CN114685734A - Polymer-based nano-composite early strength agent and preparation method and application thereof - Google Patents
Polymer-based nano-composite early strength agent and preparation method and application thereof Download PDFInfo
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Abstract
The invention provides a polymer-based nano-composite early strength agent, a preparation method thereof and application thereof in cement-based materials. The composite early strength agent comprises a copolymer obtained by copolymerization of a cation unit A, a carboxylic acid/nano-silica unit B, a polyether unit C and a modified alcohol amine unit D. The composite early strength agent utilizes the structural characteristics thereof, improves the dispersibility of nano silicon dioxide through the charge adsorption dispersion effect, obviously improves the activity release of the nano silicon dioxide, and fully exerts the activity of the nano silicon dioxide through the grafting of the nano silicon dioxide on the molecular chain of the composite early strength agent through Si-O chemical bonds; through TPEG long chain formation steric hindrance, further promote compound early strength agent to the dispersion ability of cement granule, through the complex reaction in addition, the hydration process is accelerated, when finally having guaranteed that it is applied to cement-based material, can promote cement-based material early strength and show the increase.
Description
Technical Field
The invention belongs to the technical field of concrete admixtures, and particularly relates to a polymer-based nano-composite early strength agent, a preparation method thereof and application of the early strength agent in cement-based materials.
Background
In recent years, cement-based materials represented by concrete have become a class of building materials which are widely applied in infrastructure construction and key engineering construction of China, and play an important role in national economic growth and social progress. Meanwhile, with the development of economic level and scientific technology, a new building industry mode, namely an assembly type building, is produced. The demand of the fabricated building on the concrete prefabricated part is increased sharply, but due to the reasons of actual production of the admixture, low production temperature in winter and the like, the early strength of the cement-based material is developed slowly, measures such as steam curing and the like are usually adopted to improve the early strength of the cement-based material at present, but a large amount of energy resources are consumed in the mode, so that the production cost is improved, and the environment is greatly influenced. Based on the development trend of green, efficient and environment-friendly, various inorganic salt early strength agents or alcohol amine organic early strength agents are added into cement-based materials under natural curing process conditions, but the single early strength agent has the problems of reduced later performance strength, doping amount sensitivity and the like.
The nano material is a novel superfine solid material which is rapidly developed in the last 20 years, and the specific small-size effect, the surface and interface effect, the quantum size effect and the like of the nano material provide a new direction and thought for the development of concrete admixtures. The nano silicon dioxide has the characteristics of excellent thixotropy, thickening property, reinforcing property and the like, and is widely applied in the industrial field. Based on the excellent performance of the nano-silica, scholars at home and abroad explore and research the cement-based material containing the nano-silica to different degrees. At present, the existing literature shows that the nano-silica is introduced into the cement-based material, and based on the nano-crystal nucleus effect, the micro-aggregate effect and the pozzolanic activity of the nano-silica, the nano-silica can promote the generation of hydrated calcium silicate, generate more hydration products, compact the three-dimensional structure of the hydration products and the like, and improve the early strength of the cement-based material.
The nanometer effect of the nanometer silicon dioxide depends on the dispersibility of the nanometer silicon dioxide to a great extent, but the nanometer silicon dioxide is difficult to be uniformly dispersed in cement slurry due to the characteristics of high surface energy and the like, and the agglomeration phenomenon is easy to form, so that the application effect of the nanometer silicon dioxide is greatly reduced under the current situations. Therefore, the development of a suitable dispersant to solve the problem of dispersion stability of nano-silica is a prerequisite for the application of nano-silica.
