1、Designation: C1749 12Standard Guide forMeasurement of the Rheological Properties of HydraulicCementious Paste Using a Rotational Rheometer1This standard is issued under the fixed designation C1749; the number immediately following the designation indicates the year oforiginal adoption or, in the cas
2、e of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers description of several methods tomeasure the rheological properties of fr
3、esh hydraulic cementpaste. All methods are designed to determine the yield stressand plastic viscosity of the material using commerciallyavailable instruments and the Bingham model. Knowledge ofthese properties gives useful information on performance ofcement pastes in concrete.1.2 The values stated
4、 in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This guide offers an organized collection of informationor a series of options and does not recommend a specificcourse of action. This document cannot replace education orexperience and should
5、be used in conjunction with professionaljudgment. Not all aspects of this guide may be applicable in allcircumstances. This ASTM standard is not intended to repre-sent or replace the standard of care by which the adequacy ofa given professional service must be judged, nor should thisdocument be appl
6、ied without consideration of a projects manyunique aspects. The word “Standard” in the title of thisdocument means only that the document has been approvedthrough the ASTM consensus process.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It i
7、s theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2C305 Practice for Mechanical Mixing of Hydraulic CementPastes and Mortars of Plast
8、ic ConsistencyC511 Specification for Mixing Rooms, Moist Cabinets,Moist Rooms, and Water Storage Tanks Used in theTesting of Hydraulic Cements and ConcretesC1005 Specification for Reference Masses and Devices forDetermining Mass and Volume for Use in the PhysicalTesting of Hydraulic CementsC1738 Pra
9、ctice for High-Shear Mixing of Hydraulic Ce-ment Pastes2.2 Other Standards:API Recommended Practice 10B Testing Well Cements,American Petroleum Institute, Washington, DC (1997)ISO 10426-2 (2003) Petroleum and Natural GasIndustriesCements and Materials for Well CementingPart 2: Testing of Well Cement
10、sSection 5.23. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology C125 and C219.3.2 Definitions of Terms Specific to This Standard:3,43.2.1 apparent viscosity, nthe shear stress divided by rateof shear, in units of Pa.s.3.2.2 plastic viscosity, nin the p
11、lastic (Bingham) model,the slope of the shear stress shear rate curve, in units of Pa.s.3.2.3 thixotropy, na decrease of the apparent viscosityunder constant shear stress or shear rate followed by a gradualrecovery when the stress or shear rate is removed.3.2.4 yield stress, nthe stress correspondin
12、g to the transi-tion from elastic to plastic deformation, in units of Pa; it is alsoreferred to as the stress needed to initiate flow. It would becalculated using the Bingham model in this guide.3.2.5 Bingham model, na rheological model for materialswith non-zero yield stress and a linear relationsh
13、ip betweenshear rate and shear stress, following the equation: t = tB+ghpl; where tBYield stress in Pa, gShear rate in 1/s, t Shearstress in Pa, and hplPlastic viscosity in Pa.s.4. Significance and Use4.1 Rheological properties determined using this guide in-clude plastic viscosity and yield stress
14、as defined by theBingham model and apparent viscosity.1This guide is under the jurisdiction of ASTM Committee C01 on Cement andis the direct responsibility of Subcommittee C01.22 on Workability.Current edition approved Feb. 1, 2012. Published March 2012.2For referenced ASTM standards, visit the ASTM
15、 website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3H.A. Barnes, J.F. Hutton and K. Walters,An Introduction to Rheology, Elsevier(1989).4Hackley V.A., Ferrari
16、s C.F., “The Use of Nomenclature in Dispersion Scienceand Technology” NIST Recommended Practice Guide, SP 960-3, 2001.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.2 Rheological properties provide information about theworkability
17、 of cement paste. As an example, the yield stressand plastic viscosity indicate the behavior of a specific cementpaste composition. As another example, the apparent viscosityindicates what energy is required to move the suspension at agiven strain rate. This test may be used to measure flowabilityof
18、 a cement paste or the influence of a specific material orcombination of materials on flowability.4.3 Rheological properties may be sensitive to the proce-dure being used. This guide describes procedures that areexpected to provide reproducible results.5. Summary of Guide5.1 This guide provides proc
