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High quality recycled aggregateHigh quality recycled aggregate

One approach One approach to to

its production technology its production technology from the view points from the view points

of of Development concept & Performance analysisDevelopment concept & Performance analysis

１

Index

1. Investigation on quality of traditional recycled aggregate(=>non processed recycled aggregate).

2. Quality of recycled aggregate after quality improvement process. (=>processed recycled aggregate by VSI

3. Assessment of the quality of concrete to use processed recycled aggregate.(Through test in being compared with natural aggregate and non processed aggregate.

4. Development concept of Kemco RC7 =High quality recycled aggregate production system= ２

Background

・ A lot of demolition concrete are daily generated by demolition works of old concrete buildings.・ More than 90% of demolition concrete is currently used for lower grade application including sub base or sub layer. ・ It is foreseen that the demand for these lower

grade application cannot absorb increasing volume of demolition concrete to keep on increasing.

　　　

The production of high quality recycled aggregate for the use of concrete for construction is highly required.

３

1.Investigation on quality of traditional recycled aggregate(=>non processed recycled aggregate .)

1) Traditional recycled aggregate:　 Demolition concrete is crushed by crusher and foreign

objects include metal and wood etc. are eliminated by magnetic and/or air separator. It was traditionally and is currently used as coarse aggregate with size range of 40-0mm or 30-0mm.

2) Its quality　　 The property of traditional aggregate has a lot of unknown

factors and its quality widely varies.

（ Field investigation of its quality)　　 a) Sample collection: The coarse and fine samples were collected at a demolition concrete processing plant every two weeks for 1 year.　　 b) The points to be investigated: I)Density, II)Water absorption, III)40tf crushing value　　　　（ BS 812 ） and IV)cement paste content.

４

Property of non processed recycled coarse aggregate

Density(Oven dry) Water absorption

・ Non processed recycled

coarse aggregate 2.18-2.34g/cm3 5-8%

・ Its original property 2.55-2.65g/cm3 0.8-2%

=Density is in reverse proportion to water absorption as shown on

the above blue single direct line.=

0

1

2

3

4

5

6

7

8

2.1 2.2 2.3 2.4 2.5 2.6 2.7Density (g/cm3)

Wate

r abso

rpti

on

(％

）

Non processed recycle aggregate

Crushed stone

Original property of non Processed aggregate

・ Lower density 　　　　　・ Higher water absorption 　

・ Higher density・ Lower water absorption

５

Lowe quality Fickleness

Higher qualityStability

Cement pasteDensity Non processed recycled coarse aggregate

(Nitric acid with 25% of concentration was used for dissolving cement paste)

・ Un removed cement paste varies from 25% up to 54%. ・ The more cement paste, the less density.

The less density is caused by cement paste.

2.20

2.25

2.30

2.35

2.40

20 25 30 35 40 45 50 55

Un removed cement paste （％）

Densi

ty (

g/c

m3) The more cement paste, the less density

６

Cement paste40tf Crushing value(BS 812)

<40tf crushing value BS812>

1) Traditional recycled aggregate =>20-28%, 2)The regular crushed aggregate=>14.5%

<Conclusion>

1) Few co-relation between cement paste & 40th crushing value was found.

2) It is presumed that there is certain co-relation between cement paste and W/C ratio.

20

22

24

26

28

30

20 25 30 35 40 45 50 55Un removed cement past （％）

40

tf c

rush

ing v

alu

e （

％）

７

(To harden three layered samples by pressing each layer 25 times by using a rod. And to give 398kN

of load on the sample for 10 minutes and measure the volume of -2.5mm content. ・・・・・・ BS812 ）

Property of non processed recycled fine aggregate

Density(oven dry) Water absorption

・ Non processed recycled fine aggregate 1.80-2.08g/cm3 9-17.5%

At the time of crushing of demolition concrete, its fragile part with low density and porous property

generates a lot of micro fine. The lower quality is caused by this micro fine.

・ Natural/Crushed fine aggregate 2.38-2.54g/cm3 2-3%

・ =Density is in reverse proportion to water absorption as shown on the above blue single direct line.=

0

5

10

15

20

1.7 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6

Density (g/cm3)

Wate

r abso

rpti

on （

％） Traditional recycled concrete

Natural sand

Crushed sand

８

・ Lower density 　　　　　・ Higher water absorption 　

Lower qualityFickleness

・ Higher density・ Lower water absorption

Higher qualityStability

Quality of non processed recycled aggregate.

