CN116041614A - Inorganic-organic framework material for concrete internal curing and preparation method thereof - Google Patents

Abstract

The invention provides an inorganic-organic framework material for curing in concrete and a preparation method thereof, wherein the inorganic-organic framework material is prepared by polymerizing the following raw materials in water in parts by weight: 20-40 parts of super absorbent resin monomer, 40-60 parts of nano-scale cement hydration product, 1.5-3 parts of cross-linking agent, 1.5-3 parts of initiator and 10-20 parts of catalyst. The inorganic-organic framework material prepared by the invention has high water absorption rate and slow water release rate, and can obviously improve the damage of the internal curing agent to the mechanical property of concrete.

Description

A kind of inorganic-organic framework material and preparation method thereof for internal curing of concrete

technical field

The invention belongs to the technical field of building materials, and in particular relates to an inorganic-organic framework material used for internal curing of concrete and a preparation method thereof.

Background technique

High performance concrete (HPC) is characterized by superior mechanical properties in the hardened state. However, the durability of HPC may be compromised by its early cracking, which is related to self-drying and autogenous shrinkage. Traditional external curing methods such as covering, coating, and watering cannot effectively inhibit the self-drying effect of high-performance concrete. Studies have shown that the shrinkage of concrete can be effectively improved by using internal curing agents. Internal curing agent is a kind of material with a certain water absorption capacity, which can introduce water into the interior of cement, and release water for cement hydration as the cement hydration progresses, thereby improving the self-shrinkage of cement. However, when different types of internal curing agents are used, there are some disadvantages in terms of curing efficiency and the development of mechanical properties of the matrix. Generally, internal curing materials include organic internal curing materials and inorganic internal curing materials. Super absorbent resin (SAP) is the most typical organic internal maintenance material, which contains a large number of hydrophilic groups. When in contact with water, it can form a hydrogel with a water absorption rate of hundreds or even thousands of times its own mass. However, When organic matter is introduced into cement-based materials, there are usually problems such as excessive water release and weak organic/inorganic interface bonding, which will cause cracks and affect the mechanical properties of cement. Compared with organic internal curing agents, the use of inorganic internal curing agents can improve the interface bonding problem, but due to its own structure, the porosity of inorganic internal curing agents is low, and it is difficult to achieve the same water absorption rate as organic matter, so the internal curing effect is limited (Shrinkage improvement is low, usually only 20% to 60% of organic internal curing materials). The mechanism of action of inorganic internal curing agents is to use porous structures to absorb water. Because the pore structure of natural materials is not fine enough, it is difficult to achieve the pore structure required for curing. .

How to use the interface affinity between inorganic materials and cement-based materials to design a porous structure material with high water absorption rate, solve the shortcomings of low water absorption rate and poor curing efficiency of inorganic internal curing agents, and improve the curing efficiency of internal curing materials. urgent technical issues to be resolved.

Contents of the invention

Purpose of the invention: In order to solve the above technical problems, the present invention provides an inorganic-organic framework material for internal maintenance of concrete and a preparation method thereof.

Technical solution: An inorganic-organic framework material used for internal maintenance of concrete according to the present invention is prepared by polymerizing the following raw materials in water: 20-40 parts of superabsorbent resin monomer, 40-40 parts of nanoscale cement hydration product 60 parts, 1.5-3 parts of crosslinking agent, 1.5-3 parts of initiator, 10-20 parts of catalyst.

Further, the superabsorbent resin monomer is one or more of superabsorbent resin monomers such as acrylamide, N-isopropylacrylamide, acrylic acid, sodium acrylate, chitosan, and sodium alginate. Further preferred are N-isopropylacrylamide and sodium acrylate.

Further, the nano-scale cement hydration products include nano-calcium silicate hydrate, nano-calcium hydroxide, and nano-monosulfur/trisulfide hydrated sulfoaluminate.

Further, the water is tap water or deionized water.

Further, the crosslinking agent is one of organic dibasic acid, divinylbenzene, N,N-methylenebisacrylamide, and diisocyanate, and is further preferably N,N-methylenebisacrylamide amides.

Further, the initiator is one of azobisisobutyronitrile, dibenzoyl peroxide and persulfate, more preferably potassium persulfate.

Further, the catalyst is one of N,N,N'N'-tetramethylethylenediamine, triethylenediamine, N,N,N'N'-tetramethylethylenediamine, further Preferred is N,N,N'N'-tetramethylethylenediamine.

