Calcium polyacrylate-polyacrylamide composite anti-dispersant for underwater construction and underwater non-dispersible concrete

Abstract

The application discloses a polyacrylate calcium-polyacrylamide composite anti-dispersant for underwater construction and underwater non-dispersed concrete. The composite anti-dispersant comprises component A and component B; the component A is anionic polyacrylamide with a three-dimensional network structure; and the component B is polyacrylate calcium modified by a silane coupling agent. The underwater non-dispersed concrete comprises the following components in parts by weight: cement 50-70 parts, silica fume 8-15 parts, fine aggregate 100-138 parts, quartz powder 20-50 parts, composite anti-dispersant 1-2 parts, polycarboxylic acid water reducing agent 15-25 parts, reinforcing fiber 8-15 parts and water 20-25 parts. The underwater anti-dispersing performance of the concrete and the compressive strength of an underwater formed test piece are improved significantly, the concrete has excellent fluidity and volume stability, the technical problem that the anti-dispersing performance and mechanical properties of the existing underwater concrete are difficult to be considered simultaneously is solved, and the concrete is suitable for various underwater engineering.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a calcium polyacrylate-polyacrylamide composite anti-dispersing agent for underwater construction and underwater non-dispersible concrete. Background Technology

[0002] Underwater non-dispersible concrete significantly increases the cohesiveness of ordinary concrete by adding an anti-dispersant agent (also known as a flocculant), enabling it to resist water erosion when poured directly in water, avoiding cement loss and aggregate segregation, thereby achieving underwater self-leveling and self-compacting construction.

[0003] Currently, commonly used antidispersants mainly include cellulose ethers and polyacrylamides. Among them, polyacrylamide (PAM) antidispersants are widely used due to their good flocculation effect. However, traditional linear polyacrylamide is prone to molecular chain coiling in high ionic strength underwater environments, leading to a decrease in antidispersibility. At the same time, its thickening effect often comes at the cost of fluidity, resulting in poor concrete workability and difficulty in meeting high-standard engineering requirements for water-to-land strength ratio.

[0004] On the other hand, calcium polyacrylate (CPA), as a high-molecular polymer, is commonly used as a mud treatment agent in the oil drilling field, exhibiting excellent water loss reduction and thickening effects. However, its application in concrete materials, especially in underwater non-dispersible concrete, is relatively limited. While existing technologies have used calcium polyacrylate as a single component for concrete modification (e.g., CN117401941B), the synergistic mechanism when it is compounded with polyacrylamide has not been revealed, and it has not been applied to ultra-high performance underwater non-dispersible concrete systems.

[0005] Therefore, how to develop a new type of anti-dispersant agent that can simultaneously impart ultra-high anti-dispersibility, excellent fluidity, and ultra-high mechanical properties to underwater concrete, while reducing shrinkage, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the present invention aims to provide a polyacrylic acid calcium-polyacrylamide composite anti-dispersion agent and underwater non-dispersible concrete for underwater construction, which simultaneously endows the underwater concrete with ultra-high anti-dispersion properties, excellent fluidity and ultra-high mechanical properties, and reduces shrinkage rate.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] This invention provides a calcium polyacrylate-polyacrylamide composite anti-dispersant agent for underwater construction, comprising component A and component B; wherein component A is anionic polyacrylamide; and component B is silane coupling agent modified calcium polyacrylate.

[0009] In some embodiments of the present invention, the mass ratio of component A to component B is 1:0.2-1.

[0010] In some embodiments of the present invention, the polyacrylamide is a copolymer of acrylamide and a functional monomer, wherein the functional monomer is selected from at least one of 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, and allyl-α-D-galactopyranoside.

[0011] In some embodiments of the present invention, the polyacrylamide is anionic polyacrylamide with a three-dimensional network structure and a weight-average molecular weight of 8 million to 20 million.

[0012] In some embodiments of the present invention, the silane coupling agent is at least one of vinyltriethoxysilane, vinyltrimethoxysilane, or γ-methacryloyloxypropyltrimethoxysilane.

