1. X. Wang, K. Wang, J. Han, P. Taylor
Image Analysis Applications on Assessing Static Stability and Flowability of Self-Consolidating Concrete by
X. Wang, K. Wang, J. Han, P. Taylor
June, 2014

2. Objective
Use digital image process and analysis (DIP) to evaluate the static stability of SCC
Develop statistical models for predicting flowability from hardened SCC
Investigate/calibrate the relationship between parameters derived from DIP method and existing theoretical frame, i.e., excessive paste theory and paste-to-voids volume concept

3. Background Excess paste/mortar theory
The “lubricating” layer of paste around aggregates needs to be
Thin enough: prevent coarse aggregate from sinking down and segregating
Thick enough: achieve good workability
Two main parameters:
Dss: average spacing between aggregate particle surfaces
Dav: average aggregate diameter
Assumptions:
Aggregate particles are spherical
Particles are packed in a cubic lattice

4. Background Vpaste/Vvoids concept
Provide a quantitative means to consider the interaction between paste and aggregate system
Take into account differences between aggregate systems
Coat the aggregate particles
Fill the voids between the combined aggregate system
Disperse the aggregate particles to provide workability

5. Background Digital image process (DIP) Features: Steps:
Rapid, evaluate large number at one time, free from subjectivity, and easy to characterize aggregate features
Steps:
Image acquisition, pre-processing, segmentation, representation and description, and recognition and interpretation
Applications in concrete research:
Algorithm development to provide optimum threshold and aggregate size distribution
Crack length and fracture properties
Fractured aggregate area ratio
Aggregate shape and strength
Aggregate shape parameters and concrete rheology
Air-void system in hardened concrete

6. Materials
Coarse aggregate types: crushed limestone (LS) and river gravel (G);
Coarse aggregate sizes: 19 mm (a), 12.5 mm (b), and 9.5 mm (c);
SCMs: Class C and F fly ashes (C and F) with 25% replacement level, slag cement (S) 30% replacement level;
Limestone dust (LD) amounts: 0 and 15% cement replacement.
w/cm: 0.36 to 0.42
Fine-to-total aggregate volume: 0.45 for 19 mm NMSA; 0.47 for 12.5 mm; 0.50 for 9.5 mm

7. Materials and Mix Proportioning
40 SCC mixtures
Low slump flow range between 550 and 650 mm or high flow range between 650 and 750 mm
Visual stability index, (VSI)≤1
J-ring ≤ 75 mm

8. Research Plan

9. DIP Method

10. DIP Method
Aggregate system used in excessive paste theory (left) and defined in this research

11. DIP Method a b c d

12. Results

13. Results
Static stability

14. Results
Probability density vs. HVSI

15. Results Rheological models Response surface models
SF = × MTI – 1.56 × τ – × (MTI – 1.89) × (ŋ – 0.99) – × (ŋ –0.99) × (τ – 33.41)2
=> SF= τ×(τ –106) – 94ŋ×(ŋ – 4.27) +149×(1 – 0.77ŋ) × MTI
For a given paste, SF∝MTI
Critical viscosity of 1.3 Pa-s

16. Results

17. Results
Relationship between results from DIP method and existing theoretical frames

18. Results
Average inter-particle spacing from DIP method vs. Dss calculated from excessive paste theory

19. Conclusions Proposed DIP method and algorithm works
Potentially overcomes the limitations of existing theory frames
Quantitatively assess stability and workability
Probability density of 60% from histogram analysis as a threshold for indicating a uniformly distributed SCC mixtures
Viscosity of 1.30 Pa-s tends to be a critical point

20. Questions?

21. Appendix
Fresh properties and DIP results of limestone SCC mixtures

22. Appendix
Fresh properties and DIP results of gravel SCC mixtures