CN111484287A - High-strength recycled concrete capable of being printed in 3D mode and preparation method thereof - Google Patents
High-strength recycled concrete capable of being printed in 3D mode and preparation method thereof Download PDFInfo
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- CN111484287A CN111484287A CN202010296758.XA CN202010296758A CN111484287A CN 111484287 A CN111484287 A CN 111484287A CN 202010296758 A CN202010296758 A CN 202010296758A CN 111484287 A CN111484287 A CN 111484287A
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
- C04B28/04—Portland cements
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B14/02—Granular materials, e.g. microballoons
- C04B14/04—Silica-rich materials; Silicates
- C04B14/06—Quartz; Sand
- C04B14/068—Specific natural sands, e.g. sea -, beach -, dune - or desert sand
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y70/00—Materials specially adapted for additive manufacturing
- B33Y70/10—Composites of different types of material, e.g. mixtures of ceramics and polymers or mixtures of metals and biomaterials
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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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- 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
- C04B2201/52—High compression strength concretes, i.e. with a compression strength higher than about 55 N/mm2, e.g. reactive powder concrete [RPC]
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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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- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
Abstract
The invention relates to the field of building 3D printing and waste recycling, in particular to high-strength recycled concrete capable of being printed in a 3D mode and a preparation method thereof. The high-strength recycled concrete capable of being printed in the 3D mode comprises the following components in parts by weight: cement: 730 and 1210 parts; fly ash: 75-235 parts of a modifier; silica fume: 55-220 parts; fine sand: 777 and 1356 parts; coarse sand: 354 and 661 portions; steel fiber: 8-19 parts; water reducing agent: 11.1-23.7 parts; nano clay: 7.1-15.3 parts; cellulose: 0.9-4.2 parts; water: 187-432 parts. The high-strength recycled concrete capable of being printed in 3D disclosed by the invention meets the requirements of pumpability, extrudability and constructability of 3D printing ink for buildings, and also achieves the characteristic of high strength, and is beneficial to realizing high-quality application of engineering by using a 3D printing technology for buildings.
Description
Technical Field
The invention relates to the field of building 3D printing and waste recycling, in particular to high-strength recycled concrete capable of being printed in a 3D mode and a preparation method thereof.
Background
The 3D printed concrete is an intelligent construction technology which takes concrete as a printing ink material and applies a 3D printing technology to the field of constructional engineering. The 3D printing technology completes the manufacture of the solid structure in a mode of overlapping materials layer by layer, and has the advantages of no need of a mold, shortened manufacturing period, reduced cost and the like. The application of the 3D printing technology in the field of buildings can not only greatly reduce the construction cost and improve the construction efficiency, but also improve the safety, stability and accuracy of construction, and simultaneously enable a complex construction form to be possible.
Meanwhile, China is still in the peak period of infrastructure, and the demand of building materials and the discharge of building wastes are huge. In 2017, more than 20 hundred million tons of building wastes are generated in China, wherein the content of the waste concrete is about 40 percent at most, the waste concrete is crushed and processed into recycled aggregate to be made into recycled concrete, the recycling utilization rate of the waste concrete in most developed countries can reach more than 90 percent, and in China, although the industry is developed for over a decade, the recycling utilization rate is still less than 10 percent. The application of the recycled concrete material to 3D printing brings a chance for further development of the construction waste recycling industry.
However, most building 3D printing materials at present have low compressive strength, rupture strength and splitting strength, and cannot be applied in high quality, so that further popularization and application of building 3D printing are restricted.
Disclosure of Invention
In view of the above disadvantages of the prior art, the present invention aims to provide a high strength recycled concrete capable of 3D printing and a preparation method thereof, which overcome the defects that the existing building 3D printing material cannot effectively utilize building waste, and has low strength and is easy to damage. The 3D printing high-strength recycled concrete uses fly ash, silica fume, recycled fine sand and recycled coarse sand, realizes resource recycling of wastes, and has high environmental benefit and social benefit.
Specifically, the technical scheme of the invention is as follows:
the invention discloses a high-strength recycled concrete capable of being printed in a 3D mode, which comprises the following components in parts by weight:
cement: 730 and 1210 parts;
fly ash: 75-235 parts of a modifier;
silica fume: 55-220 parts;
fine sand: 777 and 1356 parts;
coarse sand: 354 and 661 portions;
steel fiber: 10-19 parts;
water reducing agent: 11.1-23.7 parts;
nano clay: 7.1-15.3 parts;
cellulose: 0.9-4.2 parts;
water: 187-432 parts.
