A temperature-sensitive nano-porous carrier with improved workability and controllable release of water-reducing agent

Abstract

The present application relates to a kind of controllable release water reducing agent based on and easy to improve temperature sensitivity nanometer microporous carrier, the temperature sensitivity nanometer microporous carrier is by the following weight fraction of raw material component composition with total weight fraction 1000 parts: sodium silicate 280-320 parts, solvent 330-370 parts, gel hardener 80-100 parts, auxiliary 30-50 parts, auxiliary initiator 15-25 parts, heat-sensitive polymer 180-220 parts.The present application is by combining green chemistry and nanotechnology, introduce temperature sensitivity nanometer microporous carrier, to realize the controllable release of water reducing agent, to improve the workability of recycled coarse aggregate concrete.Nanometer microporous carrier special structure and functional group modification mode makes it can carry water reducing agent, by the controlled release of water reducing agent realizes the accurate adjustment to the fluidity and slump of concrete.At the same time, by regulating hydration heat release process to avoid concrete aggregation heat release, help to optimize the pore structure of cement paste, to improve the mechanical properties and frost resistance of recycled concrete.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology and relates to a controllable release water-reducing agent based on a temperature-sensitive nanoporous carrier with improved workability. Background Technology

[0002] With the acceleration of global urbanization and the rapid increase in infrastructure construction, a large amount of concrete is being used. This high demand for concrete production has led to a significant depletion of natural sand and gravel aggregates and increasingly prominent environmental problems. Recycled coarse aggregates, as a sustainable building material, have attracted widespread attention. Through sorting, crushing, and screening processes, construction and demolition waste (CDW) is reused and used to prepare new concrete. Therefore, recycled coarse aggregates offer a potential solution to alleviate the shortage of natural aggregates. However, the porous old mortar adhering to the surface of recycled coarse aggregates and the crushing process itself cause quality defects, leading to challenges in the fluidity, bondability, and water retention properties of recycled concrete.

[0003] Numerous improvement processes for recycled concrete have been proposed, among which the use of water-reducing agents is widely accepted. Currently, polycarboxylate-based water-reducing agents, as the third generation of new water-reducing agents, have advantages such as low dosage, strong dispersibility, high water reduction rate, and good slump retention, which help improve the workability of concrete. However, due to the special properties of recycled coarse aggregates, the improvement effect of ordinary polycarboxylate water-reducing agents is easily limited. Especially under long-distance transportation conditions, the workability of recycled concrete changes significantly over time, resulting in substantial loss of workability, which is detrimental to on-site construction. Although slow-release water-reducing agents have been developed, current products are mostly passively slow-released and lack active adjustment capabilities, resulting in poor adaptability to recycled concrete. Furthermore, ordinary polycarboxylate water-reducing agents often have negative environmental impacts, which does not conform to the concept of green environmental protection.

[0004] For example, Chinese patent CN201010119879.3 discloses a controlled-release polycarboxylate superplasticizer and its preparation method for suppressing the influence of aggregate mud content. It comprises 75-95 parts of polycarboxylate superplasticizer, 2-5 parts of retarder, and 5-25 parts of slow-release agent, wherein the slow-release agent is natural zeolite powder. Although natural zeolite powder has strong adsorption properties, its adsorption performance is affected by environmental factors (such as temperature and humidity), resulting in poor stability and making it difficult to meet the requirements of concrete construction. Furthermore, as a natural resource, the mining, processing, and transportation costs of natural zeolite powder are relatively high, hindering its large-scale application. Summary of the Invention

[0005] The purpose of this invention is to provide a controllable release water-reducing agent based on a temperature-sensitive nanoporous carrier with improved workability, so as to achieve controllable release of the water-reducing agent and thereby improve the workability of recycled coarse aggregate concrete.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] One of the technical solutions of the present invention provides a workability-improved temperature-sensitive nanoporous carrier, which is composed of the following raw material components in parts by weight, based on a total weight of 1000 parts: 280-320 parts sodium silicate, 330-370 parts solvent, 80-100 parts gel curing agent, 30-50 parts additives, 15-25 parts co-initiator, and 180-220 parts thermosensitive polymer.

[0008] Optionally, the proportions of each raw material are as follows:

[0009] Sodium silicate: 300 parts;

[0010] Solvent: 350 parts;

[0011] Gel hardener: 90 parts;

[0012] Additives: 40 parts;

[0013] Initiator: 20 parts;

[0014] Thermosensitive polymer: 200 parts.

[0015] Furthermore, the gel hardener is ammonium chloride;

[0016] The solvent is water;

[0017] The aforementioned additive is a silane coupling agent;

[0018] The co-initiator is one or a combination of ferrous ammonium sulfate or ferrous sulfate.

[0019] Furthermore, the heat-sensitive polymer is one or a combination of several of poly(N-isopropylacrylamide) (PNIPAM), poly(N,N-dimethylacrylamide) (PDMA), and polyvinyl formaldehyde (PVA), which can adjust the microporous structure of nano-silica, enabling the nanoporous carrier to continuously release water-reducing agent in stages. Specifically, in the first stage, the water-reducing agent wrapped around the outer layer of the nanocarrier is released. During concrete mixing, on the one hand, due to the humidity gradient and capillary suction, the water-reducing agent in the saturated nanocarrier migrates into the concrete; on the other hand, the water-reducing agent molecules are physically adsorbed onto the carrier, and at low temperatures, the molecular movement within the nanoporous carrier is relatively slow. When the hydration reaction begins, the released heat intensifies the movement of water-reducing agent molecules, thereby accelerating the escape of the water-reducing agent and its binding with cement particles and the mud particles on the surface of recycled aggregate. In the second stage, as the hydration reaction proceeds, the released heat increases rapidly. When the temperature rises above 25°C, the molecular movement inside the pore structure intensifies, and the water-reducing agent in the micropores of the nanocarrier is released. Poly(N-isopropylacrylamide) is used as an example. First, because the poly-N-isopropylacrylamide-silane polymer chains grafted onto the pore openings of the nano-silica particles extend and intertwine below 25°C, the water-reducing agent is locked within the pores. When the temperature exceeds 25°C, the polymer chains contract, thereby opening the pore openings. Due to diffusion, the water-reducing agent is released from the pores into the cement paste. In the third stage, the hydration reaction leads to an increase in pH, producing OH-... - Reaction with nano-silica to produce And further with dissolved Ca 2+ The reaction produces CSH gel, which means that the carrier gradually dissolves, thereby releasing the remaining water-reducing agent within the carrier until it is completely released.