[0013] This invention also provides a method for preparing a calcium polyacrylate-polyacrylamide composite anti-dispersant for underwater construction, comprising the following steps:

[0014] Preparation of silane coupling agent modified calcium polyacrylate: Dissolve calcium polyacrylate in warm water at 50-70℃, add silane coupling agent, stir and react to obtain modified calcium polyacrylate solution;

[0015] Composite: Polyacrylamide is dissolved in water to obtain a polyacrylamide solution; the prepared modified calcium polyacrylate solution is mixed with the polyacrylamide solution and stirred evenly to obtain the calcium polyacrylate-polyacrylamide composite anti-dispersant agent for underwater construction.

[0016] In some embodiments of the present invention, the molecular weight of the calcium polyacrylate is 2 million to 5 million, and the calcium content is 8% to 12% by mass.

[0017] The present invention also provides underwater non-dispersible concrete, comprising the following components by weight:

[0018] 50-70 parts cement;

[0019] 8-15 parts silica fume;

[0020] 100-138 parts fine aggregate;

[0021] 20-50 parts quartz powder;

[0022] 1-2 parts of the aforementioned calcium polyacrylate-polyacrylamide composite anti-dispersant agent for underwater construction;

[0023] 15-25 parts of polycarboxylate superplasticizer;

[0024] 8-15 parts of reinforcing fiber;

[0025] 20-25 parts water.

[0026] In some embodiments of the present invention, the cement is P·II 52.5 grade silicate cement; the silica fume contains ≥95% SiO2 and has a specific surface area ≥20m². 2 / g; the fine aggregate is quartz sand with a particle size of 26-110 mesh; the quartz powder has a particle size of 325-800 mesh; the polycarboxylate superplasticizer has a water reduction rate of ≥30%; the reinforcing fiber is at least one of steel fiber, polyvinyl alcohol fiber or basalt fiber.

[0027] In some embodiments of the present invention, the polyacrylamide in the polyacrylic acid-polyacrylamide composite anti-dispersant agent for underwater construction forms a flocculation network through bridging, while the modified polyacrylamide reacts with the Ca produced during cement hydration through the carboxyl groups on its molecular chain. 2+ Complexation occurs.

[0028] The present invention also provides a method for preparing the aforementioned underwater non-dispersible concrete, comprising the following steps:

[0029] Add cement, silica fume, fine aggregate, and quartz powder to a mixer and dry mix for 1-2 minutes to obtain a dry mix.

[0030] The composite anti-dispersant agent, polycarboxylate superplasticizer, and water are mixed and stirred until homogeneous to obtain a mixed solution;

[0031] Add the prepared mixed solution to the dry mixture and continue stirring for 3-5 minutes;

[0032] Evenly sprinkle in the reinforcing fibers and stir for 2-3 minutes to obtain an ultra-high performance underwater non-dispersible concrete mixture.

[0033] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0034] (1) Synergistic effect and excellent anti-dispersion performance: The composite anti-dispersion agent of the present invention combines polyacrylamide (PAM) and modified calcium polyacrylate (CPA). PAM forms a flocculation network through bridging, while CPA reacts with the Ca produced by cement hydration through the carboxyl groups on its molecular chain. 2+ Complexation occurs, enhancing the stability of the network structure; on the other hand, CPA's water loss-reducing properties effectively lock in moisture in the cement paste, resisting underwater erosion. This invention utilizes the synergistic effect of PAM and CPA to achieve a cement loss of ≤0.8% and a suspended solids content of ≤40mg / L in concrete, significantly superior to existing technologies.

[0035] (2) Ultra-high strength, high water-to-land strength ratio: The slow-release Ca of CPA in the composite anti-dispersant of this invention 2+ The effect provides a continuous calcium source for the later hydration of cement, and combined with the silica fume pozzolanic effect, makes the concrete structure more compact. The 28-day compressive strength of underwater-formed specimens can reach over 80 MPa, and the water-to-land strength ratio is ≥90%, achieving ultra-high strength under underwater construction conditions.

[0036] (3) Excellent performance: The long side chain structure of PAM in the composite anti-dispersant agent of the present invention is combined with the dispersing effect of the water-reducing agent, so that the concrete has high cohesiveness while maintaining good fluidity and spread ≥220mm, which meets the requirements of underwater self-leveling construction.