Preferably, the cement is P.I. 62.5-grade portland cement which is good in compatibility with a polycarboxylic acid water reducer; the fly ash is I-grade low-calcium fly ash; the silica fume conforms to the specification of CAN/CSA A3000 standard.
Preferably, the fine sand comprises natural sand and reclaimed sand, and the natural sand consists of river sand with hard texture and high-quality quartz sand with good aggregation; the fineness modulus of the river sand is less than 2.2; SiO of the quartz sand2The content is more than 96 percent, the grading is good, and the maximum grain size is 600 microns; the recycled fine sand is particles with the particle size of 0.6mm-2.1mm obtained by crushing waste concrete, belongs to recycled fine aggregate for I-type concrete and mortar specified in GB/T25176-2010, and has the particle grading of a 1-grade zone, the firmness index is less than 5.0 percent, and the crushing index is less than 15 percent;
preferably, the fine sand has a good particle shape and an impurity content of less than 0.1%.
Preferably, the coarse sand comprises natural coarse sand and regenerated coarse sand, the natural coarse sand is obtained by grinding hard and compact basalt, and the volume density of the basalt is 3.1-3.3g/cm3The compression strength can reach 300MPa, and the natural coarse sand has good grading grain size ranging from 2.1mm to 4.3 mm;
preferably, the reclaimed coarse sand is particles with the particle size of 2.1mm-4.3mm, which are obtained by crushing waste concrete;
preferably, the coarse sand particles are good in shape, and the impurity content is less than 0.1%.
Preferably, the steel fiber is copper-plated flat steel fiber, the diameter is 0.19mm-0.23mm, the length is 6mm-18mm, and the tensile strength is 2500MPa-3000 MPa.
Preferably, the 3D-printable high-strength recycled concrete comprises any one or more of the following conditions:
1) the water reducing agent is a polycarboxylic acid water reducing agent;
2) the nano clay is nano purified attapulgite clay powder for concrete;
3) the cellulose is carboxymethyl cellulose or lignocellulose.
4) The water is tap water.
Preferably, the waste concrete for preparing the reclaimed sand and the reclaimed macadam has a single source, is prepared from the same batch of concrete with original design strength of C60 and service life of 30 years, and is prepared by a crusher with the same model of the same waste concrete crushing plant; the water consumption in the matching design takes the water absorption of the regenerated fine sand and the regenerated coarse sand into consideration; the single source and water absorption considerations serve to reduce the variability of the 3D printable high strength recycled concrete to a coefficient of variation of less than 5%.
Specifically, the water absorption rate of the regenerated fine sand and the regenerated coarse sand is 5% -20%, and the water absorption rate needs to be particularly considered in the preparation process of the high-strength regenerated concrete capable of being printed in a 3D mode. Assuming that the amounts of cement, natural sand, natural crushed stone and water in a building 3D printing material formulation without reclaimed fine sand and reclaimed coarse sand are a, b, c and D, respectively, then when the reclaimed fine sand and the reclaimed coarse sand are replaced by m% and n% respectively, and assuming that the water absorption rates of the reclaimed fine sand and the reclaimed coarse sand are x% and y%, the amount of water used in the building 3D printing material formulation will be W ═ D + b:% x% + c:% y%, and at the same time the water-cement ratio in the formulation will be a/(D + b:% x% + c:% y%) from a/D.
Preferably, the combination of river sand, quartz sand, reclaimed fine sand, natural coarse sand and reclaimed coarse sand is a combination which obtains the optimal bulk density after calculating the multi-component combined bulk density based on Sedran and De L arrard equations (ref: L arrard F D, Sedran T. optimization of ultra-high-performance concrete by the use of a packing model [ J ]. center and C-concrete Research,1994,24(6):997-1009), the silica fume and the fly ash have further micro-aggregate filling effect on the combined material, the steel fiber is used for reducing the brittleness of the material, and the combined material has the characteristics of low fineness, high activity and good gradation, so that the internal defects of the combined material after hydration are reduced to the minimum to obtain the high-strength characteristic of the high-strength reclaimed concrete.
