CN111848081A

CN111848081A - 3D printing concrete for coastal special-shaped structure, processing technology and application

Info

Publication number: CN111848081A
Application number: CN202010664748.7A
Authority: CN
Inventors: 罗健林; 张纪刚; 李秋义; 高嵩; 侯东帅; 滕飞
Original assignee: Qingdao University of Technology
Current assignee: Qingdao University of Technology
Priority date: 2020-07-10
Filing date: 2020-07-10
Publication date: 2020-10-30
Also published as: AU2020457381A1; AU2020457381B2; CN113307597B; JP7362083B2; WO2022007063A1; JP2022542640A; CN113307597A

Abstract

The invention particularly relates to 3D printed concrete for a coastal special-shaped structure, a processing technology and application. The existing coastal special-shaped structure 3D printing concrete also has the following defects: the anticorrosion effect of the conventional marine anticorrosion technology applied to the coastal special-shaped structure for 3D printing is not ideal, and in addition, interface bonding and thixotropy between layers of the conventional 3D printing material are insufficient. The invention provides 3D printing concrete for a coastal special-shaped structure, which is prepared from raw materials of compound cement, reclaimed sand, fly ash, polyvinyl alcohol, graphene oxide, steel fiber, organic fiber, a water reducing agent, a thickening time control agent, a mineral admixture and water. This 3D prints concrete possess good cohesiveness and moisture retention and adjacent thin layer interface cohesiveness, combines to form micro-capacitor through GO and PVA electrolyte and avoids the formation of corroding the battery in the concrete thin layer, has good ocean durability, is applied to coastal abnormal shape structural engineering and has good application prospect.

Description

3D printing concrete for coastal special-shaped structure, processing technology and application

Technical Field

The invention belongs to the technical field of 3D printing of coastal structures, and particularly relates to 3D printed concrete for a coastal special-shaped structure, a processing technology of the 3D printed concrete for the coastal special-shaped structure, and application of the concrete in preparation of the coastal special-shaped structure.

Background

The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.

At present, the digitalized, industrialized and intelligentized industrial upgrading conditions of buildings need to rapidly manufacture various concrete prefabricated components for assembling shear walls, laminated floors, laminated beams, laminated columns, prefabricated staircases, integral toilets, garbage chutes and the like for buildings with different specifications and structural types. Meanwhile, the pressure of urban ecological protection and energy conservation and emission reduction is effectively relieved by resource utilization of the construction waste. In recent years, the robot-based 3D printing digital construction method can accurately control the construction precision of various concrete special-shaped components and manufacture various curved surface components with beautiful shapes, a mold does not need to be manufactured in advance, a large amount of materials do not need to be processed in the manufacturing process, a complex forging process does not need to be performed, finally, structural optimization, material saving and energy saving are realized in production, industrialization, intellectualization and resource conservation of assembly buildings are effectively realized, and the application prospect is very wide.

Meanwhile, the reinforced concrete structure is widely applied to the field of coastal structure engineering such as offshore buildings, bridge tunnels, wind energy nuclear power stations, oil drilling platforms, harbor wharfs and the like. The 3D printing technology can be used for rapidly manufacturing coastal special-shaped structures such as well covers, rainwater grates, underground pipe galleries, egg-shaped water tanks, subway segments, honeycomb beams, superposed beams/plates and the like, and further the special-shaped structures are widely concerned.

Not neglected, the 3D printed concrete is not generally added with a steel reinforcement framework, but is doped with high-strength and high-modulus chopped steel fibers to meet the requirements of high early strength and good toughness deformation of the 3D printed concrete. However, successful 3D printing of complicated concrete members depends on the characteristics of fast setting speed, good water retention cohesiveness, good plasticity, good interlayer interface adhesion and thixotropy and the like of the corresponding concrete slurry. Meanwhile, the concrete for the coastal special-shaped structure is a porous and multi-phase heterogeneous material, seawater and oxygen can reach the surface of the steel fiber along the pores in the concrete, and corrosion free electrons are generated. The electrons are transmitted to the cathode region through the steel fibers, and negative ions in the solution are transmitted to the anode region through the pore solution, so that a large number of corrosion micro-batteries are easily formed, and premature failure is further caused.

However, when developing 3D printed concrete materials for coastal assembly structures, the inventors found that the following problems existed:

(1) the curved surface of the coastal special-shaped structure is complex and mostly of a thin-wall structure, 3D printed concrete is in a layer-by-layer printing mode, and accordingly, the 3D printed concrete is difficult to have enough concrete protective layer thickness to protect randomly dispersed steel fibers and prevent the randomly dispersed steel fibers from marine corrosion; meanwhile, common marine corrosion prevention technologies such as surface coating corrosion prevention layers and external cathodic protection cannot be used or have poor use effect for the coastal special-shaped structure with the continuously-existing printing interface layer.

(2) When the conventional 3D printing concrete material is used for printing the coastal special-shaped structure, sufficient interlayer interface bonding and thixotropy are difficult to ensure while good rheological property, water retention cohesiveness, mechanical toughness and volume stability are possessed.

(3) When the conventional 3D printing concrete material is adopted to print the coastal special-shaped structure, the construction or industrial solid waste is difficult to be synchronously recycled, the pressure of urban ecological protection and energy conservation and emission reduction is reduced, and the green and environment-friendly benefit is realized.

Disclosure of Invention

Aiming at the problems recorded in the background art, the invention aims to provide the optimized 3D printed concrete for the coastal special-shaped structure, and the printed coastal special-shaped structure has better marine corrosion prevention effect and interlayer interface bonding and thixotropic property.

