Water-soluble polyurea early strength agent as well as preparation method and application thereof

Abstract

The invention discloses a water-soluble polyurea early strength agent as well as a preparation method and application thereof. The method comprises the following steps: reacting diaminopolyether, diisocyanate and a catalyst to obtain a polyurea prepolymer; adding a chain extender into the polyurea prepolymer, and continuously reacting to obtain polyurea; and finally, dropwise adding polyurea into water, and continuously stirring in the dropwise adding process to obtain the transparent water-soluble polyurea early strength agent. The water-soluble polyurea early strength agent is applied to mixing of cement paste, mortar and concrete. The polyurea provided by the invention has rich carboxyl sites, can be adsorbed on the surfaces of cement particles, prevents cement from agglomerating, improves the cohesiveness and water-retaining property of slurry, is better in workability, and can be uniformly dispersed and fully reacted in concrete, so that the hydration of the cement is accelerated, and the early strength of the cement, the mortar and the concrete is improved.

Description

Technical Field

[0001] The invention belongs to the field of building material concrete admixtures, in particular to a water-soluble polyurea early strength agent and a preparation method and application thereof. Background Art

[0002] With the rapid advancement of large-scale infrastructure construction in my country, the demand for concrete continues to rise, especially in order to speed up the construction progress and reduce the cost of project construction, higher requirements are put forward for the early strength of concrete. For example, in the production process of prefabricated components for bridges and prefabricated buildings, in order to speed up the turnover efficiency of the formwork, the strength of the prefabricated components is required to be no less than 75% of the design value when leaving the factory. Therefore, in order to improve the early strength of ready-mixed concrete, engineering and technical personnel accelerate the hardening rate of concrete by adding various types of inorganic, organic and composite early strength agents such as chlorides, sulfates, carbonates, triethanolamine, etc., which is convenient for winter, emergency rescue or rapid construction.

[0003] Document No. 202410057762.9 discloses a high-viscosity polyurethane cement mortar and a preparation method thereof, which adds water-based polyurethane to a mortar containing polypropylene and carbon fiber to prepare a high-viscosity polyurethane cement mortar without a curing agent, thereby improving the bonding strength and mechanical strength of the mortar.

[0004] At present, there are still various problems in the application of concrete early strength agents. For example, although triethanolamine-based organic early strength agents can improve the early strength of concrete, they have a certain retarding effect. Polyurethane or polyurea-based early strength agents, due to their large molecular weight and fewer hydrophilic groups, can only be dispersed into emulsions in water (particle size greater than 100nm), exist in water as micelles, and cannot fully react with concrete. When used in a complex alkaline concrete environment, they have poor stability and are prone to aggregation and precipitation. They can only increase the later toughness but cannot improve the early strength. Therefore, it is necessary to develop new water-soluble early strength agents to improve the early strength of concrete. Summary of the invention

[0005] In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a water-soluble polyurea early strength agent and a preparation method and application thereof.

[0006] The technical solution of the present invention to solve the technical problem of the method is to provide a method for preparing a water-soluble polyurea early strength agent, characterized in that the method comprises the following steps: (1) reacting diamino polyether, diisocyanate and catalyst in an anhydrous environment at 60-80°C with continuous stirring until the solution viscosity reaches above 2 Pa·s, stopping the reaction to obtain a polyurea prepolymer; (2) adding a chain extender to a polyurea prepolymer, stirring and reacting at 60-80°C in an anhydrous environment until the solution viscosity reaches above 5 Pa·s, and then stopping the reaction to obtain polyurea; (3) Add polyurea dropwise into water while stirring continuously to obtain a transparent water-soluble polyurea early strength agent.

[0007] The technical solution of the present invention to solve the technical problem of the early strength agent is to provide a water-soluble polyurea early strength agent prepared by the preparation method, characterized in that the polyurea is a small-sized micelle below 50nm in water, and the visible light transmittance of the water-soluble polyurea early strength agent is ≥90%.

[0008] The technical solution of the present invention to solve the application technical problem is to provide an application of the water-soluble polyurea early strength agent in cement paste, mortar and concrete mixing, characterized in that the water-soluble polyurea early strength agent is added together with cementitious materials, aggregates, admixtures and water.

[0009] Compared with the prior art, the present invention has the following beneficial effects: (1) The polyurea of ​​the present invention has a low molecular weight, is rich in carboxyl groups, amino groups and urea bond groups in its molecular structure, has excellent dispersibility in water, high solubility, and is a stable product. It is not easy to aggregate in a highly alkaline cement slurry environment, and is easy to use in cement slurry, mortar and concrete mixing.

