Enhancing the Properties of Recycled Aggregate Concrete … · 2015-05-20 · Annual Concrete Seminar @ Apr 29, 2015 香港理工大學 THE HONG KONG POLYTECHNIC UNIVERSITY Engineering

Enhancing the Properties of Recycled

Aggregate Concrete Products by Carbonation

Ir Prof. C S POON

The Hong Kong Polytechnic University

Concrete: From Production to Recycling Annual Concrete Seminar 2015

Annual Concrete Seminar @ Apr 29, 2015

香港理工大學

THE HONG KONG

POLYTECHNIC UNIVERSITY

CONTENTS

Motivation

Previous research

Technical background

CO2 curing of recycled aggregate

CO2 curing of eco-block


香港理工大學

THE HONG KONG


INTRODUCTION

Global Warming is caused by the sharply increased greenhouse gases (GHG) emission by human activities with cement production accounting for 6%-7% of CO2 emission or 0.88t (0.9t for China) CO2 per ton of cement produced.

CO2 emissions from simplified cement production

process G. Habert et al. / Cement and Concrete Research 40 (2010) 820–826


香港理工大學

THE HONG KONG


INTRODUCTION

The booming urbanization and industrialization in China

Besieged by Garbage: Can We Just Burn Them?


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THE HONG KONG


Batching plants

Excavation

Construction

Refurbishment Renovation

Demolition

Road Work

C&D Waste

Motivation

15 million tonnes

About 800 tonnes of crushed concrete are produced each day. (Assuming crushed concrete account for 2% of C&DW)


香港理工大學

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Engineering issue

Motivation

Although the reuse of concrete waste as Recycled Aggregate (RA) can reduce the consumption of limited natural resources and thereby save construction costs, the use of RA also has some shortcomings:

• Attached cement paste

• Higher water absorption

• Lower bulk density

• Weak interfacial transition zone -leading to a decrease of workability, strength and durability of RAC…


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INTRODUCTION

Summary on the previous research on effects of using recycled concrete aggregates (RCA) on properties of concrete products.

Con

cret

e Bl

ocks


香港理工大學

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Previous research studies

Removing Mechanical grinding (Shima, et al, 1999)

Ultrasonic cleaning (Katz, 2004)

Heating method (Shima,et al, 2005)

Presoaking RCA with acid solution (Tam, et al, 2007)

Surface modification technique for the original aggregate (Tsujino, et al, 2007)

8

Strengthening

• Impregnating RCA with cementitious slurry (Katz, 2004 ; Li, et al, 2009) • Impregnating RCA with water glass (Cheng, et al, 2004) • Impregnating RCA with polyvinyl alcohol (PVA) (Kou, et al, 2010) • Calcium carbonate biodeposition (Anna, et al, 2012)


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CO2 CURING TECHNIQUE

Carbonation of cement hydration products: CH and CSH are predominant components to react with carbon dioxide in cement paste during carbonation.

CSH(s) + CO2(g) → CaCO3(s) + silica + H2O(l)

Ca(OH)2 (s) + CO2(g) → CaCO3(s) + H2O(l)

33.0 ml/mol 36.9ml/mol

11.8% increase in solid volume


香港理工大學

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Technical background

Carbonation of anhydrous phase of cement:

CO2 can be used to cure hydraulic and non-hydraulic calcium silicate to achieve very high strength in a short period of time. (Young et al., 1974; Berger, et al., 1979)

3CaO·SiO2 +yH2O +(3-x)CO2 → xCaO·SiO2· yH2O +(3-x) CaCO3

2CaO·SiO2 +yH2O +(2-x)CO2 → xCaO·SiO2· yH2O +(2-x) CaCO3

Comparison of compressive strength development in carbonated and hydrated mortar, Young et al., 1974.


香港理工大學

THE HONG KONG


CO2 curing

Microstructure of eco-block:

Before carbonation After carbonation

In carbonated samples, CaCO3 and CSH are intermingled and cannot be identified as separated phases.


香港理工大學

THE HONG KONG


CO2 curing

NMR analysis of carbonated cement paste

-150 -135 -120 -105 -90 -75 -60 -45

Chemical shift, ppm

S3-2hCC-28dWC

S2-2hCC-7dWC

S1-2hCC

Q0

Q1 Q2 Q4

Sample information: Cement: water= 1: 0.18 S1: 2 hours CO2 curing (CC); S2: 2h CC + 7 days’ water curing (WC); S3: 2h CC+28d WC

29Si NMR spectra for S1, S2 and S3


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CO2 curing

NMR analysis of carbonated cement paste Q0 : unhydrated cement clinkers

Q1 : chain end of CSH Q2 : chain middle of CSH Q4 : amorphous silica. CO2 curing process enhanced the formation of silica gel

-145 -130 -115 -100 -85 -70 -55

Original Simulated Q4 Q2 Q1 Q0 Residual


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Objective: -- to study the effects of CO2 curing on properties of new/old recycled aggregates;

-- to investigate the effects of carbonated recycled aggregates on properties of concrete.


