CN113979688A - Recycled concrete capable of being repeatedly utilized in cold regions and preparation method - Google Patents
Recycled concrete capable of being repeatedly utilized in cold regions and preparation method Download PDFInfo
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- CN113979688A CN113979688A CN202111128218.1A CN202111128218A CN113979688A CN 113979688 A CN113979688 A CN 113979688A CN 202111128218 A CN202111128218 A CN 202111128218A CN 113979688 A CN113979688 A CN 113979688A
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- 239000004567 concrete Substances 0.000 title claims abstract description 112
- 238000002360 preparation method Methods 0.000 title claims abstract description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 74
- 239000003638 chemical reducing agent Substances 0.000 claims abstract description 36
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 33
- 239000011398 Portland cement Substances 0.000 claims abstract description 32
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 30
- 239000004576 sand Substances 0.000 claims abstract description 30
- 239000010881 fly ash Substances 0.000 claims abstract description 27
- 229910021487 silica fume Inorganic materials 0.000 claims abstract description 27
- 239000002893 slag Substances 0.000 claims abstract description 27
- 238000003756 stirring Methods 0.000 claims description 44
- 239000002245 particle Substances 0.000 claims description 18
- 239000002253 acid Substances 0.000 claims description 17
- 238000002156 mixing Methods 0.000 claims description 10
- 150000002191 fatty alcohols Chemical class 0.000 claims description 6
- RSWGJHLUYNHPMX-UHFFFAOYSA-N Abietic-Saeure Natural products C12CCC(C(C)C)=CC2=CCC2C1(C)CCCC2(C)C(O)=O RSWGJHLUYNHPMX-UHFFFAOYSA-N 0.000 claims description 3
- KHPCPRHQVVSZAH-HUOMCSJISA-N Rosin Natural products O(C/C=C/c1ccccc1)[C@H]1[C@H](O)[C@@H](O)[C@@H](O)[C@@H](CO)O1 KHPCPRHQVVSZAH-HUOMCSJISA-N 0.000 claims description 3
- PSDYQSWHANEKRV-UHFFFAOYSA-N [S]N Chemical class [S]N PSDYQSWHANEKRV-UHFFFAOYSA-N 0.000 claims description 3
- 239000001397 quillaja saponaria molina bark Substances 0.000 claims description 3
- 229930182490 saponin Natural products 0.000 claims description 3
- 150000007949 saponins Chemical class 0.000 claims description 3
- KHPCPRHQVVSZAH-UHFFFAOYSA-N trans-cinnamyl beta-D-glucopyranoside Natural products OC1C(O)C(O)C(CO)OC1OCC=CC1=CC=CC=C1 KHPCPRHQVVSZAH-UHFFFAOYSA-N 0.000 claims description 3
- 230000009467 reduction Effects 0.000 claims description 2
- 150000002790 naphthalenes Chemical class 0.000 claims 1
- 239000002699 waste material Substances 0.000 abstract description 17
- 238000007710 freezing Methods 0.000 abstract description 13
- 230000000704 physical effect Effects 0.000 abstract description 5
- 239000004566 building material Substances 0.000 abstract description 2
- 238000003912 environmental pollution Methods 0.000 abstract 1
- 230000008014 freezing Effects 0.000 description 12
- 238000010257 thawing Methods 0.000 description 11
- 239000004148 curcumin Substances 0.000 description 9
- 239000000463 material Substances 0.000 description 9
- 238000000034 method Methods 0.000 description 7
- 238000010521 absorption reaction Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 239000000843 powder Substances 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 3
- 239000003292 glue Substances 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000004568 cement Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000036571 hydration Effects 0.000 description 2
- 238000006703 hydration reaction Methods 0.000 description 2
- 229910052500 inorganic mineral Inorganic materials 0.000 description 2
- 239000011707 mineral Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000004570 mortar (masonry) Substances 0.000 description 2
- DGVVJWXRCWCCOD-UHFFFAOYSA-N naphthalene;hydrate Chemical compound O.C1=CC=CC2=CC=CC=C21 DGVVJWXRCWCCOD-UHFFFAOYSA-N 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- 238000005303 weighing Methods 0.000 description 2
