Polycarboxylate water reducer for colored concrete, and preparation method and application thereof
By combining cationic modified polycarboxylate superplasticizer with stabilizer, the problems of pigment agglomeration and rapid slump loss in colored concrete are solved, achieving efficient dispersion and stability of colored concrete, and improving construction effect and durability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HUAXIN CEMENT CO LTD
- Filing Date
- 2026-02-11
- Publication Date
- 2026-05-29
AI Technical Summary
Existing polycarboxylate superplasticizers cannot effectively solve the problems of pigment agglomeration, poor stability, and rapid slump loss in colored concrete, thus affecting the construction effect.
A cationic modified polycarboxylate superplasticizer is combined with a stabilizer, which adsorbs onto the surface of cement and pigment particles through hydrogen bonding and electrostatic repulsion. Combined with polyolefin wax emulsion, it forms a lubricating film, thereby improving the dispersibility and stability of the pigment.
It significantly improves the slump retention and pigment uniformity of colored concrete, reduces color difference and mottling defects, and has good waterproof and anti-aging properties.
Smart Images
Figure SMS_1 
Figure SMS_2
Abstract
Description
Technical Field
[0001] This invention belongs to the field of concrete admixture technology, specifically relating to a polycarboxylate superplasticizer for colored concrete, its preparation method, and its application. Background Technology
[0002] Colored concrete, as a new type of decorative concrete, can effectively solve the problem of poor aesthetic effect of ordinary concrete, realize the diversification of concrete colors, and play a significant role in improving the quality of urban buildings and the living environment. However, during the construction of colored concrete, problems such as pigment agglomeration and difficulty in dispersion are easily caused by factors such as the finer particle size of pigments compared to cement and poor pigment processing performance. In addition, due to the adsorption effect of pigments and impurities on admixtures, colored concrete is prone to having a small initial slump and a large slump loss, which seriously affects the construction of colored concrete.
[0003] The polycarboxylate superplasticizers commonly used in existing admixture technologies mainly improve the initial fluidity of ready-mixed concrete and prevent loss of fluidity during transportation. However, they cannot effectively solve the problems of poor pigment adhesion and stability in colored concrete. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to address the shortcomings of the existing technology by providing a method for preparing and applying a polycarboxylate superplasticizer for colored concrete. The polycarboxylate superplasticizer for colored concrete, which is obtained by compounding a cationic modified polycarboxylate superplasticizer synthesized by polymerization with a stabilizer, can improve the slump retention of colored concrete and avoid problems such as excessive slump loss after pouring. At the same time, it can effectively prevent the sedimentation or agglomeration of colored concrete pigments, improve the stability and uniformity of pigments, and exhibit good waterproof and anti-aging properties.
[0005] To solve the technical problem proposed in this invention, the following technical solution is adopted: A polycarboxylate superplasticizer for colored concrete, comprising the following components by weight: 20-30 parts of cationic modified polycarboxylate superplasticizer and 5-10 parts of stabilizer; wherein the cationic modified polycarboxylate superplasticizer is a free radical copolymer, and the polymer monomers used include unsaturated amide monomers containing cationic groups, unsaturated polyoxyethylene ethers, and unsaturated carboxylic acids.
[0006] In the above scheme, the polymer monomers used in the cationic modified polycarboxylate water-reducing component include, by weight, 5-10 parts of unsaturated amide monomers containing cationic groups, 300-330 parts of unsaturated polyoxyethylene ether, and 20-25 parts of unsaturated carboxylic acid.
[0007] In the above scheme, the unsaturated amide monomer containing cationic groups is dimethyl diallyl ammonium chloride (DMDAAC) modified N,N-dimethylacrylamide (DMAA).
[0008] Furthermore, the preparation steps of the unsaturated amide monomer containing cationic groups include: (1) Dissolve N,N-dimethylacrylamide (DMAA) and dimethyl diallyl ammonium chloride (DMDAAC) cationic quaternary ammonium salt monomers uniformly in water, adjust the pH of the resulting solution system to 5-6 (the most stable range), and stir to mix well; (2) Under an inert atmosphere (nitrogen, etc., the same below), a constant temperature water bath is used to raise the temperature of the solution system to stabilize at 60-65℃; (3) Under an inert atmosphere, add an initiator (such as azobisisobutyric acid hydrochloride), keep stirring at 60-65℃ and 180-220r / min, and copolymerize at a constant temperature for 3.5-4.5h; (4) Cool naturally to room temperature to obtain a pale yellow transparent dispersion of unsaturated amide monomers containing cationic groups.
[0009] In the above scheme, the mass ratio of N,N-dimethylamide to N,N-dimethylamide monomer is 4-5:1.
[0010] In the above scheme, the solid content of the unsaturated amide monomer dispersion containing cationic groups is 20-25%.
