CN112047688A - Recycled aggregate concrete and preparation method thereof - Google Patents
Recycled aggregate concrete and preparation method thereof Download PDFInfo
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- CN112047688A CN112047688A CN202010933429.1A CN202010933429A CN112047688A CN 112047688 A CN112047688 A CN 112047688A CN 202010933429 A CN202010933429 A CN 202010933429A CN 112047688 A CN112047688 A CN 112047688A
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
- C04B28/04—Portland cements
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B20/00—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
- C04B20/10—Coating or impregnating
- C04B20/1018—Coating or impregnating with organic materials
- C04B20/1029—Macromolecular compounds
- C04B20/1033—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
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- Inorganic Chemistry (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
Abstract
The application relates to the field of concrete, and particularly discloses recycled aggregate concrete and a preparation method thereof. The recycled aggregate concrete is prepared from the following raw materials in parts by weight: cement 270 + 290 parts; 80-100 parts of fly ash; 780 portions of sand and 810 portions; 800-820 parts of modified regenerated coarse aggregate; 180 portions of natural gravel and 200 portions of natural gravel; 8-10 parts of an additive; 150 portions and 160 portions of water; the modified recycled coarse aggregate is composed of a core body and a coating film, wherein the core body is recycled coarse aggregate, and the coating film is alkali-soluble resin; the preparation method comprises the following steps: weighing the raw materials according to the proportion; stirring and mixing natural macadam, sand, modified recycled coarse aggregate, cement and fly ash uniformly to obtain a first mixture; and uniformly mixing water and the additive, adding the mixture into the first mixture, and uniformly stirring to obtain the recycled aggregate concrete. The recycled aggregate concrete has the advantage of good fluidity; in addition, the preparation method has the advantages of simplicity, high efficiency and suitability for large-scale production.
Description
Technical Field
The application relates to the field of concrete, in particular to recycled aggregate concrete and a preparation method thereof.
Background
Along with the continuous progress of urban transformation, a large amount of construction waste is generated in the process of dismantling urban waste buildings, and concrete fragments are the largest constituent parts in the construction waste. Therefore, the recycling technology of the concrete fragments is very important to realize the resource utilization of the construction waste.
At present, waste concrete fragments are crushed, cleaned and graded to obtain recycled aggregate, the recycled aggregate is mixed with gradation according to a certain proportion, natural aggregates such as sand stones are partially or completely replaced, and cement, water and the like are added to prepare new concrete, so that the recycling of the concrete fragments is realized.
However, the recycled aggregate has more gaps than the natural aggregate and high water absorption rate, so that the slump of the recycled aggregate concrete is lower than that of the natural aggregate concrete under the condition of the same water cement ratio, and meanwhile, the friction force of the mixture during stirring and pouring is increased and the slump of the recycled aggregate concrete is further reduced due to the fact that the surface of the recycled aggregate is uneven and numerous edges and corners are formed.
In view of the above-mentioned related technologies, the inventors consider that concrete prepared by using recycled aggregate has disadvantages of small slump, poor fluidity and unfavorable construction in practical application.
Disclosure of Invention
In order to solve the problem that the flowability of recycled aggregate concrete is poor, the application provides recycled aggregate concrete and a preparation method thereof.
In a first aspect, the present application provides a recycled aggregate concrete, which adopts the following technical scheme:
the recycled aggregate concrete is prepared from the following raw materials in parts by weight:
cement 270 + 290 parts;
80-100 parts of fly ash;
780 portions of sand and 810 portions;
800-820 parts of modified regenerated coarse aggregate;
180 portions of natural gravel and 200 portions of natural gravel;
8-10 parts of an additive;
150 portions and 160 portions of water;
the modified recycled coarse aggregate is composed of a core body and a coating film, wherein the core body is recycled coarse aggregate, and the coating film is alkali-soluble resin.