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- 239000013058 crude material Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000000877 morphologic effect Effects 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- 229940051841 polyoxyethylene ether Drugs 0.000 description 1
- 229920000056 polyoxyethylene ether Polymers 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
Classifications
-
- 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
-
- 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
-
- 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
- C04B2111/20—Resistance against chemical, physical or biological attack
- C04B2111/29—Frost-thaw resistance
-
- 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
- C04B2111/76—Use at unusual temperatures, e.g. sub-zero
-
- 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
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Civil Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- Environmental & Geological Engineering (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
Abstract
本发明属于建筑材料技术领域，具体涉及一种可在寒冷地区多次利用的再生混凝土及制备方法，该再生混凝土包括以下重量份的组分：再生粗骨料860~912份，河砂692~736份，硅酸盐水泥286~312份，硅灰22~24份，粉煤灰88~96份，矿渣44~48份，减水剂2.2~2.4份，引气剂0.26~0.29份和水169~182份。本发明提供的可在寒冷地区多次利用的再生混凝土具有强度高、抗冻性能好的优点，破碎冻融300次后的废弃再生混凝土得到的第二代再生粗骨料满足第Ⅲ类再生粗骨料物理性能要求，可以再次应用于结构混凝土，使用其制备的第二代再生混凝土同样具备优良的力学与抗冻性能，使得再生混凝土能够多次利用，同时解决了寒冷地区废弃再生混凝土污染环境的问题。The invention belongs to the technical field of building materials, and in particular relates to a recycled concrete that can be used multiple times in cold regions and a preparation method. The recycled concrete comprises the following components by weight: 860-912 parts of recycled coarse aggregate, 692-692 parts of river sand 736 parts, Portland cement 286~312 parts, silica fume 22~24 parts, fly ash 88~96 parts, slag 44~48 parts, water reducing agent 2.2~2.4 parts, air entraining agent 0.26~0.29 parts and water 169~182 copies. The recycled concrete provided by the invention, which can be used for many times in cold regions, has the advantages of high strength and good frost resistance. The physical properties of aggregates are required, and they can be applied to structural concrete again. The second-generation recycled concrete prepared by using it also has excellent mechanical and anti-freezing properties, which enables the recycled concrete to be reused many times, and solves the problem of environmental pollution by waste recycled concrete in cold areas. The problem.
Description
Technical Field
The invention belongs to the technical field of building materials, and particularly relates to recycled concrete capable of being repeatedly used in cold regions and a preparation method thereof.
Background
With the continuous improvement of national requirements on sustainable development of the building industry, the popularization of recycled concrete becomes inevitable. In cold regions, a large number of recycled concrete structures are exposed to a freezing and thawing environment, and after the recycled concrete structures are dismantled into waste recycled concrete due to natural disasters or the designed service life, the waste recycled concrete structures are possibly scrapped due to the failure of frost resistance durability, cannot be recycled and become useless waste. The waste recycled concrete not only needs to spend a large amount of manpower and material resources for disposal, but also occupies a large amount of land resources and pollutes the environment.
However, the mechanical property and the freezing resistance of the recycled concrete under the full-substitution condition are generally poor, the safety reserve is small, and the loss of freezing resistance durability is usually accompanied with the serious damage of an internal structure, which can cause the physical property reduction of the second-generation recycled coarse aggregate, so that the waste recycled concrete in cold regions is not recommended to be used as the coarse aggregate to be applied to the structural concrete again.
In the prior art, the problem that the concrete in cold regions cannot be repeatedly utilized is not solved by recycled concrete which has good chemical performance and strong frost resistance and can be repeatedly utilized.
