alternative binder materials and its application in concrete sewer … · 2018. 4. 4. ·...
TRANSCRIPT
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Alternative binder materials and its application in concrete sewer structures for possible reduction in Fat, Oil and Grease related
Sanitary Sewer Overflows
Samrin Ahmed KusumMohammad Pour-Ghaz, Joel Ducoste
NC-AWWA 17th Annual Spring Symposium, 2018
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2
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A piece of London’s 130 ton Fatberg! 3
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FOG buildup inside sewer lines
Who is responsible?
Why do we care?
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Rapid Urbanization Growth in FSEs
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Grease Inceptor
Poor GI managementInefficient GI performance
Domestic Kitchen/ Restaurants
Excessive use of dish washing detergent
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Result of FOG deposition Sanitary Sewer Overflows
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Result of FOG deposition Sanitary Sewer Overflows
SSOs impactEnvironmental impact
Public health hazard
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Why do we need to study and fight FOG now more than ever?
Replace/Rehab Sewer, $42,072
New Collector Sewer, $25,828
New Interceptor Sewer, $18,663
Clean Watershed Needs Survey Report, 2012
Numbers in Million dollars!
Provide sustainable sewer collection system
No or less FOG formation and deposition
Causes no SSOs related to FOG
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FOG Formation Mechanism
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Saponification reaction
Fat, oil and grease are semi-solid or liquid at room temperature
85% of FOG Samples contained calcium ion
Fat or Oil (Triglycerides)
FOG formation = Solidification of FOG inside sewer lines?
LCFFAs – Long chain free fatty acids Calcium ion
Hydrolysis Free fatty Acids Glycerol
Calcium ion Calcium Soap WaterFree fatty Acids
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FOG Formation Mechanism
FOG on water
surface
Slow chemical hydrolysis inside
sewer lines FFA (Free Fatty Acid)
Saponification
Calcium ion (Ca2+)
Wastewater Concrete
FOG on water
surface
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Laboratory Based FOG Formation
He et al. 2013. Water research, 47, 4451-4459.
• Synthetic laboratory wastewater made with different fatty acids, Canola oil and distilled water
• No calcium added!
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Concrete is made of• Binder (Cement + water)• Aggregate (coarse and fine)
Cement- when hydrates
C3S + H2O → CH + CSH
C2S + H2O → CH + CSH
Bad glue Good glue
Cement constituents areC3S – Tri-calcium silicatesC2S- Di-calcium silicatesC3A- Tri-calcium aluminatesC4AF- Tetra-calcium aluminoferrites andCaSO4- gypsum
Aggregates
Calcium hydroxide Calcium silicate hydrates
• Around 20-25% of cement hydrates is CH
• Around 75-80% of cement hydrates is CSH
Leaches calcium faster under corrosive media or pure water
Leaches calcium slowly under corrosive media or pure water
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Alternative Binder Benefits
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Our goal
• Reduce CH• Increase CSH
How?
• Add Pozzolans• Pozzolanic reaction: Pozzolans coverts CH into CSH
Silicates from Pozzolans + CH → CSH
PozzolansFly ashMetakaolinSilica FumeSlagCalcinated Shale
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Image from inindianawater.org
Merom coal plant and ash pond in Indiana
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Image from sain.nbii.govKingston fly ash pond spill, Tennessee
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Why Fly Ash?
Byproduct of coal fired power plant
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Why Fly Ash?
Byproduct of coal fired power plant
Inexpensive and available
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Why Fly Ash?
Byproduct of coal fired power plant
Inexpensive and available
Has pozzolanic properties – converts CH into CSH
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Why Fly Ash?
Byproduct of coal fired power plant
Inexpensive and available
Has pozzolanic properties – converts CH into CSH
Provides concrete durability
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Methodologies and Test Results
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Methodologies
Two high volume fly ash cement paste and one pure cement paste sample-
CP0FA – 0% fly ash + 100% cement
CP50FA – 50% fly ash + 50% cement
CP75FA – 75% fly ash + 25% cement
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Test Conducted
Thermogravimetric analysis (TGA) test
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Test ConductedDissolution or Leaching test
pH meterAcid supply
Stirrer
Sample
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Available CH% in samples• Increasing trend of CH
content for CP0FA as hydration period increases.
• Decreasing trend for CP50FA and CP75FA indicates effective pozzolanic reaction between cement and fly ash.
0
5
10
15
20
25
30
0 50 100 150C
H, g
ram
per
gra
m o
f bin
der (
%)
Hydration period (days)
100% cement + 0 % fly ash
50% cement + 50% fly ash
25% cement + 75% fly ash
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Calcium Leaching100% cement + 0 % fly ash100% cement + 0 % fly ash
50% cement + 50 % fly ash
0
5
10
15
0 10 20 30 40 50
Cum
ulat
ive
calc
ium
leac
hing
(mg/
l/g)
Time (Days)
50% cement + 50 % fly ash
100% cement + 0 % fly ash
25% cement + 75 % fly ash
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Compressive Strength
42 44
23
0
10
20
30
40
50
CP0FA CP50FA CP75FA
Com
pres
sive
Stre
ngth
(MP
a)
• CP75FA- low compressive strength
• Durable• Cheaper• Applicable to low
strength structures
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Reduced FOG formation
100 % cement concrete 25 % cement + 75% fly ash concrete
Nothing that attached to the surface!
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Summary
Use of FA to replace cement in concrete structures-cost effective sustainable solution
Clean Watershed Needs Survey-Total need in replacing sewer lines is $42,072M
Therefore, for the replacement of sewer lines, alternative binders will be effective to fight FOG related SSOs
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Thank You
Any Question?
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Saponification reaction between
LCFFAs – Long chain free fatty acids
and
Calcium ion
85% of FOG Samples contained calcium ion1
Ducoste et al 2008,
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FOG Formation Precursors
Fat or oil
Calcium ion
Surface for deposition
Sources of Calcium-
• Wastewater• Sewer line construction material corrosion
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Goal
Reduce CH
Increase CSH
How?
Add Pozzolans- Fly ash, metakaolin, silica fume etc.
Pozzolanic reaction: Pozzolans coverts CH into CSH
Silicates from Pozzolans + CH → CSH
Alternative binder materials and its application in concrete sewer structures for possible reduction in Fat, Oil and Grease related Sanitary Sewer OverflowsSlide Number 2Slide Number 3Slide Number 4Slide Number 5Slide Number 6Slide Number 7Slide Number 8Why do we need to study and fight FOG now more than ever?FOG Formation MechanismSlide Number 11FOG Formation MechanismLaboratory Based FOG FormationSlide Number 14Alternative Binder BenefitsSlide Number 16Slide Number 17Slide Number 18Why Fly Ash?Why Fly Ash?Why Fly Ash?Why Fly Ash?Methodologies and Test ResultsMethodologiesTest ConductedTest ConductedAvailable CH% in samplesCalcium LeachingCompressive StrengthReduced FOG formationSummaryThank You��Any Question?Slide Number 33Slide Number 34FOG Formation PrecursorsSlide Number 36