Although there are many reports about modified nano-silica at present, such as an additive for improving the flexural strength and tensile strength of a cement-based material and a preparation method thereof, a hybrid additive (silica is a shell layer) with a core-shell structure and a preparation method thereof are disclosed, the additive can greatly improve the flexural strength and tensile strength of the cement-based material, but the process is complex and the conditions are harsh, which causes certain limitations on the wide application thereof; the admixture can reduce the electric flux of the concrete, improve the chloride corrosion resistance of the concrete, but has no obvious effect of improving the early strength of the concrete; in order to grow calcium silicate hydrate nanogel on the surface of the nano-silica by means of the seed crystal effect of the nano-silica, the titration process of the method is complex, and the stability of the titration process to the solution is not described. In summary, the modification of nano-silica is mostly carried out by chemically modifying nano-silica with a surfactant, and it can be seen that the working performance and stability of the existing additive doped with nano-silica are one of the difficulties solved in various patents.
Therefore, the method for improving the dispersibility of the nano-silica is provided, so that the nano-silica can fully exert the nano effect to improve the early strength of the cement-based material, and has important significance for the development of the cement-based material.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a polymer-based nano composite early strength agent with a completely new structure, which utilizes the structural characteristics of the compound early strength agent, improves the dispersibility of nano silicon dioxide by the charge adsorption dispersion effect, obviously improves the activity release of the nano silicon dioxide, and fully exerts the activity of the nano silicon dioxide by grafting the nano silicon dioxide on the molecular chain of the compound early strength agent through Si-O chemical bonds; through TPEG long chain formation steric hindrance, further promote this compound early strength agent to the dispersion ability of cement granule, through the complex reaction in addition, hydration process is accelerated, when finally having guaranteed that it is applied to cement-based material, can promote cement-based material early strength and show the increase.
In order to achieve the purpose of the invention, the invention adopts the following technical scheme:
a polymer-based nano-composite early strength agent comprises a copolymer obtained by copolymerization of a cation unit A, a carboxylic acid/nano-silica unit B, a polyether unit C and a modified alcohol amine unit D; the structural formulas of the cation unit A, the carboxylic acid/nano-silica unit B, the polyether unit C and the modified alcohol amine unit D are respectively as follows:
cation unit A:
carboxylic acid/nanosilica units B:
polyether unit C:
modified alcohol amine unit D:
in the above structural formula, R1And R2Are selected from any one of H or methyl; and n is an integer of 45-95.
Further, in the structural formula of the copolymer, the ratio of the average repeating unit numbers a, B, C and D of the cation unit A, the carboxylic acid/nano-silica unit B, the polyether unit C and the modified alcohol amine unit D is 1: 3-7: 1: 1; wherein the weight average molecular weight of the copolymer is 20000-70000, and the polymer dispersion index is not more than 2.
Further, the carboxylic acid/nano-silica unit B is obtained by esterification reaction of acrylic acid or methacrylic acid and nano-silica; the modified alcohol amine unit D is obtained by amidation reaction of maleic anhydride and triethanolamine.
Another object of the present invention is to provide a method for preparing the polymer-based nanocomposite early strength agent, which comprises the steps of:
s1, preparing to obtain a nano silicon dioxide aqueous solution;
s2, blending the nano silicon dioxide aqueous solution, a cation unit A, acrylic acid or methacrylic acid, a polyether unit C, a modified alcohol amine unit D, an oxidant and a thiol chain transfer agent in a water system, carrying out a free radical copolymer reaction at 30-60 ℃, and grafting the nano silicon dioxide on acrylic acid or methacrylic acid through an esterification reaction to form a carboxylic acid/nano silicon dioxide unit B; copolymerizing the cation unit A, the carboxylic acid/nano silicon dioxide unit B, the polyether unit C and the modified alcohol amine unit D to obtain a copolymer, thereby obtaining the polymer-based nano composite early strength agent;
wherein the mass ratio of the cationic unit A, the acrylic acid or the methacrylic acid, the polyether unit C and the modified alcohol amine unit D is 1: 3-7: 1: 1; the mass of the nano silicon dioxide in the nano silicon dioxide aqueous solution is 5-30% of that of the acrylic acid or the methacrylic acid; the amount of the oxidant is 0.2-2% of the total amount of the cation unit A, the acrylic acid or the methacrylic acid, the polyether unit C and the modified alcohol amine unit D, and the amount of the thiol chain transfer agent is 1-6% of the total amount of the cation unit A, the acrylic acid or the methacrylic acid, the polyether unit C and the modified alcohol amine unit D.