Disclosure of Invention
In order to solve the defects of the prior art, the invention aims to provide recycled concrete capable of being repeatedly used in a cold area, the recycled concrete has high strength and good frost resistance, second-generation recycled coarse aggregate obtained by crushing the recycled concrete after being frozen and thawed for 300 times can be applied to structural concrete again, and the problem that the waste recycled concrete in the cold area cannot be repeatedly used is solved.
The invention also aims to provide a preparation method of recycled concrete capable of being repeatedly used in cold regions, which is beneficial to the industrial production of concrete and products thereof.
In order to solve the defects of the prior art, the technical scheme provided by the invention is as follows:
the recycled concrete capable of being repeatedly used in cold regions comprises the following components in parts by weight: 860-912 parts of recycled coarse aggregate, 692-736 parts of river sand, 286-312 parts of portland cement, 22-24 parts of silica fume, 88-96 parts of fly ash, 44-48 parts of slag, 2.2-2.4 parts of a water reducing agent, 0.26-0.29 part of an air entraining agent and 169-182 parts of water.
Preferably, the recycled coarse aggregate is I-type recycled coarse aggregate or II-type recycled coarse aggregate specified in GB/T25177-2010, and the particle size is 5-25 mm.
Preferably, the strength grade of the portland cement is not less than 42.5.
Preferably, the weight ratio of the portland cement, the silica fume, the fly ash and the slag is 13: 1: 4: 2.
preferably, the ratio of the weight of the water to the total weight of the portland cement, silica fume, fly ash, and slag is 0.35 to 0.41.
Preferably, the river sand is medium sand, and the fineness modulus is 2.5-2.6.
Preferably, the water reducing agent is a polycarboxylic acid water reducing agent, a naphthalene water reducing agent or an amino sulfur water reducing agent, and the water reducing efficiency is not lower than 25%.
Preferably, the air-entraining agent is a rosin air-entraining agent, a saponin air-entraining agent or a fatty alcohol air-entraining agent.
A method for preparing recycled concrete capable of being repeatedly used in cold regions comprises the following steps,
s1: weighing the components according to the weight parts of the recycled concrete which can be repeatedly used in cold regions;
s2: adding the recycled coarse aggregate and river sand into a stirring container and uniformly stirring;
s3: adding 45-55% of water into a stirring container and uniformly stirring;
s4: adding the portland cement, the silica fume, the fly ash and the slag into a stirring container and uniformly stirring;
s5: and adding the water reducing agent, the air entraining agent and the residual water into a stirring container, and uniformly stirring to obtain the recycled concrete capable of being repeatedly utilized in cold regions.
Preferably, in the step S2, the stirring time is 60 to 100S;
in the step S3, the stirring time is 60-100S;
in the step S4, the stirring time is 30-50S;
in the step S5, the stirring time is 120-150S.
The invention has the beneficial effects that:
1) the mixing proportion of the invention is reasonable, the slump of the prepared recycled concrete which can be used repeatedly in cold regions is more than 160mm, the compressive strength is more than 35MPa, the rupture strength is more than 4MPa, the mass loss rate after repeated freezing and thawing for 300 times is less than 3%, the relative dynamic elastic modulus is more than 70%, and the performance is good.
2) The second generation recycled coarse aggregate obtained by freezing and thawing the recycled concrete which can be repeatedly utilized in cold regions and crushing for 300 times is more than 2290kg/m in apparent density3The concrete has the advantages that the water absorption rate is less than 7%, the crushing value is less than 25%, the firmness (mass loss) is less than 12%, the content of micro powder is less than 2.5%, the content of mud blocks is less than 1%, the content of needle-shaped particles is less than 8%, the physical properties meet the use requirements of III-class recycled coarse aggregates, the concrete can be used as structural concrete, second-generation recycled concrete prepared by using the concrete has the compressive strength of more than 35MPa, the breaking strength of more than 3.5MPa, the mass loss rate after 300 times of freeze thawing is less than 4%, the relative dynamic elastic modulus is more than 65%, various properties are good, and the repeated utilization of waste recycled concrete in cold regions is realized.