Preferably, the water reducing agent, the nano clay and the cellulose are used for adjusting the performance of the high-strength recycled concrete, so that the fluidity of the high-strength recycled concrete is controlled to be 160-220mm, and the plastic yield strength is controlled to be 1.5-2.5 kPa; the adjusted mixed material is easy to pump and extrude, continuous in printing, uniform in printing size, stable in printing shape, and capable of continuously printing and stacking 30 layers without obvious deformation, and the pumpability, the extrudability and the constructability required by 3D printing are met, and the printing window time is 30-90 min.
The invention discloses a method for preparing high-strength recycled concrete capable of being printed in a 3D mode, which comprises the following steps: step one, mixing cement, silica fume, fly ash, fine sand, coarse sand, steel fiber, nano clay and cellulose in proportion and stirring uniformly to obtain a mixture I; and step two, uniformly mixing the water reducing agent and the water in proportion, adding the mixture into the mixture I for three times, and stirring until the mixture is uniform, so as to obtain the high-strength recycled concrete mixture capable of being printed in a 3D mode.
Preferably, the stirring conditions in the first step and the second step are as follows: the stirring speed is 650-1200rpm, and the stirring time is 3-10 min.
The third aspect of the invention discloses application of the high-strength recycled concrete capable of being printed in a 3D mode or the preparation method in the field of recycled materials.
On the basis of the common general knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily without departing from the concept and the protection scope of the invention.
Compared with the prior art, the invention has the following remarkable advantages and effects:
according to the invention, high-grade cement is adopted, coarse and fine sand and steel fiber are selected and closely stacked, and additives are added for adjustment, so that the material not only meets the requirements of pumpability, extrudability and constructability of building 3D printing ink, but also has the advantage of high strength. The building 3D high-strength recycled concrete solves the disadvantages that a building 3D printing material in the existing reinforcement-free construction is low in strength and easy to damage, and is beneficial to the conversion of a building 3D printing technology from a laboratory stage to an engineering application stage; meanwhile, the building 3D high-strength recycled concrete uses a large amount of fly ash, silica fume, recycled fine sand and recycled coarse sand, takes resource recycling of wastes into consideration, and has high environmental benefit and social benefit.
Detailed Description
The technical solutions of the present invention are described in detail below with reference to examples, but the present invention is not limited to the scope of the examples.
The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions. The reagents and starting materials used in the present invention are commercially available.
Example 1
A high-strength recycled concrete capable of being printed in a 3D mode and a preparation method thereof are disclosed, and the high-strength recycled concrete comprises the following components in parts by weight: 1000 parts of cement, 150 parts of fly ash, 150 parts of silica fume, 200 parts of river sand, 400 parts of quartz sand, 400 parts of regenerated fine sand, 300 parts of basalt coarse sand, 200 parts of regenerated coarse sand, 14 parts of steel fiber, 20 parts of water reducing agent, 9.1 parts of nano clay, 3.7 parts of cellulose and 225 parts of water.
Wherein the cement is P.I 62.5-grade portland cement, and the fly ash is I-grade low-calcium fly ash; the silica fume accords with the specification of CAN/CSAA3000 standard; the fineness modulus of river sand is less than 2.2, and the SiO content of quartz sand2The content is more than 96 percent, the grading is good, and the maximum grain size is 600 microns; the basalt grit gradation is good, and the grain size range is 2.1mm-4.3 mm; the recycled fine sand is particles with the particle size of 0.6mm-2.1mm obtained by crushing waste concrete, belongs to I-type concrete and recycled fine aggregate for mortar specified in GB/T25176-,the grain composition is a 1-grade zone, the firmness index is less than 5.0 percent, and the crushing index is less than 15 percent; the reclaimed coarse sand is particles with the particle size of 2.1mm-4.3mm obtained by crushing waste concrete; the water absorption rates of the regenerated fine sand and the regenerated coarse sand are respectively 12% and 7%; the fine sand and the coarse sand have good particle shapes, and the impurity content is less than 0.1 percent; the steel fiber is copper-plated flat steel fiber with the diameter of 0.2mm, the length of 6mm-18mm and other lengths, and the tensile strength of 2800 MPa; the water reducing agent is a polycarboxylic acid water reducing agent, the nano clay is nano purified attapulgite clay powder for concrete, and the cellulose is carboxypropyl methyl cellulose or lignocellulose; the water is ordinary tap water.