Based on the technical effects, the invention provides the following technical scheme:

the invention provides 3D printing concrete for a coastal special-shaped structure, which comprises the following raw materials in parts by weight: 1 part of compound cement, 1-2 parts of reclaimed sand, 0.05-0.2 part of Fly Ash (FA), 0.005-0.05 part of polyvinyl alcohol (PVA), 0.0002-0.002 part of Graphene Oxide (GO), 0.01-0.05 part of steel fiber, 0.005-0.02 part of organic fiber, 0.005-0.01 part of water reducing agent, 0.005-0.01 part of pour regulator, 0-0.05 part of mineral admixture and 0.3-0.5 part of water; the PVA also has an oxidizing agent and a catalyst therein.

The 3D printing concrete for the coastal special-shaped structure prepared by the raw materials and the proportion can well meet the parameter printing requirements of the existing mechanical arm and the structural model, and the coastal special-shaped concrete structures with different specifications can be obtained by printing. In addition, the coastal special-shaped structure obtained by printing has good ocean durability.

According to the invention, the raw materials and the proportion of the 3D printing concrete are obtained through continuous attempts, and the 3D printing concrete has good cohesive water retention property and good interface cohesiveness of adjacent 3D printing concrete thin layers through GO with a plurality of hydroxyl, epoxy, carboxyl and other functional groups and PVA with a plurality of hydroxyl groups; the GO-PVAH @ FA-containing 3D printing concrete slurry has shear thinning effect, and good thixotropy and plasticity of the slurry are realized; meanwhile, a large number of GO-PVAH micro capacitors are formed by stably combining GO containing hydrophilic groups and PVA electrolyte, the GO-PVAH micro capacitors which are uniformly dispersed in the 3D printed concrete thin layer through FA media can store a large number of 3D printed concrete thin layer hole electrolyte and capture ions migrated by seawater media, the formation of corrosion batteries in the 3D printed concrete thin layer steel fibers is avoided, the electrochemical corrosion of the steel fibers is effectively prevented, and the chloride ion permeation resistance and seawater corrosion resistance of the whole coastal special-shaped structure are obviously improved.

Based on the above effects, in a second aspect of the present invention, there is provided a processing technology for 3D printing concrete for a coastal special-shaped structure, the processing technology includes: and printing and molding the concrete dry mixed material by the 3D printing concrete raw material of the first aspect through a 3D printing technology.

In a third aspect of the invention, the application of the 3D printed concrete for the coastal profiled structure in the first aspect in preparing the coastal profiled structure is provided.

The beneficial effects of one or more technical schemes are as follows:

(1) by adopting the 3D printing concrete for the coastal special-shaped structure and the processing technology, the coastal special-shaped structure can be quickly manufactured, and the ocean durability of the coastal special-shaped structure can be effectively guaranteed. The method creatively leads the stably dispersed GO-PVAH to pass through the surface of the wrapped FA medium, realizes the long-acting uniform distribution in a subsequent nano recycled concrete system, can effectively offset the problem that the fluidity of the recycled concrete is greatly reduced when GO is directly doped into the recycled concrete, and also brings good viscosity and thixotropic property to the corresponding nano recycled concrete slurry; meanwhile, the GO-combined PVA prepolymer containing hydrophilic groups is uniformly dispersed in the recycled concrete, so that the segregation resistance and the rheological property of the nano recycled concrete can be effectively improved; secondly, internal maintenance of the recycled aggregate and the ball lubrication effect of FA are beneficial to realizing the water retention function of corresponding recycled concrete; thirdly, the coagulation regulating effects such as the coagulation regulating agent and the like and the rapid coagulation characteristic of the compound cement further ensure the printability of the nano recycled concrete and the constructability of each layer.

A3D printing mechanism for mechanical toughness and durability of a concrete hardened body is as follows: on one hand, the surface of GO contains a plurality of hydrophilic groups such as hydroxyl, epoxy, carboxyl and the like, so that the compatibility of GO with a cement mortar system is facilitated, and meanwhile, GO can fully exert the effects of a nanocrystal core and a template, and improve the micro morphology of a corresponding recycled concrete hardened body; on the other hand, GO-PVAH hydrogel and the recycled aggregate can be well used as internal curing components in the nano recycled concrete forming process, and the subsequent water is slowly released to effectively offset the thermal shrinkage stress generated when the cement is rapidly hydrated, so that the volume stability efficiency is realized; on the other hand, the doped chopped steel fiber toughening and organic fiber bridging effects further guarantee the mechanical toughness and the crack resistance and permeability resistance of the nano recycled concrete.

(2) According to the coastal special-shaped structure 3D printing concrete, firstly, GO containing a plurality of hydroxyl groups, epoxy groups, carboxyl groups and other functional groups and PVA containing a plurality of hydroxyl groups enable the 3D printing concrete to have good cohesive water retention property, and enable adjacent 3D printing concrete thin layers to have good interface cohesiveness; secondly, the 3D printed concrete slurry has shear thinning effect due to the GO-PVAH @ FA, and good thixotropy and plasticity of the slurry are realized; thirdly, the GO-PVAH micro-capacitors containing hydrophilic groups and the PVA electrolyte are stably combined to form a large number of GO-PVAH micro-capacitors, the GO-PVAH micro-capacitors can store 3D printing concrete thin layer hole electrolyte and capture ions migrated by seawater media in a large number in 3D printing concrete thin layers through uniform dispersion of FA media, the formation of corrosion batteries in 3D printing concrete thin layer steel fibers is avoided, the electrochemical corrosion of the steel fibers is effectively prevented, and the chloride ion permeation resistance and seawater corrosion resistance of the whole coastal special-shaped structure are obviously improved.

