Post on 18-Apr-2018
Ms. Micheli S. GONÇALVES
Ms. Alessandra P. CAVALHEIRO
Dra. Marlova P. KULAKOWSKI
Dr. Claudio S. KAZMIERCZAK
Evaluation of concrete made with
coarse recycled aggregate from
precast concrete
WASCON 2012 Gothenburg, SE
G R A D U A T E P R O G R A M
CIVIL ENGINEERING
Universidade do Vale do Rio dos Sinos – UNISINOS A Jesuit University – South Brazil
GMAT – Research Group in Construction Materials and Recycling
G R A DU A T E P R O G R AM
CIVIL ENGINEERING
Recycled concrete aggregate
(RCA) from concrete waste
Some of the problems
to use RCA is
its higher water
absorption
and its lower specific
mass
Concrete waste has a high potential for use
as recycled aggregate in structural concrete.
0
1
2
3
4
5
6
7
8
9
0 10 20 30 40 50 60 70 80
Wa
ter
ab
so
rpti
on
(%
)
Time (min)
RCA 50 MPa
RCA 37 MPa
RCA 18 MPa
Natural Aggregate
G R A DU A T E P R O G R AM
CIVIL ENGINEERING
Recycled concrete aggregate (RCA)
from concrete waste
The ways to compensate its higher absorption can be
Pre-wetting;
Adding water to concrete mixing water;
Adding water for slump adjustment;
Aggregate saturation.
Others relevant aspects in the use of RCA
The influence of the compressive strength of the concrete which the
RCA is originated;
The quantity employed.
Previous study indicates
Maximum 50% ratio of RCA content
Maximum rate of 50% to compensate RCA water absorption.
WASCON 2012 Gothenburg, SE
G R A DU A T E P R O G R AM
CIVIL ENGINEERING
Aim
Case study
The research project was developed in a
partnership with a precast concrete industry
Porto Alegre – South Brazil;
It was carried out in laboratory;
The results helped to define some
parameters for the use of RCA in
production of precast concrete panel.
WASCON 2012 Gothenburg, SE
The purpose of this study was to investigate the influence
of recycled concrete aggregate from precast concrete
waste on mechanical properties of new concretes.
G R A DU A T E P R O G R AM
CIVIL ENGINEERING
Materials
Binding materials High early strength Portland Cement
15% of Fly Ash as mineral admixture
Superplasticizer Polycarboxylate-type
Fine natural aggregate Quartz river sand
Coarse natural aggregate Crushed basalt
WASCON 2012 Gothenburg, SE
It was employed the same materials used by the partner
industry in the production of precast concrete panels.
from production of slabs;
it is subject to conventional curing;
has 40 MPa;
RCA-C
The waste diagnosis showed that the higher quantity of
continuously generated wastes is originated from two dry-cast
concrete wastes:
from production of piles;
it is subject to steam-curing;
has 45 MPa
RCA-S
It was employed
a jaw crusher RCA was sieved
Selected with size
between
25 and 4.8 mm
RCA Absorption
Characteristics Absorption at 10 min (a)
• corresponds to water
absorption by capillary
suction;
• RCA-S has absorption
50% higher than RCA-C.
Total absorption (b)
• corresponds to water
saturation;
• RCA-S shows an
absorption only
4% higher than RCA-C.
Absorption 10 min (%) Absorption (%)
RCA-C 5,63 10,47
RCA-S 8,37 10,93
0
2
4
6
8
10
12
0 5 10 15 20 25 30 35 40
Wa
ter a
bs
orp
tio
n (%
)
Time (min)
Natural aggregateRCA-Conventional curingRCA-Steam curing
(a) (b)
0,000
0,004
0,008
0,012
0,016
0,0010,1101000
Dis
trib
utio
n o
fIn
tru
sio
nV
olu
me
( cm
3/g
)
Pore diameter (µm )
0,00
0,04
0,08
0,12
0,16
0,0010,1101000Cu
mu
lative
volu
me
intr
ud
ed
( cm
3/g
)
Pore diameter (µm )
RCA-CRCA-S
RCA porosity by Mercury Intrusion Porosimetry – MIP
The total RCA-S pore’s
volume accumulated is
higher than the RCA-C
may justify the biggest
water absorption observed
for RCA-S
RCA-S shows a micro
pore volume higher than
the RCA-C, attesting the
highest absorption by
capillary suction.
