Brite EuRam Proposal No. BE Brite EuRam Contract No. BRPR-CT

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1 Page 1(2) FINAL REPORT OF TASK 3 Doc. No.: Rev. No.: 1 Date: Task No: 3 Task name: Rheology Author: Dr. T. SedranPartner: LCPC

2 Page 2(2) Table of content: 1. Objectives of the task Rheology of paste and fine mortar Effect of the couple cement type/superplasticizer Effect of the cement an filler types Rheology of concrete Tests done at Betongindustri Tests done at LCPC Conclusions ANNEX 1 BMLWO ANNEX 2 BTRheom

3 Page 3(2) 1. OBJECTIVES OF THE TASK 3 The concrete can be considered as a Bingham fluid with the following behavior law: τ = τ + µ γ & where &γis the strain rate (in 1/s), τ the shear stress (in Pa). Then the concrete behavior is entirely characterized by its shear yield stress τ (in Pa) and the plastic viscosity µ' (in Pa s). These parameters are intrinsic properties of concrete and could be used in finite element calculations to predict any flow of the concrete. The objectives of the task at the beginning of the project (see the proposal to European commission) were the following: to give a full characterization of the rheological behavior of fresh concrete using concrete rheometers available within the consortium: namely the BML viscometer and the BTRHEOM rheometer (see annex 1 and 2). The BTRHEOM is a plane/plane rheometer which measures directly the τ and µ' values. The BML is a coaxial cylinder viscometer which measures the relationship between the torque T(Nm) and the rotation speed N(rps) applied to the outer cylinder: T=g+h N With this apparatus the behavior of the concrete is determined indirectly by the g-value (in Nm) and the h-value (in Nm s). The aim was also to modify the BTRHEOM rheometer, to be able to determine the rheology of (SCC) in both infinite and congested medium. The fundamental properties measured were expected to allow us to predict the behavior of SCC in a real structure; to find relationships with the workability tests developed within task 2 (mainly the slump flow test). The underlying idea is to see if the rheological properties can be evaluated by a simple workability test which is easier to handle than a rheological test for control test on construction site. In fact, the main goal of the task was to furnish rheological data of to define a set of requirements in terms of fresh concrete and to develop a mix design process within task 5. The work done within this task mainly consists in the measurement of the shear yield stress and plastic viscosity of different recipes of SCC (with various aggregates, superplasticizers, viscosity agent etc...). Complementary tests have also been done to characterize more precisely the rheological behavior of paste and mortar extracted from SCC to select good combinations of components. The main output of the task is then a collection of bulk data presented in the different sub-task reports referred in annexes. A major part of the analysis of these results have been done in the task 5 final report. So in order to avoid repeating the content of the different reports, the present final report simply makes a short summary of each sub-task. 3

4 Page 4(2) 2. RHEOLOGY OF PASTE AND FINE MORTAR Some tests have been made on paste or fine mortar in order to be able to study the influence of different parameters without using a lot of material 2.1. Effect of the couple cement type/superplasticizer (See annex 3-A and 4-B) This study was proceeded at BetongIndustri and aimed at studying the influence of two types of superplasticizers, Sikament 1 and Cementa Melcrete, on the rheological behavior of paste made of different cements with varying dihydrate/hemihydrate ratii. Three cements were made in laboratory and the fourth was one ordinary Portland type (Slite Std P). These four cements had almost the same Blaine surface. The tests were also made on a rapid cement (Slite SH) with a higher Blaine surface. In order to be representative of paste in SCC, a constant content of limestone filler was used as well as a constant amount of viscosity agent (Sika UCS 1 dosed at,1%). Two different percentages for each superplasticizer were tested for each cement. A reference test was also done without superplasticizer nor viscosity agent. A Bohlin Controlled Stress Rheometer was used to study the rheological behaviour of the pastes. The shear yield stress at rest was determined by increasing the torque, the shear yield stress and the plastic viscosity were determined when the speed gradient was decreasing. The measurements were made at 2, 2 and 4 min. In the same time the paste workability was determined at 2 min. with a mini slump-cone A relation ship was found between the shear yield stresses and the mini slump (see figure 1) Correlation between yield stress and minislump Yield stress (Pa) y = 16277x -1,69 R 2 =,6871 Initial Yield stress (Pa) 2 min. Interpolated Yield stress (Pa) 2 min. Potens (Initial Yield stress (Pa) 2 min.) Potens (Interpolated Yield stress (Pa) 2 min.) 4 2 y = x -2,3917 R 2 =, Minislump (mm) Fig 1- The rheological measurements allows to select more precisely a couple cement/ superplasticizer. The influence of the dihydrate content of the cement can be seen on the figure 2a and 2b. Moreover, one can deduce that for a given shear yield stress (or mini slump), the 4