The present invention also provides a method for preparing an inorganic-organic framework material, comprising the following steps:

(1) Dissolving superabsorbent resin monomer powder in water by stirring, and stirring evenly to obtain solution A;

(2) Add the nanoscale cement hydration product suspension into the solution A, and keep stirring until the solution B is completely dispersed.

(3) Add the crosslinking agent and the initiator successively to the solution B, and continue to stir until completely dissolved to obtain the solution C;

(4) The catalyst is added to the solution C to catalyze the polymerization reaction to obtain a gel;

(5) Soak the gel obtained by the reaction in step (4) in deionized water, remove unreacted monomers, filter, dry, and grind to finally obtain an inorganic-organic framework material.

The catalytic polymerization reaction time in the step (4) is 1-24h, and the reaction temperature is 0-60°C. The gas atmosphere for catalytic polymerization includes oxygen, nitrogen, argon, and helium.

Technical effect: Compared with the prior art, the technical solution of the present invention has the following beneficial effects: the inorganic-organic framework material for internal curing of concrete prepared by the present invention has the advantages of both internal curing agent and inorganic internal curing agent, and has Rich porous structure, high water absorption rate, adding it to cement mortar can solve the problem of interface incompatibility between organic matter and inorganic cement-based materials, and at the same time solve the problem of excessive water release rate of traditional internal curing agents, which can significantly improve cement The mechanical properties of the base material. In addition, the inorganic-organic framework material has good construction performance, and there is no problem of aggregate floating and segregation during the concrete mixing process.

Description of drawings

Fig. 1 is the scanning electron micrograph of the inorganic-organic framework material prepared by different cement hydration product dosages of the present invention;

Fig. 2 is the scanning electron micrograph of the inorganic-organic framework material prepared by different cement hydration product dosages of the present invention;

Fig. 3 is a scanning electron micrograph of the inorganic-organic framework material prepared in Example 1 of the present invention;

Fig. 4 is the water release rate figure when the internal curing agent of the embodiment of the present invention 1-3 and comparative example 1-2 is used for concrete curing;

Fig. 5 is the comparison chart of concrete 3d and 28d mechanical properties when the internal curing agent of the embodiment of the present invention 1-3 and comparative example 1-2 is used for concrete curing;

Fig. 6 is a comparison chart of concrete self-shrinkage when the internal curing agent of Example 1-3 of the present invention and Comparative Example 1-2 are used for concrete curing.

Detailed ways

The technical solution of the present invention will be further described in detail below in conjunction with specific examples.

Example 1

The preparation steps of an inorganic-organic framework material used for internal maintenance of concrete are as follows:

(1) Disperse 1 g of N-isopropylacrylamide (Am) and 0.5 g of sodium acrylate (AA) in water by stirring until completely dissolved.

(2) Add 1g of C-S-H seed crystals into the above solution, and keep stirring to ensure uniform dispersion.

(3) Add 0.1g of N,N-methylenebisacrylamide (Bis) and 0.1g of potassium persulfate (APS) to the above solution in sequence, and stir for 10 minutes to make the solution homogeneous.

(4) Add 100 μL of about 0.75 g of N,N,N'N'-tetramethylethylenediamine (TEMED) to catalyze the APS polymerization reaction, and polymerize in a N2 atmosphere at 0°C for 24 hours to obtain a gel;

(5) Soak the gel obtained by the reaction in step (4) in deionized water, remove unreacted monomers, filter, dry, and grind to finally obtain an inorganic-organic framework material.

The obtained inorganic-organic framework material is mixed with cement mortar. Mix the cement mortar according to the water-cement ratio of 0.35, the cement-sand ratio of 1:3, and the amount of inorganic-organic framework material of 0.3%. The strength results in Fig. 5 show that the curing materials within the inorganic-organic framework can increase the mechanical properties of concrete by 17.8% and 6.7% at 3d and 28d, respectively. The results of autogenous shrinkage in Figure 6 show that the autogenous shrinkage of cement-based materials can be reduced by 100% by the curing material in the inorganic-organic framework, which can significantly improve the autogenous shrinkage of cement-based materials.

Example 2

The preparation steps of an inorganic-organic framework material used for internal maintenance of concrete are as follows:

(1) Disperse 1 g of N-isopropylacrylamide (Am) and 0.5 g of sodium acrylate (AA) in water by stirring until completely dissolved.

(2) Add 3g of C-S-H seed crystals into the above solution, and keep stirring to ensure uniform dispersion.

(3) Add 0.1g of N,N-methylenebisacrylamide (Bis) and 0.1g of potassium persulfate (APS) to the above solution in sequence, and stir for 10 minutes to make the solution homogeneous.