[0020] The second technical solution of the present invention provides a method for preparing a workability-modified temperature-sensitive nanoporous carrier, comprising the following steps:

[0021] (A) Weigh out sodium silicate, dissolve it in a solvent, add additives, and disperse it evenly to form a sol;

[0022] (B) Add a thermosensitive polymer and a co-initiator to the sol, stir and mix thoroughly, then add a gel hardener. The addition of the gel hardener initiates gel formation, and the sol gradually thickens to obtain a colloidal gel. Allow the colloidal gel to stand and further solidify, then dry it to remove residual chemicals and generate a more stable microporous carrier, thus obtaining a temperature-sensitive nanoporous carrier.

[0023] Furthermore, additives can enhance the interaction between the nanoporous carrier and the water-reducing agent. These functional molecules can be introduced into the microporous carrier through surface modification to improve its compatibility and interaction with the water-reducing agent, effectively improving the temperature stability of the sol. This can further optimize the release behavior of the water-reducing agent and improve the workability of recycled concrete.

[0024] Furthermore, the reaction temperature for forming a colloidal gel after adding the gel hardener is 15-20℃, and the reaction time is 10-20 min;

[0025] Furthermore, the standing temperature is 0-10℃ and the standing time is 12-24h to ensure that the colloidal gel is fully cured and forms a stable microporous carrier;

[0026] Furthermore, the drying process is carried out in a cool, shaded environment to avoid exposing the temperature-sensitive nanoporous carrier to high temperatures. The drying temperature is 10-20°C, the relative humidity is 30%-40%, and the drying time is 24-72 hours.

[0027] Furthermore, the stirring speed was 1000 r / min, and the stirring time was 10 h.

[0028] The third technical solution of the present invention provides a controllable release water-reducing agent based on a workability-modified temperature-sensitive nanoporous carrier, comprising the following raw material components in parts by weight: 220-300 parts of polycarboxylate water-reducing agent, 150-210 parts of the temperature-sensitive nanoporous carrier as described above, 50-70 parts of dispersant, 60-80 parts of dispersing aid, 30-50 parts of functional modifier, 40-60 parts of stabilizer, 40-60 parts of controlled-release additive, 25-35 parts of rheology modifier, 15-25 parts of pH adjuster, and 450-570 parts of water.

[0029] Furthermore, the formulation of this water-reducing agent is as follows:

[0030] Polycarboxylate superplasticizer: 260 parts;

[0031] Temperature-sensitive nanoporous carriers: 180 parts;

[0032] Dispersant: 60 parts;

[0033] Dispersing agent: 70 parts;

[0034] Functional modifiers: 40 parts;

[0035] Stabilizer: 50 parts;

[0036] Controlled-release additive: 50 parts;

[0037] Rheology modifier: 30 parts;

[0038] pH adjuster: 20 parts;

[0039] Water: 510 portions.

[0040] Furthermore, the dispersant is sodium n-heptylbenzenesulfonate; the dispersing aid is polyvinyl alcohol; the functional modifier is hydroxymethyl cellulose; the stabilizer is propylene glycol; the controlled-release additive is citric acid; the rheology modifier is nano-diatomaceous earth; and the pH adjuster is sodium hydroxide.

[0041] Furthermore, nano-diatomaceous earth, a commercially available product, can thicken and improve the rheological properties of recycled concrete. With its large specific surface area and porous structure, nano-diatomaceous earth can form stable colloidal particles in concrete and undergo physical adsorption and coagulation with cement colloids, increasing the viscosity and consistency of the concrete. In addition, nano-diatomaceous earth can fill the voids in recycled coarse aggregate, increasing the aggregate's density and thus improving the mechanical and durability properties of the concrete.

[0042] Furthermore, sodium hydroxide is used to adjust the pH value of the reaction, adjusting the pH of the water-reducing agent to 12-13, so as to provide an alkaline environment for the hydration reaction of cement and protect the steel bars inside the concrete from corrosion.

[0043] The fourth technical solution of the present invention provides a method for preparing a controllable release water-reducing agent based on a workability-modified temperature-sensitive nanoporous carrier, comprising the following steps:

[0044] (1) The temperature-sensitive nanoporous carrier is mixed with water at 15°C and stirred evenly to form a basic carrier;

[0045] (2) Weigh out the controlled-release additive and disperse it in water, add the base carrier from step (1), and stir until uniform to obtain a carrier solution mixture.

[0046] (3) Weigh the rheology modifier and the functional modifier and disperse them in water to prepare a suspension. Then add the suspension to the carrier solution mixture one in step (2) and stir evenly to obtain the carrier solution mixture two.

[0047] (4) Continue to mix the polycarboxylate superplasticizer, dispersant, additives and stabilizer into the carrier solution mixture in step (3). Adjust the pH of the system to 12-13 using a pH adjuster and control the binding temperature of the carrier and superplasticizer to 28°C to obtain a temperature-sensitive nanoporous carrier with controllable release superplasticizer. Then store it in a brown clamp-mouth sample bottle and control the storage temperature to 10°C.

[0048] The fifth technical solution of the present invention provides a workability-improved recycled coarse aggregate concrete, comprising the following raw material components in parts by weight:

[0049] Cement: 360-450 parts;

[0050] Recycled coarse aggregate: 920-1050 parts;

[0051] River sand: 600-700 parts;

[0052] Fly ash: 60-180 parts;

[0053] The temperature-sensitive nanoporous carrier with controlled-release water-reducing agent as described above: 5-15 parts;

[0054] Expanding agent: 32-60 parts;

[0055] Water: 200-240 servings;

[0056] Biomass fiber: 60-90 parts.

[0057] Furthermore, the raw material formulation for recycled coarse aggregate concrete can be:

[0058] Cement: 380-430 parts;

[0059] Recycled coarse aggregate: 940-1020 parts;

[0060] River sand: 620-680 parts;

[0061] Fly ash: 80-180 parts;

[0062] Temperature-sensitive nanoporous carrier with controlled-release water-reducing agent: 6-14 parts;

[0063] Expanding agent: 40-56 parts;

[0064] Water: 205-235 parts;

[0065] Biomass fiber: 65-80 parts.

[0066] Furthermore, the raw material formulation for recycled coarse aggregate concrete can be:

[0067] Cement: 400-420 parts;

[0068] Recycled coarse aggregate: 960-1000 parts;

[0069] River sand: 640-660 parts;

[0070] Fly ash: 100-120 parts;

[0071] Temperature-sensitive nanoporous carrier with controlled-release water-reducing agent: 8-12 parts;

[0072] Expanding agent: 45-50 parts;

[0073] Water: 210-220 parts;

[0074] Biomass fiber: 65-75 parts.

[0075] Furthermore, the cement is PO 42.5 ordinary Portland cement, with a 28-day compressive strength of 46.2-53.2 MPa, and is produced by Shanghai Building Materials Group Cement Co., Ltd.

