Early high-strength shotcrete nanocrystal glue polymer additive

Abstract

The application relates to an early high-strength shotcrete nanocrystal glue polymer additive and a preparation method thereof, and aims to accurately control the cement hydration process and the microstructure formation and evolution process according to the cement hydration theory, develop a brand-new concrete additive, and realize the technical requirements of early strength and high strength of shotcrete through the following steps: 1) aldehyde group modification of nanocellulose; 2) preparation of a nanometal oxide dispersion liquid; and 3) preparation of a nanocrystal glue polymer. The cement minerals in water are improved in dispersity, the contact area of solid-liquid reaction is improved, and the early hydration of concrete is accelerated; the nanocrystal nucleus is introduced, the nucleation and crystallization of cement hydration products are accelerated, the ion concentration in the electrolyte solution is rapidly reduced, and the hydration process is accelerated; the aldehyde group nanocellulose performs directional adsorption on each mineral phase in the cement, realizes mineral phase inactivation, accelerates the C3A reaction process, realizes accurate design of the whole hydration process, and realizes the rapid setting and early strength of the concrete.

Description

Technical Field

[0001] This invention provides a nanocrystalline polymer additive for early high-strength shotcrete, belonging to the field of building materials. Background Technology

[0002] Shotcrete, as an important component of the initial support system during construction, is widely used in the repair of damaged concrete surfaces, tunnel lining, and underground engineering construction due to its convenient and quick application. Currently, tunnel lining is gradually being replaced by single-layer permanent lining worldwide, and shotcrete is widely used in the repair of important transportation structures, which in turn places higher demands on the strength and performance of shotcrete.

[0003] Research on high-strength shotcrete has started rapidly both domestically and internationally, mainly focusing on improving the accelerator components to formulate shotcrete with higher strength grades and better 28-day compressive strength. However, few scholars, both domestically and internationally, have focused their research on the 8-hour / 24-hour early strength of shotcrete, nor have they proposed effective methods to improve its early strength. Currently, the workability of shotcrete is relatively poor, failing to fully utilize the self-supporting capacity of the surrounding rock in the early stages of spraying, thus failing to play a significant role in tunnel support systems. Therefore, how to improve the early strength and workability of shotcrete is an urgent scientific and technological challenge that needs to be addressed. Summary of the Invention

[0004] This invention proposes a nanocrystalline polymer additive for early-strength shotcrete. Its purpose is to accurately control the cement hydration process and the formation and evolution of microstructure based on the cement hydration theory, and to develop a brand-new concrete admixture to achieve the technical requirements of early strength and high strength of shotcrete.

[0005] The technical solution of this invention:

[0006] A method for preparing a nanocrystalline polymer additive for early high-strength shotcrete is achieved through the following steps:

[0007] 1) Aldehyde-modified nanocellulose;

[0008] 2) Preparation of nano-metal oxide dispersions;

[0009] 3) Preparation of nanocrystalline polymer.

[0010] Further, the specific steps of the aldehyde-modified nanocellulose are as follows: nanocellulose and water-soluble polymer are crosslinked to prepare a polymer hydrogel; the polymer hydrogel is dispersed in water, 2,2,6,6-tetramethylpiperidine oxide and sodium bromide are added and stirred thoroughly, the pH is maintained at 10-12, sodium hypochlorite solution is added, the reaction is carried out for 0.5-1h, and then anhydrous ethanol is added to terminate the reaction to obtain aldehyde-modified nanocellulose.

[0011] As a preferred embodiment, the mass ratio of the polymer hydrogel, 2,2,6,6-tetramethylpiperidine oxide, and sodium bromide is 30~60:0.1~0.3:1~3.

[0012] As a preferred embodiment, the nanocellulose is one or more of the following: cellulose nanofibers, cellulose nanocrystals, nanobacterial cellulose, hair-like cellulose nanocrystals, quaternary ammonium salt cationized hair-like cellulose nanocrystals, amphiphilic cellulose nanofibers, and amphiphilic cellulose nanocrystals.

[0013] As a preferred embodiment, the water-soluble polymer includes one or more of starch, cellulose derivatives, polyacrylic acid, polyacrylamide, and polyvinyl alcohol.

[0014] As a preferred embodiment, the crosslinking agent is one or more of epichlorohydrin, glutaraldehyde, divinyl sulfone, and diethanol glycidyl ether.