In the nano recycled concrete, GO-PVAH is synthesized on the surface of FA, the time for adding GO-PVAH @ FA into the nano recycled concrete is effectively delayed by using an external additive aqueous solution medium, and the bottleneck problem of GO deoxidation in a strong alkaline environment is creatively avoided by combining and using admixtures such as compound cement, FA with reduced alkalinity and the like. The functions of thixotropy, chronorheology and plasticity of the nano recycled concrete slurry are realized through the surface of the FA medium wrapped by GO-PVAH, self-maintenance of the recycled aggregate and the ball lubrication effect of FA; comprehensively realizing the functions of continuous early strength, crack resistance and permeability resistance of the nano recycled concrete by using GO nano templates, organic fiber bridging and quick setting early strength effect of compound cement; the interfacial volume stabilization efficiency of the nano recycled concrete is realized through the internal curing of GO-PVAH and recycled aggregate, the micro-expansion of compound cement and the FA shrinkage reduction effect; the energy storage effect of the GO-PVAH micro-capacitor is exerted, the formation of a steel fiber corrosion micro-battery in the 3D printed coastal structure is avoided, the steel bar corrosion self-immunity effect is realized, and the printable constructability and the early strength toughening, anti-cracking, anti-permeability and corrosion self-immunity effects of 3D printed concrete of the coastal special-shaped structure and the hardening body are innovatively and synchronously realized; and the resource utilization of solid waste is synchronously widened.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

FIG. 1 is a schematic diagram of GO-PVA polymeric intercalation and GO-PVAH @ FA coating processes described in example 3;

wherein: 1-FA particles, 2-GO-PVA hydrogel layers, 21-GO sheet layers, 22-PVA polymers and 23-hydrogel. The GO-PVA intercalation structure is used for schematically reflecting the intercalation structure formed by a GO sheet layer and a PVA linear chain type polymer, and the SEM micro-morphology of FA is used for schematically reflecting the spherical hollow structure and the size specification of FA so as to be better understood by a person skilled in the art.

Fig. 2 is a flowchart of the 3D printed concrete and the processing technology of the coastal profile structure according to embodiment 3.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

Aiming at the defects in the prior art, the invention provides 3D printing concrete, a processing technology and application thereof in the rapid manufacturing of a coastal special-shaped structure. GO-PVAH is synthesized on the surface of FA, the time for adding GO-PVAH @ FA into nano recycled concrete is effectively delayed by using an external additive aqueous solution medium, and the bottleneck problem of GO deoxidation in a strong alkaline environment is creatively avoided by combining low-alkalinity compound cement and FA and other admixtures for reducing alkalinity. The thixotropic property, the rheological behavior over time and the water retention function of the nano recycled concrete slurry are realized through the surface of the GO-PVAH externally wrapped by FA media, the self-maintenance of the recycled aggregate and the ball lubrication effect of FA; comprehensively realizing the functions of continuous early strength and crack resistance and toughening of the nano recycled concrete by using GO nano templates, fiber bridging and early strength and quick setting effect of compound cement; the interfacial volume stabilization efficiency of the nano recycled concrete is realized through the internal curing of GO-PVAH and recycled aggregate, the micro-expansion of compound cement and the FA shrinkage reduction effect; the GO-PVAH micro-capacitor energy storage effect is exerted, the formation of a steel fiber corrosion micro-battery in the 3D printing coastal structure is avoided, the reinforcement corrosion self-immunity effect is realized, the printable constructability and the early strength, the volume stability, the anti-cracking, toughening and corrosion self-immunity effects of the nano recycled concrete for 3D printing of the coastal special-shaped structure are innovatively and synchronously realized; the method synchronously widens the resource utilization of solid waste, and finally has huge economic and environmental benefits in the field of quick manufacturing of coastal special-shaped structures.

Preferably, the compound cement is prepared from High Belite Sulphoaluminate Cement (HBSC), portland cement and gypsum in a proportion of 1: (0.65-1.25): (0-0.15) by weight.

The compound cement obtained by the formula has the characteristics of quick setting and early strength, and is beneficial to realizing the printable and constructable functions of corresponding nano recycled concrete by matching with the ball lubrication characteristic of FA.

Preferably, the reclaimed sand comprises coarse sand, medium sand, fine sand and ultrafine sand; wherein the medium sand rate is 27-33%.

More preferably, the coarse sand is coarse sand with a fineness modulus of 3.7-3.1 and an average particle size of more than 0.5 mm.

Further preferably, the medium sand is medium sand with fineness modulus of 3.0-2.3 and average grain diameter of 0.5-0.35 mm.

Further preferably, the fine sand is fine sand with fineness modulus of 2.2-1.6 and average grain diameter of 0.35mm-0.25 mm.

More preferably, the ultrafine sand is ultrafine sand with a fineness modulus of 1.5-0.7 and an average particle size of 0.25mm or less.

Further preferably, the mass ratio of the coarse sand, the medium sand, the fine sand and the superfine sand is 1: (1.1-2.0): (1-1.5): (1-1.5); the components in the proportion can be mixed to have a good grain grading curve.

The specific type of the reclaimed sand in the invention is not particularly limited, and in some embodiments, the reclaimed sand is the reclaimed sand which meets JC/T2548-2019 specification after demolition of construction waste or industrial waste residue and crushing and particle shaping. The self-curing effect of the nano recycled concrete slurry is effectively improved by using the recycled sand, and the solid waste recycling is synchronously widened.

Preferably, the FA is grade I FA with loss on ignition less than or equal to 5% specified in GB/T1596-2017 standard, so as to obtain better ball lubrication effect.

Preferably, the PVA is a PVA aqueous solution with an average polymerization degree of 500-600 and an alcoholysis degree of 88%; dispersing GO in PVA water solution to form stable GO-PVA pre-polymer body fluid.

Preferably, the PVA oxidant and the PVA catalyst are respectively one of sodium periodate, potassium permanganate or potassium chlorate mentioned in chinese patent CN103450489 or CN105885064A, and concentrated hydrochloric acid, dilute sulfuric acid, dilute nitric acid or boric acid, so as to intercalate the PVA prepolymer in the GO lamellar structure by an in-situ polymerization intercalation process.