Further, in the step S2, the polymerization concentration is 30% to 60%.
The oxidant is selected from one of persulfate, water-soluble azo compounds and peroxide, and the thiol chain transfer agent is selected from one of mercaptopropionic acid, thioglycolic acid, mercaptoethanol, mercaptoethylamine and dodecanethiol.
Further, in the step S1, the solid mass fraction of the nano-silica aqueous solution is 30%, wherein the purity of the nano-silica is not lower than 98%, and the average particle size is 20nm to 150 nm.
In the selection of the particle size of the nano silicon dioxide, the spontaneous agglomeration is difficult to inhibit due to too high activity of the excessively small particle size, which is not beneficial to the grafting reaction; and if the particle size is too large, the activity is too low, so that the working performance of the obtained polymer-based nano composite early strength agent as an additive is influenced. Among them, the nano-silica refers to nano-scale silica in various state forms prepared by various known commercial methods.
Another objective of the present invention is to provide an application of the polymer-based nano-composite early strength agent in cement-based materials, wherein the polymer-based nano-composite early strength agent is mixed with cement-based materials and stirred; wherein the folding and fixing mixing amount of the polymer-based nano-composite early strength agent is 0.2-0.3% of the dosage of the cementing material in the cement-based material raw material.
According to the invention, the structural unit A with positive charges is used for adsorbing a large amount of nano silicon dioxide, so that the dispersibility of the nano silicon dioxide is improved, and the activity is further improved. Secondly, because the surface of the nano silicon dioxide contains a large number of silicon hydroxyl groups, the silicon hydroxyl groups have higher activity in aqueous solution, carboxyl groups can be condensed with part of the nano silicon dioxide in an alkaline environment, and the nano silicon dioxide is grafted through Si-O chemical bonds to form a carboxylic acid/nano silicon dioxide unit B; moreover, due to the introduction of the nano silicon dioxide, on one hand, the molecular chain growth of the composite early strength agent can be influenced to a certain extent, and the relative molecular weight is increased, so that the steric hindrance effect of the composite early strength agent molecules on cement particles when the composite early strength agent molecules are applied to a cement-based material is improved, and the dispersing capacity of the early strength agent on the cement particles is improved; on the other hand, the graft structure of the nano-silica can also improve the dispersibility of nano-silica particles, thereby fully exerting the nano-crystal nucleus effect, the micro-aggregate effect and the pozzolanic activity in the cement-based material. Meanwhile, in the compound early strength agent molecule, the N atom on the modified alcohol amine unit D is utilized, and the unshared electron pair on the atom can be in contact with Ca2+And Fe3+The plasma forms a complex which is easy to dissolve in water, promotes the dissolution of tricalcium aluminate and tetracalcium aluminoferrite, accelerates the reaction of the tricalcium aluminate and the tetracalcium aluminoferrite with gypsum to generate ettringite, and promotes the early strength of the cement-based materialThe growth is remarkable; secondly, TPEG long chains in the polyether unit C are mutually soluble with water but have low surface affinity, and the TPEG long chains are mutually soluble with water and extend in a medium to form steric hindrance and form a thick enough adsorption layer, so that the nano silicon dioxide is difficult to agglomerate, and the stability and the dispersibility of the nano silicon dioxide are further improved.
Detailed Description
Hereinafter, embodiments of the present invention will be described in detail. This invention may, however, be embodied in many different forms and should not be construed as limited to the specific embodiments set forth herein. Rather, these embodiments are provided to explain the principles of the invention and its practical application to thereby enable others skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use contemplated.