[0011] In the above scheme, the amide groups in the unsaturated amide monomer containing cationic groups of the present invention are more polar and have higher polymerization activity. They can combine with active sites such as hydroxyl groups (-OH) on the surface of cement particles through hydrogen bonding and other interactions. Combined with the electrostatic adsorption of the main chain carboxyl groups, a dual effect of "electrostatic repulsion + hydrogen bond adsorption" is formed, which promotes the water-reducing agent molecules to be more firmly adsorbed on the surface of cement particles, reduces desorption, significantly improves slump retention performance, and extends the workability retention time of concrete. The water-reducing component modified with the modified DMAA-based monomer of the present invention can form hydrogen bonds with the polar groups (hydroxyl, amino, etc.) on the surface of most inorganic or organic pigment particles, which helps the water-reducing agent to be adsorbed on the pigment surface, inhibits pigment agglomeration, reduces color difference and mottling defects in colored concrete, and improves color saturation and consistency. The modified DMAA-based monomer described in this invention contains cationic and amide groups that more easily form hydrogen bonds and other interactions with polar groups (hydroxyl, amino, etc.) on the surface of most inorganic or organic pigment particles. This, combined with polyethylene wax emulsion and synergistic water-reducing agent, adsorbs onto the pigment surface, inhibiting pigment aggregation, reducing color difference and mottling defects in colored concrete, and improving color saturation and consistency.
[0012] In the above scheme, the unsaturated polyoxyethylene ether monomer is one or more of methyl allyl alcohol polyoxyethylene ether, isopentenyl alcohol polyoxyethylene ether, isobutylenyl alcohol polyoxyethylene ether, ethylene glycol monovinyl polyethylene glycol ether, etc.; its molecular weight is 2400-3000; preferably isopentenyl alcohol polyoxyethylene ether.
[0013] In the above scheme, the unsaturated carboxylic acid is one or more of acrylic acid, methacrylic acid, maleic anhydride, etc.; preferably acrylic acid.
[0014] In the above scheme, the stabilizer is one or more of polyethylene wax, oxidized polyethylene wax emulsion, etc.; polyethylene wax emulsion is preferred.
[0015] Furthermore, the stabilizer polyethylene wax emulsion has a solid content of 25-30%.
[0016] Furthermore, the polyethylene wax emulsion introduced in this invention exhibits better compatibility with polycarboxylate superplasticizers compared to other polyolefin wax emulsions. It also demonstrates better dispersibility of commonly used inorganic pigments in colored concrete, preventing pigment flocculation. The polyethylene wax exhibits extremely high chemical stability, with its molecular chain free of easily degradable branched chains or ester groups, and demonstrates excellent resistance to ultraviolet radiation and acid / alkali corrosion. Under outdoor conditions such as sun exposure, rain, and temperature fluctuations, the wax film is not prone to aging, yellowing, or chalking, thus providing long-term protection against fading of the colored concrete's color. As a pigment stabilizer, the polyethylene wax adsorbs onto the surface of pigment particles, forming a lubricating film that reduces van der Waals forces between particles, preventing pigment aggregation and improving dispersion stability. When combined with the cationic modified water-reducing component described in this invention, the amide groups of the cationic modified water-reducing component can be adsorbed onto the surface of pigment particles through hydrogen bonds, and the electrostatic repulsion inhibits pigment agglomeration. The polyolefin wax emulsion (or polyethylene wax) forms a lubricating film on the surface of the pigment particles, further reducing the friction between particles. The two work together to make the pigment disperse more evenly in the concrete, reduce color difference and mottling defects, and improve color saturation. At the same time, the cationic modified water-reducing component can optimize the cohesiveness of concrete and reduce problems such as uneven local pigment concentration caused by bleeding. The thixotropic effect of the polyethylene wax emulsion can slow down pigment sedimentation, prolong the workability retention time of fresh concrete, and ensure uniform color during the pouring process.
[0017] In the above scheme, the preparation process of the cationic modified polycarboxylate water-reducing component includes the following steps: stirring and mixing unsaturated polyoxyethylene ether monomer, unsaturated amide monomer containing cationic groups, water and unsaturated carboxylic acid evenly, heating and adding initiator, reducing agent and chain transfer agent to carry out free radical polymerization reaction, and cooling to obtain cationic modified polycarboxylate water-reducing component.
[0018] In the above scheme, the initiator can be at least one of hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, etc.; hydrogen peroxide is preferred.
[0019] Furthermore, the concentration of the hydrogen peroxide is 27-29 wt%.
[0020] In the above scheme, the reducing agent can be one or more of ascorbic acid, sodium bisulfite, ferrous sulfate, etc.; ascorbic acid is preferred.
[0021] In the above scheme, the chain transfer agent can be one or more of mercaptoacetic acid, mercaptopropionic acid, mercaptoethanol, etc.; mercaptopropionic acid is preferred.