Preferably, the GO is a GO powder with a single-layer rate of more than or equal to 90% and an oxygen content of 35-45% or an aqueous dispersion with a concentration of 0.05-10 mg/mL; when the GO water dispersion is used, calculating the mass of GO in the water dispersion according to the concentration proportion, and calculating the water in the corresponding water dispersion into the total amount of water used for 3D printing of concrete.

The specific type of the water reducing agent is not particularly limited, and the products sold in the market can meet the use requirements for preparing the coastal special-shaped structure. In some embodiments, the water reducing agent is one or more of a polycarboxylic acid high-efficiency water reducing agent, an early-strength polycarboxylic acid water reducing agent, a naphthalene sodium sulfonate high-efficiency water reducing agent or a melamine resin high-efficiency water reducing agent.

Preferably, the coagulation regulator is one of anhydrous sodium sulfate, triethanolamine and a nanometer C-S-H crystal nucleus. The coastal special-shaped 3D printing concrete provided by the invention is beneficial to quick setting of concrete through additives such as a coagulation regulator and the like, and the realization of the quick setting function of nano recycled concrete can be effectively guaranteed.

The invention adopts steel fiber, the specific source of which is not limited, and the steel fiber material generally adopts production waste of steel processing industry. For the sake of purchase convenience and cost saving, in some embodiments of the present invention, the steel fiber is one or a combination of chopped steel fiber, sheared steel fiber, milled steel fiber, and melted and drawn steel fiber.

In some embodiments, the organic fiber is one or a combination of chopped polyvinyl alcohol fiber, polypropylene fiber and high-density polyethylene fiber.

Preferably, the mineral admixture is one or a combination of more of regenerated micro-powder, ground slag, fly ash, volcanic ash or silica fume. The source of the raw material such as the regenerated fine powder is not particularly limited in the present invention.

Preferably, the water is one including but not limited to distilled water, deionized water, tap water or electrolyzed water, and the skilled person can select it according to the construction situation.

In a second aspect of the invention, a processing technology of 3D printed concrete for a coastal special-shaped structure is provided, and the processing technology includes: and printing and molding the concrete dry mixed material by the 3D printing concrete raw material of the first aspect through a 3D printing technology.

Preferably, the concrete dry mixing preparation process comprises the following specific steps: preparing GO-PVA pre-polymer body fluid from PVA, GO and an oxidant by an in-situ polymerization intercalation method; uniformly mixing FA, a water reducing agent, a catalyst and the GO-PVAH prepolymer liquid to form GO-PVAH @ FA prepolymer liquid wrapped by FA; dispersing GO-PVAH @ FA in a solution containing a water reducing agent and a coagulation regulating agent to form GO-PVAH @ FA suspension;

And mechanically and uniformly mixing the compound cement, the reclaimed sand, the steel fiber, the organic fiber and the mineral admixture in a storage bin to form a dry mixed material of the nano reclaimed concrete.

Further preferably, the GO-PVAH @ FA suspension and the dry mixed material of the nano recycled concrete are quickly mixed in a 3D printing head, the printing specification (speed, flow and layer thickness) of a 3D mechanical arm is set, and the thin layers of the nano recycled concrete with different layer thicknesses are printed layer by layer, so that the coastal special-shaped structure is obtained.

In some embodiment modes with better effects, the processing technology for 3D printing concrete of the coastal special-shaped structure provided by the invention specifically comprises the following operations:

s1: dissolving the PVA in hot water to prepare a PVA aqueous solution; under the condition that the PVA oxidant exists, the GO powder or the water dispersion is mixed into a PVA aqueous solution, and a PVA prepolymer is intercalated in a GO lamellar structure by adopting an in-situ polymerization intercalation process to obtain GO-PVA prepolymer liquid;

s2: adding FA, part of the water reducing agent and the PVA catalyst into GO-PVA prepolymer liquid, further wrapping GO-PVA hydrogel (GO-PVAH) on the surface of FA particles by adopting a thermal ultrasonic process to obtain GO-PVAH @ FA, and sealing for later use;

s3: adding the GO-PVAH @ FA into an additive water solution formed by the rest water reducing agent and the coagulant, and stirring uniformly at a high speed to obtain a GO-PVAH @ FA suspension; meanwhile, mechanically and uniformly mixing the compound cement, the reclaimed sand, the steel fibers, the organic fibers and the mineral admixture in a storage bin to form a dry mixed material of the nano reclaimed concrete;

S4: determining coastal special-shaped structure models with different specifications and sizes and material parameters, determining the printing specification requirements (speed, flow and layer thickness) of a 3D machine arm, quickly mixing GO-PVAH @ FA suspension and a nano recycled concrete dry mixed material on a 3D printing head by adopting a method well known in the art, printing nano recycled concrete thin layers with different layer thicknesses layer by layer, and finally quickly manufacturing the coastal special-shaped structure.

In step S1, the PVA intercalation efficiency and GO dispersion effect in GO-PVA pre-polymerization fluid may be analyzed by combining an automatic titration method, a rotational viscometer, a UV-Vis spectrophotometry method, and a micro-topography method.

In step S2, GO-PVAH equilibrium swelling ratio, transmittance, structural crosslinking degree, micro-distribution morphology and density can be measured by combining with a freeze-drying method, a UV-Vis spectrophotometry, a TG-DSC integrated thermal analysis method and a micro-morphology method, respectively; and (3) measuring the overall density, water content and organic matter content, interface stripping resistance and wrapping layer thickness of GO-PVAH @ FA by combining an ethanol drainage method, a TG-DSC comprehensive thermal analysis method, a stripping strength method and a film thickness instrument method.

