CN112408895A - Anti-crack recycled concrete and preparation method thereof - Google Patents
Anti-crack recycled concrete and preparation method thereof Download PDFInfo
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- CN112408895A CN112408895A CN202011311566.8A CN202011311566A CN112408895A CN 112408895 A CN112408895 A CN 112408895A CN 202011311566 A CN202011311566 A CN 202011311566A CN 112408895 A CN112408895 A CN 112408895A
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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
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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
- 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
- C04B16/06—Macromolecular compounds fibrous
- C04B16/0616—Macromolecular compounds fibrous from polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
- C04B16/0625—Polyalkenes, e.g. polyethylene
- C04B16/0633—Polypropylene
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- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F1/00—General methods for the manufacture of artificial filaments or the like
- D01F1/02—Addition of substances to the spinning solution or to the melt
- D01F1/10—Other agents for modifying properties
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
- D01F6/44—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from mixtures of polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds as major constituent with other polymers or low-molecular-weight compounds
- D01F6/46—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from mixtures of polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds as major constituent with other polymers or low-molecular-weight compounds of polyolefins
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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
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/34—Non-shrinking or non-cracking materials
- C04B2111/343—Crack resistant materials
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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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Abstract
The application relates to the technical field of concrete, and particularly discloses anti-cracking recycled concrete and a preparation method thereof. The anti-crack recycled concrete comprises the following components in parts by weight: 200 portions of cement and 300 portions of cement; 200 portions of water and 300 portions of water; 200 portions and 300 portions of silica fume; 5-10 parts of a water reducing agent; 50-100 parts of anti-crack composite fiber; 600 portions and 700 portions of recycled coarse aggregate; 500 portions and 600 portions of recycled fine aggregate; 300 portions of sand and 400 portions of sand; 400 portions of fine stone. The preparation method comprises the following steps: mixing and uniformly stirring the recycled fine aggregate, the recycled coarse aggregate, the sand and the fine stone to obtain a mixture C; adding the silica fume and the anti-crack composite fiber into the mixture C, and continuously stirring to obtain a mixture D; and adding water, cement and a water reducing agent into the mixture D, and continuously stirring and mixing. The anti-cracking recycled concrete and the preparation method thereof can be used for paving road beds and have the advantages of being strong in anti-cracking performance and the like.
Description
Technical Field
The application relates to the technical field of concrete, in particular to anti-cracking recycled concrete and a preparation method thereof.
Background
As the construction industry enters a high-speed development stage, the occupation of natural resources and the negative impact on the environment caused by concrete as the largest man-made material also lead to the discussion of sustainable development problems. The amount of waste concrete removed annually in the world, waste concrete from new buildings, and waste concrete discharged from concrete plants, prefabrication plants, etc. is enormous. The treatment method of the waste concrete is mainly to transport the waste concrete to suburbs for stacking or landfill. In order to reduce the land resources occupied by the treatment of the waste concrete, people crush the waste concrete and use the crushed waste concrete as the aggregate of newly produced concrete.
In the related technology, the collected waste concrete is firstly crushed into recycled aggregates with different particle sizes, then the recycled aggregates are used for replacing a small amount of or completely replacing natural aggregates, and cement, water, an additive and other raw materials are supplemented to prepare the recycled concrete.
In view of the above-mentioned related arts, the inventors believe that the recycled concrete is likely to crack in actual use, and the crack resistance of the recycled concrete needs to be improved.
Disclosure of Invention
In order to improve the crack resistance of the recycled concrete, the application provides the crack-resistant recycled concrete and the preparation method thereof.
In a first aspect, the present application provides an anti-crack recycled concrete, which adopts the following technical scheme.
The anti-crack recycled concrete comprises the following components in parts by weight:
200 portions of cement and 300 portions of cement;
200 portions of water and 300 portions of water;
200 portions and 300 portions of silica fume;
5-10 parts of a water reducing agent;
50-100 parts of anti-crack composite fiber;
600 portions and 700 portions of recycled coarse aggregate;
500 portions and 600 portions of recycled fine aggregate;
300 portions of sand and 400 portions of sand;
400 portions of fine stone.