[0076] The recycled coarse aggregate is derived from C40 waste concrete and is prepared by Shanghai Conggu Renewable Resources Co., Ltd. through crushing, washing, screening, sorting, and drying. Its apparent density is 2562 kg / m³. 3 The crushing index was 16.8%;

[0077] The fly ash is Grade I fly ash with a loss on ignition of 2.38% and a sulfur trioxide content of 1.67%, produced by Shanghai Guangfa Fly Ash Co., Ltd.

[0078] The water in question is tap water supplied to the laboratory;

[0079] The biomass fiber mentioned is lignocellulose. The synergistic effect of lignocellulose and temperature-sensitive nanoporous carrier controlled-release water-reducing agent can improve the workability of recycled coarse aggregate concrete. The improvement mechanism is mainly in the following aspects: (1) Nanoporous silica acts as a carrier to adsorb water-reducing agent and releases it gradually through controlled release. Lignocellulose, as a porous bio-based material, also has a certain adsorption capacity and can further adsorb water-reducing agent. Such dual adsorption can prolong the release time of water-reducing agent in concrete, thereby maintaining the rheological properties of recycled concrete. (2) The reaction between lignocellulose and water-reducing agent enhances its bonding ability with concrete, thereby improving the viscosity and viscosity of concrete. This thickening effect helps prevent segregation and sedimentation of concrete, and makes it more plastic by improving the rheological properties of concrete, which is conducive to improving the uniformity and stability of recycled coarse aggregate concrete. (3) As a porous material, lignocellulose can optimize the pore space distribution morphology inside recycled coarse aggregate, increase the density of aggregate, and is conducive to improving the mechanical properties and durability of recycled coarse aggregate concrete. At the same time, the filling effect of lignocellulose can also optimize the pore structure of concrete, reduce the generation of cracks, and improve the impermeability of concrete.

[0080] Alternatively, the method for preparing recycled coarse aggregate concrete may include the following steps:

[0081] (1) Take samples of recycled coarse aggregate, cement and fly ash according to the weight in the proportion, and pour them into a high-power single-shaft mixer for the first mixing. The mixing speed is 45r / min and the mixing time is 4min to obtain the first mixture.

[0082] (2) Add water to the first mixture and stir for a second time at a speed of 45 r / min for 3 min to obtain the second mixture;

[0083] (3) Add the temperature-sensitive nanoporous carrier's controllable release water-reducing agent, expansion agent and biomass fiber to the second mixture for a third stirring. The stirring speed is 50 r / min and the stirring time is 3 min to obtain the fresh concrete mixture.

[0084] In the preparation of recycled concrete, the nanoporous carrier has a significant impact on the workability of the concrete. Firstly, the high specific surface area of ​​the nanoporous carrier promotes the adsorption of water-reducing agents, thereby improving their dispersibility and uniformity. Secondly, the unique porous structure of the carrier allows for controlled release of the water-reducing agent into the concrete under specific environmental conditions, controlling its release rate and thus achieving precise regulation of the concrete's fluidity and slump. Furthermore, surface modification by introducing functional groups into the carrier can further enhance the interaction between the carrier and the water-reducing agent, thereby improving the workability of the concrete.

[0085] Compared with the prior art, the present invention has the following advantages:

[0086] (1) The workability of recycled coarse aggregate concrete was significantly improved by introducing a temperature-sensitive nanoporous carrier with controlled-release water-reducing agent. The nanoporous carrier has a high specific surface area, allowing it to adsorb and store large amounts of water-reducing agent. During concrete preparation, the water-reducing agent is gradually released, improving the workability of the concrete and making it easier to construct and pour. Compared to traditional water-reducing agents, the temperature-sensitive nanoporous carrier with controlled-release water-reducing agent not only provides a lasting improvement in workability but also effectively reduces the amount of water-reducing agent used, lowering construction costs.

[0087] (2) By controlling the release of water-reducing agents, the workability of recycled concrete is improved, and the amount of water-reducing agent used is reduced. Controlled-release water-reducing agents are the core of the nanoporous carrier-controlled-release technology. Compared with traditional water-reducing agents, the release rate of controlled-release water-reducing agents in concrete can be adjusted according to specific needs. This technology ensures the continuous release of water-reducing agents, giving the concrete good fluidity and workability, and allowing for the regulation of concrete fluidity under specific conditions.

[0088] (3) Nanoporous carriers possess tunable pore structures and surface chemical properties, enabling them to be customized in recycled coarse aggregate concrete. By adjusting the pore structure and functional group modification methods of the carrier, the release of water-reducing agents can be controlled, thereby better adapting to the characteristics of different recycled coarse aggregates and the requirements of concrete. For recycled aggregates with different particle size ranges, such as recycled coarse aggregates and recycled fine aggregates, targeted optimization can be achieved by adjusting the characteristics of the carrier, further improving the workability of recycled concrete.

[0089] (4) During the mixing and curing of concrete, the temperature-sensitive nanoporous carrier releases water-reducing agent in stages. After all the agent has been released, the nanoporous carrier will adsorb free water in the system and reduce the degree of freeze-thaw damage to the concrete by automatically regulating the opening and closing of the micropores. During the freezing stage, the polymer chains in the carrier micropores expand and aggregate, and the pore size changes from nanoporous carrier micropores to molecular chain level. The pore size decreases, the capillary effect becomes significant, and free water in the concrete is further adsorbed, reducing the water content, improving the pore structure, and reducing the growth and expansion of ice crystals and stress concentration. During the dissolving stage, the micropores of the carrier open, releasing the adsorbed free water, increasing the water content of the concrete, and reducing the stress and temperature gradient caused by freeze-thaw.

[0090] (5) Cement releases a large amount of heat during hydration. When the internal temperature of concrete rises, moisture evaporates, and the decrease in relative humidity increases the risk of drying shrinkage, strength reduction, and cracking (temperature stress) in concrete, thereby reducing the performance of recycled concrete. The temperature-sensitive nanoporous carrier described in this invention, with its controllable release of water-reducing agent, can regulate the hydration heat release process. By changing the surface properties of cement particles, the contact area between cement and water is reduced, thereby slowing down the hydration reaction rate, preventing concrete from accumulating and releasing heat, and thus reducing the temperature rise caused by cement hydration heat release. Specifically, the mechanism of this temperature-sensitive nanoporous carrier's controllable release of water-reducing agent is as follows: First, in the initial mixing stage, the temperature-sensitive nanoporous carrier releases the outer layer of water-reducing agent; as the temperature gradually rises and exceeds 25°C, the polymer chains within the carrier's micropores shrink, and the micropores change from sealed to open, thereby further releasing the water-reducing agent; finally, as the hydration reaction proceeds, the carrier gradually dissolves, and the remaining water-reducing agent is completely released. The water-reducing agent adsorbs onto the cement surface to form a covering layer, preventing moisture from directly contacting the cement particles. This barrier effect slows down the rate at which water penetrates into the cement particles, thereby reducing the hydration reaction rate of the cement. Furthermore, the water-reducing agent can form a dispersed phase, hindering the affinity between cement particles and reducing particle agglomeration, thus slowing down the diffusion rate of hydration reactants. These mechanisms work together to effectively reduce the hydration reaction rate and hydration heat release rate of concrete, improving the mechanical properties and durability of recycled concrete.