[0022] In the above scheme, the polymerization reaction time in the polymerization step is 4-4.5 hours.
[0023] According to the above scheme, the present invention controls the polymerization reaction time of 4-4.5h, which can accurately control the molecular weight of the water-reducing component to 20,000-30,000, and the molecular weight distribution is narrow (dispersion <1.8). This can not only efficiently disperse pigment particles, but also ensure the fluidity of the slurry and avoid surface sanding and mottling. It has both high dispersibility and low cohesion, which is conducive to promoting the efficient application in colored concrete.
[0024] In the above scheme, the polymerization reaction temperature is controlled at 40-43℃ during the polymerization step.
[0025] In the above scheme, when the temperature is above 50℃, the cationic monomer group is easily decomposed, resulting in a decrease in cationicity and a significant reduction in the adsorption and dispersion ability of the water-reducing agent on the pigment. An environment of 40-43℃ can maximize the retention of the activity of the cationic group, ensure its anchoring effect on the pigment particles, and avoid uneven color caused by the failure of the cationic group.
[0026] In the above-mentioned solution, this invention addresses the key pain points of color difference and mottling caused by uneven dispersion of pigments in colored concrete. The copolymerization activity of the introduced cationic monomers is usually lower than that of polyether macromonomers and unsaturated carboxylic acids. If a stepwise dropwise addition method is used, problems such as uneven distribution of cationic groups on the molecular chain are likely to occur (excessive local cationic solubility will over-adsorb pigment particles, while insufficient local solubility will fail to inhibit pigment agglomeration). This invention uses a one-pot method to uniformly mix all monomers (polyoxyethylene ether monomers, cationic monomers, and unsaturated carboxylic acids) in the early stage of the reaction and controls mild initiation conditions to promote simultaneous polymerization. This allows cationic groups to be uniformly grafted onto the main chain of the water-reducing agent molecule, ensuring that the resulting water-reducing component has consistent adsorption capacity for cement particles and pigment particles, thus guaranteeing the color uniformity of colored concrete from the root.
[0027] The preparation method of the above-mentioned polycarboxylate superplasticizer for colored concrete includes the following steps: adding a stabilizer to the cationic modified polycarboxylate superplasticizer component (mother liquor) and mixing evenly to obtain the polycarboxylate superplasticizer for colored concrete.
[0028] The present invention also provides a colored concrete based on the polycarboxylate superplasticizer, wherein the dosage of the polycarboxylate superplasticizer is 2-3% of the weight of the cementitious material in the colored concrete.
[0029] Furthermore, the components and their respective weight percentages in the colored concrete include: 250-300 parts cement, 70-90 parts mineral powder, 150-170 parts water, 15-20 parts pigment, 7-10 parts polycarboxylate superplasticizer for colored concrete, 1050-1100 parts crushed stone, and 800-850 parts sand.
[0030] Furthermore, the cement is PO42.5 ordinary Portland cement.
[0031] Furthermore, the mineral powder is S95 grade mineral powder.
[0032] Furthermore, the pigment is one or more of iron oxide red, iron oxide yellow, iron oxide black, iron oxide brown, etc.; iron oxide red is preferred.
[0033] Furthermore, the particle size of the pigment is 0.2-3 μm.
[0034] Furthermore, the particle size of the crushed stone is 5-25 mm; the fineness modulus of the sand (yellow sand, etc.) is 2.0-2.5.
[0035] Furthermore, the initial slump of the colored concrete reaches 220-230mm, and the spread reaches 550-600mm; the slump after 2 hours reaches 200-220mm, and the spread reaches 500-550mm; after 7 days of soaking in water, there is little or no color seepage, and it has good resistance to ultraviolet aging.
[0036] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) By adopting an initiation system based on the one-pot method and controlling the free radical generation rate, problems such as abnormal cohesiveness of concrete paste, pigment sedimentation, or color difference due to bleeding can be effectively avoided; at the same time, the molecular weight distribution of the product can be effectively controlled to ensure the stability of the paste rheological properties.
[0037] 2) The polycarboxylate superplasticizer system synthesized by using modified DMAA containing cationic monomers can effectively improve the slump retention of concrete and avoid surface sanding caused by excessive slump loss after pouring; it can also optimize the cohesiveness of concrete and reduce bleeding and water migration; the resulting water-reducing components have basically the same adsorption capacity for cement particles and pigment particles, which can ensure the color uniformity of colored concrete from the source, avoid uneven pigment concentration caused by local moisture accumulation, and ensure the uniform color of the colored concrete surface.