5 Page 5(2) Sikament 1 leads to higher viscosity. Of course the question remains how the two properties affects the behavior of fresh SCC (in terms of slump flow, viscosity, segregation...) Plastic viscosity at 2 min (Pa s) Sika 2.% Sika 1.5% Mel 2.5% Mel 1.875% ref Yield stress extrapolated at 2 min (Pa) Sika 2.% Sika 1.5% Mel 2.5% Mel 1.875% ref % Dihydrate % Dihydrate Fig 2a and 2b Effect of the cement an filler types (see annex 4) This study was proceeded at CBI and aimed at clarifying the differences, from the rheological point of view, between the cement used in concrete studies at LCPC and the cements used in Sweden within this project. The rheology of fine mortars made of the French cement Gaurain mixed with seven different dolomite fillers have been measured with a Haake RV2 coaxial cylinder viscometer. The main differences between the filler was their size distribution. The water to binder ratio was kept constant at,45. These results have been compared to the results obtained with the two Swedish cements StdP Slite and StdP Degerhamn. The particle fineness of Gaurain lies in between the Swedish cements of which StdP Slite is finer. The difference in rheology according to the Bingham model is not very big for the fine mortars depending on cement type. However, the difference that can be measured is more significant when the finer filler is used. When cements are combined with the dolomite filler Mya C, which have earlier been tested in SCC, the results predict more need of superplasticizer when StdP Degerhamn is used, compared to the other cements. Clear relations between rheology parameters and both fineness modulus and median particle size, can be drawn for the three cements respectively (see figures 3 and 4). The difference in relationship for each cement respectively cannot fully be explained. Difference in flocking behaviour and/or particle shape are two possible reasons. 5

6 Page 6(2) 6 Yield stress [Pa] StdP Slite StdP Degerhamn Gaudrain 1 1,3 1,4 1,5 1,6 1,7 1,8 1,9 Fineness modulus, FMf 6 Fig 3-5 StdP Slite Gaudrain StdP Degerhamn Yield stress [Pa] d5 [microns] Fig 4-3. RHEOLOGY OF CONCRETE 3.1. Tests done at Betongindustri (see Annex 5) This study has been proceeded in Betongindustri. The main tests done were: Slump flow test (final slump flow and T5) L box Rheological measurements with the BML viscometer (determination of the g and h values). 6

7 Page 7(2) The main varying parameters were the following: the shape of the aggregate (crushed or natural). Local materials ( - 8 mm and 8-16 mm ) in Stockholm region were examined. The -8 mm aggregates were Riksten, Underås (both natural) and Olunda ( crushed ). The 8-16 mm aggregates were Riksten (natural) and Olunda (crushed ). the coarse aggregate content (39, 42 and 45 % of total aggregate content) Some complementary tests have been done with different cement, filler, water, superplasticizer and viscosity agent contents. Correlation between slumpflow and measured g-value obtained during this study is plotted in the figure 5. The yield stress seems to have an unclear relationship with slumpflow. However a high slumpflow gives a lower g-value. Correlation between yield stress and slumpflow,6,5,4 Yield stress, Nm,3,2 y = -,39x + 2,7264 R 2 =,3879, ,1 Slumpflow, mm Fig 5- Correlation between T5 and measured h-value (BML) is plotted in the following figure. The measured viscosity in BML seems to have an unclear relationship with T5. However a high T5 gives a high h-value. 7