In step S4, the nano recycled concrete can be prepared by conventional preparation method of nano recycled concrete for 3D printing, which is well known to those skilled in the art, and the types and the mixing amounts of the corresponding water reducing agent and the coagulation adjusting agent can be optimized by using a nano recycled concrete rheometer (viscosity coefficient, shear stress, thixotropic ring, thixotropic area), a full-automatic concrete setting time and consistency tester (setting time, consistency, rheological property over time), and the like. The performance characterization of the nano recycled concrete can be carried out by combining the test method of the large-scale printability and the marine durability (freeze-thaw resistance, chloride ion corrosion resistance and sulfate corrosion resistance) of the nano recycled concrete, which is well known by the technical personnel in the field. The electrochemical parameters of the steel fiber, such as corrosion potential, polarization resistance, corrosion current density, electrochemical impedance spectrum and the like, can be developed by combining the electrochemical performance characterization method of the nano recycled concrete containing the steel fiber, which is well known to the skilled person. And (3) characterizing the performance parameters of interlayer bonding tension, interlayer shearing force and the like of the nano recycled concrete thin layers with different layer thicknesses by adopting a method known in the field according to the printing specification requirements (speed, flow and layer thickness) of the 3D mechanical arm. And the construction quality of the nano recycled concrete with different layers and the interlayer bonding force deterioration condition under the actions of freeze-thaw cycle, ion erosion and sulfate corrosion can be evaluated by methods such as ultrasonic echo or radar wave nondestructive detection familiar to the technicians in the field.

Preferably, the coastal special-shaped structure comprises but is not limited to a well cover, a rainwater grate, an underground pipe gallery, an egg-shaped water tank, a subway segment, a honeycomb beam, a superposed beam/plate and the like.

In order to make the technical solution of the present invention more clearly understood by those skilled in the art, the technical solution of the present invention will be described in detail below with reference to specific examples, wherein the raw materials described in the following examples are all commercially available products.

Example 1

In the embodiment, a 3D printed concrete for a coastal special-shaped structure is provided, and the 3D printed concrete for the coastal special-shaped structure comprises the following components: compounding cement, reclaimed sand, Fly Ash (FA), polyvinyl alcohol (PVA), Graphene Oxide (GO), steel fiber, organic fiber, a water reducing agent, a coagulation regulator, a mineral admixture and water; the mass ratio of the components is 1: 1: 0.05: 0.005: 0.0002: 0.01: 0.005: (0.005-0.01): 0.005: 0.01: 0.3.

the compound cement comprises the following components: the High Belite Sulphoaluminate Cement (HBSC), the silicate cement and the gypsum are prepared from the following components in a mass ratio of 1: 0.65: 0.1; the quick-setting early strength characteristic of the compound cement and the ball lubrication characteristic of FA are beneficial to realizing the printable and constructable functions of the corresponding nano recycled concrete.

The mass ratio of coarse sand, medium sand, fine sand and superfine sand in the reclaimed sand is 1: 1.1: 1: 1.

the FA is grade I FA with loss on ignition less than or equal to 5% specified in GB/T1596-2017 standard.

The PVA is a PVA aqueous solution with the average polymerization degree of 500-600 and the alcoholysis degree of 88%; the GO is dispersed in a PVA aqueous solution to form a stable GO-PVA pre-polymer body fluid.

The PVA oxidant and the PVA catalyst are sodium periodate and concentrated hydrochloric acid respectively.

The single layer rate of GO is more than or equal to 90%, and the oxygen content is 40%.

The water reducing agent is a polycarboxylic acid high-efficiency water reducing agent.

The coagulation regulator is anhydrous sodium sulfate.

The steel fiber is a cut steel fiber.

The organic fiber is high-density polyethylene fiber.

The mineral admixture is prepared by mixing regenerated micro powder and ground slag in a mass ratio of 1: 1.

The water is tap water.

Example 2

In the embodiment, a 3D printed concrete for a coastal special-shaped structure is provided, and the 3D printed concrete for the coastal special-shaped structure comprises the following components: compounding cement, reclaimed sand, Fly Ash (FA), polyvinyl alcohol (PVA), Graphene Oxide (GO), steel fiber, organic fiber, a water reducing agent, a coagulation regulator, a mineral admixture and water; the mass ratio of the components is 1: 2: 0.2: 0.05: 0.002: 0.05: 0.02: 0.01: 0.01: 0.05: 0.5.

The compound cement comprises the following components: the High Belite Sulphoaluminate Cement (HBSC), the silicate cement and the gypsum are prepared from the following components in a mass ratio of 1: 1.25: 0.15.

the mass ratio of coarse sand, medium sand, fine sand and superfine sand in the reclaimed sand is 1: 2.0: 1.5: 1.5.

The PVA oxidant and the PVA catalyst are respectively potassium permanganate and dilute sulfuric acid.

The single layer rate of GO is more than or equal to 90%, and the oxygen content is 35%.

The water reducing agent is an early-strength polycarboxylic acid water reducing agent.

The pour point regulator is triethanolamine.

The steel fiber is a shear steel fiber and a milling steel fiber in a mass ratio of 0.5: 1 and mixing.

The organic fiber is polypropylene fiber.

The mineral admixture is fly ash.

The water is deionized water.

Example 3

In the embodiment, a processing technology for 3D printing concrete for a coastal special-shaped structure is provided, which specifically comprises the following steps:

s1: dissolving 0.25kg of PVA in 5L of hot water at the temperature of 70 ℃ to prepare a PVA water solution with the concentration of 5%, the average polymerization degree of 500-600 and the alcoholysis degree of 88%; under the condition of containing 0.02kg of sodium periodate (PVA oxidant), 0.025kg of GO powder is mixed into the PVA aqueous solution, and a GO-PVA prepolymer is intercalated in a GO lamellar structure by adopting an in-situ polymerization intercalation process to obtain GO-PVA prepolymer liquid;