The preparation method of the high-strength recycled concrete capable of being printed in the 3D mode comprises the following steps: the method comprises the following steps: step one, mixing cement, silica fume, fly ash, fine sand, coarse sand, steel fiber, nano clay and cellulose in proportion and stirring uniformly to obtain a mixture I; and step two, uniformly mixing the water reducing agent and the water in proportion, adding the mixture into the mixture I for three times, and stirring until the mixture is uniform, so as to obtain the high-strength recycled concrete mixture capable of being printed in a 3D mode. Wherein the stirring conditions in the first step and the second step are as follows: the stirring speed is 650-1200rpm, and the stirring time is 3-10 min.
Example 2
A high-strength recycled concrete capable of being printed in a 3D mode and a preparation method thereof are disclosed, and the high-strength recycled concrete comprises the following components in parts by weight: 1100 parts of cement, 100 parts of fly ash, 100 parts of silica fume, 200 parts of river sand, 400 parts of quartz sand, 400 parts of regenerated fine sand, 300 parts of basalt coarse sand, 200 parts of regenerated coarse sand, 10 parts of steel fiber, 17 parts of water reducing agent, 8.3 parts of nano clay, 3.5 parts of cellulose and 265 parts of water.
Wherein the cement is P.I 62.5-grade portland cement, and the fly ash is I-grade low-calcium fly ash; the silica fume accords with the specification of CAN/CSAA3000 standard; the fineness modulus of river sand is less than 2.2, and the SiO content of quartz sand2The content is more than 96 percent, the grading is good, and the maximum grain size is 600 microns; the basalt grit gradation is good, and the grain size range is 2.1mm-4.3 mm; the recycled fine sand is particles with the particle size of 0.6mm-2.1mm obtained by crushing waste concrete, belongs to the recycled fine aggregate for I-type concrete and mortar specified in GB/T25176-The grain composition is a 1-grade zone, the firmness index is less than 5.0 percent, and the crushing index is less than 15 percent; the reclaimed coarse sand is particles with the particle size of 2.1mm-4.3mm obtained by crushing waste concrete; the water absorption rates of the regenerated fine sand and the regenerated coarse sand are respectively 12% and 7%; the fine sand and the coarse sand have good particle shapes, and the impurity content is less than 0.1 percent; the steel fiber is copper-plated flat steel fiber with the diameter of 0.2mm, the length of 6mm-18mm and other lengths, and the tensile strength of 2800 MPa; the water reducing agent is a polycarboxylic acid water reducing agent, the nano clay is nano purified attapulgite clay powder for concrete, and the cellulose is carboxypropyl methyl cellulose or lignocellulose; the water is ordinary tap water.
The preparation method of the high-strength recycled concrete capable of being printed in the 3D mode comprises the following steps: the method comprises the following steps: step one, mixing cement, silica fume, fly ash, fine sand, coarse sand, steel fiber, nano clay and cellulose in proportion and stirring uniformly to obtain a mixture I; and step two, uniformly mixing the water reducing agent and the water in proportion, adding the mixture into the mixture I for three times, and stirring until the mixture is uniform, so as to obtain the high-strength recycled concrete mixture capable of being printed in a 3D mode. Wherein the stirring conditions in the first step and the second step are as follows: the stirring speed is 650-1200rpm, and the stirring time is 3-10 min.
Example 3
A high-strength recycled concrete capable of being printed in a 3D mode and a preparation method thereof are disclosed, and the high-strength recycled concrete comprises the following components in parts by weight: 900 parts of cement, 200 parts of fly ash, 200 parts of silica fume, 200 parts of river sand, 400 parts of quartz sand, 400 parts of regenerated fine sand, 300 parts of basalt coarse sand, 200 parts of regenerated coarse sand, 12 parts of steel fiber, 18.5 parts of water reducing agent, 10.3 parts of nano clay, 4.3 parts of cellulose and 240 parts of water.
