A micro-expanding commercial concrete and a method for preparing the same

Abstract

The application provides a kind of micro-expansion commercial concrete and its preparation method, including gravel, sand, cement, admixture, antifreeze, expanding agent, chitosan phase change microcapsule, plugging agent, water, the preparation method of the plugging agent is: S1, using the chitosan with molecular weight of 150-200 thousand and degree of deacetylation of 90%-92% to wrap gypsum, to block the pores on the gypsum, S2, adding crosslinking agent in the preparation S1 process, and using strong alkali weak acid salt that can provide Ca2+ as chitosan precipitant, to consume the active functional groups of chitosan, S3, relying on the adsorbed water from the surface of chitosan film obtained from S2, to wrap a layer of gypsum on the surface of chitosan film again, to protect the chitosan film, to obtain cement stone microcrack self-plugging material, by using the plugging agent, after water is sprinkled on the surface of the formed concrete, the plugging agent can expand, so as to plug the small cracks in the concrete, and then improve the strength of the concrete.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, and in particular to a micro-expansion commercial concrete and a preparation method thereof. Background Art

[0002] Mass concrete plays a crucial role in modern engineering construction, being used extensively not only in buildings and other projects but also in water conservancy projects. In actual construction, due to the influence of "deformation loads," mass concrete structures are prone to cracking. The presence of cracks directly impacts the overall performance and operational functionality of the structure. Therefore, appropriate measures should be taken to prevent or control the development of cracks to ensure structural safety and operational functionality.

[0003] In the prior art, the Chinese invention patent application document with application number CN202110091972.6 discloses a micro-expansive concrete with an added expansive agent, which includes the following components in parts by mass: 340-360 parts of cement; 170-190 parts of water; 600-620 parts of sand; 1230-1270 parts of stone; 1.5-2 parts of lignin sulfonate; 10-15 parts of sulfoaluminate expansive agent; and 30-35 parts of calcium oxide expansive agent. The preparation method is: uniformly mix the components to form a micro-expansive concrete slurry, and then cure and shape it.

[0004] In the above-mentioned related technologies, a certain amount of expansive agent is added to the concrete so that the concrete can expand to a certain extent during the hydration period due to the action of the expansive agent, thereby compensating for the shrinkage of the concrete, achieving the purpose of preventing concrete cracks and improving concrete performance. However, during winter construction, hydration heat is generated early, and due to the large temperature difference between the inside and outside of the concrete, small cracks will still appear inside. With continuous freezing and melting, the internal cracks gradually increase, thereby affecting the strength of the concrete structure. Summary of the Invention

[0005] The embodiment of the present invention provides a micro-expansive commercial concrete and a preparation method thereof. By using a blocking agent, water is sprinkled on the surface of the formed concrete, which can cause the blocking agent to expand, thereby blocking small cracks inside the concrete and further improving the strength of the concrete.

[0006] In view of the above problems, the technical solution proposed by the present invention is:

[0007] A micro-expansive commercial concrete comprises the following raw materials in parts by weight: crushed stone: 850-930, sand: 790-910, cement: 280-360, admixture: 85-135, antifreeze: 7-9, expansion agent: 37-43, chitosan phase change microcapsules: 4-7, blocking agent: 5-6, water: 145-190, and the preparation method of the blocking agent is as follows: S1, using a molecular weight of 150,000-200,000 and a deacetylation degree of 9 0% to 92% chitosan is used to wrap the gypsum to seal the pores on the gypsum. S2, a cross-linking agent is added during the preparation of S1, and a strong base weak acid salt that can provide Ca2+ is used as a chitosan precipitating agent to consume the active functional groups of chitosan. S3, relying on the adsorbed water on the surface of the chitosan film obtained from S2, the surface of the chitosan film is wrapped with a layer of gypsum to protect the chitosan film, thereby obtaining a cement stone micro-crack self-sealing material when it encounters water.

[0008] By adopting the above technical solution, hydration heat is generated early during winter construction. Due to the large temperature difference between the inside and outside of the concrete, small cracks will still appear inside. With continuous freezing and melting, the internal cracks gradually increase, thereby affecting the strength of the concrete structure. Since chitosan expands little under alkaline conditions, only small macroscopic pores will be produced. When water enters the cracks of the concrete and causes the pH value to decrease, the chitosan will expand. The sealing agent made from this property of chitosan is added to the concrete. After the concrete is poured and water is sprinkled on its surface, the sealing agent can be triggered to expand, thereby blocking the gaps caused by freezing and improving the strength of the concrete.

[0009] As a preferred technical solution of the present invention, the preparation method of the chitosan phase change microcapsules is as follows: S1, using chitosan as the wall material and paraffin as the core material, and using chitosan to wrap the paraffin to obtain chitosan phase change microcapsules; S2, using silica to wrap the chitosan phase change microcapsules obtained from S1 to obtain silica chitosan phase change microcapsules.

[0010] By adopting the above technical solution, since chitosan has good adsorption properties, the chitosan phase change microcapsules made therefrom can reduce the flow rate of concrete, thereby improving the slump of concrete.