By adopting the technical scheme, as the modified recycled coarse aggregate is adopted, the recycled coarse aggregate is subjected to film coating treatment, and the concave part on the surface of the recycled aggregate is filled, the roughness of the surface of the recycled aggregate is reduced, the friction force between the recycled coarse aggregate and other raw materials during stirring and pouring is further reduced, and the effect of enhancing the fluidity of recycled aggregate concrete is achieved; meanwhile, the surface sunken area of the recycled aggregate concrete is reduced, so that the water absorption of the recycled aggregate is reduced, the storage of fluid water in the fresh concrete is ensured, and the fluidity of the recycled aggregate concrete is further improved.
The alkali-soluble resin is adopted as the coating material, on one hand, the adhesion is good, the film forming toughness is good, and the alkali-soluble resin is not easy to separate from the recycled coarse aggregate in the concrete raw material prefabricating process, on the other hand, after the concrete is mixed, the cement in the concrete undergoes hydration reaction to gradually generate calcium hydroxide, so that the alkalinity of the system is gradually enhanced, the alkali-soluble resin coating film is gradually dissolved, the recycled coarse aggregate is in direct contact with the cementing material after the concrete is prepared for a period of time, the influence of the coating layer on the bonding of the recycled aggregate and the cementing material is reduced, the interface strength of the recycled coarse aggregate and the cementing material is ensured, the mechanical property of the recycled aggregate concrete is ensured while the fluidity of the recycled aggregate concrete is improved, and the application effect is good.
Preferably, the weight ratio of the recycled coarse aggregate to the alkali-soluble resin is 10: (0.2-0.3).
Through adopting above-mentioned technical scheme, through controlling the alkali-soluble resin quantity, guaranteeing that alkali-soluble resin can carry out fully under the prerequisite of filling to regeneration coarse aggregate surface depression, realize the control to alkali-soluble resin film forming thickness, and then realize clearing up the control of time spent to alkali-soluble resin for regeneration aggregate concrete when possessing preferred mobility and workability, mechanical properties also can obtain fully guaranteeing.
Preferably, the preparation method of the modified recycled coarse aggregate comprises the following steps:
s1, crushing and screening the waste concrete blocks to obtain coarse aggregate with the particle size of 5-25mm, and cleaning and drying the obtained coarse aggregate to obtain regenerated coarse aggregate;
s2, diluting the alkali-soluble resin with water 15-20 times of the weight of the alkali-soluble resin, wherein the water temperature of the water for dilution is 40-50 ℃ to obtain alkali-soluble resin diluent;
and S3, spraying the alkali soluble resin diluent obtained in the S2 on the surface of the recycled coarse aggregate obtained in the S1, and drying to obtain the modified recycled coarse aggregate.
By adopting the technical scheme, the alkali-soluble resin is diluted by water with the weight 15-20 times that of the alkali-soluble resin, so that the prepared alkali-soluble resin solution has low viscosity and good fluidity, can fully fill the pits on the surface of the recycled coarse aggregate, has moderate water content, can be dried quickly, and saves energy; the dilution temperature of adoption is convenient for dilute alkali-soluble resin on the one hand, and on the other hand makes the diluent viscosity after diluting lower, is convenient for spray and alkali-soluble resin levelling film forming, has guaranteed film forming quality.
The preparation method is simple and efficient, and the prepared modified recycled coarse aggregate is uniform in film covering, stable in quality and convenient for large-scale industrial production and application.
Preferably, the concrete block is shaped after being crushed in S1, and the shaped and sieved coarse aggregate is soaked in cement slurry, wherein the weight ratio of water to cement in the cement slurry is 1: (1-2), and the soaking time is 20-30 min.
Through adopting above-mentioned technical scheme, carry out the plastic through the concrete piece after to the breakage, reduced the edges and corners of concrete piece for the regeneration coarse aggregate grain type that makes is more mellow and more, has reduced the frictional force when regeneration coarse aggregate stirs and pours, and then has promoted the mobility of regeneration aggregate concrete.
The crushed coarse aggregate is soaked by cement slurry, so that the cement slurry is filled into cracks and pores on the coarse aggregate, the strength of the coarse aggregate is enhanced, the cracks on the coarse aggregate caused by reshaping are repaired, the influence of reshaping on the strength of the recycled coarse aggregate is reduced, and the mechanical property of the prepared recycled aggregate concrete is further ensured.
