Polycarboxylate superplasticizer concentrate with low sensitivity to unburned carbon in fly ash

Abstract

The present invention relates to a polycarboxylate water-reducing agent mother liquor with low sensitivity to unburned carbon in fly ash. The present invention specifically relates to a polycarboxylate water-reducing agent mother liquor prepared by using cyclohexanecarboxylic acid, dicarboxylic acid and polyethylene glycol diacrylate, etc. The technical key point is that the polycarboxylate water-reducing agent mother liquor prepared by the present invention is prepared by selecting chemical raw materials or chemical reagents for reaction. The polycarboxylate water-reducing agent mother liquor prepared by the present invention has low sensitivity to unburned carbon in fly ash, reduces the adsorption of water-reducing agent, and significantly improves the workability of concrete containing high-carbon fly ash.

Description

Technical Field

[0001] The invention relates to a polycarboxylate water-reducing agent mother liquid with low sensitivity to unburned carbon in fly ash, in particular to a polycarboxylate water-reducing agent mother liquid prepared by using cyclohexanecarboxylic acid, dicarboxylic acid and polyethylene glycol diacrylate. Background Art

[0002] Concrete is mainly composed of cement, auxiliary cementitious materials, sand and gravel aggregates, water reducers and water. Among them, polycarboxylic acid water reducer has the advantages of large water reduction rate, good collapse resistance and outstanding environmental protection performance, and is one of the most widely used water reducers; while fly ash is one of the most commonly used auxiliary cementitious materials in concrete mixing plants. According to actual application, when polycarboxylic acid water reducer is used together with fly ash with high unburned carbon content, the effect of water reducer will be greatly reduced and it is difficult to play a normal role. This is the phenomenon of incompatibility.

[0003] Fly ash is a byproduct of coal combustion, and the main coal-fired technologies include ordinary pulverized coal furnaces and circulating fluidized bed combustion technology. Ordinary pulverized coal furnaces have the advantages of rapid and complete combustion, large capacity, high efficiency, and easy control and adjustment. They have been widely used in the early days. In the past, the so-called "fly ash" was mostly discharged from ordinary pulverized coal furnaces. Compared with pulverized coal furnace combustion technology, circulating fluidized bed coal-fired sulfur fixation technology has the advantages of wide fuel adaptability, environmental protection, low investment, good load regulation performance, high combustion intensity, and strong heat transfer capacity in the furnace. Therefore, my country is vigorously promoting fluidized bed coal-fired sulfur fixation technology. At present, a large number of large and medium-sized fluidized bed boilers have been built and put into use in various places across the country, and many small and medium-sized thermal power plants have also successively adopted fluidized bed boilers as the key technology for technical transformation. Therefore, the amount of fly ash discharged from fluidized bed boilers will increase year by year.

[0004] The combustion temperature in ordinary pulverized coal furnaces is basically above 1200℃, while that in circulating fluidized beds is 850~900℃. The combustion temperature of the latter is significantly lower than that of the former, so the coal particles in the fluidized bed boiler are not burned, resulting in a relatively high content of unburned carbon in the fluidized bed fly ash. After consulting relevant literature and based on our investigation, the loss on ignition in fluidized bed fly ash can be as high as 20% or more. The loss on ignition in fly ash is one of the important indicators for identifying its quality. GB / T1596-2005 "Fly ash used in cement and concrete" clearly stipulates the range of the loss on ignition of fly ash. It is generally believed that the unburned carbon content can be estimated based on the loss on ignition in fly ash.

[0005] After searching for relevant information in the CNKI database, several papers have specifically mentioned the hazards or impacts of unburned carbon or loss on ignition in fly ash.

[0006] Li Xiaojuan et al. (Li Xiaojuan, Zhou Meiru, Zhu Hongbo. Effect mechanism of high carbon fly ash on the fluidity of cement paste and its early activity [J]. Concrete, 2022, (1): 153-155, 166.) believe that high carbon fly ash can significantly reduce the fluidity of cement paste. The reason may be that the unburned carbon adsorbs free water in the paste and the content of non-spherical particles is relatively high.

[0007] Zhang Xue et al. (Zhang Xue, Chen Shiguo, Wang Qunying, Jia Lutao, Li Yonghui. Factors affecting the water demand ratio of fly ash and measures to reduce it [J]. Huadian Technology, 2016, 38(8): 3-7, 77.) believed that fly ash with a large loss on ignition has a lot of residual carbon, and the carbon particles themselves are coarse and porous and have no gelling properties, which makes them easy to absorb water, thus increasing the water demand ratio of fly ash.

[0008] Wu Bin et al. (Wu Bin, Luo Xin, Zhao Jinsong. Effect of fly ash quality on its water demand and activity [J]. Sichuan Building Materials, 2015, 41(4): 23-24.) found that the water demand of fly ash increases linearly with the increase of loss on ignition, and the linear correlation coefficient R 2 As high as 0.90, the loss on ignition has a significant negative effect on the water demand of fly ash.

[0009] Zhang Junping et al. (Zhang Junping, He Hongjun. On the influence of fly ash ignition loss on concrete workability [J]. Sichuan Cement, 2015, (4): 136.) found that as the ignition loss of fly ash increases, the workability and fluidity of concrete become worse, and the loss of expansion over time also increases.

