Anti-cracking concrete and its production process
By using anti-mud composite water-reducing agent and modified magnesium aluminum hydrotalcite, combined with alkali-resistant reinforcing fibers, the problems of concrete water-reducing agent failure and insufficient durability in high mud and gravel environments were solved, achieving improved crack prevention and durability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- FUJIAN WUJIAN CONSTR GRP CO LTD
- Filing Date
- 2026-04-13
- Publication Date
- 2026-06-19
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Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention relates to the field of building materials technology, and in particular to a crack-resistant concrete and its production process. Background Technology
[0002] Concrete, as a core structural material in modern construction engineering, directly determines the safety and durability of the project. However, in recent years, with the increasing scarcity of natural sand and gravel resources and the widespread use of substitute aggregates such as manufactured sand and desalinated sea sand, the quality of sand and gravel has generally declined, and excessive mud content has become a key bottleneck restricting concrete performance. While traditional polycarboxylate superplasticizers have the advantage of high water reduction efficiency, the carboxyl groups (-COO) in their molecular structure... - It is easily adsorbed and intercalated by the layered structure of clay minerals (such as montmorillonite and illite), which leads to a sharp drop in the water-reducing and dispersing effect. Not only does it require an additional increase in the amount of water-reducing agent, but it also causes construction problems such as rapid loss of concrete slump and segregation and bleeding, which seriously affect the quality and progress of the project.
[0003] Meanwhile, concrete cracking and insufficient durability remain industry challenges. On the one hand, the deterioration of paste workability caused by high mud content aggregates easily leads to plastic shrinkage cracks; on the other hand, microcracks caused by chloride ion erosion (in coastal areas or de-icing salt environments), carbonation shrinkage, and load effects, if not suppressed in time, will gradually expand into macro-cracks, ultimately leading to a decrease in structural load-bearing capacity. Traditional crack prevention technologies mostly rely on single components (such as simply increasing fiber content or using crack-resistant agents).
[0004] Chinese Patent Publication No. CN119349939A discloses a preparation process for heat-resistant and crack-resistant concrete, including the following steps: preparing a suspension; preparing treated PVA fibers; modifying the PVA fibers with VAE emulsion; and preparing concrete. This invention utilizes calcium carbonate whiskers and a water-reducing agent to create a suspension, and treats the PVA fibers with anatase and fly ash. The water-reducing agent reduces the material's water requirement and improves the fluidity of the slurry, thus ensuring uniform mixing of the PVA fibers and powder. The anatase powder and fly ash are then evenly distributed in the slurry and coat the PVA fibers. The tiny fly ash particles attract each other, allowing the treated PVA fibers to bond tightly together, improving the compressive strength and crack resistance of the concrete. However, this process still uses traditional polycarboxylate superplasticizers, which are easily adsorbed and degraded by clay.
[0005] Chinese Patent Publication No. CN118405889A discloses a crack-resistant, long-life fiber-reinforced concrete and its preparation process. This addresses the relatively high cost of using steel fibers alone or in combination with polyimide fibers, the difficulty in uniformly dispersing these fibers in concrete, the inability to overcome some of the drawbacks of steel fibers, and the potential irritation to the respiratory system and skin. The raw materials include: 176 parts water, 910 parts river sand, 726 parts crushed stone, 356 parts fly ash silicate cement, 4.6 parts basalt fiber, 23.5 parts steel fiber, 18 parts silica fume, 0.347-1.39 parts high-efficiency water-reducing agent, 10.68-21.36 parts composite early-strength agent, 28.48-42.72 parts expansion agent, and 1.78-14.24 parts quick-setting agent. This invention utilizes the combined use of basalt fiber and steel fiber, leveraging the high modulus and high tensile strength of steel fiber to prevent crack propagation. It also overcomes the drawbacks of steel fiber, such as clumping during mixing, difficulty in mixing, difficulty in application, susceptibility to corrosion, poor durability, and high weight. The two complement each other. However, this process still cannot solve the problem of concrete water-reducing agent failure in environments with high mud and gravel content, and it cannot simultaneously address the issues of resistance to chloride ion penetration and alkali corrosion. Summary of the Invention
[0006] Therefore, in view of the above problems, the present invention provides a crack-resistant concrete and its production process, which solves the problems of concrete water-reducing agent failure, high cracking risk and insufficient durability in high mud and gravel environments.