0,000
0,004
0,008
0,012
0,016
0,0010,1101000
Dis
trib
utio
n o
fIn
tru
sio
nV
olu
me
( cm
3/g
)
Pore diameter (µm )
0,00
0,04
0,08
0,12
0,16
0,0010,1101000Cu
mu
lative
volu
me
intr
ud
ed
( cm
3/g
)
Pore diameter (µm )
RCA-CRCA-S
G R A DU A T E P R O G R AM
CIVIL ENGINEERING
Recycled concrete aggregates microstructure
WASCON 2012 Gothenburg, SE
characterized by Secondary Electron Microscopy
RCA-C RCA-S
The images seem to confirm the difference in the pore structure among
the types of recycled aggregate, since it is possible to observe a bigger
quantity of pores in RCA-S.
G R A DU A T E P R O G R AM
CIVIL ENGINEERING
Methods
Natural coarse aggregate was replaced
in mass with compensation of volume
WASCON 2012 Gothenburg, SE
Reference concrete
Natural aggregate mortar content = 55%
three mix proportioning
1 : 2,78 : 3,10 - w/b = 0,42
1 : 2,23 : 2,65 - w/b = 0,51
1 : 2,78 : 3,10 - w/b = 0,60
used in industry
production of
precast
concrete panel
Other six mixtures were produced,
employing 50% of recycled aggregate.
with same mix
proportioning
Concrete production
G R A DU A T E P R O G R AM
CIVIL ENGINEERING
Methods
WASCON 2012 Gothenburg, SE
Concrete production
slump of 200 ± 30 mm industrial production
of concrete panel
concrete mixing water →100 ± 20 mm slump
superplasticizer admixture → 200 ± 30 mm
→ Added water to concrete mixing water;
→This method was considered the easiest
on tests carried out in the industry.
→ It was determined using 50% of the water
absorption ratio observed in 10 minutes
To compensate the
highest water
absorption of RCA
G R A DU A T E P R O G R AM
CIVIL ENGINEERING
Methods
Compressive strength test at 7, 28 and 63 days - NBR
5739:2003
Tensile strength test at 28 days - NBR 7222:2011.
Results were statistically treated by analysis of variance
(ANOVA).
WASCON 2012 Gothenburg, SE
Experimental procedures
G R A DU A T E P R O G R AM
CIVIL ENGINEERING
Results
Compressive strength - Analysis of variance (ANOVA)
Factor DFa SQb MQc Fcalc ‘p’ Value Significance
WB 1950,62 2 975,31 98,648 0,000000 S
ABS 969,68 2 484,84 49,039 0,000000 S
AG 1998,58 2 999,29 101,073 0,000000 S
WB*ABS 143,11 4 35,78 3,619 0,011012 S
WB*AG 135,59 4 33,90 3,429 0,014358 S
ABS*AG 138,67 4 34,67 3,506 0,012878 S
WB*ABS*AG 172,76 8 21,60 2,184 0,043128 S
WB = water/binder ratio;
ABS= water absorption of aggregates (%) – represents aggregate type.;
AG=Age (days); a Degrees of freedom; b Sum of squared.; c Squared mean.
All studied factors have a significant
effect on a confidence level α of 95%.
G R A DU A T E P R O G R AM
CIVIL ENGINEERING
Results - Compressive strength
For all ages and
water/binder ratio, the
RCA-C concrete had
the best performance;
Comparing to the
reference concrete it
may be observed that,
in average, RCA-C
showed an increment
on compressive
strength of
27% for 7 days age,
4% for 28 days age,
and
9.5% for 63 days age.
The average results obtained in the compressive strength
test 7, 28 and 63 are
G R A DU A T E P R O G R AM
CIVIL ENGINEERING
It may be consequence to the
steam-curing cycle
of the concrete that originated the
RCA-S.
