Templates

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Crack Free and Durable Concrete Repairs with the
BaenzigerBlock, experiences since 1995
Heinz Bänziger, Sika Services AG Senior Vice
President BU Contractors Head Technical
Department Construction Head Market Field
Refurbishment Strengthening
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Crack Free Repairs with the BaenzigerBlockPresent
ation at ICRI Congress October 25, 2001
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Crack Free Repairs with the BaenzigerBlockThe
basics of successful concrete repair

• A concrete repair mortar has to fulfill the
  requirements which are necessary
• to support the existing damaged concrete
  structure regarding-
• Strengths (compressive, flexural, tensile)
• Bond to substrate (gt 1.5 MPa)
• Durability (a part of sustainability)
• Protection
• Elastic modulus (e.g mortars with polymeric
  binder)
• Cracking

But the most important requirement is
Workability, placement only mortars with
excellent processing can reach the high
expectations
Bad Workability, placement Bad Quality
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Crack Free Repairs with the BaenzigerBlockDevelop
ment The philosophy Test facility with fastest
possible respond of the most important
properties! Killing factors visible after 1 day
to max 28 days with one single test!

1. Workability Bad placement bad quality
return to RD
2. Crack behavior Cracks reduced protection -
return to RD
3. Adhesion to substrate No adhesion not usable
- return to RD
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Crack Free Repairs with the BaenzigerBlockDevelop
ment The philosophyTest facility with fastest
possible respond of the most important
properties! Killing factors visible in shortest
time span as possible!

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Restrained shrinkage
Free drying shrinkage
TensilestressN/mm
Shrinkagestrain mm/m
Strength limit
!Cracking!
0RH
20RH
40RH
60RH
80RH
100RH
!Drying induced free contraction of the
samples!
!Free contraction restrained due to mechanical
property of substrate!
free vs. restrained shrinkage
Baenziger Block
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Crack Free Repairs with the BaenzigerBlock Crack
simulation of concrete repair mortars needs

• bond to a concrete substrate
• specimen sizes which reflects reality
• edges
• free shrinkage parts
• restrained shrinkage parts
• connection joints repair to existing
• corners
• substrate roughness according practice
• variable layer thickness
• water absorption of substrate concrete
• re-produce able climatic conditions

Job Site
BaenzigerBlock
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Crack Free Repairs with the BaenzigerBlock Crack
simulation of concrete repair mortars needs

• bond to a concrete substrate
• specimen sizes which reflects reality
• edges
• free shrinkage parts
• restrained shrinkage parts
• connection joints repair to existing
• corners
• substrate roughness according practice
• variable layer thickness
• water absorption of substrate concrete
• re-produce able climatic conditions

Job Site
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Crack Free Repairs with the BaenzigerBlock Crack
simulation of concrete repair mortars needs

• bond to a concrete substrate
• specimen sizes which reflects reality
• edges
• free shrinkage parts
• restrained shrinkage parts
• connection joints repair to existing
• corners
• substrate roughness according practice
• variable layer thickness
• water absorption of substrate concrete
• re-produce able climatic conditions

Job Site
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Crack Free Repairs with the BaenzigerBlock Crack
simulation of concrete repair mortars needs

• bond to a concrete substrate
• specimen sizes which reflects reality
• edges
• free shrinkage parts
• restrained shrinkage parts
• connection joints repair to existing
• corners
• substrate roughness according practice
• variable layer thickness
• water absorption of substrate concrete
• re-produce able climatic conditions

Job Site
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Crack Free Repairs with the BaenzigerBlock Crack
simulation of concrete repair mortars needs

• bond to a concrete substrate
• specimen size which reflects reality
• edges
• free shrinkage parts
• restrained shrinkage parts
• connection joints repair to existing
• corners
• substrate roughness according practice
• variable layer thickness
• water absorption of substrate concrete
• re-produce able climatic conditions

Job Site
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Crack Free Repairs with the BaenzigerBlock Crack
simulation of concrete repair mortars needs

• bond to a concrete substrate
• specimen size which reflects reality
• edges
• free shrinkage parts
• restrained shrinkage parts
• connection joints repair to existing
• corners
• substrate roughness according practice
• variable layer thickness
• water absorption of substrate concrete
• re-produce able climatic conditions

Job Site
3cm
6cm
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Crack Free Repairs with the BaenzigerBlock Crack
simulation of concrete repair mortars needs