The existing common early strength agents mainly comprise calcium salt type, organic-inorganic composite type, high-valence cation type and the like, and the action mechanism of the existing early strength agents, whether inorganic early strength agents or organic early strength agents, is to reduce the surface tension of cement clinker particles in contact with water and increase the solubility of the cement clinker particles in the water, and simultaneously, the concentration of cement hydrolysate in the water is reduced through the added early strength agents, so that C is promoted3S、C2S、C3A、C4The dissolution speed of cement components such as AF and the like is improved, the generation of hydration products such as ettringite, C-S-H gel and the like is accelerated, and the coagulation and hardening of the cement are accelerated. The invention provides a polymer-based nano composite early strength agent which is only a single organic-inorganic hybrid material and is not a common organic-inorganic composite early strength agent (namely, organic acid, alcohol amine substances and nitrate are compounded according to a certain proportion). The polymer-based nano-composite early strength agent provided by the invention can fully exert the activity of nano-silicon dioxide through specific structural design, and solves the problem of dispersion stability of the nano-silicon dioxide.
The polymer-based nano-composite early strength agent and the preparation method thereof are described in detail in the following.
The polymer-based nano-composite early strength agent provided by the invention comprises a copolymer obtained by copolymerization of a cation unit A, a carboxylic acid/nano-silica unit B, a polyether unit C and a modified alcohol amine unit D.
Table 1 below shows the structural formulae of the cation unit a (hereinafter referred to as a unit), the carboxylic acid/nano-silica unit B (hereinafter referred to as B unit), the polyether unit C (hereinafter referred to as C unit), and the modified alcohol amine unit D (hereinafter referred to as D unit).
Structural formula of unit 1A, B, C, D in Table 1
In the above structural formula, R1And R2Are selected from any one of H or methyl; the value of the average repeating unit number n of the ethoxy chain links in the C unit is an integer of 45-95.
The structural formula of the copolymer is formed by bonding the A, B, C, D units to each other, and since the final effect is mainly exhibited by the structural properties of each of the A, B, C, D units regardless of the arrangement order, it is not necessary to limit the specific arrangement order of A, B, C, D units, and it may be a structural formula such as shown in the following formula:
in the structural formula of the copolymer, the ratio of the average number of repeating units a, b, c and d of A, B, C, D units is generally defined as 1:3 to 7:1:1, and the specific average number of repeating units of A, B, C, D units is adjusted so that the weight average molecular weight of the copolymer is 20000 to 70000 and the Polymer Dispersion Index (PDI) is not more than 2.
Specifically, the B unit is obtained by esterification reaction of acrylic acid or methacrylic acid and nano-silica, and the D unit is obtained by amidation reaction of maleic anhydride and triethanolamine.
The compound early strength agent provided by the invention is generally prepared by the following method, and the preparation method is simple.
Firstly, preparing and obtaining a nano silicon dioxide aqueous solution.
Generally, the solid mass fraction of the nano-silica aqueous solution is controlled to be about 30%, wherein the purity of the nano-silica is not lower than 98%, and the average particle size is 20 nm-150 nm. The excessively small particle size causes spontaneous agglomeration to be difficult to inhibit due to too high activity, which is not favorable for subsequent grafting reaction; and if the particle size is too large, the activity is too low, so that the working performance of the obtained composite early strength agent as an additive is influenced.
Then, blending the nano silicon dioxide aqueous solution, the unit A, the acrylic acid or methacrylic acid, the unit C, the unit D, the oxidant and the mercaptan chain transfer agent in a water system, and carrying out free radical copolymer reaction at the temperature of 30-60 ℃ to obtain the composite early strength agent.
Specifically, the process of the above radical copolymer reaction is: part of the nano silicon dioxide is grafted on acrylic acid or methacrylic acid through esterification reaction to form a B unit; the copolymer is obtained by copolymerizing the A unit, the B unit, the C unit and the D unit.
In the reaction, the amount ratio of the A unit, acrylic acid or methacrylic acid, the C unit and the D unit is controlled to be 1: 3-7: 1: 1; meanwhile, the mass of the nano silicon dioxide in the nano silicon dioxide water solution is controlled to be 5-30 percent of the mass of acrylic acid or methacrylic acid (hereinafter referred to as F value); the amount of the oxidant is 0.2 to 2% of the total amount of the A unit, acrylic acid or methacrylic acid, C unit, and D unit, and the amount of the thiol chain transfer agent is 1 to 6% of the total amount of the A unit, acrylic acid or methacrylic acid, C unit, and D unit.