[0038] 3) When cationic modified polycarboxylate water-reducing components are combined with stabilizers, the introduced amide and other groups can be adsorbed on the surface of pigment particles through hydrogen bonds, and combined with electrostatic repulsion to inhibit pigment agglomeration; while stabilizing components such as polyolefin wax emulsions will form a lubricating film on the surface of pigment particles, further reducing the friction between particles. The synergistic effect of the two promotes more uniform dispersion of pigments and other components in concrete, significantly reduces color difference and mottling defects, and improves color saturation. Detailed Implementation
[0039] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.
[0040] In the following examples, the method for preparing unsaturated amide monomers containing cationic groups includes the following steps: (1) Add deionized water to a three-necked flask, and add 10 parts (by weight, the same below) of DMAA and 2 parts of DMDAAC monomer in sequence while stirring. Stir until completely dissolved, and adjust the pH of the resulting solution system to 5-6 with dilute acetic acid. Stir and mix well. (2) Under an inert atmosphere (nitrogen purging for more than 15 minutes), a constant temperature water bath is used to raise the temperature of the solution system to stabilize at 60-65℃; (3) Under an inert atmosphere, add 0.02 azobisisobutyric acid hydrochloride (dissolved in a small amount of water first), keep stirring at 60-65℃ and 200r / min, and copolymerize at a constant temperature for 4h; (4) Cool naturally to room temperature to obtain a light yellow transparent dispersion of unsaturated amide monomers containing cationic groups (solid content is 23%).
[0041] The polyethylene wax emulsion used has a solid content of 27% and is from BASF.
[0042] Example 1 A polycarboxylate superplasticizer for colored concrete, the preparation method of which includes the following steps: 1) Take 320 parts of isopentenyl alcohol polyoxyethylene ether (molecular weight 2400) and 300 parts of deionized water into a reactor, start the stirrer, heat to 40-43℃, and stir until completely dissolved; 2) Under stirring, add 2.8 parts of hydrogen peroxide (concentration 27.5wt%), 5 parts of unsaturated amide monomer containing cationic groups (modified DMAA), 24 parts of acrylic acid, 0.45 parts of ascorbic acid, and 1.8 parts of mercaptopropionic acid to the reactor. React at 40-43℃ for 4-4.5 hours. Cool to room temperature to obtain cationic modified polycarboxylate water-reducing component (molecular weight controlled at 20,000-30,000, with narrow molecular weight distribution and dispersion <1.8; the same below). 3) Take 20 parts of the obtained cationic modified polycarboxylate superplasticizer and mix them evenly with 5 parts of polyethylene wax emulsion to obtain the polycarboxylate superplasticizer for colored concrete.
[0043] The polycarboxylate superplasticizer obtained in this embodiment is further applied to the preparation of colored concrete. The specific preparation steps include the following: (1) Weighing of raw materials; each raw material and its weight percentage include: 250 parts of cement (PO42.5 ordinary Portland cement), 80 parts of mineral powder (S95 grade mineral powder), 20 parts of pigment (iron oxide red, particle size of 0.2~2μm), 800 parts of yellow sand (fineness modulus of 2.3), 1050 parts of crushed stone (5-25mm), 170 parts of water, and 7.3 parts of polycarboxylate superplasticizer for colored concrete; (2) First, add the weighed sand, stone and pigment into the mixer and stir for 20-30 seconds. Then add the cement and mineral powder into the mixer and stir for 20-30 seconds. Finally, add the colored concrete polycarboxylate superplasticizer and water into the mixer and stir for 60 seconds. Mix evenly to obtain colored concrete.
[0044] Example 2 A polycarboxylate superplasticizer for colored concrete, the preparation method of which includes the following steps: 1) Take 330 parts of methyl allyl alcohol polyoxyethylene ether (molecular weight 2400) and 300 parts of deionized water into a reactor, start the stirrer, heat to 40-43℃, and stir until completely dissolved; 2) Under stirring, add 3.5 parts ammonium persulfate, 7.5 parts DMAA, 23 parts acrylic acid, 0.49 parts sodium bisulfite, and 1.8 parts mercaptopropionic acid to the reactor and react at 40-43℃ for 4-4.5 hours; cool to room temperature to obtain cationic modified polycarboxylate water-reducing component; 3) Take 20 parts of the obtained cationic modified polycarboxylate superplasticizer and mix them evenly with 5 parts of oxidized polyethylene wax emulsion to obtain the polycarboxylate superplasticizer for colored concrete.
