CN113388275A

CN113388275A - Modified lithium-based concrete sealing curing agent and preparation method thereof

Info

Publication number: CN113388275A
Application number: CN202110813447.0A
Authority: CN
Inventors: 潘崇根; 陈娜; 何静姿; 李旭; 臧家伟; 朱大勇; 陈景阳
Original assignee: Zhejiang University of Science and Technology ZUST
Current assignee: Ningbo University of Technology; Zhejiang University of Science and Technology ZUST
Priority date: 2021-07-19
Filing date: 2021-07-19
Publication date: 2021-09-14

Abstract

The invention discloses a modified lithium-based concrete sealing curing agent and a preparation method thereof, and relates to the technical field of building materials, wherein the modified lithium-based concrete sealing curing agent comprises the following raw materials in percentage by mass: 30-50 wt% of liquid lithium silicate, 0-10 wt% of sodium silicate, 0-30 wt% of silica sol, 0.5-2 wt% of surfactant, 0.5-1 wt% of dispersant, 0.5-2 wt% of defoaming agent, 3-15 wt% of fluorosilicate, 0.02-0.3 wt% of graphene oxide and the balance of water, wherein the contents of the sodium silicate and the silica sol are not 0, the prepared sealing curing agent has good comprehensive performance, can effectively improve the structural strength, the wear resistance, the waterproofness and other performances of concrete, and has high commercial and popularization values.

Description

Modified lithium-based concrete sealing curing agent and preparation method thereof

Technical Field

The invention relates to the technical field of building materials, in particular to a modified lithium-based concrete sealing curing agent and a preparation method thereof.

Background

In modern buildings, concrete is a widely used and most used building structural material, is a mixture prepared by mixing a cementing material, granular aggregate, water and chemical additives and mineral admixtures which need to be added according to a proper proportion, and has the advantages of economy, durability, fire resistance, high pressure resistance and the like. Nowadays, with the development of various fields such as highways, bridges, ocean development, tunnel construction and the like towards the direction of complexity, maximization and convenience, the requirements on the service performance of concrete are more and more strict and harsh, in the hardening process of the concrete, because the surface layer and the internal structure of the concrete contain a large number of mutually-penetrated pores, the concrete structure is often difficult to resist the corrosion of corrosive substances in the environment due to poor surface quality or insufficient compactness in the service process, the accelerated deterioration of the performance of the concrete structure is caused, the durability and the service life of the concrete structure are reduced, and especially, the early damage of the concrete structure of some ocean engineering is caused under the condition that the design service life is not reached.

In view of the above circumstances, the surface coating of concrete is currently an effective technical means for improving the durability of concrete, and the surface coating mainly comprises a surface coating and silane impregnation, wherein the former has a relatively complex construction process and poor environmental protection, and the latter has a simple and relatively environmental protection construction process, but has a relatively high price and poor durability, and has relatively few engineering applications.

The lithium base sealing curing agent for concrete is a kind of concrete surface permeable protective material using lithium silicate as main component, it is an alkaline colorless transparent liquid, it is a new terrace material with the characteristics of tastelessness, non-toxicity, non-inflammable and non-volatile, it can permeate to a certain depth of concrete surface layer, and through chemical reaction with free calcium ion, it can strengthen the cementing structure in the cement, reduce the pores of concrete surface layer, and increase the compactness of concrete surface layer, so that it can greatly raise the surface hardness and strength of concrete, and can increase the wear resistance of concrete surface, so that it can obtain dustless and compact concrete floor, and can raise the durability of concrete, and can prolong the service life of concrete.

However, the performance and preparation process of the common lithium-based sealing curing agent on the market still have certain problems, after the curing agent is used, the strength and waterproof performance of the concrete surface are still general and are easy to corrode, and at present, in the aspect of selecting and matching of various raw materials, how to determine an optimal proportion can enable the performance of the curing agent to reach a relatively excellent level, and how to prepare the sealing curing agent with good substrate strength and water absorption performance is a technical problem which is difficult to solve in the industry at present.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the modified lithium-based concrete sealing curing agent can ensure that the concrete has high surface hardness, good wear resistance, good waterproofness and high structural strength after being used, and can play the effects of protection, corrosion resistance and carbonization resistance on the surface of the concrete so as to solve the conventional problems at present.