S2: adding 1.0kg of FA, 0.1kg of polycarboxylic acid high-efficiency water reducing agent and 0.01kg of concentrated hydrochloric acid (PVA catalyst) into the GO-PVA pre-polymerization body fluid, further adopting an oil bath pot thermal ultrasonic dispersion process (oil temperature 100 ℃, frequency 10kHz, power 50W and ultrasonic time 30min), wrapping GO-PVA hydrogel (GO-PVAH) on the surface of FA particles to obtain GO-PVAH @ FA, and sealing for later use;

s3: adding the GO-PVAH @ FA into an additive aqueous solution formed by the residual 0.15kg of PCA-I type polycarboxylic acid high-efficiency water reducing agent (purchased from Jiangsu Subo New Material Co., Ltd.) and 0.3kg of anhydrous sodium sulfate (sold in the market), and stirring at a high speed to obtain GO-PVAH @ FA suspension; at the same time, 20kg of compound cement (composed of 10kg of 525 type HBSC, 9.5kg of P.O-52.5 type portland cement and 0.5kg of gypsum) and 40kg of class II granite reclaimed sand (obtained by crushing and particle shaping construction wastes removed from concrete structures in 28-year ages of C40 in Qingdao local areas), wherein the average apparent density of the mixture is 2860kg/m³) (consisting of 8kg coarse sand, 12kg medium sand, 10kg fine sand and 10kg ultra fine sand), 0.5kg ground slag powder (taken from the surface)Apparent density is 2930kg/m³The steel blast furnace heavy slag and ball milling), and adding 1.0kg/m³The shear type steel fiber (length of 3-15mm, diameter of 0.12-0.25mm, tensile strength not less than 2850MPa, produced by Jinhentong engineering materials Co., Ltd., Laiwu city) is 0.5kg/m ³Polyvinyl alcohol fibers (linear density 1.9 g/cm)³The dry breaking strength is more than or equal to 11.5MPa, the dry breaking elongation is more than or equal to 4.0-9.0%, the initial modulus is more than or equal to 280MPa, the length is 6mm, the equivalent diameter is less than or equal to 14 mu m, and the material is produced by Shandong calamus source new material technology Co., Ltd.), and is mechanically mixed in a material bin of an HC-3DPRT type concrete (mortar) 3D printing system (produced by Jian Hua Zheng (Hangzhou) technology Co., Ltd.), so as to form a corresponding nano recycled concrete dry mixed material;

s4: adding the GO-PVAH @ FA suspension and the residual distilled water calculated according to the water-cement ratio of 0.45 into the corresponding nano recycled concrete dry mixed material for 3D printing, and mechanically mixing the mixture in a storage bin of an HC-3DPRT type concrete (mortar) 3D printing system to prepare nano recycled concrete slurry for 3D printing.

Determining the specification of a printing head (nozzle equivalent diameter is 2.5cm) of a concrete (mortar) 3D printing system, wherein the plane printing speed is 5cm/s, the vertical lifting speed is 1.5cm/s, and the layer thickness is 2cm, printing the prepared nano recycled concrete mixture layer by layer to form a coastal rainwater grate structure by combining with rainwater grate structure parameters (300mm multiplied by 450mm multiplied by 60mm), and evaluating the rapid manufacturing, interlayer bonding and ocean durability of the coastal rainwater grate structure by a system.

In step S1, the intercalation efficiency and the dispersing effect of the PVA in the GO-PVA pre-polymer fluid are shown in fig. 1. In step S2, the swelling ratio and the wrapping layer thickness of GO-PVAH @ FA are respectively 30% and 65 μm; in step S4, the nano recycled concrete for 3D printing of the rain grate structure is rapidly manufactured, and interlayer bonding and ocean durability properties are shown in table 1.

The attached drawing 1 shows a GO-PVA polymerization intercalation and GO-PVAH @ FA cladding structure schematic diagram, the GO-PVA hydrogel layer is cladded on the surface of FA particles, and a GO lamellar structure is effectively intercalated by a PVA polymer to form a micro-capacitor positive and negative double electric layers, so that the marine corrosion resistance of the nano recycled concrete is effectively improved.

Example 4

The preparation process of the nano recycled concrete for 3D printing of the embodiment comprises the following specific steps:

s1: dissolving 0.5kg of PVA in 5L of hot water at the temperature of 80 ℃ to prepare a PVA water solution with the concentration of 10%, the average polymerization degree of 500-600 and the alcoholysis degree of 88%; under the condition of containing 0.015kg of potassium permanganate (PVA oxidant), mixing 10mg/mL of 2L of GO water dispersion into the PVA aqueous solution, and intercalating a PVA prepolymer in a GO lamellar structure by adopting an in-situ polymerization intercalation process to obtain GO-PVA prepolymer body fluid;

s2: 1.5kg of FA, 0.2kg

Adding a 510 type early strength polycarboxylic acid water reducer (purchased from Jiangsu Subo new materials Co., Ltd.) and 0.01kg of dilute sulfuric acid (PVA catalyst) into the GO-PVA pre-polymerization body fluid, further adopting an oil bath kettle thermal ultrasonic dispersion process (oil temperature 120 ℃, frequency 20kHz, power 50W and ultrasonic time 45min), wrapping GO-PVA hydrogel (GO-PVAH) on the surface of the FA particles, obtaining GO-PVAH @ FA, and sealing for later use;

