CN113429178B - Freeze-thaw resistant recycled concrete and preparation method thereof - Google Patents
Freeze-thaw resistant recycled concrete and preparation method thereof Download PDFInfo
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- CN113429178B CN113429178B CN202110819970.4A CN202110819970A CN113429178B CN 113429178 B CN113429178 B CN 113429178B CN 202110819970 A CN202110819970 A CN 202110819970A CN 113429178 B CN113429178 B CN 113429178B
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
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- 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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- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B16/00—Use of organic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of organic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B16/04—Macromolecular compounds
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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
- C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B18/04—Waste materials; Refuse
- C04B18/16—Waste materials; Refuse from building or ceramic industry
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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
- C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B18/04—Waste materials; Refuse
- C04B18/18—Waste materials; Refuse organic
- C04B18/20—Waste materials; Refuse organic from macromolecular compounds
- C04B18/22—Rubber, e.g. ground waste tires
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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
- C04B20/1051—Organo-metallic compounds; Organo-silicon compounds, e.g. bentone
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
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- C04B24/00—Use of organic materials as active ingredients for mortars, concrete or artificial stone, e.g. plasticisers
- C04B24/24—Macromolecular compounds
- C04B24/28—Macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
- C04B24/32—Polyethers, e.g. alkylphenol polyglycolether
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
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- 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
- C04B28/24—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 alkyl, ammonium or metal silicates; containing silica sols
- C04B28/26—Silicates of the alkali metals
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- 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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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
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Abstract
The invention discloses freeze-thaw cycle resistant recycled concrete and a preparation method thereof. The freeze-thaw cycle resistant recycled concrete is prepared from the following raw materials: the concrete comprises portland cement, fine aggregate, coarse aggregate, water, a water reducing agent, an air entraining agent and rubber powder, wherein the fine aggregate comprises organic silicon resin modified recycled fine aggregate, and the coarse aggregate comprises organic silicon resin modified recycled coarse aggregate; the rubber powder and the air entraining agent provide an expansion space for free water expansion in the recycled concrete, the expansion stress in the recycled concrete is reduced, meanwhile, the surface of the recycled aggregate is coated by the organic silicon resin, the water absorption of the recycled aggregate is reduced, the freeze-thaw resistance of the recycled concrete is improved, and the modified recycled aggregate is tightly connected with a cement gel system, so that the recycled concrete is compact in the interior, and the compressive strength of the recycled concrete is enhanced.
Description
Technical Field
The invention relates to the technical field of building materials, in particular to freeze-thaw resistant recycled concrete and a preparation method thereof.
Background
The development of the construction industry is often accompanied by the production of large quantities of construction waste. The building waste mainly refers to a large amount of waste cement blocks generated in the process of dismantling waste buildings, and as the cement blocks contain a large amount of calcium oxide and other components inside, the cement blocks can change the acidity and alkalinity of soil after being contacted with the soil for a long time, so that the property of the soil is changed, and therefore the waste cement blocks cannot be buried on the spot and are difficult to treat.
At present, the construction industry is gradually trying to recycle waste cement blocks: the waste cement blocks are crushed into recycled aggregates with different particle sizes, and the recycled aggregates can be mixed with cement and water to prepare concrete again through hydration reaction. However, compared with artificial sand aggregate, the recycled aggregate has the characteristics of high water absorption rate, low apparent density and higher water content due to the fact that residual slurry is adhered to the surface of the recycled aggregate, so that the recycled concrete prepared from the recycled aggregate is easy to crystallize and expand in free water in a low-temperature environment, the expansion pressure in a recycled concrete test piece is higher, cracks are generated, the surface of the recycled concrete shows cracking, stripping, falling and other phenomena after the test piece is subjected to repeated freeze-thaw cycles, the freeze-thaw resistance of the recycled concrete is poor, and the development and application of the recycled concrete in the building industry are severely restricted.
Disclosure of Invention
In order to improve the freeze-thaw resistance of the recycled concrete, the application provides the freeze-thaw resistance recycled concrete and a preparation method thereof.