Detailed Description
The present invention will be further described with reference to the following embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, and the protection scope of the present invention is not limited thereby.
The embodiment of the invention provides recycled concrete capable of being repeatedly used in a cold area, which comprises the following components in parts by weight: 860-912 parts of recycled coarse aggregate, 692-736 parts of river sand, 286-312 parts of portland cement, 22-24 parts of silica fume, 88-96 parts of fly ash, 44-48 parts of slag, 2.2-2.4 parts of a water reducing agent, 0.26-0.29 part of an air entraining agent and 169-182 parts of water. Portland cement, silica fume, fly ash and slag are used as cementing materials.
The recycled coarse aggregate and the sand play a role of a framework, various cementing materials are mixed with water and then wrap the aggregate, so that the recycled concrete has certain workability, wherein silica fume, fly ash and slag can play a morphological effect, an active effect and a micro-aggregate filling effect in the recycled concrete due to the activity and density difference of the silica fume, the fly ash and the slag, a super superposition effect is formed, the internal pores and an interface transition area of the recycled concrete are further compacted, the mechanical property and the frost resistance of the recycled concrete are improved, the capability of resisting freeze-thaw damage is stronger, meanwhile, due to secondary hydration of mortar, partial damage is compensated, and the physical and mechanical properties of the second-generation recycled coarse aggregate are better.
In an alternative embodiment of the invention, the recycled coarse aggregate is commercial I type recycled coarse aggregate or II type recycled coarse aggregate specified in GB/T25177-2010, and the apparent density of the recycled coarse aggregate is more than 2350kg/m3The water absorption is less than 5%, the crushing value is less than 20%, the firmness (mass loss) is less than 10%, the content of micropowder is less than 2%, the content of mud blocks is less than 0.7%, the content of needle-shaped particles is less than 10%, and the particle size is 5-25 mm.
In an alternative embodiment of the invention, the portland cement has a strength rating of not less than 42.5.
In an alternative embodiment of the present invention, the weight ratio of portland cement, silica fume, fly ash, and slag is 13: 1: 4: 2.
in an alternative embodiment of the present invention, the ratio of the weight of water to the total weight of the cementitious material (portland cement, silica fume, fly ash, and slag) is 0.35 to 0.41.
In an optional embodiment of the invention, the river sand is medium sand, and the fineness modulus is 2.5-2.6.
In an optional embodiment of the invention, the water reducing agent is a polycarboxylic acid water reducing agent, a naphthalene water reducing agent or an amino sulfur water reducing agent, and the water reducing efficiency is not lower than 25%. Among them, a polycarboxylic acid type water reducing agent is a preferable water reducing agent.
In an alternative embodiment of the present invention, the air-entraining agent is a rosin-based air-entraining agent, a saponin-based air-entraining agent, or a fatty alcohol-based air-entraining agent. Among these, fatty alcohol-based air-entraining agents are preferable air-entraining agents.
The embodiment of the invention also provides a preparation method of recycled concrete capable of being repeatedly used in cold regions, which comprises the following steps:
s1: weighing the components according to the weight parts of the recycled concrete which can be repeatedly used in cold regions;
s2: adding the recycled coarse aggregate and river sand into a stirring container, and stirring for 60-100 s;
s3: adding 45-55% of water into a stirring container and stirring for 60-100 s;
s4: adding portland cement, silica fume, fly ash and slag into a stirring container and stirring for 30-50 s;
s5: and adding the water reducing agent, the air entraining agent and the residual water into a stirring container, stirring for 120-150 s, and uniformly mixing to obtain the recycled concrete which can be repeatedly used in a cold area.
In an alternative embodiment of the invention, the mixing vessel is a blender.