[0045] The polycarboxylate superplasticizer obtained in this embodiment was further applied to the preparation of colored concrete. The specific preparation method was the same as in Example 1, except that the raw materials and their weight proportions included: 260 parts cement, 70 parts mineral powder, 15 parts pigment, 830 parts yellow sand, 1090 parts crushed stone, 168 parts water, and 7.3 parts polycarboxylate superplasticizer for colored concrete; the rest was the same as in Example 1. Example 3 A polycarboxylate superplasticizer for colored concrete, the preparation method of which includes the following steps: 1) Take 345 parts of isopentenyl alcohol polyoxyethylene ether (molecular weight 3000) and 300 parts of deionized water into a reactor, start the stirrer, heat to 40-43℃, and stir until completely dissolved; 2) After the monomer is dissolved in step 1), 3.9 parts of potassium persulfate, 9 parts of DMAA, 22 parts of maleic anhydride, 0.49 parts of sodium bisulfite, and 2 parts of mercaptopropionic acid are added to the reactor under stirring. The reaction is carried out at 40-43℃ for 4-4.5 hours. The mixture is then cooled to room temperature to obtain the cationic modified polycarboxylate superplasticizer. 3) Take 20 parts of the obtained cationic modified polycarboxylate superplasticizer and mix them evenly with 5 parts of oxidized polyethylene wax emulsion to obtain the polycarboxylate superplasticizer for colored concrete.
[0046] The polycarboxylate superplasticizer obtained in this embodiment is further applied to the preparation of colored concrete. The specific preparation method is the same as in Example 1, except that: the raw materials and their weight parts include: 280 parts cement, 88 parts mineral powder, 18 parts pigment, 830 parts yellow sand, 1075 parts crushed stone, 166 parts water, and 8.1 parts polycarboxylate superplasticizer for colored concrete; the rest is the same as in Example 1.
[0047] Example 4 A polycarboxylate superplasticizer for colored concrete, the preparation method of which includes the following steps: 1) Take 330 parts of pentenol polyoxyethylene ether (molecular weight 2500) and 300 parts of deionized water into a reactor, start the stirrer, heat to 40-43℃, and stir until completely dissolved; 2) Under stirring, add 3 parts hydrogen peroxide, 10 parts DMAA, 26 parts acrylic acid, 0.45 parts ascorbic acid, and 2.2 parts mercaptoacetic acid to the reactor and react at 40-43℃ for 4-4.5 hours; cool to room temperature to obtain cationic modified polycarboxylate superplasticizer. 3) Take 20 parts of the obtained cationic modified polycarboxylate superplasticizer and mix them evenly with 5 parts of polyethylene wax emulsion to obtain the polycarboxylate superplasticizer for colored concrete.
[0048] The polycarboxylate superplasticizer obtained in this embodiment is further applied to the preparation of colored concrete. The specific preparation method is the same as in Example 1, except that: the raw materials and their weight parts include: 270 parts cement, 85 parts mineral powder, 15 parts pigment, 830 parts yellow sand, 1070 parts crushed stone, 169 parts water, and 7.8 parts polycarboxylate superplasticizer for colored concrete; the rest is the same as in Example 1.
[0049] Example 5 A polycarboxylate superplasticizer for colored concrete, the preparation method of which includes the following steps: 1) Take 330 parts of pentenol polyoxyethylene ether (molecular weight 2500) and 300 parts of deionized water into a reactor, start the stirrer, heat to 40-43℃, and stir until completely dissolved; 2) Under stirring, add 3 parts hydrogen peroxide, 10 parts DMAA, 26 parts acrylic acid, 0.45 parts ascorbic acid, and 2.2 parts mercaptoacetic acid to the reactor and react at 40-43℃ for 4-4.5 hours; cool to room temperature to obtain cationic modified polycarboxylate superplasticizer. 3) Take 24 parts of the obtained cationic modified polycarboxylate superplasticizer and mix them evenly with 8 parts of polyethylene wax emulsion to obtain the polycarboxylate superplasticizer for colored concrete. The polycarboxylate superplasticizer obtained in this embodiment is further applied to the preparation of colored concrete. The specific preparation method is the same as in Example 1, except that: each raw material and its weight percentage include: 250 parts cement, 80 parts mineral powder, 20 parts pigment, 800 parts yellow sand, 1050 parts crushed stone, 170 parts water, and 7.3 parts polycarboxylate superplasticizer for colored concrete; the rest is the same as in Example 1.
[0050] Example 6 A polycarboxylate superplasticizer for colored concrete, the preparation method of which includes the following steps: 1) Take 330 parts of pentenol polyoxyethylene ether (molecular weight 2500) and 300 parts of deionized water into a reactor, start the stirrer, heat to 40-43℃, and stir until completely dissolved; 2) Under stirring, add 3 parts hydrogen peroxide, 10 parts DMAA, 26 parts acrylic acid, 0.45 parts ascorbic acid, and 2.2 parts mercaptoacetic acid to the reactor and react at 40-43℃ for 4-4.5 hours; cool to room temperature to obtain cationic modified polycarboxylate superplasticizer. 3) Take 28 parts of the obtained cationic modified polycarboxylate superplasticizer and mix them evenly with 9 parts of polyethylene wax emulsion to obtain the polycarboxylate superplasticizer for colored concrete. The polycarboxylate superplasticizer obtained in this embodiment is further applied to the preparation of colored concrete. The specific preparation method is the same as in Example 1, except that: the raw materials and their weight parts include: 255 parts cement, 83 parts mineral powder, 19 parts pigment, 810 parts yellow sand, 1060 parts crushed stone, 170 parts water, and 7.4 parts polycarboxylate superplasticizer for colored concrete; the rest is the same as in Example 1.