[0010] (2) The polyurea of ​​the present invention has abundant carboxyl sites, which can be adsorbed on the surface of cement particles, prevent cement from agglomerating, improve the cohesiveness and water retention of the slurry, and improve workability. It can be evenly dispersed and fully reacted in concrete, thereby accelerating cement hydration and improving the early strength of cement, mortar and concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a comparison chart of the concrete compressive strength at 1d, 3d and 7d of Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 of the present invention; Figure 2 The dynamic light scattering test results of Examples 1-4 of the present invention are shown; Figure 3 This is a transmission electron microscope image of the solute polyurea in the water-soluble polyurea early strength agent of Example 1 of the present invention. DETAILED DESCRIPTION

[0012] The specific embodiments of the present invention are given below. The specific embodiments are only used to further illustrate the present invention in detail and do not limit the protection scope of the present invention.

[0013] The present invention provides a method for preparing a water-soluble polyurea early strength agent (hereinafter referred to as the method), characterized in that the method comprises the following steps: (1) reacting diamino polyether, diisocyanate and catalyst in an anhydrous environment at 60-80°C (preferably 70°C) with continuous stirring until the solution viscosity reaches 2 Pa·s or more, stopping the reaction to obtain a polyurea prepolymer; Preferably, in step (1), the water content of each of the diamino polyether, the diisocyanate and the catalyst is lower than 0.05 wt %; a drying process is used to achieve the required water content, and the drying is carried out by vacuum drying, barium oxide drying or 4A molecular sieve drying.

[0014] Preferably, in step (1), the reactor is a glass, enamel or stainless steel reactor.

[0015] Preferably, in step (1), the diamino polyether is at least one of polytetramethylene furan diamine, polyoxyethylene ether diamine and polyoxypropylene ether diamine, and has a number average molecular weight of 250-2000 g / mol.

[0016] Preferably, in step (1), in order to ensure good solubility of polyurea in water, the number average molecular weight of polytetrahydrofuran diamine is 250-1000 g / mol, and the number average molecular weight of polyoxyethylene ether diamine and polyoxypropylene ether diamine is 500-1500 g / mol.

[0017] Preferably, in step (1), the diisocyanate is at least one of toluene diisocyanate, diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate and isophorone diisocyanate.

[0018] Preferably, in step (1), the catalyst is dibutyltin dilaurate, stannous isooctanoate or triethylenediamine, preferably dibutyltin dilaurate.

[0019] (2) adding a chain extender to the polyurea prepolymer, stirring and reacting at 60-80°C (preferably 70°C) in an anhydrous environment until the solution viscosity reaches 5 Pa·s or more, stopping the reaction, and obtaining polyurea; Preferably, in step (2), the chain extender contains two amino groups and at least one carboxyl group, which can improve the solubility of polyurea in water, and is specifically any one of lysine, diaminopimelic acid or 2,3-diaminopropionic acid.

[0020] Preferably, in step (2), the mass ratio of diisocyanate: diamino polyether: chain extender is 100:50-90:10-20, preferably 100:55-80:12-19, more preferably 100:60-70:15-18, and further preferably 100:65-68:16-17.

[0021] Preferably, in step (2), the mass ratio of diisocyanate: diamino polyether: chain extender: catalyst is 100:50~90:10~20:0.01~1, preferably 100:55~80:12~19:0.02~0.5, more preferably 100:60~70:15~18:0.05~0.1, and further preferably 100:65~68:16~17:0.06~0.08.

[0022] Preferably, in step (2), the polyurea comprises a hard segment and a soft segment, the hard segment comprises diisocyanate and a chain extender, and the soft segment comprises diamino polyether, and the hard segment and the soft segment are connected via a urea bond formed by condensation of an amino group and an isocyanate.

[0023] Preferably, in step (2), the polyurea is rich in hydrophilic groups such as amino groups, carboxyl groups and urea bonds. To ensure good solubility of the polyurea in water, the number average molecular weight of the polyurea is 4000-10000 g / mol, preferably 5000-8000 g / mol.

[0024] Preferably, in step (1) and step (2), the anhydrous environment is an anhydrous and oxygen-free environment, which is achieved by nitrogen or inert gas protection, and the inert gas is argon.

[0025] Preferably, in step (1) and step (2), the reaction time is 2 to 4 hours, preferably 3 hours.