By adopting the technical scheme, cement is used as a main binder to bond fine stones, sand, recycled fine aggregate and recycled coarse aggregate together to form a basic framework of recycled concrete. The crack-resistant composite fiber is added, so that the defects of large shrinkage deformation and poor impermeability of cement mortar are mainly overcome, and the crack-resistant composite fiber is directly doped into concrete, so that the crack resistance of the concrete can be obviously improved. The silica fume is used as a main filler, has small average particle size and good filling effect, can be filled in gaps among cement particles, improves the strength and durability of concrete, improves the wear-resisting property of the concrete, generates gel with hydration products, and has the functions of water retention and segregation prevention.
Preferably, the anti-crack composite fiber comprises the following components in parts by weight:
1-5 parts of graphene;
100 portions and 200 portions of polypropylene resin;
20-30 parts of waste glass;
1-5 parts of maleic acid glycoside grafted polypropylene;
2-4 parts of a silane coupling agent;
3-5 parts of liquid paraffin.
By adopting the technical scheme, the polypropylene resin is used as the main base material, the waste glass is added, the strength and toughness of the anti-cracking composite fiber are improved while the environment is protected and the cost is reduced, and the anti-cracking performance of the concrete can be obviously improved by doping the anti-cracking composite fiber into the concrete. The maleic acid glycoside grafted polypropylene is used as a compatilizer, so that the compatibility among resins can be improved, the dispersibility of each component can be improved, and the macroscopic properties of the material, such as mechanics and the like, can be indirectly improved. The silane coupling agent can be used for carrying out surface modification on polypropylene, and the dispersibility of graphene on the surface of the polypropylene is improved. The liquid paraffin is used as a lubricant, and the addition of the liquid paraffin can reduce the internal pressure of a screw during material processing, so that the material can be extruded more quickly.
Preferably, the preparation of the anti-crack composite fiber comprises the following steps:
a, ball-milling graphene, polypropylene resin and waste glass to obtain a mixture A;
b, mixing the maleic acid glycoside grafted polypropylene, the silane coupling agent and the liquid paraffin with the mixture A to obtain a mixture B;
and c, melting and extruding the mixture B, and then carrying out spinning to obtain the anti-crack composite fiber.
By adopting the technical scheme, the graphene, the polypropylene resin and the waste glass are subjected to ball milling, and the obtained mixture A is small in particle size and convenient to mix in the next step. The raw materials are mixed in multiple steps, so that the raw materials are mixed more fully, the toughness of the prepared anti-cracking composite fiber is improved, and the anti-cracking performance of the concrete is improved by doping the anti-cracking composite fiber into the concrete.
Preferably, in the step a, the ball milling rotating speed is set to 250-350rpm, and the ball milling time is set to 2-3 h; in the step c, a twin-screw extruder is used for melt extrusion, the screw rotating speed of the twin-screw extruder is set to be 200-300rpm, and the temperature is set to be 160-200 ℃.
By adopting the technical scheme, the ball milling rotating speed and the ball milling time within the range are adopted, the obtained composite material is good in dispersion uniformity, the screw rotating speed and the screw temperature within the range are adopted, the obtained anti-cracking composite fiber is good in tensile property, and the anti-cracking performance of concrete can be remarkably improved by doping the anti-cracking composite fiber into the concrete.
Preferably, the preparation of the recycled fine aggregate and the recycled coarse aggregate comprises the following steps:
a1, hammering the waste concrete, removing steel bars and various impurities, and screening the waste concrete into recycled concrete particles with the particle sizes of less than 5mm, 5-20mm and 20-50 mm;
a2, continuously hammering the recycled concrete particles with the particle size of 20-50mm, and screening the recycled concrete particles with the particle size of less than 5mm and 5-20 mm;
and the screened recycled concrete particles with the particle size of less than 5mm are recycled fine aggregate, and the recycled concrete particles with the particle size of 5-20mm are recycled coarse aggregate.