[0051] Example 7 A polycarboxylate superplasticizer for colored concrete, the preparation method of which includes the following steps: 1) Take 330 parts of pentenol polyoxyethylene ether (molecular weight 2500) and 300 parts of deionized water into a reactor, start the stirrer, heat to 40-43℃, and stir until completely dissolved; 2) Under stirring, add 3 parts hydrogen peroxide, 10 parts DMAA, 26 parts acrylic acid, 0.45 parts ascorbic acid, and 2.2 parts mercaptoacetic acid to the reactor and react at 40-43℃ for 4-4.5 hours; cool to room temperature to obtain cationic modified polycarboxylate superplasticizer. 3) Take 30 parts of the obtained cationic modified polycarboxylate superplasticizer and mix them evenly with 10 parts of polyethylene wax emulsion to obtain the polycarboxylate superplasticizer for colored concrete. The polycarboxylate superplasticizer obtained in this embodiment is further applied to the preparation of colored concrete. The specific preparation method is the same as in Example 1, except that: each raw material and its weight percentage include: 250 parts cement, 80 parts mineral powder, 20 parts pigment, 800 parts yellow sand, 1050 parts crushed stone, 170 parts water, and 7.3 parts polycarboxylate superplasticizer for colored concrete; the rest is the same as in Example 1.
[0052] Comparative Example 1 A polycarboxylate superplasticizer, the preparation method of which includes the following steps: 1) Take 320 parts of isopentenyl alcohol polyoxyethylene ether (molecular weight 2400) and 300 parts of deionized water into a reactor, start the stirrer, and heat to 40-43℃, stirring until completely dissolved. 2) After the monomer is dissolved in step 1), under stirring, take 2.8 parts of hydrogen peroxide, 24 parts of acrylic acid, 0.45 parts of ascorbic acid and 1.8 parts of mercaptopropionic acid and add them to the reaction vessel. React at 40-43℃ for 4-4.5 hours.
[0053] 3) After cooling the water-reducing agent obtained in step 2) to room temperature, mix 24 parts of the mixture with 8 parts of water until homogeneous to obtain the polycarboxylate water-reducing agent. The rest is the same as in Example 1.
[0054] Comparative Example 2 A polycarboxylate superplasticizer, the preparation method of which includes the following steps: 1) Take 320 parts of isopentenyl alcohol polyoxyethylene ether (molecular weight 2400) and 300 parts of deionized water into a reactor, start the stirrer, and heat to 40-43℃, stirring until completely dissolved. 2) After the monomer is dissolved in step 1), under stirring, take 2.8 parts of hydrogen peroxide, 24 parts of acrylic acid, 0.45 parts of ascorbic acid, 1.8 parts of mercaptopropionic acid, and 10 parts of N,N-dimethylacrylamide (DMAA) and add them to the reactor. React at 40-43℃ for 4-4.5 hours.
[0055] 3) After cooling the water-reducing agent obtained in step 2) to room temperature, take 24 parts and mix them evenly with 8 parts of polyethylene wax emulsion to obtain the polycarboxylate water-reducing agent.
[0056] The preparation method of colored concrete is the same as in Example 1.
[0057] Comparative Example 3 A polycarboxylate superplasticizer, the preparation method of which includes the following steps: 1) Take 330 parts of isopentenyl alcohol polyoxyethylene ether (molecular weight 2400) and 300 parts of deionized water into a reactor, start the stirrer, heat to 40-43℃, and stir until completely dissolved; 2) After the monomer is dissolved in step 1), under stirring, take 3.5 parts of ammonium persulfate, 10 parts of DMAA, 23 parts of acrylic acid, 0.49 parts of sodium bisulfite, and 1.8 parts of mercaptopropionic acid and add them to the reaction vessel. React at 40-43℃ for 4-4.5 hours. 3) After cooling the cationic modified water-reducing agent obtained in step 2) to room temperature, take 24 parts and mix them evenly with 8 parts of polypropylene wax emulsion to obtain the polycarboxylate water-reducing agent.
[0058] The preparation method of colored concrete is the same as in Example 1.