[0010] Tan Yanbin et al. (Tan Yanbin, Li Huajian, Xie Yongjiang, Yi Zhonglai. Effects of ignition loss and fineness on rheological properties of fly ash slurry [J]. Railway Construction, 2010, (2): 127-129.) found that the effect of ignition loss on rheological properties of fly ash is much greater than that of fly ash fineness; and the smaller the ignition loss of fly ash, the greater the fluidity value of the slurry and the shorter the Marshall flow time.

[0011] Xue Yongjie et al. (Xue Yongjie, Hou Haobo, Cha Jin. Research on the influence of high ignition loss fly ash on the mechanical and durability properties of cement paste [J]. Fly Ash, 2007, (4): 24-26.) found that with the increase of ignition loss of fly ash, the water demand of the paste increased, the compressive strength decreased, and the shrinkage performance and sulfate corrosion resistance decreased to varying degrees.

[0012] Therefore, the loss on ignition (unburned carbon) is considered to be a substance harmful to concrete. It will increase the water demand of concrete, thereby increasing the water-cement ratio and seriously affecting the strength of concrete. It will also absorb a large amount of water-reducing agent, causing the water-reducing agent to partially fail and seriously affecting the fluidity of concrete.

[0013] As for how to eliminate the harm of unburned carbon, after consulting relevant academic papers and patents, the main measures are as follows:

[0014] (1) Decarbonization of fly ash

[0015] Shao Jingbang et al. (Shao Jingbang, Wang Zune. Ways to reduce the carbon content of fly ash [J]. China Coal, 1998, (10): 17-19.) believe that different ways can be used to reduce the carbon level in fly ash. During the combustion process, the fuel conditions in the boiler can be adjusted through boiler modification to enable the coal to burn fully, thereby reducing the carbon content. When the carbon content of the discharged fly ash is high, some unburned carbon in the fly ash can be removed by methods such as electrostatic separation, flotation, and combustion.

[0016] Zhang Quanguo et al. (Zhang Quanguo, Li Gang, Xu Bo, Jiao Youzhou, Wang Xuetao, Li Zhenghua, Zhang Xiangfeng. Research on electrostatic decarbonization technology of fly ash [J]. Journal of Safety and Environment, 2002, (1): 47-50.) introduced the electrostatic decarbonization resource utilization technology and conducted an optimization test using a vertical electric field fly ash decarbonization device. The test results showed that when the vertical electric field decarbonization device was operated under the optimal process parameter conditions, the carbon content of the fine ash after fly ash decarbonization could be reduced to 1.20%, and the decarbonization rate was as high as 86.74%.

[0017] Ji Jun et al. (Ji Jun, He Mingli, Zhou Nianxin. Research on decarbonization technology of fly ash from power plants [J]. Jiangxi Coal Science and Technology, 2014, (4): 160-161.) introduced the properties of fly ash from the ash field of the first phase of Laibin Power Plant in Guangxi. After roughing, fine selection and dehydration, fine carbon powder and Class I fly ash with a loss on ignition of no more than 4% can be obtained.

[0018] Zhu Guangli et al. (Zhu Guangli, Wang Haoyu, Li Hailong, Yao Yuan, Teng Rui. Research progress and prospects of fly ash decarbonization [J]. Clean Coal Technology, 2017, 23(1): 110-114.) introduced three methods for fly ash decarbonization, namely flotation, gravity separation and electrostatic separation. Among them, flotation mainly decarbonizes fly ash based on the surface properties of minerals; gravity separation decarbonizes and separates fly ash based on the differences in mineral density properties; and electrostatic separation separates minerals based on the differences in frictional charging properties.

[0019] This treatment method is a one-time solution, directly removing most of the unburned carbon from the fly ash, and there is no need to consider its hazards when using it. It seems to be a good treatment measure. However, this method requires investment in expensive production equipment, is technically difficult, and has high treatment costs. Moreover, in developed provinces with many infrastructure projects, fly ash is in short supply, so fly ash suppliers are not very willing to improve quality.

[0020] (2) Adjustment of concrete admixtures

[0021] One of the main uses of fly ash is to produce concrete. Since unburned carbon adsorbs a large amount of water reducer, a large amount of water reducer does not play its due role, resulting in a low apparent water reduction rate and poor slump retention. Therefore, one of the common and simple methods in actual use is to increase the amount of water reducer. However, this method not only increases production costs, but also makes it difficult to accurately control the amount: if the amount is slightly less, the water reducer is insufficient and the effect is limited, but if the amount is slightly larger, the concrete will have quality defects such as bleeding, slurry bleeding, bottom grabbing or segregation.

[0022] Secondly, add a certain amount of air entraining agent. The addition of air entraining agent will increase the fluidity of concrete, thus compensating for the side effects of unburned carbon to a certain extent. However, this method increases production costs on the one hand, and has little effect on the slump retention ability, so it is not a fundamental solution.

[0023] Finally, carbon shielding agents or inhibitors are added to reduce the adsorption of unburned carbon to admixtures, including water reducers and air entraining agents.

[0024] Some methods mainly shield the adsorption of unburned carbon on air-entraining agents. For example, Wang Xia et al. (Wang Xia, Chen Qin. Research on improving the performance stability of fly ash concrete by ethylene glycol phenyl ether [J]. Commercial Concrete, 2021, (6): 53-56.) used the preferential adsorption of ethylene glycol phenyl ether on carbon particles to shield the adsorption of carbon particles on air-entraining agents, stabilize the air content in concrete, and improve the stability of concrete working performance and mechanical properties. However, this inhibitor only targets air-entraining agents and has limited effect on water reducers.

