Recycling Concrete

56
1 RECYCLING CONCRETE -The present state and future perspective- Koji Sakai Kagawa University, Japan TCG-JSCE JOINT SEMINAR Nov. 20, Athens

Transcript of Recycling Concrete

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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

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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

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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)

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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.