香港理工大學

THE HONG KONG


Old RCAs sourced from old demolished structures Provided by C&D waste recycling plant, TioStone Environmental Limited ;



香港理工大學

THE HONG KONG


New RCAs on basis of designed concrete mixtures Provided by Gammon Construction Limited and Crushed by TioStone Environmental Limited.

Amount of designed concrete mixture: about 14m3 Amount of delivered NRCA to PolyU: about 6 tons



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Properties of recycled aggregate Aggr. Type Conditions

Size (mm)

Density (kg/m3) Water absorptio

n (%)

10% fine value (KN)

Crushing value (%)

CO2 uptake

(%) Apparent Particle

NRCA

Non-carbonated

<5 2624±26 2044±15 12.3±0.4 — — —

5-10 2624±26 2205±15 7.2±0.2 — — —

10-20 2605±15 2249±10 6.1±0.3 125.8±0.

8 27.8±2.8 —

Carbonated under 0.1bar

<5 2680±12 2091±19 10.2±0.6 — — 2.10

5-10 2633±14 2255±11 6.4±0.2 — — 0.74

10-20 2610±13 2300±14 5.1±0.2 129.7±0.

9 21.9±2.0 0.65

Carbonated under 5bar

<5 2688±15 2099±22 9.1±0.5 — — 2.15

5-10 2663±23 2262±10 6.0±0.2 — — 0.81

10-20 2609±18 2301±9 5.0±0.2 130.9±0.

9 20.6±2.0 0.66

ORCA

Non-carbonated

<5 2661±16 2075±11 10.6±0.4 — — — 5-10 2557±3 2189±11 6.4±0.3 — — —

10-20 2561±12 2554±2 5.5±0.1 117.7±0.

7 26.6±2.5 —

C b t d <5 2680±21 2088±16 9.1±0.5 — — 1.89

5 10 2585 5 2249 8 5 8 0 3 0 54


香港理工大學

THE HONG KONG



Effects of carbonated RA on density of concrete

2,200

2,250

2,300

2,350

2,400

0 20 40 60 80 100

Dens

ity o

f coc

nret

e (K

g/m

3 )

Replacement of NRCA by volume (%)

Non-carbonated New RCAsCarbonated New RCAs

2,240

2,260

2,280

2,300

2,320

2,340

2,360

2,380

2,400

2,420

N ORCA 5BarORCA

0.1BarNRCA

5BarNRCA

NRCA

Desit

y of

conc

rete

(kg/

m3 )

1.5%0.3%


香港理工大學

THE HONG KONG



Effects of carbonated RA on compressive strength of concrete

2025303540455055606570

0 20 40 60 80 100

Com

pres

sive

stre

ngth

(MPa

)


Carbonated New RCAs

Non-carbonated New RCAs

0.6%

10.8%

11.0% 16.6% 22.6%

30

35

40

45

50

55

N ORCA 5BarORCA

0.1BarNRCA

5BarNRCA

NRCA

Com

pres

sive

stre

ngth

(MPa

)

22.6%

6.6%


香港理工大學

THE HONG KONG



Effects of carbonated RA on elastic modulus of concrete

20

22

24

26

28

30

32

0 20 40 60 80 100

Mod

ulus

of e

last

icity

(GPa

)

Proportion of carbonated NR(%)

Carbonated New RCAsNon-carbonated New RCAs

1.4%

4.1%

9.9%13.9%

13.2% 20

22

24

26

28

30

32

N ORCA 5Bar ORCA

0.1Bar NRCA

5Bar NRCA

NRCA

Mod

ulus

of e

last

icity

(MP

a)

13.2%

8.3%


香港理工大學

THE HONG KONG



Effects of carbonated RA on chloride permeability of concrete

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

N ORCA 5BarORCA

0.1BarNRCA

5BarNRCA

NRCA

Tota

l cha

rge

pass

ed in

coul

ombs

at

56 d

ays

36.4%

15.4%

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

0 20 40 60 80 100

Tota

l cha

rge

pass

ed in

coul

ombs

at

56 d

ays



8.8%4.4%

13.6%

24.5%

36.4%


香港理工大學

THE HONG KONG



Effects of carbonated RA on gas permeability of concrete

3

6

9

12

15

18

21

24

27

N ORCA 5BarORCA

0.1BarNRCA

5BarNRCA

NRCACo

effic

ient

of g

as p

erm

eabi

lity

at

56 d

ays (

×10-1

7 m2 )

37.5%

43.6%

3.0

6.0

9.0

12.0

15.0

18.0

21.0

24.0

0 20 40 60 80 100

Coef

ficie

nt o

f gas

per

mea

bilit

y at

56

day

s (×

10-1

7 m2 )



21.7%32.2%

24.2%

34.4%

42.4%

Eco-Blocks

第三代

Recycled Aggregate Recycled Aggregate

+ Recycled Glass

Recycled Glass + Recycled Aggregate + Photo-catalyst

第一代

第二代


香港理工大學

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Objective: --to study factors affecting the CO2 curing process of eco-

blocks prepared with recycled aggregates.