[0011] As a preferred technical solution of the present invention, the antifreeze comprises the following raw materials in the following weight percentages: 40% of an antifreeze component, 45% of an early strength component, 7% of an air entraining component, and 8% of a water reducing component. The preparation method of the antifreeze is as follows: sodium sulfate with a concentration of 1% to 1.5%, sodium nitrite with a concentration of 1% to 3%, calcium chloride with a concentration of 0.3% to 0.5%, and sodium chloride with a concentration of 0.3% to 0.5%, and stirring to obtain the antifreeze.

[0012] The anti-freezing component can destroy the crystal form of ice, reduce the liquid phase freezing point of water, keep the liquid water needed for the cement hydration reaction in the concrete, avoid the freezing damage of the concrete, and quickly reach the early strength. The early strength component can play a catalytic role in the hydration reaction of the concrete, accelerate the setting and hardening of the concrete, and make the concrete quickly reach the anti-freezing critical strength, thereby improving the anti-freezing capacity of the concrete. The air entraining component can introduce fine air bubbles, absorb the frost heaving stress generated in the ice crystal formation process, reduce the crack expansion of the concrete in the frost heaving process, reduce the frost heaving force of the concrete, and reduce the water consumption of the concrete, eliminate the internal frost heaving factors, and enhance the compactness of the concrete. The water reducing component can disperse the cement into smaller particles, and improve the internal pore structure of the concrete.

[0013] As a preferred technical solution of the present application, the expansive agent is mixed by magnesium oxide expansive agent and lime expansive agent in a mass ratio of 1:(2-4).

[0014] By adopting the above technical solution, the expansive agent is added in the concrete, volume expansion can be generated in the strength growth process of the concrete, internal compressive stress and compressive strain are generated, various shrinkage deformations can be compensated, the corresponding tensile stress can be offset, and the crack resistance of the structure can be effectively improved. Since most of the energy released in the expansion deformation occurs in the early stage of the concrete curing, the concrete is in a plastic state at this time, and therefore a large number of voids can be easily compressed and compacted, and the compacting effect can be significantly improved.

[0015] As a preferred technical solution of the present application, the admixture is one or more of fly ash, slag powder and silica fume, and the weight ratio of the fly ash, slag powder and silica fume is (4-8):(8-10):(5-9).

[0016] By adopting the above technical solution, since the fly ash and the slag powder can replace part of the cement, the cement addition amount is reduced, thereby reducing the cement hydration heat release, reducing the cracking degree of the concrete, the silica fume can fill the voids of the fly ash, the slag powder and the cement, reducing the voids is conducive to reducing the entry of external air into the concrete, reducing the erosion of the concrete, and increasing the strength of the concrete.

[0017] On the other hand, the present application provides a method for preparing micro-expansion commercial concrete, comprising the following steps:

[0018] S1, adding gravel, sand and cement into a mixer, and stirring at a speed of 50 r / min for 5 min;

[0019] S2, adding an admixture and an expansive agent into the mixture of S1, and stirring at a speed of 60 r / min for 5 min;

[0020] S3, add blocking agent, chitosan phase change microcapsules, antifreeze and water to the mixture of S2, stir at 60 r / min for 10 min, add inhibitor and stir at 60 r / min for 4 min to prepare micro-expansive concrete.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. Since chitosan expands little under alkaline conditions, only small macro pores will be produced. When water enters the cracks of concrete and causes the pH value to decrease, chitosan will expand. The sealing agent made by utilizing this characteristic of chitosan is added to the concrete. After the concrete is poured and water is sprinkled on its surface, the sealing agent will expand, thereby blocking the gaps caused by freezing and improving the strength of the concrete.

[0023] 2. Because chitosan has good adsorption properties, the chitosan phase change microcapsules made from it can reduce the flow rate of concrete, thereby improving the slump of concrete.

[0024] 3. The antifreeze component destroys ice crystals, lowers the liquidus freezing point of water, and maintains liquid water within the concrete required for the cement hydration reaction, protecting the concrete from frost damage and enabling it to reach early strength as quickly as possible. The early-strengthening component catalyzes the concrete hydration reaction, accelerating the setting and hardening of the concrete, allowing it to reach its critical frost resistance strength as quickly as possible and improving its frost resistance. The air-entraining component introduces tiny bubbles that absorb the frost heave stress generated during ice crystal formation, mitigating crack propagation during frost heave and reducing the frost heave force on the concrete. The water-reducing component reduces concrete water consumption, eliminates the internal causes of frost heave, and enhances concrete density. Water reducers disperse cement into smaller particles, improving the internal pore structure of concrete.

[0025] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. Specific embodiments

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0027] Preparation Example 1, a method for preparing a plugging agent is as follows: S1, using chitosan with a molecular weight of 150,000 to 200,000 and a deacetylation degree of 90% to 92% to wrap gypsum to block the pores on the gypsum; S2, adding a cross-linking agent during the preparation of S1, and using a strong base weak acid salt that can provide Ca2+ as a chitosan precipitating agent to consume the active functional groups of chitosan; S3, relying on the adsorbed water on the surface of the chitosan film obtained from S2, wrapping the surface of the chitosan film with a layer of gypsum to protect the chitosan film, thereby obtaining a cement stone micro-crack self-sealing material when exposed to water.