[0007] To achieve the above objectives, the present invention adopts the following technical solution:
[0008] A crack-resistant concrete is composed of the following raw materials in parts by weight: 280-420 parts inorganic cementitious system, 600-700 parts fine aggregate, 950-1050 parts coarse aggregate, 120-150 parts mixing water, 0.6-1.0 parts composite water-reducing agent, 1.2-1.8 parts modified magnesium aluminum hydrotalcite, 0.05-0.12 parts alkali-resistant reinforcing fiber, and 0.2-0.4 parts potassium stearate;
[0009] The inorganic cementitious system includes a silicate cementitious component and an auxiliary cementitious component. The auxiliary cementitious component is a mixture of steel slag powder and zeolite powder in a mass ratio of (1-2):1. The mass ratio of the silicate cementitious component to the auxiliary cementitious component is (3-5):1. The silicate cementitious component is ordinary silicate cement.
[0010] The composite water-reducing agent has a core-shell structure, including a shell layer and a core layer. The shell layer is a polymer network copolymerized from acrylamide, acrylic acid and light-colored N-acyl amino acid phosphate salts, and the core layer is modified Bayer process white mud.
[0011] The modified magnesium aluminum hydrotalcite comprises the following raw materials: magnesium chloride, aluminum sulfate, potassium hydroxide, nano-SiO2, γ-aminopropyltriethoxysilane, isopropanol, and ethylene glycol.
[0012] The alkali-resistant reinforcing fiber is a carbon nanotube with an organosilicon coating on its surface. The organosilicon coating is composed of methyl silicone resin, silver nanowires, graphene oxide, and mercaptosilane.
[0013] Furthermore, the preparation method of the composite water-reducing agent includes the following steps:
[0014] a. Disperse Bayer process white mud in a mixed solution of ethanol and water. Add phytic acid and calcium gluconate at a mass ratio of 1:(0.05-0.15):(0.1-0.2). Carry out a mineralization reaction at room temperature and pressure for 1-3 hours to form a white microsphere carrier with a passivated surface, and obtain modified Bayer process white mud.
[0015] b. Using tall oil as a hydrophobic raw material, tall oil and L-lysine are subjected to amidation reaction according to a molar ratio of tall oil to L-lysine of 1:(1-1.2), followed by phosphorylation modification to obtain light-colored N-acyl amino acid phosphate salt.
[0016] c. The white microsphere carrier obtained in step a and the light-colored N-acyl amino acid phosphate salt obtained in step S2 are dispersed together in a polycarboxylic acid mother liquor. Acrylamide and acrylic monomer are added, and graft copolymerization is carried out on the surface of the white microsphere carrier by a free radical initiator. The mass ratio of the white microsphere carrier, the light-colored N-acyl amino acid phosphate salt, the acrylamide and the acrylic monomer are (5-10):(1-3):(2-5):(1-3). After the graft copolymerization reaction is completed, a polymer network is formed to obtain a composite water-reducing agent.
[0017] Bayer process white mud is a residue produced during the Bayer process of alumina production. It is light in color, appearing as white or light gray, and contains fewer coloring impurities such as iron oxide. Compared with Bayer process red mud, it has the advantage of not easily turning red.
[0018] Sand and gravel are essential raw materials for making concrete. Currently, the quality of sand and gravel on the market is deteriorating, with higher mud content. Polycarboxylate superplasticizers are extremely sensitive to the clay content in aggregates, as clay reduces their water-reducing and dispersing effects and increases economic losses. Therefore, this technical solution prepares a composite superplasticizer with anti-mud properties, which is a modified polycarboxylate superplasticizer.
[0019] First, the polymer network formed after the graft copolymerization reaction creates a dense hydration film in the early stages of hydration, hindering the intercalation and adsorption of the water-reducing agent by the clay. The polymer network in the shell contains light-colored N-acyl amino acid phosphate salts, synthesized from tall oil and L-lysine. These light-colored N-acyl amino acid phosphate salts are a special amphoteric molecule with long-chain hydrophobic tails and amphiphilic head groups (amino acid and phosphate).