19、edures for the determination ofrheological properties of fresh cement paste using a rotationalrheometer with geometries, such as parallel plate, narrow-gapand wide gap concentric cylinders.6. Interferences6.1 Rheological properties may be sensitive to the proce-dure, so a comparison of properties ob
20、tained using differentprocedures is not recommended, unless relative viscosity (ratiobetween the plastic viscosity of a materials and the plasticviscosity of a reference material, both measured using the samerheometer) is considered.6.2 Rheological properties may be sensitive to the shearhistory of
21、the sample, so comparison of properties usingdifferent mixing procedures is not recommended.6.3 Paste mixtures (water and cement particles) that are veryfluid may yield erroneous data using this procedure due tosettling of particles. Such settling is especially likely in shearthinning and thixotropi
22、c mixtures.6.4 Larger cement particles or aggregations of cementparticles may block flow in a narrow-gap rheometer andthereby increase the shear stress. The gap between the shearingsurfaces needs to be selected with consideration of the particlesize of the material to be tested. Depending on the gap
23、 size, itmay be necessary to remove larger particles by sieving orotherwise prevent segregation.6.5 Incorporation of air in the paste during mixing reducesviscosity and increases flow.6.6 The time of testing after initial contact of cement withwater influences the results.7. Apparatus7.1 General Des
24、cription:7.1.1 The apparatus shall be a rotational rheometer in whichthe sample is confined between two surfaces (called theshearing surfaces), one of which is rotating at a constantrotational speed, V and the other being stationary. The appa-ratus shall measure both the rotational speed and the tor
25、querequired to maintain that speed.7.1.2 The rheometer geometry shall provide a simple shear-ing flow (laminar, without turbulence). Allowable geometriesand their equations for computing stress and strain rate fromthe measured values of rotational speed and torque are de-scribed in section 7.4.7.2 T
26、he rotational rheometer shall be capable of measuringshear stress at strain rates in the range from 0.1 s-1to 600 s-1.The range of shear rates will be selected by the operatordepending on the geometry used. At least five measurementsneed to be recorded.NOTE 1Most experiments found in the literature
27、do not use the fullrange of shear rates prescribed here. For example, most parallel platemeasurements are done between 0.1 s-1to 50 s-1. The selection of theshear rate range might take into account the exact geometry of therheometer.7.3 Regularly check the calibration and zeroing of theapparatus, as
28、 discussed in section 7.9.7.4 Rheometer Geometry:7.4.1 The rheometer geometries described in this sectionprovide simple shearing flow, essential for reliable computa-tion of stress and strain rates. The equation for computation ofstress and strain rates is given for each geometry.NOTE 2The following
29、 assumptions were made to develop the equa-tions that appear in this section: (1) the fluid is homogeneous, (2) slip atthe wall is negligible, and (3) the flow regime is laminar.7.4.2 Selection of the geometry of the rheometer. Threegeometries are described here: narrow-gap concentric cylin-ders, wi
30、de-gap concentric cylinders, and parallel plates. Theselection of the geometry should be based on the type ofrotational rheometer available. One criterion to select betweenthe narrow-gap and the wide-gap should be based on themaximum size of the particles in the cement tested.7.4.2.1 Narrow-Gap Conc
31、entric CylinderWith this typeof rheometer, the sample is confined between two concentriccylinders of radii R1and R2(R2R1), one of which, the rotor, isrotating at a constant rotational speed V and the other isstationary. The rotation of the rotor in the presence of thesample produces a torque that is
32、 measured at the wall of theinner cylinder. The cylinder radii should be selected such thatthe shear stress is uniform across the gap. This condition isassumed to be satisfied if:SR1R2D.5 0.92 (1)where R1is the radius of the inner rotating cylinder (m) andR2is the radius of the outer stationary cyli
33、nder (m).5To prevent slip (development of a liquid layer at the wall ofthe rotating cylinder that produces an anomalously low stress),the surface of cylinders may be serrated or at least renderedrough by attaching a sand paper, sand blasting, or othermethods that roughen the surface such as serratio
34、n.The nominal shear rate and stress are calculated at the innercylinder wall by the following expression:g5R23V1R2 R1(2)where gis strain rate (s-1) and V1is rotational speed at theinner cylinder (r/s). The nominal shear stress is calculated atthe inner cylinder wall by the following expression:t5G2p
