CN113307597A

CN113307597A - Nano recycled concrete, processing technology and application

Info

Publication number: CN113307597A
Application number: CN202110779748.6A
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: 2021-07-09
Publication date: 2021-08-27
Anticipated expiration: 2041-07-09
Also published as: WO2022007063A1; AU2020457381A1; CN113307597B; AU2020457381B2; JP2022542640A; JP7362083B2; CN111848081A

Abstract

The invention particularly relates to nano recycled concrete, a processing technology and application. The existing nano recycled concrete also has the following defects: the conventional marine anticorrosion technology is not ideal in anticorrosion effect when applied to a 3D printed coastal assembly structure, and in addition, interface bonding and thixotropy between layers of conventional 3D printing materials are not enough. The invention provides nano recycled concrete which is prepared from the raw materials of compound cement, recycled sand, fly ash, polyvinyl alcohol, graphene oxide, steel fiber, organic fiber, a water reducing agent, a coagulation regulator, 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 assembly structure engineering and has good application prospect.

Description

Nano recycled concrete, processing technology and application

Technical Field

The invention belongs to the technical field of concrete 3D printing, and particularly relates to nano recycled concrete, a processing technology of the nano recycled concrete and application of the nano recycled concrete in preparation of a coastal assembly 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 concrete structure engineering such as offshore buildings, bridge tunnels, wind energy nuclear power stations, oil drilling platforms, harbor wharfs and the like. The special-shaped coastal concrete structure such as 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 can be rapidly manufactured based on the 3D printing technology, and further the special-shaped coastal concrete structure is 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, as the concrete for the coastal assembly 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, in particular for profiled structures, the inventors found that the following problems existed:

(1) the curved surface of the coastal assembly 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 are not applicable to the coastal assembly structure with the continuous printing interface layer, or the application effect is poor.

(2) When the conventional 3D printing concrete material is used for printing the coastal assembly 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 assembly 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 technology, the invention aims to provide the optimized nano recycled concrete which can be applied to 3D printing, and the special-shaped structure obtained by printing has better marine anticorrosion effect and interlayer interface bonding and thixotropic property.

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

the invention provides nano recycled concrete, which comprises Fly Ash (FA), polyvinyl alcohol (PVA) and Graphene Oxide (GO) and is characterized in that GO-PVAH FA hydrogel is formed by the Fly Ash (FA), the polyvinyl alcohol (PVA) and the Graphene Oxide (GO).

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 assembly structure are obviously improved.

In a second aspect of the present invention, there is provided a processing method of the nano recycled concrete of the first aspect, the processing method comprising: 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 a GO-PVAH @ FA suspension.

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

In a third aspect of the invention, the application of the nano recycled concrete of the first aspect in preparing a coastal assembly structure is provided.

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

(1) by adopting the nano recycled concrete and the processing technology, the coastal assembly structure can be quickly manufactured, and the ocean durability of the coastal assembly 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 nano recycled 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 3D printed concrete to have good cohesive water retention property, and enable adjacent 3D printed 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 assembly 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 to avoid the formation of a steel fiber corrosion micro-battery in a 3D printing coastal structure, the reinforcement 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 a hardened body of nano recycled concrete 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 flow chart of the nano recycled concrete and the processing technology described in example 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 printed nano recycled concrete, a processing technology and application thereof in the rapid manufacturing of a coastal assembly 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 assembly 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 fast manufacturing of coastal assembly structures.

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 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.

Preferably, the nano recycled concrete also comprises compound cement, and 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 nano recycled concrete also comprises recycled sand, wherein the recycled 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.

In one embodiment with a good effect, the nano recycled concrete is prepared from 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 nanometer recycled concrete prepared from 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 concrete mixed structure with different specifications can be obtained by printing. In addition, the printed coastal assembly structure has good marine durability.

The specific type of the water reducing agent is not particularly limited in the invention, and all products sold in the market can meet the use requirements for preparing the coastal assembly 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.

In an embodiment with a better effect, the water reducing agent is replaced by a retarding superplasticizer, so that the slump loss rate can be effectively reduced.

In another embodiment with a better effect, the nano concrete also contains the EVA redispersible polymer latex, so that the fluidity of concrete slurry can be effectively improved.

Further, the coagulation regulator is one of anhydrous sodium sulfate, triethanolamine and a nanometer C-S-H crystal nucleus. The coastal assembly 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.

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

Further, the water is one of distilled water, deionized water, tap water or electrolyzed water, and the skilled person can select the water according to the construction situation.

Further, 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 that the PVA prepolymer is intercalated in the GO lamellar structure by an in-situ polymerization intercalation process.

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 nano recycled concrete is obtained.

In some embodiment modes with better effects, the processing technology of the nano recycled concrete 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, the compound cement, the reclaimed sand, the steel fiber, the organic fiber and the mineral admixture are mechanically and uniformly mixed in a storage bin to form a dry mixed material of the nano reclaimed concrete.

S4: determining coastal assembly 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 the 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 assembly 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 assembly 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 this embodiment, a nano recycled concrete is provided, which includes 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 this embodiment, a nano recycled concrete is provided, which includes 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 this embodiment, a processing technology of nano recycled concrete is provided, which specifically includes 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 the in-situ polymerization intercalation process is adopted to intercalate the PVA prepolymer in the GO lamellar structure 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 superfine sand), 0.5kg ground slag powder (from an apparent density of 2930 kg/m)³The 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/m³Polyvinyl 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 the 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 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 a high speed in an additive water solution formed by a 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/cm)³The 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 nano regenerative concrete is produced by Shandong calamus source new material science and technology Limited company).