香港理工大學

THE HONG KONG



Materials: Aggregate: Crushed granite (CGA);

Crushed mortar(CMA, <5mm, the parent mortar was

prepared with : cement: water: crushed fine granite = 1: 0.6: 3,

and attained a 28-day compressive strength of 52.7 MPa.)

Binders: ASTM Type I Portland cement


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Samples preparation and curing:

Zhan BJ, Poon CS, Shi CJ. Materials Characteristics Affecting CO2 Curing of Concrete Blocks containing Recycled Aggregates. In revision.

CO

2 Tank

Data logger

Regulator

Pressure gauge

Vacuum Pump Safety valve

Humidity& Temperature sensor

Samples

Silica gel

Compacted specimens (Ø 52±0.5mm × H 50mm )

CO2 curing setup 2 hours, +0.1Bar


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Effect of moisture content of blocks:

R² = 0.9604

R² = 0.9692

0

10

20

30

40

50

60

70

0 2 4 6 8 10 12 14

Cur

ing

degr

ee, %

Moisture content, %

M-CGA M-CMA

CEM: water: CGA=1:0.32:3 CEM: water: CMA=1:0.55:3

12.09% 10.37% 8.90% 7.51% 5.59%


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Effect of moisture content:

18.5 20.9

24.3 26.1

21.4

14.7

9.9

0

5

10

15

20

25

30

1.97 2.4 3.15 4.02 5.52 6.2 7.41

Com

pres

sive

str

engt

h, M

Pa

Moisture content, %

(A): M-CGA Strength value after 6 hrs steam curing: 24.1 MPa

15 15.2 16.8 18.8

16.2 15.8 14.1

8.4

0

5

10

15

20

25

30

5.59 5.98 6.43 7.41 7.51 8.9 10.37 12.09

Com

pres

sive

str

engt

h, M

Pa

Moisture content, %

(B): M-CMA

Strength value after 6 hrs steam curing: 19.3 MPa

CEM: water: CGA=1:0.32:3 CEM: water: CMA=1:0.55:3


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Effect of curing degree:

Relationship between compressive strength and CO2 curing degree

y = 0.6753x + 3.7519 R² = 0.936

y = 0.1895x + 6.5209 R² = 0.7899

0

5

10

15

20

25

30

0 10 20 30 40 50 60

Com

pres

sive

stre

ngth

, MPa

Curing degree, %

M-CGA

From Shi CJ et al. (2011)


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Effect of recycled aggregate content:

Mix Code A/C ratio Cement Water CMA CGA Density,

Kg/m3 Theoretical voids ratio

CMA00 3 1 0.32 0 3 2286 0.060 CMA25 3 1 0.38 0.75 2.25 2236 0.056 CMA50 3 1 0.44 1.5 1.5 2186 0.057 CMA75 3 1 0.50 2.25 0.75 2136 0.060 CMA100 3 1 0.55 3 0 2086 0.064


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32.4

y = -1.77x2 + 13.49x + 5.66 R² = 0.99

0

20

40

60

0 5 10 15

CMA00

35.3

y = -1.28x2 + 12.70x - 0.60 R² = 0.76

0

20

40

60

0 5 10 15

CMA25

42.6

y = -0.92x2 + 7.9x + 25.2 R² = 0.99

0

20

40

60

0 5 10 15

CMA50

44.2

y = -1.05x2 + 12.11x + 6.21 R² = 0.95

0

20

40

60

0 5 10 15

CMA75

51.9

y = -0.93x2 + 10.89x + 19.60 R² = 0.97

0

20

40

60

0 5 10 15

CMA100

Note: X axis : moisture content (%) Y axis : curing degree (%)


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Recycled aggregate content:

CMA00, α=8.3% CMA00, α=32.4%

CMA100, α=16.1% CMA100, α=51.9%


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26.1

16.9 16.1 16 16.8

35 31.6

29.2 26.3

23.6

0

10

20

30

40

CMA00 CMA25 CMA50 CMA75 CMA100

Com

pres

sive

stre

ngth

, MPa

After 2 hours CO2 curing

After 7 days moiste curing


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Effect of post water curing:

