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Experimental and Numerical Techniques to Characterize Structural Properties of Fresh
ConcreteConcrete
Tony Di Carlo, PhD candidate
Anders Carlson, S.E., Ph.D.
Behrokh Khoshnevis, Ph.D.
University of Southern California
Daniel J. Epstein Department of Industrial and Systems Engineering
Overview
• Contour Crafting• Properties of Fresh Concrete• Experimental Techniques• Experimental Techniques• Numerical Techniques• Fresh Concrete Stacking Regimens• Fresh Concrete Stacking Test• Opportunities for Research
Experimental and Numerical Techniques to Characterize Structural Properties of Fresh Concrete 2May 30, 2012
Contour Crafting - Intro
• Computer-controlled layering of cementitious materials
• A special mixture of extrudable mortar• Successive layers accrete from the bottom up• Successive layers accrete from the bottom up• Process is formless; fresh mortar is shape stable• Green strength to match substantial and unprecedented fabrication loads
May 30, 2012 Experimental and Numerical Techniques to Characterize Structural Properties of Fresh Concrete 3
A prototypical structure and its fabrication tool path
(Zhang 2009)
Contour Crafting - Motivation
• Reduce the time and cost of fabrication• Automation → affordable high quality dwellings• Material savings (less waste and formwork)• Material savings (less waste and formwork)• Less labor, fewer construction-related injuries• More design freedom
May 30, 2012 Experimental and Numerical Techniques to Characterize Structural Properties of Fresh Concrete 4
Contour Crafting - Evolution
Un
cure
d C
era
mic
Ma
teri
als
(K
wo
n 2
00
2)
RapidSet Cement AllUltimax
Cement 35.3%Sand 40.6%Bentonite 2.5%
Water 21.6%(% by weight)
SikaRepairM
elt
ed
Po
lyst
yre
ne
(R
uss
ell
19
99
)
Un
cure
d C
era
mic
Ma
teri
als
(K
wo
n 2
00
2)
Co
ncr
ete
wit
h C
lay
VM
A (
Hw
an
g 2
00
5)
Plasterand Clay
Ultimax
May 30, 2012 Experimental and Numerical Techniques to Characterize Structural Properties of Fresh Concrete 5
Me
lte
d P
oly
sty
ren
e (
Ru
sse
ll 1
99
9)
Un
cure
d C
era
mic
Ma
teri
als
(K
wo
n 2
00
2)
Co
ncr
ete
wit
h C
lay
VM
A (
Hw
an
g 2
00
5)
'99 '00 '01 '02 '03 '04 '05 '06 '07 '08 '09 '10'98
Contour Crafting in Action
May 30, 2012 Experimental and Numerical Techniques to Characterize Structural Properties of Fresh Concrete 6
Contour Crafting – Fabrication Scenario
• Goal: a house in a day• Mortar stacking rate...
H
H=96” (8 feet)h=3”
n=94/3=32t= 8 hrs = 480 min
May 30, 2012 Experimental and Numerical Techniques to Characterize Structural Properties of Fresh Concrete 7
h
t= 8 hrs = 480 min
n/t = 32/480 n/t = 1 road / 15 min
Mix Design ↔ Stacking Regimen
Lightweight
Early Strength
Workability
ClayFly AshExpanded Glass
May 30, 2012 Experimental and Numerical Techniques to Characterize Structural Properties of Fresh Concrete 8
Internal curing (Green) Shape Stability
Properties of Fresh Concrete
Development of Compressive Strength of Extruded Cement
May 30, 2012 Experimental and Numerical Techniques to Characterize Structural Properties of Fresh Concrete 9
Development of Compressive Strength of Extruded Cement
Mortars (Voigt 2005)“at birth”† structural
properties of concrete
† credit: Mario Ucci
After Carino (2001) and Freiesleben (1985) the gradual strength development
during setting can be modeled with an exponential function:
y =Cemt
Experiments with Fresh Concrete
Bin to hold sand used to charge the
loading device.
Dummy specimen used to zero
extensometer.
6 in.x12 in. cylinder guided laterally and suspended by springs. The
cylinder collects sand flowing in at a constant rate from above. This charge stretches the suspension
system, and is considerably larger than the resistance exerted by the
compressed fresh mortar specimen - this disparity assures nearly constant axial strain rate.
Ram used to extrude
May 30, 2012 Experimental and Numerical Techniques to Characterize Structural Properties of Fresh Concrete 10
Digital weighing platform to measure
applied force.
Extensometer to measure slump and
axial deflection. Vibration table used to consolidate test specimens inside extrudable
cylindrical mold.
Ram used to extrude test specimens.
Stacking Strength
May 30, 2012 Experimental and Numerical Techniques to Characterize Structural Properties of Fresh Concrete 11
Stacking Regimen
May 30, 2012 Experimental and Numerical Techniques to Characterize Structural Properties of Fresh Concrete 12
0.0
10.0
20.0
0 100 200 300
Exponential Growth
F = Cemt
Time After Mixing [min.]
Ma
xim
um
Fo
rce
[l
bf]
Stacking Simulation
May 30, 2012 Experimental and Numerical Techniques to Characterize Structural Properties of Fresh Concrete 13
Numerical Methods for Fresh Concrete
Analysis of Fabrication
Scenarios, and In-Situ Health
Monitoring
Modulus
[psi]
Poisson’s
ratio, ν
Angle of
Friction
Initial Hydrostatic
Tension Strength
Dilation
Angle
Yield Stress
[psi]
May 30, 2012 Experimental and Numerical Techniques to Characterize Structural Properties of Fresh Concrete 14
[psi] ratio, ν Friction Tension Strength Angle [psi]
5 0.2 45 0.2 45 0.3
Typical Drucker-Prager parameters for a Contour-Craftable
mortar 30 minutes after mixing
Research Opportunities
• Varying temperatures • Varying moisture contents
• Analysis of creep• Analysis of autgeneous shrinkage cracking of the
monolithic structure• Optimize grading (including large aggregate) improve
shape stability and green strength• …
May 30, 2012 Experimental and Numerical Techniques to Characterize Structural Properties of Fresh Concrete 15
• …
Thank You for you Kind AttentionThank You for you Kind Attention
www.contourcrafting.org
Experimental and Numerical Techniques to Characterize Structural Properties of Fresh Concrete 16May 30, 2012
Maison en Pise’ (Rammed Earth)
May 30, 2012 Experimental and Numerical Techniques to Characterize Structural Properties of Fresh Concrete 17
Ref. 1: « traité de construction en terre » CRATerre ed parenthèses, 1995, p. 207)
Ref. 2: « Architecture et Terre en SYRIE , une tradition de onze Millénaires » par Mahmoud BENDAKIR ed CRAterre. 2008.
Green Strength Test - Results
4.0
4.5
5.0
Dia
l Tur
ns (
1 re
volu
tion
= 0
.1 in
ches
)
5
6
0:060:11
Time AfterMixing
[hh:mm]
1.0
1.5
2.0
2.5
3.0
3.5
4.0
Dia
l Tur
ns (
1 re
volu
tion
= 0
.1 in
ches
)
2
3
4
For
ce [l
bf]
0:110:180:220:260:310:470:520:581:041:131:241:32
May 30, 2012 Experimental and Numerical Techniques to Characterize Structural Properties of Fresh Concrete 18
Unconfined Compressive Strength of a Contour-Craftable Mortar
0.0
0.5
1.0
1.00 3.00 5.00
Raw Scale Reading [lb]
0
1
0.00 0.05
Strain [%]
1:321:391:491:543:283:314:434:48