粉煤灰对水泥浆体的剪切变稀和剪切增稠作用.pdf

?43?8?2015?8?Vol.43?No.8 Aug?2015 JOURNAL OF THE CHINESE CERAMIC SOCIETY http:/ DOI?10.14062/j.issn.0454-5648.2015.08.00?(?410075)?RHEOLAB QC?HERSCHEL-BULKEY(H-B)?1?(?crit)?(?crit)?(?min)?2?crit?crit?min?40%?50%?50%?TU528?A?0454?5648(2015)08?0000?07?Effects of Fly Ash on Shearing Thinning and Thickening of Cement Paste XIE Youjun,CHENG Xiaobo,MA Kunlin,Fen Jin,LONG Guangcheng(School of Civil Engineering,Central South University,National Engineering laboratory for Construction Technology of High Speed Railway,Key Laboratory of Engineering Structure of Heavy Railway,Ministry of Education,Changsha 410075,China)Abstract:The rheological curves of cement pastes with different fly ash(FA)contents were determined in a model RHEOLAB QC rotation viscometer.The data obtained were calculated by the Herschel-Bulkey(H-B)rheological model.The results show that there is an inflection point in rheological curve when shear rate increases.The corresponding rheological parameters of the inflection point are critical shear rate(?crit),critical shear stress(?crit)and minimum viscosity(?min),respectively.The pastes in left and right sides of the inflection point are shear thinning stage and shear thickening stage.Pure cement pastes have shear thinning even at a high shear rate.However,the addition of fly ash into cement paste decreases?crit,?crit and?min.When fly ash content is more than 40%,critical shear rate is rather low,resulting in shear thinning.At shear thinning stage,the increase of fly ash content can decrease the rheological index when fly ash content is less than 50%,and the increase of fly ash content can increase the rheological index when fly ash content is beyond 50%.At shear thickening stage,the rheological indexes increases with increasing fly ash content,leading to the development of the degree of shear thickening.Key words:rheology,cement,fly ash,shear thinning,shear thickening?1-2?3-4?2015?02?30?2015?05?19?973?(2013CB036201)?(2014G012)?(2014JSJJ013)?(1964?)?(1976?)?Received date:2015?02?30.Revised date:2015?05?19.First author:XIE Youjun(1964?),male,Ph.D.,Professor.E-mail: Correspondent author:MA Kunlin(1976?),male,Ph.D.,Associate Professor.E-mail:Mark- 2?J Chin Ceram Soc,2015,43(8):1?7 2015?5-7?8?9?10-12?13-15?1?1.1?(C)?P.O 42.5?3.12 g/cm3?344 m2/kg?C3A?7.22%?45?m?18.5%?(FA)?F?2.45 g/cm3?486 m2/kg?45?m?10.3%?(SP)?18.1%?25.4%?(W)?1?2?3?4?1?Table 1 Physical properties and chemical composition of cement(C)Density/(kgm?3)Specific surface area/(m2kg?1)Mass fraction w/%Setting time/min Compressivestrength/MPa SiO2 Fe2O3 Al2O3 CaO MgO SO3 Alkali IL Initial Final 3 d 28 d 3 120 344 23.3 3.2 4.8 56.3 4.2 2.2 0.47 2.4 149 211 25.1 46.8?2?Table 2 Physical properties and chemical composition of fly ash(FA)Density/(kgm?3)Specific surface area/(m2kg?1)Ratio of water needing/%w/%SiO2 Fe2O3 Al2O3 CaO MgO SO3 Alkali IL 2450 486 97 51.8 5.0 26.4 4.1 1.0 2.0 0.52 3.09?3?Table 3 Particle size distribution of C and FA Material DV,0.5/?m DV,0.9/?m DV,0.1/?m Specific surface area/(m2kg?1)C 16.211 36.098 2.670 344 FA 8.249 20.505 3.280 486?43?8?3?4?Table 4 Mix proportion of cement compound pastes Specimen No.Mix proportion/%Cement Fly ash Water Super plasticizer P1 100 0 28 0.4 P2 80 20 28 0.4 P3 70 30 28 0.4 P4 60 40 28 0.4 P5 50 50 28 0.4 P6 40 60 28 0.4 P7 0 100 28 0.4 1.2?1)?