Complete Recycling and Utilization of Waste Concrete ...
Transcript of Complete Recycling and Utilization of Waste Concrete ...
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Complete Recycling and Utilization of Waste Concrete through Geopolymerization
Lianyang Zhang, PhD, PE
Department of Civil Engineering and Engineering MechanicsUniversity of Arizona
November 19, 2014
Civil Engineering and Engineering Mechanics
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Outline of Presentation
Background
Research Objectives Geopolymerization Technology Research Approach Results Summary and Conclusions
Civil Engineering and Engineering Mechanics
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Background
Civil Engineering and Engineering Mechanics
The U.S. infrastructure receives an overall grade of D+ and is in urgent need to be repaired and upgraded
Repairing and upgrading existing infrastructure generates significant amount of concrete waste
Addressing the significant amount of concrete waste is a great challenge
D+
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Civil Engineering and Engineering Mechanics
How to address the significant amount of waste concrete in a sustainable way?
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Civil Engineering and Engineering Mechanics
Crushing of waste concrete for recycling
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Civil Engineering and Engineering Mechanics
Utilization of crushed waste concrete without processing Mainly for low-specification applications
Crushed-concrete base
• Road base• Embankment fill• …
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Civil Engineering and Engineering Mechanics
RCA1RCA2
Fines ?
??
Utilization of crushed waste concrete for structural concrete
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Civil Engineering and Engineering Mechanics
Compared to natural aggregate (NA), RCA has
• larger water absorption, • lower bulk density, • higher porosity, and• higher increased crushability.
Limited utilization of RCA in structural concrete
≤ 30%
Low quality of RCA
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Civil Engineering and Engineering Mechanics
Mechanical grinding Heating and scrubbing Chemical processing …
Refining of RCA
Heating and scrubbing(after Noguchi 2008)
Energy consumption ?
?
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Civil Engineering and Engineering Mechanics
Recycling of both RCA and fines
Recycling of RCA
Limitations of current WC recycling methods
– Low specification applications
– Only partially replace natural aggregate ≤ 30%
– Reprocessing of RCA Energy consumption
– Fines?
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Outline of Presentation
Background
Research Objectives
Geopolymerization Technology
Research Approach
Results
Summary and Conclusions
Civil Engineering and Engineering Mechanics
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The major goal is to develop an environmentally friendly and cost effective method for complete recycling and utilization of waste concrete (both RCA and fines) in concrete production
Research Objectives
No OPC is used !
Civil Engineering and Engineering Mechanics
Geopolymerization Technology
Production of 1 ton of OPC consumes about 1.5 tons of natural materials & 4.8 million Btu energy, and releases 1 ton of CO2 to the atmosphere
Address drawbacks of OPC
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Outline of Presentation
Background
Research Objectives
Geopolymerization Technology
Research Approach
Results
Summary and Conclusions
Civil Engineering and Engineering Mechanics
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Geopolymerization is a relatively new technology that transforms aluminosilicate materials through chemical reaction with an alkaline solution into a useful product called geopolymer
Geopolymerization Technology
Aluminosilicate Alkali (NaOH) Geopolymer pasteWater
Reaction proceeds at room or slightly elevated temperature
Civil Engineering and Engineering Mechanics
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Geopolymerization consists of 2 basic steps: (1) Dissolution of solid aluminosilicate oxides by alkali to produce
small reactive silica and alumina
(2) Polycondensation process leading to formation of amorphous to semicrystalline polymers
3D Interlocking structure!
Civil Engineering and Engineering Mechanics
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Civil Engineering and Engineering Mechanics
Advantages of geopolymer over OPC
• Energy saving and environment protection
• Wastes (fly ash, mine tailings, …) as source material
• Good volume stability
• Reasonable strength gain in short time
• Excellent durability
• High fire resistance and low thermal conductivity
• Ability to immobilize toxic and hazardous wastes
• Superior resistance to chemical attack
• …
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Outline of Presentation
Background
Research Objectives
Geopolymerization Technology
Research Approach
Results
Summary and Conclusions
Civil Engineering and Engineering Mechanics
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Research Approach
Civil Engineering and Engineering Mechanics
• The fines of crushed waste concrete (WCF) can be used together withfly ash to produce geopolymer paste/mortar with desired properties
Hypotheses
• The RCA with original “porous” cement paste/mortar adhering to themcan be (partially) geopolymerized to generate a good bond between theaggregate and the geopolymer paste/mortar
WCF Fly ash
