Article pubs.acs.org/IECR
Synthesis of Modified Chitosan Superplasticizer by Amidation and Sulfonation and Its Application Performance and Working Mechanism Shenghua Lv,* Jingjing Liu, Qingfang Zhou, Ling Huang, and Ting Sun College of Resource and Environment, Shaanxi University of Science & Technology, Xi’an 710021, China ABSTRACT: A sulfonated chitosan superplasticizer (SCS) was synthesized from chitosan, maleic anhydride, and sodium metabisulfite via amidation and sulfonation. The structure and molar masses were confirmed by FTIR, 1H NMR, and GPC. The application performance was determined by water-reducing ratio, paste fluidity, setting time, hydration heat−time curve, compressive strength, pore structure, and SEM images. The results indicated that SCS has high water-reducing ratio, better paste fluidity, and suitable setting time at low water-to-cement ratio (0.29). The working mechanism of SCS was revealed by the adsorption behavior of SCS and the zeta-potential of cement. The results demonstrated that SCS and polycarboxylate superplasticizers (PCs) have great similarity in molecular structure and performance, and SCS exceeds PCs with regard to retarding effect and improving compressive strength. This study, especially, demonstrates that a high-performance superplasticizer may be synthesized using a renewable natural polymer and simple synthesis methods, which will be a trend for the future.
1. INTRODUCTION Water reducers have become an indispensable ingredient of various types of concrete because they can reduce the water-tocement (w/c) ratio, maintain high slump of fresh concrete, and improve the compressive strength of concrete.1,2 Therefore, the development of novel water reducers and improving existing water reducers are always research hotspots. According to whether the water-reducing ratio is over 12%, water reducers are divided into common water reducers and high-range or high-performance water reducers, which are usually called superplasticizers (SPs). 1 A common water reducer is lignosulfonate (LS), which includes sodium lignosulfonate and calcium lignosulfonate.3,4 In contrast, SPs have a richer diversity, which include sulfonated melamine−formaldehyde condensates (SMF),5 sulfonated naphthalene−formaldehyde condensates (SNF),6 acetone formaldehyde sulfite (AFS), sulfanilic acid−phenol−formaldehyde condensates (SPF), and polycarboxylate superplasticizers (PCs). Because currently there is no agreement on the academic naming of SPs, the same SPs usually has several different names. For example, SMF is also called poly(melamine sulfonate)7,8 or melamine formaldehyde sulfonate.9 SNF is also called poly(naphthalene sulfonate), poly(butyl naphthalene sulfonate),7 naphthalene formaldehyde sulfonate,9 sodium naphthalene sulfonate, naphthalene sulfonate, naphthalene sulfonate formaldehyde condensate, or sodium naphthalene sulfonate formaldehyde. AFS is also called aliphatic superplasticizer or sulfonated acetone formaldehyde. PCs are also called polycarboxylate series superplasticizer,10 carboxylated acrylic ester-grafted copolymer superplasticizer,6 or polycarboxylate ether superplasticizer.11,12 Though they may be known as SPs, their waterreducing ratios have a big difference among them. The waterreducing ratio of SMF, SNF, AFS, and SPF is in the range of 15−25%, and the water-reducing ratio of PCs is in the range of 25−50%. © 2014 American Chemical Society
In addition to the classification above, another is also commonly accepted that divides the water reducers into three generations according to their order of discovery and the waterreducing ratio. The first generation is LS, which was first found from wastewater in sulfite pulping in the 1930s. LS is a modified natural polymer consisting of phenylpropane repeat units with sulfonic, phenolic hydroxyl, and alcoholic hydroxyl groups.1 Though the water-reducing ratio of LS is only about 8% and also cannot significantly improve the mechanical strength of concrete, the effect of LS on concrete inspired people to further discover more novel water reducers. Secondgeneration water reducers, mainly including SMF, SNF, SPF, and AFS, were found between 1960 and 1980.13 They are all polycondensates formed by the cross-linking of formaldehyde. The advantages of second-generation water reducers are their better adaptability to different cements, relative higher waterreducing ratio (15−25%), and inexpensiveness, which result in their extensive application.9 The second-generation water reducers were called SPs. Their dispersion force on cement mainly originates from electrostatic repulsion. But the performance parameters, such as slump retention (0.35), and increase of mechanical strength, cannot reach the requirements of high-performance concrete. In addition, the second-generation SPs are known to gradually release toxic formaldehyde during use because there are many unstable methylols produced by reaction of formaldehyde with amino or hydroxyl groups. 5 Research has therefore focused on developing novel SPs possessing higher water-reducing ratio and without formaldehyde pollution, rather than secondgeneration SPs.14 As a result, in the 1980s, the third-generation Received: Revised: Accepted: Published: 3908
