TCG-JSCE Joint Seminar (Sakai)library.tee.gr/digital/m2469/m2469_sakai.pdf · TCG-JSCE JOINT...
Transcript of TCG-JSCE Joint Seminar (Sakai)library.tee.gr/digital/m2469/m2469_sakai.pdf · TCG-JSCE JOINT...
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RECYCLING CONCRETE-The present state and
future perspective-
Koji Sakai
Kagawa University, Japan
TCG-JSCE JOINT SEMINARNov. 20, Athens
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ConcreteConstituents: coarse aggregate, fine
aggregate, cement (limestone and clay),and water“The most bountiful resources on the Earth”Therefore, concrete is the second most
consumed material on the Earth after water.
at present: more than 20 billion tons1950: 2 billion tons
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Environmental Problems in Concrete Sector
Global warming
Resource depletion
Waste disposal
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CEMBUREAU10.8%
CIS3.2%
Other America6%
USA3.1%
Africa4.7%
Others Europe*0.5%
Oceania0.4%
Japan2.2%
India6.5%
Others Asia13.5%
China49%
World Cement Production by Regions and Main Countries
*Including EU27 countries not members of CEMBUREAU
2.83 billion tons
CO2 emission from cement: 2.46 billion tons
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Estimated Cement Demand (CSI-WBCSD)
8000
10000
6000
4000
2000
0Cem
ent
dem
and
(m
illi
on t
ons)
’90 ’05 ’20 ’35 ’50 ’65 ’80 ’95
Scenario A1Scenario A2Scenario B1Scenario B2
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Warning by IPCC Report
“CO2 emissions must be reduced by 85 - 50% by 2050 compared with the 2000 level to limit CO2 to 350 -400 ppm. Even if we could do it, a temperature rise of 2.0 – 2.4 ºC will be inevitable.”
What is the current situation?
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CO2 Observation in Hawaii
Keeling Curve
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Consumption of Natural Resources on Earth
26Total
1.3Others
3Wood
0.7Gold production (gold ore)
1Steel production (iron ore)
20Aggregates
(billion tons)
L. R. Brown: ECO-ECONOMY
CO2 emissions from aggregate production: 160 million tons
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Total CO2 Emissions from Concrete Sector
Total: about 5.9 billion tons (Cement,
aggregate, steel, execution, transportation)
It corresponds to 20% of the total fossil fuel origin CO2 emissions, which is 30.0 billion tones in 2007.
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Resource Input into Construction Sector in Japan
TotalTotal
ConstructionConstruction1,000 (million 1,000 (million t/year)t/year)50%50%
Total: 2,000 (million Total: 2,000 (million t/year)t/year)
ConstructionConstruction
Total: 1,000 (million Total: 1,000 (million t/year)t/year)
ConcreteConcrete500 (million t/year)500 (million t/year)50%50%
OthersOthers
SteelSteel
WoodWood
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Amount of waste in Major Regions
53228241
Municipal waste
77317510
Construction and demolition waste
JapanUSAEurope
Amount of waste (Mt)
Source: CSI - Recycling concrete
12
Waste Output from Construction Industries in Japan
Industrial WasteIndustrial Waste
ConConstructionstruction7575 (million t/year)(million t/year)1818%%
Total: 412 (million t/year)Total: 412 (million t/year)
Construction WasteConstruction Waste
Total: 75 (million t/year)Total: 75 (million t/year)
ConcreteConcrete32 (million 32 (million t/year)t/year)41%41%
EnergyEnergy
AgriculturAgriculturee
PulpPulp
SteelSteel
ChemicalChemicalOthersOthers
Asphalt Asphalt concretconcretee
SludgeSludgeWoodWood OthersOthers
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Construction Waste in Each Country
日本
アメリカ
EU15
ルクセンブルク
アイルランド
フィンランド
スウェーデン
ギリシャ
デンマーク
ポルトガル
オーストリア
ベルギー
オランダ
スペイン
イタリア
フランス
イギリス
ドイツ
0 5000 10000 15000 20000
建設廃棄物(万㌧)
59003000
24002000
13001100
700500
3003002002001001000
1800013500
8500
建設廃棄物(万㌧)Germany
UKFrance
ItalySpain
NetherlandBelgiumAustria
PortugalDenmark
GreeceSwedenFinlandIreland
LuxembourgEU 15 countries
USAJapan
Construction Waste (x10,000 t)
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Final Disposal Sites for Wastein Japan
120
140
160
180
200
220
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
Pos
sib
le w
aste
in
fin
al d
isp
osal
are
a(m
illi
on t
on)
GeneralIndustrial
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Utilization Formof Recycled Concrete
Reuse in original form by cutting them into smaller blocks (very limited)
-slab reuse
Use as aggregate
- road sub-base or
- underground stabilization
- concrete
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Use of Recycled Aggregate% Recycled Aggregate of Total Aggregate Use
0
5
10
15
20
25
Cro
atia
Den
mar
k
No
rwa
y
Po
rtu
gal
Tu
rke
y
Sp
ain
Fin
lan
d
Slo
vaki
a