[0025] There are also methods that mainly inhibit or shield the adsorption of unburned carbon on water reducers. Generally, a carbon inhibitor or shielding agent is developed and compounded with water reducers. For example, Lu Xin et al. (Lu Xin, Zang Jun, Xu Zhan. Preparation and application of fly ash concrete carbon adsorption inhibitor [J]. Commercial Concrete, 2014, (2): 39-40, 52.) used the preferential adsorption of unburned carbon particles in fly ash to aromatic compounds, supplemented with acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, sodium ethylenediaminetetramethylenephosphonate, etc. to prepare a fly ash concrete carbon adsorption inhibitor. The experiment confirmed that it has good inhibition on the carbon adsorption of fly ash, thereby reducing the amount of admixtures and ensuring the working performance of concrete. The patent "A carbon adsorption inhibitor for fly ash concrete and its application" (application number 201210184309.1, authorized) discloses a carbon adsorption inhibitor for fly ash concrete, which mainly includes aromatic amino small molecules, aromatic sodium sulfonate, alcohol derivatives, o-hydroxybenzoate, acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, ethylenediaminetetramethylenephosphonate and organosilane, etc. The invented carbon adsorption inhibitor can inhibit the adsorption of carbon particles in fly ash to admixtures. The patent "Polycarboxylic acid composite water reducer for high carbon content concrete, preparation method and use method" (application number 201410724480.6, authorized) relates to a polycarboxylic acid composite water reducer for high carbon content concrete, preparation method and use method, which is compounded with air entraining agent, defoamer, carbon shielding agent, triethanolamine and inorganic early strength agent with polycarboxylic acid water reducer mother liquor, and has a good effect in high carbon content concrete.

[0026] Such carbon inhibitors or shielding agents have certain effects and need to be compounded with polycarboxylate superplasticizer mother liquor to work. However, expensive chemical reagents are required in production; secondly, due to the unique molecular structure of polycarboxylate superplasticizer, it is a water reducer with poor compatibility with other substances. Therefore, these inhibitors or shielding agents are very easy to delaminate after compounding with polycarboxylate superplasticizer, which affects its effect.

[0027] In summary, after searching relevant information in the CNKI database and the China Patent website, there are papers and patents involving methods for eliminating or inhibiting the hazards of unburned carbon in fly ash, but the number is not large. After reading and sorting out these materials, it is found that there are currently two main methods to solve this problem: one is to decarbonize fly ash; the other is to adjust concrete admixtures. However, the above methods generally have shortcomings such as high production cost, unstable effect, and narrow application range. At the same time, compared with the loss on ignition index, fly ash suppliers pay more attention to the fineness index; at present, the discharge of fluidized bed fly ash is getting higher and higher, resulting in a generally high loss on ignition in the fly ash used in the current concrete mixing station, with few less than 5%, and some even exceeding 20%. According to statistics, about 30% of my country's fly ash has a loss on ignition of more than 20%. This shows that high carbon content in fly ash should be a normal state for a long time in the future. Then, the adsorption of fly ash on water reducer is bound to be a common phenomenon. Summary of the invention

[0028] In view of the disadvantage that polycarboxylate water-reducing agents are generally sensitive to unburned carbon in fly ash, this patent provides a polycarboxylate water-reducing agent mother liquor with low sensitivity to unburned carbon in fly ash, which can significantly improve the workability of concrete containing high-carbon fly ash.

[0029] In order to achieve the above technical solution and the invention objective, a method for producing a polycarboxylic acid water-reducing agent mother liquor with low sensitivity to unburned carbon in fly ash is described as follows.

[0030] The polycarboxylate water-reducing agent mother solution with low sensitivity to unburned carbon in fly ash is prepared according to the following preparation method, and the steps are as follows:

[0031] 1) Mix allyl polyoxyethylene ether with a number average molecular weight of 2400, dicarboxylic acid, inhibitor and catalyst, stir and heat in an oil bath to reflux;

[0032] 2) After heating to 120-160°C and keeping warm for 1-6 hours, a modified macromonomer 1 is obtained;

[0033] 3) At the same time, allyl polyoxyethylene ether with a number average molecular weight of 2400, cyclohexanecarboxylic acid, inhibitor and catalyst are stirred and heated in an oil bath to reflux;

[0034] 4) After heating to 110-140°C and keeping warm for 2-7 hours, the modified macromonomer 2 is obtained;

[0035] 5) Synthesis of polycarboxylate water-reducing agent mother liquor:

[0036] According to the synthetic mass of 1000g polycarboxylate water-reducing agent mother liquor,

[0037] 5.1) Mix 100-250 g of modified macromonomer 1, 100-250 g of modified macromonomer 2 and 340 g of deionized water, and stir at room temperature for 10-20 minutes;

[0038] 5.2) Add 2-6 g hydrogen peroxide and stir for 5 minutes;

[0039] 5.3) Prepare liquid A and liquid B,

[0040] Liquid A: 1.0~1.8g mercaptopropionic acid, 0.5~1.2g vitamin C, 85g deionized water,

[0041] Liquid B: 30-45 g acrylic acid, 2-15 g polyethylene glycol diacrylate, 40 g deionized water;

[0042] Then, liquid A and liquid B were added simultaneously by dropwise addition, wherein liquid A was added dropwise for 2.5 hours and liquid B was added dropwise for 2 hours;

