regeneration coarse aggregate and filler mix, through natural infiltration and regeneration coarse aggregate's adsorption, the filler part infiltration gets into regeneration coarse aggregate inside, and modified fiber, glass bead etc. in the filler fills into regeneration coarse aggregate's crack, surface pore simultaneously, further shutoff regeneration coarse aggregate's water absorption passageway, can form one deck rete on regeneration coarse aggregate surface after the gluey stickness material solidification in the filler further prevents regeneration coarse aggregate's water absorption. The osmotic filling effect of the filler can be improved by vacuum pressurizing and mixing.

In summary, the present application includes at least one of the following beneficial technical effects:

1. according to the technical scheme, the filler is used for filling and modifying the recycled coarse aggregate, so that microcracks and surface pores on the recycled coarse aggregate can be plugged to a certain extent, the porosity of the recycled coarse aggregate is reduced, meanwhile, the filler attached to the surface of the recycled coarse aggregate can further reduce the contact between the filler and external water, the water absorption rate of the recycled coarse aggregate is reduced through mutual cooperation, and the strength of recycled concrete is further improved.

2. In the technical scheme, the filler is prepared by compounding glass beads and modified carbon fibers with a silicate adhesive system, and the filler is filled into gaps and surface pores of the recycled coarse aggregate, so that the compression resistance of the recycled coarse aggregate can be enhanced on one hand, and on the other hand, the addition of the carbon fibers can play a role in restraining the crack expansion of the recycled coarse aggregate.

3. In the technical scheme, through carrying out plasma cleaning treatment to the carbon fiber, can improve the hydrophilicity on carbon fiber surface, simultaneously in plasma treatment process, can introduce certain active group at the carbon fiber surface through ionization, these active groups can take place substitution grafting reaction with other active components in the filler, promote the dispersibility between modified carbon fiber and other each components and with the link strength between the coarse aggregate of regeneration, promote the restraint effect to the coarse aggregate crack extension of regeneration.

Detailed Description

The present application is described in further detail below in connection with specific examples. In the following examples, no specific details are set forth, and the examples were conducted under conventional conditions or conditions recommended by the manufacturer; the raw materials used in the following examples were all commercially available from ordinary sources except for the specific descriptions.

Preparation of filler

Preparation example 1

Referring to the raw material ratios in table 1, a filler was prepared as follows:

s1, putting asphalt-based carbon fibers with the length range of 0.5-5 mm into a roller plasma cleaning machine, setting the temperature to 25 ℃, treating the asphalt-based carbon fibers with the process atmosphere of nitrogen and the discharge power of 300W for 30min to obtain modified carbon fibers;

s2, weighing sodium silicate according to the proportion, dissolving in water, stirring and mixing uniformly, then adding modified carbon fiber, nano silicon dioxide and glass beads with the particle size range of 30-80 mu m, and stirring and mixing uniformly to obtain the filler.

Preparation example 2

The preparation example differs from preparation example 1 only in the proportions of the raw materials, with specific reference to table 1, and the remainder remains the same as in example 1.

Preparation example 3

Preparation example 4

The present preparation example differs from preparation example 3 in that an equal amount of nanosilica was used instead of the modified carbon fiber, the remainder remaining in agreement with preparation example 1.

Preparation example 5

The present preparation example differs from preparation example 3 only in that an equal amount of modified carbon fiber was used instead of glass beads, and the rest was kept the same as preparation example 1.

Preparation example 6

The difference between this preparation and preparation 3 is that sodium silicate, nano silica and water are not added to the filler, and the rest is the same as preparation 1.

Preparation example 7

The difference between this preparation example and preparation example 3 is that glass beads and modified carbon fibers were not added, and the remainder was the same as in preparation example 1.

Preparation example 8

The difference between this preparation example and preparation example 3 is that the carbon fiber is not modified, and the rest remains the same as in preparation example 1.

Table 1: examples 1 to 3 raw material ratios (unit: kg)

	Silicate salt	Nano silicon dioxide	Modified carbon fiber	Glass bead	Water and its preparation method
						Preparation example 1	20	20	5	15	20
Preparation example 2	30	15	15	10	35
						Preparation example 3	25	18	10	12	25

Example 1

The raw material composition of the recycled concrete is shown in Table 2, and the concrete preparation method comprises the following steps:

s1, taking waste concrete, crushing, screening to obtain regenerated coarse aggregate particles with the particle size range of 5-15 mm, and drying to remove water;

s2, mixing the filler prepared in the preparation example 1 with the recycled coarse aggregate in a vacuum mixer, wherein the vacuum degree is 0.1MPa, the mixing time is 1h, and drying at 120 ℃ for 1h after filling is finished to obtain the filled modified recycled coarse aggregate;

s3, weighing the recycled coarse aggregate subjected to filling modification, carbon fiber with the average length of 20mm, natural fine aggregate with the fineness modulus of 2.0, cement, polycarboxylate water reducer and water according to the proportion, mixing and stirring uniformly to obtain the recycled concrete.

Example 2

The difference between this example and example 1 is that the raw material composition ratio is different, specifically referring to table 2, and the remainder remains the same as example 1.

Example 3

Table 2: examples 1 to 3 raw material composition (unit: kg)

Example 4

This example differs from example 3 in that the filler was prepared from preparation 2, the remainder remaining the same as example 3.