[0059] Comparative Example 4 A polycarboxylate superplasticizer, the preparation method of which includes the following steps: 1) Take 330 parts of isopentenyl alcohol polyoxyethylene ether (molecular weight 2400) and 300 parts of deionized water into a reactor, start the stirrer, heat to 40-43℃, and stir until completely dissolved; 2) After the monomer is dissolved in step 1), under stirring, take 3.5 parts of ammonium persulfate, 10 parts of DMAA, 23 parts of acrylic acid, 0.49 parts of sodium bisulfite, and 1.8 parts of mercaptopropionic acid and add them to the reaction vessel. React at 40-43℃ for 4-4.5 hours. 3) After cooling the cationic modified water-reducing agent obtained in step 2) to room temperature, take 24 parts and mix them evenly with 8 parts of ethylene vinyl acetate copolymer wax emulsion to obtain the polycarboxylate water-reducing agent.
[0060] The preparation method of colored concrete is the same as in Example 1.
[0061] The performance test results of the colored concrete obtained in each embodiment and comparative example are as follows: 1) Working performance; The colored concrete prepared in Examples 1-7 and Comparative Examples 1-4 were subjected to flowability tests in accordance with the "Standard for Test Methods of Performance of Ordinary Concrete Mixtures" GB / T 50080-2016, and the slump and spread were measured. The specific test results are shown in Table 1.
[0062] Table 1. Performance test results of the embodiments and comparative examples.
[0063] Based on Examples 1-7 and Table 1, it can be seen that in Examples 1-5, the initial slump and spread at 2 hours first increased and then remained constant. This is because when the degree of polymerization of the main chain has not reached saturation, the dispersion and slump retention effects of the water-reducing agent are improved with the increase of the amount of cationic modified DMAA; when the amount added reaches the saturation point of the main chain polymerization, the excess will not participate in the polymerization reaction. In Examples 4-7, the initial slump and spread at 2 hours first increased and then remained constant. This is because as the amount of cationic modified water-reducing agent in the polycarboxylate water-reducing agent for colored concrete increases, the dispersion and slump retention effects of the water-reducing agent are improved, but when the amount added reaches the adsorption saturation point of colored concrete, the excess will not participate in the cement hydration reaction.
[0064] Based on Examples 1-5 and Comparative Examples 1-4, and referring to Table 1, it can be seen that Comparative Example 1 is a synthesized ordinary water-reducing agent. The water-reducing agent synthesized by Comparative Example 2, which directly incorporates N,N-dimethylacrylamide (DMAA) monomer, has comparable performance to the ordinary water-reducing agent synthesized in Comparative Example 1. In the colored concrete system, due to the adsorption of the ordinary water-reducing agent by the pigment itself and impurities, the dispersion and slump retention are weak, resulting in smaller initial and 2-hour slump and spread of the colored concrete. Comparative Examples 3 and 4 are polycarboxylate water-reducing agents specifically for colored concrete, formulated by compounding cationic (DMAA) modified water-reducing agents with other polyolefin wax emulsions as stabilizers. The polyolefin wax emulsions have little effect on the dispersion and slump retention performance of the polycarboxylate water-reducing agent.
[0065] 2) Water immersion test and ultraviolet aging test; The water immersion test involved curing the obtained colored concrete for 7 days and then immersing it in water for 10 days.
[0066] The ultraviolet aging test involved curing the obtained colored concrete for 7 days, followed by irradiation with ultraviolet light at 25 degrees Celsius for 10 days.
[0067] The specific performance test results of the colored concrete prepared in Examples 1-7 and Comparative Examples 1-4 are shown in Table 2.
[0068] Table 2. Waterproofing and anti-aging performance test results of the examples and comparative examples.
[0069] As shown in Examples 1-7 of Table 2, with the increase of the amount of cationic modified water-reducing agent and stabilizer polyethylene wax emulsion, the colored concrete showed no color seepage after a long-term water immersion test, effectively preventing pigment sedimentation or agglomeration in the system and improving the stability and uniformity of the pigment. Simultaneously, after prolonged ultraviolet irradiation, there was virtually no fading or minimal fading, ensuring the gloss and durability of the colored concrete.
[0070] As shown in Table 2, Comparative Examples 1-4, the ordinary water-reducing agent synthesized in Comparative Example 1 exhibits poor adhesion and stability to pigments in colored concrete. The water-reducing agent synthesized in Comparative Example 2 performs similarly to the ordinary water-reducing agent synthesized in Comparative Example 1. Although the emulsion, when compounded with polyethylene wax emulsion, provides some stabilization to the pigments in colored concrete, the poor cohesiveness of the concrete results in poor pigment adhesion and uneven pigment concentration in certain areas. Comparative Examples 3 and 4, using other types of polyolefin wax emulsions as stabilizers, show severe fading in UV aging tests. This is because polyethylene wax possesses extremely high chemical stability compared to other polyolefin waxes, its molecular chain does not contain easily degradable branched chains or ester groups, and it exhibits excellent resistance to UV radiation and acid / alkali corrosion. Under outdoor conditions of sun, rain, and temperature fluctuations, the wax film is not prone to aging, yellowing, or chalking, thus providing long-term protection against fading of the colored concrete's color. The polypropylene wax emulsion used in Comparative Example 3 has a branched structure that is prone to breakage under ultraviolet radiation and has poor weather resistance. The ethylene vinyl acetate copolymer wax emulsion used in Comparative Example 4 contains ester groups and is easily hydrolyzed by acids and alkalis, making it unsuitable for harsh outdoor environments.