Preferably, before the coarse aggregate is soaked in the S1, the coarse aggregate is placed in a negative pressure environment of 0.04-0.07MPa and stands for 5-8 min.
By adopting the technical scheme, the coarse aggregate is subjected to negative pressure treatment before being soaked in the cement slurry, so that air in pores and cracks on the coarse aggregate is discharged, the cement slurry can be fully filled into the pores and cracks on the coarse aggregate during subsequent soaking, and the improvement effect on the strength of the coarse aggregate is improved.
Preferably, the alkali-soluble resin is an alkali-soluble polyester resin or an alkali-soluble acrylic resin.
By adopting the technical scheme, the alkali-soluble polyester resin and the alkali-soluble acrylic resin have proper viscosity, good fluidity and easy leveling, and have good filling performance and good use effect on the surface depression of the recycled coarse aggregate.
Preferably, the alkali-soluble resin is an alkali-soluble acrylic resin.
By adopting the technical scheme, the alkali-soluble acrylic resin is more sensitive to the change of the pH value of the environment, so that the alkali-soluble acrylic resin can be conveniently controlled when the film covering of the alkali-soluble resin is cleared up by controlling the weight of the alkali-soluble resin, the alkali-soluble acrylic resin can be conveniently adjusted according to the actual application requirements, and the alkali-soluble acrylic resin is convenient for large-scale industrial production.
Preferably, the alkali-soluble resin is polyacrylic acid resin III.
By adopting the technical scheme, the polyacrylic resin III is used as the recycled coarse aggregate film-coated material, and the dissolution pH of the polyacrylic resin III is about 8 and is close to the pH of concrete mixing for 1-2h, so that the prepared recycled aggregate concrete can keep higher fluidity during mixing and pouring, and the recycled aggregate can be quickly combined with the cementing material after pouring is finished, thereby being beneficial to practical production and use.
In a second aspect, the application provides a preparation method of recycled aggregate concrete, which adopts the following technical scheme:
a preparation method of recycled aggregate concrete comprises the following steps:
step one, weighing raw materials according to a ratio;
step two, mixing and uniformly stirring cement, fly ash, sand, modified recycled coarse aggregate and natural macadam to obtain a first mixture;
and step three, uniformly mixing water and the additive, adding the mixture into the first mixture, and uniformly stirring to obtain the recycled aggregate concrete.
By adopting the technical scheme, the preparation method is simple and efficient, is suitable for large-scale production and use, and the prepared recycled aggregate concrete is good in flowability, good in workability and convenient to construct.
In summary, the present application has the following beneficial effects:
1. according to the method, the alkali-soluble resin is adopted to carry out film coating modification treatment on the recycled aggregate, so that the smoothness of the surface of the recycled aggregate is improved, the water absorption of the recycled aggregate is reduced, the fluidity of the prepared recycled aggregate concrete is enhanced, the influence on the interface combination part of the recycled coarse aggregate and the cementing material is small, and the mechanical property of the recycled aggregate concrete is ensured;
2. according to the method, the crushed concrete blocks are shaped, so that the prepared regenerated coarse aggregate particles are more round, the fluidity of the regenerated aggregate concrete is improved, the crushed coarse aggregate is soaked by cement slurry, cracks on the coarse aggregate caused by shaping are repaired, and the mechanical property of the regenerated aggregate concrete is ensured;
3. the method is simple and efficient, is suitable for large-scale production and use, and the prepared recycled aggregate concrete is good in flowability, good in workability and convenient to construct.
Detailed Description
The present application will be described in further detail with reference to examples.
The waste concrete blocks referred to in the following are obtained from concrete construction waste and have an apparent density of 2380-3The crushing index is 13.0-16.8%, the water content is 1.85-2.52%, and the water absorption is 3.75-5.12%. The rest of the raw material information is shown in table 1.