=Summary=1) Non processed recycled coarse aggregate: a) Cement paste : 25-54% b) Density(oven dry) : 2.18-2.34g/cm3

c) Water absorption : 5-8% d) 40t/f crushing value:20-28% = This quality is inferior to that of natural material crushed aggregate= 2) Non processed recycled fine aggregate: a) Density(oven dry) : 1.80-2.08g/cm3

c) Water absorption : 9-17.5% = This quality is inferior to the above 1) and widely varies. 3) Conclusion:　　 =The more cement paste, the less density.=

The less density is caused by cement paste.　　　　　　　　　　 Quality improvement can be attained by removing cement paste.

９

2.Quality of recycled aggregate after quality improvement process(processed recycled

aggregate).1) Quality improvement process(How to remove cement paste): a) The material passes through Vertical Shaft Impactor (Barmac Hustler) up to 5 times(max.). This VSI has easy operation, high performance and low energy consumption. b) Micro fine with less than 1.75g/cm3 of density which is produced after 5 passes and composes 10% of 5-0mm is eliminated by specially designed air separator. * The advantage of VSI “Rock on rock” crushing system is a feature and it is good at shaping the material. As “Rock on rock” crushes the fragile part of material, it helps to remove cement paste very much for improving quality.

2) Property of a random sample: a) Size : 30-13mm b) Density(oven dry) : 2.25g/cm3

c) Water absorption : 6.45% 　　 １０

Number of “Passes” Removal of cement paste

for coarse aggregate

・ 3 passes remove 70% of cement paste.

・ 5 passes remove 80% of cement paste.

・ After 4 passes, cement paste cannot be further removed remarkably

0

10

20

30

40

50

0 1 2 3 4 5

Pass times

Un r

em

oved c

em

ent

past

（％

）

70% removed 80% removed

Easy and effective way of removal.

１１

9%14%

42%

・ 3 passes can attain more than 2.5g/cm3 of density

and less than 3 %of water absorption. => “H” grade of JIS・ To become equivalent to its original property

after 5 passes.

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

0 1 2 3 4 5 Original propertyNumbers of passes

Densi

ty (

g/c

m3)

0

1

2

3

4

5

6

7

Wate

r ab

sorp

tion(

％）

Density Water absorption

“ Ｈ” grade of JIS 3 passes attain “H” grade

１２

Easy and effective way of quality improvement.

Number of “Passes” Density and Water absorption

For coarse aggregate

・ In the zone where more than 20% of

un removed cement paste is still remained, density of its cement paste is approx.2.15g/cm3

・ In case of less than 15%, its density

drastically gets higher.

2

2.1

2.2

2.3

2.4

2.5

2.6

5 10 15 20 25 30 35 40 45

Un removed cement past （％）

Densi

ty o

f u

n r

em

oved c

em

ent

past

(calc

ula

ted)(

％）

Higher density 　　　　 few negative affect on concrete

Density gets higherLower density

In the zone where un removed cement paste

is less than 10%, density of cement paste is

more than 2.5g/cm3. It is high density and its

negative affect on quality of concrete is regarded as negligible small.

１３

（モルタル付着率と原骨材密度と再生粗骨材密度よりの付着モルタル密度計算値）

Density of un-removed cement paste in its each volume:

・“ 40ft crushing value” drops drastically through 3 passes,

however thereafter, there is no remarkable improvement.

0

5

10

15

20

25

30

0 1 2 3 4 5 Original aggregate

Crushed stone

Pass times

40

tf c

rush

ing

valu

e（

％）

Drastic drop

Gets stable

１４

Number of “Passes” “40ft crushing value (BS812)

・ Density of natural sand is stable in each particle size range.・ Density of non processed recycle aggregate is relatively low, especially in finer particle size range. ・ 3 passes shows lower density in the size range of under 0.3mm. 　　　 The particle with lower density is to be eliminated by air

separator.

1.5

1.6

1.7

1.8

1.9

2.0

2.1

2.2

2.3

2.4

2.5

5 ～2.

5

2.5

～1.

2

1.2

～0.

6

0.6

～0.

3

0.3

～0.