[0020] (1) The phosphate group of this molecule can be adsorbed on the surface of clay, and the phosphate ester group (-PO3) 2- It exhibits a strong complexing ability for calcium ions and aluminum oxide octahedra on clay surfaces. In muddy environments, it preferentially binds to active sites on the surface of clay particles, forming a stable adsorption layer that blocks the interlayer of clay. This is used for adsorbing carboxyl groups (-COO) in traditional polycarboxylic acid molecules. - The channels of the clay significantly reduce the ineffective adsorption and consumption of carboxyl groups on the main chain of the water-reducing agent by the clay. The phosphate ester molecules adsorbed on the surface of the clay have their hydrophilic ends facing outward, which can increase the negative charge and steric hindrance of the clay particles, making them more stable in water and less prone to aggregation, thereby reducing the damage to the overall fluidity of the slurry.
[0021] (2) Its long-chain hydrophobic tails extend outward to form a dense hydrophobic molecular film on the surface of clay particles. This hydrophobic film can effectively block free water molecules from entering the layered structure of clay, thereby fundamentally inhibiting the rapid loss of slurry fluidity caused by the expansion of clay due to water absorption.
[0022] (3) At the same time, its hydrophilic head group can change the electrical properties of the clay surface, enhance the electrostatic repulsion between particles, and assist in dispersion.
[0023] Secondly, the main component of Bayer process white clay is hydrated aluminosilicate, which has a certain layered structure and high specific surface area. After mineralization treatment with phytic acid and calcium gluconate, a dense passivation layer is formed on its surface. This passivation layer wraps around the core layer surface, masking a large number of active adsorption sites of Bayer process white clay itself. This makes it less likely to undergo strong ion exchange or intercalation adsorption with clay when it encounters clay, thereby reducing the risk of failure due to being heavily wrapped by clay.
[0024] Furthermore, the preparation process of the modified magnesium aluminum hydrotalcite is as follows:
[0025] I. Dissolve MgCl2 and Al2(SO4)3 in deionized water at a molar ratio of (1.5-2.5):1, add potassium hydroxide and nano-SiO2, and perform hydrothermal reaction at 100℃-140℃ for 8-16 hours to form a precursor.
[0026] II. Dissolve the silane coupling agent γ-aminopropyltriethoxysilane in a mixed solution of isopropanol and ethylene glycol, stir until homogeneous, and prepare a silane mixed solution with a mass concentration of 3%-8%.
[0027] III. The precursor prepared in step I is ultrasonically dispersed using the silane mixed solution obtained in step II. After ultrasonic dispersion, the precursor is filtered and the filter cake is washed with isopropanol 2-3 times. The filter cake is then placed in a vacuum drying oven and dried at 60℃-90℃. After grinding through a 200-mesh sieve, modified magnesium aluminum hydrotalcite is obtained.
[0028] When modified magnesium aluminum hydrotalcite (LDHs) is incorporated into concrete, the silane coupling agent-modified LDHs are uniformly dispersed in the cementitious system with the assistance of modified polycarboxylate superplasticizer (composite superplasticizer). Simultaneously, the nano-SiO2 incorporated during the preparation process fills the capillary pores of the concrete, reducing Cl- concentration. - Infiltration channels; when free Cl exists in concrete - At that time, Cl - It can react with the existing anions (such as SO42-) in the interlayer domain of LDHs. 2- An ion exchange reaction occurs, transferring Cl... - Fixed in the interlayer domain, preventing Cl - Migration; silane coupling agents are grafted onto the surface of LDHs through Si-OM bonds to form a functional layer, which works synergistically with the polyether chains of the modified polycarboxylate superplasticizer through hydrogen bonding and hydrophobic interactions to prevent LDHs from agglomerating or peeling off at the interface; at the same time, the Si-OM bonded layer resists the erosion of concrete in a high-alkaline environment (pH>12) and improves the long-term durability of concrete against chloride ion corrosion.
[0029] Furthermore, the preparation process of the alkali-resistant reinforced fiber is as follows:
[0030] (1) Dissolve methyl silicone resin in a mixed solvent of ethanol and water, add silver nanowires, graphene oxide and mercaptosilane coupling agent in sequence, and treat with a high-speed shear emulsifier for 15 min-20 min at 60℃-80℃ to form a uniform mixed slurry.
