1. By Narain Hariharan Aishwarya Baranikumar
MEASURING PERMEABILITY OF CONCRETE - THE CHALLENGES AND SOLUTIONS IN THE RESEARCH EXPERIENCE By
Narain Hariharan
Aishwarya Baranikumar

2. Outline of the presentation
Research objective
Purpose of the Paper
Importance of Permeability in Concrete
Experiment procedure
Challenges in Various Stages of Research
Results and Discussion
Conclusion

3. Research Objective
Measure the permeability of Cement paste (w/c=0.45 and 7 days after mixing, using the Hollow Cylinder Dynamic Pressurization (HDP) test.
Compare and test the results of the 2 cases for statistical significance.
Establish the importance and impact of w/c ratio on permeability.

4. Purpose of the Paper
To discuss the results obtained in the research study.
To elaborate on the various challenges faced during the experimental process.
Discuss the solutions and measures adopted to tackle the challenges.
Bring to light the importance of precision and accuracy in performing laboratory tests.

5. Importance of Permeability in Concrete
Diffusion, osmosis, adsorption, permeability- all affect durability of concrete.
Permeability- seepage of water through the pores in concrete.
Results in loss of durability.
Main reason why concrete is taken out of service.
Early age permeability of concrete- very low but critical.
Accurate measurements required.

6. Experiment procedure Mold details Hollow cylindrical mold
Diameter- 2 in.
Height - 8 in.
Batch 1: w/c=0.40
Batch 2: w/c=0.45
0.20 in. diameter
plastic rods in center
to make hollow
samples.

7. Batch 1: w/c = 0.4 , Type III OPC Batch 2: w/c = 0.5 , Type III OPC
Sample details
Batch 1: w/c = 0.4 , Type III OPC
Batch 2: w/c = 0.5 , Type III OPC
Mixed in accordance with ASTM C
Samples demolded hrs. after mixing.
Immediately placed in room temperature till testing.
Tested for Permeability using HDP after 7 days.
Pressure – psi
Test time – 24 hrs.
Gives relaxation time Ʈ from strain-time history

8. HDP Test Apparatus
Reference: Correlation of Radial Flow-Through and Hollow Cylinder
Dynamic Pressurization Test for Measuring Permeability
Christopher A. Jones and Zachary C. Grasley

9. Challenges in Various Stages of Research
Mold Preparation
Combined two 2”x4.2” standard molds
Cut open the closed end of one mold and combined with another mold using duct tape to get 2”x8” mold
Hollow mold??
Reflector sticks drilled through center of base
To hold the stick in place– Aluminum plate same dimensions as base used at top
To remove stick – cut longer than 8”

11. Sample Demolding Process
Removing the reflector stick – critical; after initial set and before final set ( 3-4 hrs.)
Blowing compressed air- ineffective for hollow geometry
Removing the duct tape and separating the two molds by twisting/shearing – breaks the sample, weak zone at interface
Hence, the mold was cut vertically after removing the tape and the two molds were bent out without damaging the sample

12. HDP Test Setup Sample glued to steel caps using epoxy
Height adjustments made by threading and bending the steel rod having LVDT setup
LVDT extremely sensitive – challenge to position the core and coil in line
Very important for accurate measurements.

13. HDP Testing Risks associated with High Pressure
Pressure range in HDP - High (1000 psi)
Pressure Removal dangerous
Can result in leaks and spills
Damage the specimen
Precautions – Step-wise depressurization; minimum 3 levels
Securely check and fasten all connections

14. Other Scope of Errors Presence of entrapped air
Insufficient saturation at time of testing
Variation in time of performing test.(+/- 2-3hrs.)
Minor variation in specimen height as a result of cutting open the existing 2”x4” mold
LVDT- zero error

15. Results and Discussion
Permeability is then calculated using the following relation:
where,
k- permeability in units of length square
Ro, Ri are respectively the outer and inner radii of the sample
Kp , M and Ƞl are material properties of the sample
Ʈ is the relaxation time (obtained from HDP test)

16. Cement paste (w/c=0.40 @ 7 days)
Note: x-axis represents time and y-axis represents micro-strain.

17. w/c ratio impacts permeability of early age cement paste.
Summary of results
Statistically significant increase in permeability with higher w/c ratio.
w/c ratio impacts permeability of early age cement paste.
Batch
Relaxation time (s)
Permeability k (nm2)
1 (w/c = 0.4)
20000
0.005
2 (w/c = 0.5)
17000
0.015

18. Conclusion
Discussed the various challenges encountered during the research study.
Highlighted the importance of perfection and precision in execution of research tasks.
Understood the significance of research in education.

19. REFERENCES
Jones, C.A. and Grasley, Z.C. (2009) Correlation of Radial Flow-Through and Hollow Cylinder Dynamic Pressurization Test for measuring Permeability.
Grasley, Z.C. (2006) Measuring and modeling the time-dependent response of cementitious materials to internal stresses.
Vichit-Vadakan, Scherer, G.W. and Grutzeek, M. (2002) Measuring permeability of rigid materials by a beam-bending method.
Jones, C.A. and Grasley, Z.C. (2010) Correlation of hollow and solid cylinder dynamic pressurization Test for measuring permeability.

20. Comments/Questions?? Thank you