聚羧酸系减水剂的分散作用及其引气性能_英文_

硅酸盐学报· 616 ·2009年聚羧酸系减水剂的分散作用及其引气性能李顺，文梓芸(华南理工大学材料科学与工程学院，特种功能材料教育部重点实验室，广州 510640)摘要：采用自由基聚合法合成了一系列聚羧酸减水剂，通过正交试验研究了减水剂官能团种类及比例，引发剂、链转移剂对其在水泥浆中分散性能的影响。

在此基础上，通过优化官能团比例及调整分子量合成了一种引气性低且分散性高的聚羧酸系减水剂。

分析了官能团比例和分子量对聚羧酸系减水剂引气性能的影响，探讨了分子量及其分布与聚羧酸系减水剂的分散性能及其饱和掺量的关系。

结果表明：合适的官能团比例是降低聚羧酸系减水剂引气性的前提。

官能团比例合适时，分子量过高将导致其引气性增强，聚羧酸系减水剂在水泥净浆中的分散性低，且在水泥砂浆中的饱和掺量高。

关键词：聚羧酸系减水剂；分子量；分布；分散性能；引气性能中图分类号：TQ172 文献标志码：A 文章编号：0454–5648(2009)04–0616–06DISPERSIBILITY AND AIR ENTRAINING PERFORMANCE OF POLYCARBOXYLATE-TYPEWATER REDUCERSLI Shun，WEN Ziyun(Key Laboratory of Specially Functional Materials of Ministry of Education, College of Materials Science and Engineering,South China University of Technology, Guangzhou 510640, China)Abstract: A series of polycarboxylate-type water reducers (PCWRs) were synthesized by free radical copolymerization. Effects of type and ratio of the functional group, initiator and chain transfer on the dispersibility of the PCWRs in cement grout were investi-gated by using an orthogonal test. The PCWR with a low air entraining capability and a high dispersibility was synthesized by opti-mizing the functional group ratio and adjusting the molecular mass. The effects of the functional group ratio and the molecular mass on the air entraining performance of the PCWR were analyzed. The relationships among the molecular mass and its distribution and the dispersibility, as well as the saturation dosage of the PCWRs were discussed. The results show that. The strengthened air entrain-ing capability of the PCWR with the appropriate functional group ratio results from the excessively high molecular mass. When the molecular mass is excessively high, the dispersibility of the PCWR in the cement paste is low, but its saturation dosage in cement mortar is high.Key words: polycarboxylate-type water reducers; molecular mass; distribution; dispersibility; air entraining performancePolycarboxylate-type water reducers (PCWRs) were first developed in the 1990s. [1] The PCWRs had been developed during the past decade, attributed to its poten-tially changeable molecular structure. This chemical possesses an excellent water reducing capability and a dispersion retention stability at a low content.[2–7] Cement particles can be efficiently dispersed using this chemical due to the electrostatic repulsions and the steric hindrance effects.[8–10] Yamada et al.[11] investigated the effect of chemical structure on the properties of polycarboxy-late-type superplatisizer. Li et al.[12] discussed the influ-ence of polyethylene oxide chains on the performance of the PCWRs. Cho et al.[13] investigated the effect of syn-thetic conditions on the dispersibility of poly{carboxylate- g-(ethylene glycol) methyl ether} in cement paste. Plank et al.[14–15] analyzed the dispersibility and adsorption be-havior of the PCWRs with respect to the molecular structure. As known, the use of the PCWRs can increase the air content of concrete, which is beneficial to the workability and durability of concrete. The objective of this paper was to investigate the dispersibility, dispersion retention capability and air entraining performance of the收稿日期：2008–11–06。

修改稿收到日期：2009–01–08。

第一作者：李顺(1977—)，男，博士研究生。

通讯作者：文梓芸(1943—)，男，博士，教授，博士研究生导师。

