Icsc-jueves-1 Taking Recycled Aggregate Concrete Into a New Era

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Plano de evacuación

Taking Recycled Aggregate Concrete

Into a New Era

Mohamed A Mahgoub, PhD. PE Assistant Professor and Program Director

Concrete Industry Management Department of Engineering Technology

New Jersey Institute of Technology, Newark, NJ ACI 555 “Concrete with Recycled Materials”

Committee Chair

6 February, 2014

THANK YOU

Manuel Lascarro Andrea Urueña

Recycled Aggregate Concrete (RAC)

Recycling concrete provides sustainability in several different ways:

• Saving natural resources

1250 million tons

44% x 1250=550 million tons was used for concrete

Annual production of sand and gravel in the US

• Construction and Demolition Debris

25% increase in 7 years!

• Construction and Demolition Debris

Roofing

Brick

Concrete

Wood

Landfill debris

Scrap iron

Roofing

170 x 66%= 112 million tons! (net concrete waste in 2003)

2000 ft

400 ft

Average composition of demolition debris

66%

• RAC is a concrete made of reclaimed aggregates; • Quality of RAC is dependent on the quality of RCA; • Care must be taken to prevent contaminations such as asphalt and gypsum.

Recycled Aggregate Concrete (RAC)?

RCA Natural

• Mostly road sub-base • erosion control • pipe and drain ducts • parking lots • filter material

Current uses of RCA:

States recycling concrete as road base

• Widespread application of RAC, such as structure and seismic, requires knowledge of RAC behavior (unconfined and confined) • The main objective of this research was to develop stress-strain models for use in structure and seismic analysis (confined and unconfined).

Problem Statement and Objective of current RAC research at NJIT:

• Experimental approach was employed. • 45 Reinforced RAC columns (10x10x32 inches) were tested under axial load (monotonic and cyclic). • Different reinforcement configurations were considered.

• There were several test variables: - steel and unconfined concrete strengths - pattern, size and distribution of the ties

Scope:

Literature Review on

RAC Properties

Mechanical Prop. and Durability of Plain RAC

Beams made of RAC

Models for Confined NAC

Summary of RAC Properties:

General Findings: • The idea of using RAC for structural applications is quite new and the literature is limited.

• Deflection and load capacity were simply compared to normal concrete beams. • Cracking patterns were similar to normal concrete beams.

• Ultimate capacity of RAC beams slightly less than NAC beams

• Deflections at failure of RAC beams are more than NAC beams.

Using RAC as Structural Members:

Confinement :

A constitutive model for normal concrete (Park et al, 1982)

Parabola Sustaining branch

Experimental Setup

Weldon Materials crushing facilities,

New Jersey

0

1

2

3

4

5

0 0.0025 0.005 0.0075 0.01 0.0125Strain

Stre

ss (k

si)

NAC Cylinder #1NAC Cylinder #2

29

0.00

1.00

2.00

3.00

4.00

5.00

3 7 14 21Age (days)

Com

pres

siv

Stre

ngth

(ksi

)

Sample #1Sample #2Sample #3Sample #4Average

Gain in the strength Mixing arrangement

RAC Cylinders

30

Testing machine used for measuring strength of concrete cylinders

0.00

1.00

2.00

3.00

4.00

5.00

0.0000 0.0025 0.0050 0.0075 0.0100Axial Strain

Stre

ss (k

si)

RAC Cylinder #1RAC Cylinder #2RAC Cylinder #3

test terminated

significant damage

Typical stress-strain Curves for plain RAC cylinders

9 possibilities to make columns with different tie configuration and spacing

Tie pattern Tie spacing Sequence number

Column Designations

quasi-static

fast rate

cyclic

Extra End confinement with GFRPs:

Installation of SikaWrap® GFRP sheets on specimen ends

External Instrumentation:

Capping with hydro-stone® gypsum cement

DC Linear Variable Differential Transformers (DCDT)

Internal Instrumentation:

CEA-06-240UZ-120 electrical strain gauge (4 by 9 mm)

0

10

20

30

40

50

60

70

80

0.00 0.01 0.02 0.03Strain

Stre

ss (k

si)

0.41%

Strain gauge still functional after this point

0.2% offset method

Loading Unit:

1000-kip MTS815 loading unit and data acquisition hardware and software

Test Results:

Observations and Discussions

Typical failure

South and East sides North and West sides

South and East sides North and West sides

Effect of Reinforcement Variables:

0

100

200

300

400

500

600

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5Axial Deformation (in)

Axi

al L

oad

(kip

s)

C1-1

B1-1

C2-1

A1-1 B2-1

A3-1 A2-1

B3-1

C3-1

Increase in volumetric ratio

0

100

200

300

400

500

600

0 0.005 0.01 0.015 0.02Axial Strain

Axi

al L

oad

(kip

s)

`̀̀

C3-1 ( =0.70, s=3 in)

C2-1 ( =1.05, s=2 in)

C1-1 ( =2.10, s=1 in)f =4.23 ksi

c

f =4.34 ksic

f =4.45 ksic

Tie Spacing

Effect of Tie Configuration

0

100

200

300

400

500

600

0 0.005 0.01 0.015 0.02Axial Strain

Axi

al L

oad

(kip

s)

`̀̀

B2-1 ( =0.75, s=2 in)

A1-1 ( =0.88, s=1 in)

C3-1 ( =0.70, s=3 in)

f =4.18 ksic

f =4.26 ksic

f =4.45 ksic

Effect of Loading Rate

0

100

200

300

400

500

600

700

0 0.1 0.2 0.3 0.4 0.5

Axial Deformation (in)

Axi

al L

oad

(kip

s)B2-4B2-1

Analytical Prediction of RAC

Stress-Strain Behavior

0

1

2

3

4

5

6

7

8

0.000 0.002 0.004 0.006 0.008Strain

Stre

ss (k

si)

A18 (fc=6.08 ksi)

A18 (predicted)

A13 (fc=5.02 ksi)

A13 (predicted)

A8 (fc=3.61 ksi)

A8 (predicted)

A3 (fc=2.4 ksi)

A3 (predicted)

0

1

2

3

4

5

6

0 0.003 0.006 0.009 0.012Axial Strain

Stre

ss (k

si)

Proposed model for confinedRACMander et al. (1984) model fornormal concreteSheikh and Uzumeri (1978)model for normal concreteProposed model for confinedRACExperimental curves (C2-2)

Examination of RAC models in

Flexure

An extensive experimental program including testing of several plain RAC cylinders as well reinforced RAC columns, 10 inches by 10 inches in section and 32 inches in height, with different tie arrangements was conducted. The following conclusions can be made:

1. RAC has a relatively smaller E than that of NAC (30% to 50% depending on the compressive strength). The higher the strength, the less the difference is;

Conclusions:

2. The strain corresponding to maximum strength of a RAC cylinder is about 0.0025 (0.002 for NAC);

3. When efficiently confined, RAC can exhibit a significant gain in strength (depending on the amount of the lateral reinforcement) and ductility. An “efficient” confinement, however, requires a cage in which the longitudinal and lateral reinforcement are closely joined together;

4. Up to an axial strain about 0.0020 and regardless of the amount of lateral reinforcement, RAC columns behave as if they are plain. At this stage vertical hair cracks appear on the cover;

5. The strain at which the cover spalls off is in a wide range of

0.004 to 0.007, depending on the amount of lateral reinforcement (0.004 and 0.005 is suggested for NAC);

6. Under high straining rates, RAC column show 7% to 26% increase in ultimate axial strength;

7. Well-confined RAC shows excellent ductility and no insignificant degradation of stiffness under cyclic loading;

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