Das Betonrheometer BT2 zur Bestimmung der rheologischen Eigenschaften selbstverdichtender Betone - Möglichkeiten und Entwicklungspotential

Transcription

1 Das Betonrheometer BT2 zur Bestimmung der rheologischen Eigenschaften selbstverdichtender Betone - Möglichkeiten und Entwicklungspotential The concrete rheometer BT2 for assessment of the rheological properties of Self-Compacting Concrete scope and potential for development 21. Kolloquium Rheologische Messungen an mineralischen Baustoffen, HS.R

2 Contents Introduction The Concrete Rheometer BT2 Further development of the BT2 Measurements with the new BT2 Test results Summary 2

3 Introduction Control of the flowability of SCC Visual control; laboratory technician 3

4 Introduction Control of the flowability of SCC Single-Point Tests (V-Funnel Test, Slump Flow, etc.) Advantages: simple, fast, suitable for construction site Disadvantages: empirical, no detailed information about rheological properties 4

5 Introduction Control of the flowability of SCC Measuring required mixing energy 5

6 Introduction Control of the flowability of SCC Recording energy consumption of concrete mixer Torque of mixing tool [Nmm] Recording of the torque of the mixing tool during a whole mixing period Mixing time [sec] Torque of mixing tool [Nmm] Utilisation of the flow curve Bingham y = 0,1257x + 8,1028 R² = 0, Speed mixing tool [rpm] 6

7 Introduction Control of the flowability of SCC Multiple-Point Tests BML Viscometer Tattersall Two-Point Rheometer BTRHEOM Eric P. Koehler, W.R. Grace & Co.: Test Methods for Workability and Rheology of Fresh Concrete, ACI Fall Convention November

8 Introduction Control of the flowability of SCC Multiple-Point Tests Advantages: Disadvantages: Rheological properties permanent shearing of the specimen slipping / segregation tricky handling setting and stiffening of the concrete is affected 8

9 Introduction Control of the flowability of SCC Multiple-Point Tests ICAR Rheometer Eric P. Koehler, W.R. Grace & Co.: Test Methods for Workability and Rheology of Fresh Concrete, ACI Fall Convention November

10 Introduction Control of the flowability of SCC Multiple-Point Tests Advantages: Disadvantages: Rheological properties permanent shearing of the specimen slipping / segregation tricky handling setting and stiffening of the concrete is affected 10

11 The Concrete Rheometer BT2 crank-handle original probes 20 l container 11

12 The Concrete Rheometer BT2 How it works Two probes with different radius rotate around a centric axis Measurement of the flow resistance at different load levels (different track speed) Regression line flow curve with relative Yield Stress and relative Plastic Viscosity 12

13 The Concrete Rheometer BT2 Advantages Portable Short measurement No problems with cylinder geometry No slipping / segregation Measurement in fresh, unsheared concrete (one revolution) 13

14 The Concrete Rheometer BT2 original BT2 First measurements on SCC Results: data were not exact enough 14

15 The Concrete Rheometer BT BT2 - Flow curve Example original probes (d = 12 mm) BT-2 Linear (BT-2 ) 1500 Torque [Nmm] y = 6955,9x + 526,28 R² = 0, ,00 0,02 0,04 0,06 0,08 0,10 0,12 Speed [m/s] 15

16 Further development of the BT2 original BT2 First measurements on SCC Results: data were not exact enough new probes More reliable data But still too inexact for very flowable SCC Flow curve indistinct Blocking by settled aggregates 16

17 Further development of the BT2 BT2 - Flow curve Example new probes (d = 28 mm) y = 6807,2x + 120,28 R² = 0, Torque [Nmm] ,00 0,02 0,04 0,06 0,08 0,10 0,12 Speed [m/s] 17

18 Further development of the BT2 Automatic drive new probes 40 l container 18

19 Further development of the BT2 Deeper specimen container and automatic drive Flow curve with yield stress, plastic viskosity and structural break down Stress growth test with static and dynamic yield stress No blocking Exact data at low shear speed Software Update 19