November 8, 2013 February 9, 2014 February 14, 2014 February 14, 2014 dx.doi.org/10.1021/ie403786q | Ind. Eng. Chem. Res. 2014, 53, 3908−3916
Industrial & Engineering Chemistry Research
Article
PCs were found, which have higher water-reducing ratio (25− 50%), superior fluidity, a longer retention effect at lower dosage (about 0.2%), and a lower w/c ratio (28%) at low w/c ratio (0.29). The working mechanism of SCS was revealed through the adsorption behavior of SCS on the cement surface and the zetapotential of cement particles. It was confirmed that the adsorption behavior conforms to the Langmuir isotherm model, and SCS can make cement particles exhibit a high and durable negative charge compared to PCs and SNF. The results demonstrated that the strong dispersion force of SCS
the pore structure, indicating that SCS can markedly reduce the number of large pores (>100 nm) compared with PCs and SNF. Also, SCS can lead to a greater number of smaller pores compared to PCs and SNF. This supports the finding of the greater strength of cement paste and concrete mixed with SCS than that mixed with PCs and SNF. A smaller pore diameter is associated with greater mechanical strength of cement composites. Figure 6 shows the SEM images of hardened cement paste doped with different SPs (SCS, PCs, and SNF) at 28 d. For the blank sample, the SEM image indicates that there are many rodlike crystals in the hardened cement paste, which are mainly cement hydration crystals of fettringite (AFt), calcium hydroxide (CH), monosulfate (AFm), and calcium silicate
Figure 6. SEM images of hardened cement paste with different SPs cured for 28 d: (a) blank sample, (b) SNF 0.9% bwoc, (c) PCs 0.2% bwoc, and (d) SCS 0.4% bwoc (Shengwei 42.5R; w/c of part a is 0.6 and w/c of parts b−d is 0.29). 3915
dx.doi.org/10.1021/ie403786q | Ind. Eng. Chem. Res. 2014, 53, 3908−3916
Industrial & Engineering Chemistry Research
Article
(13) Ma, G. G.; Wang, X. G.; Liang, W. Q.; Li, X. G.; He, Z. Study on early-age cracking of cement-based materials with superplasticizers. Constr. Build. Mater. 2007, 21, 2017−2022. (14) Annika, K.; Karin, M.; Andersson, L. B. Probing the effect of superplasticizer adsorption on the surface forces using the colloidal probe AFM technique. Cem. Concr. Res. 2005, 35, 133−140. (15) Yamada, K.; Ogawa, S.; Hanehara, S. Controlling of the adsorption and dispersing force of polycarboxylate-type superplasticizer by sulfate ion concentration in aqueous phase. Cem. Concr. Res. 2001, 31, 375−383. (16) Lv, S. H.; Duan, J. P.; Gao, R. J.; Cao, Q.; Li, D. Effects of poly(ethylene glycol) branched chain linkage mode on polycarboxylate superplasticizer performance. Polym. Adv. Technol. 2012, 23, 1596− 1603. (17) Yoshioka, K.; Sakai, E.; Daimon, M.; Kitahara, A. Role of steric hindrance in the performance of superplasticizers for concrete. J. Am. Ceram. Soc. 1997, 80, 2667−2671. (18) Chakraborty, S.; Kundu, S. P.; Roy, A.; Adhikari, B.; Majumder, S. B. Effect of jute as fiber reinforcement controlling the hydration characteristics of cement matrix. Ind. Eng. Chem. Res. 2013, 52, 1252− 1260. (19) Peschard, A.; Govin, A.; Pourchez, J.; Fredon, E.; Bertrand, L.; Maximilien, S.; Guilhot, B. Effect of polysaccharides on the hydration of cement suspension. J. Eur. Ceram. Soc. 2006, 26, 1439−1445. (20) Izaguirre, A.; Lanas, J.; Á lvarez, J. I. Behavior of a starch as a viscosity modifier for aerial lime-based mortars. Carbohydr. Polym. 2010, 80, 222−228. (21) Lv, S. H.; Gao, R. J.; Duan, J. P.; Li, D.; Cao, Q. The effects of βcyclodextrin side chains on the dispersing and retarding properties of polycarboxylate superplasticizers. J. Appl. Polym. Sci. 2012, 125, 396− 404. (22) Bian, H.; Plank, J. Effect of heat treatment on the dispersion performance of casein superplasticizer used in dry-mix mortar. Cem. Concr. Res. 2013, 51, 1−5. (23) Patural, L.; Marchal, P.; Govin, A.; Grosseau, P.; Ruot, B.; Deves, O. Cellulose ethers influence on water retention and consistency in cement-based mortars. Cem. Concr. Res. 2011, 41, 46−55. (24) Lv, S. H.; Cao, Q.; Gao, F. T. Structure and characterization of sulfated chitosan superplasticizer. J. Am. Ceram. Soc. 2013, 96, 1923− 1932. (25) Shahid-ul-Islam, M. S.; Mohammed, F. Green chemistry approaches to develop antimicrobial textiles based on sustainable biopolymersA review. Ind. Eng. Chem. Res. 2013, 52, 5245−5260. (26) Rouessac, F.; Rouessac, A. Chemical Analysis; Wiley: New York, 2000.