[0015] Furthermore, the specific steps for preparing the nano-metal oxide dispersion are as follows:

[0016] a) Prepare a nanocellulose dispersion with a mass fraction of 0.2%~1%;

[0017] b) Add the nano-metal oxide particles to the nano-cellulose dispersion and mix them evenly by mechanical stirring to obtain the nano-metal oxide dispersion.

[0018] As a preferred embodiment, the nanocellulose used in step a) is the same as that used in step 1); the dispersion is prepared by centrifuging at 1000~5000 rpm for 2~5 min.

[0019] As a preferred embodiment, in step b), the mechanical stirring is performed by centrifugation or ball milling.

[0020] As a preferred embodiment, the centrifugation involves adding nano-metal oxide particles to deionized water and centrifuging at 5000~10000 rpm to obtain a preliminarily dispersed aqueous dispersion of nano-metal oxide particles, followed by adding the nano-cellulose dispersion and mixing evenly; the mass ratio of the nano-metal oxide particles to the nano-cellulose in step a) is ≥5:1.

[0021] As a preferred embodiment, the ball milling process involves directly mixing the nano-metal oxide particles with the nano-cellulose dispersion and placing them in a ball milling jar, wherein the mass ratio of the nano-metal oxide particles to the nano-cellulose in step a) is ≥5:1.

[0022] As a preferred embodiment, the nano-metal oxide particles are one or more of titanium dioxide, tungsten trioxide, nickel oxide, vanadium oxide, or zinc oxide nanoparticles.

[0023] As a preferred embodiment, the size of the nano-metal oxide particles is 5~100nm.

[0024] Furthermore, the nanocrystalline polymer component includes: aldehyde-modified nanocellulose, nanometal oxide dispersion, dispersant, excipients, and water.

[0025] As a preferred embodiment, the dispersant comprises a comb-shaped polymer dispersant and a small component; the weight parts of the dispersant are: 80-95 parts of comb-shaped polymer dispersant and 5-20 parts of small component.

[0026] As a preferred embodiment, the comb-shaped polymer dispersant is a six-carbon comb-shaped polymer super liquid dispersant; the polyether macromonomer used in the synthesis of the six-carbon comb-shaped polymer super liquid dispersant has a molecular weight greater than 4000.

[0027] As a preferred embodiment, the minor component is one or more of polyethylene glycol, 2-acrylamide-2-methylpropanesulfonic acid, sodium methyl allyl sulfonate, β-mercaptopropionic acid, mercaptoacetic acid, persulfate, azobisisobutyronitrile, diacyl peroxide, and sodium gluconate.

[0028] As a preferred embodiment, the excipient is one or more of sodium chloride, sodium nitrate, sodium nitrite, sodium sulfate, sodium gluconate, potassium chloride, potassium nitrate, potassium nitrite, and potassium sulfate.

[0029] Further, the method for preparing the nanocrystalline polymer is as follows: the components of the dispersant are mixed in proportion, stirred evenly, heated to 60°C, and cooled for later use; the nano metal oxide dispersion is added to the dispersant, stirred evenly, and then the aldehyde-modified nanocellulose and excipients are added, and the mixture is stirred continuously for 24 hours to obtain the nanocrystalline polymer.

[0030] The beneficial effects of this invention are:

[0031] 1) By increasing the dispersion of cement minerals in water, the contact area of ​​the solid-liquid reaction is increased, thus accelerating the early hydration of concrete;

[0032] 2) By introducing nanocrystal nuclei, the nucleation and crystallization of cement hydration products are accelerated, the ion concentration in the electrolyte solution is rapidly reduced, and the hydration process is accelerated;

[0033] 3) Aldehyde-based nanocellulose can perform directional adsorption on various mineral phases in cement, thereby deactivating the mineral phases, accelerating the C3A reaction process, achieving precise design of the entire hydration process, and realizing the rapid setting and early strength of concrete. Detailed Implementation

[0034] The technical solution of the present invention will be further explained below.