Table 1 raw material information table
Preparation example of modified recycled coarse aggregate
Preparation example 1
S1, preparing a recycled coarse aggregate, putting the waste concrete blocks into a jaw crusher for crushing, then screening by a vibrating screen machine to obtain a coarse aggregate with the grain size of 5-25mm and continuous gradation, spraying and cleaning the obtained coarse aggregate, and then naturally airing to obtain the recycled coarse aggregate;
s2, preparing an alkali-soluble resin diluent, weighing a vinyl ester resin with the weight being 2% of the weight of the recycled coarse aggregate, diluting the weighed vinyl ester resin with water with the weight being 15 times of the weight of the vinyl ester resin, wherein the water temperature of the dilution water is 40 ℃, so as to obtain a vinyl ester resin diluent;
and S3, conveying the regenerated coarse aggregate obtained in the step S1 to a mesh belt type conveyor belt, enabling the regenerated coarse aggregate to be flatly laid on the mesh belt type conveyor belt, driving the regenerated coarse aggregate to pass through a spray head for spraying the vinyl ester resin diluent obtained in the step S2 by the mesh belt type conveyor belt, spraying the vinyl ester resin diluent on the surface of the regenerated coarse aggregate, and then driving the regenerated coarse aggregate to pass through a hot air drying box for hot air drying at 65 ℃ to obtain the modified regenerated coarse aggregate.
Preparation example 2
The present preparation example differs from preparation example 1 in that the alkali-soluble resin used is a BT-9 type aqueous alkali-soluble acrylic resin.
Preparation example 3
The present preparation example differs from preparation example 1 in that the alkali-soluble resin used is polyacrylic acid resin iii.
Preparation example 4
S1, preparing a recycled coarse aggregate, putting the waste concrete blocks into a jaw crusher for crushing, then screening by a vibrating screen machine to obtain a coarse aggregate with the grain size of 5-25mm and continuous gradation, spraying and cleaning the obtained coarse aggregate, and then naturally airing to obtain the recycled coarse aggregate;
s2, preparing alkali-soluble resin diluent, weighing polyacrylic resin III with the weight being 2.5% of the weight of the recycled coarse aggregate, diluting the weighed polyacrylic resin III with water with the weight being 18 times that of the polyacrylic resin III, wherein the water temperature of the water for dilution is 45 ℃, and obtaining polyacrylic resin III diluent;
and S3, conveying the regenerated coarse aggregate obtained in the step S1 to a mesh belt type conveyor belt, enabling the regenerated coarse aggregate to be flatly laid on the mesh belt type conveyor belt, driving the regenerated coarse aggregate to pass through a spray head for spraying polyacrylic resin III diluent obtained in the step S2 by the mesh belt type conveyor belt, spraying the polyacrylic resin III diluent on the surface of the regenerated coarse aggregate, and then driving the regenerated coarse aggregate to pass through a hot air drying box for hot air drying at 70 ℃ to obtain the modified regenerated coarse aggregate.
Preparation example 5
S1, preparing a recycled coarse aggregate, putting the waste concrete blocks into a jaw crusher for crushing, then screening by a vibrating screen machine to obtain a coarse aggregate with the grain size of 5-25mm and continuous gradation, spraying and cleaning the obtained coarse aggregate, and then naturally airing to obtain the recycled coarse aggregate;
s2, preparing an alkali-soluble resin diluent, weighing polyacrylic resin III with the weight being 3% of the weight of the recycled coarse aggregate, diluting the weighed polyacrylic resin III with water with the weight being 20 times that of the polyacrylic resin III, wherein the water temperature of the water for dilution is 50 ℃, and thus obtaining a polyacrylic resin III diluent;
and S3, conveying the regenerated coarse aggregate obtained in the step S1 to a mesh belt type conveyor belt, enabling the regenerated coarse aggregate to be flatly laid on the mesh belt type conveyor belt, driving the regenerated coarse aggregate to pass through a spray head for spraying polyacrylic resin III diluent obtained in the step S2 by the mesh belt type conveyor belt, spraying the polyacrylic resin III diluent on the surface of the regenerated coarse aggregate, and then driving the regenerated coarse aggregate to pass through a hot air drying box for hot air drying at 75 ℃ to obtain the modified regenerated coarse aggregate.