By adopting the technical scheme, the recycled aggregate is used for replacing part of natural aggregate, the waste concrete is recycled, the land occupied by the waste concrete treatment is reduced, and the cost is saved. Natural disasters such as landslide and debris flow can be caused by over mining of the natural aggregate, and the use of the natural aggregate is reduced in the production process of the concrete, so that the environment is protected.
Preferably, the recycled fine aggregate and the recycled coarse aggregate obtained in A1 and A2 are further subjected to strengthening treatment, and the strengthening treatment comprises the following steps:
b1, placing the obtained regenerated fine aggregate and regenerated coarse aggregate into a clean water tank, ultrasonically cleaning for 20-30min, continuously stirring, standing for 20-30min after cleaning is finished, removing suspended matters suspended above the clean water tank, and fishing out and drying the concrete block;
and B2, soaking the concrete block treated by the B1 in an acid tank for 20-30min, taking out, soaking in an alkaline tank for 15-20min, taking out, washing in a washing tank, and taking out and drying the concrete block after washing.
By adopting the technical scheme, loose cement paste attached to the surface of the recycled aggregate and impurity garbage mixed in the recycled aggregate are removed by ultrasonic cleaning. And (3) carrying out acid treatment on the recycled aggregate to remove cement paste tightly combined with the recycled aggregate and improve the quality of the recycled aggregate. The recycled aggregate treated by the acid liquor is placed in an alkaline pool for neutralization, so that the pH value of the recycled aggregate is prevented from being acidic, and the corrosion resistance and the crack resistance of the prepared concrete are improved.
Preferably, the liquid in the acid tank is a hydrochloric acid solution with the concentration of 2-3mol/L, and the liquid in the alkaline tank is a sodium carbonate solution with the concentration of 1-2 mol/L.
By adopting the technical scheme, the hydrochloric acid can remove cement paste tightly combined with the recycled aggregate, such as calcium oxide, silicon dioxide, aluminum oxide, iron oxide and the like. The sodium carbonate solution can neutralize hydrochloric acid attached to the surface of the recycled aggregate, and prevent the pH value of the recycled aggregate from being acidic, so that the corrosion resistance and the crack resistance of the prepared concrete are improved.
Preferably, the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent.
By adopting the technical scheme, the water reducing agent is doped, so that the using amount of water can be effectively reduced under the condition of not changing the mixture ratio of raw materials and the slump of concrete, the anti-cracking performance of the concrete is improved, and meanwhile, the service life of the concrete can be prolonged by adding the water reducing agent.
In a second aspect, the present application provides a method for preparing anti-crack recycled concrete, which adopts the following technical scheme.
A preparation method of anti-crack recycled concrete comprises the following steps:
s1, mixing and uniformly stirring the recycled fine aggregate, the recycled coarse aggregate, the sand and the fine stones to obtain a mixture C;
s2, adding the silica fume and the anti-crack composite fibers into the mixture C, and continuously stirring to obtain a mixture D;
s3, adding water, cement and a water reducing agent into the mixture D, and continuously stirring and mixing.
By adopting the technical scheme, the raw materials are mixed step by step, so that the dispersibility of the raw materials in the concrete mixture is better, the workability of the concrete mixture is improved, and the prepared concrete has good compression resistance and crack resistance.
Preferably, in the step S3, the stirring temperature is set to be 50-60 ℃, and the stirring time is set to be 2-3 h.
By adopting the technical scheme, the raw materials are stirred within a better temperature and time range, so that the dispersibility of the raw materials in the concrete mixture is better, the workability of the concrete mixture is improved, and the prepared concrete has better compression resistance and crack resistance.
