K. H. Khayat 1 and A. Yahia 1 Simple Field Tests to Characterize Fluidity and Washout Resistance of Structural Cement Grout REFERENCE: Khayat, K. H. and Yahia, A., ‘‘Simple Field Tests characteristics of cement suspensions or to evaluate their fluidity to Characterize Fluidity and Washout Resistance of Structural and injectability. This includes precise methods for the determina- Cement Grout,’’ Cement, Concrete, and Aggregates, CCAGDP, Vol. tion of rheological profiles at low and high shear rates as well as 20, No. 1, June 1998, pp. 145–156. simple tests to evaluate fluidity and ease of pumping, injection, and spreading. The determination of rheological parameters often ABSTRACT: The ability to assess rheological properties of neat cement grout, such as those used in structural repair and for filling involves the use of a coaxial cylinder viscometer to measure appar- post-tension ducts, is of special interest for the evaluation of the ease ent viscosities at various shear rates that may be encountered during of pumping, spreading into place, and filling of narrow spaces. There mixing, pumping, injection, and spreading into place. is an increasing need to identify dependable and simple test methods Unlike Newtonian fluids, such as water, where the rheological that can characterize the consistency of specialty cement grouts and reflect variations in rheological properties during handling and place- behavior can be characterized only by determining the viscosity, ment. Several tests can be used to evaluate the rheological characteris- a high-performance cement grout behaves as a Bingham fluid. This tics of a cement grout suspension, including precise methods for the is characterized by the presence of a yield value ( 0 ) after which determination of rheological parameters and simple procedures to the plastic viscosity remains constant. The flow of any material is assess fluidity. Rheological properties can be accurately determined initiated whenever the applied force exceeds the yield stress. Such by using a coaxial cylinder viscometer. However, the use of such a flow causes a deformation of the material that is characterized by viscometer is mainly limited to the laboratory, and simple methods including the mini-slump spread and the modified Marsh cone tests a relative displacement of the particles each-to-others. Such grout are usually employed in the field to verify the consistency for quality exhibits a pseudo-plastic behavior where the apparent viscosity control. decreases with the increase in shear rate. This paper attempts to establish relationships between rheological The evaluation of grout fluidity can be carried out using simple parameters and fluidity values obtained using simple test methods. test methods, such as the mini-slump test and the modified Marsh Relationships are also determined between the wash-out resistance of structural cement grout and various fluidity and rheological parameters. cone method. Such tests are often used to optimize cement grouts The derived relationships are based on a wide variety of cement grouts and characterize their fluidity and are also used for quality control covering up to 210 data points. The various grouts were prepared with in the field to monitor the variations in consistency during place- W/C ranging between 0.30 and 0.50, Type I and III portland cements, ment. In contrast to the viscometer technique, the mini-slump and as well as various silica fume replacement values (up to 8% by mass), Marsh cone test methods are not completely developed, in the blast-furnace slag contents of 20 to 60%, fly ash substitutions of 10 to 30%, and limestone filler replacements of up to 30%. The investi- sense that the shear rate in which these tests are carried out is not gated grouts incorporated melamine- and naphthalene-based high-range well determined. Experiments using these tests do not therefore water reducer, welan gum and cellulose-based viscosity-modifying provide information concerning the rate of shear that the grout is admixtures, as well as set-retarding admixture. subjected to during the testing. Test results highlight the difficulties of relying on a single empirical This paper compares the fluidity values obtained with the mini- test to evaluate the fluidity of a given grout. Correlations between slump and modified March cone test methods to the various rheo- various simple measurements of fluidity and wash-out mass loss and apparent viscosities determined at different shear rates indicate that the logical parameters. The suitability of such tests to describe the mini-slump and wash-out mass loss measurements correspond well to rheological behavior of structural grouts is evaluated. Correlations viscosities determined at low-shear rates (5.1 s 1 ). In contrast, the between various direct and indirect means of evaluating rheologi- modified Marsh cone measurement corresponds well to viscosity deter- cal parameters are therefore presented. Correlations between rheo- mined at high-shear rates ranging between 340 and 510 s 1 . Because logical parameters and wash-out mass loss values determined using of the pseudo-plastic behavior of structural cement grouts, field quality control tests should include fluidity assessment at low and high shear a simple proposed method are also established. rates to adequately evaluate the rheological behavior of the grouts. Experimental Program KEYWORDS: cement grout, flow time, mini-slump, rheology, vis- cometer, viscosity, wash-out resistance, yield value Materials and Mixture Proportions All grout mixtures considered in this study were prepared using An understanding of the interparticle forces that control the flow the same mixing sequence and tested for rheological parameters, behavior of cement grout can be assessed through rheological stud- fluidity, and the wash-out mass loss. Three different operators were ies. Various test methods can be used to determine the rheological involved in carrying out the various tests in order to take into consideration the inherent variations due to the operator. 1 Civil Engineering Department, University of Sherbrooke, Sherbrooke, As shown in Table 1, three types of portland cement were used. Quebec, Canada. These are a blended silica fume cement containing approximately  1998 by the American Society for Testing and Materials 145 www.astm.org Copyright by ASTM Int'l (all rights reserved); Wed May 27 15:08:42 EDT 2015 Downloaded/printed by Missouri Univ of Science (Missouri Univ of Science ) pursuant to License Agreement. No further reproductions authorized.