In a first aspect, the application provides a freeze-thaw resistant recycled concrete, which is realized by adopting the following technical scheme:
the freeze-thaw resistant circulating recycled concrete is prepared from the following raw materials in parts by weight:
the fine aggregate comprises organic silicon resin modified recycled fine aggregate and natural fine aggregate, and the organic silicon resin modified recycled fine aggregate accounts for 20-100 wt% of the total weight of the fine aggregate; the coarse aggregate comprises organic silicon resin modified recycled coarse aggregate and natural coarse aggregate, and the organic silicon resin modified recycled coarse aggregate accounts for 20-100 wt% of the total weight of the coarse aggregate.
Through adopting above-mentioned technical scheme, the rubber powder is the elasticity powder that the surface has cellular structure, and the rubber powder includes but not limited to abandonment tire rubber powder, polyurethane elastic rubber powder, and the rubber powder has hydrophobicity, and in the process of mixing with the concrete, there is a large amount of bubbles in its interface department with the cement gel, and air-entraining agent makes these bubbles become tiny, seal and stable, and the inside infiltration passageway of recycled concrete has been blocked along with the cement hardening to the bubble. The rubber powder and the air entraining agent act together, when the recycled concrete is subjected to freeze-thaw cycle, the space generated after the rubber powder is extruded and the air bubbles are free water expansion to provide space, so that the expansion pressure is reduced, and the freeze-thaw resistance of the recycled concrete is improved;
but because of the existence of the air bubbles, the interface of the rubber powder and the cement gel system in the recycled concrete is the weak point of the recycled concrete mechanics, therefore, in the application, the regenerated coarse aggregate and the regenerated fine aggregate (the regenerated coarse aggregate and the regenerated fine aggregate are collectively called as regenerated aggregate) are modified by using the organic silicon resin, the surface of the regenerated aggregate is coated with the organic silicon resin, a layer of relatively uniform hydrophobic organic silicon resin film is formed on the recycled aggregate, so that the water absorption of the recycled aggregate is reduced, the freeze-thaw resistance of the recycled concrete is improved, the compatibility between the recycled aggregate modified by the organic silicon resin and the rubber powder is improved, the rubber powder is attached to the surface of the recycled aggregate, the organic silicon resin coated on the surface of the recycled aggregate is closely connected with a cement gel system through H-Si, the interior of the recycled concrete is compact, and the compressive strength of the recycled concrete is enhanced.
In addition, the organic silicon resin modified recycled fine aggregate and the organic silicon resin modified recycled coarse aggregate are obtained by recycling waste cement building blocks, and the rubber powder is waste obtained by recycling.
Preferably, the silicone resin modified recycled coarse aggregate and the silicone resin modified recycled fine aggregate are prepared by the following preparation steps: the method comprises the steps of crushing, particle shaping, cleaning and drying waste cement blocks recovered from waste buildings to obtain recycled aggregate, soaking the recycled aggregate into organic silicon resin emulsion with the concentration of 1-4 wt%, uniformly stirring, drying, and screening to obtain organic silicon resin modified recycled coarse aggregate and organic silicon resin modified recycled fine aggregate.
By adopting the technical scheme, the organic silicon resin in the organic silicon resin emulsion comprises but is not limited to a silane coupling agent, part of the organic silicon resin enters the pores in the recycled aggregate in the process of modifying the recycled aggregate, and the pores of the recycled aggregate are filled, so that the surface of the recycled aggregate is more complete, and the compressive strength of recycled concrete is improved.
Preferably, the concentration of the silicone resin emulsion is 2 wt%.
Preferably, the organic silicon resin modified recycled fine aggregate accounts for 35wt% of the total weight of the fine aggregate, and the organic silicon resin modified recycled coarse aggregate accounts for 75wt% of the total weight of the coarse aggregate.
By adopting the technical scheme, the compressive strength of the recycled concrete is not influenced by the organic silicon resin modified recycled fine aggregate and the organic silicon resin modified recycled coarse aggregate under the mixing amount, and meanwhile, the recycled concrete has better freeze-thaw resistance.
Preferably, the particle size range of the rubber powder is 20-60 meshes.
By adopting the technical scheme, the particle size of the rubber powder is controlled within the range, so that the possibility of agglomeration of the rubber powder can be reduced, the content of bubbles at the interface of the rubber powder and a cement gel system can be reduced, the generation of bubbles at the interface can be reduced, and the compressive strength of the recycled concrete can be improved.