[0031] (2) Add carbon nanotubes to the mixed slurry prepared in step (1), disperse it by ultrasonication, and then separate the solid and liquid by centrifugation. Discard the supernatant and place the collected solid precipitate in a vacuum drying oven and dry it at 80℃-100℃ for 6h-8h to obtain alkali-resistant reinforced fiber.
[0032] The amount of silver nanowires added is 5%-10% of the mass of methyl silicone resin, the amount of graphene oxide added is 1%-3% of the mass of methyl silicone resin, and the amount of mercaptosilane coupling agent added is 3%-6% of the mass of methyl silicone resin.
[0033] When carbon nanotubes are uniformly dispersed in a concrete matrix, they can overlap to form a three-dimensional network, bridging both sides of the crack, effectively transferring and dispersing stress, and consuming the energy for crack propagation, thereby significantly inhibiting the development of microcracks into larger cracks. After curing, methyl silicone resin forms a dense, hydrophobic, and chemically stable siloxane (Si-O-Si) network, which can effectively block the erosion of alkaline ions and water molecules.
[0034] Furthermore, the auxiliary cementitious component also contains waste ceramic powder, the amount of which is 5%-8% of the total mass of steel slag powder and zeolite powder.
[0035] Furthermore, in step a: the volume fraction of ethanol in the mixed solution of ethanol and water is 30%-50%; the pH value of the mineralization reaction is controlled at 6.5-7.5.
[0036] Furthermore, in step b: the phosphorylation reagent used for the phosphorylation modification is phosphorus pentoxide.
[0037] The above-described production process for crack-resistant concrete includes the following steps:
[0038] S1. Premixing of cementitious materials: Add silicate cementitious components, steel slag powder and zeolite powder into a mixer and dry mix for 60s-90s to form an inorganic cementitious system.
[0039] S2, Dispersion of functional components: Add composite water-reducing agent, modified magnesium aluminum hydrotalcite and alkali-resistant reinforcing fiber to the inorganic cementitious system obtained in step S1, and continue to dry mix for 30s-60s to make each functional component evenly dispersed.
[0040] S3. Mixing coarse and fine aggregates: Put fine aggregates and coarse aggregates into a mixer and premix for 30-60 seconds;
[0041] S4. Wet mixing and molding: Add mixing water and potassium stearate to the mixer in step S3, mix for 90s-120s, then pour the concrete mixture into the mold and compact it.
[0042] S5. Curing: Curing the formed concrete to obtain crack-resistant concrete.
[0043] By adopting the aforementioned technical solution, the beneficial effects of the present invention are as follows:
[0044] This technical solution addresses the problems of concrete water-reducing agent failure, high cracking risk, and insufficient durability in environments with high mud and gravel content, achieving a significant improvement in crack prevention performance and overall durability. Its core lies in using an anti-mud composite water-reducing agent to reduce clay adsorption, using modified magnesium aluminum hydrotalcite to block chloride ion erosion, and using toughened alkali-resistant reinforcing fibers to inhibit microcrack propagation. Detailed Implementation
[0045] Example 1
[0046] A crack-resistant concrete is composed of the following raw materials in parts by weight: 300 parts inorganic cementitious system, 650 parts fine aggregate, 1000 parts coarse aggregate, 130 parts mixing water, 0.8 parts composite water-reducing agent, 1.5 parts modified magnesium aluminum hydrotalcite, 0.08 parts alkali-resistant reinforcing fiber, and 0.3 parts potassium stearate; wherein the fine aggregate is artificial sand and the coarse aggregate is crushed stone;
[0047] The inorganic cementitious system comprises a silicate cementitious component and an auxiliary cementitious component. The auxiliary cementitious component is a mixture of steel slag powder and zeolite powder in a mass ratio of 1:1. The mass ratio of the silicate cementitious component to the auxiliary cementitious component is 3:1. The silicate cementitious component is ordinary silicate cement. Waste ceramic powder is also added to the auxiliary cementitious component at a concentration of 5% of the total mass of the steel slag powder and zeolite powder.
[0048] The composite water-reducing agent has a core-shell structure, including a shell layer and a core layer. The shell layer is a polymer network copolymerized from acrylamide, acrylic acid and light-colored N-acyl amino acid phosphate salts, and the core layer is modified Bayer process white mud.
[0049] The modified magnesium aluminum hydrotalcite comprises the following raw materials: magnesium chloride, aluminum sulfate, potassium hydroxide, nano-SiO2, γ-aminopropyltriethoxysilane, isopropanol, and ethylene glycol.