(4) Add 100 μL of about 0.75 g of N,N,N'N'-tetramethylethylenediamine (TEMED) to catalyze the APS polymerization reaction, and polymerize in a N2 atmosphere at 20°C for 24 hours to obtain a gel;

(5) Soak the gel obtained from the reaction in step (4) in deionized water, remove unreacted monomers, filter, dry, and grind to finally obtain an inorganic-organic framework material.

The obtained inorganic-organic framework material is mixed with cement mortar. According to the water-cement ratio of 0.35, the cement mortar ratio of 1:3, and the amount of inorganic-organic framework material of 0.3%, the cement mortar is mixed. The strength results in Figure 5 show that the curing materials within the inorganic-organic framework can increase the mechanical properties of concrete by 21.4% and 8.1% at 3d and 28d, respectively. The results of autogenous shrinkage in Figure 6 show that the autogenous shrinkage of cement-based materials can be reduced by 49% with the curing material in the inorganic-organic framework, which can significantly improve the autogenous shrinkage of cement-based materials.

Example 3

The preparation steps of an inorganic-organic framework material used for internal maintenance of concrete are as follows:

(1) Disperse 1 g of N-isopropylacrylamide (Am) and 0.5 g of sodium acrylate (AA) in water by stirring until completely dissolved.

(2) Add 5g of C-S-H seed crystals into the above solution, and keep stirring to ensure uniform dispersion.

(3) Add 0.1g of N,N-methylenebisacrylamide (Bis) and 0.1g of potassium persulfate (APS) to the above solution in sequence, and stir for 10 minutes to make the solution homogeneous.

(4) Add 100 μL of about 0.75 g of N,N,N'N'-tetramethylethylenediamine (TEMED) to catalyze the APS polymerization reaction, and polymerize in a N2 atmosphere at 60°C for 3 hours to obtain a gel;

(5) Soak the gel obtained by the reaction in step (4) in deionized water, remove unreacted monomers, filter, dry, and grind to finally obtain an inorganic-organic framework material.

The obtained inorganic-organic framework material is mixed with cement mortar. Mix the cement mortar according to the water-cement ratio of 0.35, the cement-sand ratio of 1:3, and the amount of inorganic-organic framework material of 0.3%. The strength results in Figure 5 show that the curing materials within the inorganic-organic framework can increase the mechanical properties of concrete by 31.6% and 11.1% at 3d and 28d, respectively. The results of autogenous shrinkage in Figure 6 show that the autogenous shrinkage of cement-based materials can be reduced by 31% with the curing material in the inorganic-organic framework, which can significantly improve the autogenous shrinkage of cement-based materials.

Example 4

The preparation steps of an inorganic-organic framework material used for internal maintenance of concrete are as follows:

(1) Disperse 2 g of acrylamide in water by stirring until completely dissolved.

(2) Add 3g of C-S-H seed crystals into the above solution, and keep stirring to ensure uniform dispersion.

(3) Add 0.1g of N,N-methylenebisacrylamide (Bis) and 0.1g of potassium persulfate (APS) to the above solution in sequence, and stir for 10 minutes to make the solution homogeneous.

(4) Add 100 μL of about 0.75 g of N,N,N'N'-tetramethylethylenediamine (TEMED) to catalyze the polymerization reaction of APS, and conduct the polymerization reaction at 60°C for 3 hours in a _N2 atmosphere to obtain a gel;

(5) Soak the gel obtained by the reaction in step (4) in deionized water, remove unreacted monomers, filter, dry, and grind to finally obtain an inorganic-organic framework material.

The obtained inorganic-organic framework material is mixed with cement mortar. Mix the cement mortar according to the water-cement ratio of 0.35, the cement-sand ratio of 1:3, and the amount of inorganic-organic framework material of 0.3%. Inorganic-organic framework internal curing materials can improve the mechanical properties of concrete by 28.3% and 8.7% at 3d and 28d, respectively. The autogenous shrinkage experiment results show that the autogenous shrinkage of the cement-based material can be significantly improved by the curing material in the inorganic-organic framework reducing the autogenous shrinkage of the cement-based material by 35%.

Example 5

The preparation steps of an inorganic-organic framework material used for internal maintenance of concrete are as follows:

(1) Disperse 2 g of sodium alginate in water by stirring until completely dissolved.

(2) Add 3g of C-S-H seed crystals into the above solution, and keep stirring to ensure uniform dispersion.

(3) Add 0.1g of N,N-methylenebisacrylamide (Bis) and 0.1g of potassium persulfate (APS) to the above solution in sequence, and stir for 10 minutes to make the solution homogeneous.