[0035] A method for preparing a nanocrystalline polymer additive for early high-strength shotcrete is achieved through the following steps:

[0036] 1) Aldehyde-modified nanocellulose: A polymer hydrogel was prepared by crosslinking nanocellulose with a water-soluble polymer using a crosslinking agent; the polymer hydrogel was dispersed in water, and 2,2,6,6-tetramethylpiperidine oxide and sodium bromide were added and stirred thoroughly, maintaining the pH at 10-12. Sodium hypochlorite solution was added, and the reaction was terminated by adding anhydrous ethanol after 0.5-1 h to obtain aldehyde-modified nanocellulose. The mass ratio of the polymer hydrogel, 2,2,6,6-tetramethylpiperidine oxide, and sodium bromide was 30-60:0.1-0.3:1-3.

[0037] 2) Preparation of nano-metal oxide dispersion; a) Prepare a nano-cellulose dispersion with a mass fraction of 0.2%~1%; b) Add nano-metal oxide particles to the nano-cellulose dispersion and mechanically stir to mix evenly to obtain nano-metal oxide dispersion.

[0038] 3) Preparation of nanocrystalline polymer; the nanocrystalline polymer components include: aldehyde-modified nanocellulose, nano-metal oxide dispersion, dispersant, excipients, and water. The components of the dispersant are mixed in proportion, stirred evenly, heated to 60°C, and cooled for later use; the nano-metal oxide dispersion is added to the dispersant, stirred evenly, and then the aldehyde-modified nanocellulose and excipients are added, and stirring is continued for 24 hours to obtain the nanocrystalline polymer.

[0039] Nanocellulose is one or more of the following: cellulose nanofibers, cellulose nanocrystals, nanobacterial cellulose, hair-like cellulose nanocrystals, quaternary ammonium salt cationized hair-like cellulose nanocrystals, amphiphilic cellulose nanofibers, and amphiphilic cellulose nanocrystals.

[0040] Water-soluble polymers include one or more of starch, cellulose derivatives, polyacrylic acid, polyacrylamide, and polyvinyl alcohol.

[0041] The crosslinking agent is one or more of epichlorohydrin, glutaraldehyde, divinyl sulfone, and diethanol glycidyl ether.

[0042] The nano-metal oxide particles are one or more of titanium dioxide, tungsten trioxide, nickel oxide, vanadium oxide, or zinc oxide nanoparticles. The mass ratio of the nano-metal oxide particles to the nanocellulose in step a) is ≥5:1.

[0043] The dispersant includes a comb-shaped polymer dispersant and a small component; the weight parts of the dispersant are: 80-95 parts of comb-shaped polymer dispersant and 5-20 parts of small component.

[0044] The minor component is one or more of the following: polyethylene glycol, 2-acrylamide-2-methylpropanesulfonic acid, sodium methyl allyl sulfonate, β-mercaptopropionic acid, mercaptoacetic acid, persulfate, azobisisobutyronitrile, diacyl peroxide, and sodium gluconate. The excipients are one or more of the following: sodium chloride, sodium nitrate, sodium nitrite, sodium sulfate, sodium gluconate, potassium chloride, potassium nitrate, potassium nitrite, and potassium sulfate.

[0045] Example 1

[0046] 1) Aldehyde-modified cellulose nanoparticles: Cellulose nanocrystals and starch were reacted with diethylene sulfone to prepare a cellulose polymer hydrogel; the polymer hydrogel was dispersed in water, and 2,2,6,6-tetramethylpiperidine oxide and sodium bromide were added and stirred thoroughly, maintaining the pH at 10-12. Sodium hypochlorite solution was added, and the reaction was terminated by adding anhydrous ethanol after 0.5-1 h to obtain aldehyde-modified cellulose nanoparticles. The mass ratio of the polymer hydrogel, 2,2,6,6-tetramethylpiperidine oxide, and sodium bromide was 30:0.3:3.

[0047] 2) Preparation of nano metal oxide dispersion; a) Prepare a nano cellulose dispersion with a mass fraction of 0.2%~1%; b) Add nano zinc oxide to the nano cellulose dispersion and mechanically stir to mix evenly to obtain nano zinc oxide dispersion.

[0048] 3) Preparation of nanocrystalline polymer; the nanocrystalline polymer components include: aldehyde-modified nanocellulose, nano-metal oxide dispersion, dispersant, excipients, and water. The components of the dispersant are mixed in proportion, stirred evenly, heated to 60°C, and cooled for later use; the nano-metal oxide dispersion is added to the dispersant, stirred evenly, and then the aldehyde-modified nanocellulose and excipients are added, and stirring is continued for 24 hours to obtain the nanocrystalline polymer.