S3: the GO-PVAH @ FA mentioned above was added to the remaining 0.1kg

Stirring uniformly at high speed in an additive water solution formed by a 510 type early strength polycarboxylic acid water reducing agent and 0.25kg of citric acid to obtain GO-PVAH @ FA suspension; at the same time, 25kg of compounded cement (consisting of 12kg of 525 type HBSC, 12kg of P.O 52.5.5 portland cement and 1kg of gypsum), 35kg of group II reclaimed sand (taken from the sand with apparent density of 3160 kg/m)³The chemical composition of the steel slag tailing sand is 35-38% of CaO and Fe₂O₃＝20～24％，SiO₂＝18～21％，Al₂O₃5-8% of MgO (5-7%) (consisting of 8kg of coarse sand, 12kg of medium sand, 8kg of fine sand and 7kg of superfine sand), 1kg of fly ash (produced by grade I, Qingdao tetragonal power plant), and 0.8kg/m of fly ash (produced by grade I, Qingdao tetragonal power plant) are added³The milled steel fiber (10-60 mm in length, 0.2-0.6mm in diameter, not less than 850MPa in tensile strength, available from Jinhentong engineering materials Co., Ltd., Laiwu, Ltd.) is 0.6kg/m³Polypropylene fibers (linear density 0.91)g/cm³The tensile strength is more than or equal to 450MPa, the ultimate elongation is more than or equal to 10%, the elastic modulus is more than or equal to 3500MPa, the length is 12mm, the equivalent diameter is less than or equal to 100 mu m, and the dry mixed material of the calamus source new material is produced by Shandong province scientific and technological Limited company) is formed by mechanical mixing;

s4: adding the GO-PVAH @ FA suspension and the residual deionized water calculated according to the water-cement ratio of 0.42 into the corresponding nano recycled concrete dry mixed material for 3D printing, and mechanically mixing the mixture in a storage bin of an HC-3DPRT type concrete (mortar) 3D printing system to prepare nano recycled concrete slurry for 3D printing.

Determining the specification of a printing head (the equivalent diameter of a nozzle is 3cm) of a concrete (mortar) 3D printing system, the plane printing speed is 6cm/s, the vertical lifting speed is 2cm/s, the layer thickness is 3cm, printing the prepared nano recycled concrete mixture layer by layer to form a coastal manhole cover structure by combining with the structural parameters (phi 600mm multiplied by 50mm) of the coastal manhole cover, and evaluating the rapid manufacturing, interlayer bonding and ocean durability of the system.

The swelling ratio and the wrapping thickness of GO-PVAH @ FA in the step S2 are respectively 40% and 50 μm. In step S4, the rapid manufacturing, interlayer bonding, and marine durability of the nano recycled concrete for 3D printing of the round manhole cover structure are also shown in table 1.

Example 5

s1: dissolving 0.3kg of PVA in 5L of hot water at 65 ℃ to prepare a PVA aqueous solution with the concentration of 6%, the average polymerization degree of 500-600 and the alcoholysis degree of 88%; under the condition of containing 0.02kg of potassium chlorate (PVA oxidant), 5L of GO water dispersion with the concentration of 4mg/mL is mixed into the PVA water solution, and a PVA prepolymer is intercalated in a GO lamellar structure by adopting an in-situ polymerization intercalation process to obtain GO-PVA prepolymer body fluid;

S2: adding 1.2kg of FA, 0.15kg of SBTJM-9 type polycarboxylic acid and melamine resin combined high-efficiency water reducing agent (purchased from Jiangsu Subo New Material Co., Ltd.) and 0.01kg of boric acid (PVA catalyst) into the GO-PVA pre-polymerization body fluid, further adopting an oil bath pan thermal ultrasonic dispersion process (oil temperature 100 ℃, frequency 20kHz, power 50W and ultrasonic time 60min), wrapping GO-PVA hydrogel (GO-PVAH) on the surface of FA particles to obtain GO-PVAH @ FA, wherein the swelling rate and the wrapping layer thickness are respectively 50% and 100 mu m, and sealing for later use;

s3: adding the GO-PVAH @ FA into an additive aqueous solution formed by adding the residual 0.15kg of SBTJM-9 type polycarboxylic acids and melamine resin combined high-efficiency water reducing agent and 0.3kg of tartaric acid, and stirring at a high speed to obtain GO-PVAH @ FA suspension; at the same time, 25kg of compound cement (composed of 12kg of 625 type HBSC, 12kg of P.I 42.5 portland cement and 1kg of gypsum) and 40kg of gold tailings II reclaimed sand (with the apparent density of 2670 kg/m)³With SiO₂、Al₂O₃Gold tailings of Laizhou mining Co., Ltd, crushed, granulated and formed) (consisting of 10kg of coarse sand, 10kg of medium sand, 10kg of fine sand and 10kg of ultra-fine sand), 1kg of volcanic ash (100 mesh, commercially available) and 1.0kg/m added³The melt-draw type steel fiber (13 mm in length, 0.3mm in diameter, 850MPa in tensile strength, 210GPa in elastic modulus, Baoding, Xinhuo steel fiber manufacturing Co., Ltd.), 0.5kg/m ³High density polyethylene fiber (density 0.97 g/cm)³The dry mixed material is prepared by mechanically mixing the components in a bin of an HC-3DPRT type concrete (mortar) 3D printing system (produced by Soviet technologies, Inc. of Jian Hua Huan, China) to form a corresponding nano regenerated concrete dry mixed material, wherein the tensile strength is 2.8-4N/tex, the elastic modulus is 91-140N/tex, the elongation is 3.5-3.7%, and the product is produced by Soviet special line and tape, Inc. of Dongguan;

s4: adding the GO-PVAH @ FA suspension and the residual electrolyzed water calculated according to the water-cement ratio of 0.35 into the corresponding nano recycled concrete dry mixed material for 3D printing, and mechanically mixing the mixture uniformly in a storage bin of an HC-3DPRT type industrial grade concrete (mortar) 3D printing system to prepare nano recycled concrete slurry for 3D printing.

Determining the specification of a printing head (nozzle equivalent diameter is 5cm) of an industrial-grade concrete (mortar) 3D printing system, wherein the plane printing speed is 4cm/s, the vertical lifting speed is 1.2cm/s, and the layer thickness is 1cm, printing the prepared nano recycled concrete mixture layer by layer to form an oval water tank structure by combining the structural parameters (1500mm multiplied by 450mm multiplied by 300mm) of the oval water tank, and evaluating the rapid manufacturing, interlayer bonding and ocean durability performance of the nano recycled concrete mixture by the system.