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 the 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 1.2kg 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/m³High density polyethylene fiber (density 0.97 g/cm)³Tensile strength of 2.8-4N/tex, elastic modulus of 91-140N/tex,3.5-3.7% elongation, available from soviet special tape company, Dongguan), and mechanically mixing in a bin of an HC-3DPRT type concrete (mortar) 3D printing system (available from Jianhua Hua survey (Hangzhou) science and technology company, so as to form a corresponding nano recycled concrete dry mixed material.

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

As can be seen from the above Table 1, after the GO-PVAH @ FA hydrogel is added into the nano concrete in the embodiments 3-6, the water-sinking rate and the thixotropic index are obviously improved compared with the concrete without the GO-PVAH @ FA hydrogel, the concrete setting speed is increased, and the concrete strength is comprehensively improved.

Example 7

In this example, another nano-recycled concrete was provided, which is different from example 3 in that the slump loss rate with time of 30min of the nano-recycled concrete slurry obtained by changing 0.15kg of the water reducing agent to 0.15kg of the set-retarding superplasticizer was reduced from 72.6% to 18.5%.

Example 8

In this example, another nano recycled concrete was provided, which is different from example 3 in that: by adding 1.5kg of EVA redispersible polymer latex, the fluidity of the nano recycled concrete slurry is increased to 220mm from the original 205mm, the freeze-thaw durability is increased to F250 grade from the original F150, the surface is changed from the hydrophilic characteristic to the hydrophobic characteristic, and the corresponding surface contact angle is rapidly increased to 97.4 degrees from the original 32.3 degrees.

Comparative example 1

In the research process of the invention, the nano recycled concrete is prepared by adopting single-formula cement, and HBSC or Portland cement is added into the concrete. However, the research shows that the single use of HBSC has the problems of incompatibility with the admixture and too fast slump loss; the problem of volume shrinkage and cracking of a nano recycled concrete hardened body can be caused by singly using the portland cement; the gypsum used alone has the problems of low strength and poor water resistance of the nano recycled concrete hardened body.

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 nano recycled concrete is characterized by comprising fly ash, polyvinyl alcohol and graphene oxide; the fly ash, the polyvinyl alcohol and the graphene oxide form GO-PVAH @ FA hydrogel.

2. The nano-recycled concrete as set forth in claim 1, wherein the FA is class I FA with loss on ignition of less than or equal to 5% as 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%; dispersing GO in a PVA aqueous solution to form a stable GO-PVA pre-polymer body fluid;

or 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.

3. The nano recycled concrete of claim 1, wherein the nano recycled concrete further comprises a compound cement, and the compound cement is prepared from high belite sulphoaluminate cement, portland cement and gypsum in a proportion of 1: (0.65-1.25): (0-0.15) by weight;

or the nano recycled concrete also comprises recycled sand, wherein the recycled sand comprises coarse sand, medium sand, fine sand and ultrafine 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 nano recycled concrete of claim 1, wherein the nano recycled concrete is prepared from 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 comprises an oxidant and a catalyst;

preferably, the water reducing agent is one or an optimized combination of 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;

preferably, the steel fiber is one or a combination of several of cut steel fiber, shearing steel fiber, milling steel fiber and melt-drawing steel fiber;

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

5. The nano recycled concrete of claim 1, wherein the mineral admixture is one or more of recycled micro powder, ground slag, fly ash, volcanic ash or silica fume;

preferably, the water is one of distilled water, deionized water, tap water or electrolyzed water;

preferably, 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, and the PVA prepolymer is intercalated in the GO lamellar structure by an in-situ polymerization intercalation process.

6. The process for the preparation of nano-recycled concrete according to any of claims 1 to 5, wherein said process comprises: 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;

7. The process for preparing nano recycled concrete according to claim 6, wherein the GO-PVAH @ FA suspension and the nano recycled concrete dry mixture are rapidly mixed in a 3D printing head, the printing specification of a 3D mechanical arm is set, and the nano recycled concrete thin layers with different layer thicknesses are printed layer by layer, so that the nano recycled concrete is obtained.

8. The processing technique of nano recycled concrete as claimed in claim 7, characterized in that the processing technique of nano recycled concrete is specifically operated as follows:

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 assembly structure models with different specification sizes and material parameters, determining the printing specification requirements of a 3D (three-dimensional) robot arm, quickly mixing GO-PVAH @ FA suspension and a nano recycled concrete dry mixed material at a 3D printing head by adopting a method well known in the field, printing nano recycled concrete thin layers with different layer thicknesses layer by layer, and finally quickly manufacturing a coastal assembly structure.

9. The process for producing nano recycled concrete according to claim 8, wherein:

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

or, 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 spectroscopic method, a TG-DSC integrated thermal analysis method and a micro-morphology method, respectively; respectively measuring the overall density, water content and organic matter content of GO-PVAH @ FA, interface peel resistance and wrapping layer thickness by combining an ethanol drainage method, a TG-DSC comprehensive thermal analysis method, a peel strength method and a film thickness instrument method;

alternatively, in step S4, the nano recycled concrete may 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 may be optimized by a nano recycled concrete rheometer, a full-automatic concrete setting time and consistency measuring instrument, and the like.

10. Use of the nano-recycled concrete of any one of claims 1 to 7 for the preparation of a coastal assembly structure;

preferably, the coastal assembly 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 and a superposed beam/plate.