8 Page 8(2) Correlation between viscosity and T y = 3,9326x,6352 R 2 =,4124 h-value, Nms ,5 1 1,5 2 2,5 3 3,5 4 4,5 5 T5, sec. Fig 6- The scattering of these relationships may be partially explained by uncertainties occuring when using the BML-viscometer and the Abrams cone. Below some possible explanations are made for these errors: separation in the concrete mix; In this investigation moisten aggregate was used and variations of humidity in aggregate can not be totally controlled. SCC without viscosity agent is sensitive to variations in water content; The calculation of the regression line affects the g-value in a way which sometimes gives a negative value; The BML measurement as well as other methods will have some uncertainty. An estimation for ordinary concrete are: g-value +.1 Nm and h-value +.5 Nms. The experience from this test series shows that slump flow of 65 mm or more together with a T5 value of 4 seconds may be target values for good SCC. However, the absence of accuracy in the T5 measurements can be a problem. Target values for the BML viscometer for a good SCC may be g = -,1 and the h-value may be at least 12. The upper limit for the viscosity should be further investigated concerning the risk to encase air in the concrete Tests done at LCPC (see annex 6) Two programs of test were made at LCPC within this task. The first program mainly focused on the effect of the gravel to sand ratio on slump flow and rheological behavior in infinite and congested conditions. A device was specially developed to be added to the BTRHEOM to be able to account for the confinement during rheological test (see figure 7) 8

9 Page 9(2) upper blade supplementary upper blade rotating part fixed bowl sheared zone lower blade rheometer axis Fig 7- Principle of BTRHEOM in classical and confined conditions Ten recipes were made with varying gravel to sand ratio, the other components proportions being constant. The aggregate was a semi crushed silico-calcareous from Seine river. The following tests were done on each batch: slump or slump flow; air measurement on the sample used for slump; rheological test with BTRHEOM with and without confinement. The objectives of the second program was to study the rheology of very fluid concrete in infinite conditions and to find a correlation with the slump flow and the T5 with the rheological properties. Complementary objectives were to find a relation between the aggregate segregation and the mix design and to determine the relationship between the mix design and blocking in the L box. The aggregate was a crushed limestone from Boulonnais, the cement was CPA CEM I 52.5 Gaurain, the superplasticizer was Sikament 1 and limestone filler was Piketty A. The main varying parameters were the following: maximum size of aggregate; paste volume (or aggregate volume); paste nature (water, superplasticizer and cement content) The following tests were done: slump flow: the final diameter, the T5 and the width of the halo of mortar around the disc of concrete at the end of the test; rheological test with BTRHEOM with and without confinement. segregation tests the ball test: this test was specially developed for the project. It consists in measuring the sinking of a calibrated ball into a concrete of fresh concrete test on hardened concrete: a concrete cylinder Ø16*32 cm is cast and splitted after hardening to measure the mean penetrating depth of the two nearest from surface aggregates (with a diameter higher than 8mm). 9

10 Page 1(2) blocking tests with Lbox with different clear spaces between reinforcement. The main conclusions of these works are the following. Two models have been proposed to relate the rheological parameters to the slump flow parameters: ( Sl) τ = 88 Mg 1174 (mean error 95 Pa) (1) where Sl is the slump flow in mm, g the gravity acceleration and M the density in kg/m 3. and: Mg µ = ( Sl t ) 5 (mean error 35 Pa.s) (2) where t 5 is the spreading time in s. The following figure show the accordance between the models and the measurements. 1 4 Theoretical yield stress (Pa) Prog Theoretical viscosity (Pa s) Prog n Experimental yield stress (Pa) Experimental viscosity (Pa s) Fig. 1: Prediction of rheological parameters with equ. 1 and 2. The experience from this test series shows that for a good SCC target values of rheological parameters measured by the BTRHEOM rheometer may be a shear yield stress τ less than 4 Pa and a plastic viscosity µ' less than 2 Pa s. It is more difficult to define a minimum limit for the viscosity (a too low viscosity may lead to segregation of gravel). We have been able to characterize the flow behavior of the concrete in confined conditions with the BTRHEOM. The figure 8 shows the results obtained for concretes with the same paste volume and nature but with different gravel to sand ratios. It can be seen on this figure that the rheological parameters increase when the confinement increases. This evolution depends on the gravel to sand ratio. Although these rheological tests were useful to understand the effect of confinement in a more fundamental point of view (validation of mathematical packing model presented in task 5 report), they are burdensome to do. So L-box test seems to be more adapted to study the effect of confinement on the blocking risk. 1