In summary, the present application has the following beneficial effects:
1. the crack-resistant composite fiber is added, so that the defects of large shrinkage deformation and poor impermeability of cement mortar are mainly overcome, and the crack-resistant composite fiber is directly added into concrete, so that the crack resistance of the concrete can be obviously improved;
2. according to the anti-cracking composite fiber prepared in the application, the polypropylene resin is used as a main base material, the toughness of the anti-cracking composite fiber can be improved by adding the waste glass, the anti-cracking performance of the prepared concrete is improved, meanwhile, the waste glass is used as a raw material, the production cost is reduced, and sustainable development is facilitated;
3. according to the method, the recycled fine aggregate and the recycled coarse aggregate are subjected to strengthening treatment, impurity garbage attached to the surface of the recycled aggregate is removed, the strength of the recycled aggregate is improved, and the prepared concrete is good in compression resistance and crack resistance.
Detailed Description
The present application will be described in further detail with reference to examples.
The cement in the embodiment of the application is common Portland cement, and the strength grade is 42.5;
the sands are all natural medium sands in the area II, the fineness modulus is 2.5, and the mud content is less than 1.0%;
the fine stones are crushed stones with the grain size of 5-20mm in continuous gradation;
the silica fume is collected from a mineral processing factory in Lingshou county;
the silane coupling agent is prepared from Jinan Rong Guang chemical Co., Ltd and is KH 550;
the graphene and the polypropylene resin are both obtained from Huayun plastics raw materials Co., Ltd, Dongguan city;
maleic acid glycoside grafted polypropylene and liquid paraffin are both taken from the Yingtai plastic material meridian of lignum Cinnamomi Camphorae of Dongguan city;
the polycarboxylic acid high-efficiency water reducing agents are all collected from Shandong HanLin Jun International trade limited.
Preparation examples of raw materials
Preparation example 1: an anti-crack composite fiber, each component and the corresponding weight thereof are shown in Table 1, and is prepared by the following steps,
a, putting graphene, polypropylene resin and waste glass into a ball mill, and carrying out ball milling for 2h at 250rpm to obtain a mixture A;
b, mixing the maleic acid glycoside grafted polypropylene, the silane coupling agent and the liquid paraffin with the mixture A to obtain a mixture B;
and c, melting and extruding the mixture B by using a double-screw extruder, and performing spinning to obtain the anti-crack composite fiber, wherein the rotating speed of a screw of the double-screw extruder is set to be 200rpm, and the temperatures of 5 sections from a feeding port to a machine head are set to be 160 ℃, 175 ℃, 180 ℃, 180 ℃ and 180 ℃ in sequence.
Preparation examples 2 to 3: an anti-crack composite fiber was different from that of preparation example 1 in that each component and the corresponding weight thereof are shown in table 1.
TABLE 1 Components and weights (kg) thereof in preparation examples 1-3
Preparation example 4: an anti-crack composite fiber is different from the preparation example 1 in that when the anti-crack composite fiber is prepared, in a, the ball milling rotating speed is set to be 300rpm, and the ball milling time is set to be 2.5 h; in the step c, the screw rotation speed of the twin-screw extruder was set to 250rpm, and the temperatures of 5 stages from the feed port to the head were set to 170 ℃, 185 ℃, 185 ℃, 190 ℃ and 190 ℃ in this order.
Preparation example 5: an anti-crack composite fiber is different from the preparation example 1 in that when the anti-crack composite fiber is prepared, in a, the ball milling rotating speed is set to be 350rpm, and the ball milling time is set to be 3 hours; in the step c, the screw rotation speed of the twin-screw extruder was set to 300rpm, and the temperatures of 5 stages from the feed port to the head were set to 175 ℃, 190 ℃, 200 ℃, 200 ℃ and 200 ℃ in this order.
Examples
Example 1: an anti-crack recycled concrete, the components and the corresponding weight thereof are shown in Table 2, and is prepared by the following steps,
s1, mixing and uniformly stirring the recycled fine aggregate, the recycled coarse aggregate, the sand and the fine stones to obtain a mixture C;
s2, adding the silica fume and the anti-crack composite fiber prepared in the preparation example 1 into the mixture C, and continuously stirring to obtain a mixture D;
s3, adding water, cement and a water reducing agent into the mixture D, and continuously stirring and mixing for 2 hours at 50 ℃, wherein the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent.