Preferably, the air entraining agent is fatty alcohol-polyoxyethylene ether.
By adopting the technical scheme, the hydrophobic end of the fatty alcohol-polyoxyethylene ether is easy to crosslink and wind the organic silicon resin on the surface of the recycled aggregate, and the hydrophilic end of the fatty alcohol-polyoxyethylene ether is easy to adsorb inorganic cement particles, so that the cement particles are fully dispersed around the recycled aggregate, bubbles between a cement gel system and the recycled aggregate modified by the organic silicon resin are tiny, and the compressive strength and the freeze-thaw resistance of the recycled concrete are further improved.
Preferably, the raw material also comprises liquid sodium silicate, and the weight part of the liquid sodium silicate is 40-60.
By adopting the technical scheme, the liquid sodium silicate promotes the hydration of the portland cement, so that free water in the recycled concrete is converted into bound water as far as possible, and the freeze-thaw resistance of the recycled concrete is improved.
Preferably, the weight ratio of the portland cement to water is 0.45.
Preferably, the water reducing agent is a polycarboxylate water reducing agent.
By adopting the technical scheme, under the combined action of the water-cement ratio and the water reducing agent, the addition of water is reduced, so that the freeze-thaw resistance of the recycled concrete is improved.
In a second aspect, the application provides a preparation method of freeze-thaw cycle resistant recycled concrete, which adopts the following technical scheme: a preparation method of freeze-thaw resistant recycled concrete comprises the following steps: weighing Portland cement, fine aggregate, coarse aggregate, water, a water reducing agent, an air entraining agent and rubber powder according to the formula ratio, and stirring and blending to obtain the freeze-thaw resistant circulating recycled concrete.
By adopting the technical scheme, the prepared recycled concrete has high compressive strength and better freeze-thaw resistance.
In summary, the present application has the following beneficial effects:
1. rubber powder and air entraining agent provide the expansion space for the free water expansion in the recycled concrete in this application, reduce the inside expansion stress of recycled concrete, use organic silicon resin cladding recycled aggregate surface simultaneously, reduce the water absorption of recycled aggregate, improve the freeze-thaw resistance of recycled concrete, make closely linking to each other between aggregate and the cement gel system simultaneously for the inside compactness of recycled concrete has strengthened the compressive strength of recycled concrete.
2. Recycled aggregate and rubber powder used in the application are waste materials, the application realizes waste recycling, and construction cost is saved.
3. According to the application, the fatty alcohol-polyoxyethylene ether is used, the hydrophobic end of the fatty alcohol-polyoxyethylene ether is easy to crosslink and wind the organic silicon resin on the surface of the recycled aggregate, and the hydrophilic end of the fatty alcohol-polyoxyethylene ether is easy to adsorb inorganic cement particles, so that the cement particles are fully dispersed around the recycled aggregate, bubbles between a cement gel system and the recycled aggregate modified by the organic silicon resin are small, and the compressive strength and the freeze-thaw resistance of the recycled concrete are further improved.
4. Liquid sodium silicate has still been added in this application, and liquid sodium silicate promotes portland cement's hydration effect for free water in the recycled concrete converts the bound water into as far as possible, promotes recycled concrete's anti freeze-thaw performance.
Detailed Description
Unless otherwise specified, the raw material sources of the following preparation examples, examples and comparative examples are shown in table 1 below.
TABLE 1 sources of raw materials
Note: the waste cement building blocks are recovered from a certain waste building in Yongjia county in Zhejiang.
Preparation examples of Silicone resin-modified recycled coarse aggregate and Silicone resin-modified recycled Fine aggregate
Preparation example 1
An organic silicon resin modified recycled coarse aggregate and an organic silicon resin modified recycled fine aggregate are prepared according to the following steps:
putting the waste cement building blocks into a crusher to crush the waste cement building blocks to aggregate with the maximum particle size of not more than 31.5mm, putting the aggregate into a 5X series gravel shaping machine production machine sand making device, wherein the linear speed of the 5X series gravel shaping machine production machine sand making device is 100m/s, performing primary rolling screening on shaped regenerated aggregate particles, screening out the regenerated aggregate with the particle size of 3-25 mm after two times of screening, putting the regenerated aggregate into water, soaking for 48h, and fishing out the regenerated aggregate to dry in the sun;
weighing 1kg of silane coupling agent KH-550 and 99kg of water, stirring and blending to prepare 1 wt% of organic silicon resin emulsion, adding 100kg of organic silicon resin emulsion into 200kg of recycled aggregate, stirring and blending at the rotating speed of 600rpm, stirring for 10min, and then placing into a 160 ℃ oven for baking for 6 h; and after baking, screening to obtain the organic silicon resin modified recycled fine aggregate with the particle size range of 3-5 mm and the organic silicon resin modified recycled coarse aggregate with the particle size range of 5-25 mm.