[0026] (3) Add polyurea dropwise into water and stir continuously during the addition process to allow the polyurea to be completely dissolved or highly stably and evenly dispersed in the water to obtain a transparent water-soluble polyurea early strength agent.

[0027] Preferably, step (3) is performed at room temperature.

[0028] Preferably, in step (3), the mass ratio of polyurea to water is 1:10-100, preferably 1:20-90, more preferably 1:50-80.

[0029] Preferably, in step (3), the water-soluble polyurea early strength agent is an aqueous solution of polyurea terminated with amino groups at both ends.

[0030] Preferably, in step (3), the polyurea is highly dispersed in water into small-sized nano-micelles of less than 50 nm, and the appearance of the water-soluble polyurea early strength agent is highly transparent, with a visible light transmittance of ≥90% (preferably ≥95%).

[0031] The invention also provides a water-soluble polyurea early strength agent prepared by the preparation method.

[0032] The present invention also provides an application of the water-soluble polyurea early strength agent in cement paste, mortar and concrete mixing, characterized in that the water-soluble polyurea early strength agent is added together with a cementitious material, an aggregate, an admixture and water.

[0033] Preferably, the cementitious material is at least one of cement, fly ash or silica fume; the aggregate is crushed stone and / or sand; the admixture is at least one of a water reducer, a retarder, a pumping agent, a waterproofing agent, a thickener, an air entraining agent and an existing early strength agent. In order to further improve the early strength effect of the water-soluble polyurea early strength agent, an existing early strength agent is added to the system; the existing early strength agent is at least one of calcium chloride, triethanolamine and sodium sulfate. The combined use of multiple early strength agents provides a richer and more effective multi-faceted means for adjusting the early strength of cement paste, mortar and concrete. The water-soluble polyurea early strength agent can be used alone or mixed with one or more of at least one existing admixture to improve the comprehensive performance of cement products and meet different application requirements.

[0034] Preferably, due to the different concentrations of the water-soluble polyurea early strength agent, the mass of the solute polyurea in the water-soluble polyurea early strength agent accounts for 0.001-0.1% (preferably 0.003-0.015%, more preferably 0.005-0.01%) of the mass of the cementitious material, which can improve the cohesiveness and water retention of the slurry, promote cement hydration, and increase the early strength.

[0035] Preferably, in cement slurry mixing, water-soluble polyurea early strength agent is added together with cement, fly ash, silica fume and admixtures; the mass of polyurea accounts for 0.001-0.05% (preferably 0.002-0.01%) of the mass of cementitious materials. In cement slurry mixing, water-soluble polyurea early strength agent has a wide range of application prospects in pure slurry experiments, material compatibility experiments, cement product manufacturing and crack repair projects.

[0036] Preferably, in the mortar mixing, the water-soluble polyurea early strength agent is added together with cement, fly ash, silica fume, sand and admixtures; the mass of polyurea accounts for 0.002-0.08% (preferably 0.005-0.06%) of the mass of the cementitious material. In the mortar mixing, the water-soluble polyurea early strength agent has a wide range of application prospects in the reinforcement of existing buildings, winter wall construction and rapid road repair.

[0037] Preferably, in concrete mixing, water-soluble polyurea early strength agent is added together with cement, fly ash, silica fume, sand, crushed stone and admixtures; the mass of polyurea accounts for 0.005-0.1% (preferably 0.006-0.01%) of the mass of cementitious materials. In concrete mixing, water-soluble polyurea early strength agent has broad application prospects in the production of high-speed railways, bridges, tunnels, subways and prefabricated components of assembled buildings.

[0038] The application method of the water-soluble polyurea early strength agent of the present invention is the same as the application method of the existing early strength agent. Those skilled in the art can determine the optimal dosage through laboratory small batch experiments according to actual engineering needs. When the early strength improvement is not obvious, the dosage can be increased. When the early strength is significantly increased and meets the requirements, the dosage can be reduced to reduce costs. However, during use, the dosage of the water-soluble polyurea early strength agent should be gradually increased to avoid significantly increasing the rapid hardening and difficulty in construction that may result.