[0037] (4) Good volume stability: The composite anti-dispersion agent of the present invention effectively reduces the loss of moisture inside the concrete and significantly reduces early drying shrinkage. The 28-day drying shrinkage value is ≤400×10 -6 It effectively inhibits underwater structure shrinkage and cracking, thus improving the structure's durability. Attached Figure Description

[0038] Figure 1 This is a bar chart comparing cement loss in embodiments and comparative examples of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0040] In the following examples, all raw materials used are commercially available.

[0041] Example 1

[0042] In this embodiment, the polyacrylamide used is anionic polyacrylamide with a molecular weight of 15 million (acrylamide-acrylic acid copolymer, purchased from Gongyi Jiezhiyuan Water Treatment Materials Co., Ltd. - J-096); the calcium polyacrylate has a molecular weight of 3 million and a calcium content of 10%, purchased from Henan Chengshuo New Material Technology Co., Ltd. - 1688; the silane coupling agent is γ-methacryloyloxypropyltrimethoxysilane (KH570), purchased from Dongguan Kangjin New Material Technology Co., Ltd. - Coupling Agent KH-570; the cement is P·II 52.5 grade silicate cement; the SiO2 content in silica fume is 96%; the fine aggregate is ordinary quartz sand with a particle size of 26-110 mesh; the particle size of the quartz powder is 325-800 mesh; the water reduction rate of the polycarboxylate superplasticizer is 35%, purchased from Kezhijie New Material Group (Guangdong) Co., Ltd. - Point-490UCS; the reinforcing fiber: diameter 0 0.22mm in diameter, 14mm in length, and with a tensile strength greater than 2000MPa. Hook-type ordinary steel fiber.

[0043] The underwater non-dispersible concrete in this embodiment is prepared as follows:

[0044] (1) Preparation of modified calcium polyacrylate: Dissolve 1 part of calcium polyacrylate in 100 parts of warm water at 60°C, add 0.5 parts of KH570, stir and react for 2 minutes to obtain modified calcium polyacrylate solution.

[0045] (2) Preparation of composite anti-dispersant: Dissolve 1 part of modified polyacrylamide in 15 parts of water to obtain a polyacrylamide solution. Mix the modified calcium polyacrylate solution from step (1) with the polyacrylamide solution and stir evenly to obtain a composite anti-dispersant (PAM:CPA mass ratio = 1:1, based on solid content).

[0046] (3) Preparation of ultra-high performance underwater non-dispersible concrete:

[0047] By weight, take 60 parts cement, 10 parts silica fume, 130 parts fine aggregate, and 23 parts quartz powder, add them to a forced mixer, and dry mix for 1 minute.

[0048] Take 2 parts of the composite anti-dispersant agent, 20 parts of the polycarboxylate superplasticizer and 22 parts of water from step (2), mix them evenly to obtain a mixed solution.

[0049] Add the mixed solution to the dry mixture and stir for 4 minutes.

[0050] Evenly sprinkle in 12 parts of steel fiber, then stir for 2 minutes to obtain ultra-high performance underwater non-dispersible concrete mixture.

[0051] Example 2

[0052] The difference from Example 1 is that the ratio of the composite anti-dispersant is adjusted so that the mass ratio of PAM:CPA is 1:0.4.

[0053] Example 3

[0054] The difference from Example 1 is that the ratio of the composite anti-dispersant is adjusted so that the mass ratio of PAM:CPA is 1:0.8.

[0055] Example 4

[0056] The difference from Example 1 is that the polyacrylamide used is an anionic polyacrylamide with a molecular weight of 8 million.

[0057] Example 5

[0058] The difference from Example 1 is that the polyacrylamide used is a copolymer of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid.

[0059] The polyacrylamide used in this embodiment was purchased from Shandong Baomo Biochemical Co., Ltd., and its model is AMPS copolymer.

[0060] Comparative Example 1

[0061] No anti-dispersant was added, and the remaining components and preparation process were the same as in Example 1.

[0062] Comparative Example 2

[0063] Only polyacrylamide (1 part) was added as an anti-dispersant, and the remaining components and preparation process were the same as in Example 1.