Wherein the recycled fine aggregate and the recycled coarse aggregate are obtained by the following steps,
a1, crushing the waste concrete by using a jaw crusher, removing steel bars and various impurities, and screening the recycled concrete preform into recycled concrete particles with the particle sizes of less than 5mm, 5-20mm and 20-50mm by using a concrete vibration screening machine;
a2, continuously hammering the recycled concrete particles with the particle size of 20-50mm by using a hammering type crusher, and screening the recycled concrete preform into the recycled concrete particles with the particle size of less than 5mm and 5-20mm by using a concrete vibration screening machine.
And the screened recycled concrete particles with the particle size of less than 5mm are recycled fine aggregate, and the recycled concrete particles with the particle size of 5-20mm are recycled coarse aggregate.
Examples 2 to 6: an anti-cracking recycled concrete, which is different from example 1 in that each component and the corresponding weight thereof are shown in table 2.
TABLE 2 Components and weights (kg) thereof in examples 1-6
Example 7: an anti-crack recycled concrete, which is different from the concrete of example 1 in that the anti-crack composite fiber prepared in preparation example 2 is used in the preparation process of the anti-crack recycled concrete.
Example 8: an anti-crack recycled concrete, which is different from that of example 1 in that the anti-crack composite fiber prepared in preparation example 3 was used in the preparation process of the anti-crack recycled concrete.
Example 9: an anti-crack recycled concrete, which is different from that of example 1 in that the anti-crack composite fiber prepared in preparation example 4 was used in the preparation process of the anti-crack recycled concrete.
Example 10: an anti-crack recycled concrete, which is different from that of example 1 in that the anti-crack composite fiber prepared in preparation example 5 was used in the preparation process of the anti-crack recycled concrete.
Example 11: an anti-crack recycled concrete, which is different from the concrete of example 1 in that the stirring temperature is set to 55 ℃ and the stirring time is set to 2.5h in S3 in the preparation process of the anti-crack recycled concrete.
Example 12: an anti-crack recycled concrete, which is different from that of example 1 in that the stirring temperature is set to 60 ℃ and the stirring time is set to 3 hours in S3 during the preparation of the anti-crack recycled concrete.
Example 13: a crack-resistant recycled concrete is different from the concrete in the embodiment 1 in that in the preparation process of the recycled fine aggregate and the recycled coarse aggregate, the recycled fine aggregate and the recycled coarse aggregate are also subjected to strengthening treatment, wherein the strengthening treatment process is as follows, B1, the obtained recycled fine aggregate and the obtained recycled coarse aggregate are placed in a clean water tank, ultrasonically cleaned for 20min and continuously stirred, after the cleaning is finished, the mixture is kept still for 20min, suspended matters suspended above the clean water tank are removed, and concrete blocks are fished out and aired for 1 h;
and B2, placing the concrete block treated by the B1 into an acid tank, soaking for 20min, taking out, placing into an alkaline tank, soaking for 15min, taking out, placing into a cleaning tank, washing, and fishing out the concrete block and airing for 1h after the washing is finished, wherein the liquid in the acid tank is a hydrochloric acid solution with the concentration of 2mol/L, and the liquid in the alkaline tank is a sodium carbonate solution with the concentration of 1 mol/L.
Example 14: an anti-cracking recycled concrete, which is different from the concrete in the embodiment 13, is characterized in that in the B1 strengthening treatment process of recycled fine aggregate and recycled coarse aggregate, ultrasonic cleaning is carried out for 25min, and after the cleaning is finished, standing is carried out for 25 min; b2, soaking in an acid pool for 25min and soaking in an alkaline pool for 17 min.
Example 15: an anti-crack recycled concrete, which is different from the concrete in the embodiment 13, is characterized in that in the B1 strengthening treatment process of recycled fine aggregate and recycled coarse aggregate, ultrasonic cleaning is carried out for 30min, and after the cleaning is finished, standing is carried out for 30 min; b2, soaking in an acidic pool for 30min and in an alkaline pool for 20 min.