15

0.15

～0

Size (mm)

Densi

ty (

g/c

m3)

Natural sand

３ passes

No processed

１５

Density by each particle size range under 5mmFor fine aggregate

・ While 3 passes with air classification is still inferior to natural sand, its quality has been

very much improved if it is compared with non processed sand.

1.8

1.9

2.0

2.1

2.2

2.3

2.4

2.5

2.6

Natural sand

３ pass 3 passes with air classificationSand

Den

sity

(g

/cm

3)

0

2

4

6

8

10

12

14

16

18

Wate

r ab

sorp

tion

（％

）Density Water absorption

Improvement of density& water absorption

１６

Comparison of “density” and “water absorption” in

4 different types of fine aggregate.

Non processed

Quality of processed recycled aggregate=Summary=

Quality improvement by VSI

1) Coarse aggregate

a) 70% and 80% of cement paste were removed after 3 passes and 4 passes

respectively.

b) More than 2.5g/cm3 of density and less than 3% of water absorption were

attained after 3 passes. These figures comply with “H” grade of JIS

requirement.

2) Less than 10% of cement paste has very high density and its negative affect

on quality of concrete is regarded as negligible small.

3) Fine aggregate:

After 3 passes and elimination of less than 0.3mm of micro fine, a great deal of

quality improvement was attained.

　　　　　　　　　　 ・ The more passes, the better quality by VSI

　　　 ・ The quality becomes equivalent to the natural aggregate after 3 passes.

・ High efficiency and easy operation and maintenance. １７

3. Assessment of the quality of concrete to use processed recycled aggregate:

(Through tests in being compared with natural aggregate and non processed aggregate)

1) Test items:

a) Strength(Compression strength/Tensile strength)

b) Dry shrinkage

　 c) Durability (Freezing and thawing ， Neutralization ）

2) Sample materials:

a) Natural aggregate.

b) Non processed recycled aggregate.

c) Recycled aggregate after 3 passes by VSI.

d) Recycled aggregate after 5 passes by VSI.１８

W/C ratioCompression strength for 4 coarse samples

・ W/C ratio and compression strength for each sample are in the proportionate

relation as shown on the above lines.

・ The strength of 3 passed sample gets equivalent to that of natural aggregate.

・ The strength of non processed aggregate remarkably gets lower than those of

3 others especially in higher strength zone.

(7 days result) 　　　　　　　　　　　 (28days result)

15

20

25

30

35

40

45

1.4 1.6 1.8 2 2.2 2.4 2.6

Cement water ratio

Com

pre

ssio

n s

trength

（N

／m

m2)

Natural

Non process

３ pass

５ pass

25

30

35

40

45

50

55

1.4 1.6 1.8 2 2.2 2.4 2.6

Cement water ratioC

om

pre

ssio

n s

trength

（N

／m

m2)

Natural

３ pass

５ pass

１９

Non process

W/C ratioCompression strength for 4 fine samples

・ Concrete to use processed fine sample with 10% of fly ash added could attain

equivalent to or better compression strength than that of natural sand regardless

W/C ratio and aging of sample .

・ Compression strength in case of non processed sample is getting lower

especially in higher W/C ratio zone.

15

20

25

30

35

40

45

1.4 1.6 1.8 2 2.2 2.4 2.6Cement water ratio

Com

pre

ssio

n s

trength

（N

／m

m2)

Natural Non processedProcessedProcessed wit fly ash

25

30

35

40

45

50

55

1.4 1.6 1.8 2 2.2 2.4 2.6Cement water ratio

Com

pre

ssio

n s

trength

（N

／m

m2)

２０

(7 days result) 　　　　　　　　　　　 (28days result)

Natural

Non processedProcessedProcessed wit fly ash

Dry shrinkage for 3 fine samples

・ The dry shrinkage of 3 passed sample is equivalent to that of

crushed sand.

・ Non processed aggregate has 2.2 times higher dry shrinkage

than crushed sand.

0

500

1000

1500

2000

2500

0 50 100 150Age of concrete （ day ）

Dry

ing

sh

rinkage

（×

10

-6）

Natural

Non processed

３ pass

２ .２ times

２１

Dynamic modules of elasticity of concrete for 5 fine samples

・ Dynamic modulus of elasticity of concrete to use 3 passed fine sample with or without

natural sand is equivalent to that of crushed sand even after repeating freezing and

melting tests 300 times.