• bond to a concrete substrate
• specimen size which reflects reality
• edges
• free shrinkage parts
• restrained shrinkage parts
• connection joints repair to existing
• corners
• substrate roughness according practice
• variable layer thickness
• water absorption of substrate concrete
• re-produce able climatic conditions

Job Site
Climate Chamber
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Crack Free Repairs with the BaenzigerBlock The
Size of the BaenzigerBlock
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Crack Free Repairs with the BaenzigerBlock The
Preparation of the Block
Due to reproducibility reasons we use only one
concrete mixture
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Crack Free Repairs with the BaenzigerBlock Testing
, alternative conditions
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Crack Free Repairs with the BaenzigerBlock Results
and Interpretation
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Crack Free Repairs with the BaenzigerBlock Results
and Interpretation
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Crack Free Repairs with the BaenzigerBlock Baenzig
erBlock and practice 15 years ago!
Concrete Repair Mortar in practice 15 years ago
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Crack Free Repairs with the BaenzigerBlock Today
Benchmark of so called Non Cracking Cement
Mortars
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Crack Free Repairs with the BaenzigerBlock 1.
Sample Results Crack evolution over time
After 2 days
After 4 days
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Crack Free Repairs with the BaenzigerBlock 1.
Sample Results Crack evolution over time
After 9 days
After 28 days
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Crack Free Repairs with the BaenzigerBlock 2.
Sample Results Crack evolution over time
After 28 days
After 56 days
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Crack Free Repairs with the BaenzigerBlock 2.
Sample Results Crack evolution over time
After 90 days
The crack development of cement mortars is
different! Some mortars are cracking within the
first 24 hours others just start to crack after
a few days or a few weeks! From our long term
experience we knowThe cracking behavior of
cement concrete repair mortars should be tested
up to one year!
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Crack Free Repairs with the BaenzigerBlock Today
Benchmark of Non Cracking Cement Mortars
Its possible! No cracks after 1 year!
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Crack Free Repairs with the BaenzigerBlock Additio
nal Test Methods
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Crack Free Repairs with the BaenzigerBlock Results
Crack evolution over time

• The BaenzigerBlock enables a lot of additional
  information
• date when the cracks appears
• wideness of the cracks and wideness progress
• crack development in length
• numbers of cracks and development of cracks over
  time
• type of cracks, e.g. single crack, spider web
  cracks
• sensitivity of crack behavior, at corners, at
  edges on full surface etc.
• loss of bond (de lamination) of the substrate
  due internal strengths and restricted shrinkage