Example 16: a difference from example 13 is that in B2 in the reinforcing treatment process of recycled fine aggregate and recycled coarse aggregate, the liquid in the acid tank is a hydrochloric acid solution with a concentration of 2.5mol/L, and the liquid in the alkaline tank is a sodium carbonate solution with a concentration of 1.5 mol/L.
Example 17: a difference from example 13 is that in B2 in the reinforcing treatment process of recycled fine aggregate and recycled coarse aggregate, the liquid in the acid tank is a hydrochloric acid solution with a concentration of 3mol/L, and the liquid in the alkaline tank is a sodium carbonate solution with a concentration of 2 mol/L.
Comparative example
Comparative example 1: a concrete, which is different from example 1 in that no recycled coarse aggregate and recycled fine aggregate are added in the preparation process of the concrete, the addition amount of sand is 800kg, and the addition amount of fine stone is 1000 kg.
Comparative example 2: a concrete, which is different from example 1 in that no anti-crack composite fiber is added in the preparation process of the concrete.
Comparative example 3: the concrete is different from the concrete in example 1 in that graphene is not added in the preparation process of the anti-crack composite fiber.
Comparative example 4: a concrete is different from the concrete in example 1 in that no waste glass is added in the preparation process of the anti-crack composite fiber.
Comparative example 5: the concrete is different from the concrete in the embodiment 1 in that in the preparation process a of the anti-crack composite fiber, the ball milling rotating speed is set to be 200rpm, and the ball milling time is set to be 1 h; in the step c, the screw rotation speed of the twin-screw extruder was set to 150rpm, and the temperatures of 5 stages from the feed port to the head were set to 140 ℃, 155 ℃, 155 ℃, 160 ℃ and 160 ℃ in this order.
Comparative example 6: the concrete is different from the concrete in the embodiment 1 in that in the preparation process a of the anti-crack composite fiber, the ball milling rotating speed is set to be 400rpm, and the ball milling time is set to be 4 hours; in the step c, the screw rotation speed of the twin-screw extruder was set to 400rpm, and the temperatures of 5 stages from the feed port to the head were set to 180 ℃, 195 ℃, 210 ℃, 210 ℃ in this order.
Comparative example 7: a concrete, which is different from example 13 in that in the reinforcing treatment process of recycled fine aggregate and recycled coarse aggregate in B1, ultrasonic cleaning is carried out for 10min, and after the cleaning is finished, standing is carried out for 10 min; b2, soaking in an acid pool for 10min and in an alkaline pool for 5 min.
Comparative example 8: a concrete, which is different from the concrete of example 13 in that in the B1 in the strengthening treatment process of the recycled fine aggregate and the recycled coarse aggregate, ultrasonic cleaning is carried out for 40min, and after the cleaning is finished, standing is carried out for 40 min; b2, soaking in an acid pool for 40min and in an alkaline pool for 30 min.
Comparative example 9: a concrete, which is different from example 13 in that in B2 in the reinforcing treatment process of recycled fine aggregate and recycled coarse aggregate, the liquid in the acid tank was a hydrochloric acid solution having a concentration of 1mol/L, and the liquid in the alkaline tank was a sodium carbonate solution having a concentration of 0.5 mol/L.
Comparative example 10: a concrete, which is different from example 13 in that in B2 in the reinforcing treatment process of recycled fine aggregate and recycled coarse aggregate, the liquid in the acid tank was a hydrochloric acid solution having a concentration of 5mol/L, and the liquid in the alkaline tank was a sodium carbonate solution having a concentration of 3 mol/L.
Comparative example 11: a concrete, which was different from example 1 in that the stirring temperature was set to 40 ℃ and the stirring time was set to 1 hour in S3 during the preparation of the concrete.