Example 5

This example differs from example 3 in that the filler was prepared from preparation 3, the remainder remaining identical to example 3.

Comparative example 1

This comparative example differs from example 1 in that no filler was added, and the remainder remained the same as example 1, comparative example 2

The comparative example was different from example 1 in that the filler was mixed with other raw materials, and the filler was not first filled into the surface and cracks of the recycled aggregate, and the remainder was the same as example 1.

Comparative example 3

This comparative example differs from example 1 in that no reinforcing fibers were added, and the remainder remained the same as example 1.

Performance detection

The recycled concrete prepared in examples and comparative examples was subjected to various performance tests, specifically as follows:

making a standard test block according to GB/T50081-2002 standard of a common concrete mechanical property test method, and measuring the compressive strength of the standard test blocks 7d and 28d and the cleavage resistance of the standard test block 28 d;

the water penetration depth of a standard test block is tested by referring to a water penetration height method in GB/T50082-2009 Standard for test method of ordinary concrete long-term Performance and durability.

The results of the performance measurements for examples 1 to 5 and comparative examples 1 to 3 are shown in Table 3 below.

Table 3: results of Performance measurements of examples 1 to 5 and comparative examples 1 to 3

As can be seen from the data in Table 3, the addition of the filler and the reinforcing fiber can well improve the water absorption of the recycled coarse aggregate, reduce the water absorption rate of the recycled coarse aggregate and improve the compressive strength and the cracking strength of the recycled concrete.

Examples 6 to 10

Examples 6 to 10 differ from example 5 in the source of the filler, specifically referring to table 4 below.

Table 4: examples 6 to 10 where filler source

Examples	Filler (B)
		Example 6	Preparation example 4
Example 7	Preparation example 5
		Example 8	Preparation example 6
Example 9	Preparation example 7
		Example 10	Preparation example 8

Example 11

The difference between this example and example 5 is that the glass beads have a particle size in the range of 100 to 120. Mu.m, and the remainder is the same as in example 5.

Example 12

The difference between this example and example 5 is that the glass beads have a particle size in the range of 10 to 30. Mu.m, and the remainder is the same as in example 5.

Implementation of the embodiments example 13

This example differs from example 5 in that the recycled coarse aggregate and the filler were mixed under normal pressure, and the remainder was the same as example 5.

The regenerated concrete produced in examples 6 to 13 was subjected to performance test, and the test results are shown in Table 5 below.

Table 5: examples 6 to 13 Performance test results

As can be seen from the data in table 5, the use of the modified carbon fiber, glass beads in the filler in combination with the silicate adhesive system reduces the water absorption of the recycled coarse aggregate by effectively filling the cracks and pores in the recycled coarse aggregate particles, and improves the strength of the recycled coarse aggregate by filling the carbon fiber with high-strength glass beads, and the modified carbon fiber is fixedly connected in the cracks of the recycled coarse aggregate by the adhesive, so that the re-expansion of the cracks on the surface of the recycled coarse aggregate can be restrained, and the cracking resistance and durability of the concrete are improved.

The foregoing are all preferred embodiments of the present application, and are not intended to limit the scope of the present application in any way, therefore: all equivalent changes in structure, shape and principle of this application should be covered in the protection scope of this application.

Claims

1. The recycled concrete is characterized by comprising the following raw materials in parts by weight:

65-80 parts of recycled coarse aggregate;

5-10 parts of filler;

3-10 parts of reinforcing fibers;

20-30 parts of natural fine aggregate;

25-30 parts of cement;

1-3 parts of a water reducing agent;

5-15 parts of water;

2. The recycled concrete according to claim 1, wherein the filler comprises the following raw materials in parts by weight:

20-30 parts of silicate;

15-20 parts of nano silicon dioxide;

5-15 parts of modified carbon fiber;

10-15 parts of glass beads;

20-35 parts of water.

3. A recycled concrete according to claim 2, wherein the modified carbon fiber is a carbon fiber subjected to a plasma surface treatment.

4. The recycled concrete of claim 2, wherein the glass beads have a particle size of 30-80 μm.

5. The recycled concrete of any one of claims 2 to 4, wherein the filler is prepared by:

s1, placing the raw carbon fiber in a roller plasma cleaner for modification treatment to obtain modified carbon fiber, wherein the treatment time is 30-60 min, the temperature is 25-30 ℃, and the discharge power is 200-400W;

6. The recycled concrete according to claim 1, wherein the recycled coarse aggregate has a particle size of 5-15 mm.

7. The recycled concrete of claim 1, wherein the natural fine aggregate has a fineness modulus of 2.0 to 3.0.

8. A recycled concrete according to claim 1, wherein the reinforcing fibers are one or both of glass fibers and carbon fibers.

9. The method for preparing recycled concrete according to any one of claims 1 to 8, comprising the steps of:

s1, preparing recycled coarse aggregate: crushing and screening the waste concrete to obtain recycled coarse aggregate particles with a specified particle size range;

10. The method for preparing recycled concrete according to claim 9, wherein in the step S2, the recycled coarse aggregate and the filler are stirred and mixed in a vacuum environment, the vacuum degree is 0.1-0.2 mpa, and the reaction time is 0.5-2 h.