Compressive strength
compressive strength of
concrete waste
RCA-S > RCA-C
concretes made with RCA
RCA-S < RCA-C
higher RCA-S water absorption at 10 minutes
increase in amount of water to compensate it
might have caused the
less compressive
strength of concrete
with RCA-S
quicker hydration due to steam curing
can result in hydration’ products with a
poorer structure with a
higher capillary pore volume
can be responsible for its higher capillary suction
G R A DU A T E P R O G R AM
CIVIL ENGINEERING
Results - Tensile strength
The average values found for the concretes made with
RCA-C present an increase from 1.6 to 6.7% related to
natural aggregate;
Is similar to the behavior found for the compressive strength.
G R A DU A T E P R O G R AM
CIVIL ENGINEERING
Results
Relationship between compressive strength and tensile
strength
G R A DU A T E P R O G R AM
CIVIL ENGINEERING
Conclusions
As final considerations it can be said:
The lower mechanical strength was observed for RCA-S concrete
and this behavior can be explained by its characteristics;
The micro structure of the recycled aggregate has a significant
influence in the performance of the new concrete, even though,
the recycled aggregate have been originated from concrete with
similar strength levels.
The RCA-C concrete presented compatible strength with ones
returned for the natural coarse aggregate concrete.
Other method to produce concrete with RCA can lead to a better
performance. It is being studied by our research group.
G R A DU A T E P R O G R AM
CIVIL ENGINEERING
Production of pre-cast concrete panel with RCA
Adding RCA Aspect of Concrete with RCA production of precast
concrete with RCA
Panels
finishing of molded panel Cured Panels Prototype construction
with RCA
Concrete Panels
1 2 3
4 5 6
G R A DU A T E P R O G R AM
CIVIL ENGINEERING
Evaluation of concrete made with coarse
recycled aggregate from precast concrete
Acknowledgements
Support for this research was provided by FINEP,
CAPES and CNPq, Brazilian agencies for research
support.
We would like to thank the organization committee of
WASCON 2012.
Contacts marlovak@unisinos.br
claudiok@unisinos.br
Ms. Micheli S. GONÇALVES
Ms. Alessandra P. CAVALHEIRO
Dra. Marlova P. KULAKOWSKI
Dr. Claudio S. KAZMIERCZAK
G R A DU A T E P R O G R AM
CIVIL ENGINEERING
Unisinos’ research in
recycled concrete aggregate
WASCON 2012 Gothenburg, SE
CONCRETE WASTE AS RECYCLING AGGREGATE
Mechanical
properties Durability
Carbonation
Cl- Penetration
From ready mix
concrete plants
From concrete
structure demolition
Generated in
laboratory From precast
concrete industry
ways to compensate the
higher absorption of water Content of RCA
Amount of water to
compensate
higher absorption of water
Concrete Mixing method
Fresh state
properties Water absorption
Slump maintenance Shrinkage
Compressive
strength
Tensile strength
Elasticity modulus
This work is part of a research on recycling concrete waste as aggregate:
G R A DU A T E P R O G R AM
CIVIL ENGINEERING
Identification Absorption 10 min (%) Absorption (%) Bulk density (kg/m³) Specific gravity (kg/m³)
RCA-C 5,63 10,47 2330 1070
RCA-S 8,37 10,93 2370 1160
RCA characteristics
A compensation of volume due to differences in specific mass was done,
according to Equation 1.
MRCA = mass of recycled concrete aggregate (kg);
MNA = mass of natural aggregate (kg);
γNA = specific gravity of natural aggregate;
γRCA = specific gravity of recycled concrete aggregate.
RCA
NA
NARCA
MM
Fine natural aggregate Quartz river sand
Bulk density = 1530 kg/m³
Specific gravity = 2550 kg/m³
Fineness = 2,73
Maximum size = 4.8 mm
Coarse natural aggregate Crushed basalt
Bulk density = 1570 kg/m³
Specific gravity = 2400 kg/m³
Fineness = 7,50
Maximum size = 19 mm
G R A DU A T E P R O G R AM
CIVIL ENGINEERING
The additional water was determined using 50% of the water absorption
ratio observed in 10 minutes (Eq 2);
MCW = mass of additional water (kg);
AW10 = water absorption in 10 minutes (%);
MRCA = mass of recycled concrete aggregate (kg).
RCAW
CW MA
M 100
50 10.