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Civil Engineering and Engineering Mechanics
Research Tasks• Study the mechanical behavior of geopolymer paste/mortar produced
from WCF and fly ash at different conditions• Study the bonding between RCA and geopolymer paste/mortar• Study the mechanical behavior of geopolymer concrete produced
from WCF/fly ash and RCA at different conditions
l/2l
l/4l/4
bd
h
a
Precast section Paste/MortarRock slice
c
P Experimental set-up (not toscale) for four-point bendingtest
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Outline of Presentation
Background
Research Objectives
Geopolymerization Technology
Research Approach
Results
Summary and Conclusions
Civil Engineering and Engineering Mechanics
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Results
Waste concrete fines (WCF) and fly ash (FA) used
Civil Engineering and Engineering Mechanics
Chemical Compound WCF (%) FA (%)
SiO2 40.1 57.5
CaO 20.6 6.0
Al2O3 9.6 29.3
Fe2O3 3.5 2.95
K2O 2.3 NA
H2O 2.2 NA
MgO 2.1 1.36
Na2O 1.7 2.6
(Waste concrete is the tested concrete specimens in the structural lab at UA)
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Experiments on WCF/FA-based geopolymer paste
Civil Engineering and Engineering Mechanics
WCF content: 0, 25, 50, 75 and 100%
WCF FA
NaOH DI-H2O
• NaOH Concentration: 5M and 10M
NaOH Solution
Aqueous Na2SiO3
• SS/N = 1 and 2
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Effect of WCF content on UCS
Civil Engineering and Engineering Mechanics
5
10
15
20
25
30
35
0 25 50 75 100
7 da
y U
CS
(MPa
)
WCF Content (%)
NaOH = 5 M, SS/N = 1NaOH = 10 M, SS/N = 1NaOH = 10 M, SS/N = 2
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SEM micrographs
Civil Engineering and Engineering Mechanics
a
b
b
UF
CSHGPb
a b
WCF
0% WCF
50% WCF
UF
UF
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XRD patterns
Civil Engineering and Engineering Mechanics
10 15 20 25 30 35 40 45 50 55 60 65 70
2θ
Q
M MM
M
FA
CWF
10-50-2
10-0-2
T
TP
P PP
CS
H
CS
H
AA
A
A
QT
QMM
A: anorthite, M: mullite, P: portlandite, Q: quartz, T: 1.1-nm tobermorite)
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Four-point bending tests
Civil Engineering and Engineering Mechanics
NA-paste interface: NA: Limestone slice Paste: OPC and WCF/FA Paste W/S: 0.30, 0.35, 0.40
Old paste-paste interface:Old paste: Old OPC Paste: OPC and WCF/FA Paste W/S: 0.30, 0.35, 0.40
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Four-point bending tests
Civil Engineering and Engineering Mechanics
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Four-point bending tests
Civil Engineering and Engineering Mechanics
0
50
100
150
200
250
0 0.1 0.2 0.3 0.4 0.5 0.6
Forc
e (N
)
Displacement (mm)
WCF-40
Bonding strength:
2max
b)(4
3adblP
−=σ
Pmax
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Four-point bending tests – Test Results
Civil Engineering and Engineering Mechanics
0.84
0.71
0.62
0.73
0.66
0.54
0.400.450.500.550.600.650.700.750.800.850.90
0.30 0.35 0.40
Bond
ing
Stem
gth
(MPa
)
Water to Solid Ratio
NA-Paste Interface
WCF-1
OPC-1
0.70
0.56
0.49
0.45
0.52
0.57
0.400.450.500.550.600.650.700.750.800.850.90
0.30 0.35 0.40Bo
ndin
g St
emgt
h(M
Pa)
Water to Solid Ratio
Old Paste-New Paste Interface
WCF-2
OPC-2
• NA: Does not absorb water• Old paste: Absorbs water
• OPC paste: Needs water for curing/hydration• WCF GP paste: Expels water during curing
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Tests on geopolymer concrete
Civil Engineering and Engineering Mechanics
Setting time UCS
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7 day UCS of geopolymer concrete
Civil Engineering and Engineering Mechanics
Workability???
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Outline of Presentation
Background
Research Objectives
Geopolymerization Technology
Research Approach
Results
Summary and Conclusions
Civil Engineering and Engineering Mechanics
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Civil Engineering and Engineering Mechanics
Inclusion of WCF improves the UCS of geopolymer binder up to a certain WCF content and further increase of WCF content leads to decrease of UCS. In the current experiment, 50% was found as the optimum WCF content.
WCF enhances the strength mainly due to the formation of low Ca semi-crystalline CSH gel which coexists with the geopolymer gel.
The geopolymer paste-NA interface has higher strength than the OPC paste-NA interface; the geopolymer paste-old OPC paste interface also has higher strength than the OPC paste-old OPC paste interface at low water/solid ratio.
GP concrete using WCF/FA and RCA can have higher strength than the original OPC concrete.
Summary and Conclusions
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Project ParticipantsSaeed Ahmari, Rui Chen, Xiaobin Ding, Xin Ren, Rasoul Shadnia, Mo Sadat, Lino Manjarrez (Graduate students)John Lyons, Mark Gregory (Undergraduate students)
Sponsors and Supporters• National Science Foundation (NSF)• Environmental Research and Education Foundation (EREF)• Boral Material Technologies Inc. (providing fly ash samples)• Salt River Materials Group (providing fly ash samples)• ADOT (providing testing service)
Acknowledgement
Civil Engineering and Engineering Mechanics
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Civil Engineering and Engineering Mechanics
Thank You!
Lianyang Zhang, PhD, PESMART (Sustainable Materials and Recycling Technologies) Laboratory
Department of Civil Engineering and Engineering MechanicsUniversity of Arizona
(520)-626-0532, [email protected]