(4) Add 100 μL of about 0.75 g of N,N,N'N'-tetramethylethylenediamine (TEMED) to catalyze the polymerization reaction of APS, and conduct the polymerization reaction at 60°C for 3 hours in a _N2 atmosphere to obtain a gel;

(5) Soak the gel obtained by the reaction in step (4) in deionized water, remove unreacted monomers, filter, dry, and grind to finally obtain an inorganic-organic framework material.

The obtained inorganic-organic framework material is mixed with cement mortar. According to the water-cement ratio of 0.35, the cement mortar ratio of 1:3, and the amount of inorganic-organic framework material of 0.3%, the cement mortar is mixed. Inorganic-organic framework internal curing materials can improve the mechanical properties of concrete by 26.3% and 8.4% at 3d and 28d respectively. The autogenous shrinkage experiment results show that the autogenous shrinkage of the cement-based material can be significantly improved by the curing material in the inorganic-organic framework reducing the autogenous shrinkage of the cement-based material by 40%.

Comparative example 1

Ordinary inorganic internal curing agent sodium silicate

The obtained inorganic internal curing agent is mixed with cement mortar. Mix cement mortar according to the water-cement ratio of 0.35, mortar-sand ratio of 1:3, and 0.3% of inorganic internal curing agent. The inorganic internal curing agent can reduce the mechanical properties of concrete by 6% and 4% respectively at 3d and 28d. The autogenous shrinkage test results show that the inorganic internal curing agent reduces the autogenous shrinkage of cement-based materials by 11%.

Comparative example 2

Ordinary organic internal curing agent super absorbent resin (SAP)

The obtained organic internal curing agent is mixed with cement mortar. Mix cement mortar according to the water-cement ratio of 0.35, mortar-sand ratio of 1:3, and 0.3% of organic internal curing agent. The organic internal curing agent can reduce the mechanical properties of concrete by 22% and 15% respectively at 3d and 28d. The autogenous shrinkage test results show that the organic internal curing agent reduces the autogenous shrinkage of cement-based materials by 80%.

Claims (10)

1. The inorganic-organic framework material for curing in concrete is characterized by being prepared by polymerizing the following raw materials in water in parts by weight: 20-40 parts of super absorbent resin monomer, 40-60 parts of nano-scale cement hydration product, 1.5-3 parts of cross-linking agent, 1.5-3 parts of initiator and 10-20 parts of catalyst.

2. The inorganic-organic framework material according to claim 1, wherein the super absorbent resin monomer is one or more of acrylamide, N-isopropyl acrylamide, acrylic acid, sodium acrylate, chitosan, sodium alginate and the like.

3. The inorganic-organic framework material of claim 1, wherein the nanoscale cement hydration product comprises nano calcium silicate hydrate, nano calcium hydroxide, nano mono/tri-sulfur hydrated sulfoaluminate.

4. The inorganic-organic framework material of claim 1 wherein the water is tap water or deionized water.

5. The inorganic-organic framework material of claim 1, wherein the cross-linking agent is one of an organic diacid, divinylbenzene, N-methylenebisacrylamide, and diisocyanate.

6. The inorganic-organic framework material of claim 1 wherein the initiator is one of azobisisobutyronitrile, dibenzoyl peroxide, persulfate.

7. The inorganic-organic framework material of claim 1 wherein the catalyst is one of N, N-dimethylcyclohexane, triethylenediamine, N' -tetramethyl ethylenediamine.

8. The method for preparing an inorganic-organic framework material according to any one of claims 1 to 7, comprising the steps of:

(1) Dissolving the super absorbent resin monomer powder into water by stirring, and uniformly stirring to obtain a solution A;

(2) Adding the nano-scale cement hydration product suspension into the solution A, and continuously stirring until the solution A is completely dispersed to obtain the solution B.

(3) Adding a cross-linking agent and an initiator into the solution B in sequence, and continuously stirring until the cross-linking agent and the initiator are completely dissolved to obtain a solution C;

(4) Adding a catalyst into the solution C to catalyze the polymerization reaction to obtain gel;

(5) Soaking the gel obtained in the step (4) in deionized water, removing unreacted monomers, filtering, drying and grinding to finally obtain the inorganic-organic framework material.

9. The method for preparing inorganic-organic framework material according to claim 8, wherein the catalytic polymerization reaction time in the step (4) is 1-24 hours, and the reaction temperature is 0-60 ℃.

10. The method for preparing an inorganic-organic framework material according to claim 8, wherein the gas atmosphere for catalyzing the polymerization reaction in the step (4) comprises oxygen, nitrogen, argon, helium.

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