[0043] 5.4) After standing for 1 hour, add water to 1000 grams to obtain the polycarboxylate water-reducing agent mother solution;

[0044] 6) Synthesize other polycarboxylate water-reducing agent mother liquors in equal proportions according to step 5);

[0045] 7) Then, neutralize with sodium hydroxide to a pH of 6-7 to obtain a polycarboxylic acid water-reducing agent mother solution with low sensitivity to unburned carbon in fly ash;

[0046] Wherein, in step 1), the dicarboxylic acid is one of oxalic acid and malonic acid or a mixture thereof; the inhibitor is one of 2-tert-butylhydroquinone and hydroquinone or a mixture thereof; the catalyst is one of concentrated sulfuric acid and p-toluenesulfonic acid or a mixture thereof;

[0047] In step 3), the cyclohexylcarboxylic acid is one or a mixture of cyclohexylcarboxylic acid and cyclohexylacetic acid; the polymerization inhibitor is one or a mixture of 2-tert-butylhydroquinone and hydroquinone; the catalyst is one or a mixture of concentrated sulfuric acid and p-toluenesulfonic acid;

[0048] In step 5.3), the polyethylene glycol diacrylate is one or a mixture of PEG200DA, PEG400DA, and PEG600DA;

[0049] In addition, in step 1), according to the mass ratio, allyl polyoxyethylene ether: dicarboxylic acid: inhibitor: catalyst = 1000: (10-50): (1-5): (5-20);

[0050] In step 3), according to the mass ratio, allyl polyoxyethylene ether: cyclohexanecarboxylic acid: inhibitor: catalyst = 1000: (20-60): (1-5): (5-20);

[0051] Preferably, in step 1), the mass ratio of allyl polyoxyethylene ether: dicarboxylic acid: inhibitor: catalyst = 1000: (20-40): (2-3): (10-15).

[0052] Preferably, in step 3), the mass ratio of allyl polyoxyethylene ether: cyclohexanecarboxylic acid: inhibitor: catalyst = 1000: (30-50): (2-4): (10-20);

[0053] Preferably, in step 5), based on the synthesis mass of 1000 g of polycarboxylate water-reducing agent mother liquor, modified macromonomer 1: modified macromonomer 2: acrylic acid: polyethylene glycol diacrylate: mercaptopropionic acid: vitamin C: hydrogen peroxide = (150-200) g: (150-200) g: (35-45) g: (5-10) g: (1.2-1.6) g: (0.6-1.0) g: (3-5) g, and the remainder is deionized water.

[0054] The polycarboxylate water-reducing agent mother liquor with low sensitivity to unburned carbon in fly ash of the present invention comprises the following steps: firstly, a macromonomer allyl polyoxyethylene ether (HPEG) and a dicarboxylic acid are subjected to an esterification reaction (bulk polymerization) to obtain a modified macromonomer 1; then, a macromonomer allyl polyoxyethylene ether (HPEG) and cyclohexyl carboxylic acid are subjected to an esterification reaction (bulk polymerization) to obtain a modified macromonomer 2; finally, the modified macromonomer 1 and the modified macromonomer 2 are mixed according to a proportion, and free radical copolymerization reaction (solution polymerization) is carried out with polyethylene glycol diacrylate and acrylic acid to obtain a polycarboxylate water-reducing agent mother liquor with low sensitivity to unburned carbon in fly ash.

[0055] The polycarboxylate water-reducing agent mother solution prepared by the invention is added during the preparation of concrete, has low sensitivity to unburned carbon in fly ash, significantly alleviates the adsorption of the water-reducing agent, and significantly improves the workability of concrete containing high-carbon fly ash.

[0056] The technical principle of the present invention is:

[0057] The so-called unburned carbon in fly ash is generated by the carbon components in the coal that have not had time to burn out, and the organic matter has overflowed with the combustion, so the remaining carbon particles are gasified and foamed, thus forming interconnected pores. In a certain sense, it is essentially a loose and porous "activated carbon", and most of the particle sizes are above 45μm, with extremely strong adsorption. The surface of unburned carbon is non-polar, which is due to the presence of oxygen-containing functional groups or inorganic impurities on the surface and has weak polarity. According to the "like dissolves like principle", it has a stronger adsorption effect on non-polar substances, while the adsorption effect on polar molecules is relatively weak. For general polycarboxylate water-reducing agent molecules, it is a typical comb-shaped structure, with a carbon chain as the main chain and a long polyethylene oxide (PEO) chain as the side chain. Therefore, the main chain of the existing polycarboxylate water-reducing agent molecules is very easy to be adsorbed into the particle surface or internal voids of the unburned carbon, and the unburned carbon and cement produce competitive adsorption on the polycarboxylate water-reducing agent molecules, which causes some water-reducing agent molecules to lose their due function.

[0058] The polycarboxylate water-reducing agent mother liquor with low sensitivity to unburned carbon in fly ash of the present invention reduces the adsorption of unburned carbon on the polycarboxylate water-reducing agent from two aspects.