Received date:2008–11–06. Approved date: 2009–01–08.First author: LI Shun (1977–), male, postgraduate student for doctor degree. Correspondent author: WEN Ziyun (1943–), male, Ph.D., professor.E-mail: lis1116@第37卷第4期2009年4月硅酸盐学报JOURNAL OF THE CHINESE CERAMIC SOCIETYVol. 37，No. 4April，2009硅酸盐学报JOURNAL OF THE CHINESE CERAMIC SOCIETY第37卷第4期2009年4月Vol. 37，No. 4 April，2009李顺等：聚羧酸系减水剂的分散作用及其引气性能· 617 ·第37卷第4期PCWRs in cement grout from the functional group ratio and the molecular mass, and its distribution.1 Experimental1.1 Synthesis of PCWRsGrade 52.5 Portland cement (type II) was supplied by Yuexiu Cement Plant in Guangzhou. Fine aggregate was ISO standard sand from Xiamen. Polyalkylene glycol monomethacrylate (PGMA) was from Clariant Chemical.Methyl acrylic acid (MAA) and sodium hydroxide were from Kermel Chemical Co. in Tianjin. Methyl methacrylate (MMA) and ethyl acrylate (EA) were from Chinese Medical Group Chemical Co.. Initiator and chain transfer were from Guanghua Chemical in Guangzhou.The PCWRs were synthesized by a free radical co-polymerization with the PGMA, MAA, MMA and EA in water solution. In this step, the mixed monomer solution and initiator solution were dropwise charged into the vessel, equipped with a stirrer, a thermometer and a re-flux condenser, within 4 and 5h, respectively. The tem-perature was kept in the range of 75 to 85℃. After the completion of copolymerization, the polymer solution was neutralized by 30% (in mass) sodium hydroxide so-lution to pH value 6.5–7.0. Then, a certain amount of water was added to obtain a solution with a solid content of 20% by mass.1.2 Measurement1.2.1 Gel permeation chromatography The average molecular mass and distribution of the PCWRs were de-termined from gel permeation chromatography (GPC) measurements using a Waters 515 chromatographic ap-paratus equipped with four columns ultrahydrogel 120, 250, 500 and 1000, as well as a detector (Waters 2410). The temperature of column was kept at 40℃. The sam-ples were analyzed using a 0.1mol/L Na2SO4 aqueous solution as an eluant, at a flow rate of 0.6mL/min. The monodisperse polyethylene glycols with various molecu-lar mass were used as calibration standards.1.2.2 Fluidity of cement paste The cement paste was prepared with a water-cement ratio of 0.29 or 0.35 at 20℃. The PCWRs were added into water at a solid con-tent ranging from 0.15% to 0.4% by mass. The specimen of cement paste was sealed in a container for 5, 30, 60 and 90min, respectively. The fluidity of cement paste was measured using a minislump cone (a height of 60 mm, upper diameter of 36mm and a bottom diameter of 60mm). The processes were performed according to the Chinese standard GB/T 8077—2000.1.2.3 Water reducing ratio of the PCWRs in cement mortar The testing and reference mortar with the same fluidity (180±5)mm was each made by adjusting the amount of water used. Thus, the water reducing ratio (WRR) of the PCWRs at different contents in cement mortar can be calculated. The mixing and testing proce-dures were carried out according to the Chinese standardGB/T 17671—1999 and GB/T 8077—2000.1.2.4 Air content of cement mortar Air content of cement mortar was examined using an air meter ModelLC–546(Sanyo, Japan).2 Results and discussion2.1 Selection of monomer ratioThe results of the preliminary tests[10]show that the monomers such as PGMA (factor A), MAA (factor B), MMA and EA can be used to synthesize the PCWRs. However, their proper combination may have an effect onthe performance of the PCWRs. The molecular mass and distribution of the PCWRs are closely related to the amount of initiator (factor C) and chain transfer (factor D), which have significant influences on the dispersibility, dispersion retention capability and air entraining capabil-ity of the PCWRs. To optimize the combination formula,an orthogonal