Further, the oxidizing agent may be any one of persulfate, a water-soluble azo compound, and peroxide, and the thiol chain transfer agent may be any one of mercaptopropionic acid, mercaptoacetic acid, mercaptoethanol, mercaptoethylamine, and dodecanethiol.
In the above reaction, the polymerization concentration of the polymerization system may be controlled to 30% to 60%.
In the reaction process, the APTAC/MAPTAC structure in the unit A has positive charges, so that the nano-silica with the surface showing electronegativity can be adsorbed, on one hand, the dispersity of the nano-silica is improved, the esterification reaction between the nano-silica and acrylic acid or methacrylic acid is promoted to generate a unit B, and on the other hand, part of the nano-silica can be adsorbed by the unit A; this dual action promotes good dispersion of the nanosilica.
The composite type early strength agent of the present invention will be described below by way of specific examples, and table 2 below shows each of the composite type early strength agents of examples 1 to 6 and the polymer structure parameters thereof.
The weight average molecular weight of the composite type early strength agent in each example is measured by Shimadzu LC-20A high performance gel chromatography (GPC), wherein TSKgel PW is adopted as a chromatographic columnXL-CP series, column temperature 40 deg.C, eluent 0.1mol/L NaNO3Aqueous solution, flow rate of 1.0mL/min, sample size of 20 u L1 ‰ sample aqueous solution, standard curve preparation using dextran standard (Sigma-Aldrich).
In each embodiment, the particle size distribution of the composite early strength agent is measured by adopting an ALV-CGS-3 integrated light scattering instrument, and an object to be measured is prepared into an aqueous solution with the concentration of 0.1 mg/mL.
In order to verify the effect of the composite early strength agent of the present invention when applied to cement-based materials, the following table 2 also provides three comparative early strength agents of comparative examples 1 to 3 and their high molecular structure parameters.
Table 2 composite early strength agent in examples 1 to 6, comparative early strength agent in comparative examples 1 to 3, and structural parameters of polymer
That is, in the structure of the first comparative early strength agent provided in comparative example 1, it is different from the structure of the composite type early strength agent in the above-described example 2 of the present invention in that the first comparative early strength agent does not contain nano silica grafted on acrylic acid, that is, the nano silica is not present at the B unit, and only the polymerized group B of acrylic acid; in the structure of the second comparative early strength agent provided in comparative example 2, which is different from the composite type early strength agent in the above-described example 2 of the present invention, the second comparative early strength agent does not contain an a unit; in the structure of the third comparative early strength agent provided in comparative example 3, it is different from the composite type early strength agent in the above-described example 2 of the present invention in that the third comparative early strength agent does not contain a D unit.
Table 3 shows the particle size parameters of the composite early strength agents of examples 1 to 6.
TABLE 3 particle size parameters of the composite early strength agents of examples 1 to 6
As can be seen from table 3, each of the composite early strength agents provided in the examples of the present invention is at a nanometer level, which also confirms that the nano-silica in the composite early strength agent is well dispersed without agglomeration; meanwhile, the composite early strength agent is a nano material and can keep better stability.
The composite early strength agent in the above examples 1 to 6 was applied to a cement-based material by the following method, and performance tests were performed.
Mixing and stirring the composite early strength agent and other cement-based material raw materials; the folding and fixing mixing amount of the composite early strength agent is controlled to be 0.2-0.3% of the using amount of the cementing material.
The basic formulation of the test mortar is shown in Table 4, the test cement is P.O 42.5.5 cement, and the test sand is ISO standard sand.
In order to verify the beneficial effect of the composite early strength agent in the aspect of early strength, the mixture ratio without any early strength agent is used as a background group; meanwhile, the early strength agents in comparative examples 1 to 3 are applied to the cement-based material by the same method.
TABLE 4 Experimental ratios of the composite early strength agent in examples 1-6 and the comparative early strength agent in comparative examples 1-3 applied to cement-based materials and background groups
The cement mortar strength test method is in accordance with GB/T17671-1999 (ISO method).