The slump of the recycled concrete is measured according to GB/T50080-2016 standard on the performance test method of common concrete mixtures, the 28d compressive strength and the 28d flexural strength obtained according to GB/T50081-2019 standard on the mechanical property test method of common concrete are measured, and the performance of the prepared recycled concrete capable of being repeatedly utilized in cold regions is characterized according to the mass loss rate and the relative dynamic elastic modulus obtained after 300 times of quick freeze-thaw tests according to GB/T50082-2009 standard on the long-term performance and durability test method of common concrete.
In addition, the invention measures the physical properties of the prepared recycled concrete which can be used repeatedly in cold regions after being frozen and thawed 300 times according to GB/T25177-2010 recycled coarse aggregate for concrete, the recycled concrete is crushed to obtain the second-generation recycled coarse aggregate with the particle size of more than 4.75mm, the second-generation recycled concrete is prepared by using the recycled concrete, and the 28d compressive strength and the 28d flexural strength of the second-generation recycled concrete, and the mass loss rate and the relative dynamic elastic modulus of the second-generation recycled concrete after 300 times of rapid freeze-thaw tests are measured to represent the properties of the second-generation recycled concrete.
In the following examples, the air entraining agent was a fatty alcohol type air entraining agent available from Jiangsu Subo New Material Co., Ltd, model number GYQ-E100, and the main component was fatty alcohol polyoxyethylene ether. The water reducing agent is a polycarboxylic acid water reducing agent purchased from Jiangsu Subo New materials GmbH, the model is PCA-I, and the main component is a butenedioic acid-acrylic acid-allyl polyethylene glycol copolymer.
Example one
1) Preparing recycled concrete:
the method comprises the following steps: 883 parts of recycled coarse aggregate, 736 parts of river sand, 286 parts of ordinary portland cement, 22 parts of silica fume, 88 parts of fly ash, 44 parts of slag, 182 parts of water, 2.2 parts of polycarboxylic acid water reducing agent and 0.26 part of GYQ-E100 air entraining agent. Wherein the apparent density of the recycled coarse aggregate is 2442kg/m3The water absorption was 3.8%, the crush value was 15.6%, the firmness (mass loss) was 9.2%, the content of fine powder was 0.8%, the content of clod was 0.3%, the content of needle-like particles was 6.7%, and the particle size was 5 to 25 mm. The river sand is medium sand, and the fineness modulus is 2.6. The strength grade of the ordinary portland cement is 42.5, and the mass ratio of the ordinary portland cement, the silica fume, the fly ash and the slag to the total cementing material is 13: 1: 4: 2, the water-to-glue ratio is 0.41. The water reducing efficiency of the polycarboxylic acid water reducing agent is 25%.
Step two: adding the recycled coarse aggregate and river sand into a stirrer and stirring for 60 s.
Step three: 91 parts of water was added to the stirrer and stirred for 60 seconds.
Step four: and adding the portland cement, the silica fume, the fly ash and the slag into a stirrer and stirring for 30 s.
Step five: and adding the polycarboxylic acid water reducing agent, GYQ-E100 air entraining agent and the remaining 91 parts of water into a stirrer, stirring for 120s, and uniformly mixing to obtain the recycled concrete.
2) Preparing second-generation recycled concrete:
freezing and thawing the recycled concrete prepared in the step five for 300 times to obtain waste recycled concrete, and crushing the waste recycled concrete to obtain second-generation recycled coarse aggregate with the particle size of more than 4.75 mm; and (4) replacing the recycled coarse aggregate used in the step one with the second-generation recycled coarse aggregate, keeping the other components unchanged, and preparing the second-generation recycled concrete according to the content of each component in the step one and the steps two-five.
