4. Self-Consolidating Concrete
(SCC)
Self-Consolidating Concrete (SCC) is
highly flowable, non-segregating
concrete that can spread into place,
fill the formwork, and encapsulate the
reinforcement without any mechanical
consolidation.
ACI 237
6. Viscosity-Modifying Admixtures
(VMAs)
“A material added to
concrete, or a cement- 35
30
based mixture, to 25
change (usually 20
15
increase) the viscosity 10
and improve the 5
stability of the mixture.”
0
0 4 8 12
VMA Dosage (fl oz/cwt)
7. How Does A VMA Work
Thickening-Type: thickens mixture making
it cohesive
Binding-Type: binds water in mixture
more potent
controls bleeding
adds thixotropic properties
8. Binding-Type VMA
The active cellulosic polymer binds up the
free water within any given mixture
holding the material together.
This makes the concrete, grout, or cement
slurry very cohesive preventing the
blending of external water with the matrix
or the internal water from leaving the
matrix.
9. Binding-Type VMA
The active polymer binds up the free water
within the mixture, holding the material together
VMA 2 VMA 2
H2 O H2 O
H2 O VMA 2 H2 O VMA 2
VMA 2 VMA 2
H2 O H2 O
VMA 2 VMA 2
H2 O H2 O
VMA 2 VMA 2
H2 O H2 O
VMA 2 VMA 2
VMA 2 VMA 2
H2 O H2 O
VMA 2 VMA 2
10. Slump Flow
Typical Slump Flow for SCC: 26 to 30 in.
Recommended slump flow for shafts:
18 to 24 in.
(Note: 16 in. slump flow ≈ 9 in. slump)
12. Slump Flow Loss Over Time
Slump flow = 28 in. Slump flow = 16 in.
Age = 15 minutes Age = 3 hours
13. Hydration-Control Admixtures
Two part system:
Stabilizer or retarder stops hydration
Activator reestablishes normal hydration
Suspends hydration up to 72 hours
Reuse of returned concrete
Stabilized for long hauls
14. Coloring Admixtures
Natural and synthetic materials
Colors: Black, Red, Yellow, Tan, Green,
Blue
6%-10% addition by weight cement
Special applications: buried electrical or
gas lines, special floors, residential
concrete
16. Colored Concrete is Cost-
Effective
Can be installed and
finished like regular
concrete
Eliminates separate
finishing or staining, thus
minimizing cost of
installation
Generally less
expensive than painting
costs over service life of
structure.
18. Curing Colored Concrete
Uneven Curing = Uneven Drying = Uneven Color
Use curing
compounds
specifically
recommended for
colored concrete.
Water cure,
membrane sheets, or
non-approved curing
compounds can
discolor concrete.
19. Dampproofing Admixtures
Product types:
Soaps
Stearates
Petroleum Products
Reduction of moisture transmission
W/R of less than 0.50 by mass
20. Pumping Aids
Improve pumpability
Aids increase viscosity or cohesion
Some aids may increase water
demand, reduce compressive
strength, increae air entrainment, retard
setting
21. Bonding Admixtures and Bonding
Agents
Bonding Admixtures Water emulsions:
Rubber
Polyvinyl chloride
Polyvinyl acetates
Acrylics
Styrene butadiene copolymers
Added to concrete for bond strength
Rate of addition 5%-20%
Bonding agents help glue materials
Restoration/repair work
Latex, grouts, copolymers
22. Grouting Admixtures
Use of Portland Cement Grouts
Stabilize Foundations
Set Machine Bases
Fill Cracks and Joints
Cement Oil Wells
Fill Masonry Walls
Grout Pre-stress tendons/anchor bolts
Fill Voids in preplaced aggregate concrete
23. Gas-Forming Admixtures
Added to Concrete and Grout to Cause
slight expansion
Use to complete grouting
Machine Bases
Post-tension ducts of prestressed concrete
Aluminum Powder/other gas forming
materials
24. Fungicidal, Germicidal, and
Insecticidal Admixtures
Control of Bacteria and Fungal growth
Types of materials
Polyhalogenated Phenols
Dieldrin emulsions
Copper Compounds
Effectiveness is temporary/ high dosage
25. Antiwashout Admixtures
Increase the cohesiveness of concrete
Allows placement of concrete in water and
underwater
Admixture increases viscosity of water
resulting in increased thixotropy and
resistance to segregation
Types of materials: Cellulose ether or
acrylic polymers
26. Admixture Compatibility Due to
Cement-Admixture Incompatibility
Fresh Concrete Properties
Slump Loss
Air Loss
Early Stiffening
Long-term Hardened Properties
Compressive strength
Placement
Poor correlation with lab test to conditions
experienced in the field