[0059] One is to increase the molecular polarity of polycarboxylate water-reducing agent. When synthesizing polycarboxylate water-reducing agent mother liquor, acrylic acid or methacrylic acid must be used in order to introduce carboxyl groups (-COOH) into the main chain. Carboxyl groups become -COOH in the alkaline environment of cement. - ions, thereby generating electrostatic repulsion. Among organic groups, the carboxyl group is almost the most polar group. The macromonomer allyl polyoxyethylene ether (HPEG) is one of the most important raw materials for synthesizing polycarboxylic acid water reducers. Its molecular formula is CH2=CH(CH3)(OCH2CH2)n OH. It contains active terminal hydroxyl groups that can participate in the reaction and can be used for modification. The present invention uses dicarboxylic acid to esterify HPEG, introduces carboxyl groups on the PEO side chain of HPEG, and further increases the molecular polarity of HPEG. In fact, the terminal ester group formed also has a sustained release function. It will hydrolyze in an alkaline environment to continuously release carboxyl groups to compensate for the loss of water-reducing ability caused by the adsorption of the water reducer.

[0060] The second is to improve the steric hindrance effect. By forming an appropriate cross-linking structure and introducing bulky groups, the steric hindrance effect of the polycarboxylate water-reducing agent molecules is increased, and the polycarboxylate water-reducing agent molecules are adsorbed on the surface of the unburned carbon particles, and some of them can also enter the internal pores of the unburned carbon, and then the unburned carbon particles are prevented from continuing to adsorb other water-reducing agent molecules through the steric hindrance effect, thereby reducing the adsorption of the unburned carbon on the water-reducing agent and effectively reducing the sensitivity to the unburned carbon.

[0061] After reviewing relevant literature and patents, no information was found proposing this method, so this patent application has obvious innovation.

[0062] Beneficial effects of the present invention:

[0063] 1. Compared with the existing anti-carbon technology, the present invention has significant innovations: (1) Different raw materials are used. Cyclohexanecarboxylic acid, adipic acid and polyethylene glycol diacrylate are used. (2) Different processes. A synthesis process combining bulk polymerization and solution polymerization is used.

[0064] 2. The present invention starts from the production process of polycarboxylate water-reducing agent mother liquor, introduces functional groups into polycarboxylate water-reducing agent molecules, or appropriately changes the molecular configuration of polycarboxylate water-reducing agent, so that the polycarboxylate water-reducing agent mother liquor directly obtains the ability to inhibit unburned carbon in fly ash. The polycarboxylate water-reducing agent mother liquor prepared by the present invention is added during the preparation of concrete, has a low sensitivity to unburned carbon in fly ash, significantly alleviates the adsorption of water-reducing agent, and significantly improves the workability of concrete containing high-carbon fly ash.

[0065] 3. The polycarboxylate water-reducing agent mother liquor production process with low sensitivity to unburned carbon in fly ash of the present invention is suitable for industrial production. The present invention adopts common chemical raw materials and has relatively low cost. Moreover, it has good anti-carbon effect: it also has good effect on fly ash with a loss on ignition of up to 20%. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 This is the SEM picture of the fly ash used in the experiment.

[0067] Figure 2 This is a kinetic diagram showing the adsorption amount of different water-reducing agent mother solutions in the pure slurry changing with time. DETAILED DESCRIPTION

[0068] In practical application, the polycarboxylate water-reducing agent mother liquor with low sensitivity to unburned carbon in fly ash described in this patent includes three steps, namely, the preparation of modified macromonomer 1, the preparation of modified macromonomer 2, and the synthesis of polycarboxylate water-reducing agent mother liquor. The present invention will be described in more detail below with reference to the accompanying drawings, in which preferred embodiments of the present invention are shown. It should be understood that those skilled in the art can modify the present invention described herein and still achieve the beneficial effects of the present invention. Therefore, the following description should be understood as being widely known to those skilled in the art and not as a limitation of the present invention.

[0069] Example 1

[0070] 1. Preparation of modified macromonomer 1:

[0071] 1) Add the above substances into a three-necked flask in a ratio of allyl polyoxyethylene ether: oxalic acid: 2-tert-butylhydroquinone: p-toluenesulfonic acid = 1000:20:2:10, start stirring and oil bath heating, and start reflux;

[0072] 2) Heating to 120°C and keeping the temperature for 3 hours to obtain modified macromonomer 1.

[0073] 2. Preparation of modified macromonomer 2:

[0074] 1) Add the above substances into another three-necked flask in the ratio of allyl polyoxyethylene ether: cyclohexylcarboxylic acid: hydroquinone: p-toluenesulfonic acid = 1000:30:2:10, start stirring and oil bath heating, and start reflux;

[0075] 2) heating to 110°C and keeping the temperature for 3 hours to obtain modified macromonomer 2;

[0076] 3. Synthesis of polycarboxylate water-reducing agent mother solution 1 (based on 1000 g of mother solution):

[0077] 1) Add 100 g of modified macromonomer 1, 250 g of modified macromonomer 2, and 340 g of deionized water into a three-necked flask and stir at room temperature for 10 minutes;

[0078] 2) Add 3 grams of hydrogen peroxide and stir for 5 minutes.

[0079] 3) Prepare liquid A and liquid B. Liquid A: 1.2 g mercaptopropionic acid, 0.8 g vitamin C, 85 g deionized water. Liquid B: 40 g acrylic acid, 5 g PEG200DA, 40 g deionized water. Liquid A and liquid B are added dropwise into the three-necked flask, with liquid A added for 2.5 hours and liquid B added for 2 hours.

[0080] 4) Add water to 1000 grams 1 hour after dripping.

[0081] 5) Neutralize with sodium hydroxide to a pH of 6-7 to obtain polycarboxylic acid water-reducing agent mother liquor 1 (PCE1) with low sensitivity to unburned carbon in fly ash.