[0050] The alkali-resistant reinforcing fiber is a carbon nanotube with an organosilicon coating on its surface. The organosilicon coating is composed of methyl silicone resin, silver nanowires, graphene oxide, and mercaptosilane.
[0051] The above-described production process for crack-resistant concrete includes the following steps:
[0052] S1. Premixing of cementitious materials: Add silicate cementitious components, steel slag powder and zeolite powder into a mixer and dry mix for 70 seconds to form an inorganic cementitious system.
[0053] S2, Dispersion of functional components: Add composite water-reducing agent, modified magnesium aluminum hydrotalcite and alkali-resistant reinforcing fiber to the inorganic cementitious system obtained in step S1, and continue to dry mix for 45s to make each functional component evenly dispersed.
[0054] S3. Mixing coarse and fine aggregates: Put fine aggregates and coarse aggregates into a mixer and premix for 45 seconds;
[0055] S4. Wet mixing and molding: Add mixing water and potassium stearate to the mixer in step S3, mix for 120 seconds, then pour the concrete mixture into the mold and compact it.
[0056] S5. Curing: Curing the formed concrete to obtain crack-resistant concrete.
[0057] The preparation method of the composite water-reducing agent includes the following steps:
[0058] a. Bayer process white mud is dispersed in a mixed solution of ethanol and water. Phytic acid and calcium gluconate are added at a mass ratio of Bayer process white mud to phytic acid and calcium gluconate of 1:0.1:0.15. The mineralization reaction is carried out at room temperature and pressure for 2 hours to form a white microsphere carrier with a passivated surface, thus obtaining modified Bayer process white mud. The volume fraction of ethanol in the mixed solution of ethanol and water is 30%. The pH value of the mineralization reaction is controlled at 7.0.
[0059] b. Using tall oil as a hydrophobic raw material, tall oil and L-lysine are subjected to an amidation reaction at a molar ratio of 1:1, followed by phosphorylation modification to obtain a light-colored N-acyl amino acid phosphate salt; the phosphorylation reagent used for the phosphorylation modification is phosphorus pentoxide.
[0060] c. The white microsphere carrier obtained in step a and the light-colored N-acyl amino acid phosphate salt obtained in step S2 are dispersed together in a polycarboxylic acid mother liquor. Acrylamide and acrylic monomer are added, and graft copolymerization is carried out on the surface of the white microsphere carrier using a free radical initiator. The mass ratio of the white microsphere carrier, light-colored N-acyl amino acid phosphate salt, acrylamide and acrylic monomer are 5:1:2:1. After the graft copolymerization reaction is completed, a polymer network is formed to obtain a composite water-reducing agent.
[0061] The preparation process of the modified magnesium aluminum hydrotalcite is as follows:
[0062] I. Dissolve MgCl2 and Al2(SO4)3 in deionized water at a molar ratio of 2:1, add potassium hydroxide and nano-SiO2, and hydrothermally react at 120℃ for 12h to form a precursor;
[0063] II. Dissolve the silane coupling agent γ-aminopropyltriethoxysilane in a mixed solution of isopropanol and ethylene glycol, stir until homogeneous, and prepare a silane mixed solution with a mass concentration of 5%.
[0064] III. The precursor prepared in step I is ultrasonically dispersed using the silane mixed solution obtained in step II. After ultrasonic dispersion, the precursor is filtered and the filter cake is washed three times with isopropanol. The filter cake is then dried in a vacuum drying oven at 60°C and ground through a 200-mesh sieve to obtain modified magnesium aluminum hydrotalcite.
[0065] The preparation process of the alkali-resistant reinforced fiber is as follows:
[0066] (1) Dissolve methyl silicone resin in a mixed solvent of ethanol and water, and add silver nanowires, graphene oxide and mercaptosilane coupling agent in sequence. At 60°C, treat with a high-speed shear emulsifier for 20 min to form a uniform mixed slurry.
[0067] (2) Add carbon nanotubes to the mixed slurry prepared in step (1), disperse it by ultrasonication, and then separate the solid and liquid by centrifugation. Discard the supernatant and place the collected solid precipitate in a vacuum drying oven and dry it at 80°C for 8 hours to obtain alkali-resistant reinforced fiber.