test program was designed. Monomers used for the synthesis are PGMA, MAA and MMA as well. Table 1 gives the factors and levels of the experi-ments designed by a statistic approach L9(34). Tables 2 and 3 show the experimental results. It is seen from Table4 that for the WRR of cement mortar with the PCWRs, factors A and D are the primary important parameters among the variables studied. The secondary important parameter is factor B. The amount of initiator (factor C)has a less effect on the WRR of cement mortar.Table 1 Factors and levels of the orthogonal test for pre-paring PCWRsFactor (in mole)/% Factor (in mass)/% LevelA B C D1 20 40 1 0.52 25 503 1.03 30 60 5 2.0 Factors A, B, C, D are represented for PGMA, MAA, initiator, chain transfer.Table 2 Scheme and results of the orthogonal test inmortarFactor/% Water reducing ratio/%Serial numberA B C D 0.2 0.3 0.41 204010.520.827.127.12 205031.022.925.027.13 206052.018.820.820.84 254032.014.616.718.85 255050.520.827.127.16 256011.018.820.820.87 304051.013.516.720.88 305012.015.616.720.89 306030.520.822.925.0硅 酸 盐 学 报· 618 ·2009年Table 3 Scheme and results of the orthogonal test in pasteFactor/% Fluidity/mmSerial numberA B C D 0.2% 0.3%0.4%1 20 40 1 0.5 60 101 1392 20 503 1.0 166 211 200 3 20 60 5 2.0 196 262 2494 25 40 3 2.0 60 60 60 5 25 50 5 0.5 132 163 2006 25 60 1 1.0 179 232 2607 30 40 5 1.0 60 60 608 30 50 1 2.0 60 96 1229 30 60 3 0.5 203 256 280 0.2%, 0.3% and 0.4% all denote the dosage of PCWRs in mortar, the same below.Table 4 Range analysis of the orthogonal test in mortarFactor (0.2%)Factor (0.3%)Factor (0.4%)IndexA B C D A B C D A B CDK 1 20.8 16.3 18.4 20.8 24.3 20.221.5 25.7 25.0 22.222.926.4K 2 18.1 19.8 19.4 18.4 21.5 22.921.5 20.8 22.2 25.023.622.9K 316.6 19.5 17.7 16.3 18.8 21.521.5 18.1 22.2 22.222.920.1Range 4.2 3.5 1.7 4.5 5.5 2.70 7.6 2.8 2.80.76.3K i (i =1, 2, 3) is average of index for level i .And the better formula is the combination of A 1, B 2, C 2 and D 1. As shown in Table 5, for the fluidity of cement paste with PCWRs, factor B is the most significant pa-rameter, while other three factors have a less effect on the fluidity of cement paste. And the better formula is the combination of A 1, B 3, C 2 and D 1. In the two different systems, the almost same formula was obtained, and the difference was the amount of B (correspondingly, the different amount of MMA).Table 5 Range analysis of the orthogonal test in pasteFactor (0.2%)Factor (0.3%)Factor (0.4%)IndexA B C D A B C D A B CDK 1 141 60 100 132 191 74143 173 196 86174206K 2 124 119 143 135 152 157176 168 173 174180173K 3108 193 129 105 137 250162 139 154 263170144Range 33 133 43 30 54 17633 34 42 1771062To examine the results of the statistically designed experiment, the PCWR-1 and the PCWR-2 were synthe-sized using the formula of A 1B 3C 2D 1 and A 1B 2C 2D 1, re-spectively (see in Table 6). Figure 1 shows a higher dis-persibility of the PCWR-1 rather than that of the PCWR-2 in cement paste. Figure 3 (a) shows a higher dispersibility of the PCWR-2 compared to that of the PCWR-1 in cement mortar. For the PCWR-1 and the PCWR-2, different dispersibilities in cement paste and mortar were related to their molecular structures. On theTable 6 Monomer mole fraction for PCWRs synthesisx /%SamplePGMA MAA MMA EAPCWR-1 20 60 20 PCWR-2 20 50 30 PCWR-3 15 65 20 PCWR-4 15 55 30 PCWR-5 30 65 5 PCWR-6 30655PCWR-7 30 65 5 x —Mole fraction.Fig.1 Variation of minislump spread of cement paste withcontents of PCWRs李顺等：聚羧酸系减水剂的分散作用及其引气性能· 619 ·第37卷第4期Fig.2 Minislump spread of cement paste with different cotents of PCWR-7Fig.3 Water reducing ratio of PCWRs at different dosages in cement mortarother hand, Table 7 shows that the air content of cement mortar with the PCWR-1 and the PCWR-2 was greater, indicating their high air entraining capability. This is dis-advantageous to the strength development of cement mortar. Therefore, it is necessary to improve the dispersi-bility and reduce the air entraining capability of the PCWRs in order to further optimize the monomer ratio. 