Irel
and
Ital
y
Sw
eden
Ro
man
ia
Fra
nce
Au
stri
a
Po
lan
d
Cze
ch R
epu
blic
Ger
man
y
Sw
itze
rlan
d
Bel
giu
m
Net
her
lan
ds
Un
ited
Kin
gd
om
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Recycling Ratio of Concretein Japan
0 10 20 30 40
Emission of Concrete Lumps (million t)
2000
1995
1990
Recycle
Disposal
Mostly used as road sub-base
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Predicted Amount of Future Concrete Lumps in Japan
Pro
duct
ion (
million
t)
600
500
400
300
200
100
01950 2000 2050
Year
Concrete productionConcrete production
ConcreteConcretewastewaste
Demand forDemand forroad road subbasesubbase
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Demolished Concrete LumpsDemolished Concrete LumpsDemolished Concrete Lumps
Jaw CrusherJaw CrusherJaw Crusher
Impact CrusherImpact CrusherImpact Crusher
Vibratory SievesVibratory SievesVibratory Sieves
Road Subbase,Backfill
Road Subbase,Road Subbase,BackfillBackfill
Cone CrusherCone CrusherCone Crusher
Vibratory SievesVibratory SievesVibratory Sieves
Vibratory SievesVibratory SievesVibratory Sieves
Low Quality RecycledCoarse
Aggregates
Low Quality Low Quality RecycledRecycledCoarse Coarse
AggregatesAggregates
Heating TowerHeating TowerHeating Tower
Coarse Aggregate ScrubberCoarse Aggregate ScrubberCoarse Aggregate Scrubber
Fine Aggregate ScrubberFine Aggregate ScrubberFine Aggregate Scrubber
Low Quality Recycled
Fine Aggregates
Low Quality Low Quality RecycledRecycled
Fine Fine AggregatesAggregates High Quality
Recycled Coarse
Aggregates
High Quality High Quality Recycled Recycled CoarseCoarse
AggregatesAggregates
High Quality Recycled
FineAggregates
High Quality High Quality Recycled Recycled
FineFineAggregatesAggregates
PowderPowderPowder
Vibratory SievesVibratory SievesVibratory Sieves
(a) Road Subbase(a) Road Subbase (b) Low Quality(b) Low QualityRecycled AggregatesRecycled Aggregates
(c) High Quality(c) High QualityRecycled AggregatesRecycled Aggregates
Recycling process of concrete lumps
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The Most General Technologiesfor Concrete Recycling
Road sub-base material
Non-structural concrete
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Properties of Recycled Aggregate
5-10mmnot less than 10mm
No 1st 2nd 3rd
Water Absorption
(%)
Recovery Percentage
(%)
Recycled FineAggregate
Recycled CoarseAggregate
Powder
Size of SuppliedConcrete Lumps
Sand
Gravel
Cement Paste
No 1st 2nd 3rd OriginalConcrete
Number of Crushing Treatment
Number of Crushing Treatment
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Recycling Technologies of Demolished Concrete in Japan
(1) Heating and rubbing method
(2) Eccentric-shaft rotor method
(3) Mechanical grinding method
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Heating and rubbing method
Concrete rubble
Powder
Recycled fine aggregate
Recycled coarse aggregate
Packed bed heater
Coarse aggregate recovering equipment
(Ball Mill)
Dustextractor
Vibrating screen
Fine aggregate recovering equipment
(Mill)
Heating: 300℃
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Input HopperInput Hopper
Heating TowerHeating Tower
Fine Aggregate MillFine Aggregate Mill
ClassifierClassifier
Dart CollectorDart Collector
Powder Storage TankPowder Storage Tank
Recycled Coarse Recycled Coarse AggregateAggregate
Recycled Fine Recycled Fine AggregateAggregate
Coarse Aggregate MillCoarse Aggregate Mill
Heating and Rubbing Method Plant
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Mechanism of Heatingand Rubbing Method
Heating at 300C
Rubbing process
Concrete rubbleWeakening of
hardened cement paste
Removal of powdered
cement hydrate
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Recycled Aggregates & By-product Powder by H&R Method
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Abso
rpti
on (
%)
Oven-dry density (g/cm3)
0
2
4
6
8
10
12
14
2.0 2.2 2.4 2.6
Virgin Aggregate
Recycled Coarse/ Former Systems
Recycled Fine/Former Systems
High QualityHigh QualityRecycled AggregateRecycled Aggregate
Quality of Recycled Aggregates
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An Example of Application ofHeating and Rubbing Method
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On-site Concrete Resource Recycling System and CO2
Closed-loopconcretesystem
Usual case
P2 P3P1 P4
2,530 17,852 2,349
0 5,000 10,000 15,000 20,000
1,042
1,010 19,183 3,580
25,000
CO2 Emission(t)
P1:Road sub-bases production, P2: Recycled aggregate recovering, P3: Concrete mixing and delivery, P4: Ground improvement
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Eccentric-Shaft Rotor Method
Crushed concrete
lumps
Eccentric shaft rotor
Motor
Crushed concrete lumps are passed downward between an outer and inner cylinder.