[0068] The amount of silver nanowires added is 5% of the mass of methyl silicone resin, the amount of graphene oxide added is 1% of the mass of methyl silicone resin, and the amount of mercaptosilane coupling agent added is 3% of the mass of methyl silicone resin.
[0069] Example 2
[0070] The difference from Example 1 is as follows:
[0071] A crack-resistant concrete is composed of the following raw materials in parts by weight: 380 parts inorganic cementitious system, 680 parts fine aggregate, 1020 parts coarse aggregate, 140 parts mixing water, 0.9 parts composite water-reducing agent, 1.6 parts modified magnesium aluminum hydrotalcite, 0.1 parts alkali-resistant reinforcing fiber, and 0.35 parts potassium stearate; wherein the fine aggregate is artificial sand and the coarse aggregate is crushed stone;
[0072] The inorganic cementitious system comprises a silicate cementitious component and an auxiliary cementitious component. The auxiliary cementitious component is a mixture of steel slag powder and zeolite powder in a mass ratio of 1.5:1. The mass ratio of the silicate cementitious component to the auxiliary cementitious component is 4:1. The silicate cementitious component is ordinary silicate cement. Waste ceramic powder is also added to the auxiliary cementitious component at a mass ratio of 6% of the total mass of the steel slag powder and zeolite powder.
[0073] In the preparation of the composite water-reducing agent:
[0074] The mass ratio of Bayer process white mud to phytic acid and calcium gluconate is 1:0.12:0.18; the molar ratio of tall oil to L-lysine is 1:1.2; and the mass ratio of white microsphere carrier, light-colored N-acyl amino acid phosphate salt, acrylamide and acrylic acid monomer is 8:2:3:3.
[0075] In the preparation of the modified magnesium aluminum hydrotalcite: the molar ratio of MgCl2 and Al2(SO4)3 is 1.5:1;
[0076] In the preparation of the alkali-resistant reinforced fiber: the amount of silver nanowires added is 8% of the mass of methyl silicone resin; the amount of graphene oxide added is 2% of the mass of methyl silicone resin; and the amount of mercaptosilane coupling agent added is 4% of the mass of methyl silicone resin.
[0077] Other technical solutions are the same as in Example 1.
[0078] Example 3
[0079] The difference from Example 1 is as follows:
[0080] A crack-resistant concrete is composed of the following raw materials in parts by weight: 400 parts inorganic cementitious system, 700 parts fine aggregate, 1050 parts coarse aggregate, 150 parts mixing water, 1.0 part composite water-reducing agent, 1.8 parts modified magnesium aluminum hydrotalcite, 0.12 parts alkali-resistant reinforcing fiber, and 0.4 parts potassium stearate; wherein the fine aggregate is artificial sand and the coarse aggregate is crushed stone;
[0081] The inorganic cementitious system comprises a silicate cementitious component and an auxiliary cementitious component. The auxiliary cementitious component is a mixture of steel slag powder and zeolite powder in a mass ratio of 2:1. The mass ratio of the silicate cementitious component to the auxiliary cementitious component is 5:1. The silicate cementitious component is ordinary silicate cement. Waste ceramic powder is also added to the auxiliary cementitious component at a rate of 6% of the total mass of the steel slag powder and zeolite powder.
[0082] In the preparation of the composite water-reducing agent:
[0083] The mass ratio of Bayer process white mud to phytic acid and calcium gluconate is 1:0.15:0.2; the molar ratio of tall oil to L-lysine is 1:1.2; the mass ratio of white microsphere carrier, light-colored N-acyl amino acid phosphate salt, acrylamide and acrylic acid monomer are 10:3:5:3, respectively.
[0084] In the preparation of the modified magnesium aluminum hydrotalcite: the molar ratio of MgCl2 and Al2(SO4)3 is 2.5:1;
[0085] In the preparation of the alkali-resistant reinforced fiber: the amount of silver nanowires added is 10% of the mass of methyl silicone resin; the amount of graphene oxide added is 3% of the mass of methyl silicone resin; and the amount of mercaptosilane coupling agent added is 7% of the mass of methyl silicone resin.
[0086] Other technical solutions are the same as in Example 1.