(252)?(705)%?U400?4?500 r/min?1 600 r/min?2 min?30S?Anton Paar?Rheolab QC?(?)?2)?Herschel-Bulkley(H-B)?2?(1)?00,=1?n?n1?n?3)?Rise-2202?2?2.1?1?5?H-B?1?(a)?vs.?(b)?vs.?is shear rate;?is shear stress;?is plastic viscosity.?1?Fig.1 Rheological curves of cement paste and fly ash paste?1a?5?(M?N?)?(n)?1?(n)?1?1b?4?J Chin Ceram Soc,2015,43(8):1?7 2015?5?(?crit)?(?min)?1?5?169 S?1?50.0 Pa?0.297 Pas?94 S?1?19.4 Pa?0.205 Pas?169 S?1?94 S?1?0.297 Pas?0.205 Pas?(n)?0.837 4?0.720 9?(n)?1.298?1.875?5?H-B?R?0.99?2.2?2?6?H-B?P1?P7?P2?P6?20%?30%?40%?50%?60%?2a?2b?50%?2c?2d?50%?5?Table 5 Rheological parameters of cement paste and fly ash paste Specimen No.convex curve segment Inflection point Concave curve segment?0/Pa?/(Pas)n R?crit/S?1?crit/Pa?min/(Pas)?0/Pa?/(Pas)n R P1 2.925 0.5448 0.8374 0.9956 169 50.0 0.297 6.069 0.04499 1.298 0.9994 P7 4.371 0.5921 0.7209 0.9942 94 19.4 0.205 9.578 0.0105 1.875 0.9998?0 is yield stress;?is plastic viscosity;n is rheological index;R is correlation index;?crit is critical shear rate;?crit is critical shear stress;?min is minimum plastic viscosity.?2a?6?50%?1?2b?6?2c?6?50%?2d?6?50%?50%?3a?3b?(n?1)?(n?1)?3a?50%?43?8?5?n?0.297 4?(?4?5?)?11?50%?P2?P7?P1?(a)?vs.?(b)?vs.?(c)?vs.?(d)?vs.?Fly ash content are less than 50%.?2?Fig.2 Rheological curves of cement paste and different fly ash paste content?6?Table 6 Rheological parameters of cement paste with different fly ash content Specimen No.convex curve segment Inflection point concave curve segment?0/Pa?/(Pas)n R?crit/S?1?crit/Pa?min/(Pas)?0/Pa?/(Pas)n R P2 0.559 0.9113 0.6523 0.9987 83 17.2 0.207 0.3866 0.01198 1.3489 0.9998 P3 0.137 1.124 0.576 0.9935 78 13.8 0.177 0.693 0.00491 1.526 0.9979 P4 0.0818 2.873 0.3221 0.9968 49 4.8 0.096 0.214 0.00806 1.516 0.9947 P5 0.0813 2.203 0.2974 0.9921 31 1.9 0.058 0.4159 0.00248 1.6310 0.9999 P6 0.119 0.1969 0.6205 0.9929 41 4.9 0.117 1.6565 0.01134 1.6255 0.9998 6?J Chin Ceram Soc,2015,43(8):1?7 2015?(a)Shear thinning stage (b)Shear thickening stage?3?(n)?Fig.3 Relationship between fly ash content and rheological index(n)?3b?1?6?0?20%?30%?40%?50%?60%?100%?169?83?78?49?31?41?94 S?1?50%?40%?60%?40%?50%?96?58 mPas?4?SEM?Fig.4 SEM image of FA?5?SEM?Fig.5 SEM image of cement 3?1)?1?Herschel-Bulkley(H-B)?2)?43?8?7 40%?3)?50%?50%?1?.?J.?,2011(9):21?26.Huang Daneng.J Concr World(in Chinese),2011(9):21?26.2?,?.?J.?,2013(4):9?13.ZHANG Xiong,ZHANG Lei.Fly Ash Comprehensive Utilization(in Chinese),2013(4):9?13.3?,?,?,?.SiO2?J.?,2014,42(3):296?301.LU Chenglong,PENG Weike,YUAN Wenjie,et al.J Chin Ceram Soc(in Chinese),2014,42(3):296?301.4 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