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Old apartment Houses12 x 4-storiedConcrete lump: 11,500 t
New apartment Houses7 x 9-19-storiedRecycled coarse aggregate: 3,000 tRecycled concrete volume: 3,000 m3
( Total concrete volume:40,000 m3 )
An Example of Application ofEccentric-Shaft Rotor Method
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Mechanical Grinding Method
Passinghole
Drum4000mm
External diameter:1500mm
Chargeinlet
Recycledaggregatedischarge
PartitionPlate
Steel ball
Coarse and fine aggregates are produced by separating a drum into small sections with partitions.
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Japan Industrial Standards for Recycled Aggregate
JIS A 5021– Recycled aggregate for concrete - Class H
JIS A 5022– Recycled concrete using recycled
aggregate Class M
JIS A 5023– Recycled concrete using recycled
aggregate Class L
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not morethan
13.0
not morethan
7.0
not morethan
7.0
not morethan
5.0
not morethan
3.5
not morethan
3.0
Water Absorp-tion(%)
--
not lessthan
2.2
not lessthan
2.3
not lessthan
2.5
not lessthan
2.5
Oven-dry density(g/cm3)
FineCoarseFineCoarseFineCoarse
Class - LClass - MClass - H
Specified Values of Recycled Aggregate in JIS
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Limits of Amount of Deleterious Substances for RA-H
3.0Total
0.1Wood, Paper, AsphaltF
0.5PlasticsE
0.5Inorganic substances other than plaster D
0.1PlasterC
0.5GlassB
2.0Tile, Brick, Ceramics, Asphalt concreteA
Limits (mass%)Deleterious substancesCategory
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Application of Recycled Aggregate
Scope of application
Backfill concrete, blinding concrete, and Backfill concrete, blinding concrete, and leveling concreteleveling concrete
Class - L
Members not subjected to drying or Members not subjected to drying or freezingfreezing--andand--thawing actionthawing action, such as piles, underground beam, and concrete filled in steel tubes
Class - M
No limitationsNo limitations are put on the type and segment for concrete and structures with a nominal strength of 45MPa or less
Class - H
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Utilization of By-product Powders
Large amount of by-product powders– Possible uses
• Cement material
• Ground improving material
• Addition to road bottoming
• Concrete addition
• Asphalt filler
• Inorganic board material
– Demands• Quality stabilization
• Reduction of quality control
cost
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Barriers of Concrete Recycling(CSI)
Low economic cost of virgin aggregateNon-regular supply of construction and
demolished waste (C & DW)C & DW on-site waste management plans are
neededMisconception that recovered concrete is of
low qualityClassification of recovered concrete as
waste can increase reporting and permit requirements. Extra limitations can be placed on use.
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Barriers of Concrete Recycling(CSI)
Processing technology for recovery of concrete should consider possible air and noise pollution impacts as well as energy consumption.
For specialized application (e.g. high performance concrete), there are some limitations on fitness for use.
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Future Technologies for Concrete Recycling
Concept of Completely Recyclable Concrete– Recyclable concrete like steel and aluminum
– Production process of concrete
• Conventional downstream approach– focusing on
» Cost reduction
» Efficiency in production
•• New production systemNew production system– incorporating upstream (inverse) processesupstream (inverse) processes in
consideration of recyclability
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Requirements for Ideal Recycling
Save energy
Make high performance concrete
Reduce waste
Conserve natural resources
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Cement-recovery Type Completely Recyclable Concrete (The Uni. Of Tokyo)
• Concrete in which binders, additives and aggregates are all made of cement or materials of cement, and all of these materials can be used as raw materials of cement after hardening
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Application of Cement Recovery Type CRC
Precast Concrete Foundations Made from CRC in Kita-kyusyu
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Aggregate-recovery Type Completely Recyclable Concrete (The Uni. Of Tokyo)
• Concrete which is designed to reduce the adhesion between aggregate and the matrix to an extent that does not adversely affect the mechanical properties of concrete by modifying the aggregate surfacesbeforehand, thereby facilitating recovery of original aggregate
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Mechanism of Aggregate-recovery Type CRC by Surface Modification
Chemical treatment
Physical treatment
The principal ingredient of the coating agent is mineral oil. The agent hydrolyzes in alkali conditions of fresh concrete, forming acidic matter and indissoluble amalgam on the surface of the aggregate. The surface coating results in decreased amounts of cement hydrate, and leads to decreased adhesive strength between aggregate and paste matrix, allowing easy recovery of the original aggregate.