11 Page 11(2) Shear yield stress (Pa) G/S=,75 G/S=1 G/S=1,3 G/S=1,5 Plastic viscosity (Pa s) G/S=,75 G/S=1 G/S=1,3 G/S=1, Inter-blades distance (cm) Inter-blades distance (cm) Fig. 8 a) and b) - Evolution of the rheological properties with the gravel to sand ratio and the distance between the blades on the BTRHEOM. 4. CONCLUSIONS Within this task, we have shown that the rheology of paste or grout could be a useful tool to select a set of cement, mineral addition and superplasticizer to be included in SCC concrete. With rheological measurements, it is possible to separate the effect of the components on the shear yield stress and the plastic viscosity. The aim, today, is to obtain a combination with a low shear yield stress and a sufficient viscosity which allows to roughly compare the components. But the acceptable limits are not well defined simply because the question remains how to relate these properties to the concrete behavior at fresh state. More research is needed on this subject. A lot of rheological tests have been done with the two rheometers available within the consortium: namely the BML viscometer and the BTRHEOM rheometers. These data will be used to validate the mix design models developed within task 5. Relationships have been established between the final slump flow and the shear yield stress (or the g-value) on one hand and the slumping time T5 and the plastic viscosity (or the h-value) on the other hand. With these relationships, it is possible to roughly estimate the rheological parameters of concrete from the slump flow test. The slump flow test is simpler to do but of course it describes less precisely the flow behavior than concrete rheometers. Guidelines for the target values of rheological parameters for "good" SCC have been proposed for BML viscometer and BTRHEOM rheometer. We have been able to characterize the influence of the confinement on the rheological behavior of the concrete thanks a new device added on the BTRHEOM rheometer. Although these rheological tests were useful to understand the effect of confinement in a more fundamental point of view (validation of mathematical packing model presented in task 5 report), they are 11

12 Page 12(2) burdensome to do. So L box test seems to be more adapted to study the effect of confinement on the blocking risk. 12

13 Page 13(2) 5. ANNEX 1 BMLWO3 A PRESENTATION OF THE BML-VISCOMETER During the years, many attempts have been made to study the rheological properties of concrete. These are important in defining the workability and fluidity of concrete when certain requirements are laid down. The rheological properties of concrete are, however, not easy to study. Empirical methods such as slump do not provide the correct parameters necessary to describe the rheological properties of fresh concrete. Techniques for measuring the rheological properties of concrete, often lack any theoretical basis, they may be too operator dependent and even sample separation may occur. The slump provides one parameter necessary to describe the rheological properties, but it is not capable of, for example, describing the relationship between shear rate and force in a concrete mix or giving rheological parameters as the initial flow resistance, the viscosity or quantifying the thixotropic effects. The need for accurate measurement of rheological properties of fresh concrete, have increased as new materials for mix design have been introduced (plasticizers, silica fume), and the requirements of fresh concrete have become more specific. A project was initiated at the Department of Building Material at the Norwegian Institute of Technology in the early eighties. The aim was to develop an instrument with a solid theoretical basis, which could measure the rheological parameters in concrete more easily and provide accurate and reliable results. 2 Description of the BML-Viscometer The BML-Viscometer type WO-3, which is the latest model in the BML-Viscometer family, is a constant rate coaxial cylindrical viscometer working according to the principle of a Couette viscometer [1]. It consists of a measuring unit and a computer that controls the instrument (Figure B-1). Figure B-1 The BML-Viscometer. 13

14 Page 14(2) Figure B-2 shows a cross section of the inner and outer cylinders in contact with the sample. The radius of the inner cylinder is 1 cm, the outer 2 cm and the height of the cylinders are 2 cm. Figure B-3 shows the outer and inner cylinder from above with the ribs to prevent slippage and to have the interface concrete-concrete in the shearing zone. The software that controls the BML-Viscometer is based on MS-Windows, with possibilities to define the measuring procedures and also to study measured rheological variables. Outer rotating cylinder Sample Rigid cone to avoid end effects Outer cylinder with ribs Inner cylinder with torque measuring Sample with cell possible plug indicated Rotating plate for outer cylinder Inner cylinder with ribs Figure B-2. Cross section of the viscometer cylinders. Figure b-3. The outer and inner cylinder from above. There exist several possibilities for graphical presentations and modelling using rheological models or simply raw data as measured torque and the speed of the outer cylinder. Transferring data to other software such as Excel is also possible, and in a new version of the software to come, it will also be possible to cut and paste graphics, define measuring procedures with both increasing and decreasing shear rate on the same sample besides some other improved features. The construction ensures the minimum of end effects affecting the measured values. It is possible to have control with separation under measurement, since the applied force is constant all over the shearing zone. The speed range of the outer cylinder is.1-.9 r.p.s., and the torque applied is maximum 1 Nm, though the normal maximum torque is set to 66 Nm to obtain the highest accuracy [2]. These ranges are suitable for different concrete mixes when a test is to be undertaken. Normally concrete exhibits a torque in the range.5-25 Nm during measuring when speed is set between.1-.5 r.p.s.. It is even possible to undertake rheological tests on zero-slump concrete, since all parts of the viscometer are intentionally oversized, however accurate results from such concrete are not possible. Sometimes it seems to be possible to obtain reliable measurements with a slump above 2 mm, but often a slump of 4-5 mm is necessary depending on the mix. The main differences between the BML WO-3 and earlier versions, are: Windows software instead of MS-DOS with some new facilities included 14