Preparation examples 2 to 3
The organic silicon resin modified recycled coarse aggregate and the organic silicon resin modified recycled fine aggregate are different from the preparation example 1 in the concentration of the organic silicon resin emulsion, and the specific concentration is shown in the following table 2.
TABLE 2 concentration of Silicone resin emulsion
| Preparation example | Silane coupling agent KH-550/kg | Water/kg | Silicone resin emulsion concentration/wt% |
| Preparation example 1 | 1 | 99 | 1 |
| Preparation example 2 | 4 | 96 | 4 |
| Preparation example 3 | 2 | 98 | 2 |
Examples
Examples 1-7, which are described below as example 1, each provide a recycled concrete resistant to freeze-thaw cycles.
The freeze-thaw cycle resistant recycled concrete provided in example 1 is prepared by the steps of:
weighing 24kg of portland cement, 73kg of the silicone resin modified recycled fine aggregate prepared in preparation example 3, 90kg of the silicone resin modified recycled coarse aggregate prepared in preparation example 3, 13.2kg of water, 3kg of polycarboxylate water reducer LA-8Q, 0.12kg of fatty alcohol-polyoxyethylene ether AEO-7 and 0.5kg of rubber powder RA-789A (the mesh number is 20-60);
putting the portland cement, the organic silicon resin modified recycled fine aggregate, the organic silicon resin modified recycled coarse aggregate, the polycarboxylate water reducer and the rubber powder into a stirrer, stirring and blending for 5min at the rotating speed of 600rpm, adding water and fatty alcohol-polyoxyethylene ether after stirring, stirring and blending for 1min at the rotating speed of 1500rpm, and obtaining the freeze-thaw resistant circulating recycled concrete.
Examples 2-7, which differ from example 1 only in that: the mass of each raw material was different, and specific mass of each raw material is shown in table 3.
TABLE 3 quality of raw materials in freeze-thaw cycle resistant recycled concrete examples 1-7
Examples 8 to 10
The difference between the freeze-thaw resistant recycled concrete and the embodiment 9 is that liquid sodium silicate with the concentration of 3.4 wt% is added into the raw materials, and the liquid sodium silicate is added into a stirrer together with water and fatty alcohol-polyoxyethylene ether; wherein, the adding amount of the liquid sodium silicate in the embodiment 8 is 4 kg; the addition amount of the liquid sodium silicate in example 9 was 5 kg; the amount of the liquid sodium silicate added in example 10 was 6 kg.
Examples 11 to 12
The freeze-thaw resistance cycle recycled concrete is different from the concrete in example 1 in that the sources of the used organic silicon resin modified recycled fine aggregate and organic silicon resin modified recycled coarse aggregate are different;
wherein the silicone resin-modified recycled fine aggregate and the silicone resin-modified recycled coarse aggregate of example 11 were derived from preparation example 1;
the silicone resin-modified recycled fine aggregate and the silicone resin-modified recycled coarse aggregate of example 12 were derived from preparation example 2.
Example 13
The freeze-thaw resistant recycled concrete is different from the concrete in example 1 in that rubber powder with the mass replacement mesh number of 20-60 such as rubber powder with the particle size of 1-3 mm is used.
Example 14
The freeze-thaw resistant recycled concrete is different from the concrete in example 1 in that alkylphenol ethoxylates and the like are used for replacing fatty alcohol-polyoxyethylene ether.
Comparative example
Comparative example 1
A freeze-thaw cycle resistant recycled concrete was distinguished from example 1 in that 5kg of a polycarboxylate water reducing agent or the like was used in place of the rubber powder.