[0091] (6) Improved environmental performance of recycled coarse aggregate concrete, promoting sustainable development in the building materials sector. The application of temperature-sensitive nanoporous carriers with controlled-release water-reducing agents further enhances the environmental performance of recycled coarse aggregate concrete. The effective use of water-reducing agents reduces the demand for raw materials, and the use of recycled coarse aggregates reduces the consumption of natural resources. In addition, nanoporous carriers can enhance the durability and crack resistance of recycled concrete through surface modification and the introduction of functional groups, extending the service life of concrete structures and further reducing environmental impact.

[0092] In summary, the application of temperature-sensitive nanoporous carrier-based controlled-release water-reducing agents in recycled coarse aggregate concrete has many advantages, including improved concrete fluidity and workability, reduced water-reducing agent usage, customized modification, and enhanced environmental performance, mechanical properties, and freeze-thaw resistance of concrete. This contributes to the sustainable development of the building materials industry and promotes the effective use of resources. Attached Figure Description

[0093] Figure 1 The mechanism of action of controlled-release water-reducing agents with added temperature-sensitive nanoporous carriers on workability improvement of recycled coarse aggregate concrete was demonstrated.

[0094] Figure 2 A schematic diagram showing the effect of adding a temperature-sensitive nanoporous carrier to a controlled-release water-reducing agent on the workability of fresh concrete mixtures.

[0095] Figure 3 (a) is an electron microscope image of the cement slurry with added nanoporous carrier in Example 1. Figure 3 (b) is an electron micrograph of cement slurry without the addition of nanoporous carriers.

[0096] Figure 4 Flowchart for the preparation of a temperature-sensitive nanoporous carrier-based controlled-release water-reducing agent. Detailed Implementation

[0097] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0098] In the following embodiments, the silane coupling agent used is coupling agent KH-540, whose molecular formula is C6H. 17 NO3Si was purchased from Yunsheng Chemical Co., Ltd.

[0099] The expanding agent used is UEA high-efficiency expanding agent, with an expansion rate of approximately 0.03% after 7 days, produced by Henan Xinmi Mingzhu Waterproof and Anticorrosive Materials Co., Ltd.

[0100] The polycarboxylate superplasticizer used is a high-efficiency superplasticizer with a solid content of 30%, produced by Jiangsu Subote New Material Co., Ltd.

[0101] The lignocellulose used was produced by Taian Anfeng New Material Technology Co., Ltd.

[0102] The poly-N-isopropylacrylamide mentioned above is derived from Aladdin and has the molecular formula CH3(C6H) 11 NO) n CH3 should be stored at a temperature of 2-5℃ during transportation.

[0103] The poly(N,N-dimethylacrylamide) is derived from Maclean's and has the molecular formula C5H9NO.

[0104] The polyethylene formaldehyde mentioned above originated from Hubei Langbowan Biomedical Co., Ltd.

[0105] The specific process for preparing temperature-sensitive nanoporous supports is as follows:

[0106] (A) Weigh out sodium silicate, dissolve it in a solvent, add additives, and disperse it evenly to form a sol;

[0107] (B) Add a thermosensitive polymer and a co-initiator to the sol, stir and mix thoroughly, then add a gel hardener. The addition of the gel hardener initiates gel formation, and the sol gradually thickens to obtain a colloidal gel. Allow the colloidal gel to stand and further solidify, then dry it to remove residual chemicals and generate a more stable microporous carrier, thus obtaining a temperature-sensitive nanoporous carrier.

[0108] The stirring speed in the above process was 1000 r / min, and the stirring time was 10 h.

[0109] Meanwhile, the temperature for forming a colloidal gel after adding the gel hardener was 18℃ and the time was 15min; the standing temperature was 5℃ and the standing time was 18h; the drying temperature was 15℃, the relative humidity was 35%, and the drying time was 48h.

[0110] The preparation method of the temperature-sensitive nanoporous carrier-based controlled-release water-reducing agent is as follows:

[0111] (1) The temperature-sensitive nanoporous carrier is mixed with water at 15°C and stirred evenly to form a basic carrier;

[0112] (2) Weigh out the controlled-release additive and disperse it in water, add the base carrier from step (1), and stir until uniform to obtain a carrier solution mixture.

[0113] (3) Weigh the rheology modifier and the functional modifier and disperse them in water to prepare a suspension. Then add the suspension to the carrier solution mixture one in step (2) and stir evenly to obtain the carrier solution mixture two.

[0114] (4) Continue to mix the polycarboxylate superplasticizer, dispersant, additives and stabilizer into the carrier solution mixture in step (3). Adjust the pH of the system to 12-13 using a pH adjuster and control the binding temperature of the carrier and superplasticizer to 28°C to obtain a temperature-sensitive nanoporous carrier with controllable release superplasticizer. Then store it in a brown clamp-mouth sample bottle and control the storage temperature to 10°C.

[0115] The preparation method of recycled coarse aggregate concrete includes the following steps:

[0116] (1) Take samples of recycled coarse aggregate, cement and fly ash according to the weight in the proportion, and pour them into a high-power single-shaft mixer for the first mixing. The mixing speed is 45r / min and the mixing time is 4min to obtain the first mixture.

[0117] (2) Add water to the first mixture and stir for a second time at a speed of 45 r / min for 3 min to obtain the second mixture;

[0118] (3) Add the temperature-sensitive nanoporous carrier's controllable release water-reducing agent, expansion agent and biomass fiber to the second mixture for a third stirring. The stirring speed is 50 r / min and the stirring time is 3 min to obtain the fresh concrete mixture.

[0119] Unless otherwise specified, all other raw materials or processing techniques are commercially available materials or conventional processing techniques in the field.

[0120] Example 1

[0121] (1) Preparation of temperature-sensitive nanoporous carrier: By weight, the following components are included: 300 parts sodium silicate, 350 parts solvent (water), 90 parts gel curing agent (ammonium chloride), 40 parts auxiliary agent (silane coupling agent), 20 parts co-initiator (ferrous ammonium sulfate), and 200 parts thermosensitive polymer (poly(N-isopropylacrylamide) (PNIPAM)). Then, the temperature-sensitive nanoporous carrier is prepared step by step according to the operation in the second technical solution of this invention.