In order to achieve the purpose, the invention provides the following scheme:

the first technical scheme is as follows:

the invention provides a modified lithium-based concrete sealing curing agent which comprises the following raw materials in percentage by mass: 30-50 wt% of liquid lithium silicate, 0-10 wt% of sodium silicate, 0-30 wt% of silica sol, 0.5-2 wt% of surfactant, 0.5-1 wt% of dispersant, 0.5-2 wt% of defoaming agent, 3-15 wt% of fluorosilicate, 0.02-0.3 wt% of graphene oxide and the balance of water, wherein the content of sodium silicate and silica sol is not 0.

The modified lithium-based concrete sealing curing agent can well permeate into concrete and react with the concrete to form insoluble calcium silicate hydrate, the treated concrete surface can prevent water and chemical substances from corroding the concrete surface, and the wear resistance can be obviously enhanced. The surface of the concrete coated with the modified lithium-based concrete sealing curing agent also has the performances of dust prevention, easy cleaning, easy maintenance, environmental protection and the like.

The addition of the graphene oxide greatly changes the microstructure of the concrete crystal, and in the formation process of a cement hydration product, the graphene oxide promotes the hydration product to form regular and orderly flower-shaped crystals, so that the compactness of the internal structure is increased, the shrinkage and cracks can be eliminated, the concrete cannot be weathered, the strength of the concrete is improved, the water in the concrete is delayed from being diffused outwards, and the concrete can be protected; since the structure of the concrete is chemically changed to be more compact, the generation of dust can be eliminated, and the surface of the concrete is prevented from being dented and recessed, thereby substantially reducing maintenance costs. Meanwhile, the large specific surface area of the graphene oxide can also increase the strength of concrete, and the formation of the nano-scale C-S-H improves the bonding strength of the concrete and hinders the formation of microcracks, so that the compressive strength and the flexural strength of the cement-based composite material are improved.

Further, the surfactant is one of sodium stearate, sodium dodecyl benzene sulfonate or sodium dodecyl sulfate. The surfactant has the effects of reducing the interfacial free energy of a two-phase interface in a dispersion system and improving the stability of the dispersion system; the sodium dodecyl benzene sulfonate is an anionic surfactant, has stable chemical properties on alkali, dilute acid and hard water, has good surface activity and stronger hydrophilicity, and effectively reduces the tension of an oil-water interface.

Furthermore, the dispersing agent is polyethylene glycol, is an auxiliary agent capable of improving the dispersibility of the liquid material, enhances the stability of the solution, and also has the function of a surfactant.

Further, the fluosilicate is MgSiF₆Or CaSiF₆。

SiF in fluorosilicates₆ ^2-In the presence of Ca (OH)₂Hydrolyzing in an alkaline environment to exchange F^-Are each separately reacted with Mg²⁺And Ca²⁺Bonding ofTo MgF₂And CaF₂And precipitate out MgF₂Is a tetragonal crystal or powder, is odorless, insoluble in water and alcohol, slightly soluble in dilute acid, and soluble in nitric acid. CaF₂The crystal belongs to an isometric crystal system and is cubic, octahedral or dodecahedral. Fluorosilicates with Ca (OH)₂Insoluble matter (MgF) formed₂And CaF₂And C-S-H gel) is filled in the gaps of the concrete, so that the concrete is more compact, the strengthening effect is achieved, and Ca (OH) is blocked₂The channel migrates to the surface and consumes Ca (OH) generated by hydration₂And simultaneously solves the puzzlement of whitening the surface of the concrete material. Si (OH) formed by the reaction₆ ^2-Conversion in water to Si (OH)₄Namely, ortho-silicic acid which is a polyhydroxy small molecule and is a substance with good water solubility, is converted into polysilicic acid in water to form a network structure which can be written as nSiO₂·yH₂In the form of O, a common silica gel. The active silicon oxide can further react with cement hydration product calcium hydroxide in concrete to form C-S-H gel, and capillary pores are further filled. The secondary reaction product of the fluosilicate and the cement hydration product has a positive effect on the enhancement of the concrete strength, a large amount of alkali substances are consumed, the alkalinity of the concrete can be effectively reduced after the reaction, more fibrous and reticular space structures are generated, microscopic gaps are effectively filled, and a certain enhancement effect can be achieved.