Preparation example 6
The difference from preparation example 4 is that: and the weight of the polyacrylic resin III weighed in the S2 is 1 percent of the weight of the recycled coarse aggregate.
Preparation example 7
The difference from preparation example 4 is that: and the weight of the polyacrylic resin III weighed in the S2 is 4% of the weight of the recycled coarse aggregate.
Preparation example 8
The difference from preparation example 4 is that: s1, preparing a regenerated coarse aggregate, putting the waste concrete blocks into a jaw crusher for coarse crushing, then putting the waste concrete blocks into a shaping machine for fine crushing and shaping, screening the waste concrete blocks by a vibrating screen machine to obtain the coarse aggregate with the grain size of 5-25mm and continuous gradation, then putting the obtained coarse aggregate into a cement slurry pool for soaking for 20 minutes, wherein the weight ratio of water to cement in the cement slurry is 1:1, fishing out the coarse aggregate for spray washing after soaking is finished, and then naturally airing to obtain the regenerated coarse aggregate.
Preparation example 9
The difference from preparation example 4 is that: s1, preparing a regenerated coarse aggregate, putting the waste concrete blocks into a jaw crusher for coarse crushing, then putting the waste concrete blocks into a shaping machine for fine crushing and shaping, screening the waste concrete blocks by a vibrating screen machine to obtain the coarse aggregate with the grain size of 5-25mm and continuous gradation, then putting the obtained coarse aggregate into a cement slurry pool for soaking for 30 minutes, wherein the weight ratio of water to cement in the cement slurry is 1:2, fishing out the coarse aggregate after soaking, spraying and washing, and then naturally airing to obtain the regenerated coarse aggregate.
Preparation example 10
The difference from preparation example 4 is that: s1, preparing a recycled coarse aggregate, putting the waste concrete blocks into a jaw crusher for coarse crushing, then putting the waste concrete blocks into a shaping machine for fine crushing and shaping, screening the waste concrete blocks by a vibrating screen machine to obtain a coarse aggregate with the grain size of 5-25mm and continuous gradation, spraying and cleaning the obtained coarse aggregate, and then naturally airing to obtain the recycled coarse aggregate.
Preparation example 11
The difference from preparation example 4 is that: s1, preparing a regenerated coarse aggregate, putting the waste concrete blocks into a jaw crusher for coarse crushing, then putting the waste concrete blocks into a shaping machine for fine crushing and shaping, screening the waste concrete blocks by a vibrating screen machine to obtain the coarse aggregate with the grain size of 5-25mm and continuous gradation, putting the coarse aggregate into a storage tank, forcibly pumping the pressure in the storage tank to a negative pressure environment of 0.04Mpa by using a vacuum pump for 5 minutes, then directly putting the coarse aggregate in the storage tank into a cement slurry pool for soaking for 30 minutes, wherein the weight ratio of water to cement in the cement slurry is 1:2, fishing out the coarse aggregate for spray washing after soaking is finished, and naturally airing to obtain the regenerated coarse aggregate.
Preparation example 12
The difference from preparation example 4 is that: s1, preparing a regenerated coarse aggregate, putting the waste concrete blocks into a jaw crusher for coarse crushing, then putting the waste concrete blocks into a shaping machine for fine crushing and shaping, screening the waste concrete blocks by a vibrating screen machine to obtain the coarse aggregate with the grain size of 5-25mm and continuous gradation, putting the coarse aggregate into a storage tank, forcibly pumping the pressure in the storage tank to a negative pressure environment of 0.07Mpa by using a vacuum pump for 8 minutes, then directly putting the coarse aggregate in the storage tank into a cement slurry pool for soaking for 30 minutes, wherein the weight ratio of water to cement in the cement slurry is 1:2, fishing out the coarse aggregate for spray washing after soaking is finished, and naturally airing to obtain the regenerated coarse aggregate.