[0122] (2) Preparation of a temperature-sensitive nanoporous carrier with controlled-release water-reducing agent: By weight, the following components are included: 260 parts polycarboxylate water-reducing agent, 180 parts temperature-sensitive nanoporous carrier, 60 parts dispersant (sodium n-heptylbenzenesulfonate), 70 parts dispersing aid (polyvinyl alcohol), 40 parts functional modifier (hydroxymethyl cellulose), 50 parts stabilizer (propylene glycol), 50 parts controlled-release additive (citric acid), 30 parts rheology modifier (nanodiatomaceous earth), 20 parts pH adjuster (sodium hydroxide), and 510 parts water. Then, the temperature-sensitive nanoporous carrier with controlled-release water-reducing agent is prepared step by step according to the operation in technical solution four of this invention.

[0123] (3) Preparation of workability-modified recycled coarse aggregate concrete: By weight, it includes the following components: 410 parts cement, 980 parts recycled coarse aggregate, 650 parts river sand, 110 parts fly ash, 10 parts temperature-sensitive nanoporous carrier controlled-release water-reducing agent, 48 parts expansion agent, 215 parts water, and 70 parts biomass fiber. Then, workability-modified recycled coarse aggregate concrete is prepared step by step according to the steps in the preparation method.

[0124] Example 2

[0125] (1) Preparation of temperature-sensitive nanoporous carrier: By weight, the following components are included: 300 parts sodium silicate, 350 parts solvent (water), 90 parts gel curing agent (ammonium chloride), 40 parts auxiliary agent (silane coupling agent), 20 parts co-initiator (ferrous ammonium sulfate), and 200 parts thermosensitive polymer (poly(N,N-dimethylacrylamide (PDMA)). Then, the temperature-sensitive nanoporous carrier is prepared step by step according to the operation in the second technical solution of this invention.

[0126] (2) Preparation of a temperature-sensitive nanoporous carrier with controlled-release water-reducing agent: By weight, the following components are included: 260 parts polycarboxylate water-reducing agent, 180 parts temperature-sensitive nanoporous carrier, 60 parts dispersant (sodium n-heptylbenzenesulfonate), 70 parts dispersing aid (polyvinyl alcohol), 40 parts functional modifier (hydroxymethyl cellulose), 50 parts stabilizer (propylene glycol), 50 parts controlled-release additive (citric acid), 30 parts rheology modifier (nanodiatomaceous earth), 20 parts pH adjuster (sodium hydroxide), and 510 parts water. Then, the temperature-sensitive nanoporous carrier with controlled-release water-reducing agent is prepared step by step according to the operation in technical solution four of this invention.

[0127] (3) Preparation of workability-modified recycled coarse aggregate concrete: By weight, it includes the following components: 410 parts cement, 980 parts recycled coarse aggregate, 650 parts river sand, 110 parts fly ash, 10 parts temperature-sensitive nanoporous carrier controlled-release water-reducing agent, 48 parts expansion agent, 215 parts water, and 70 parts biomass fiber. Then, workability-modified recycled coarse aggregate concrete is prepared step by step according to the steps in the preparation method.

[0128] Example 3

[0129] (1) Preparation of temperature-sensitive nanoporous carrier: By weight, the following components are included: 300 parts sodium silicate, 350 parts solvent (water), 90 parts gel curing agent (ammonium chloride), 40 parts auxiliary agent (silane coupling agent), 20 parts co-initiator (ferrous ammonium sulfate), and 200 parts thermosensitive polymer (polyvinyl formaldehyde (PVA)). Then, the temperature-sensitive nanoporous carrier is prepared step by step according to the operation in the second technical solution of this invention.

[0130] (2) Preparation of a temperature-sensitive nanoporous carrier with controlled-release water-reducing agent: By weight, the following components are included: 260 parts polycarboxylate water-reducing agent, 180 parts temperature-sensitive nanoporous carrier, 60 parts dispersant (sodium n-heptylbenzenesulfonate), 70 parts dispersing aid (polyvinyl alcohol), 40 parts functional modifier (hydroxymethyl cellulose), 50 parts stabilizer (propylene glycol), 50 parts controlled-release additive (citric acid), 30 parts rheology modifier (nanodiatomaceous earth), 20 parts pH adjuster (sodium hydroxide), and 510 parts water. Then, the temperature-sensitive nanoporous carrier with controlled-release water-reducing agent is prepared step by step according to the operation in technical solution four of this invention.

[0131] (3) Preparation of workability-modified recycled coarse aggregate concrete: By weight, it includes the following components: 410 parts cement, 980 parts recycled coarse aggregate, 650 parts river sand, 110 parts fly ash, 10 parts temperature-sensitive nanoporous carrier controlled-release water-reducing agent, 48 parts expansion agent, 215 parts water, and 70 parts biomass fiber. Then, workability-modified recycled coarse aggregate concrete is prepared step by step according to the steps in the preparation method.

[0132] Example 4

[0133] (1) Preparation of temperature-sensitive nanoporous carrier: By weight, the following components are included: 300 parts sodium silicate, 350 parts solvent (water), 90 parts gel curing agent (ammonium chloride), 40 parts auxiliary agent (silane coupling agent), 20 parts co-initiator (ferrous ammonium sulfate), and 200 parts thermosensitive polymer (poly(N-isopropylacrylamide) (PNIPAM)). Then, the temperature-sensitive nanoporous carrier is prepared step by step according to the operation in the second technical solution of this invention.

[0134] (2) Preparation of a temperature-sensitive nanoporous carrier with controlled-release water-reducing agent: The agent comprises the following components by weight: 260 parts polycarboxylate water-reducing agent, 180 parts temperature-sensitive nanoporous carrier, 60 parts dispersant (sodium n-heptylbenzenesulfonate), 70 parts dispersing aid (polyvinyl alcohol), 40 parts functional modifier (hydroxymethyl cellulose), 50 parts stabilizer (propylene glycol), 50 parts controlled-release additive (citric acid), 30 parts rheology modifier (nanodiatomaceous earth), 15 parts pH adjuster (sodium hydroxide), and 510 parts water. The temperature-sensitive nanoporous carrier with controlled-release water-reducing agent is then prepared step-by-step according to the operation described in section four of this invention.

[0135] (3) Preparation of workability-modified recycled coarse aggregate concrete: By weight, it includes the following components: 410 parts cement, 980 parts recycled coarse aggregate, 650 parts river sand, 110 parts fly ash, 10 parts temperature-sensitive nanoporous carrier controlled-release water-reducing agent, 48 parts expansion agent, 215 parts water, and 70 parts biomass fiber. Then, workability-modified recycled coarse aggregate concrete is prepared step by step according to the steps in the preparation method.

[0136] Example 5

[0137] (1) Preparation of temperature-sensitive nanoporous carrier: By weight, the following components are included: 300 parts sodium silicate, 350 parts solvent (water), 90 parts gel curing agent (ammonium chloride), 40 parts auxiliary agent (silane coupling agent), 20 parts co-initiator (ferrous ammonium sulfate), and 200 parts thermosensitive polymer (poly(N-isopropylacrylamide) (PNIPAM)). Then, the temperature-sensitive nanoporous carrier is prepared step by step according to the operation in the second technical solution of this invention.