2.2 Optimization of monomer ratioTo improve the dispersibility and reduce the air en-training capability, the PCWR-3 and the PCWR-4 (in Table 6), were synthesized by changing the ratio of the PGMA and MAA based on the formula of the PCWR-1 and the PCWR-2, respectively. Figure 1 shows that com-pared to the PCWR-1 and the PCWR-2, the minislump spread of cement paste with either the PCWR-3 or the PCWR-4 increased, respectively. This indicates that the dispersibility of the PCWRs increased with increasing the ratio of the MAA. Also, the air entraining capability of the PCWR-3 and the PCWR-4 was higher (see Table 7). From the analysis above, the PCWR-5 was synthesized by changing the ratio of the PGMA and the MMA based on the PCWR-3 formula (in Table 6). As a result, the dis-persibility of the PCWR-5 in cement paste increased, compared to that of the PCWR-3(see Fig.1(a)). Mean-while, the air content of cement mortar was decreased to 16.5%, indicating that the air entraining capability of the PCWR-5 was obviously reduced (see Table 7). In addi-tion, the air entraining capability of the PCWRs was fur-ther reduced by adjusting the molecular weight when the PCWR-7 contains the same monomer ratio as the PCWR-5. The air content of cement mortar with 0.2% of the PCWR-7 was only 9.0 %. Figure 2 shows that the dispersibility of the PCWR-7 in cement paste was im-proved compared to the PCWR-5. The dispersibility and the air entraining capability of the PCWRs both were improved by adjusting the monomer ratio and the mo-lecular mass.Table 7 Air content of cement mortar with PCWRsSample Dosage,w/% Water-cement ratio Air content/% PCWR-1 0.2 0.37 28.0PCWR-2 0.2 0.36 30.0PCWR-3 0.2 0.38 30.0PCWR-4 0.2 0.38 32.0 PCWR-5 0.2 0.36 16.5 PCWR-6 0.2 0.36 22.0 PCWR-7 0.2 0.40 9.0 2.3 Air entraining performance of PCWRsThe PCWRs are a kind of high molecular surfactant. Its air entraining capability is related to the surface activ-ity. Generally, the higher surface activity of the PCWRs, the higher air entraining capability of the PCWRs has. The air entraining performance of the PCWRs is affected by the ratio of functional group in molecule. In Tables 6 and 7, the air entraining capability of PCWRs was higher when the molar ratio of the MMA (containing ester group) varied from 20% to 30%. This capability was reduced when the molar ratio of the MMA was decreased to 5%. This illustrates that the excessive ester groups in mole-硅酸盐学报· 620 ·2009年cule could strengthen the air entraining capability of the PCWRs. Compared to the PCWR-1 and the PCWR-4, the mass average molecular mass M m of the PCWR-5 in-creased(see Table 8), however, the air entraining capabil-ity reduced due to the decreased amount of ester groupsin molecule. Compared to the PCWR-5, the M m of the PCWR-7 is decreased, and the corresponding air entrain-ing capability is reduced, resulting from the decreased amount of functional groups such as ester groups, car-boxyl of the MAA, and polyethylene oxide (PEO) of the PGMA. For the PCWR-5 and the PCWR-6, the ratio of functional groups