COURSE Testing techniques for structures inspection 29th and 30th May 2012
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MECHANICAL TECHNIQUES APPLIED IN CONCRETE
STRUCTURES
Arlindo Gonçalves
André Monteiro
(LNEC)
COURSE Testing techniques for structures inspection 29th and 30th May 2012
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ADDRESSED TECHNIQUES
• Rebound Hammer
• Pull‐Out
• Pull‐Off
DURATINET COURSE - Testing Techniques for Structures Inspection LNEC • Lisbon • Portugal • 29-30 May 2012
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COURSE Testing techniques for structures inspection 29th and 30th May 2012
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REBOUND HAMMER
Originally developed by the Swiss engineer Ernst Schmidt in the 1940’s
The test is covered by EN 12504‐2 andASTM C805
Measures the surface hardness of concrete
Main applications:
•Detection of zones with poor quality concrete
•Comparative testing against a concrete with known strength
•Estimation of in situ concrete strength
COURSE Testing techniques for structures inspection 29th and 30th May 2012
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Principle:
Test result: rebound number
REBOUND HAMMER
DURATINET COURSE - Testing Techniques for Structures Inspection LNEC • Lisbon • Portugal • 29-30 May 2012
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COURSE Testing techniques for structures inspection 29th and 30th May 2012
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REBOUND HAMMER
Steps:
COURSE Testing techniques for structures inspection 29th and 30th May 2012
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REBOUND HAMMER
Types of rebound hammer:
L(0.74 Nm)
P(0.88 Nm)
N(2.21 Nm)
M(29.43 Nm)
DURATINET COURSE - Testing Techniques for Structures Inspection LNEC • Lisbon • Portugal • 29-30 May 2012
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REBOUND HAMMER
New SilverSchmidt Hammer developed by Proceq
(does not need correction for the impact direction)
COURSE Testing techniques for structures inspection 29th and 30th May 2012
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REBOUND HAMMER
Correlation with concrete compressive strength:
Influence of the type of aggregate Influence of concrete moisture contentInfluence of carbonation
Strength level: L-low; M-medium and H-highCuring conditions: empty bullets – normal curing; filled bullets – accelerated carbonation
DURATINET COURSE - Testing Techniques for Structures Inspection LNEC • Lisbon • Portugal • 29-30 May 2012
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Pr EN 12504‐2 – What’s new?
• The results may be used for comparative testing
• A number may also be obtained in terms of velocity differential before and after the impact
• Acceptance rules for checking the rebound hammer before and after the readings
• Other anvils may be used if they provide similar readings (the mass of the reference anvil is 16 1kg)
• The hammer may be operated within the range 0oC to 50oC (before 10oC to 35oC)
COURSE Testing techniques for structures inspection 29th and 30th May 2012
Investing in our common future
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PULL‐OUT TEST
First developments by 1930 in the URSS
Major improvements published by Kierkegaard‐Hansen in 1975, naming it by Lok‐test
The test is covered by EN 12504‐3 andASTM C900
Main application:
•Assessment of concrete compressive strength
DURATINET COURSE - Testing Techniques for Structures Inspection LNEC • Lisbon • Portugal • 29-30 May 2012
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COURSE Testing techniques for structures inspection 29th and 30th May 2012
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PULL‐OUT TEST
Principle:
Test result: pull‐out force (kN)
A small metal disc, with a rod fixed centrally on one side is installed into concrete during casting, so that the rod protrudes from the surface of the concrete. The force required to pull the disc out of the concrete is measured.