[0138] (2) Preparation of a temperature-sensitive nanoporous carrier with controlled-release water-reducing agent: The agent comprises the following components by weight: 260 parts polycarboxylate water-reducing agent, 100 parts temperature-sensitive nanoporous carrier, 60 parts dispersant (sodium n-heptylbenzenesulfonate), 70 parts dispersing aid (polyvinyl alcohol), 40 parts functional modifier (hydroxymethyl cellulose), 50 parts stabilizer (propylene glycol), 50 parts controlled-release additive (citric acid), 30 parts rheology modifier (nanodiatomaceous earth), 20 parts pH adjuster (sodium hydroxide), and 510 parts water. The temperature-sensitive nanoporous carrier with controlled-release water-reducing agent is then prepared step-by-step according to the operation described in section four of this invention.

[0139] (3) Preparation of workability-modified recycled coarse aggregate concrete: By weight, it includes the following components: 410 parts cement, 980 parts recycled coarse aggregate, 650 parts river sand, 110 parts fly ash, 10 parts temperature-sensitive nanoporous carrier controlled-release water-reducing agent, 48 parts expansion agent, 215 parts water, and 70 parts biomass fiber. Then, workability-modified recycled coarse aggregate concrete is prepared step by step according to the steps in the preparation method.

[0140] Example 6

[0141] (1) Preparation of temperature-sensitive nanoporous carrier: By weight, the following components are included: 300 parts sodium silicate, 350 parts solvent (water), 90 parts gel curing agent (ammonium chloride), 40 parts auxiliary agent (silane coupling agent), 20 parts co-initiator (ferrous ammonium sulfate), and 200 parts thermosensitive polymer (poly(N-isopropylacrylamide) (PNIPAM)). Then, the temperature-sensitive nanoporous carrier is prepared step by step according to the operation in the second technical solution of this invention.

[0142] (2) Preparation of a temperature-sensitive nanoporous carrier with controlled-release water-reducing agent: By weight, the following components are included: 260 parts polycarboxylate water-reducing agent, 180 parts temperature-sensitive nanoporous carrier, 60 parts dispersant (sodium n-heptylbenzenesulfonate), 70 parts dispersing aid (polyvinyl alcohol), 40 parts functional modifier (hydroxymethyl cellulose), 50 parts stabilizer (propylene glycol), 50 parts controlled-release additive (citric acid), 30 parts rheology modifier (nanodiatomaceous earth), 20 parts pH adjuster (sodium hydroxide), and 510 parts water. Then, the temperature-sensitive nanoporous carrier with controlled-release water-reducing agent is prepared step by step according to the operation in technical solution four of this invention.

[0143] (3) Preparation of workability-modified recycled coarse aggregate concrete: By weight, it includes the following components: 410 parts cement, 980 parts recycled coarse aggregate, 650 parts river sand, 110 parts fly ash, 15 parts temperature-sensitive nanoporous carrier controlled-release water-reducing agent, 48 parts expansion agent, 215 parts water, and 70 parts biomass fiber. Then, workability-modified recycled coarse aggregate concrete is prepared step by step according to the steps in the preparation method.

[0144] Example 7

[0145] (1) Preparation of temperature-sensitive nanoporous carrier: By weight, the following components are included: 300 parts sodium silicate, 350 parts solvent (water), 90 parts gel curing agent (ammonium chloride), 40 parts auxiliary agent (silane coupling agent), 20 parts co-initiator (ferrous ammonium sulfate), and 200 parts thermosensitive polymer (poly(N-isopropylacrylamide) (PNIPAM)). Then, the temperature-sensitive nanoporous carrier is prepared step by step according to the operation in the second technical solution of this invention.

[0146] (2) Preparation of a temperature-sensitive nanoporous carrier with controlled-release water-reducing agent: By weight, the following components are included: 260 parts polycarboxylate water-reducing agent, 180 parts temperature-sensitive nanoporous carrier, 60 parts dispersant (sodium n-heptylbenzenesulfonate), 70 parts dispersing aid (polyvinyl alcohol), 40 parts functional modifier (hydroxymethyl cellulose), 50 parts stabilizer (propylene glycol), 50 parts controlled-release additive (citric acid), 30 parts rheology modifier (nanodiatomaceous earth), 20 parts pH adjuster (sodium hydroxide), and 510 parts water. Then, the temperature-sensitive nanoporous carrier with controlled-release water-reducing agent is prepared step by step according to the operation in technical solution four of this invention.

[0147] (3) Preparation of workability-modified recycled coarse aggregate concrete: By weight, it includes the following components: 410 parts cement, 980 parts recycled coarse aggregate, 650 parts river sand, 110 parts fly ash, 5 parts temperature-sensitive nanoporous carrier controlled-release water-reducing agent, 48 parts expansion agent, 215 parts water, and 70 parts biomass fiber. Then, workability-modified recycled coarse aggregate concrete is prepared step by step according to the steps in the preparation method.

[0148] Comparative Example 1:

[0149] Compared with Example 1, most of the contents are the same, except that the addition of the thermosensitive polymer is omitted in the preparation of the temperature-sensitive nanoporous carrier.

[0150] Comparative Example 2:

[0151] The process is largely the same as in Example 1, except that poly(N-isopropylacrylamide) was replaced with an equal mass of polyvinyl lactam polymer (a non-thermal-sensitive polymer) during the preparation of the temperature-sensitive nanoporous carrier.

[0152] Comparative Example 3:

[0153] Compared with Example 1, most of the process is the same, except that the addition of the auxiliary agent (silane coupling agent) is omitted in the preparation of the temperature-sensitive nanoporous carrier.

[0154] Comparative Example 4:

[0155] Compared with Example 1, most of them are the same, except that in the preparation of the temperature-sensitive nanoporous carrier for the controlled release of water-reducing agent, the temperature-sensitive nanoporous carrier is replaced with an equal mass of natural zeolite powder.

[0156] Comparative Example 5:

[0157] Compared with Example 1, most of them are the same, except that the addition of temperature-sensitive nanoporous carrier is omitted in the preparation of the temperature-sensitive nanoporous carrier for the controlled release of water-reducing agent.

[0158] Comparative Example 6:

[0159] Compared with Example 1, most of the contents are the same, except that the dispersant (sodium n-heptylbenzenesulfonate) is omitted in the preparation of the temperature-sensitive nanoporous carrier controlled-release water-reducing agent.

[0160] Comparative Example 7:

[0161] Compared with Example 1, most of the contents are the same, except that the addition of the functional modifier (hydroxymethyl cellulose) is omitted in the preparation of the temperature-sensitive nanoporous carrier controlled-release water-reducing agent.