[0087] Comparative Example 1
[0088] The difference from Example 1 is as follows:
[0089] No composite water-reducing agent, modified magnesium aluminum hydrotalcite, or alkali-resistant reinforcing fiber are added to the raw materials; the water-reducing agent used is a commercially available and well-known polycarboxylate water-reducing agent. Other technical solutions are the same as in Example 1.
[0090] Comparative Example 2
[0091] The difference from Example 1 is as follows:
[0092] No composite water-reducing agent or alkali-resistant reinforcing fiber is added to the raw materials; the water-reducing agent used is a commercially available and well-known polycarboxylate water-reducing agent. Other technical solutions are the same as in Example 1.
[0093] Comparative Example 3
[0094] No composite water-reducing agent is added to the raw materials. The water-reducing agent used is a commercially available, well-known polycarboxylate water-reducing agent. Other technical solutions are the same as in Example 1.
[0095] The composite water-reducing agents and crack-resistant concrete prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were tested, and the test results are shown in Table 1.
[0096] Table 1
[0097]
[0098] Water reduction rate: The water reduction rate of the water-reducing agent was tested in accordance with the national standard GB 8076-2008 "Concrete Admixtures".
[0099] Slump: The slump of the concrete to be dispersed with water-reducing agent was tested in accordance with the national standard GB / T 50080-2016.
[0100] Mud resistance performance: Prepare cement paste containing different proportions of mud powder, measure the slump of the mixture after standing for 1 hour, and calculate the difference between the slump and the initial slump, i.e., slump loss.
[0101] Chloride ion penetration prevention: Refer to section 7.1 of GB / T 50082-2024 "Standard for Test Methods of Long-term Performance and Durability of Concrete" for the Rapid Chloride Ion Migration Coefficient Method (RCM Method).
[0102] Compressive strength: Concrete test blocks containing the water-reducing agent to be tested were tested in accordance with the national standard GB / T 50081-2019.
[0103] Maximum crack width induced by flat plate: Flat plate concrete specimens were prepared and cured under constrained conditions; after the initial cracks appeared on the surface of the specimens, the maximum crack width was measured with vernier calipers.
[0104] As can be seen from Table 1, the crack-resistant concrete prepared by this technical solution has excellent performance in terms of water reduction rate, workability retention (resistance to mud slump loss), durability (resistance to chloride ion penetration), mechanical properties (compressive strength) and crack resistance (slab-induced cracking).
[0105] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.
Claims
1. A crack-resistant concrete, characterized in that, It is composed of the following raw materials in parts by weight: 280-420 parts inorganic cementitious system, 600-700 parts fine aggregate, 950-1050 parts coarse aggregate, 120-150 parts mixing water, 0.6-1.0 parts composite water-reducing agent, 1.2-1.8 parts modified magnesium aluminum hydrotalcite, 0.05-0.12 parts alkali-resistant reinforcing fiber, and 0.2-0.4 parts potassium stearate; The inorganic cementitious system includes a silicate cementitious component and an auxiliary cementitious component. The auxiliary cementitious component is a mixture of steel slag powder and zeolite powder in a mass ratio of (1-2):
1. The mass ratio of the silicate cementitious component to the auxiliary cementitious component is (3-5):
1. The silicate cementitious component is ordinary silicate cement. The composite water-reducing agent has a core-shell structure, including a shell layer and a core layer. The shell layer is a polymer network copolymerized from acrylamide, acrylic acid and light-colored N-acyl amino acid phosphate salts, and the core layer is modified Bayer process white mud. The modified magnesium aluminum hydrotalcite comprises the following raw materials: magnesium chloride, aluminum sulfate, potassium hydroxide, nano-SiO2, γ-aminopropyltriethoxysilane, isopropanol, and ethylene glycol. The alkali-resistant reinforcing fiber is a carbon nanotube with an organosilicon coating on its surface. The organosilicon coating is composed of methyl silicone resin, silver nanowires, graphene oxide and mercaptosilane. The preparation method of the composite water-reducing agent includes the following steps: a. Disperse Bayer process white mud in a mixed solution of ethanol and water. Add phytic acid and calcium gluconate at a mass ratio of 1:(0.05-0.15):(0.1-0.2). Carry out a mineralization reaction at room temperature and pressure for 1-3 hours to form a white microsphere carrier with a passivated surface, and obtain modified Bayer process white mud. b. Using tall oil as a hydrophobic raw material, tall oil and L-lysine are subjected to amidation reaction according to a molar ratio of tall oil to L-lysine of 1:(1-1.2), followed by phosphorylation modification to obtain light-colored N-acyl amino acid phosphate salt. c. The white microsphere carrier obtained in step a and the light-colored N-acyl amino acid phosphate salt obtained in step S2 are dispersed together in a polycarboxylic acid mother liquor. Acrylamide and acrylic acid monomer are added, and graft copolymerization is carried out on the surface of the white microsphere carrier by a free radical initiator. The mass ratio of the white microsphere carrier, the light-colored N-acyl amino acid phosphate salt, the acrylamide and the acrylic acid monomer are (5-10):(1-3):(2-5):(1-3). After the graft copolymerization reaction is completed, a polymer network is formed to obtain a composite water-reducing agent.