[0082] Example 2

[0083] 1. Preparation of modified macromonomer 1:

[0084] 1) Add the above substances into a three-necked flask in the ratio of allyl polyoxyethylene ether: malonic acid: hydroquinone: concentrated sulfuric acid = 1000:30:2.5:12, start stirring and oil bath heating, and start reflux;

[0085] 2) Heating to 150°C and keeping the temperature for 4 hours to obtain modified macromonomer 1.

[0086] 2. Preparation of modified macromonomer 2:

[0087] 1) Add the above substances into another three-necked flask in the ratio of allyl polyoxyethylene ether: cyclohexyl acetic acid: hydroquinone: concentrated sulfuric acid = 1000:40:3:15, start stirring and oil bath heating, and start reflux;

[0088] 2) heating to 130° C. and keeping the temperature for 4 hours to obtain modified macromonomer 2;

[0089] 3. Synthesis of water reducing agent mother solution 2 (based on the synthesis of 1000g mother solution):

[0090] 1) Add 250 g of modified macromonomer 1, 100 g of modified macromonomer 2, and 340 g of deionized water into a three-necked flask and stir at room temperature for 15 minutes;

[0091] 2) Add 4 grams of hydrogen peroxide and stir for 5 minutes.

[0092] 3) Prepare liquid A and liquid B. Liquid A: 1.4 g mercaptopropionic acid, 0.6 g vitamin C, 85 g deionized water. Liquid B: 40 g acrylic acid, 5 g PEG400DA, 40 g deionized water. Liquid A and liquid B are added dropwise into the three-necked flask, with liquid A added for 2.5 hours and liquid B added for 2 hours.

[0093] 4) Add water to 1000 grams 1 hour after dripping.

[0094] 5) Neutralize with sodium hydroxide to a pH of 6-7 to obtain polycarboxylic acid water-reducing agent mother liquor 2 (PCE2) with low sensitivity to unburned carbon in fly ash.

[0095] Example 3

[0096] 1. Preparation of modified macromonomer 1:

[0097] 1) Add allyl polyoxyethylene ether: oxalic acid: malonic acid: 2-tert-butylhydroquinone: concentrated sulfuric acid in a ratio of 1000:15:15:3:15 into a three-necked flask, start stirring, heating in an oil bath, and start refluxing;

[0098] 2) Heating to 150°C and keeping the temperature for 5 hours to obtain modified macromonomer 1.

[0099] 2. Preparation of modified macromonomer 2:

[0100] 1) Add allyl polyoxyethylene ether: cyclohexylcarboxylic acid: cyclohexylacetic acid: 2-tert-butylhydroquinone: concentrated sulfuric acid in a ratio of 1000:20:20:4:20 to another three-necked flask, start stirring, heating in an oil bath, and start refluxing;

[0101] 2) heating to 140° C. and keeping the temperature for 5 hours to obtain modified macromonomer 2;

[0102] 3. Synthesis of water reducing agent mother solution 3 (based on the synthesis of 1000g mother solution):

[0103] 1) Add 175 g of modified macromonomer 1, 175 g of modified macromonomer 2, and 340 g of deionized water into a three-necked flask and stir at room temperature for 15 minutes;

[0104] 2) Add 4 grams of hydrogen peroxide and stir for 5 minutes.

[0105] 3) Prepare liquid A and liquid B. Liquid A: 1.2 g mercaptopropionic acid, 0.8 g vitamin C, 85 g deionized water. Liquid B: 40 g acrylic acid, 5 g PEG600DA, 40 g deionized water. Liquid A and liquid B are added dropwise into the three-necked flask, with liquid A added for 2.5 hours and liquid B added for 2 hours.

[0106] 4) Add water to 1000 grams 1 hour after dripping.

[0107] 5) Neutralize with sodium hydroxide to a pH of 6-7 to obtain polycarboxylic acid water-reducing agent mother liquor 3 (PCE3) with low sensitivity to unburned carbon in fly ash.

[0108] Synthesis of Blank Polycarboxylate Superplasticizer Mother Solution

[0109] In order to verify the performance of the above polycarboxylate water-reducing agent mother liquor, a blank polycarboxylate water-reducing agent mother liquor was synthesized as a comparison. The blank polycarboxylate water-reducing agent mother liquor does not contain macromonomer 1, macromonomer 2 and polyethylene glycol diacrylate, and is denoted as PCE0. For greater comparison, its solid content is set to be consistent with PCE1, PCE2 and PCE3. The synthesis method is as follows:

[0110] 1) Add 355 g of allyl polyoxyethylene ether and 340 g of deionized water into a 1000 mL three-necked flask and stir at room temperature for 15 minutes.

[0111] 2) Add 4 grams of hydrogen peroxide and stir for 5 minutes.

[0112] 3) Prepare liquid A and liquid B. Liquid A: 1.4 g mercaptopropionic acid, 0.6 g vitamin C, 85 g deionized water. Liquid B: 40 g acrylic acid, 40 g deionized water. Liquid A and liquid B are added dropwise into the three-necked flask, with liquid A added for 2.5 hours and liquid B added for 2 hours.

[0113] 4) After all the drops are added, add water to 1000 grams 1 hour later.

[0114] 5) Neutralize with sodium hydroxide to a pH of 6-7 to obtain blank water reducer mother liquor (PCE0).

