Structural Rehabilitation of RC Column with Micro Concrete Jacketing

1. STRUCTURAL REHABILITATION OF RC COLUMN
WITH MICRO-CONCRETE JACKETING
Presented By :
Md. Alauddin Khan
Student ID: 1104134
Md. Tariqul Islam
Student ID: 1104160
Supervised By:
Dr. Ishtiaque Ahmed

2. • Introduction
• Test Design
• Test Result
• Data Analysis
• Conclusions and Recommendations
Outline of The Presentation

3. Introduction

4. Objectives
•To Identify the nominal axial capacity of
existing weak concrete columns.
•To Evaluate various micro concrete jacketing
methods as a retrofit measure for improving
the nominal load carrying capacity of
rectangular columns.
•To evaluate the effectiveness of surface
roughing and use of Nitobond at the interface
of existing concrete and micro concrete jacket.

5. Objectives
•To evaluate the effectiveness of using shear key
at the faces of existing deficient column to
improve load carrying capacity of column.
•To evaluate the effectiveness of using shear
key, Nitobond and surface roughening all
together.
•To compare the improved axial load capacity of
micro-concrete jacketed column with theoretical
value.

6. Scope of the study
• The experiment was conducted with a half
scale column. Cross section of the core
column was taken as 6″x6″ with the cross
section of the jacketed section 10″x10″.
• The study considered only for the pure axial
capacity of the column and the flexure
capacity was not considered.

7. Scope of the study
• This study with only micro-concrete as a
jacketing material. The behavior of the other
jacketing material was not studied.
• The spacing of shear key is calculated
according to the ACI (318-14) code 22.9

8. Test Design

9. Mix Design of Concrete
For Core Concrete:
•W/C ratio: 0.68
•Cement= 243 kg
• Fine Aggregate(SSD)= 875 kg
•Course Aggregate(SSD)= 812kg
•Water = 243 kg
•Design Slump=180 mm
For Jacketing:
•W/C ratio: 0.26
•Cement=765 kg
•Fine Aggregate (SSD) =501.45 kg
•Course Aggregate (SSD) =812 kg
•Water = 198.9 kg
•Admixture = 7.65 kg
•Designed Slump=200 mm

10. Column name
Column
Size
Number of longitudinal bars
Core column-1
6”X6” 4 #5 corner bar
Core column-2 6”x6” 4 #5 corner bar
Retrofitted
Column-1
10”x10”
4 #5 corner bar
With shear key , Nitobond and Surface Roughening
Retrofitted
Column-2
10”x10”
4 #5 corner bar
With shear key , Nitobond and Surface Roughening
Retrofitted
Column-3
10”x10”
4 #5 corner bar
With shear key and Surface Roughening
Retrofitted
Column-4
10”x10”
4 #5 corner bar
With shear key and Surface Roughening
Retrofitted
Column-5
10”x10”
4 #5 corner bar
With Nitobond and Surface Roughening
Retrofitted
Column-6
10”x10”
4 #5 corner bar
With Nitobond and Surface Roughening
Design of Columns

11. Design of Columns for Jacketing
Design of Shear Key:
•Size of Bar : 12 mm
•Length of Shear key : 4” (3”
into the core 1” outside)
•Extended portion of Shear key
is bend at 60 Degree
Use of Nitobond:
• Nitobond is placed all over the 5
ft. column by manual brushing.

12. Fig: Shear key
Jacketing Procedure
Fig: Application of Nitobond
by brushing

13. Test Result

14. Fig: Failure of Core Column-1 Fig: Failure of Core Column-2
Failure of Columns

15. Failure of Columns
Fig: Failure of
Column-1
Fig: Failure of Column-2

16. Failure of Columns
Fig: Failure of
Column-3
Fig: Failure of Column-4

17. Failure of Columns
Fig: Failure of
Column-5
Fig: Failure of Column-6

18. Summary of Test Results
Designation Ultimate Load
(KN)
Ultimate Load
(Kip)
1st Cracking
Load
(KN)
1st Cracking
Load
(Kip)
Width of First
Crack
(mm)
Core Column-1 809.59 182.02 136 30.58 0.4
Core Column-2 655.66 147.41 301 67.68 0.6
Column-1 1647.22 370.33 1280 287.77 0.4
Column-2 1754.26 394.4 1600 359.72 0.6
Column-3 1735.98 390.29 1631 366.69 0.4
Column-4 1725.6 387.95 1557 350.05 0.3
Column-5 1691.82 380.36 1675 376.58 1
Column-6 1725.17 387.86 1295 291.15 1

19. Data Analysis

20. Comparison Among Columns
0
200
400
600
800
1000
1200
1400
1600
1800
2000
Load(KN)
Axial Capacity (KN)
Core Column-1
Core Column-2
Column-1
Column-2
Column-3
Column-4
Column-5
Column-6
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0 20 40 60
Load(KN)
Deflection (mm)
Load Vs Deflection
Column-1
Column-2
Column-3
Column-4
Column-5
Column-6
Core Column-1
Core Column-2

21. Theoretical Capacity

22. Designation Pn (core) Pn (jkt) α Pn(ret) Actual Strength Percentage of
(KN) (KN) (KN) (KN)
Theoretical
Strength
Column-1 645.09 2723 0.4 1734.3 1647.22 94.98
Column-2 645.09 2723 0.4 1734.3 1754.26 101.16
Column-3 645.09 2723 0.4 1734.3 1735.98 100.1
Column-4 645.09 2723 0.4 1734.3 1725.6 99.5
Column-5 645.09 2723 0.4 1734.3 1691.82 97.56
Column-6 645.09 2723 0.4 1734.3 1725.17 99.48
Core Column-1 645.09 0 0 645.09 809.59 125.51
Core Column-2 645.09 0 0 645.09 655.66 101.64
Theoretical Capacity

23. Sources of Variation In Test Result
• Compaction difficulties
• Material dissimilarities
• Delaying casting
• Expansion of jacketed concrete
• Improper sealing of shuttering

24. Conclusion

25. • Capacity of columns increases more than100%
than that of core column
• When the interaction between old and new
concrete is assumed 40% the theoretical
capacity approaches the test capacity
• Shear key performs better than Nitobond.
• RC jacketed columns gives adequate time
before failure
Outcomes of The Study

26. Limitations
• Only behavior of rectangular columns are
studied.
• Only analysis is done for pure axial load (No
eccentricity)
• Load is directly applied to retrofitted cross
section.
• No pre loading of column is considered.

27. Recommendations
• Behavior of circular columns can be studied.
• RC jacketing with pre loading of column can also be studied in future.
• Behavior of eccentric loading can also be studied.
• Different loading condition can be considered.
• Maximum Capacity of the compression testing machine is 2000KN.For
that reason the effect of high strength concrete cannot be tested in the
lab.
• The effect of welded tie bars in shear transfer mechanism can further be
investigated.
• This test can also be performed for seismic detailing