[0162] Comparative Example 8:

[0163] Compared with Example 1, most of them are the same, except that the controlled-release additive (citric acid) is omitted in the preparation of the temperature-sensitive nanoporous carrier controlled-release water-reducing agent.

[0164] Comparative Example 9:

[0165] Compared with Example 1, most of them are the same, except that the addition of rheology modifier (nanodiatomite) is omitted in the preparation of the temperature-sensitive nanoporous carrier controlled release water-reducing agent.

[0166] Comparative Example 10:

[0167] Compared with Example 1, most of the contents are the same, except that the addition of pH adjuster (sodium hydroxide) is omitted in the preparation of the temperature-sensitive nanoporous carrier controlled-release water-reducing agent.

[0168] Comparative Example 11:

[0169] Compared with Example 1, most of the contents are the same, except that the binding temperature between the carrier and the water-reducing agent is reduced to 15°C during the preparation of the temperature-sensitive nanoporous carrier for controlled release of water-reducing agent.

[0170] Comparative Example 12:

[0171] The two methods are largely the same as in Example 1, except that the addition of biomass fibers is omitted in the preparation of recycled coarse aggregate concrete.

[0172] Then, the preparation method was further improved through performance evaluation and optimization. The workability, mechanical properties, freeze-thaw resistance, and pore structure of the prepared recycled coarse aggregate concrete samples were tested. Based on the test results, the preparation methods of the temperature-sensitive nanoporous carrier and the controlled-release water-reducing agent of the temperature-sensitive nanoporous carrier were adjusted to achieve optimal performance.

[0173] Workability Testing: According to GB 8076-2018 "Concrete Admixtures", the initial slump, initial spread, and initial bleeding rate of the concrete were tested, and workability was evaluated in conjunction with relevant parameters. Furthermore, the workability evaluation adopted a numerical standard of "good, good, average, poor, and very poor" based on published invention patents. The patent application publication number is CN115449024 A, and the patent title is "Preparation of a Workability-Retaining Polycarboxylate Superplasticizer".

[0174] Mechanical property testing method: According to GB / T 50081-2019, the compressive strength test was carried out on a standard cubic specimen with dimensions of 100mm×100mm×100mm. The curing period of the specimen was 28 days, and the average value of the three results was taken as the experimental value of compressive strength.

[0175] Freeze-thaw resistance test: According to the rapid freezing method specified in GB / T 50082-2009, concrete specimens cured for 24 days were removed from the standard curing room and immersed in 20℃ clean water for 4 days. During immersion, the water level should be 2-3 cm above the top surface of the specimen. After 28 days of curing, the specimens were placed in a TDR-28 type concrete freeze-thaw testing machine for rapid freeze-thaw cycle testing. The freeze-thaw medium was tap water. After 300 freeze-thaw cycles, the control system was paused, the surface moisture of the specimens was wiped dry, and then the mass loss and dynamic modulus of elasticity were tested. The mass loss rate and relative dynamic modulus of elasticity were used to characterize the freeze-thaw resistance of concrete, and the calculation formulas are as follows:

[0176]

[0177] Where: ΔW 300 W0 is the mass loss rate of the concrete specimen after 300 freeze-thaw cycles; W0 is the mass of the concrete specimen before the freeze-thaw cycles. 300 The quality of the concrete specimen after undergoing 300 freeze-thaw cycles.

[0178]

[0179] Where: E d E represents the relative dynamic modulus of elasticity of a concrete specimen after 300 freeze-thaw cycles. d,0 E represents the dynamic elastic modulus of a concrete specimen before it undergoes freeze-thaw cycles. d,300 The dynamic elastic modulus of the concrete specimen after 300 freeze-thaw cycles.

[0180] Porosity test method: The porosity and average pore size of the mortar were measured using an Autopore IV 9500 fully automatic mercury intrusion porosimeter, with a maximum mercury intrusion pressure of 33,000 psi. A 5 mm cube was taken from a 28-day cured concrete specimen using a cutting machine, with the sampling location at the center of the specimen, avoiding the aggregate area. The sample was then immersed in anhydrous ethanol to prevent hydration.

[0181] The working performance, mechanical properties, frost resistance and pore structure of the above component samples were evaluated, and the test results and evaluation results are shown in Table 1-3.

[0182] Table 1. Workability of Recycled Coarse Aggregate Concrete in Examples 1-7 and Comparative Examples 1-12

[0183]

[0184]

[0185] Table 2 shows the compressive strength and pore structure of recycled coarse aggregate concrete in Examples 1-7 and Comparative Examples 1-12.

[0186]

[0187]

[0188] Table 3. Freeze-thaw resistance of recycled coarse aggregate concrete in Examples 1-7 and Comparative Examples 1-12

[0189]

[0190]

[0191] The results in Tables 1-3 show that the temperature-sensitive nanoporous carrier-based controlled-release water-reducing agent prepared in this invention can effectively regulate the workability, mechanical properties, pore structure, and freeze-thaw resistance of recycled concrete. Specifically, recycled concrete with good workability was obtained in Examples 1-7, indicating that PNIPAM, PDMA, and PVA, as thermosensitive polymers, effectively control the release of water-reducing agents in the nanocarrier. A comparison of the results in Examples 1, 6, and 7 shows that there is an upper limit to the loading amount of water-reducing agent on the nanoporous carrier. In Comparative Examples 1 and 2, due to the omission of the thermosensitive polymer, the nanoporous carrier can only perform a simple loading function. The results show that the thermosensitive polymer successfully combines with the nanoporous carrier and achieves the function of controlling the release of water-reducing agents. In Comparative Example 3, due to the omission of the silane coupling agent, the nanoporous carrier could not be synthesized, but due to the introduction of the thermosensitive polymer, the final effect was slightly better than that of Comparative Example 5. In Comparative Example 4, because the nanoporous carrier was replaced with natural zeolite powder, the effect of controlling the release of water-reducing agents could not be achieved, resulting in poor performance improvement. In Comparative Examples 6-10, because the raw materials for preparing the temperature-sensitive nanoporous carrier-based controlled-release water-reducing agent were omitted, it was impossible to synthesize a water-reducing agent with improved conditioning effects. In Comparative Example 11, due to the lower bonding temperature between the water-reducing agent and the carrier, the polymer chains within the micropores of the nanocarrier stretched and intertwined, leading to micropore closure. This hindered the water-reducing agent from entering the carrier's micropores, resulting in a significant decrease in the loading capacity and a reduced effect on improving the workability of concrete. In Comparative Example 12, the omission of biomass fibers led to a decrease in the water-reducing agent's effect on improving recycled concrete.