[0039] Example 1 Preparation of water-soluble polyurea early strength agent: (1) 100 g of pre-dried 1,6-hexamethylene diisocyanate, 50 g of polyoxyethylene ether diamine (number average molecular weight of 500 g / mol) and 0.05 g of dibutyltin dilaurate were added into a 1 L glass reactor equipped with a magnetic stirrer, and stirred at 70 ° C for 3 h under nitrogen protection to obtain a polyurea prepolymer; (2) 10 g of diaminopimelic acid was added as a chain extender to the polyurea prepolymer, and the mixture was stirred and reacted at 70 °C for 3 h under nitrogen protection to obtain polyurea (number average molecular weight 6500 g / mol); (3) At room temperature, polyurea was added dropwise into 0.74 kg of water with continuous stirring to obtain a transparent water-soluble polyurea early strength agent (visible light transmittance of 98%).

[0040] In order to evaluate the early strength effect of water-soluble polyurea early strength agent in concrete mixing, 1500g cement, 1000g fly ash, 1000g silica fume, 8000g sand, 11000g crushed stone, 200g water reducer, 218.8g water-soluble polyurea early strength agent of Example 1 and 500g water were added to a concrete mixer, and mixed evenly according to the relevant method of GB / T 8076-2008 "Concrete Admixtures". The appearance and setting time of the concrete are shown in Table 1. After steam curing for 1d, 3d and 7d, the compressive strength of the concrete test blocks was measured as shown in Table 1 and Figure 1 shown.

[0041] Example 2 Preparation of water-soluble polyurea early strength agent: (1) 100 g of pre-dried isophorone diisocyanate, 80 g of polyoxypropylene ether diamine (number average molecular weight of 1500 g / mol) and 0.1 g of stannous isooctanoate were added into a 1 L stainless steel reactor equipped with a mechanical stirrer, and stirred at 60 ° C for 3.5 h under nitrogen protection to obtain a polyurea prepolymer; (2) 19 g of lysine was added as a chain extender to the polyurea prepolymer, and the mixture was stirred and reacted at 60 °C for 4 h under nitrogen protection to obtain polyurea (number average molecular weight: 10,000 g / mol); (3) At room temperature, polyurea was added dropwise into 18 kg of water with continuous stirring to obtain a transparent water-soluble polyurea early strength agent (visible light transmittance of 95%).

[0042] In order to evaluate the early strength effect of water-soluble polyurea early strength agent in cement slurry mixing, 300g cement, 50g silica fume, 50g fly ash, 6.5g water-soluble polyurea early strength agent of Example 2, 1.5g water reducer and 87g water were added into the stirring pot of the slurry instrument, and mixed evenly according to the cement slurry test method of GB / T 8077-2012 "Test method for homogeneity of concrete admixtures", and then steam cured to obtain an early strength cement product.

[0043] Example 3 Preparation of water-soluble polyurea early strength agent: (1) 100 g of pre-dried toluene diisocyanate, 60 g of polytetramethylene diamine (number average molecular weight of 250 g / mol) and 0.5 g of triethylene diamine were added into a 1 L enamel reactor equipped with a mechanical stirrer, and stirred and reacted at 80 ° C for 4 h under nitrogen protection to obtain a polyurea prepolymer; (2) 18 g of 2,3-diaminopropionic acid was added as a chain extender to the polyurea prepolymer, and the mixture was stirred and reacted at 80 °C for 2 h under nitrogen protection to obtain polyurea (number average molecular weight 4000 g / mol); (3) At room temperature, polyurea was added dropwise into 8 kg of water with continuous stirring to obtain a transparent water-soluble polyurea early strength agent (visible light transmittance of 90%).

[0044] In order to evaluate the early strength effect of water-soluble polyurea early strength agent in mortar mixing, 450g of cement, 150g of silica fume, 8.5g of the water-soluble polyurea early strength agent of Example 3, 6.0g of water reducer, 150g of water and 2500g of standard sand were added into the stirring pot of the mortar instrument, and mixed evenly according to the cement mortar test method of GB / T 8077-2012 "Test method for homogeneity of concrete admixtures", and then steam cured to obtain an early strength mortar product.

[0045] Example 4 Preparation of water-soluble polyurea early strength agent: (1) 100 g of pre-dried diphenylmethane diisocyanate, 68 g of polyoxyethylene ether diamine (number average molecular weight of 500 g / mol) and 0.5 g of triethylene diamine were added into a 1 L glass reactor equipped with a magnetic stirrer, and stirred and reacted at 80 ° C for 2 h under nitrogen protection to obtain a polyurea prepolymer; (2) 16 g of 2,3-diaminopropionic acid was added as a chain extender to the polyurea prepolymer, and the mixture was stirred and reacted at 80 °C for 3.5 h under nitrogen protection to obtain polyurea (number average molecular weight 8000 g / mol); (3) At room temperature, polyurea was added dropwise into 14.7 kg of water with continuous stirring to obtain a transparent water-soluble polyurea early strength agent (visible light transmittance of 96%).