COURSE Testing techniques for structures inspection 29th and 30th May 2012
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Steps:
PULL‐OUT TEST Remove the cast-in rod and connect the loading rod
DURATINET COURSE - Testing Techniques for Structures Inspection LNEC • Lisbon • Portugal • 29-30 May 2012
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COURSE Testing techniques for structures inspection 29th and 30th May 2012
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PULL‐OUT TEST
History of development (Kierkegaard‐Hansen):
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PULL‐OUT TEST
Performing pull‐out test on existing structures (Capo‐test):
DURATINET COURSE - Testing Techniques for Structures Inspection LNEC • Lisbon • Portugal • 29-30 May 2012
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PULL‐OUT TESTType of resistance measured:
Complex triaxial stress state changing during the test and along the failure surface
The ultimate state of failure is influenced by the shear strength of the matrix mortar that controls the displacement of the aggregates at the failure surface
COURSE Testing techniques for structures inspection 29th and 30th May 2012
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PULL‐OUT TEST
Correlation with concrete compressive strength:Obtained by several authors
(15 cm cubes)Kierkegaard-Hansen
recommendation:
Some studies have shown that for high strengths the linear relation may underestimate the compressive strength
DURATINET COURSE - Testing Techniques for Structures Inspection LNEC • Lisbon • Portugal • 29-30 May 2012
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COURSE Testing techniques for structures inspection 29th and 30th May 2012
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ESTIMATION OF IN‐SITU COMPRESSIVE STRENGTH
TEST Laboratory In‐situ
Reboundhammer
15 % 25 %
Pull‐out 6‐8 % 10‐20 %
COURSE Testing techniques for structures inspection 29th and 30th May 2012
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EN 13791 ‐ ASSESSMENT OF IN‐SITU COMPRESSIVE STRENGTH IN STRUCTURES AND PRE‐CAST CONCRETE COMPONENTS
Compressive strength estimation:
•Alternative 1: Direct correlation with cores (requires 18 cores)
•Alternative 2: Correlation based on a basic curve (requires 9 cores)
DURATINET COURSE - Testing Techniques for Structures Inspection LNEC • Lisbon • Portugal • 29-30 May 2012
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COURSE Testing techniques for structures inspection 29th and 30th May 2012
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EN 13791 ‐ ASSESSMENT OF IN‐SITU COMPRESSIVE STRENGTH IN STRUCTURES AND PRE‐CAST CONCRETE COMPONENTS
Alternative 2 (basic curves)Rebound hammer Pull-out test
COURSE Testing techniques for structures inspection 29th and 30th May 2012
Investing in our common future
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EN 13791 ‐ ASSESSMENT OF IN‐SITU COMPRESSIVE STRENGTH IN STRUCTURES AND PRE‐CAST CONCRETE COMPONENTS
Alternative 2 (basic curve)
DURATINET COURSE - Testing Techniques for Structures Inspection LNEC • Lisbon • Portugal • 29-30 May 2012
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COURSE Testing techniques for structures inspection 29th and 30th May 2012
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EN 13791 ‐ ASSESSMENT OF IN‐SITU COMPRESSIVE STRENGTH IN STRUCTURES AND PRE‐CAST CONCRETE COMPONENTS
CONSERVATIVE APPROACH ?!
COURSE Testing techniques for structures inspection 29th and 30th May 2012
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PULL‐OFF TEST
Originally developed in England
The test is standardized in EN 1542
Measures the bond strength between two materials
Main applications:
• Check bond strength of repair materials (coatings, paints, vanishes and repair mortars)
• Assessment of concrete or mortar tensile strength
DURATINET COURSE - Testing Techniques for Structures Inspection LNEC • Lisbon • Portugal • 29-30 May 2012
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COURSE Testing techniques for structures inspection 29th and 30th May 2012
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Principle:
Test result: bond strength (MPa)
PULL‐OFF TEST
COURSE Testing techniques for structures inspection 29th and 30th May 2012
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Steps:
PULL‐OFF TEST
DURATINET COURSE - Testing Techniques for Structures Inspection LNEC • Lisbon • Portugal • 29-30 May 2012
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Types of failure:
PULL‐OFF TEST
A Cohesion failure in the concrete substrate
A/B Adhesion failure between the substrate and the first layer
B Cohesion failure in the first layer
B/Y Adhesion failure between the first layer and the adhesive layer
Y Cohesion failure in the adhesive layer
Y/Z Adhesion failure between the adhesive layer and the dolly
COURSE Testing techniques for structures inspection 29th and 30th May 2012
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Effect of the coring depth on the interface stresses:
PULL‐OFF TEST
DURATINET COURSE - Testing Techniques for Structures Inspection LNEC • Lisbon • Portugal • 29-30 May 2012
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COURSE Testing techniques for structures inspection 29th and 30th May 2012
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Effect of surface treatment on the interface stresses (Zhou, J. et al. 2011):
PULL‐OFF TEST
COURSE Testing techniques for structures inspection 29th and 30th May 2012
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Obrigado
DURATINET COURSE - Testing Techniques for Structures Inspection LNEC • Lisbon • Portugal • 29-30 May 2012
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