Wherein the cement is P.I 62.5-grade portland cement, and the fly ash is I-grade low-calcium fly ash; the silica fume accords with the specification of CAN/CSAA3000 standard; the fineness modulus of river sand is less than 2.2, and the SiO content of quartz sand2The content is more than 96 percent, the grading is good, and the maximum grain size is 600 microns; the basalt grit gradation is good, and the grain size range is 2.1mm-4.3 mm; the recycled fine sand is particles with the particle size of 0.6mm-2.1mm obtained by crushing waste concrete, belongs to the recycled fine aggregate for I-type concrete and mortar specified in GB/T25176-The grain composition is a 1-grade zone, the firmness index is less than 5.0 percent, and the crushing index is less than 15 percent; the reclaimed coarse sand is particles with the particle size of 2.1mm-4.3mm obtained by crushing waste concrete; the water absorption rates of the regenerated fine sand and the regenerated coarse sand are respectively 12% and 7%; the fine sand and the coarse sand have good particle shapes, and the impurity content is less than 0.1 percent; the steel fiber is copper-plated flat steel fiber with the diameter of 0.2mm, the length of 6mm-18mm and other lengths, and the tensile strength of 2800 MPa; the water reducing agent is a polycarboxylic acid water reducing agent, the nano clay is nano purified attapulgite clay powder for concrete, and the cellulose is carboxypropyl methyl cellulose or lignocellulose; the water is ordinary tap water.
The preparation method of the high-strength recycled concrete capable of being printed in the 3D mode comprises the following steps: the method comprises the following steps: step one, mixing cement, silica fume, fly ash, fine sand, coarse sand, steel fiber, nano clay and cellulose in proportion and stirring uniformly to obtain a mixture I; and step two, uniformly mixing the water reducing agent and the water in proportion, adding the mixture into the mixture I for three times, and stirring until the mixture is uniform, so as to obtain the high-strength recycled concrete mixture capable of being printed in a 3D mode. Wherein the stirring conditions in the first step and the second step are as follows: the stirring speed is 650-1200rpm, and the stirring time is 3-10 min.
Comparative example 1
The common building 3D printing mortar comprises the following components in parts by weight: 1000 parts of cement, 1000 parts of natural sand, 1.5 parts of a water reducing agent, 0.5 part of sodium gluconate, 3.5 parts of nano clay and 370 parts of water. Wherein, the cement is P.O 42.5.5 ordinary portland cement; the natural sand is natural fine sand, the average grain diameter is 0.25mm-0.35mm, and the water content of the natural fine sand is 4% -6%; the water reducing agent is a polycarboxylic acid water reducing agent, the sodium gluconate is sodium gluconate for concrete, and the nano clay is nano purified attapulgite clay powder for concrete; the water is ordinary tap water. The preparation method of the common building 3D printing mortar comprises the following steps: step one, mixing and stirring cement, natural sand, a water reducing agent, sodium gluconate and nano clay uniformly; and step two, mixing the mixture obtained in the step one with water and uniformly stirring to obtain the common building 3D printing mortar. Wherein, in the first and second steps, the stirring speed is 800-1200rpm, and the stirring time is 3-7 min.
Comparative example 2
The common building 3D printing regeneration mortar comprises the following components in parts by weight: 1000 parts of cement, 500 parts of natural sand, 500 parts of reclaimed sand, 1.5 parts of water reducing agent, 0.5 part of sodium gluconate, 3.5 parts of nano clay and 430 parts of water. Wherein, the cement is P.O 42.5.5 ordinary portland cement; the natural sand is natural fine sand, the average grain diameter is 0.25mm-0.35mm, and the water content of the natural fine sand is 4% -6%; the reclaimed sand is particles with the particle size of 1.25mm-4.75mm which are obtained by crushing the building waste, the building waste is waste concrete, and the water absorption rate of the reclaimed sand is 5% -15%; the water reducing agent is a polycarboxylic acid water reducing agent, the sodium gluconate is sodium gluconate for concrete, and the nano clay is nano purified attapulgite clay powder for concrete; the water is ordinary tap water. The preparation method of the common building 3D printing mortar comprises the following steps: step one, mixing and stirring cement, natural sand, a water reducing agent, sodium gluconate and nano clay uniformly; and step two, mixing the mixture obtained in the step one with water and uniformly stirring to obtain the common building 3D printing mortar. Wherein, in the first and second steps, the stirring speed is 800-1200rpm, and the stirring time is 3-7 min.