・ The concrete to use non processed fine sample dropped by approx. 50% after 300 times

of freezing and melting test if it is compared with crushed and and processed samples.

・ The concrete to use non processed coarse and fine sample dropped down to 40% after 120

times of freezing and melting test. Thereafter, no data was obtained.

0

20

40

60

80

100

120

0 50 100 150 200 250 300Cycle of freezing thawing （ times ）

Dynam

ic m

odulu

s of

ela

stic

ity （

％）

Natural

Non processed

３ passes ＋ Natural

３passesNon processed+Natural

５０％

２２

Assessment of the quality of concrete to use processed recycled aggregate:

=Summary=

　　　・ Compression strength, tensile strength,modulus of elasticity,

dry shrinkage,durability factor,neutralization of concrete which use recycled aggregate processed by VSI are equivalent to or better than those of the concrete which use crushed or natural aggregate.

=Conclusion!

Recycled aggregate which is processed by VSI

is applicable to concrete for the construction. 　　・ Non processed recycled aggregate has lower strength, higher dry

shrinkage, remarkable drop of durability factor.

=Conclusion!

Non processed aggregate is not applicable to concrete for

construction but for very limited uses.

２３

4. Development concept of Kemco RC7=High quality recycled aggregate production

system=

“key concept” of its development　　 1. Production of high quality aggregate. a) To comply with “H” grade of JIS b) To produce sand well quality controlled by air screen.　　 2. Quality control of product.　　 3. Low initial cost thanks to “Dry system” 4. Low running and maintenance costs thanks to VSI & Air screen 5. Less space requirement, non dust and low noise.

２４

Outer view of RC7

BM 7

Air Screen

Dust collector

Product stock pile

・ All the equipment are in vertically integrated flow and in compact style.・ Low noise, no dust low vibration => Environmentally friendly ２

５

　　　１ pass

　　　２ pass

　　　３ pass

Processing flow of system

Crushing and shaping by BM7

Classification, sieving and cleaning of the surface of aggregate by air screen

Stock bin for subsequentprocess

More passed Product

　　　　　

２６

BM 7

・ Vertical shaft impactor (More than 1,200 units were supplied to market) ・“ Rock on rock” crushing can remove cement paste easily.・ Low running cost by セルフライニング方式 ２

７

Air Screen(RCAS)

・ 4 layers of sieves・ Classification, sieving and cleaning of the surface of aggregate by air screen. => Multi function

２８

Working mechanism of air screenWorking mechanism of air screen

２９

Numbers of passesDensity and Water absorption

（ Fine aggregate ）１～２ pass ・・・・ “Ｌ” grade of JIS３ pass ・・・・・・・ “Ｍ” grade of JISClassification by density ・・ ・・・“Ｈ” grade of JIS

（ Coarse aggregate ）１ pass ・・・・“Ｌ” grade of JIS２ pass ・・・・“Ｍ” grade of JIS３ pass ・・・・“Ｈ” grade of JIS

３０

Classification by density

（ Product ） Coarse （ Product ） Sand

(Material)Images of product

３１

Model line-ups of RC7

・ 3 model lines-ups are available per capacity.

Model ＲＣ７－１ ＲＣ７－２ ＲＣ７－３

Feed －４０ｍｍ ４０ｔ／ｈ ６０ｔ／ｈ ８０ｔ／ｈ

Volume of stock bin １０ｔ／ｈ １６ｔ／ｈ ２０ｔ／ｈ

Max capacity １２０ｔ／ｈ １９０ｔ／ｈ ２５０ｔ／ｈ

Dust collector ３６０ｍ３／ｍｉｎ ６００ｍ３／ｍｉｎ ８００ｍ３／ｍｉｎ

Barmac Hustler ＵＳ３０１Ｈ ＵＳ３２２Ｈ ＵＳ３９４ＨAir Screen ＲＣＡＳ１２００ ＲＣＡＳ１９００ ＲＣＡＳ２５００

３２

RC7 Pilot plant for sample test

We are ready to run test for the customer.

Required material volume is 3 tons

３３

Thank you!Thank you!

Kotobuki Engineering & Kotobuki Engineering &

Manufacturing Co.,ltd.Manufacturing Co.,ltd.

http://www.kemco.co.jphttp://www.kemco.co.jp