Further, the defoaming agent is an organic silicon defoaming agent or a mineral oil defoaming agent, and the defoaming agent eliminates foams formed by materials in the production process; the organic silicon defoaming agent can be used in a water system and an oil system, and has small surface tension and higher thermal stability and chemical stability.

Further, the silica sol is alkaline silica sol or neutral silica sol, the silica sol is a dispersion of nano-scale silica particles in water or a solvent, the average particle size of the neutral silica sol is 8-15 nm, and the average particle size of the alkaline silica sol is 10-20 nm. The preferred silica sol is alkaline silica sol, and the nano-scale particle size and the sol form ensure that the silica sol has good dispersibility and viscosity, and has the functions of resisting dirt, preventing dust, resisting aging, preventing fire and the like when being used in a coating; the pH value of the alkaline silica sol is closer to that of the lithium silicate solution, and the compatibility is better.

Furthermore, the thickness of the graphene oxide sheet layer is 0.5-2 nm, and the sheet diameter is 0.5-8 μm.

The second technical scheme is as follows:

the invention provides a preparation method of a modified lithium-based concrete sealing curing agent, which comprises the following steps:

(1) accurately weighing each raw material;

(2) mixing liquid lithium silicate, sodium silicate, fluorosilicate and graphene oxide, heating and stirring, and cooling to room temperature to obtain a stirred mixed solution;

(3) adding a surfactant into the mixed solution stirred in the step (2), and continuously stirring until the solution is clear;

(4) adding a dispersing agent, a defoaming agent and water, continuously stirring, standing to obtain a mixed solution, continuously adding silica sol into the mixed solution, stirring and standing to obtain the modified lithium-based concrete sealing curing agent.

Further, the heating temperature in the step (2) is 50-70 ℃, and the stirring time is 50-70 min.

Further, the stirring time in the step (4) is 2-3 h.

Further, in the step (4), the first standing time is 10-14 hours, and the second standing time is 20-25 hours.

The invention discloses the following technical effects:

the modified lithium-based concrete sealing curing agent provided by the invention takes lithium silicate as a main component, is matched with a small amount of sodium silicate, fluosilicate and graphene oxide, takes nano-silica sol as an auxiliary component, and is matched with a high-performance surfactant, a dispersing agent and an antifoaming agent. After the curing agent is coated on the surface of concrete, silicate components in the curing agent can enter the concrete and react with free calcium ions on the surface layer of the concrete to generate calcium silicate hydrate gel, sodium silicate has good film-forming property, a layer of compact protective film can be formed on the surface of the concrete, lithium silicate has smaller molecular size and stronger permeability, the microstructure of a concrete crystal is greatly changed by adding graphene oxide, the compactness of an internal structure is increased, the formation of microcracks is hindered, the concrete can be more compact by adding fluorosilicate, the reinforcing effect is achieved, therefore, the concrete sealing curing agent taking lithium silicate as a main component has larger penetration depth, a protective layer on the surface of the concrete is more uniformly formed within the penetration depth range, the surface hardness and the wear resistance of the concrete can be improved, and the phenomenon that the surface layer concrete forms filamentous cracks too fast is avoided to a great extent, the porosity of the surface concrete is reduced, and the effect of reducing the water absorption of the concrete is further achieved. The nano silica sol component is added, so that the surface brightness of the concrete coated with the curing agent is higher, the anti-fouling and dustproof effects are better, the ground cleaning work is simpler, the terrace durability after the curing agent is acted is good, the maintenance cost is low, and the modified lithium-based concrete sealing curing agent provided by the invention is non-toxic, colorless, tasteless, free of volatile gas, simple and convenient to construct, and quick in film forming time, and can be constructed while producing.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.

FIG. 1 is an electron microscope image of the surface micro-topography of a blank set cement;

FIG. 2 is an electron microscope image of the surface micro-topography of a set cement after coating the modified lithium-based concrete sealing curing agent of example 4;

FIG. 3 is an electron microscope image of the surface micro-topography of a set cement after coating the modified lithium-based concrete sealing curing agent of example 5;

FIG. 4 is an electron microscope image of the surface micro-topography of a set cement after coating the modified lithium-based concrete sealing curing agent of example 6;

FIG. 5 is an electron microscope image of the surface micro-topography of the set cement after coating the modified lithium-based concrete sealing curing agent of example 7.