Comparative example 3
The common building C30 concrete comprises the following components in parts by weight: 461 parts of cement, 512 parts of natural sand, 1252 parts of stones and 175 parts of water. Wherein, the cement is P.O 42.5.5 ordinary portland cement; the natural sand is natural fine sand, the average grain diameter is 0.25mm-0.35mm, and the water content of the natural fine sand is 4% -6%; the stones are common broken stones; the water is ordinary tap water. The preparation method of the common building C30 concrete comprises the following steps: step one, mixing cement, natural sand and stones and stirring the mixture until the mixture is uniform; and step two, mixing the mixture obtained in the step one with water and uniformly stirring to obtain the common building C30 concrete. Wherein, in the first and second steps, the stirring speed is 500-1200rpm, and the stirring time is 1-7 min.
Comparative example 4
The building C100 concrete comprises the following components in parts by weight: 568 parts of cement, 322 parts of natural sand, 625 parts of stones, 36 parts of fly ash, 22 parts of silica fume, 8 parts of water reducing agent and 246 parts of water. Wherein, the cement is P.O 62.5.5-grade portland cement; the natural sand is natural river sand, the fineness modulus is 2.6-2.8, and the water content of the natural fine sand is 4% -6%; the stones are the mixture of limestone with hard texture and good grain shape and pebbles; the water reducing agent is a polycarboxylic acid water reducing agent; the water is ordinary tap water. The preparation method of the building C100 concrete comprises the following steps: step one, mixing and stirring cement, natural sand, pebbles, fly ash, silica fume and a water reducing agent to be uniform; and step two, mixing the mixture obtained in the step one with water and uniformly stirring to obtain the building C100 concrete. Wherein, in the first and second steps, the stirring speed is 500-1200rpm, and the stirring time is 1-7 min.
The 3D-printable high-strength recycled concrete prepared in the examples 1 to 3 and the common building 3D printing mortar, the common building 3D printing recycled mortar, the common building C30 concrete and the building C100 concrete prepared in the comparative examples 1 to 4 are respectively subjected to layer-by-layer printing or mixing pouring by a 3D printer according to a specifically set programming program to obtain the component samples of the examples and the comparative examples. And maintaining each component sample in a standard maintenance mode, wherein the temperature of the standard maintenance is 18-22 ℃, the humidity of the standard maintenance is 90-95%, and the maintenance age of the standard maintenance is 28 days. The test conditions and curing method were identical except for the material differences.
The compression strength, the breaking strength and the splitting strength of the component samples are tested, the 3D printing performance and the utilization rate of the recycled waste are evaluated, and the obtained test and evaluation results are shown in Table 1.
TABLE 1 evaluation of compressive strength, flexural strength, splitting strength of each component sample, 3D printable performance and utilization rate of recycled waste
As can be seen from table 1, the compressive strength, the flexural strength and the cleavage strength of the 3D printable high-strength recycled concrete material prepared according to the embodiment of the disclosure can reach 130MPa, 15MPa and 9.5MPa, respectively, and thus it is beneficial to the implementation of engineering high-quality application in the 3D printing technology for buildings.
In conclusion, the high-strength recycled concrete capable of being printed in 3D and the preparation method thereof are provided, high-grade cement is adopted, coarse sand and fine sand and steel fiber are selected, optimal stacking, fineness reduction, activity increase and the like are carried out, and additives are used for adjustment, so that the material meets the requirements of pumpability, extrudability and constructability of building 3D printing ink, and also achieves the characteristic of high strength, wherein the compression strength, the fracture strength and the cleavage strength can reach 130MPa, 15MPa and 9.5MPa respectively, and the building 3D printing technology is favorable for moving from a laboratory stage to an engineering application stage. Meanwhile, the building 3D high-strength recycled concrete uses a large amount of fly ash, silica fume and reclaimed sand, takes resource recycling of wastes into consideration, and has high environmental benefit and social benefit.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (10)
1. The high-strength recycled concrete capable of being printed in a 3D mode is characterized by comprising the following components in parts by weight:
cement: 730 and 1210 parts;
fly ash: 75-235 parts of a modifier;
silica fume: 55-220 parts;
fine sand: 777 and 1356 parts;
coarse sand: 354 and 661 portions;
steel fiber: 10-19 parts;
water reducing agent: 11.1-23.7 parts;
nano clay: 7.1-15.3 parts;
cellulose: 0.9-4.2 parts;
water: 187-432 parts.