[0046] In order to evaluate the early strength effect of water-soluble polyurea early strength agent in mortar mixing, 450g of cement, 150g of silica fume, 10.0g of the water-soluble polyurea early strength agent of Example 4, 6.0g of water reducer, 150g of water and 2500g of standard sand were added into the stirring pot of the mortar instrument, and mixed evenly according to the cement mortar test method of GB / T 8077-2012 "Test method for homogeneity of concrete admixtures", and then steam cured to obtain an early strength mortar product.

[0047] Comparative Example 1 Preparation of polyurea emulsion: (1) 100 g of pre-dried 1,6-hexamethylene diisocyanate, 50 g of polycaprolactone diamine (number average molecular weight of 500 g / mol) and 0.05 g of dibutyltin dilaurate were added into a 1 L glass reactor equipped with a magnetic stirrer, and stirred at 70 ° C for 3 h under nitrogen protection to obtain a polyurea prepolymer; (2) 10 g of 1,4-butanediamine was added as a chain extender to the polyurea prepolymer, and the mixture was stirred and reacted at 70 °C for 3 h under nitrogen protection to obtain polyurea (number average molecular weight: 17000 g / mol); (3) At room temperature, polyurea was added dropwise into 0.75 kg of water with continuous stirring to obtain a milky white polyurea solution, i.e., a polyurea emulsion (visible light transmittance of 12%).

[0048] In order to compare and evaluate the early strength effect of water-soluble polyurea early strength agent and the polyurea emulsion of comparative example 1 in concrete mixing, 1500g cement, 1000g fly ash, 1000g silica fume, 8000g sand, 11000g crushed stone, 200g water reducer, 218.8g polyurea emulsion of comparative example 1 and 500g water were added into a concrete mixer, and mixed uniformly according to the relevant method of GB / T 8076-2008 "Concrete Admixtures". The appearance and setting time of the concrete are shown in Table 1. After steam curing for 1d, 3d and 7d, the compressive strength of the concrete test blocks measured are shown in Table 1 and Figure 1 shown.

[0049] Comparative Example 2 Comparative Example 2 uses the commercially available early strength agent triethanolamine.

[0050] In order to compare and evaluate the early strength effect of water-soluble polyurea early strength agent and commercial early strength agent triethanolamine in concrete mixing, 1500g cement, 1000g fly ash, 1000g silica fume, 8000g sand, 11000g crushed stone, 200g water reducer, 35g commercial triethanolamine of comparative example 2 and 683.8g water were added into a concrete mixer, and mixed evenly according to the relevant method of GB / T 8076-2008 "Concrete Admixtures". The appearance and setting time of the concrete are shown in Table 1. After steam curing for 1d, 3d and 7d, the compressive strength of the concrete test blocks is shown in Table 1 and Figure 1 shown.

[0051] Comparative Example 3 To compare and evaluate the early strength of concrete without early strength agent, 1500g cement, 1000g fly ash, 1000g silica fume, 8000g sand, 11000g crushed stone, 200g water reducer and 718.8g water were added into a concrete mixer and mixed evenly according to the relevant methods of GB / T8076-2008 Concrete Admixtures. The appearance and setting time of the concrete are shown in Table 1. After steam curing for 1d, 3d and 7d, the compressive strength of the concrete test blocks was measured as shown in Table 1 and Figure 1 shown.

[0052]

[0053] From Table 1 and Figure 1 It can be seen from the data that compared with the newly mixed concrete, the concrete without early strength agent (Comparative Example 3) has better fluidity, but poor paste encapsulation, severe stone exposure, poor cohesion and water retention; the concrete with the commercially available early strength agent triethanolamine (Comparative Example 2) also has poor encapsulation, severe stone exposure, slightly improved cohesion, but delayed the concrete setting time; the concrete with the addition of polyurea emulsion (Comparative Example 1) has a slightly decreased fluidity, but improved the cohesion of the paste; the concrete with the addition of water-soluble polyurea early strength agent (Example 1) also has a slightly decreased fluidity, but greatly improved the cohesion and water retention of the paste, excellent paste encapsulation, and slightly improved setting time, indicating that the water-soluble polyurea early strength agent has a significant effect on improving the workability of concrete without significantly affecting the setting time of concrete.