Detailed Description

Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The description and examples are intended to be illustrative only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.

The embodiments of the present invention relate to various raw materials, including but not limited to lithium silicate, sodium dodecylbenzene sulfonate, silicone defoamer, polyethylene glycol, alkaline silica sol, fluorosilicate, graphene oxide, and the like, which are commercially available.

Example 1

The modified lithium-based concrete sealing curing agent is prepared from the following raw materials in percentage by mass: 30 wt% of liquid lithium silicate, 1 wt% of sodium silicate, 0.5 wt% of neutral silica sol (average particle size of 15nm) surfactant, 0.5 wt% of dispersant, 0.5 wt% of defoaming agent, 5 wt% of fluorosilicate, 0.05 wt% of graphene oxide and the balance of deionized water; in the embodiment, the surfactant is sodium stearate, the dispersing agent is polyethylene glycol PEG200, the defoaming agent is a food-grade organic silicon defoaming agent, and the fluorosilicate is MgSiF₆The thickness of the graphene oxide sheet layer is 0.5nm, and the sheet diameter is 7 μm.

The preparation method of the modified lithium-based concrete sealing curing agent of the embodiment comprises the following preparation steps:

(1) accurately weighing each raw material;

(2) mixing liquid lithium silicate, sodium silicate, fluorosilicate and graphene oxide, stirring at 60 ℃ for 60min, and cooling to room temperature to obtain a stirred mixed solution;

(4) adding a dispersing agent, a defoaming agent and water, continuously stirring for 2 hours, standing for 12 hours to obtain a mixed solution, continuously adding silica sol into the mixed solution, stirring, and standing for 24 hours to obtain the modified lithium-based concrete sealing curing agent.

Example 2

The modified lithium-based concrete sealing curing agent is prepared from the following raw materials in percentage by mass: 40 wt% of liquid lithium silicate, 5 wt% of sodium silicate, 30 wt% of alkaline silica sol (average particle size is 15nm), 1.25 wt% of surfactant, 0.75 wt% of dispersant, 1.25 wt% of defoaming agent, 3 wt% of fluorosilicate, 0.02 wt% of graphene oxide and the balance of deionized water; in this example, the surfactant was sodium lauryl sulfate, the dispersant was polyethylene glycol PEG200, and the defoamer was food grade siliconeDefoaming agent, wherein the fluosilicate is MgSiF₆The thickness of the graphene oxide sheet layer is 2nm, and the sheet diameter is 8 μm.

The preparation method of the modified lithium-based concrete sealing curing agent of the embodiment is the same as that of the embodiment 1.

Example 3

The modified lithium-based concrete sealing curing agent is prepared from the following raw materials in percentage by mass: 50 wt% of liquid lithium silicate, 8 wt% of sodium silicate, 20 wt% of alkaline silica sol (average particle size is 15nm), 2 wt% of surfactant, 1 wt% of dispersant, 2 wt% of defoaming agent, 10 wt% of fluorosilicate, 0.02 wt% of graphene oxide and the balance of deionized water; in this example, the surfactant was sodium dodecylbenzenesulfonate, the dispersant was polyethylene glycol PEG200, the defoamer was a food grade silicone defoamer, and the fluorosilicate was CaSiF₆The thickness of the graphene oxide sheet layer is 0.8nm, and the sheet diameter is 6 μm.

Example 4

The modified lithium-based concrete sealing curing agent is prepared from the following raw materials in percentage by mass: 35 wt% of liquid lithium silicate, 2 wt% of sodium silicate, 1 wt% of alkaline silica sol (average diameter is 20nm) surfactant, 1 wt% of dispersant, 2 wt% of defoaming agent, 15 wt% of fluorosilicate, 0.3 wt% of graphene oxide and the balance of deionized water; the surfactant is sodium dodecyl benzene sulfonate, the dispersant is polyethylene glycol PEG200, the defoaming agent is a food-grade organic silicon defoaming agent, and the fluosilicate is MgSiF₆The thickness of the graphene oxide sheet layer is 1.5nm, and the sheet diameter is 0.5 μm.