2. The 3D printable high strength recycled concrete according to claim 1, wherein said cement is a p.i62.5 grade portland cement; the fly ash is I-grade low-calcium fly ash; the silica fume conforms to the specification of CAN/CSA A3000 standard.
3. The 3D printable high strength recycled concrete according to claim 1, wherein said fine sand comprises natural sand and recycled sand;
preferably, the natural sand consists of river sand with hard texture and high-quality quartz sand with good aggregation; the fineness modulus of the river sand is less than 2.2; SiO of the quartz sand2The content is more than 96 percent, the grading is good, and the maximum grain size is 600 microns;
preferably, the reclaimed sand is particles with the particle size of 0.6mm-2.1mm obtained by crushing waste concrete, belongs to I-type concrete and recycled fine aggregate for mortar specified in GB/T25176-2010, and has the particle grading of a 1-grade zone, the firmness index is less than 5.0 percent, and the crushing index is less than 15 percent;
preferably, the fine sand has a good particle shape and an impurity content of less than 0.1%.
4. The 3D printable high strength recycled concrete according to claim 1, wherein said grit comprises natural grit and recycled grit;
preferably, the natural coarse sand is obtained by grinding hard and compact basalt, and the bulk density of the basalt is 3.1-3.3g/cm3The compression strength can reach 300MPa, the obtained natural coarse sand has good gradation, and the grain size range is 2.1mm-4.3 mm;
preferably, the reclaimed coarse sand is particles with the particle size of 2.1mm-4.3mm, which are obtained by crushing waste concrete;
preferably, the coarse sand particles are good in shape, and the impurity content is less than 0.1%.
5. The 3D printable high strength recycled concrete according to claim 1, wherein the steel fibers are copper plated flat steel fibers having a diameter of 0.19mm to 0.23mm, a length of 6mm to 18mm, and a tensile strength of 2500MPa to 3000 MPa.
6. The 3D printable high strength recycled concrete according to claim 1, characterized by comprising any one or more of the following conditions:
1) the water reducing agent is a polycarboxylic acid water reducing agent;
2) the nano clay is nano purified attapulgite clay powder for concrete;
3) the cellulose is carboxymethyl cellulose or lignocellulose.
4) The water is tap water.
7. The 3D-printable high-strength recycled concrete according to claims 3, 4 and 6, wherein the waste concrete for preparing the recycled fine sand and the recycled coarse sand is from the same batch of concrete with original design strength of C60 and service life of 30 years and is prepared by the same type of crusher of the same waste concrete crushing plant; the water consumption in the matching design does not consider the water absorption of the saturated dry surface state of the regenerated fine sand and the regenerated coarse sand.
8. The 3D-printable high-strength recycled concrete according to claims 2-5, wherein the combination of river sand, quartz sand, recycled fine sand, natural coarse sand and recycled coarse sand is a combination which obtains the optimal packing density after calculating the multi-element combined packing density based on Sedran and De L arrard equations.
9. The 3D-printable high-strength recycled concrete according to claim 6, wherein the water reducing agent, the nanoclay and the cellulose are used for adjusting the working performance of the high-strength recycled concrete, so that the fluidity of the high-strength recycled concrete is controlled to be 160-220mm, and the plastic yield strength is controlled to be 1.5-2.5 kPa; the adjusted mixed material is easy to pump and extrude, continuous printing, uniform printing size, stable printing shape and 30-90min printing window time, can continuously print and stack 30 layers without obvious deformation, and meets the requirements of pumpability, extrudability and constructability required by 3D printing.
10. The preparation method of the high-strength recycled concrete capable of being printed in a 3D mode is characterized by comprising the following steps:
step one, mixing cement, silica fume, fly ash, fine sand, coarse sand, steel fiber, nano clay and cellulose in proportion and stirring uniformly to obtain a mixture I; step two, uniformly mixing a water reducing agent and water in proportion, adding the mixture into the mixture I for three times, and stirring until the mixture is uniform, so as to obtain a high-strength recycled concrete mixture capable of being printed in a 3D mode;
preferably, the stirring conditions in the first step and the second step are as follows: the stirring speed is 650-1200rpm, and the stirring time is 3-10 min.
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