VMA for Concrete Cellulose Ether as Viscosity Modifying Agent (VMA) for the use in concrete ....
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Dow Coatings & Construction VMA for Concrete Cellulose Ether as Viscosity Modifying Agent (VMA) for the use in concrete
Transcript of VMA for Concrete Cellulose Ether as Viscosity Modifying Agent (VMA) for the use in concrete ....
Dow Coatings & Construction
VMA for Concrete
Cellulose Ether as Viscosity Modifying Agent (VMA) for the use in concrete
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Proven chemistry from combined know-how
A heritage of 40+ years of development,
formulation and application expertise
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Chemistry of Cellulose Derivatives
O
HOOMe
O
OH
3
NaOH Cellulose
Alkali
cellulose
HEMC
CMC
Ethylene oxide
Chloro acetic acid
- NaCl
- NaCl
„Activating“
Monochloromethane
Ethylene oxide
HEC O
H O O H
O
O H
O
H O O M e
O
O H
O
O O H
O
O H O
O H
O
O
H O O N a
O N a
O
H O O H
O H
O
O N a C l
C l
H H
H
O
O
Cellosize™ Products
Walocel® M Products
Walocel® C Products
HPMC
- NaCl
Monochloromethane
Propylene oxide
C l
H H
H
Walocel® M / Methocel® Products
O
Could react
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Why the use of VMA becomes more important
Use of coarse aggregates will increase in future
Leads to higher yield stress more Plastiziser or higher w/c ratio
Increase of PCE acceptance as HRWR
CO2 footprint / eco concrete
Less use or exchange of OPC / higher dosage of HRWR
Without Cellulose Ether as VMA
No robustness against raw material variation (e.g. +/- 10l/m³ water)
Segregation
Bleeding
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Main performance criteria which can be controled / influenced by a VMA
Rheological behavior
Slump (Flow)
V-funnel discharging time (for SCC)
Mortar yield point
Mortar viscosity
Behaviour over time (0h, 1h, 2h)
Bleeding
Air entrainment
Air void content
Density
Cement hydration / Setting
Ultrasonic
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Investigation on CE chemistry for the use in concrete
A multi dimensional Design of Experiment (DoE) was made to define the
desired Cellulose Ether chemistry
Substitution
• DS(M); MS(HE) – HEC, HEMC, MC
– CMC and HPMC not part of this investigation
Molecular weight
• Viscosity in a 2% aqueous solution
Particle size
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Summary Chemistry Findings
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Slump V-funnel time
Bleeding Static yield
Dynamic yield
Mortar viscosity
Air void content
Density Setting time
DS(M)
No bleeding observed
MS(HE)
V2
Particle size
Potentially best performing HEMC:
• High DS – Highest impact regarding
cement setting
• Low to medium MS
• Low to medium viscosity
• Fine powder
Structure parameters:
DS(M): 1.65 – 2.20
MS(HE): < 0.50
Viscosity: < 30.000 mPas
(2% aqueous solution)
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Typical rheological behaviour of cement paste (Herchel-Bulkley)
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0
20
40
60
80
100
120
140
160
180
200
0 10 20 30 40 50 60 70 80
Shear rate (s-1)
Shear stress (Pa)
p 0
p
0 Yield stress
Plastic viscosity
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Viscosity increase by using CE in water and cement paste
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x 10
x 2
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CE increases robustness of SCC
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CE gives a wider range for w/c ratio
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Summary
CE as VMA increases the yield point and the viscosity slightly and
increase robustness against w/c ratio variation.
With a high subtitution degree no delay in hydration of cement
Use of CE prevents bleeding
Additional air entrainment could be reduced with the right mix of MS(HE)
and molecular weight of the CE
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Thank You
Dipl.-Ing. Marc Schmitz