Table 5 and table 6 show the performance test results.
TABLE 5 compression strengths of cement-based materials obtained in examples 1 to 6, comparative examples 1 to 3, and background groups at different ages
As can be seen from table 5, when the composite early strength agent provided in embodiments 1 to 6 of the present invention is applied to a cement-based material, the early strength of the cement-based material can be significantly increased, and the 12h compressive strength and the 1d compressive strength of the prepared cement-based material are both significantly improved; in particular, the 12h compressive strength and the 1d compressive strength of the cement-based material obtained by using the composite early strength agent in the embodiment 4 can reach 10.56MPa and 20.17 MPa. In addition, it can be seen that under the same doping amount, the early strength effect achieved by the composite early strength agent from different embodiments is also different, and the larger or smaller content of the nano-silica is not beneficial to the dispersion of the nano-silica and further affects the overall working performance, and the reason for the trend is presumed that when the content of the nano-silica is lower, the proportion of other dispersion units in the early strength agent is higher, so that the dispersibility of the nano-silica is better, but the active sites and defects on the surface of the nano-silica are reduced, so that the nano-silica cannot generate better adsorption with the surface of cement particles, and further the strength is improved; when the content of the nano silicon dioxide is higher, silicon hydroxyl on the surface of the nano silicon dioxide is easy to aggregate to form a polymer, so that the adsorption capacity of the early strength agent is damaged to a certain extent, and the dispersion performance is poor; when the content of the nano-silica is optimal, active hydroxyl on the surface of the nano-silica is subjected to dehydration condensation with hydroxyl on the surface of cement particles, so that a chemical adsorption effect is generated, and the strength of the cement-based material can be remarkably improved.
Compared with the composite early strength agent provided in the embodiment 2, the working strength of the comparative cement-based material obtained by the comparative early strength agent provided in the comparative examples 1-3 is obviously lower than that of the cement-based material obtained by the composite early strength agent provided in the invention; the method shows that the nano silicon dioxide can not be effectively dispersed only by adsorbing the nano silicon dioxide by the cationic unit A or grafting the nano silicon dioxide by the carboxyl/nano silicon dioxide group B, and the combined action of the two is needed; in addition, the modified alcohol amine unit D also has certain working efficiency on the early strength of the cement-based material, and can promote the early strength of the cement-based material to increase.
Meanwhile, the composite early strength agent in the above example 2 is applied to a cement-based material according to different addition amount of the bending and fixing admixture, and the relationship between the bending and fixing admixture amount and the compressive strength is tested, and the test results are shown in table 6.
TABLE 6 compression strengths of different composite early strength agents at different ages
It can be easily found from table 6 that when the amount of the composite early strength agent is increased, the working strength of the obtained cement-based material is slowly increased; if the doping amount is increased continuously, the working strength of the corresponding cement-based material is reduced obviously, and the fact that when the dosage of the composite early strength agent is too much, the composite early strength agent possibly enters a supersaturated state, and secondary agglomeration of the nano silicon dioxide is possibly caused due to the bridge adsorption effect caused by adsorption groups on the composite early strength agent is confirmed; when the concentration of the composite early strength agent is further increased, macromolecular chain parts in the composite early strength agent are possibly intertwined with each other, so that the dispersion performance of cement is reduced, and finally the working strength of the obtained cement-based material is lower.
The invention utilizes the structural characteristics of the composite early strength agent, improves the dispersibility of the nano silicon dioxide by the charge adsorption dispersion effect, and further releases the activity of the nano silicon dioxide; through the esterification reaction between active hydroxyl and carboxyl on the nano-silica, the nano-silica is grafted on a molecular chain of the composite early strength agent, so that the relative molecular weight of the composite early strength agent is obviously improved, the activity of the nano-silica is exerted, the hydration reaction degree of cement is improved, the structure of a cement-based material is densified, the early strength of the cement-based material is improved, and the aims of saving cost, improving the working performance of the cement-based material and improving the compressive strength are fulfilled finally.
