its about bonding between old and new concrete.

1. Final Year Project Presentation
TITLE OF THE PROJECT
EVALVATING DIFFERENT FACTORS AND
REMEDIES FOR BONDING BETWEEN OLD
AND NEW CONCRETE LAYERS
DEPARTMENT OF CIVIL ENGINEERING
UNIVERSITY OF ENGINEERING AND TECHNOLOGY, PESHAWAR.

2. Presented by:
SAJJAD AHMAD
Reg# 11PWCIV3499
NOOR ULLAH
Reg# 11PWCIV3521
MUHAMMAD BILAL
Reg# 11PWCIV3554
Supervised by:
PROF. DR. BASHIR ALAM

3. INTRODUCTION:
 Concrete(RCC) Structures are built in parts.
Foundation……Columns…….Beams……..Slabs…..
 Concrete pavement(PCC)……. Overlay new concrete over
old concrete.
 It leads to the formation of interfaces b/w concrete
layers cast at different ages.
 Results in non-monolithic behavior of reinforced
concrete composite members.
 It deteriorates the structural members and adversely
effect the structural members strength parameters.

4. OVERVIEW:
 Factors leading to non monolithic behavior.
 Differential stiffness.
 Differential shrinkage.
 Differential Thermal Coefficient.
 Factors effecting Interfacial Bond strength.
 Moisture condition.
 Water/cement ratio.
 Surface Roughness.
 Age difference factor.
 Supplementary Cementatious Materials(SCM).

5. OVERVIEW:
 REMEDIES TO STRENGTHEN THE BOND B/W OLD AND NEW
CONCRETE LAYERS.
 Increase Substrate Surface Roughness
 Use of Bonding Agents
LATEX
EPOXY
 Nailing
TESTS TO BE CONDUCTED TO EVALVATE THE BOND STRENGTH.
 Bending test….(Tension + Compression)
 Direct Shear test……….(Shear)
 Direct Tension test….(Tension)
 Slant Shear test………(Compression + Shear)

6. OBJECTIVES:
 Concrete members combine precast with cast-in-place parts.
 The main theme of our project is to Evaluate
 Different approaches to ensure Monolithic behavior.
 Different approaches to ensure effective bonding.
 Suitability of different approaches to specified conditions.
 The influence of differential stiffness and differential
shrinkage at interface of concrete layers cast at different
ages.

7. WORK FLOW PATTERN:

8. FACTORS LEADING TO NON MONOLITHIC
BEHAVIOR:
 Chemical reactions(Hydration) in old precast concrete has
processed while in new overlay it has to process yet...leads
to different chemical analogy.
 Concrete casted at different ages…exhibit differential Young
modulus………..differential stiffness…..…..differential stress
distribution………even if same concrete mix.
 Differential thermal co-efficient……caused by differential
chemical analogy……………...leads to differential stress
distribution at interface.

9. FACTORS EFFECTING INTERFACIAL BOND
STRENGTH:
 Moisture condition.
Different opinions(findings) but small watery content at
interface boost good bonding while more content weakens.
 Water/cement ratio(w/c).
As w/c 1/strength (beyond certain limit).
What is effect of w/c ratio on bond strength???
 Surface Roughness.
Generally….Increased roughness…Increased friction…
….Increased strength. Different approaches to get surface
roughness.

10. SURFACE PREPERATION TECHNIQUES:
 Mechanical Removal:
Chipping hammer Wire brushing Scarification

11. SURFACE PREPERATION TECHNIQUES:
Particle Impact Removal:
Shot Blasting……When metal particles are used for blasting.
Sand Blasting…..When sand particles are used for blasting.
Fig# Sand Blasting.

12. REMEDIED TO STRENGTHEN THE INTERFACIAL BOND:
 Increase Surface Roughness:
Surface preparation (Previous slides).
 Application of Bonding Agents:
 EPOXY RESING.
Function……….Bonding and Adhesion.
 Three Grades of Epoxies….Type I …… type II ……Type III.
 We deals with Type II, for bonding freshly mixed
concrete to hardened concrete.
 For Repair of Joints and Cracks.

13. REMEDIED TO STRENGTHEN THE INTERFACIAL BOND:
 LATEX EMULSION:
 Always used in slurry form with Cementatious materials.
 Cement/Latex slurry increases Bond strength.
 Without Cement……………not effective.
 Different types………..select the most suitable for the
intended purpose.

14. REMEDIED TO STRENGTHEN THE INTERFACIAL BOND:
 NAILING (PCC).
 Nails are intruded in substrate……then overlaid.
 Overlay anchored in substrate………….increase shear strength.
 For Pavement and adding thickness to Roof slabs.

15. TESTS BE CONDUCTED TO ASSESS THE BOND STRENGTH:
 Bending test:
 Common test to assess the bond strength of concrete-to-concrete
And concrete-to-repair material interfaces.
 Depends on the localization and orientation of the interface
Plane. Only tension and compression are present at the interface.
Fig# Bending test.

16. TESTS BE CONDUCTED TO ASSESS THE BOND STRENGTH:
 Direct Shear test:
 Simplest bond test to assess the shear strength between two
materials(concrete).
Fig# Direct Shear test

17. TESTS BE CONDUCTED TO ASSESS THE BOND STRENGTH:
 Direct Tension Test:
The direct tension test, defined by standard ASTM C 1404
(2003), measures the tensile bond strength of the interface
between two materials, such as old-to-new concretes or
Concrete-to-repair material.
Fig# Direct tensile test

18. TESTS BE CONDUCTED TO ASSESS THE BOND STRENGTH:
 Slant Shear Test:
 The slant shear test is one of the most wide spread bond tests.
 The interface is subjected to a stress state of compression
combined with shear.
 Reliable and Consistent method, because it simulates a stress
state close to the actual use and failure mode of concrete.
Fig# Slant Shear Test.

19. REFERENCES:
 Pedro, Eduardo,(july2009) ACI material journal, Assessment of
shear strength between concrete layers vol(108), Coimbra.
 Zhifu (may,2011) Thesis on Interfacial Bond Strength between
old and new concrete, Beijing university of technology.

20. THANK YOU!!
QUESTIONS PLZ???