[0115] Effect verification

[0116] The verification test uses circulating fluidized bed desulfurized fly ash, the chemical composition of which is shown in Table 1:

[0117] Table 1 Chemical composition of fly ash used in the experiment / %

[0118] <![CDATA[SiO2]]> <![CDATA[Fe2O3]]> <![CDATA[Al2O3]]> <![CDATA[TiO2]]> CaO MgO <![CDATA[Na2O]]> <![CDATA[K2O]]> <![CDATA[SO3]]> Loss on ignition Total 25.82 3.23 20.31 0.38 21.35 0.52 0.22 0.54 7.60 19.72 99.69

[0119] The data in Table 1 show that the CaO and SO3 mass contents of the fly ash are 21.35% and 7.60%, respectively, which is a typical circulating fluidized bed desulfurized fly ash. In addition, the ignition loss of the fly ash is as high as 19.72%, which is also very high among the fly ashes used in concrete production.

[0120] Figure 1 This is the SEM picture of the fly ash, which shows that most of its particles are irregular in shape, the surface structure of the particles is relatively loose, and there are a large number of pores that are interconnected with the outside world.

[0121] (1) Adsorption test

[0122] The sensitivity of different mother liquors to unburned carbon was compared by studying the adsorption amount of polycarboxylic acid water-reducing agent mother liquor in neat slurry.

[0123] The test used the UV-visible spectrophotometer method to determine the adsorption amount of the water-reducing agent mother liquor. First, a series of polycarboxylic acid water-reducing agent solutions were prepared, the characteristic absorption wavelength was determined, and a standard adsorption curve was established. About 1 gram of cement fly ash mixture (cement: fly ash = 70:30) was added to 100 ml of 5 g / L water-reducing agent solution, stirred at a constant temperature at 25 °C, and the suspension was extracted every 15 minutes. Centrifuged for 15 minutes using a desktop centrifuge, the supernatant was extracted and the absorbance value was measured. The concentration of the water-reducing agent solution after adsorption was calculated according to the standard adsorption curve, and the adsorption amount was calculated according to the following formula

[0124] Q ad = ( C 0 - C ) · ν / W

[0125] Where: Q ad is the adsorption amount, unit is mg / g; C 0 is the initial concentration of the solution, in mg / L; C is the concentration of the solution after adsorption, in mg / L; v is the volume of the solution, in L; W is the mass of montmorillonite, in g.

[0126] Figure 2The kinetic diagram of the adsorption amount of different water-reducing agent mother liquors in the pure slurry changing with time. The polycarboxylic acid water-reducing agent mother liquor PCE1, mother liquor PCE2, mother liquor PCE3 and blank mother liquor PCE0 are the polycarboxylic acid water-reducing agent mother liquors synthesized in the above examples.

[0127] Figure 2 The results show that the adsorption amount of the four water-reducing agent mother liquors tends to be flat around 60 minutes. In addition, at any preset time point, the adsorption amount of the four water-reducing agent mother liquors is in the following order: PCE0 > PCE1 > PCE2 > PCE3, indicating that the water-reducing agent mother liquor synthesized in this patent can effectively reduce the sensitivity to unburned carbon, among which PCE3 is the most significant.

[0128] (2) Fluidity of pure slurry

[0129] The net paste test was carried out in accordance with GB / T8077-2012 "Test method for homogeneity of concrete admixtures", and the net paste ratio was: 210g 42.5R ordinary Portland cement, 90g fly ash, 87g water, and 0.6g water reducer mother liquor. The fluidity of the net paste was measured at the initial stage, 30 minutes and 60 minutes, and the test results are shown in Table 2. The results show that the net paste fluidity of each water reducer mother liquor shows a certain difference at the beginning. This is because the unburned carbon in fly ash has a strong adsorption capacity. Once it comes into contact with the water reducer, it begins to adsorb, but the initial fluidity is not much different. However, at 30 minutes and 60 minutes, the net paste fluidity of PCE1, PCE2 and PCE3 is significantly greater than that of blank PCE0. It also shows that the sensitivity of these three water reducer mother liquors to unburned carbon in fly ash is significantly lower than that of the blank water reducer mother liquor. Among them, water reducer mother liquor 3 has the best effect, which is comparable to the blank water reducer mother liquor. Figure 2 The results are relatively consistent.

[0130] Table 2 Effect of different polycarboxylate water-reducing agent mother solutions on the fluidity of high carbon cement paste

[0131] Water reducing agent sample Initial (mm) 30 minutes (mm) 60 minutes (mm) PCE0 290 262 212 PCE2 297 279 263 PCE3 302 288 272 PCE4 308 300 290

[0132] (3) Compressive strength

[0133] Natural river sand with a mud content of about 1.6% was used, which came from the Yuniao River in Yantai. The test was carried out in accordance with GB / T8077-2012 "Test Method for Symmetry of Concrete Admixtures". The ratio of cementitious materials was cement: fly ash = 70:30. Without the use of a water reducer, the water consumption when the mortar fluidity reached (180±5) mm was 225 mL, and then 0.3% of the cement mass of the water reducer mother liquor was added, and the water consumption was appropriately reduced and the test was carried out again. The water reduction rate of the mortar was obtained by calculation, and the mortar specimens were prepared at this water-cement ratio. The mortar was cured in accordance with GB / T 17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)", and the compressive strength of the test blocks at 3 days and 7 days of age were measured, respectively. The results are shown in Table 3.