[0192] Table 1 shows the workability of all groups of recycled concrete, including initial slump, initial spread, and initial bleeding rate. In Example 1, the water-reducing agent and the nanoporous carrier were well integrated. During the fresh mixing stage, the water-reducing agent components were released from the nanoporous carrier in stages and combined with recycled coarse aggregate and cement particles. The hydrophobic groups delayed the absorption of free water in the mixture by the pores of the recycled aggregate, while also hindering the agglomeration of cement particles, thereby improving the bleeding and flowability of the recycled concrete. Table 2 shows the compressive strength and pore structure of all groups of recycled concrete. In Example 1, due to the good dispersing effect of the water-reducing agent, the aggregate and cement particles in the mixture were more evenly distributed, while the hydration reaction rate was slowed down, and the cement particles were hydrated more completely. In addition, the biomass fibers played a good filling effect. The results showed that the recycled concrete in Example 1 had a porosity of only 9.3% and an average particle size of 18.1 nm, indicating that the recycled concrete was more dense and had a finer microstructure. Figure 3(a) This results in a 28-day compressive strength of 72.6 MPa for the recycled concrete. Table 3 shows the freeze-thaw resistance of all groups of recycled concrete, including the mass loss rate and relative dynamic modulus of elasticity. In Example 1, the average pore size of the recycled concrete is only 18.1 nm, which means a lower freezing point and a lower freezing rate. Furthermore, during the freeze-thaw cycle of the recycled concrete, the nanoporous carrier, which can autonomously adapt to changes in ambient temperature, can absorb and release free water accordingly, thereby reducing the tensile stress on the pore walls of the recycled concrete. The results show that the recycled concrete in Example 1 has a mass loss rate of only 0.17% and a relative dynamic modulus of elasticity as high as 95.7%, indicating good freeze-thaw resistance.

[0193] Based on the above results, it can be observed that the temperature-sensitive nanoporous carrier controlled release water-reducing agent technology can significantly improve the workability of recycled coarse aggregate concrete and effectively reduce bleeding, water seepage, and segregation. In addition, by improving the pore structure of cement paste and the density of recycled coarse aggregate, the mechanical properties of concrete are enhanced. It also saves on the amount of polycarboxylate water-reducing agent used, resulting in strong economic and environmental benefits.

[0194] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A temperature-sensitive nanoporous carrier with improved workability, characterized in that, Based on a total weight of 1000 parts, it is composed of the following raw material components in parts by weight: 280-320 parts sodium silicate, 330-370 parts solvent, 80-100 parts gel curing agent, 30-50 parts additives, 15-25 parts co-initiator, and 180-220 parts heat-sensitive polymer. The gel hardener is ammonium chloride; The solvent is water; The additive is a silane coupling agent; The co-initiator is one or a combination of two of ferrous ammonium sulfate or ferrous sulfate. The thermosensitive polymer is one or a combination of several of poly(N-isopropylacrylamide), poly(N,N-dimethylacrylamide), and polyethylene formaldehyde.

2. The method for preparing a workability-modified temperature-sensitive nanoporous carrier as described in claim 1, characterized in that, Includes the following steps: (A) Weigh out sodium silicate, dissolve it in a solvent, add additives, and disperse it evenly to form a sol; (B) Add the thermosensitive polymer and co-initiator to the sol, stir and mix thoroughly, then add the gel hardener to obtain a colloidal gel, let it stand, and dry to obtain a temperature-sensitive nanoporous carrier.

3. The method for preparing a workability-modified temperature-sensitive nanoporous carrier according to claim 2, characterized in that, The reaction temperature for forming a colloidal gel after adding the gel hardener is 15-20℃, and the reaction time is 10-20 min. The settling temperature is 0-10℃, and the settling time is 12-24 hours; The temperature during the drying stage is 10-20℃, the relative humidity is 30%-40%, and the drying time is 24-72 hours.

4. A controllable-release water-reducing agent based on a workability-modified temperature-sensitive nanoporous carrier, characterized in that, The raw material components include the following parts by weight: 220-300 parts of polycarboxylate superplasticizer, 150-210 parts of temperature-sensitive nanoporous carrier as described in claim 1, 50-70 parts of dispersant, 60-80 parts of dispersing aid, 30-50 parts of functional modifier, 40-60 parts of stabilizer, 40-60 parts of controlled-release additive, 25-35 parts of rheology modifier, 15-25 parts of pH adjuster, and 450-570 parts of water.

5. The controllable release water-reducing agent based on a workability-modified temperature-sensitive nanoporous carrier according to claim 4, characterized in that, The dispersant is sodium n-heptylbenzenesulfonate; the dispersing aid is polyvinyl alcohol; the functional modifier is hydroxymethyl cellulose; the stabilizer is propylene glycol; the controlled-release additive is citric acid; the rheology modifier is nano-diatomaceous earth; and the pH adjuster is sodium hydroxide.

6. The method for preparing a controllable release water-reducing agent based on a workability-modified temperature-sensitive nanoporous carrier according to claim 4, characterized in that, Includes the following steps: (1) The temperature-sensitive nanoporous carrier was mixed with water at 15°C and stirred evenly to form a basic carrier; (2) Weigh out the controlled-release additive and disperse it in water, add the base carrier from step (1), and stir until homogeneous to obtain a carrier solution mixture. (3) Weigh the rheology modifier and the functional modifier and disperse them in water to prepare a suspension. Then add the suspension to the carrier solution mixture one in step (2) and stir evenly to obtain the carrier solution mixture two. (4) Continue to mix the polycarboxylate superplasticizer, dispersant, dispersant and stabilizer into the carrier solution mixture in step (3). Adjust the pH of the system to 12-13 using a pH adjuster and control the binding temperature of the carrier and superplasticizer to 28°C to obtain a temperature-sensitive nanoporous carrier with controllable release superplasticizer. Then store it in a brown clamp bottle and control the storage temperature to 10°C.

7. A workability-modified recycled coarse aggregate concrete, characterized in that, The raw material components include the following parts by weight: Cement: 400-420 parts; Recycled coarse aggregate: 960-1000 parts; River sand: 640-660 parts; Fly ash: 100-120 parts; Controlled-release water-reducing agent of temperature-sensitive nanoporous carrier as described in claim 4: 8-12 parts; Expanding agent: 45-50 parts; Water: 210-220 parts; Biomass fiber: 65-75 parts.

8. The workability-improved recycled coarse aggregate concrete according to claim 7, characterized in that, The cement is PO 42.5 ordinary Portland cement, with a 28-day compressive strength of 46.2-53.2 MPa; The recycled coarse aggregate is derived from C40 waste concrete and is prepared through crushing, washing, screening, sorting, and drying, with an apparent density of 2562 kg / m³. 3 The crushing index was 16.8%. The fly ash is Grade I fly ash, with a loss on ignition of 2.38% and a sulfur trioxide content of 1.67%.

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