The preparation method of the modified lithium-based concrete sealing curing agent comprises the following steps:

(1) accurately weighing each raw material;

(2) mixing liquid lithium silicate, sodium silicate, fluorosilicate and graphene oxide, stirring at 70 ℃ for 50min, and cooling to room temperature to obtain a stirred mixed solution;

(4) adding a dispersing agent, a defoaming agent and water, continuously stirring for 3 hours, standing for 12 hours to obtain a mixed solution, continuously adding silica sol into the mixed solution, stirring, and standing for 20 hours to obtain the modified lithium-based concrete sealing curing agent.

Example 5

The modified lithium-based concrete sealing curing agent is prepared from the following raw materials in percentage by mass: 30 wt% of liquid lithium silicate, 5 wt% of sodium silicate, 1 wt% of alkaline silica sol (average diameter is 10nm) surfactant, 1 wt% of dispersant, 2 wt% of defoaming agent, 5 wt% of fluorosilicate, 0.2 wt% of graphene oxide and the balance of deionized water; in the embodiment, the surfactant is sodium dodecyl benzene sulfonate, the dispersant is polyethylene glycol PEG200, the defoaming agent is a food-grade organic silicon defoaming agent, and the fluosilicate is MgSiF₆The thickness of the graphene oxide sheet layer is 0.8nm, and the sheet diameter is 6 μm.

The preparation method of the modified lithium-based concrete sealing curing agent is the same as that of example 4.

Example 6

The modified lithium-based concrete sealing curing agent is prepared from the following raw materials in percentage by mass: 45 wt% of liquid lithium silicate, 2 wt% of sodium silicate, 20 wt% of alkaline silica sol, 1 wt% of surfactant, 0.8 wt% of dispersant, 1.5 wt% of defoaming agent, 6 wt% of fluorosilicate, 0.2 wt% of graphene oxide and the balance of deionized water; in the embodiment, the surfactant is sodium dodecyl benzene sulfonate, the dispersant is polyethylene glycol PEG200, the defoaming agent is a food-grade organic silicon defoaming agent, and the fluosilicate is MgSiF₆The thickness of the graphene oxide sheet layer is 1.5nm, and the sheet diameter is 0.8 μm.

The preparation method of the modified lithium-based concrete sealing curing agent of the embodiment is the same as that of the embodiment 4.

Example 7

The modified lithium-based concrete sealing curing agent is prepared from the following raw materials in percentage by mass: 35 wt% of liquid lithium silicate, 8 wt% of sodium silicate, 30 wt% of alkaline silica sol (average particle size of 15nm), 0.5 wt% of surfactant, 0.5 wt% of dispersant, 2 wt% of defoaming agent, 12 wt% of fluorosilicate, 0.15 wt% of graphene oxide, and deionized waterThe balance of water; in the embodiment, the surfactant is sodium dodecyl benzene sulfonate, the dispersant is polyethylene glycol PEG200, the defoaming agent is a food-grade organic silicon defoaming agent, and the fluosilicate is MgSiF₆The thickness of the graphene oxide sheet layer is 1.5nm, and the sheet diameter is 5 μm.

The preparation method of the modified lithium-based concrete sealing curing agent of the embodiment comprises the following steps:

(1) accurately weighing each raw material;

(2) mixing liquid lithium silicate, sodium silicate, fluorosilicate and graphene oxide, stirring at 60 ℃ for 70min, and continuously stirring and cooling to room temperature to obtain a stirred mixed solution;

(3) adding a surfactant into the mixed solution, and continuously stirring until the solution is uniform and clear;

(4) adding a dispersing agent, a defoaming agent and deionized water, continuously stirring for 2.5 hours, and standing for 10 hours to obtain a colorless transparent solution; adding silica sol into the colorless and transparent solution, continuously stirring until the solution is homogenized and clarified, and standing for 24 hours to obtain the modified lithium-based concrete sealing curing agent.

Comparative example 1

The same as example 7 except that the fluorosilicate and graphene oxide were not added.

Comparative example 2

The same as example 7 except that no fluorosilicate was added.

Comparative example 3

The difference from example 5 is only that no graphene oxide was added.