0

10

20

30

40

1 2 4 12 24

Com

pres

sive

stre

ngth

, MP

a

CO2 curing time, hours

Strength after CO2 curing Strength gain after 7 days water curing Strength gain after 28 days water curing

CEM: water: CMA=1:0.55:3


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CO2 CURING OF ECO-BLOCK

Proportions of eco-block mixes

Proportion Load-bearing blocks

(LB) Non load-bearing blocks

(NLB) Control TA50 TA100 Control TA50 TA100

Aggr./Cem Ratio 3 3 3 10 10 10

Type ⅠOPC 1 1 1 1 1 1

10mm Granite 0.7 0.7 0.7 3.5 3.5 3.5 Crushed fine granite 2.3 1.15 0 6.5 3.25 0 T.M. Aggregate (TA) 0 1.15 2.3 0 3.25 6.5

During the mixing process, the amount of mixing water was adjusted to same consistence

Zhan BJ, Poon CS, Kou SC. CO2 curing for improving the properties of concrete blocks containing recycled aggregates. Cement and Concrete Composites, 2013, 42: 1-8.


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Samples preparation in lab

Cubical samples (70mm × 70mm × 70mm)

for compressive strength testing;

Prism samples (285mm × 25mm × 25mm)

for drying shrinkage testing;

All the samples were compacted to

pressure of about 30MPa, and kept

for 30s; then remolded immediately.



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Curing regime: (for 6 hours, 12 hours and 24 hours)

CO2 curing Moist curing



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Strength variation

26.5

34.4

38.1

30.6

40.9

49.1

15

25

35

45

55

6 hours 12 hours 24 hours

Com

pres

sive

stre

ngth

, MPa

LB-ControlMoist curing CO2 curing

24.6

33.7 35.233.8

41.6

49.9

6 hours 12 hours 24 hoursCuring time

LB-TA50

23.7

33.136.6

30.8

41.9

50.4


LB-TA100

8.711.6

16.5

12.5

16.017.8

0.0

5.0

10.0

15.0

20.0

25.0


Com

pres

sive

stre

ngth

, MPa

NLB-ControlMoist curing CO2 curing

6.5

11.6

15.5

9.2

16.8

23.0

6 hours 12 hours 24 hoursCuring time

NLB-TA50

8.8

12.2

15.7

12.6

18.4

22.7


NLB-TA100

Compared to conventional moist curing, CO2 curing improved the compressive strength of both the non-load- and load-bearing blocks dramatically and rapidly with strength gains ranging from 108% to 151% within 24-h CO2 curing time.



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Comparison of drying shrinkage for LB-TA50 sample after different curing regime

0.01%

0.03%

0.05%

0.07%

0 7 14 21 28

Dry

ing

shrin

kage

val

ue

Drying time/days

LB-TA50-6h CO2 curing LB-TA50-12h CO2 curing LB-TA50-24h CO2 curing LB-TA50-Moist curing



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High-efficiency and low-cost approach for CO2 capture and storage (CCS).

ZERO cost for CO2 capture (28€/t CO2) and transport(1-6€/t CO2);

ZERO risk of CO2 leaking from storage site;

LOW cost for CO2 storage(1-8€/t CO2).




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CONCLUSIONS

After the CO2 curing process, there was a significant reduction in water absorption and porosity of the recycled concrete aggregate.

The moisture content and the mortar content of the recycled aggregate are of crucial importance in affecting the CO2 curing process.

Utilization of CO2-cured recycled aggregate can improve the mechanical and durability properties of the new concrete.


香港理工大學

THE HONG KONG


CONCLUSIONS

Compared to conventional water curing method, CO2 curing improved the compressive strength of eco-blocks significantly with rapid strength gain. The drying shrinkage values of the blocks were reduced as well.

The CO2 curing of recycled aggregate concrete products provides a low-cost method to sequestrate CO2.

Research at PolyU: Turning wastes to eco-construction products

C&D Waste Incinerator Ash Glass Waste Timber


香港理工大學

THE HONG KONG


ACKNOWLEDGMENT

Research Grants Council Environmental Protection Department Environment and Conservation Fund Civil Engineering and Development Department The Hong Kong Polytechnic University Tiostone Environmental Ltd. SHK Properties Gammon Construction Co. Ltd. Innovation Technology Fund

Thank You!

www.eco-block.hk Email: [email protected]

Documents

Enhancing the Properties of Recycled Aggregate Concrete … · 2015-05-20 · Annual Concrete Seminar @ Apr 29, 2015 香港理工大學 THE HONG KONG POLYTECHNIC UNIVERSITY Engineering