[0028] Preparation Example 2, the preparation method of chitosan phase change microcapsules is as follows: S1, using chitosan as the wall material and paraffin as the core material, and using chitosan to wrap the paraffin to obtain chitosan phase change microcapsules, S2, using silica to wrap the chitosan phase change microcapsules obtained from S1 to obtain silica chitosan phase change microcapsules.

[0029] Preparation Example 3: The antifreeze comprises the following raw materials in weight percentage: 40% of an antifreeze composition, 45% of an early strength composition, 7% of an air entraining composition, and 8% of a water reducing composition. The preparation method of the antifreeze is as follows: sodium sulfate with a concentration of 1% to 1.5%, sodium nitrite with a concentration of 1% to 3%, calcium chloride with a concentration of 0.3% to 0.5%, and sodium chloride with a concentration of 0.3% to 0.5%, and stirring to obtain the antifreeze.

[0030] Example 1

[0031] A kind of slightly expansive commercial concrete, the raw material dosage is shown in Table 1:

[0032] The cement is P.O42.5 silicate cement, the sand is zone II graded sand, the fineness modulus is 2.5, the apparent density is 2500kg / m3, the bulk density is 1400kg / m3, the mud content is 0.2%, the mass percentage of chloride ions is 0.00015%, the particle size of the gravel is 5-25mm continuous grading, the content of needle-like particles is 4%, the apparent density is 2500kg / m3, the bulk density is 1400kg / m3, the mud content is 0.1%, the fly ash in the admixture is Class F II fly ash, the slag powder is S95 grade mineral powder, the expansion agent is magnesium oxide expansion agent and lime expansion agent, the plugging agent is made by Preparation Example 1, the chitosan phase change microcapsules are made by Preparation Example 2, and the antifreeze agent is made by Preparation Example 3.

[0033] The method for preparing the above-mentioned slightly expansive commercial concrete comprises the following steps:

[0034] S1, add gravel, sand and cement into the mixer and mix at 50r / min for 5min;

[0035] S2, add admixtures and expansion agent to the mixture of S1, and stir at 60r / min for 5min;

[0036] S3, add blocking agent, chitosan phase change microcapsules, antifreeze and water to the mixture of S2, stir at 60 r / min for 10 min, add inhibitor and stir at 60 r / min for 4 min to prepare micro-expansive concrete.

[0037] Examples 2-3 are slightly expansive commercial concretes. The difference from Example 1 is that the amounts of raw materials used are as shown in Table 1.

[0038]

[0039]

[0040] Table 1 Amount of raw materials used in concrete in Examples 1 to 3

[0041] Comparative Example 1: A slightly expansive commercial concrete, which differs from Example 1 in that no blocking agent is added.

[0042] Comparative Example 2: A slightly expansive commercial concrete, which differs from Example 1 in that chitosan phase change microcapsules are not added.

[0043] Comparative Example 3: A slightly expansive commercial concrete, which differs from Example 1 in that no antifreeze is added.

[0044]

[0045]

[0046] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A slightly expansive commercial concrete, characterized in that: The invention comprises the following raw materials in parts by weight: crushed stone: 850-930, sand: 790-910, cement: 290-360, admixture: 85-135, antifreeze: 7-9, expansion agent: 37-43, chitosan phase change microcapsules: 4-7, plugging agent: 5-6, water: 145-190. The preparation method of the plugging agent is as follows: S1, chitosan with a molecular weight of 150,000-200,000 and a deacetylation degree of 90%-92% is used to wrap gypsum to block the pores on the gypsum; S2, a cross-linking agent is added during the preparation of S1, and a strong base weak acid salt that can provide Ca2+ is used as a chitosan precipitation agent to consume the active functional groups of chitosan; S3, relying on the adsorbed water on the surface of the chitosan film obtained from S2, the surface of the chitosan film is further wrapped with a layer of gypsum to protect the chitosan film, thereby obtaining a cement stone micro-crack self-sealing material when it encounters water.

2. The slightly expansive commercial concrete according to claim 1, characterized in that: The preparation method of the chitosan phase change microcapsules is as follows: S1, using chitosan as the wall material and paraffin as the core material, and using chitosan to wrap the paraffin to obtain chitosan phase change microcapsules; S2, using silica to wrap the chitosan phase change microcapsules obtained in S1, thereby obtaining silica chitosan phase change microcapsules.

3. The slightly expansive commercial concrete according to claim 1, characterized in that: The antifreeze comprises the following raw materials in percentage by weight: 40% of an antifreeze component, 45% of an early strength component, 7% of an air entraining component, and 8% of a water reducing component.

4. The slightly expansive commercial concrete according to claim 1, characterized in that: The expansion agent is prepared by mixing a magnesium oxide expansion agent and a lime expansion agent in a mass ratio of 1:(2-4).

5. The slightly expansive commercial concrete according to claim 1, characterized in that: The admixture is one or more of fly ash, slag powder and silica fume, and the weight ratio of the admixture is (4-8): (8-10): (5-9).

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