According to the requirements of the concrete surface protection and durability improvement, the tests of mechanical property, permeability, carbonization resistance and the like are carried out after the modified lithium-based concrete sealing curing agent is coated on the concrete. The results show that: the modified lithium-based sealing curing agent has certain influence on the strength of concrete, and greatly improves the permeability, including water permeability, chloride ion permeability and concrete carbonization resistance, and experimental results show that after the lithium-based modified concrete sealing curing agent is coated, the porosity of a concrete surface layer is reduced, the compactness of the concrete surface layer is increased, and a surface layer film capable of effectively preventing external factors from being corroded is formed on the concrete surface.

Firstly, testing mechanical properties

The modified lithium-based modified sealing curing agent is coated on cement mortar test blocks of 40mm × 40mm × 160mm in different curing ages according to the formula of the embodiment 4-7, and compared with untreated cement mortar test blocks, the compressive strength test is carried out according to GB/T17671-1999 Cement mortar Strength test method (ISO method), the surface hardness is measured by a Mohs hardness tester, and the results are shown in tables 1 and 2.

TABLE 1 mortar strength (MPa) after applying curing agent at different curing ages

TABLE 2 Mohs hardness of mortar surface after coating lithium-based sealing curing agent

Test piece	Hardness before painting	Hardness after painting
			Blank test block	5.5	5.5
Example 4	5-5.5	6.5
			Example 5	5-5.5	6.5
Example 6	5-5.5	7
			Example 7	5-5.5	7
Comparative example 3	5.5	5.8

1. Compressive strength

The blank test block 28d has a compressive strength of 42.96Mpa, and all test blocks coated with the sealing curing agent have 28d compressive strengths tested at the age of 28d, and the results show that the coating of the sealing curing agent at the age of 7d has no influence on the strength of the cement mortar test block, the coating of the sealing curing agent at the ages of 14d, 21d and 28d has an effect of improving the strength of the cement mortar test block, and the coating at the age of 21d can obtain the maximum compressive strength, which is respectively improved by 7%, 5.7%, 12.1% and 12.7% compared with the blank test blocks in examples 1-4 after the coating of the cement mortar test block at the age of 21 d.

2. Hardness of

The result shows that the hardness of the cement mortar test block is improved from 5.5 to 6.5-7 and the maximum hardness can reach 7 by brushing the modified lithium-based concrete sealing curing agent.

Permeability and permeability

The permeability test comprises the water absorption and the chlorine ion permeability resistance of a cement mortar test block, the water absorption is carried out according to JGJ/T70-2009 Standard for basic Performance test method of building mortar, a sealing curing agent is coated on six surfaces of the test block at the age of 21d, a 48-hour water absorption test of the mortar is carried out at the age of 28d, and the result is calculated according to the following formula:

in the formula: w_xWater absorption (%) of the mortar; m is₁The mass (g) of the test piece after water absorption; m is₀The dry specimen mass (g).

A method for measuring the penetration depth of free chlorine ions in mortar by a silver nitrate detection method in a chlorine ion penetration experiment includes the steps of coating a sealing curing agent on the back surface of a molding surface of cement mortar when the cement mortar test block is aged 21d, keeping the coated surface as a penetration surface of the chlorine ion penetration experiment, sealing the rest surfaces by an epoxy resin sealing adhesive when the cement mortar test block is aged 27d, soaking the test block in a NaCl solution with the mass concentration of 3% when the cement mortar test block is aged 28d, taking out and disconnecting the test block after the test block is soaked for 3d, 7d, 14d, 21d and 28d respectively, and spraying 0.1mol/L AgNO on a port interface₃The solution measures the depth of penetration of free chloride ions in the mortar. The water absorption and chloride ion permeability of the blank test block are shown in tables 3 and 4 in comparison with examples 4 to 7.

TABLE 3 Cement mortar test block 48h water absorption rate after brushing sealing curing agent

Test specimen	Blank test block	Example 4	Example 5	Example 6	Example 7	Comparative example 1
							Water absorption (%)	7.87	5.82	5.22	5.02	4.82	7.24

TABLE 4 mortar test block penetration depth (mm) after applying sealing curing agent

The experimental result shows that the permeability of cement mortar can be effectively improved by brushing the lithium-based sealing curing agent, the water absorption of a cement mortar test block after 48 hours can be reduced by 26.1-38.8% by brushing the four sealing curing agents, and the penetration depth of chloride ions of 28d can be reduced by 21.5-44.2%.

