Cements in Nebraska: NDOR Research Into FlyAsh Alternatives
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Transcript of Cements in Nebraska: NDOR Research Into FlyAsh Alternatives
Cements in NebraskaMick Syslo, P.E.Materials & Research Engineer, NDOR
Cements In Nebraska• A quick review• What’s changed• Where we are headed
A QUICK REVIEWCement
• Crushed Rock Limestone* Shale Iron Ore Sand
• Heated to 2700 oF
QUICK FACTSMost consumed substances in the world?
#1 - Water
#2 - Concrete
#3 -
Back to CementCement
• Crushed Rock Limestone* Shale Iron Ore Sand
• Heated to 2700 oF
CO2 Emissions• 50% Limestone Burn
off CaO3 = CaO + CO2
• 50% burning of fuel to heat
What’s Changed?
Late 70’s – 80’s• Emission Requirements began to
change• Resulting in changes in the
alkali / alkalinity of Cement–Sodium Oxide (Na2O)–Potassium Oxide (K2O)–Calcium Oxide (CaO)
The Effects?Concrete
• Rock Ledge Rock Gravel Sand
• Water
• Cement
Since Cement changed Concrete Changed
•ASR
Not new, but MUCH MUCH more prevalent!
ASR = Alkali-Silica Reaction• Alkali – Cements (CaO)• Silica – Aggregate
(SiO2)• Water (H2O) ASR
Gel
CaO
H2OSiO
START EXPERIMENT
The Effects?Concrete produced after 1985 began showing early distresses
The Effects?By late 1990’s and early 2000’s Nebraska….well the nation had major issues!
The Effects?Some pavements build during the same era did not have the distresses
NDOR Reviewed the PCC Mix designs & began a research project.
• All projects with IPF or IPN Cement had performed well while the others had not
– As a result in 2004 moving forward only IPF could be used
– 25% F-ash blended with Type I/II cement
Chemical Testing of Cement
• How do we verify that we are getting 25% F-ash
– NDOR established a chemical ratio
– No major changes in cement specification for next 10 yrs
CaO SiO2
Changes go on elsewhere
• Other states become aware of the their ASR issues and soon several states began requiring IPF. (TxDOT)– Results in lower F-ash supply availability
• Emission requirements for changed for Coal Ash production(Remove more Nox gases-Ammonia, Carbon-Mercury, & Sulfur – Sodium)
– Results in lower F-ash supply availability• 2 major flyash incidents in Tennessee & North
Carolina(Rivers contaminated from ash slides)– Results in risk of flyash being labeled Hazardous
Where are we headed?
• Chemistry
Where are we headed?
• We can get the right chemical balance through blending or other materials.
– NDOR established a chemical ratioCaO SiO2
How it worksMaterial SiO2 CaO Ratio
CaO/SiO2 Mitigate ASR
Cement I/II 22 63 2.8 NO
How it worksMaterial SiO2 CaO Ratio
CaO/SiO2 Mitigate ASR
Cement I/II 22 63 2.8 NOCement + 25% F-ash 29 48 1.65 YES
How it worksMaterial SiO2 CaO Ratio
CaO/SiO2 Mitigate ASR
Cement I/II 22 63 2.8 NOCement + 25% F-ash 29 48 1.65 YES
Cement +25% C-ash 25 52 2.08 NO
How it worksMaterial SiO2 CaO Ratio
CaO/SiO2 Mitigate ASR
Cement I/II 22 63 2.8 NOCement + 25% F-ash 29 48 1.65 YES
Cement +25% C-ash 25 52 2.08 NO
Cement + 25% Slag 25 57 2.28 NO
How it worksMaterial SiO2 CaO Ratio
CaO/SiO2 Mitigate ASR
Cement I/II 22 63 2.8 NOCement + 25% F-ash 29 48 1.65 YES
Cement +25% C-ash 25 52 2.08 NO
Cement + 25% Slag 25 57 2.28 NO
Cement +40% Slag 27 53 1.96 YES
How it worksMaterial SiO2 CaO Ratio
CaO/SiO2 Mitigate ASR
Cement I/II 22 63 2.8 NOCement + 25% F-ash 29 48 1.65 YES
Cement +25% C-ash 25 52 2.08 NO
Cement + 25% Slag 25 57 2.28 NO
Cement +40% Slag 27 53 1.96 YES
Cement +25% Cal. Clay
26 50 1.68 YES
Our Current Specification• Allows the following cements:– IP, 20% or 25% F-ash or Calcined Clay
– IS, 30%-40% Slag
– IT, Blends of SCM’s up to 40% F-ash, C-ash,
Calcined Clay, Slag, Lime Dust, Zeolites…….
Material SiO2 CaO Ratio CaO/SiO2
Mitigate ASR
Cement I/II 22 63 2.8 NO
Cement + 25% F-ash 29 48 1.65 YES
Cement +25% C-ash 25 52 2.08 NO
Cement + 25% Slag 25 57 2.28 NO
Cement +40% Slag 27 53 1.96 YES
Cement +25% Cal. Clay
26 50 1.68 YES
Know your cement• Each cement is different– Workability
– Set Times (saw cutting)
– Strength Gains (opening strength)
– Water Demand
EXPERIMENT RESULTS
Questions?