Example two
1) Preparing recycled concrete:
the method comprises the following steps: 897 parts of recycled coarse aggregate, 718 parts of river sand, 299 parts of ordinary portland cement, 23 parts of silica fume, 92 parts of fly ash, 46 parts of slag, 175 parts of water, 2.3 parts of a polycarboxylic acid water reducing agent and 0.28 part of GYQ-E100 of an air entraining agent are prepared according to the parts by weight. Wherein the apparent density of the recycled coarse aggregate is 2442kg/m3The water absorption was 3.8%, the crush value was 15.6%, the firmness (mass loss) was 9.2%, the content of fine powder was 0.8%, the content of clod was 0.3%, the content of needle-like particles was 6.7%, and the particle size was 5 to 25 mm. The river sand is medium sand, and the fineness modulus is 2.6. The strength grade of the ordinary portland cement is 42.5, and the mass ratio of the ordinary portland cement, the silica fume, the fly ash and the slag to the total cementing material is 13: 1: 4: 2, the water-to-glue ratio is 0.38. The water reducing efficiency of the polycarboxylic acid water reducing agent is 25%.
Step two: adding the recycled coarse aggregate and river sand into a stirrer and stirring for 70 s;
step three: adding 87.5 parts of water into the stirrer and stirring for 70 s;
step four: adding the portland cement, the silica fume, the fly ash and the slag into a stirrer and stirring for 40 s;
step five: and adding the polycarboxylic acid water reducing agent, GYQ-E100 air entraining agent and the remaining 87.5 parts of water into a stirrer, stirring for 130s, and uniformly mixing to obtain the recycled concrete.
2) Preparing second-generation recycled concrete:
freezing and thawing the recycled concrete prepared in the step five for 300 times to obtain waste recycled concrete, and crushing the waste recycled concrete to obtain second-generation recycled coarse aggregate with the particle size of more than 4.75 mm; and (4) replacing the recycled coarse aggregate used in the step one with the second-generation recycled coarse aggregate, keeping the other components unchanged, and preparing the second-generation recycled concrete according to the content of each component in the step one and the steps two-five.
EXAMPLE III
1) Preparing recycled concrete:
the method comprises the following steps: preparing regenerated crude material according to weight portion912 parts of aggregate, 692 parts of river sand, 312 parts of ordinary portland cement, 24 parts of silica fume, 96 parts of fly ash, 48 parts of slag, 169 parts of water, 2.4 parts of polycarboxylic acid water reducing agent and 0.29 part of GYQ-E100 air entraining agent. Wherein the apparent density of the recycled coarse aggregate is 2442kg/m3The water absorption was 3.8%, the crush value was 15.6%, the firmness (mass loss) was 9.2%, the content of fine powder was 0.8%, the content of clod was 0.3%, the content of needle-like particles was 6.7%, and the particle size was 5 to 25 mm. The river sand is medium sand, and the fineness modulus is 2.6. The strength grade of the ordinary portland cement is 42.5, and the mass ratio of the ordinary portland cement, the silica fume, the fly ash and the slag to the total cementing material is 13: 1: 4: 2, the water-to-glue ratio is 0.35. The water reducing efficiency of the polycarboxylic acid water reducing agent is 25%.
Step two: adding the recycled coarse aggregate and river sand into a stirrer and stirring for 90 s;
step three: adding 84.5 parts of water into the stirrer and stirring for 90 seconds;
step four: adding the portland cement, the silica fume, the fly ash and the slag into a stirrer and stirring for 50 s;
step five: and adding the polycarboxylic acid water reducing agent, GYQ-E100 air entraining agent and the remaining 84.5 parts of water into a stirrer, stirring for 150s, and uniformly mixing to obtain the recycled concrete.
2) Preparing second-generation recycled concrete:
freezing and thawing the recycled concrete prepared in the step five for 300 times to obtain waste recycled concrete, and crushing the waste recycled concrete to obtain second-generation recycled coarse aggregate with the particle size of more than 4.75 mm; and (4) replacing the recycled coarse aggregate used in the step one with the second-generation recycled coarse aggregate, keeping the other components unchanged, and preparing the second-generation recycled concrete according to the content of each component in the step one and the steps two-five.