Third, anti-carbonization property

The accelerated carbonation test is carried out according to a carbonation test method in GB/T50082-2009 test method for long-term performance and durability of ordinary concrete, the back surface of the molded surface coated in examples 1-4 is used as a carbonation surface when a test piece is in a 21d maintenance age, the other five surfaces are sealed by epoxy resin glue, and a test piece in a 28d age is placed in a carbonation box, and the carbonation surface is ensured to be uniformly upward. The samples were carbonized for 3, 7, 14, 21, and 28d, taken out and cut off as needed, and the carbonization depth was measured with a colorless phenolphthalein reagent, and the results of the carbonization test are shown in table 5.

TABLE 5 mortar test block carbonization depth after coating sealing curing agent

As shown in Table 5, the anti-carbonization capability of the mortar is improved to a certain extent by brushing the sealing curing agent of the four examples, and the 28d carbonization depth of the mortar can be reduced by about 20.6-30.4% after brushing in the examples 1-4.

Scanning test of electron microscope

Scanning electron microscope tests mainly represent the change of the surface micro-morphology of the cement coated with the sealing curing agent, in the experimental process, a tool is taken down to perform electron microscope scanning on the block on the surface of the cement coated with the sealing curing agent, and the electron microscope images of the surface micro-morphology of the blank cement and the cement coated in the embodiments 4 to 7 are shown in the figures 1 to 5.

According to the graphs 1-5, the surface of the blank sample is compared with the sample processed by the curing agent, a large number of pores exist on the surface of the blank sample, the surface of the blank sample is uneven, and large pores are formed among crystals, but the fillers (C-S-H gel) among the sealed curing agent processed cemented stone crystals are obviously increased, the edge angles of the crystals become more rounded, for example, the flatness of the surface of the cemented stone processed by the seventh embodiment is greatly increased, and a plurality of crystals are connected into a whole to fill the pores of the cement gel, so that the surface porosity is reduced, the compactness is enhanced, and the flatness is increased, and the invention also further illustrates that the integral performance of the curing agent is greatly improved after silica sol, graphene oxide and fluosilicate are added.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.

Claims

1. The modified lithium-based concrete sealing curing agent is characterized by comprising the following raw materials in percentage by mass: 30-50 wt% of liquid lithium silicate, 0-10 wt% of sodium silicate, 0-30 wt% of silica sol, 0.5-2 wt% of surfactant, 0.5-1 wt% of dispersant, 0.5-2 wt% of defoaming agent, 3-15 wt% of fluorosilicate, 0.02-0.3 wt% of graphene oxide and the balance of water, wherein the content of sodium silicate and silica sol is not 0.

2. The modified lithium-based concrete sealing and curing agent as claimed in claim 1, wherein the surfactant is one of sodium stearate, sodium dodecylbenzene sulfonate or sodium dodecylsulfate.

3. The modified lithium-based concrete sealing and curing agent as claimed in claim 1, wherein the dispersant is polyethylene glycol.

4. The modified lithium-based concrete sealing curing agent as claimed in claim 1, wherein the defoaming agent is a silicone defoaming agent or a mineral oil defoaming agent.

5. The modified lithium-based concrete sealing curing agent as claimed in claim 1, wherein the silica sol is an alkaline silica sol or a neutral silica sol.

6. The modified lithium-based concrete sealing curing agent as claimed in claim 1, wherein the graphene oxide has a lamella thickness of 0.5-2 nm and a lamella diameter of 0.5-8 μm.

7. The preparation method of the modified lithium-based concrete sealing and curing agent as claimed in any one of claims 1 to 6, characterized by comprising the following steps:

(1) accurately weighing each raw material;

8. The preparation method according to claim 7, wherein the heating temperature in the step (2) is 50 to 70 ℃ and the stirring time is 50 to 70 min.

9. The preparation method according to claim 7, wherein the stirring time in the step (4) is 2-3 h.

10. The preparation method according to claim 7, wherein the first standing time in the step (4) is 10-14 h, and the second standing time is 20-25 h.