and M m is almost similar, but the air entraining capability of the latter is higher than that of the former. This may be due to the different types of ester groups from the MMA and the EA. From the analyses above, it can be concluded that the air entraining capabil-ity of the PCWRs was correlated to both the ratio of functional group and M m. The precondition to reduce the air entraining capability of the PCWRs was the appropri-ate ratio of the functional group.Table 8 Average molecular mass and PDI of PCWRsSample M m×104M n×104 PDI(M m/M n)PCWR-1 6.65 3.04 2.19 PCWR-2 7.37 2.91 2.53 PCWR-3 5.47 2.54 2.15 PCWR-4 5.63 2.47 2.28 PCWR-5 7.58 3.44 2.20 PCWR-6 7.70 3.21 2.40 PCWR-7 3.51 1.31 2.69 M m denotes mass average molecular mass; M n denotes number average molecular mass.2.4 Dispersibility and saturation dosage of PCWRsThe effects of molecular mass, distribution and ratioof functional group on the dispersibility and dispersion retention capability of the PCWRs in cement paste were investigated. For the PCWR-1 to the PCWR-4, it is rea-sonable to analyze their different disperabilities in cement paste due to their approximate air entraining capabilities. From the results in Fig.1 and in Table 6, it can be con-cluded that the dispersion capability of the PCWRs in-creased with increasing the content of carboxyl from 50%to 65%. Among the four PCWRs, the dispersion capabil-ity of the PCWR-3 was the highest but its dispersion re-tention capability in cement paste was lower, especiallyat the dosage of 0.20% and 0.25%. This is attributed to its relative low M m and PDI, (see Table 8). Compared to the PCWR-3, the M m of the PCWR-1 increased and the dis-persibility in cement paste decreased. In contrast with the PCWR-4, the M m of the PCWR-2 increased and the dis-persibility in cement paste decreased. For the PCWR-5 and the PCWR-6, the M m of the latter was higher and the dispersibility of the former was higher in cement paste. Compared to the PCWR-5 and the PCWR-6, the M m of the PCWR-7 was obviously low. The dispersibility of the PCWR-7 was improved in cement paste (see Fig.2). It is indicated that in a certain range, the increased molecular mass would lead to the decreased dispersion capability in cement paste when the ratio of functional group of the PCWRs was similar.For the PCWR-2, the PCWR-5 and the PCWR-6, the WRR in cement mortar can be increased with increasing the content from 0.2% to 0.4%, which indicates that the saturation dosage was at least 0.4%. This was correlated with their higher molecular mass. For the PCWR-3, the WRR in cement mortar was equal at the content of 0.3% and 0.4%, and the WRR of the PCWR-4 in cement mor-tar decreased with increasing the content from 0.3% to 0.4%, indicating that the saturation dosage of them was 0.3% due to their approximate molecular mass and the PDI. When the PCWR-1 and the PCWR-7 are concerned, the WRR was not increased with increasing the dosage from 0.25% to 0.3%, showing that their saturation dosage was 0.25%. These results and the GPC results in Table 8 indicate that the molecular mass and the PDI both have effects on the saturation dosage of the PCWRs. The ex-cessive high molecular mass of the PCWRs would lead to the higher saturation dosage in cement mortar.3 Conclusions(1) A higher mole fraction of the MMA in the PCWRs resulted in a lower dispersibility in cement paste and a higher air entraining capability in cement mortar.