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ICRI Convention, October 2010, Pittsburgh
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Crack Free and Durable Concrete Repairs with the BaenzigerBlock, experiences since 1995
Heinz Bänziger, Sika Services AGSenior Vice President BU ContractorsHead Technical Department ConstructionHead Market Field Refurbishment & Strengthening
ICRI Convention, October 2010, Pittsburgh
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Crack Free Repairs with the BaenzigerBlockPresentation at ICRI Congress October 25, 2001
ICRI Convention, October 2010, Pittsburgh
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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 necessaryto support the existing damaged concrete structure regarding-
- Strengths (compressive, flexural, tensile)- Bond to substrate (> 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
ICRI Convention, October 2010, Pittsburgh
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3. Adhesion to substrateNo adhesion = not usable - return to R&D
2. Crack behaviorCracks = reduced protection - return to R&D
1. WorkabilityBad placement = bad quality – return to R&D
Crack Free Repairs with the BaenzigerBlockDevelopment: 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!
ICRI Convention, October 2010, Pittsburgh
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2. Crack behaviorCracks = reduced protection
3. Adhesion to substrateNo adhesion = not usable
1. WorkabilityBad placement behavior = bad quality
Crack Free Repairs with the BaenzigerBlockDevelopment 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
Tensilestress[N/mm]
100% RH90% RH80% RH70% RH60% RH50% RH40% RH30% RH
0%RH 20%RH 40%RH 60%RH 80%RH 100%RH
Free drying shrinkage
Shrinkagestrain [mm/m]
Baenziger Block
!Drying induced „free“ contraction of the samples!!Free contraction restrained due to mechanical property of substrate!
free
vs.
res
trai
ned
sh
rin
kag
e
Strength limit
!Cracking!
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Crack Free Repairs with the BaenzigerBlockCrack 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
300mm
1000mm
ICRI Convention, October 2010, Pittsburgh
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Crack Free Repairs with the BaenzigerBlockCrack 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
ICRI Convention, October 2010, Pittsburgh
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Crack Free Repairs with the BaenzigerBlockCrack 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
ICRI Convention, October 2010, Pittsburgh
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Crack Free Repairs with the BaenzigerBlockCrack 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
ICRI Convention, October 2010, Pittsburgh
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Crack Free Repairs with the BaenzigerBlockCrack 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
ICRI Convention, October 2010, Pittsburgh
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Crack Free Repairs with the BaenzigerBlockCrack 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
ICRI Convention, October 2010, Pittsburgh
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Crack Free Repairs with the BaenzigerBlockCrack 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
ICRI Convention, October 2010, Pittsburgh
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Crack Free Repairs with the BaenzigerBlockThe Size of the BaenzigerBlock
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Crack Free Repairs with the BaenzigerBlockThe Preparation of the Block
Due to reproducibility reasons we use only one concrete mixture
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Crack Free Repairs with the BaenzigerBlockTesting, alternative conditions
ICRI Convention, October 2010, Pittsburgh
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Crack Free Repairs with the BaenzigerBlockResults and Interpretation
ICRI Convention, October 2010, Pittsburgh
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Crack Free Repairs with the BaenzigerBlockResults and Interpretation
ICRI Convention, October 2010, Pittsburgh
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Crack Free Repairs with the BaenzigerBlockBaenzigerBlock and practice 15 years ago!
Concrete Repair Mortar in practice 15 years ago
ICRI Convention, October 2010, Pittsburgh
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Crack Free Repairs with the BaenzigerBlockToday Benchmark of so called “Non Cracking Cement Mortars”
Mortar 1“non cracking mortar”
Mortar 2“non cracking mortar”
Mortar 3“low cracking mortar”
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Crack Free Repairs with the BaenzigerBlock1. Sample Results “Crack evolution over time”
After 2 days
After 4 days
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Crack Free Repairs with the BaenzigerBlock1. Sample Results “Crack evolution over time”
After 9 days
After 28 days
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Crack Free Repairs with the BaenzigerBlock2. Sample Results “Crack evolution over time”
After 28 days
After 56 days
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Crack Free Repairs with the BaenzigerBlock2. 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 know:The cracking behavior of cement concrete repair mortars should be tested
up to one year!
ICRI Convention, October 2010, Pittsburgh
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Crack Free Repairs with the BaenzigerBlockToday Benchmark of “Non Cracking Cement Mortars”
It’s possible!No cracks after 1 year!
ICRI Convention, October 2010, Pittsburgh
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Crack Free Repairs with the BaenzigerBlockAdditional Test Methods
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Crack Free Repairs with the BaenzigerBlockResults “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 BaenzigerBlockConcrete Repair Mortar development within the last 15 years
High quality Concrete Repair under hardest conditions
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Crack Free Repairs with the BaenzigerBlockConcrete 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 BaenzigerBlockInvestigations of independent Institutes
THE EFFECT OF CONCRETE SUBSTRATE STRENGTH ON THE ADHESION PROPERTIES OF POLYMER MODIFIED REPAIR
MATERIALSA.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 BaenzigerBlockInvestigations of independent Institutes
2004
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Crack Free Repairs with the BaenzigerBlockInvestigations of independent Institutes
ICRI Convention, October 2010, Pittsburgh
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Crack Free Repairs with the BaenzigerBlockInvestigations of independent Institutes
ICRI Convention, October 2010, Pittsburgh
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Crack Free Repairs with the BaenzigerBlockInvestigations of independent Institutes
ICRI Convention, October 2010, Pittsburgh
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Crack Free Repairs with the BaenzigerBlockInvestigations of independent Institutes
ICRI Convention, October 2010, Pittsburgh
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Crack Free Repairs with the BaenzigerBlockInvestigations of independent Institutes
ICRI Convention, October 2010, Pittsburgh
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Crack Free Repairs with the BaenzigerBlockInvestigations of independent Institutes
ICRI Convention, October 2010, Pittsburgh
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Crack Free Repairs with the BaenzigerBlockInvestigations of independent Institutes
Ring tests do not simulate reality!
ICRI Convention, October 2010, Pittsburgh
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Crack Free Repairs with the BaenzigerBlockInvestigations of independent Institutes
App. 2002
ICRI Convention, October 2010, Pittsburgh
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Crack Free Repairs with the BaenzigerBlockInvestigations of independent Institutes
App 2006
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Shrinkage does not correlate with cracking!
0
200
400
600
800
1000
1200
1400
0 1 2 3 4 5 6 7Ranking of cracking on Bänziger Block
Sh
rin
ka
ge
(µm
/m)
(EN
126
17
-4
fre
e -
21
°C -
60%
R.H
.)
No cracks Full of cracks
Mortar 2
Mortar 5Mortar 4
Mortar 6
Mortar 3Mortar 1
Crack Free Repairs with the BaenzigerBlockOur investigations: Correlation Cracking - Shrinkage
Bench mark at same age of specimens
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relative humidity [-]
t = 28 d
t = 56 d
t = 55.5 d
t = 59 d
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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Target: smaller, less weight, reliable, reproducible
Correlation Measuring cracking time on different devices
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
Crack Free Repairs with the BaenzigerBlockOur investigations: Alternative Crack Testing Method based on our experiences
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
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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!
Crack Free Repairs with the BaenzigerBlockConclusion of laboratory investigations, Alternative Crack Testing Method based on our experiences
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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 competitor’s products The BaenzigerBlock is one of the best tool to test the mortar due to
the close simulation of a real of concrete repair!
Crack Free Repairs with the BaenzigerBlockSummary of over 15 years experience
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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!
Crack Free Repairs with the BaenzigerBlockOutlook 2020
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Thanks for Attention!