[0071] In summary, applying the polycarboxylate superplasticizer for colored concrete described in this invention to colored concrete can effectively improve the slump retention of colored concrete, preventing surface sanding caused by excessive slump loss after pouring; it optimizes the cohesiveness of concrete, reduces bleeding and water migration, avoids uneven pigment concentration caused by localized water accumulation, and ensures uniform color on the surface of colored concrete. When the cationic modified polycarboxylate superplasticizer component described in this invention is compounded with the stabilizer polyethylene wax emulsion, the polyolefin wax emulsion forms a lubricating film on the surface of pigment particles, further reducing inter-particle friction. The two work synergistically to allow for more uniform pigment dispersion in concrete, reducing color difference and mottling defects, improving color saturation, and exhibiting good water resistance and anti-aging properties.
[0072] The above embodiments are merely examples for clear illustration and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations, and any obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A polycarboxylate superplasticizer for colored concrete, characterized in that, Based on parts by weight, it comprises the following components: 20-30 parts of cationic modified polycarboxylate superplasticizer and 5-10 parts of stabilizer; the cationic modified polycarboxylate superplasticizer is a free radical copolymer, and the polymer monomers used include unsaturated amide monomers containing cationic groups, unsaturated polyoxyethylene ethers, and unsaturated carboxylic acids.
2. The polycarboxylate superplasticizer for colored concrete according to claim 1, characterized in that, The cationic modified polycarboxylate water-reducing component comprises, by weight, 5-10 parts of unsaturated amide monomers containing cationic groups, 300-330 parts of unsaturated polyoxyethylene ether, and 20-25 parts of unsaturated carboxylic acid.
3. The polycarboxylate superplasticizer for colored concrete according to claim 1, characterized in that, The unsaturated amide monomer containing cationic groups is dimethyl diallyl ammonium chloride modified N,N-dimethylacrylamide.
4. The polycarboxylate superplasticizer for colored concrete according to claim 1, characterized in that, The preparation steps of the unsaturated amide monomer containing cationic groups include: (1) Dissolve N,N-dimethylacrylamide and dimethyldiallylammonium chloride evenly in water, adjust the pH of the resulting solution system to 5-6, and stir to mix well; (2) Under an inert atmosphere, a constant temperature water bath is used to raise the temperature of the solution system to 60-65℃; (3) Under an inert atmosphere, add an initiator, and then copolymerize at a constant temperature of 60-65℃ and 180-220r / min for 3.5-4.5h. (4) Cool naturally to room temperature to obtain a pale yellow transparent dispersion of unsaturated amide monomers containing cationic groups.
5. The polycarboxylate superplasticizer for colored concrete according to claim 1, characterized in that, The unsaturated polyoxyethylene ether monomer is one or more of methyl allyl alcohol polyoxyethylene ether, isopentenol polyoxyethylene ether, isobutylenol polyoxyethylene ether, and ethylene glycol monovinyl polyethylene glycol ether; its molecular weight is 2400-3000; the unsaturated carboxylic acid is one or more of acrylic acid, methacrylic acid, and maleic anhydride.
6. The polycarboxylate superplasticizer for colored concrete according to claim 1, characterized in that, The stabilizer is one or more of polyethylene wax and oxidized polyethylene wax emulsion.
7. The polycarboxylate superplasticizer for colored concrete according to claim 1, characterized in that, The preparation process of the cationic modified polycarboxylate water-reducing component includes the following steps: unsaturated polyoxyethylene ether, unsaturated amide monomer containing cationic groups, water and unsaturated carboxylic acid are stirred and mixed evenly, heated and initiator, reducing agent and chain transfer agent are added to carry out free radical polymerization reaction, and after cooling, cationic modified polycarboxylate water-reducing component is obtained.
8. The polycarboxylate superplasticizer for colored concrete according to claim 1, characterized in that, The polymerization reaction in the polymerization step takes 4-4.5 hours and is carried out at a temperature of 40-43°C.
9. The method for preparing the polycarboxylate superplasticizer for colored concrete according to any one of claims 1 to 8, characterized in that, The process includes the following steps: adding a stabilizer to the cationic modified polycarboxylate water-reducing component and stirring until homogeneous to obtain a polycarboxylate water-reducing agent for colored concrete.
10. A type of colored concrete based on the polycarboxylate superplasticizer for colored concrete according to any one of claims 1 to 8, characterized in that, The dosage of polycarboxylate superplasticizer is 2-3% of the mass of cementitious materials in colored concrete.