Examples
Example 1
The recycled aggregate concrete comprises the following raw materials in parts by weight shown in Table 2, and is prepared by the following steps:
step one, weighing raw materials according to a ratio, wherein the modified recycled coarse aggregate is prepared by the preparation example 1;
sequentially adding the natural macadam, the sand, the modified recycled coarse aggregate, the cement and the fly ash into a forced concrete mixer, stirring for 90s, and uniformly mixing to obtain a first mixture;
and step three, uniformly mixing the water and the additive, adding the mixture into a forced concrete stirring tank filled with the first mixture, and uniformly stirring for 30 seconds to obtain the recycled aggregate concrete.
Example 2
A recycled aggregate concrete is different from the concrete of example 1 in that the raw material components and the corresponding weights thereof are shown in Table 2, and a modified recycled coarse aggregate is prepared by the preparation example 2;
example 3
A recycled aggregate concrete was different from example 1 in that the raw material components and the respective weights thereof were as shown in Table 2, and a modified recycled coarse aggregate was obtained in production example 3.
TABLE 2 example 1 raw material components and their weights (kg)
| Example 1 | Example 2 | Example 3 | |
| Cement | 270 | 280 | 290 |
| Fly ash | 100 | 90 | 80 |
| Sand | 780 | 795 | 810 |
| Natural macadam | 180 | 190 | 200 |
| Additive agent | 8 | 9 | 10 |
| Water (W) | 150 | 155 | 160 |
| Modified recycled coarse aggregate | 800 | 810 | 820 |
Example 4
A recycled aggregate concrete, which is different from example 2 in that a modified recycled coarse aggregate was prepared according to preparation example 4.
Example 5
A recycled aggregate concrete was different from example 2 in that a modified recycled coarse aggregate was obtained from preparation example 5.
Example 6
A recycled aggregate concrete, which is different from example 2 in that a modified recycled coarse aggregate was prepared in preparation example 6.
Example 7
A recycled aggregate concrete which is different from example 2 in that a modified recycled coarse aggregate was prepared by preparation example 7.
Example 8
A recycled aggregate concrete which is different from example 2 in that a modified recycled coarse aggregate was prepared by preparation example 8.
Example 9
A recycled aggregate concrete which is different from example 2 in that a modified recycled coarse aggregate was prepared in production example 9.
Example 10
A recycled aggregate concrete which is different from example 2 in that a modified recycled coarse aggregate was prepared in production example 10.
Example 11
A recycled aggregate concrete which is different from example 2 in that a modified recycled coarse aggregate was prepared in production example 11.
Example 12
A recycled aggregate concrete which is different from example 2 in that a modified recycled coarse aggregate was prepared in production example 12.
Comparative example
Comparative example 1
A recycled aggregate concrete, which is different from example 2 in that the modified recycled coarse aggregate was not added, but the recycled coarse aggregate prepared in S1 of preparation example 2 was directly added.
Performance test
Test slump test
The slump was determined by tapping according to the description in section 3.1 of the general concrete mixture Property test methods Standard (GB/T50080-2002).
Test samples: the concrete mixtures obtained in examples 1 to 12 were used as test samples 1 to 12, and the concrete mixture obtained in comparative example 1 was used as control sample 1.
The test method comprises the following steps: a horn-shaped slump bucket with an upper opening of 100mm, a lower opening of 200mm and a height of 300mm is respectively filled with test samples 1-12 and a control sample 1, each sample is filled for three times, a tamping hammer is used for uniformly impacting 25 times along the wall of the bucket from outside to inside after each filling, and after tamping, the samples are leveled. And pulling up the barrel, and subtracting the height of the highest point of the concrete after collapse by using the height of the barrel to obtain a difference value, namely the slump.
And (3) test results: the test results of the test samples 1 to 12 and the control sample 1 are shown in Table 3.
Test second slump 1h time-dependent change test
The amount of change with time in slump was measured according to the method for measuring the amount of change with time in slump of 1h described in section 6.5.1.2 of concrete admixtures (GB 8076-2008).
Test samples: the concrete mixtures obtained in examples 1 to 12 were used as test samples 1 to 12, and the concrete mixture obtained in comparative example 1 was used as control sample 1.