[0049] The prepared nanocrystalline polymer was mixed into C30 shotcrete at a dosage of 5%, and the compressive strength was measured and compared with that of the benchmark shotcrete as follows:

[0050] model 8h 24h 28d benchmark 2.5Mpa 10.8 MPa 41.3 MPa Example 1 12.9 MPa 24.8 MPa 45.5 MPa

Claims

1. A method for preparing a nanocrystalline polymer additive for early high-strength shotcrete, characterized in that... Includes the following steps: 1) Aldehyde-modified nanocellulose: Nanocellulose and water-soluble polymers are crosslinked to prepare polymer hydrogels; the polymer hydrogels are dispersed in water, 2,2,6,6-tetramethylpiperidine oxide and sodium bromide are added and stirred thoroughly, the pH is maintained at 10-12, sodium hypochlorite solution is added, the reaction is carried out for 0.5-1 h, and then anhydrous ethanol is added to terminate the reaction to obtain aldehyde-modified nanocellulose; 2) Preparation of nano-metal oxide dispersion: Prepare a nano-cellulose dispersion with a mass fraction of 0.2%~1%; add nano-metal oxide particles to the nano-cellulose dispersion and mechanically stir to mix evenly to obtain nano-metal oxide dispersion; 3) Preparation of nanocrystalline polymer: The nanocrystalline polymer components include the aldehyde-modified nanocellulose of step 1), the nano-metal oxide dispersion of step 2), dispersant, excipients, and water; The water-soluble polymer includes one or more of starch, cellulose derivatives, polyacrylic acid, polyacrylamide, and polyvinyl alcohol; The crosslinking agent is one or more of epichlorohydrin, glutaraldehyde, divinyl sulfone, and diethanol glycidyl ether. The size of the nano-metal oxide particles is 5~100nm; the nano-metal oxide particles are one or more of titanium dioxide, tungsten trioxide, nickel oxide, vanadium oxide or zinc oxide nanoparticles; The dispersant includes a comb-like polymer dispersant and a small component; the small component is one or more of polyethylene glycol, 2-acrylamide-2-methylpropanesulfonic acid, sodium methyl allyl sulfonate, β-mercaptopropionic acid, mercaptoacetic acid, persulfate, azobisisobutyronitrile, diacyl peroxide, and sodium gluconate. The excipients are one or more of the following: sodium chloride, sodium nitrate, sodium nitrite, sodium sulfate, sodium gluconate, potassium chloride, potassium nitrate, potassium nitrite, and potassium sulfate.

2. The preparation method of the nanocrystalline polymer additive for early high-strength shotcrete according to claim 1, characterized in that: In step 1), the nanocellulose is one or more of cellulose nanofibers, cellulose nanocrystals, and nanobacterial cellulose; the cellulose nanofibers are amphiphilic cellulose nanofibers; and the cellulose nanocrystals are one or more of hair-like cellulose nanocrystals, quaternary ammonium salt cationized hair-like cellulose nanocrystals, and amphiphilic cellulose nanocrystals.

3. The preparation method of the nanocrystalline polymer additive for early high-strength shotcrete according to claim 1, characterized in that: In step 1), the mass ratio of the polymer hydrogel, 2,2,6,6-tetramethylpiperidine oxide and sodium bromide is 30~60:0.1~0.3:1~3.

4. The preparation method of a nanocrystalline polymer additive for early high-strength shotcrete according to claim 1, characterized in that: In step 2), the nanocellulose used is the same as that used in step 1); the dispersion is prepared by centrifuging at 1000-5000 rpm for 2-5 minutes.

5. The preparation method of a nanocrystalline polymer additive for early high-strength shotcrete according to claim 1, characterized in that: In step 2), mechanical stirring is performed by centrifugation or ball milling; the mass ratio of the nano-metal oxide particles to the nano-cellulose in step 2) is ≥5:

1.

6. The preparation method of a nanocrystalline polymer additive for early high-strength shotcrete according to claim 1, characterized in that: The method for preparing the nanocrystalline polymer described in step 3) is as follows: mix the components of the dispersant in proportion, stir evenly, heat to 60°C, and cool for later use; add the nano metal oxide dispersion to the dispersant, stir evenly, then add the aldehyde-modified nanocellulose and excipients, and continue stirring for 24 hours to obtain the nanocrystalline polymer.