[0054] Comparing the concrete cured for 1d, 3d and 7d, the strength of the test block without early strength agent increased slowly, and the addition of triethanolamine can significantly improve the early strength of the test block. Polyurea emulsion also has certain early strength performance, but it is significantly weaker than triethanolamine, while the water-soluble polyurea early strength agent significantly improves the compressive strength of the test block, which is better than triethanolamine, indicating that the water-soluble polyurea early strength agent of the present invention has a significant improvement effect on the early strength improvement of concrete.

[0055] Depend on Figure 2It can be seen that the particle size of Example 1 is 36.5±5.0 nm, the particle size of Example 2 is 44.6±3.5 nm, the particle size of Example 3 is 33.2±10.2 nm, and the particle size of Example 4 is 38.8±7.6 nm.

[0056] Depend on Figure 3 It can be seen that the transmission electron microscopy particle size of Example 1 is 35.0±5.0 nm, which is consistent with the dynamic light scattering result.

[0057] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A method for preparing a water-soluble polyurea early strength agent, characterized in that: The method comprises the following steps: (1) reacting diamino polyether, diisocyanate and catalyst in an anhydrous environment at 60-80°C with continuous stirring until the solution viscosity reaches above 2 Pa·s, stopping the reaction to obtain a polyurea prepolymer; (2) adding a chain extender to a polyurea prepolymer, stirring and reacting at 60-80°C in an anhydrous environment until the solution viscosity reaches above 5 Pa·s, and then stopping the reaction to obtain polyurea; (3) Add polyurea dropwise into water while stirring continuously to obtain a transparent water-soluble polyurea early strength agent.

2. The method for preparing the water-soluble polyurea early strength agent according to claim 1, characterized in that: In step (1), the diamino polyether is at least one of polytetrahydrofuran diamine, polyoxyethylene ether diamine and polyoxypropylene ether diamine, and has a number average molecular weight of 250 to 2000 g / mol; The diisocyanate is at least one of toluene diisocyanate, diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate and isophorone diisocyanate; The catalyst is dibutyltin dilaurate, stannous isooctanoate or triethylenediamine.

3. The method for preparing the water-soluble polyurea early strength agent according to claim 2, characterized in that: In step (1), the number average molecular weight of polytetrahydrofuran diamine is 250-1000 g / mol, and the number average molecular weight of polyoxyethylene ether diamine and polyoxypropylene ether diamine is 500-1500 g / mol.

4. The method for preparing the water-soluble polyurea early strength agent according to claim 1, characterized in that: In step (2), the chain extender contains two amino groups and at least one carboxyl group, and is specifically any one of lysine, diaminopimelic acid or 2,3-diaminopropionic acid.

5. The method for preparing the water-soluble polyurea early strength agent according to claim 1, characterized in that: In step (2), the mass ratio of diisocyanate: diamino polyether: chain extender is 100:50-90:10-20; The mass ratio of diisocyanate: diamino polyether: chain extender: catalyst is 100:50~90:10~20:0.01~1; The number average molecular weight of polyurea is 4000~10000 g / mol.

6. The method for preparing the water-soluble polyurea early strength agent according to claim 1, characterized in that: In step (1) and step (2), the anhydrous environment is an anhydrous and oxygen-free environment, which is achieved by nitrogen or inert gas protection, and the inert gas is argon; In step (1) and step (2), the reaction time is 2 to 4 hours.

7. The method for preparing the water-soluble polyurea early strength agent according to claim 1, characterized in that: In step (3), the mass ratio of polyurea to water is 1:10-100.

8. A water-soluble polyurea early strength agent prepared by the preparation method according to any one of claims 1 to 7, characterized in that: Polyurea is a small-sized micelle below 50nm in water, and the visible light transmittance of water-soluble polyurea early strength agent is ≥90%.

9. Use of the water-soluble polyurea early strength agent according to claim 8 in cement paste, mortar and concrete mixing, characterized in that: The water-soluble polyurea early strength agent is added together with the cementitious material, aggregate, admixture and water.

10. The use according to claim 9, characterized in that: The cementitious material is at least one of cement, fly ash or silica fume; the aggregate is crushed stone and / or sand; the admixture is at least one of a water reducing agent, a retarder, a pumping agent, a waterproofing agent, a thickener, an air entraining agent and an existing early strength agent; The mass of the solute polyurea in the water-soluble polyurea early strength agent accounts for 0.001~0.1% of the mass of the cementitious material.

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