Comparative example 2
The difference between the freeze-thaw resistant recycled concrete and the embodiment 1 is that 0.12kg of polycarboxylate water reducing agent is used for replacing fatty alcohol-polyoxyethylene ether.
Comparative example 3
The freeze-thaw resistant recycled concrete is prepared by the following preparation method:
putting the waste cement building blocks into a crusher to crush the waste cement building blocks to aggregate with the maximum particle size of not more than 31.5mm, putting the aggregate into a 5X series gravel shaping machine production machine sand making device, wherein the linear speed of the 5X series gravel shaping machine production machine sand making device is 100m/s, performing primary rolling screening on shaped regenerated aggregate particles, screening out the regenerated aggregate with the particle size of 3-25 mm after two times of screening, putting the regenerated aggregate into water, soaking for 48h, and fishing out the regenerated aggregate to dry in the sun;
weighing 100kg of liquid sodium silicate with the concentration of 3.4 wt%, adding the liquid sodium silicate into 200kg of recycled aggregate, stirring and blending at the rotating speed of 600rpm for 10min, and then putting the mixture into a 120 ℃ oven to bake for 8 h; after baking is finished, screening out liquid sodium silicate modified recycled fine aggregate with the particle size range of 3-5 mm and liquid sodium silicate modified recycled coarse aggregate with the particle size range of 5-25 mm;
weighing 24kg of portland cement, 73kg of liquid sodium silicate modified recycled fine aggregate, 90kg of liquid sodium silicate modified recycled coarse aggregate, 13.2kg of water, 3kg of polycarboxylate water reducing agent LA-8Q, 0.12kg of fatty alcohol-polyoxyethylene ether AEO-7 and 0.5kg of rubber powder RA-789A (the mesh number is 20-60);
putting the portland cement, the liquid sodium silicate modified recycled fine aggregate, the liquid sodium silicate modified recycled coarse aggregate, the polycarboxylate water reducer and the rubber powder into a stirrer, stirring and blending for 5min at the rotating speed of 600rpm, adding water and fatty alcohol-polyoxyethylene ether after stirring, stirring and blending for 1min at the rotating speed of 1500rpm, and obtaining the freeze-thaw resistant circulating recycled concrete.
Performance test
Preparation of test pieces: the concrete samples of examples 1 to 14 and comparative examples 1 to 3 were poured into concrete test molds of 100mm × 100mm × 100mm, and the concrete in the test molds was cured for 28 days under standard curing conditions after molding to obtain test pieces.
Compressive strength: detecting the compressive strength of the cured test piece according to GB/T50081-2010 standard of test methods for mechanical properties of common concrete;
and (3) freeze-thaw cycle detection:
the test pieces were tested in reagent # 1: taking out the test piece from a maintenance place 4 days before a freeze-thaw experiment, firstly carrying out appearance inspection, then soaking the test piece in water at the temperature of 20 ℃, wherein the liquid level of the test piece is 20mm higher than that of the test piece during soaking, and the test piece is used for the experiment after being soaked for 4 days; controlling each freeze-thaw cycle to be completed within 2-4 h, wherein the time for thawing is not less than 1/4 of the whole freeze-thaw time; when freezing and melting are finished, the central temperature of the test piece is controlled to be minus 17 plus or minus 2 ℃ and 8 plus or minus 2 ℃ respectively; the time taken for each test piece to fall from 6 ℃ to-15 ℃ must not be less than 1/2 for the freeze time.
The test pieces were tested in reagent # 2: taking out the test piece from a maintenance place 4 days before a freeze-thaw experiment, firstly carrying out appearance inspection, then soaking the test piece in a sodium chloride solution with the temperature of 20 ℃ and the concentration of 3.5 wt%, wherein the liquid level is 20mm higher than that of the test piece during soaking, and the test piece is used for the experiment after being soaked for 4 days; controlling each freeze-thaw cycle to be completed within 2-4 h, wherein the time for thawing is not less than 1/4 of the whole freeze-thaw time; when freezing and melting are finished, the central temperature of the test piece is controlled to be minus 17 plus or minus 2 ℃ and 8 plus or minus 2 ℃ respectively; the time taken for each test piece to fall from 6 ℃ to-15 ℃ must not be less than 1/2 for the freeze time.