15 Page 15(2) New hardware, cards placed directly in PC. Motors and torque cells that manages 1 Nm compared to 32 Nm New heavy duty hydraulic systems New operating facilities as jog mode (manual movements of outer cylinder for easier transportation and cleaning) Smooth running at very low shear rates A new software is to come in December 1997 that makes it possible even to start at low shear rates and increase it to get both up and down curves. 3 Calibration and accuracy during measurement The variation in calibration constants for speed and torque are determined over a wide range of different speeds and moments. The difference in values measured under calibration, are in percentage within two decimal places, well below the variation observed for concrete. The reproducibility of the instrument is therefore very good. The calibration is easily done with standard weights, however, calibration fluids (oils) can also be used. The precision in measuring also seems to be satisfactory. A test of 7 equal concrete mixes, showed a maximum variation of the measured torque of ±.2 Nm, which shows a satisfactory reproducibility as the variation between the concrete mixes is included. 4 Running the BML-Viscometer When testing, the preferred procedure (which influences the results for concrete, as well as for any particle systems) is set up using the computer. The outer cylinder is filled with approximately 12 liters of concrete and testing can begin. Normally it will take a minute to finish a test, dependent on the set-up. The outer cylinder with the concrete is easily transported between the mixer and the viscometer by a small hand operated electric truck. 5 Are the results reliable, and what parameters are adequate? One of the problems with viscometric measurements on concrete, is the concentrated and dense particle system. Figure B-4, tables B-1 and B-2 shows a division of suspensions with different particle concentration into regions and indicates the most adequate measuring techniques in these regions [3]. Concrete is in an area where viscometric tests could be acceptable, but also in an area where other techniques could be preferable. Suspensions with low to medium concentration may cause a flow profile in the sample, but concrete has a too high particle concentration for this to occur completely. 15

16 Page 16(2) Fluid ~35 % C v C =1 C v v maks 8-9 % saturation Powder I II III Saturated systems Not saturated systems Figure B-4. Systems of different particle concentration, C V = concentration. Table B-1. Characterisation of particle systems: Influence of concentration. Region I Region II Region III Suspensions with low to medium concentration. May be treated as pseudo homogeneous. Poor reproducibility in viscometric tests. The flow behaviour is regulated by packing effects. Suspensions can show a granule-viscous behaviour. Not saturated, compressible 3-phase materials. Viscometers and rheometers cannot in most cases be used. Table B-2. Techniques for the different regions. Rheology Soil mechanics Region I & II III (II) Technique used Viscometers Rheometers (1) Shear box (2) Shear cell (3) Triaxial apparatus (4) IC-Tester [4] One of the problems arising then, is dilatation in the shearing zone, causing the values measured to be lower than they should be. This dilatation effect is greatly dependent on the shear rate, the higher shear rate causing increased separation [5]. Studies undertaken in the shearing zone of the BML-Viscometer, show that the dilatation effects are only pronounced, when the sample is sheared for the first time. The paste and liquid are then sucked into the shearing zone, but during subsequent shearing this does not occur as the zone has already 16