The GO-PVAH @ FA swelling ratio and the wrapping layer thickness in the step S2 are respectively 40% and 50 μm. In step S4, the rapid manufacturing, interlayer bonding, and ocean durability of the 3D printing nano recycled concrete with the oval water tank structure are also shown in table 1.

Example 6

The preparation method of the embodiment is the same as that of the embodiment 3, except that 20kg of the compound cement in the S3 step consists of two parts, namely 10kg of 525 type HBSC and 10kg of P.O 52.5.5 Portland cement, gypsum is not contained, and the corresponding mineral admixture is 0 kg.

In step S2, the swelling ratio and the wrapping layer thickness of GO-PVAH @ FA are respectively 30% and 65 μm. In step S4, the relevant properties of the nano recycled concrete for 3D printing are shown in table 1.

Table 1 comparative results of performance tests of nano recycled concrete for 3D printing in examples 3 to 6

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. The 3D printing concrete for the coastal special-shaped structure is characterized by comprising the following raw materials in parts by weight: 1 part of compound cement, 1-2 parts of reclaimed sand, 0.05-0.2 part of fly ash, 0.005-0.05 part of polyvinyl alcohol, 0.0002-0.002 part of graphene oxide, 0.01-0.05 part of steel fiber, 0.005-0.02 part of organic fiber, 0.005-0.01 part of water reducing agent, 0.005-0.01 part of pour regulator, 0-0.05 part of mineral admixture and 0.3-0.5 part of water; the PVA also has an oxidizing agent and a catalyst therein.

2. The 3D printed concrete for the coastal profiled structures as claimed in claim 1, wherein the compound cement is prepared from high belite sulphoaluminate cement, portland cement, gypsum in a weight ratio of 1: (0.65-1.25): (0-0.15) by weight.

3. The 3D printed concrete for the coastal profiled structures as claimed in claim 1, wherein the reclaimed sand comprises coarse sand, medium sand, fine sand and ultra-fine sand; wherein the medium sand rate is 27% -33%;

preferably, the coarse sand is coarse sand with fineness modulus of 3.7-3.1 and average particle size of more than 0.5 mm;

preferably, the medium sand is medium sand with fineness modulus of 3.0-2.3 and average grain diameter of 0.5-0.35 mm;

preferably, the fine sand is fine sand with fineness modulus of 2.2-1.6 and average grain diameter of 0.35mm-0.25 mm;

preferably, the superfine sand is the superfine sand with the fineness modulus of 1.5-0.7 and the average grain diameter of less than 0.25 mm;

preferably, the mass ratio of the coarse sand to the medium sand to the fine sand to the superfine sand is 1: (1.1-2.0): (1-1.5): (1-1.5).

4. The 3D printing concrete for the coastal profiled structures as recited in claim 1, wherein the FA is grade I FA with loss on ignition less than or equal to 5% specified in GB/T1596-2017 standard;

Or the PVA is a PVA water solution with the average polymerization degree of 500-600 and the alcoholysis degree of 88%;

or the PVA oxidant and the PVA catalyst are respectively one of sodium periodate, potassium permanganate or potassium chlorate, concentrated hydrochloric acid, dilute sulfuric acid, dilute nitric acid or boric acid;

or the GO is GO powder with a single-layer rate of more than or equal to 90% and an oxygen content of 35-45% or an aqueous dispersion with a concentration of 0.05-10 mg/mL.

5. The 3D printing concrete for the coastal deformed structure as claimed in claim 1, wherein the water reducing agent is one or a combination of a plurality of polycarboxylic acid high-efficiency water reducing agents, early-strength polycarboxylic acid water reducing agents, naphthalene sodium sulfonate high-efficiency water reducing agents or melamine resin high-efficiency water reducing agents;

or the coagulation regulator is one of anhydrous sodium sulfate, triethanolamine and nanometer C-S-H crystal nucleus.

6. The 3D printed concrete for the coastal profile structure as claimed in claim 1, wherein the steel fiber is one or a combination of several of a cut steel fiber, a sheared steel fiber, a milled steel fiber and a melted and drawn steel fiber;

or the organic fiber is one or a combination of a plurality of short-cut polyvinyl alcohol fiber, polypropylene fiber and high-density polyethylene fiber.

7. The 3D printed concrete for the coastal profiled structures as recited in claim 1, wherein the mineral admixture is one or a combination of recycled micro powder, ground slag, fly ash, volcanic ash or silica fume;

alternatively, the water is one including, but not limited to, distilled water, deionized water, tap water, or electrolyzed water.

8. The processing technology for 3D printing concrete of the coastal special-shaped structure is characterized by comprising the following steps: 3D printing the concrete material according to any one of claims 1 to 7, and printing and forming the concrete dry mixture by a 3D printing technology.

9. The processing technology of the 3D printed concrete with the coastal special-shaped structure as claimed in claim 8, wherein the concrete dry mixing material preparation technology comprises the following concrete steps: preparing GO-PVA pre-polymer body fluid from PVA, GO and an oxidant by an in-situ polymerization intercalation method; uniformly mixing FA, a water reducing agent, a catalyst and the GO-PVAH prepolymer liquid to form GO-PVAH @ FA prepolymer liquid wrapped by FA; dispersing GO-PVAH @ FA in a solution containing a water reducing agent and a coagulation regulating agent to form GO-PVAH @ FA suspension; mechanically and uniformly mixing compound cement, reclaimed sand, steel fiber, organic fiber and mineral admixture in a storage bin to form a nano reclaimed concrete dry mixed material;

Preferably, the GO-PVAH @ FA suspension and the dry mixed material of the nano recycled concrete are quickly mixed in a 3D printing head, the printing specification of a 3D mechanical arm is set, and the thin layers of the nano recycled concrete with different layer thicknesses are printed layer by layer, so that the coastal special-shaped structure is obtained.

10. Use of the 3D printed concrete for a coastal profiled structure as claimed in any one of claims 1 to 7 for the preparation of a coastal profiled structure;