originates from the synergy of strong steric hindrance and electrostatic repulsion, which is attributed to its ring-shaped linear main chains with carboxyl and sulfonate groups. The research results demonstrated that SCS has a great similarity in molecular structure and application performance with PCs, and meanwhile, SCS exceeds PCs with regard to retarding effect. Currently, the green concrete and the related superplasticizers have caught more and more attention. This study demonstrates that a high-performance superplasticizer may be synthesized using a renewable natural green polymer and also provide a novel green superplasticizer.
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The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This research was funded by the China National Nature Science Foundation 21076121 research project. REFERENCES
(1) Xu, S. L.; Zhang, B. W.; Chen, Z. R.; Yu, J. H; Evans, D. G.; Zhang, F. Z. A general and scalable formulation of pure CaAl-layered double hydroxide via an organic/water solution route. Ind. Eng. Chem. Res. 2011, 50, 6567−6572. (2) Ji, D.; Luo, Z. Y.; He, M.; Shi, Y. J.; Gu, X. L. Effect of both grafting and blending modifications on the performance of lignosulphonate-modified sulphanilic acid−phenol−formaldehyde condensates. Cem. Concr. Res. 2012, 42, 1199−1206. (3) Lu, S. H.; Liu, G.; Ma, Y. F.; Li, F. Study on synthesis and application of a new vinyl graft copolymer superplasticizer. J. Appl. Polym. Sci. 2010, 117, 273−280. (4) Lou, H. M.; Lai, H. R.; Wang, M. X.; Pang, Y. X.; Yang, D. J.; Qiu, X. Q.; Wang, B.; Zhang, H. B. Preparation of lignin-based superplasticizer by graft sulfonation and investigation of the dispersive performance and mechanism in a cementations system. Ind. Eng. Chem. Res. 2013, 52, 16101−16109. (5) Lei, L.; Plank, J. Synthesis, working mechanism and effectiveness of a novel cycloaliphatic superplasticizer for concrete. Cem. Concr. Res. 2012, 42, 118−123. (6) Lewis, J. A.; Matsuyama, H.; Kirby, G.; Sherry, M.; Francis, J. Y. Polyelectrolyte effects on the rheological properties of concentrated cement suspensions. J. Am. Ceram. Soc. 2000, 83, 1905−1913. (7) Kılınckale, F. M.; Dogan, G. G. Performance of concretes produced with superplasticizer. J. Appl. Polym. Sci. 2007, 103, 3214− 3219. (8) Plank, J.; Pöllmann, K.; Zouaoui, N.; Andres, P. R.; Schaefer, C. Synthesis and performance of methacrylic ester based polycarboxylate superplasticizers possessing hydroxy terminated poly(ethylene glycol) side chains. Cem. Concr. Res. 2008, 38, 1210−1216. (9) Aiad, I.; Hafiz, A. A. Structural effect of prepared and commercial superplasticizers on performance of cement pastes. J. Appl. Polym. Sci. 2003, 90, 482−487. (10) Plank, J.; Sachsenhauser, B. Experimental determination of the effective anionic charge density of polycarboxylate superplasticizers in cement pore solution. Cem. Concr. Res. 2009, 39, 1−5. (11) Burak, F.; Hasan, S. Effect of chemical structure of polycarboxylate-based superplasticizers on workability retention of self-compacting concrete. Constr. Build. Mater. 2008, 22, 1972−1980. (12) Frank, W.; Stefan, B.; Joachim, P.; Thomas, G. Effects of the molecular architecture of comb-shaped superplasticizers on their performance in cementitious systems. Cem. Concr. Comp. 2007, 29, 251−262. 3916
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