Comparative example
1) Preparing recycled concrete:
the method comprises the following steps: 883 parts of recycled coarse aggregate, 736 parts of river sand, 440 parts of ordinary portland cement, 182 parts of water, 1 part of polycarboxylic acid water reducing agent and 0.2 part of GYQ-E100 air entraining agent. Wherein the apparent density of the recycled coarse aggregate is 2442kg/m3Water absorption of 3.8% and crush value of 15.6%, firmness (mass loss)Loss) is 9.2 percent, the content of micro powder is 0.8 percent, the content of mud blocks is 0.3 percent, the content of needle-shaped particles is 6.7 percent, and the particle diameter is 5-25 mm. The river sand is medium sand, and the fineness modulus is 2.6. The strength grade of the ordinary portland cement is 42.5, and the water-cement ratio is 0.41. The water reducing efficiency of the polycarboxylic acid water reducing agent is 25%.
Step two: adding the recycled coarse aggregate and river sand into a stirrer and stirring for 60 s;
step three: adding 91 parts of water into a stirrer and stirring for 60 s;
step four: adding the Portland cement into a stirrer and stirring for 30 s;
step five: and adding the polycarboxylic acid water reducing agent, GYQ-E100 air entraining agent and the remaining 91 parts of water into a stirrer, stirring for 120s, and uniformly mixing to obtain the recycled concrete.
2) Preparation of second-generation recycled concrete
Step six: freezing and thawing the prepared recycled concrete for 300 times to obtain waste recycled concrete, and crushing the waste recycled concrete to obtain second-generation recycled coarse aggregate with the particle size of more than 4.75 mm; and (4) replacing the recycled coarse aggregate used in the step one with the second-generation recycled coarse aggregate, keeping the other components unchanged, and preparing the second-generation recycled concrete according to the content of each component in the step one and the steps two-five.
TABLE 1 mechanical and Frost Property data of recycled concrete
TABLE 2 Performance data for second generation recycled coarse aggregate
TABLE 3 mechanics and frost resistance data of second generation recycled concrete
As can be seen from Table 1, the recycled concrete prepared by the method disclosed by the invention and capable of being repeatedly used in cold regions has the slump value of more than 160mm, the compressive strength of more than 35MPa, the breaking strength of more than 4MPa, the mass loss rate of less than 3% after repeated freezing and thawing for 300 times, the relative dynamic elastic modulus of more than 70% and good performance. In the comparative example, only a small amount of water reducing agent and air entraining agent is added, so that the recycled concrete has better working performance, and meanwhile, the cementing material is only cement and cannot exert the super superposition effect brought by mineral admixtures (silica fume, fly ash and slag), so that the recycled concrete has a poorer pore structure and performance.
As can be seen from Table 2, the physical and mechanical properties of the second-generation recycled coarse aggregate obtained by crushing, freezing and thawing the waste recycled concrete for 300 times meet the requirements of the III-type recycled coarse aggregate in GB/T25177-2010 recycled coarse aggregate for concrete, and the second-generation recycled coarse aggregate can be applied to structural concrete again. As the recycled concrete in the embodiment is added with the mineral admixture (silica fume, fly ash and slag), secondary hydration of mortar occurs in a quick freezing test, and partial freeze-thaw damage is compensated, so that the physical property of the second generation recycled coarse aggregate in the embodiment is superior to that of a comparative example.
As can be seen from Table 3, the compressive strength of the second-generation recycled concrete is greater than 35MPa, the flexural strength is greater than 3.5MPa, the mass loss rate after 300 times of freeze thawing is less than 4%, the relative dynamic elastic modulus is greater than 65%, the performances are good, and the performance requirements of the structural concrete in the cold region are met.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
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Application publication date: 20220128 Assignee: Shandong Hongke Construction Project Management Co.,Ltd. Assignor: CHANGZHOU University Contract record no.: X2023980050999 Denomination of invention: A recycled concrete that can be reused multiple times in cold regions and its preparation method Granted publication date: 20221104 License type: Common License Record date: 20231209 |