[0064] Comparative Example 3

[0065] Only unmodified calcium polyacrylate (1 part) was added as an anti-dispersant, and the remaining components and preparation process were the same as in Example 1.

[0066] Comparative Example 4

[0067] Commercially available cellulose ether anti-dispersant agents were used, with an admixture dosage of 1.5% of the total amount of cementitious materials. The remaining components and preparation process were the same as in Example 1.

[0068] Comparative Example 5

[0069] Only silane coupling agent-modified calcium polyacrylate (preparation process is the same as in Example 1) was added as an anti-dispersant, without adding polyacrylamide.

[0070] Comparative Example 6

[0071] A one-pot method was used to prepare a composite anti-dispersant, which involves mixing and reacting calcium polyacrylate, KH570, and polyacrylamide in a single process.

[0072] Performance testing

[0073] The concrete prepared in the above embodiments and comparative examples was subjected to performance tests, and the test methods are as follows:

[0074] Anti-dispersion property: Refer to DL / T 5117-2000 to determine cement loss and suspended solids content.

[0075] Flowability: Referencing JGJ-T 283-2012 "Technical Specification for Application of Self-Compacting Concrete", the flowability of concrete was tested using the jump table test method to determine the spread of the concrete.

[0076] Mechanical properties: According to GB-T 17671-1999 "Test method for strength of cement mortar (ISO method)", the 7-day and 28-day compressive strength of underwater molded specimens with a curing age of 28 days were determined, and the ratio of water strength to land strength was calculated.

[0077] Table 1 summarizes the test results of suspended solids content, spread, 7-day underwater strength, 28-day underwater strength, and water-to-land strength ratio of the underwater non-dispersible concrete mixtures in each embodiment and comparative example. A bar chart comparing cement loss is shown below. Figure 1 As shown.

[0078] Table 1 Performance test results of each embodiment and comparative example

[0079]

[0080] The test results show that:

[0081] Compared with all comparative examples, the concrete prepared in Examples 1-5 of this invention shows significant advantages in terms of anti-dispersion, mechanical strength and workability. The cement loss and suspended solids content are extremely low, and the 28-day underwater compressive strength exceeds 90 MPa, achieving a perfect combination of ultra-high performance and underwater non-dispersion.

[0082] Compared with Comparative Examples 2 and 3, the effect of using PAM or CPA alone was far less than that of the combination of the two, confirming a significant synergistic effect between PAM and CPA. In particular, the addition of CPA not only improved anti-dispersion properties but also significantly increased later-stage strength and reduced shrinkage.

[0083] As can be seen from Comparative Example 5, although silane coupling agent modification can improve the performance of calcium polyacrylate, it is still far inferior to the PAM-modified CPA compound system in Example 1. This indicates that modified CPA cannot replace the bridging and flocculation effect of PAM; the two functions are complementary and neither can be dispensed with.

[0084] As can be seen from Comparative Example 6, the performance of the antidispersant prepared by the one-pot method (28-day strength 78.4 MPa, suspended solids content 75 mg / L) is better than that of Comparative Examples 2 and 3, but still significantly lower than that of Example 1. This is because in the one-pot method, KH570 preferentially reacts with PAM, resulting in insufficient CPA modification; while the stepwise method of the present invention ensures sufficient CPA modification, forming a more stable composite network structure.

[0085] The above comparison fully demonstrates that: (1) the combination of PAM and modified CPA has a significant synergistic effect; and (2) the stepwise preparation process of this invention is the key to obtaining excellent performance. These two points together highlight the inventiveness of this invention.

[0086] Comparing Example 1 with Comparative Example 4, it can be seen that the performance of the composite anti-dispersant of the present invention far surpasses that of commercially available cellulose ether products.

[0087] In summary, the polyacrylic acid calcium-polyacrylamide composite anti-dispersing agent and the ultra-high performance underwater non-dispersible concrete prepared by the present invention effectively solve the technical problems of underwater concrete in the prior art, such as difficulty in balancing anti-dispersibility and fluidity, low strength, and large shrinkage. It has engineering application value and broad market prospects.

[0088] In the above embodiments, polyacrylamide can also be copolymerized from acrylamide and functional monomers, wherein the functional monomers are selected from at least one of 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, and allyl-α-D-galactopyranoside; the weight-average molecular weight of the polyacrylamide is 8 million to 20 million.