The BaenzigerBlock reflects the reality! But the
final approval of the cracking performance Is
always the application on a real structure!
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Crack Free Repairs with the BaenzigerBlock Concret
e Repair Mortar development within the last 15
years
High quality Concrete Repair under hardest
conditions
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Crack Free Repairs with the BaenzigerBlock Concret
e Repair Mortar development within the last 15
years
Today it is possible Architectural Concrete
without any Cracks
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Crack Free Repairs with the BaenzigerBlock Investi
gations of independent Institutes
THE EFFECT OF CONCRETE SUBSTRATE STRENGTH ON THE
ADHESION PROPERTIES OF POLYMER MODIFIED REPAIR
MATERIALS A.J.C. Jooste Rand Afrikaans University
ABSTRACT. It is a known fact that the preparation
of the concrete substrate plays an important role
on the adhesion properties of polymer modified
repair materials. Some uncertainty exist as to
the influence of the concrete substrate strength
on the adhesion properties of concrete repair
materials. This paper reports on research done at
the Rand Afrikaans University (South Africa), to
investigate the influence of concrete substrate
strength on the bonding properties of various
repair materials. Different concrete substrate
strengths were simulated by using the Banziger
test block (20, 30 and 40 MPa). On these blocks
seven different repair materials, from three
different manufacturers, were placed. The
placing specifications of the manufacturers were
strictly followed. The samples were fully cured
for 28 days, during which the crack behaviour was
observed at 1, 7 ,14 and 28 days. The influence
of concrete substrate strength on crack behaviour
was experimentally investigated. By determining
the bonding strength between repair material and
concrete after 28 days, the influence of concrete
strength on bonding strength was investigated.
To compare practise with laboratory work a trial
repair was done on a part of the R.A.U. complex.
This repair was evaluated in the same manner as
the Banziger test blocks. An important
conclusion drawn from the observations, is that
the actual method of substrate preparation plays
an important role in determining bond strength.
In substrates of low strengths, micro-cracks are
easily formed. These cracks lead to reduced
bonding strengths.
1999
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Crack Free Repairs with the BaenzigerBlock Investi
gations of independent Institutes
2004
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Crack Free Repairs with the BaenzigerBlock Investi
gations of independent Institutes
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Crack Free Repairs with the BaenzigerBlock Investi
gations of independent Institutes
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Crack Free Repairs with the BaenzigerBlock Investi
gations of independent Institutes
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Crack Free Repairs with the BaenzigerBlock Investi
gations of independent Institutes
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Crack Free Repairs with the BaenzigerBlock Investi
gations of independent Institutes
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Crack Free Repairs with the BaenzigerBlock Investi
gations of independent Institutes
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Crack Free Repairs with the BaenzigerBlock Investi
gations of independent Institutes
Ring tests do not simulate reality!
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Crack Free Repairs with the BaenzigerBlock Investi
gations of independent Institutes
App. 2002
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Crack Free Repairs with the BaenzigerBlock Investi
gations of independent Institutes
App 2006
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Shrinkage does not correlate with cracking!
Crack Free Repairs with the BaenzigerBlockOur
investigations Correlation Cracking - Shrinkage
1400
Mortar 1
Mortar 4
Mortar 3
1200
Mortar 5
1000
800
free - 21C - 60 R.H.)
Shrinkage (µm/m) (EN 12617-4
600
Mortar 2
Mortar 6
400
200
0
0
1
2
3
4
5
6
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Ranking of cracking on Bänziger Block
Bench mark at same age of specimens
No cracks
Full of cracks
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Crack Free Repairs with the BaenzigerBlockOur
investigations Moisture conditions in concrete
and mortar before and during the repair process
Development of internal moisture content during
hardening and mortar application
Of course a block of steel would not show similar
behavior and the results would be different!
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Crack Free Repairs with the BaenzigerBlockOur
investigations Alternative Crack Testing Method
based on our experiences

• Target smaller, less weight, reliable,
  reproducible
• Correlation
• Measuring cracking time on different devices

Cracking time of mortars Mortar 1 Mortar 2
Steel Ring Test 32 days 5-6 days
BaenzigerBlock 10-17 days 9-11 days
Alternative Laboratory Test Method of Sika 14 days 9-11 days
Steel Ring Test does not simulate the site
conditions
Steel has no surface roughness, does not breath
and does not absorb water of the repair mortar
100 moist in contact zone mortar/steel
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Crack Free Repairs with the BaenzigerBlockConclus
ion of laboratory investigations, Alternative
Crack Testing Method based on our experiences

• Based on fundamental research of Technology
  Center
• Improved lab test equipment
• Possibility to identify directly which
  formulation parameters impact cracking
• Final laboratory testing will still involve
  BaenzigerBlock
• The final market release of a concrete repair
  mortar is still pending on the performance of
  selective applications on job site!

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Crack Free Repairs with the BaenzigerBlockSummary
of over 15 years experience

• During the past 20 years we made big improvements
  and gained more knowledge regarding cracking
  behavior of cement mortars!
• Cracking of mortars is influenced by different
  parameters
• Shrinkage of mortar
• Environmental conditions
• Concrete Substrate
• Application and placement quality
• Relaxation properties of the mortar
• We have learned to formulate low (no) cracking
  mortars
• We introduced the BaenzigerBlock in all
  development centers around the globe
• It is our best tool for benchmarking different
  formulations or comparisons with competitors
  products
• The BaenzigerBlock is one of the best tool to
  test the mortar due to the close simulation of a
  real of concrete repair!

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Crack Free Repairs with the BaenzigerBlockOutlook
2020

• Due to high investments in infrastructures over
  the past decades, costs for maintenance and
  refurbishment of all (concrete) structures will
  increase dramatically!
• The costs have already exceeded the budgets of
  many states!
• Lack of maintenance is reality
• Examples of collapses we see every day in the
  news
• Functioning infrastructures are the backbone of
  every economy
• New structures must have high sustainability and
  durability
• The repair and protection of existing structures
  requires long lasting and sustainable methods
• Sustainability is like a plant, it starts very
  small and is more important and more powerful
  with the age!
• only if all components of a system meet the
  requirements of sustainability and durability,
  the overall system can meet this requirement
  also!
• It is one of our main tasks to invest in products
  which align with Sustainability!

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Thanks for Attention!