2. The anti-cracking concrete according to claim 1, wherein The preparation process of the modified magnesium aluminum hydrotalcite is as follows: I. Dissolve MgCl2 and Al2(SO4)3 in deionized water at a molar ratio of (1.5-2.5):1, add potassium hydroxide and nano-SiO2, and perform hydrothermal reaction at 100℃-140℃ for 8-16 hours to form a precursor. II. Dissolve the silane coupling agent γ-aminopropyltriethoxysilane in a mixed solution of isopropanol and ethylene glycol, stir until homogeneous, and prepare a silane mixed solution with a mass concentration of 3%-8%. III. The precursor prepared in step I is ultrasonically dispersed using the silane mixed solution obtained in step II. After ultrasonic dispersion, the precursor is filtered and the filter cake is washed with isopropanol 2-3 times. The filter cake is then placed in a vacuum drying oven and dried at 60℃-90℃. After grinding through a 200-mesh sieve, modified magnesium aluminum hydrotalcite is obtained.
3. The anti-cracking concrete according to claim 1, wherein The preparation process of the alkali-resistant reinforced fiber is as follows: (1) Dissolve methyl silicone resin in a mixed solvent of ethanol and water, add silver nanowires, graphene oxide and mercaptosilane coupling agent in sequence, and treat with a high-speed shear emulsifier for 15 min-20 min at 60℃-80℃ to form a uniform mixed slurry. (2) Add carbon nanotubes to the mixed slurry prepared in step (1), disperse it by ultrasonication, and then separate the solid and liquid by centrifugation. Discard the supernatant and place the collected solid precipitate in a vacuum drying oven and dry it at 80℃-100℃ for 6h-8h to obtain alkali-resistant reinforced fiber. The amount of silver nanowires added is 5%-10% of the mass of methyl silicone resin, the amount of graphene oxide added is 1%-3% of the mass of methyl silicone resin, and the amount of mercaptosilane coupling agent added is 3%-6% of the mass of methyl silicone resin.
4. The anti-cracking concrete according to claim 1, wherein: The auxiliary cementitious component also contains waste ceramic powder, the amount of which is 5%-8% of the total mass of steel slag powder and zeolite powder.
5. The anti-cracking concrete according to claim 1, characterized in that, In step a: the volume fraction of ethanol in the mixed solution of ethanol and water is 30%-50%; the pH value of the mineralization reaction is controlled at 6.5-7.
5.
6. The anti-cracking concrete according to claim 1, wherein In step b: the phosphorylation reagent used in the phosphorylation modification is phosphorus pentoxide.
7. A process for the production of a non-cracking concrete according to claim 1, characterized in that, Includes the following steps: S1. Premixing of cementitious materials: Add silicate cementitious components, steel slag powder and zeolite powder into a mixer and dry mix for 60s-90s to form an inorganic cementitious system. S2, Dispersion of functional components: Add composite water-reducing agent, modified magnesium aluminum hydrotalcite and alkali-resistant reinforcing fiber to the inorganic cementitious system obtained in step S1, and continue to dry mix for 30s-60s to make each functional component evenly dispersed. S3. Mixing coarse and fine aggregates: Put fine aggregates and coarse aggregates into a mixer and premix for 30-60 seconds; S4. Wet mixing and molding: Add mixing water and potassium stearate to the mixer in step S3, mix for 90s-120s, then pour the concrete mixture into the mold and compact it. S5. Curing: Curing the formed concrete to obtain crack-resistant concrete.