[0089] In the above embodiments, the silane coupling agent is vinyltriethoxysilane or vinyltrimethoxysilane.

[0090] Those skilled in the art will readily understand that the above description is merely an embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A calcium polyacrylate-polyacrylamide composite anti-dispersant agent for underwater construction, characterized in that, It includes component A and component B; component A is polyacrylamide; component B is silane coupling agent modified calcium polyacrylate.

2. The polyacrylic acid calcium-polyacrylamide composite anti-dispersant agent for underwater construction according to claim 1, characterized in that, The mass ratio of component A to component B is 1:0.2-1.

3. The polyacrylic acid calcium-polyacrylamide composite anti-dispersant agent for underwater construction according to claim 1, characterized in that, The polyacrylamide is a copolymer of acrylamide and a functional monomer, wherein the functional monomer is selected from at least one of 2-acrylamido-2-methylpropanesulfonic acid, acrylic acid, and allyl-α-D-galactopyranoside.

4. The polyacrylic acid calcium-polyacrylamide composite anti-dispersant agent for underwater construction according to claim 1 or 3, characterized in that, The polyacrylamide has a weight-average molecular weight of 8 million to 20 million.

5. The polyacrylic acid calcium-polyacrylamide composite anti-dispersant agent for underwater construction according to claim 1, characterized in that, The silane coupling agent is at least one of vinyltriethoxysilane, vinyltrimethoxysilane, or γ-methacryloxypropyltrimethoxysilane.

6. The method for preparing the calcium polyacrylate-polyacrylamide composite anti-dispersant agent for underwater construction according to any one of claims 1 to 5, characterized in that, Includes the following steps: Preparation of silane coupling agent modified calcium polyacrylate: Dissolve calcium polyacrylate in warm water at 50-70℃, add silane coupling agent, stir and react to obtain modified calcium polyacrylate solution. Composite: Polyacrylamide is dissolved in water to obtain a polyacrylamide solution; the prepared modified calcium polyacrylate solution is mixed with the polyacrylamide solution and stirred evenly to obtain the calcium polyacrylate-polyacrylamide composite anti-dispersant agent for underwater construction.

7. Underwater non-dispersible concrete, characterized in that, By weight, it comprises the following components: 50-70 parts cement; 8-15 parts silica fume; 100-138 parts fine aggregate; 20-50 parts quartz powder; 1-2 parts of the calcium polyacrylate-polyacrylamide composite anti-dispersant agent for underwater construction as described in any one of claims 1 to 5; 15-25 parts of polycarboxylate superplasticizer; 8-15 parts of reinforcing fiber; 20-25 parts water.

8. The underwater non-dispersible concrete according to claim 7, characterized in that, The cement is P·II 52.5 grade Portland cement; the silica fume contains ≥95% SiO2 and has a specific surface area ≥20m². 2 / g; the fine aggregate is quartz sand with a particle size of 26-110 mesh; the quartz powder has a particle size of 325-800 mesh; the polycarboxylate superplasticizer has a water reduction rate of ≥30%; the reinforcing fiber is at least one of steel fiber, polyvinyl alcohol fiber or basalt fiber.

9. The underwater non-dispersible concrete according to claim 7, characterized in that, The polyacrylamide-polyacrylamide composite anti-dispersant agent used for underwater construction forms a flocculation network through bridging, while the modified calcium polyacrylamide reacts with the Ca produced during cement hydration through the carboxyl groups on its molecular chain. 2+ Complexation occurs.

10. The method for preparing underwater non-dispersible concrete according to any one of claims 7 to 9, characterized in that, Includes the following steps: Add cement, silica fume, fine aggregate, and quartz powder to a mixer and dry mix for 1-2 minutes to obtain a dry mix. The composite anti-dispersant agent, polycarboxylate superplasticizer, and water are mixed and stirred until homogeneous to obtain a mixed solution; Add the prepared mixed solution to the dry mixture and continue stirring for 3-5 minutes; Evenly sprinkle in the reinforcing fibers and stir for 2-3 minutes to obtain an ultra-high performance underwater non-dispersible concrete mixture.

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