The test method comprises the following steps: the prepared recycled aggregate concrete was put into a sample cylinder which was wiped with a wet cloth, the container was covered, left to stand for 1 hour (calculated from the time of stirring with water), poured out, turned over with a spade on an iron plate until uniform, and then slump was measured according to the test one measurement method described above. And calculating the difference value between the machine time and the slump after 1h to obtain the time-varying slump.
And (3) test results: the test results of the test samples 1 to 12 and the control sample 1 are shown in Table 3.
Test three compression strength test
The 28d compressive strength (MPa) of the recycled aggregate concrete is detected according to a cubic compressive strength test recorded in 6.0.4 part of Standard test methods for mechanical Properties of ordinary concrete (GB/T50081-2002).
Test samples: the recycled aggregate concrete prepared in examples 1 to 12 and comparative example 1 was prepared into a concrete standard cubic test piece according to the requirement of the compression test, and the test piece was cured in a standard curing room until the specified age, and then the compression test was carried out. Among them, test pieces prepared from the concrete mixtures obtained in examples 1 to 12 were used as test samples 1 to 12, and test pieces prepared from the concrete mixtures obtained in comparative example 1 were used as control sample 1.
The test instrument: pressure testing machine
And (3) test results: the test results of the test samples 1 to 12 and the control sample 1 are shown in Table 3.
TABLE 3 test results record table
| Slump/mm of discharge machine | Slump 1h change with time/mm | Compressive strength/Mpa | |
| Test sample 1 | 125 | 10 | 40.8 |
| Test sample 2 | 130 | 10 | 40.9 |
| Test sample 3 | 130 | 10 | 41.2 |
| Test sample 4 | 135 | 10 | 41.0 |
| Test sample 5 | 140 | 5 | 40.8 |
| Test sample 6 | 95 | 10 | 41.1 |
| Test sample 7 | 140 | 5 | 40.3 |
| Test sample 8 | 145 | 5 | 41.0 |
| Test sample 9 | 145 | 5 | 41.3 |
| Test sample 10 | 145 | 5 | 38.8 |
| Test sample 11 | 145 | 5 | 43.8 |
| Test sample 12 | 145 | 5 | 44.2 |
| Control sample 1 | 90 | 10 | 41.2 |
It can be seen from the combination of examples 1 to 3 and comparative example 1 and the combination of table 3 that the slump of the recycled aggregate concrete prepared by using the modified recycled coarse aggregate is significantly improved, which indicates that after the recycled coarse aggregate is subjected to film coating treatment and the concave part on the surface of the recycled aggregate is filled, the roughness of the surface of the recycled aggregate is reduced, so that the friction with other raw materials during the pouring of the recycled aggregate is reduced, and the fluidity of the recycled aggregate concrete is enhanced. The compressive strength of the recycled aggregate concrete prepared by adopting the modified recycled coarse aggregate is not obviously reduced, which shows that the alkali-soluble resin coating of the recycled coarse aggregate has small influence on the combination of the recycled aggregate and the cementing material, even when the alkali-soluble resin adopts polyacrylic resin III, the alkali-soluble resin basically has no influence on the combination of the recycled aggregate and the cementing material, and further shows that the alkali-soluble resin can be dissolved in a concrete system, and the dissolving effect on the polyacrylic resin III is the best, namely the polyacrylic resin III is the most sensitive to the change of the environmental pH.
It can be seen from the combination of examples 3 to 7 and table 3 that, when the weight of the alkali-soluble resin used is small, although the slump of the recycled aggregate concrete can be improved, the improvement range is small and the practical value is small; when the weight of the alkali soluble resin is excessive, the slump of the recycled aggregate concrete is not continuously improved, and the compressive strength is also reduced, which shows that when the alkali soluble resin layer is too thick, the total digestion is prolonged, so that the bonding degree of the cementing material and the recycled aggregate is reduced, and further the compressive strength is reduced.