Comparative example 12: a concrete, which was different from example 1 in that the stirring temperature was set to 70 ℃ and the stirring time was set to 4 hours in S3 during the preparation of the concrete.
Performance test
The concrete prepared in the examples 1 to 17 and the concrete prepared in the comparative examples 1 to 12 are taken as test objects, cubic standard test pieces with the specification of 150 multiplied by 150mm are prepared, the test is carried out according to GB/T50081-2019 standard of test method for mechanical property of common concrete, and the concrete prepared in each example or comparative example is tested by taking three test pieces. The compressive strength and the splitting tensile strength of the samples were tested, whether cracks were generated in each group of samples was observed, the length of the cracks was recorded, and the test results were included in the following table 3.
As can be seen from the test data in table 3:
the test pieces of the anti-crack recycled concrete prepared in the examples 1 to 17 have no crack after being cured for 28 days, the compressive strength is higher than 44.4MPa, and the splitting tensile degree is higher than 3.79MPa, wherein the example 14 is the optimal example.
By combining example 1 and comparative example 1, and by combining table 3, it can be seen that the crack resistance of the prepared crack-resistant recycled concrete is not significantly reduced by using recycled fine aggregate and recycled coarse aggregate instead of a part of natural aggregate, compared with the concrete completely made of natural aggregate, which indicates that the use of recycled aggregate instead of a part of natural aggregate can reduce the production cost and is beneficial to sustainable development without affecting the crack resistance of the concrete.
It can be seen from the combination of example 1 and comparative example 2 and table 3 that the addition of the anti-crack composite fiber can significantly improve the compression resistance and anti-crack performance of the prepared concrete when the concrete is prepared.
By combining the example 1 and the comparative examples 3 and 4, and combining the table 3, it can be seen that when the anti-crack composite fiber is prepared, the graphene and the waste glass are added, so that the strength and the toughness of the anti-crack composite fiber can be improved, and when the anti-crack composite fiber is doped into concrete, the anti-crack performance of the concrete is obviously improved.
By combining the example 1 and the comparative examples 5 and 6 and combining the table 3, it can be seen that in the preparation process a of the anti-crack composite fiber, the preferred setting range of the ball milling rotation speed is 250-350rpm, and the preferred setting range of the ball milling time is 2-3 h; in c, the preferred setting range of the screw rotation speed of the twin-screw extruder is 200-300rpm, and the preferred setting range of the temperature is 160-200 ℃. The anti-cracking composite fiber prepared in the rotating speed and temperature range has better toughness, and can obviously improve the anti-cracking performance of concrete when being added into the concrete.
By combining examples 1, 13, 14 and 15 and comparative examples 7 and 8 and combining table 3, it can be seen that the compressive and crack resistance of the prepared crack-resistant recycled concrete can be remarkably improved by performing strengthening treatment on the recycled fine aggregate and the recycled coarse aggregate, and in the strengthening treatment process, the preferred time range of ultrasonic cleaning is 20-30min, the preferred time range of standing after cleaning is 20-30min, the preferred time range of soaking in an acid tank is 20-30min, and the preferred time range of soaking in an alkaline tank is 15-20 min. Within this time range, the strengthening treatment effect is the best.
As can be seen from the combination of examples 13, 16 and 17 and comparative examples 9 and 10 and Table 3, the preferable concentration of the hydrochloric acid solution in the acid tank is 2 to 3mol/L and the preferable concentration of the sodium carbonate solution in the alkaline tank is 1 to 2mol/L in the strengthening treatment. Within this concentration range, the effect of the strengthening treatment is the best.
As can be seen from the combination of example 1 and comparative examples 11 and 12, and from Table 3, in the preparation of the anti-crack recycled concrete, the preferable range of the stirring temperature is 50 to 60 ℃ and the preferable range of the stirring time is 2 to 3 hours in S3.