While the invention has been shown and described with reference to certain embodiments, those skilled in the art will understand that: various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.
Claims (8)
1. A polymer-based nano-composite early strength agent is characterized by comprising a copolymer obtained by copolymerization of a cation unit A, a carboxylic acid/nano-silica unit B, a polyether unit C and a modified alcohol amine unit D; the structural formulas of the cation unit A, the carboxylic acid/nano silicon dioxide unit B, the polyether unit C and the modified alcohol amine unit D are respectively as follows:
cation unit A:
carboxylic acid/nanosilica units B:
polyether unit C:
modified alcohol amine unit D:
in the above structural formula, R1And R2Are selected from any one of H or methyl; and the value of n is an integer of 45-95.
2. The polymer-based nano-composite type early strength agent according to claim 1, wherein in the structural formula of the copolymer, the ratio of the average repeating unit numbers a, B, C and D of the cationic unit A, the carboxylic acid/nano-silica unit B, the polyether unit C and the modified alcohol amine unit D is 1: 3-7: 1: 1; wherein the weight average molecular weight of the copolymer is 20000-70000, and the polymer dispersion index is not more than 2.
3. The polymer-based nano-composite type early strength agent according to claim 1 or 2, wherein the carboxylic acid/nano-silica unit B is obtained by esterification reaction of acrylic acid or methacrylic acid and nano-silica; the modified alcohol amine unit D is obtained by amidation reaction of maleic anhydride and triethanolamine.
4. The preparation method of the polymer-based nano-composite type early strength agent according to any one of claims 1 to 3, comprising the steps of:
s1, preparing to obtain a nano silicon dioxide aqueous solution;
s2, blending the nano silicon dioxide aqueous solution, a cation unit A, acrylic acid or methacrylic acid, a polyether unit C, a modified alcohol amine unit D, an oxidant and a thiol chain transfer agent in a water system, carrying out a free radical copolymer reaction at 30-60 ℃, and grafting the nano silicon dioxide on acrylic acid or methacrylic acid through an esterification reaction to form a carboxylic acid/nano silicon dioxide unit B; copolymerizing the cation unit A, the carboxylic acid/nano silicon dioxide unit B, the polyether unit C and the modified alcohol amine unit D to obtain a copolymer, thereby obtaining the polymer-based nano composite early strength agent;
wherein the mass ratio of the cation unit A, the acrylic acid or the methacrylic acid, the polyether unit C and the modified alcohol amine unit D is 1: 3-7: 1: 1; the mass of the nano silicon dioxide in the nano silicon dioxide aqueous solution is 5-30% of that of the acrylic acid or the methacrylic acid; the amount of the oxidant is 0.2-2% of the total amount of the cation unit A, the acrylic acid or the methacrylic acid, the polyether unit C and the modified alcohol amine unit D, and the amount of the thiol chain transfer agent is 1-6% of the total amount of the cation unit A, the acrylic acid or the methacrylic acid, the polyether unit C and the modified alcohol amine unit D.
5. The method according to claim 4, wherein in the step S2, the polymerization concentration is 30% to 60%.
6. The method according to claim 4 or 5, wherein the oxidizing agent is selected from the group consisting of persulfates, water-soluble azo compounds, and peroxides, and the thiol chain transfer agent is selected from the group consisting of mercaptopropionic acid, mercaptoacetic acid, mercaptoethanol, mercaptoethylamine, and dodecanethiol.
7. The method according to claim 4 or 5, wherein in the step S1, the solid mass fraction of the nano-silica aqueous solution is 30%, wherein the purity of nano-silica is not less than 98%, and the average particle diameter is 20nm to 150 nm.
8. The application of the polymer-based nano-composite type early strength agent in the cement-based material according to any one of claims 1 to 3, wherein the polymer-based nano-composite type early strength agent is mixed with the cement-based material raw materials and stirred; wherein the folding and fixing mixing amount of the polymer-based nano-composite early strength agent is 0.2-0.3% of the dosage of the cementing material in the cement-based material raw material.
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