35、R12L(3)5DIN 53019-1:2008, ViscometryMeasurement of viscosities and flow curvesby means of rotational viscometersPart 1: Principles and measuring geometry.C1749 122where t is shear stress (Pa), G is torque (Nm), L is cylinderlength (m), and R1is the inner radius (m). These equationsassume that the sl
36、urry is homogeneous, the shear stress isuniform in the gap, the flow regime in the gap is laminar, andslip at the wall is negligible.7.4.2.2 Wide-Gap Concentric CylinderThis type of rhe-ometer is similar to the narrow-gap concentric cylinder de-scribed in section 7.4.2 except that there is no limit
37、on the gapvalue and the gap is larger. Computation of strain rate andstress is simplified if it is assumed that the material follows apower-law model. In that case, the nominal shear rate, g,iscalculated at the inner cylinder wall by the following expres-sion:g52 3V1n1b2/n!(4)where gis strain rate (
38、s-1), V1is the rotational speed at theinner cylinder (rad/s), b is the ratio of the inner to the outerradius, and n is the power-law exponent. A procedure fordetermining the value of n is presented elsewhere.3Nominalshear stress, t, is calculated at the inner cylinder wall by thefollowing expression
39、:t5G2pR12L(5)where t is shear stress (Pa), G is torque per unit length (Nm),L is cylinder length (m), and R1and R2are inner and outercylinder radii (m).Some concentric cylinder rheometers use an extreme widegap such that the radius of the outer cylinder approachesinfinity and (1-b2/n) approaches uni
40、ty. This type of rheometernormally operates only at moderately low shear rates, typically0.1 s-1to 10 s-1. For a material following a power-law model,the nominal shear rate is calculated at the inner cylinder wallby the following expression:g52 3V1n(6)where gis strain rate (s-1), V1is the rotational
41、 speed of theinner cylinder (rad/s), and n is the power-law exponent.Nominal shear stress, t, is calculated at the inner cylinder wallby the following expression:t5G2pR12L(7)where t is shear stress (Pa), G is torque (N.m), L is cylinderlength (m), and R1is inner cylinder radius (m).7.4.2.3 Parallel
42、PlateIn this type of rheometer the sampleis held between two parallel horizontal plates, each equal andcircular cross section. The plates may be serrated to avoidslippage. When one of the plates is rotating and the other isstationary, the shear rate varies from zero at the center to amaximum at the
43、rim, and the value at the rim is:g5R 3V1h(8)where gis strain rate (s-1), R is the plate radius (m), V1is therotational speed (rad/s), and h is the gap between the two plates(m). Viscosity is given by:h53hG2pR4V1S1 11dlnG3dlnV1D(9)where h is viscosity (Pa.s) and G is the torque (N.m).7.5 GapThe gap b
44、etween the shearing surfaces of therheometer should be wide enough that the sample is homoge-neous throughout or be of the same magnitude of the distancebetween aggregates in concrete (typically 0.4 mm). If the gapis too narrow relative to the size of particles in the cement paste(less than 10 times
45、 the maximum particles size), the torque willbe very high or even the plate will lock and not rotate.7.6 SlippageSlippage can occur if the shearing surfacesare smooth, due to the formation of layer of water near thesurface. If slippage occurs, the torque measured is smaller thanit should be. It coul
46、d be even zero. Therefore, some precautionshould be taken to avoid slippage by serration of the shearingsurfaces. It can be done either by gluing a sand paper, or bysand blasting the surfaces or by serration of the surface withgrooves or a pattern.7.7 EvaporationPrevent evaporation of water from the
47、paste by covering the paste with a vapor barrier or a water-saturated material.7.8 Temperature ControlControl the temperature to thenearest 2C. The temperature may be selected to reflect thetemperature at which the cement paste would be used in thefield.7.9 VerificationPeriodically follow the proced
48、ures sug-gested by the manufacturer to assure the repeatability of themeasurements. Using any standard oil, as recommended by therheometer manufacturer, would allow detection of malfunc-tioning of the instrument.68. Procedure8.1 Details of the test procedure may be varied as necessaryto suit the spe
49、cific apparatus.8.2 Prepare sufficient cementitious mixture (Note 3)tofillthe rheometer tool selected. Mix the paste following a methodthat ensures full dispersion of the cement in water, such asPractice C1738. Describe the mixing method in the report(Note 4). Record the time of first contact between water and thecementitious materials.NOTE 3There is a practical limit to the water-to-cement ratio (w/c)that can be tested in a rheometer. If the w/c is too low, the paste willexceed the upper torque limit of the rheometer and may not maintaincontact