[0134] Table 3 Effect of different polycarboxylate superplasticizer mother solutions on mortar strength

[0135]

[0136] The results in Table 3 show that the water reduction rates of PCE1, PCE2 and PCE3 are significantly higher than PCE0, and the mortar strength is also higher, among which PCE3 has the best effect. This shows that the three water-reducing agent mother liquors synthesized in this patent are less sensitive to the unburned carbon in fly ash, which is consistent with the previous results.

[0137] The test indicators of adsorption amount, net slurry fluidity and compressive strength verified above show that the water-reducing agent mother liquor synthesized by the present invention has low sensitivity to unburned carbon, can effectively alleviate the adsorption of unburned carbon on the water-reducing agent, and also has a slow-release function. Therefore, the polycarboxylate water-reducing agent mother liquor prepared by the present invention, when added during the preparation of concrete, has low sensitivity to unburned carbon in fly ash, significantly alleviates the adsorption of water-reducing agent, and significantly improves the workability of concrete containing high-carbon fly ash.

[0138] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A polycarboxylate water-reducing agent mother solution with low sensitivity to unburned carbon in fly ash, characterized in that It was prepared according to the following preparation method, the steps are as follows: 1) Mix allyl polyoxyethylene ether with a number average molecular weight of 2400, dicarboxylic acid, polymerization inhibitor and catalyst, stir and heat in an oil bath to reflux; 2) After heating to 120-160°C and keeping warm for 1-6 hours, a modified macromonomer 1 is obtained; 3) At the same time, allyl polyoxyethylene ether with a number average molecular weight of 2400, cyclohexanecarboxylic acid, inhibitor and catalyst are stirred and heated in an oil bath to reflux; 4) After heating to 110-140°C and keeping warm for 2-7 hours, the modified macromonomer 2 is obtained; 5) Synthesis of polycarboxylate water-reducing agent mother liquor: According to the synthetic mass of 1000g polycarboxylate water-reducing agent mother liquor, 5.1) Mix 100-250 g of modified macromonomer 1, 100-250 g of modified macromonomer 2 and 340 g of deionized water, and stir at room temperature for 10-20 minutes; 5.2) Add 2-6 g hydrogen peroxide and stir for 5 minutes; 5.3) Prepare liquid A and liquid B, Liquid A: 1.0~1.8g mercaptopropionic acid, 0.5~1.2g vitamin C, 85g deionized water, Liquid B: 30-45 g acrylic acid, 2-15 g polyethylene glycol diacrylate, 40 g deionized water; Then, liquid A and liquid B were added simultaneously by dropwise addition, wherein liquid A was added dropwise for 2.5 hours and liquid B was added dropwise for 2 hours; 5.4) After standing for more than 1 hour, add water to 1000 grams to obtain the polycarboxylate water-reducing agent mother solution; 6) Synthesize other polycarboxylate water-reducing agent mother liquors in equal proportions according to step 5); 7) Then, neutralize with sodium hydroxide to a pH of 6-7 to obtain a polycarboxylic acid water-reducing agent mother solution with low sensitivity to unburned carbon in fly ash; Wherein, in step 1), the dicarboxylic acid is one of oxalic acid and malonic acid or a mixture thereof; the inhibitor is one of 2-tert-butylhydroquinone and hydroquinone or a mixture thereof; the catalyst is one of concentrated sulfuric acid and p-toluenesulfonic acid or a mixture thereof, and the mass ratio of allyl polyoxyethylene ether: dicarboxylic acid: inhibitor: catalyst = 1000: (10-50): (1-5): (5-20); In step 3), the cyclohexanecarboxylic acid is one of cyclohexanecarboxylic acid and cyclohexaneacetic acid or a mixture thereof; the inhibitor is one of 2-tert-butylhydroquinone and hydroquinone or a mixture thereof; the catalyst is one of concentrated sulfuric acid and p-toluenesulfonic acid or a mixture thereof, and the mass ratio of allyl polyoxyethylene ether: cyclohexanecarboxylic acid: inhibitor: catalyst = 1000: (20-60): (1-5): (5-20); In step 5.3), the polyethylene glycol diacrylate is one or a mixture of PEG200DA, PEG400DA, and PEG600DA.

2. The polycarboxylate water-reducing agent mother solution with low sensitivity to unburned carbon in fly ash according to claim 1, characterized in that: In step 1), according to the mass ratio, allyl polyoxyethylene ether: dicarboxylic acid: inhibitor: catalyst = 1000: (20-40): (2-3): (10-15).

3. The polycarboxylate water-reducing agent mother solution with low sensitivity to unburned carbon in fly ash according to claim 1, characterized in that: In step 3), according to the mass ratio, allyl polyoxyethylene ether: cyclohexanecarboxylic acid: inhibitor: catalyst = 1000: (30-50): (2-4): (10-20).

4. The polycarboxylate water-reducing agent mother solution with low sensitivity to unburned carbon in fly ash according to claim 1, characterized in that: In step 5), based on the synthesis mass of 1000 g of polycarboxylic acid water-reducing agent mother liquor, modified macromonomer 1: modified macromonomer 2: acrylic acid: polyethylene glycol diacrylate: mercaptopropionic acid: vitamin C: hydrogen peroxide = (150-200) g: (150-200) g: (35-45) g: (5-10) g: (1.2-1.6) g: (0.6-1.0) g: (3-5) g, and the remainder is deionized water.

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