And respectively recording the number of freeze-thaw cycles of the test piece in which cracks or peeling and other phenomena appear for the first time in the two detection processes.
TABLE 4 test results of 28d compressive Strength of examples 1-14 and comparative examples 1-3
| Test piece | 28d compressive strength/MPa | Test piece | 28d compressive strength/MPa |
| Example 1 | 49.1 | Example 10 | 60.3 |
| Example 2 | 50.8 | Example 11 | 47.2 |
| Example 3 | 52.5 | Example 12 | 48.7 |
| Example 4 | 51.7 | Example 13 | 46.8 |
| Example 5 | 52.9 | Example 14 | 47.5 |
| Example 6 | 57.4 | Comparative example 1 | 49.3 |
| Example 7 | 56.3 | Comparative example 2 | 49.7 |
| Example 8 | 61.2 | Comparative example 3 | 51.4 |
| Example 9 | 62.7 |
TABLE 5 number of freeze-thaw cycles for which cracks or flaking occurred in examples 1 to 14 and comparative examples 1 to 3
Note: the larger the number of freeze-thaw cycles, the better the freeze-thaw resistance.
Combining example 1 and comparative examples 1-2, and combining the data in tables 4-5, it can be seen that, although the 28d compressive strength of comparative example 1 is slightly improved compared with example 1 without adding rubber powder, the number of freeze-thaw cycles in water is reduced from 267 times to 230 times compared with example 1, and the number of freeze-thaw cycles in saline is reduced from 256 times to 145 times compared with example 1, with obvious reduction; compared with the example 1, the number of the freeze-thaw cycles in the water is reduced from 267 times to 227 times, and compared with the example 1, the number of the freeze-thaw cycles in the saline is reduced from 256 times to 139 times, and the reduction is obvious in comparative example 2 without adding the air entraining agent. The use of the simultaneous use of rubber crumb and air entraining agent proved to be able to significantly improve the number of freeze-thaw cycles of recycled concrete, in particular in salt water, possibly due to: the pores of the rubber powder absorb water molecules to block the permeation of the water molecules, and the air bubbles formed by the air entraining agent are closed bubble holes and can also block the permeation of the water molecules, so that the free water is not easy to permeate and migrate in the crystallization process, and the freeze-thaw cycle effect of the anti-salt water is good.
Combining example 1 and comparative example 3, and combining the data in tables 4-5, it can be seen that the compressive strength of 28d of the recycled aggregate modified by using liquid sodium silicate in comparative example 3 is increased from 49.1MPa to 51.4MPa compared with example 1, but the number of freeze-thaw cycles in water is reduced from 267 times to 164 times compared with example 1, and the number of freeze-thaw cycles in brine is reduced from 256 times to 67 times compared with example 1, and the reduction is significant, thus proving that the use of liquid sodium silicate can make up gaps in the recycled aggregate and improve the strength of the recycled concrete, but has little influence on the improvement of the freeze-thaw resistance of the recycled concrete.
As can be seen by combining examples 1-5 and the data in tables 4-5, the compressive strength in the recycled concrete is mainly determined by the water cement ratio in the recycled concrete, the influence of the addition amount of the other raw materials on the compressive strength of the recycled concrete is limited, and the compressive strength and the freeze-thaw resistance of the recycled concrete are better when the water cement ratio of the recycled concrete is 0.45.
It can be seen by combining examples 5-7 and the data in tables 4-5 that the compressive strength of the recycled concrete can be improved when the natural aggregate and the recycled aggregate are blended in the recycled concrete, the compressive strength is higher when the natural aggregate is blended in a larger amount, but the effect of improving the freeze-thaw resistance of the recycled concrete by the recycled aggregate is obvious, and when the silicone resin modified recycled fine aggregate accounts for 35wt% of the total weight of the fine aggregate and the silicone resin modified recycled coarse aggregate accounts for 75wt% of the total weight of the coarse aggregate, the compressive strength of the recycled concrete is slightly reduced, but the freeze-thaw resistance of the recycled concrete is better.
It can be seen from the data in Table 6 in conjunction with examples 7-10 that the use of liquid sodium silicate improves the freeze-thaw resistance of the recycled concrete to some extent, while also enhancing the compressive strength of the recycled concrete.