The coating agent is a water-soluble synthetic resin emulsion, which is applied in process of abrasion, and which is chemically stable in fresh concrete. The uneven surfaces of virgin aggregate become smoother, the shape of the aggregate being roughly maintained. This has the effect of decreasing adhesive strength between aggregate and paste matrix.
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Concrete recycle by surface modification treatment to Concrete recycle by surface modification treatment to aggregate aggregate
EExisting technologyxisting technology
Proposed technologyProposed technology
Existing technologyExisting technology was very difficult was very difficult to ensureto ensure ttraderade--off relationshipoff relationship ::
< Recycled aggregate >High-quality aggregate with low energy
Crush
< Concrete >
Crush
Mortar matrixSurface improving agent
To enhance a peeling effect
Aggregate
Mortar matrixAggregate (Water repellent agent)
of aggregate from mortar matrix
““MMechanical propertiesechanical properties””
““RRecycling performanceecycling performance””andand
47
Energy consumption of the aggregate recycling utilizing microwavEnergy consumption of the aggregate recycling utilizing microwave heatinge heatingis small compared to existing technologies.is small compared to existing technologies.
0
5
10
15
20
25
30
35
40
2Q
uant
ity
of C
O
emit
ted
(kg/
ton
: A
ggre
gate
) Quantity of CO emitted
* Heating process : Rated power of Microwave oven
* Crushing process : Anamnestic case ( Rubbing method)
Rubbing methodManufacturing process of aggregate
Microwave heating
Exi
stin
g
Exi
stin
g Microwave heating (Heating time)30sec. 60sec. 90sec. 120sec.
2
by using test (The amount of one processing is 10kg.)
in Microwave-based Aggregate Recovering
tech
nolo
gy 2
tec
hnol
ogy
1(H
igh
qual
ity)
(Mid
dle
qual
ity
- H
igh
qual
ity)
Emission of COEmission of CO22 during Aggregate Recyclingduring Aggregate Recycling
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Recovery of Aggregate fromRecovery of Aggregate fromConcrete Waste by Electric Concrete Waste by Electric Pulsed Power TechnologyPulsed Power Technology
(Kumamoto University: M. (Kumamoto University: M. ShigeishiShigeishi, , T. T. NamihiraNamihira, M. , M. OhtsuOhtsu, and H. Akiyama), and H. Akiyama)
49
Pulsed Power Method
ConcreteMarx Generator
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Fracture of Concrete by EPP
The dielectric breakdown of gas occurs in concrete by the pulsed electric discharge at first. Ionized gas forms plasma and explosive volumetric change tears concrete matrix.
The shock wave is also generated at the same time. The shock wave generates the tensile stress at the boundary and mortar is separated from aggregate.
Gas(pore)
Cement &aggregate Aggregate mortar Aggregate mortar
Tensile stress
Aggregate mortar
Tensile stress
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Controllable Fracture
• 20 shots
• 60 shots
• 100 shots
Concrete can be demolished under the controlled fracture by frequency of discharge and energy of discharge per once.
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Environmental Benefit
• For processing of 1000 kg of concrete waste;
7.24 kg-CO2/t (+)11.32 kg-CO2/t (*)CO2
Emission
17.8 kWh/t (+)29 kWh/t (*)Energy Consumption
Pulsed Power method
Rubbing method with pre-heating
(*) refer to RECOMMENDATION OF ENVIRONMENTAL PERFORMANCE VERIFICATION FOR CONCRETE STRUCTURES (DRAFT), JSCE, 2006.
(+) estimated from experimental results of processing of 4 kg of concrete.
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Green Building Design and Practices to Foster Recycling (CSI) Sustainability in initial design (durable
flexible designs, off-site prefabrication, and deconstruction design)
Optimum use of input materials in design (reuse, recycling, building energy efficiency)
On-site waste management plans (maximize the potential for materials reuse and recycling and minimize negative environmental and health effects)
These aspects should be reasonably incorporated into green building rating systems. At present, not enough.
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Concluding Remarks(To be cont’d)
Concrete should be repeatedly recycled with less energy.
More efficient recycling technologies should be developed.
Recycling should be of high quality from the user’s point of view.
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Concluding Remarks (Cont’d)
The reasonable regulations and design/green-rating systems should be established to promote concrete recycling.
Concrete recycling will become one of the most important elements for construction sustainability
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Acknowledgment
I would like to thank Dr. Noguchi, The University of Tokyo, and Dr. Shigeyoshi and Prof. Ohtsu, Kumamoto University, for providing their PPT information on concrete recycling.