(2) The air entraining capability of the PCWRs could be reduced in the appropriate ratio of functional group. A higher molecular mass could give a higher air entraining capability of the PCWRs with the appropriate ratio of functional group.(3) The excessive higher molecular mass of the PCWRs would lead to a lower dispersibility in cement paste and a higher saturation dosage in cement mortar. References:[1] KINOSHITA M, YONEZAWA T, YUKI Y. Chemical structure andperformance of a new type high range water reducing agent for ultra high strength concrete [J]. Semento, Konkurito Ronbunshu, 1993, 47: 196–201.[2] LIM G G, HONG S S, KIM D S, et al. Slump loss control of cementpaste by adding polycarboxylic type slump-releasing dispersant [J].Cem Concr Res, 1999, 29(2): 223–229.[3] LIAO T S, HWANG C L, YE Y S, et al. Effects of a carboxylic acid/sulfonic acid copolymer on the material properties of cementitious materials [J]. Cem Concr Res, 2006, 36(4): 650–655.[4] YAMADA K, TAKAHASHI T, MATSUHISA M. Effect of chemicalstructure and water cement ratio on the fluidity of cement paste added with polycarboxylate type dispersant [J]. Semento, Konkurito Ron-bunshu, 1998, 52: 158–164.李顺等：聚羧酸系减水剂的分散作用及其引气性能· 621 ·第37卷第4期[5] OHTA A, SUGIYAMA T, TAMAKA Y. Fludizing mechanism andapplication of polycarboxylate based superplasticizers [A]//MALHOTRA V M ed. 5th CANMET/ACI International Conference on Superplasti-cizers and Other Chemical Admixtures in Concrete [C], Rome, Italy, 1997: 359–378.[6] YAMADA K, OGAWA S, HANEHARA S. Controlling of the adsorp-tion and dispersing force of polycarboxylate-type superplasticizer by sulfate ion concentration in aqueous phase [J]. Cem Concr Res, 2001, 31(3): 375–383.[7] TSENG Y C, WU W L, HUANG H L, New carboxylic acid-basedsuperplasticizer for high-performance concrete [A]// 6th CANMET/ ACI International Conference on Superplaticizers and Other Chemical Admixtures in Concrete [C]. Nice, France, 2000: 401–413.[8] YOSHIOKA K, SAKAI E, DAIMON M, et al. Role of steric hindrancein the performance of water-reducers for concrete [J]. J Am Ceram Soc, 1997, 80(10): 2667–2672.[9] YOSHIOKA K, TAZAWA E, KAWAI K, et al. Adsorption characteris-tics of water-reducers on cement component minerals [J]. Cem Concr Res, 2002, 32(10): 1507–1513. [10] LI Shun, WEN Ziyun. Synthesis of polycarboxylate-type superplasti-cizer and its effects on the performance of cement-based materials [J].J Chin Ceram Soc (in Chinese), 2008, 36(7): 884–889.[11] YAMADA K, TAKAHASHI T, HANEHARA S, et al. Effects of thechemical structure on the properties of polycarboxylate-type super-plasticizer [J]. Cem Concr Res, 2000, 30(2): 197–207.[12] LI Chongzhi, FENG Naiqian, LI Yongde, et al. Effects of polyethleneoxide chains on the performance of polycarboxylate-type water-re- ducers [J]. Cem Concr Res, 2005, 35(5): 867–873.[13] CHO H Y, SUH J M. Effects of the synthetic conditions of poly {car-boxylate-g-(ethylene glycol) methyl ether} on the dispersibility in ce-ment paste [J]. Cem Concr Res, 2005, 35(5): 891–899.[14] PLANK J, POLLMANN K, ZOUAOUI N, et al. Synthesis and per-formance of methacrylic ester based polycarboxylate superplasticizers possessing hydroxy terminated poly (ethylene glycol) side chains [J].Cem Concr Res, 2008, 38(10): 1210–1216.[15] PLANK J, WINTER CH. Competitive adsorption between superplas-tic-izer and retarder molecules on mineral binder surface [J]. Cem Concr Res, 2008, 38(5): 599–605.※※※※※※※※※更正《硅酸盐学报》(2009年，37卷第1期，第16页)，图6更正如下：图6 不同温度下涂层的单位面积覆冰量Fig.6 Mass of ice in unit area at different temperatures1—Superhydrophobic coating prepared in our experiment; 2—High temperature vulcanized silicone rubber (HTV); 3—Glass。