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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