20 Measurements with new BT2 Measuring process: 20

21 Measurements with new BT2 Measurement profiles 21

22 Measurements with new BT2 Measurement profiles Profile a Setting: Result: Speed controlled mode with increasing and decreasing velocity flow curve with - rel. yield stress - rel. viscosity 22

23 Measurements with new BT2 Measurement profiles Profile a 23

24 Measurements with new BT2 Measurement profiles Profile b Setting: continual low speed Result: Torque vs. time; Stress Growth Test - Static Yield Stress - Dynamic Yield Stress 24

25 Measurements with new BT2 Measurement data Data are recorded by both probes Both probes are evaluated separately Good correlation between the probes Utilisation with Bingham-Model Only one probe necessary for getting results Second Probe used for control 25

26 Test Results 1. Test series: Optimization of the test profiles and settings 2. Test series Variation in water content (SF 550 mm mm) Target: Impact of different water content on the rheological properties Result: BT2 delivers reliable information regarding the water content 26

27 Test Results Profile a 300 Flow curve increasing velocity; t = w/p - ratio 0,88 Torque [Nmm] ,88 0,8 0,8 0,76 0,76 0,72 0,72 0 0,00 0,01 0,02 0,03 0,04 Speed [m/s] 27

28 Test Results Profile a 300 Flow curve decreasing velocity; t = 0 Torque [Nmm] y = 5108,2x + 85,217 R² = 0,9099 y = 5626,8x + 52,887 R² = 0,8858 y = 3434,8x + 18,984 R² = 0,9625 y = 3086,7x + 26,404 R² = 0,9506 y = 1834,2x + 1, R² = 0,9618 y = 1616,5x + 2,6276 R² = 0, y = 917,11x - 1,4854 R² = 0,9364 y = 489,92x - 4, R² = 0,9025 0,00 0,01 0,02 0,03 0,04 Speed [m/s] w/p -ratio 0,88 0,88 0,8 0,8 0,76 0,76 0,72 0,72 28

29 Test Results Profile a 350 Flow curve increasing velocity; no additional mixing 300 Torque [Nmm] Time t=0 t=3 t= ,00 0,01 0,02 0,03 0,04 0,05 Speed [m/s] 29

30 Test Results Profile a 900 Flow curve increasing velocity; t = 5 min Torque [Nmm] ,70 without additional mixing 0,70 with 30sec. mixing ,00 0,01 0,02 0,03 0,04 Speed [m/s] 30

31 Test Results Profile b 600 Stress Growth Test half turn; inner probe; t = 0; Cement A 500 Torque [Nmm] w/p=0,70 w/p=0,76 w/p=0,80 w/p=0, Time 31

32 Test Results Profile b Stress Growth Test half turn; outer probe; t = 0; Cement A Torque [Nmm] w/p=0,70 w/p=0,76 w/p=0,80 w/p=0, Time 32

33 Test Results Profile b 600 Stress Growth Test half turn; inner probe; t = 0; Cement B 500 Torque [Nmm] w/p=0,80 w/p=0,84 w/p=0,92 w/p=0, Time 33

34 Test Results Profile b (Mean of five measurements+ standard deviation) 500 Yield Stress with different water content; t = 0 min Torque [Nmm] ,68 0,73 0,78 0,83 0,88 w/p-ratio Stat. Static Fließgrenze Yield Stress Dyn. Dynamic Fließgrenze Yield Stress 34

35 Test Results Profile b 700 Stress Growth Test half turn; inner probe; w/p = 0, Torque [Nmm] t=0 t=5 t= Time 35

36 Test Results 20 l container vs und 40 l container 250 Stress Growth Test half turn; inner probe; different containers 200 Torque [Nmm] l w/p = 0,88 40l w/p = 0,94 20l w/p=0,88 20l w/p=0, Time 36

37 Summary More exact results with modified BT2 No blocking of aggregates Flow curves with structural build up and break down relative Yield Stress and Plastic Viscosity Stress Growth Test (Torque vs. Time) with dynamic Yield Stress static Yield Stress Control of water content and flowability possible Further tests necessary 37

38 KONSTROLL Thank you! Bild neuer BT2 Folgt noch! Noch auf Handy 38