It can be seen by combining example 4 and examples 8-10 and combining table 3 that after the concrete blocks obtained by crushing are shaped, the slump of the recycled aggregate concrete is obviously improved, which shows that the grain type of the coarse aggregate is also one of the important factors influencing the slump of the prepared recycled aggregate concrete, namely, the slump of the recycled aggregate concrete can be increased by the regular grain type of the coarse aggregate, and by comparing example 10 with examples 8 and 9, the strength of the coarse aggregate is reduced by shaping the coarse aggregate, and the damage to the coarse aggregate caused by shaping can be effectively compensated by the cement slurry soaking treatment with a proper water-cement ratio, so that the performance of the recycled aggregate concrete is improved.
It can be seen from the combination of examples 4, 11 and 12 and table 3 that the negative pressure treatment before the cement slurry soaking of the shaped coarse aggregate can effectively enhance the reinforcing effect of the cement slurry on the coarse aggregate, which means that the negative pressure treatment can exhaust air in pores and cracks on the coarse aggregate, thereby facilitating the filling of the cement slurry into the pores and cracks on the coarse aggregate and enhancing the improvement effect on the strength of the coarse aggregate.
The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.
Claims (9)
1. The recycled aggregate concrete is characterized by being prepared from the following raw materials in parts by weight:
cement 270 + 290 parts;
80-100 parts of fly ash;
780 portions of sand and 810 portions;
800-820 parts of modified regenerated coarse aggregate;
180 portions of natural gravel and 200 portions of natural gravel;
8-10 parts of an additive;
150 portions and 160 portions of water;
the modified recycled coarse aggregate is composed of a core body and a coating film, wherein the core body is recycled coarse aggregate, and the coating film is alkali-soluble resin.
2. The recycled aggregate concrete according to claim 1, characterized in that: the weight ratio of the recycled coarse aggregate to the alkali-soluble resin is 10: (0.2-0.3).
3. The recycled aggregate concrete according to claim 2, characterized in that: the preparation method of the modified recycled coarse aggregate comprises the following steps:
s1, crushing and screening the waste concrete blocks to obtain coarse aggregate with the particle size of 5-25mm, and cleaning and drying the obtained coarse aggregate to obtain regenerated coarse aggregate;
s2, diluting the alkali-soluble resin with water 15-20 times of the weight of the alkali-soluble resin, wherein the water temperature of the water for dilution is 40-50 ℃ to obtain alkali-soluble resin diluent;
and S3, spraying the alkali soluble resin diluent obtained in the S2 on the surface of the recycled coarse aggregate obtained in the S1, and drying to obtain the modified recycled coarse aggregate.
4. The recycled aggregate concrete according to claim 3, wherein: and S1, crushing the concrete block, shaping, and soaking the shaped and screened coarse aggregate by using cement slurry, wherein the weight ratio of water to cement in the cement slurry is 1: (1-2), and the soaking time is 20-30 min.
5. The recycled aggregate concrete according to claim 4, wherein: and (8) before the coarse aggregate is soaked in the S1, placing the coarse aggregate in a negative pressure environment of 0.04-0.07MPa and standing for 5-8 min.
6. The recycled aggregate concrete according to claim 1, characterized in that: the alkali-soluble resin is an alkali-soluble polyester resin or an alkali-soluble acrylic resin.
7. The recycled aggregate concrete according to claim 6, wherein: the alkali-soluble resin is an alkali-soluble acrylic resin.
8. The recycled aggregate concrete according to claim 7, wherein: the alkali soluble resin is polyacrylic resin III.
9. The method for preparing recycled aggregate concrete according to claims 1 to 8, comprising the steps of:
step one, weighing raw materials according to a ratio;
step two, stirring and mixing the natural macadam, the sand, the modified recycled coarse aggregate, the cement and the fly ash uniformly to obtain a first mixture;
and step three, uniformly mixing water and the additive, adding the mixture into the first mixture, and uniformly stirring to obtain the recycled aggregate concrete.
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| CN111423174A (en) * | 2020-03-24 | 2020-07-17 | 西安顺通建材有限责任公司 | Recycled concrete and preparation method thereof |
| CN112430043A (en) * | 2020-12-11 | 2021-03-02 | 深圳市恒星建材有限公司 | High polymer environment-friendly recycled concrete and preparation method thereof |
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