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 (8)
1. The freeze-thaw resistant recycled concrete is characterized by being prepared from the following raw materials in parts by weight:
240-260 parts of Portland cement
730-750 parts of fine aggregate
900-1100 parts of coarse aggregate
117-132 parts of water
30-40 parts of water reducing agent
1.2-2.3 parts of air entraining agent
50-150 parts of rubber powder;
the fine aggregate comprises organic silicon resin modified recycled fine aggregate and natural fine aggregate, and the organic silicon resin modified recycled fine aggregate accounts for 20-100 wt% of the total weight of the fine aggregate; the coarse aggregate comprises organic silicon resin modified recycled coarse aggregate and natural coarse aggregate, and the organic silicon resin modified recycled coarse aggregate accounts for 20-100 wt% of the total weight of the coarse aggregate;
the air entraining agent is fatty alcohol-polyoxyethylene ether;
the raw material also comprises liquid sodium silicate, and the weight of the liquid sodium silicate is 40-60 parts.
2. The freeze-thaw cycle resistant recycled concrete according to claim 1, wherein: the organic silicon resin modified recycled coarse aggregate and the organic silicon resin modified recycled fine aggregate are prepared by the following preparation steps: the method comprises the steps of crushing, particle shaping, cleaning and drying waste cement blocks recovered from waste buildings to obtain recycled aggregate, soaking the recycled aggregate into organic silicon resin emulsion with the concentration of 1-4 wt%, uniformly stirring, drying, and screening to obtain organic silicon resin modified recycled coarse aggregate and organic silicon resin modified recycled fine aggregate.
3. A freeze-thaw cycle resistant recycled concrete according to claim 2, wherein: the concentration of the silicone resin emulsion was 2 wt%.
4. A freeze-thaw cycle resistant recycled concrete according to claim 3, wherein: the organic silicon resin modified recycled fine aggregate accounts for 35wt% of the total weight of the fine aggregate, and the organic silicon resin modified recycled coarse aggregate accounts for 75wt% of the total weight of the coarse aggregate.
5. The freeze-thaw cycle resistant recycled concrete according to claim 1, wherein: the particle size range of the rubber powder is 20-60 meshes.
6. The freeze-thaw cycle resistant recycled concrete according to claim 1, wherein: the weight ratio of the portland cement to water is 0.45.
7. The freeze-thaw cycle resistant recycled concrete according to claim 6, wherein: the water reducing agent is polycarboxylate water reducing agent.
8. The method for preparing a freeze-thaw cycle resistant recycled concrete according to any one of claims 1 to 7, comprising the steps of: weighing Portland cement, fine aggregate, coarse aggregate, water, a water reducing agent, an air entraining agent, rubber powder and liquid sodium silicate according to the formula ratio, stirring and blending to obtain the freeze-thaw resistant circulating recycled concrete.
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| CN113929390B (en) * | 2021-10-25 | 2022-07-08 | 阆中市上盛建筑材料有限公司 | Environment-friendly green concrete and preparation method thereof |
| CN114149192B (en) * | 2021-12-13 | 2022-11-08 | 中国建筑西南设计研究院有限公司 | Solid antifreezing agent for antifreezing concrete and preparation method thereof |
| CN114380562B (en) * | 2022-02-25 | 2022-11-08 | 青岛光大集团工程有限公司 | Preparation method of anti-freezing recycled concrete and anti-freezing recycled concrete |
| CN114656208B (en) * | 2022-03-18 | 2023-03-17 | 常州大学 | Recycled concrete capable of being recycled in severe cold areas and preparation method thereof |
| CN114956691A (en) * | 2022-06-16 | 2022-08-30 | 贵州工程应用技术学院 | Permeable concrete based on construction waste and preparation method thereof |
| CN116283118A (en) * | 2022-12-01 | 2023-06-23 | 武汉工程大学 | Pavement base material based on organic-inorganic cementing material synergistic stabilization phosphogypsum and recycled aggregate and preparation method thereof |
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Denomination of invention: Freeze-thaw resistant recycled concrete and its preparation method Effective date of registration: 20230608 Granted publication date: 20220517 Pledgee: Zhejiang Yongjia Rural Commercial Bank Co.,Ltd. Shatou Branch Pledgor: Chongde Building Materials Group Co.,Ltd. Registration number: Y2023330001128 |