17 Page 17(2) separated [6]. The dilatation effects in concrete, and the permeability of the fresh concrete, have also been studied with techniques used in soil mechanics (triaxial tests) [6]. The nature of concrete also makes it impossible to obtain shear or velocity profiles, in opposite to many other materials, such as oils or suspensions at lower solid concentrations [7]. The viscometer will with concrete behave like an advanced shear box, with the shearing zone just outside the inner cylinder. The remainder of the concrete, between the inner and outer cylinder, will act as a plug. For the Bingham behavior concrete exhibits, only two parameters are necessary to describe the relationship between the shear speed and the measured torque. The two parameters have been given the name g [Nm] (initial flow resistance) and h [Nms] (a plastic viscous parameter), as for the two-point tester [4]. The g- and h-parameters are illustrated in figure B-5. There exists a non-linear relationship between the slump and g-value, but not between the h-value and the slump or between the g- and h-values, as expected, as the latter two describes two different properties of the concrete. This is shown in figure B-6 for some mixes, both with and without admixture (a superplasticizer). The slump, therefore does not indicate anything about the viscous properties of concrete, or other important rheological properties as for example thixotropic effects. These properties are of special importance in both high performance concrete and self levelling concrete (vibration free concrete). Torque [Nm] g h Speed [1/s].Figure B-5. Relationship between measured torque and speed in concrete. 17

18 Page 18(2) g [Nm] h [Nms] 2 5, 2, 1 5, 1, 5, Closed=g/slump Open=h/slump, Slump [mm] Figure B-6. Relationship between the g- and h-values and slump. References 1. Wallevik, O.H. and Gjørv O.E. (199) Development of a coaxial cylinders viscometer for fresh concrete. Proceedings of the RILEM Colloquium on Properties of Fresh Concrete, H.J. Wierig, Ed., Chapman & Hall. 2. Wallevik, O. H. (1995). Calibration of the BML-Viscometer for EUROC Research AB with documentation (Preliminary), Reykjavik, (in Norwegian). 3. Fluid Rheology (1987). A course arranged by Skandinavisk Teknikförmedling International AB, Uppsala. 4. Tattersall, G.H. (1991) Workability and Quality Control of Concrete, E & FN Spon, London. 5. Cheng, D.C-H. and Richmond R.A. (1978) Some observations on the rheological behaviour of dense suspensions. Rheol Acta 17, pp , Dr. Dietrich Steinkopff Verlag, Darmstadt. 6. Mork, J.H. Effect of gypsum-hemihydrate ratio in cement on the rheological properties of fresh concrete. The Norwegian Institute of Technology-NTH, Dr.Ing. dissertation 1994:4, Trondheim, 286p, (in Norwegian). 7. Cheng, D.C-H. (1984) Further observations on the rheological behaviour of dense suspensions. Powder Technology 37, pp , Elsevier. 8. Wallevik, O.H. The rheology of the fresh concrete and applications for concrete with and without silica fume, The Norwegian Institute of Technology-NTH, Dr.Ing. dissertation 199:45, Trondheim, 185p, (in Norwegian). 18

19 Page 19(2) 6. ANNEX 2 BTRHEOM The BTRHEOM rheometer is a plane-plane rheometer for concrete with maximum size of aggregate up to 25 mm. The principle of this rheometer is the following: a 7-liter specimen of concrete in the shape of a hollow cylinder is sheared between its fixed base and its top section which is in rotation around a vertical axis (see fig. C-1). The torque is transmitted from the motor located in the bottom part of the apparatus to the sample contained in the upper tank thanks to two horizontal blades (see fig C-2.). Different rotating speeds may be applied to the top section of the sample thanks to a software and the relationship between this speed and the torque necessary to maintain it constant is computed. From this relationship, and the strain field shown in fig. C-1, the rheological behavior of the concrete can be deducted whatever it is. Thus if the concrete is assumed to be a Bingham model, i. e. : τ = τ + µ γ &, where &γis the strain rate (in 1/s), τ the shear stress (in Pa), the concrete behavior is entirely characterized by its shear yield stress τ (in Pa) and the plastic viscosity µ' (in Pa s) and τ' and µ' can be measured with the BTRHEOM. The distance between the blades is 1 cm with allows to avoid the main wall effect in the apparatus. Nevertheless, for self compacting concrete, we are interested in measuring the rheology of the concrete in confined conditions. So an additional blade fixed on the vertical axis can be added between the two fixed blades. This blade is equipped with a grid to block the free dilatancy of the granular skeleton and the distance between this grid and the bottom one can be adjusted to be representative of the real confinement of the structure in which the concrete will be poured. During the week in Slite the gap was adjusted to 5 cm. Z Ω R2 h R 1 ΩR 2 θ r Y X Figure C-1: Principle of the BTRHEOM 19

20 Page 2(2) Figure C- 2: The BTRHEOM rheometer 2