Table 3 results of performance testing
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 (10)
1. The anti-crack recycled concrete is characterized by comprising the following components in parts by weight:
200 portions of cement and 300 portions of cement;
200 portions of water and 300 portions of water;
200 portions and 300 portions of silica fume;
5-10 parts of a water reducing agent;
50-100 parts of anti-crack composite fiber;
600 portions and 700 portions of recycled coarse aggregate;
500 portions and 600 portions of recycled fine aggregate;
300 portions of sand and 400 portions of sand;
400 portions of fine stone.
2. The anti-crack recycled concrete according to claim 1, wherein the anti-crack composite fiber comprises the following components in parts by weight:
1-5 parts of graphene;
100 portions and 200 portions of polypropylene resin;
20-30 parts of waste glass;
1-5 parts of maleic acid glycoside grafted polypropylene;
2-4 parts of a silane coupling agent;
3-5 parts of liquid paraffin.
3. The crack-resistant recycled concrete of claim 2, wherein the preparation of said crack-resistant composite fibers comprises the steps of:
a, ball-milling graphene, polypropylene resin and waste glass to obtain a mixture A;
b, mixing the maleic acid glycoside grafted polypropylene, the silane coupling agent and the liquid paraffin with the mixture A to obtain a mixture B;
and c, melting and extruding the mixture B, and then carrying out spinning to obtain the anti-crack composite fiber.
4. The anti-crack recycled concrete according to claim 3, wherein in the step a, the ball milling rotation speed is set to 250-350rpm, and the ball milling time is set to 2-3 h; in the step c, a twin-screw extruder is used for melt extrusion, the screw rotating speed of the twin-screw extruder is set to be 200-300rpm, and the temperature is set to be 160-200 ℃.
5. The crack-resistant recycled concrete according to claim 1, wherein the preparation of the recycled fine aggregate and the recycled coarse aggregate comprises the steps of:
a1, hammering the waste concrete, removing steel bars and various impurities, and screening the waste concrete into recycled concrete particles with the particle sizes of less than 5mm, 5-20mm and 20-50 mm;
a2, continuously hammering the recycled concrete particles with the particle size of 20-50mm, and screening the recycled concrete particles with the particle size of less than 5mm and 5-20 mm;
and the screened recycled concrete particles with the particle size of less than 5mm are recycled fine aggregate, and the recycled concrete particles with the particle size of 5-20mm are recycled coarse aggregate.
6. The crack-resistant recycled concrete according to claim 5, wherein the recycled fine aggregate and the recycled coarse aggregate obtained in A1 and A2 are further subjected to a strengthening treatment, and the strengthening treatment comprises the following steps:
b1, placing the obtained regenerated fine aggregate and regenerated coarse aggregate into a clean water tank, ultrasonically cleaning for 20-30min, continuously stirring, standing for 20-30min after cleaning is finished, removing suspended matters suspended above the clean water tank, and fishing out and drying the concrete block;
and B2, soaking the concrete block treated by the B1 in an acid tank for 20-30min, taking out, soaking in an alkaline tank for 15-20min, taking out, washing in a washing tank, and taking out and drying the concrete block after washing.
7. The crack-resistant recycled concrete according to claim 6, wherein the liquid in the acid tank is a hydrochloric acid solution with a concentration of 2-3mol/L, and the liquid in the alkaline tank is a sodium carbonate solution with a concentration of 1-2 mol/L.
8. The anti-crack recycled concrete of claim 1, characterized in that the water reducer is a polycarboxylic acid high-efficiency water reducer.
9. The method for preparing the anti-crack recycled concrete according to any one of claims 1 to 8, which is characterized by comprising the following steps:
s1, mixing and uniformly stirring the recycled fine aggregate, the recycled coarse aggregate, the sand and the fine stones to obtain a mixture C;
s2, adding the silica fume and the anti-crack composite fibers into the mixture C, and continuously stirring to obtain a mixture D;
s3, adding water, cement and a water reducing agent into the mixture D, and continuously stirring and mixing.
10. The method for preparing anti-crack recycled concrete according to claim 8, wherein in the step S3, the stirring temperature is set to 50-60 ℃ and the stirring time is set to 2-3 h.
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