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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 GRADUATE PROGRAM CIVIL ENGINEERING Universidade do Vale do Rio dos Sinos – UNISINOS A Jesuit University – South Brazil GMAT – Research Group in Construction Materials and Recycling
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Page 1: Evaluation of concrete made with coarse recycled aggregate ...

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

Page 2: Evaluation of concrete made with coarse recycled aggregate ...

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

Page 3: Evaluation of concrete made with coarse recycled 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

Page 4: Evaluation of concrete made with coarse recycled aggregate ...

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.

Page 5: Evaluation of concrete made with coarse recycled aggregate ...

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.

Page 6: Evaluation of concrete made with coarse recycled aggregate ...

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

Page 7: Evaluation of concrete made with coarse recycled aggregate ...

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)

Page 8: Evaluation of concrete made with coarse recycled aggregate ...

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

Page 9: Evaluation of concrete made with coarse recycled aggregate ...

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.

Page 10: Evaluation of concrete made with coarse recycled aggregate ...

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

Page 11: Evaluation of concrete made with coarse recycled aggregate ...

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

Page 12: Evaluation of concrete made with coarse recycled aggregate ...

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

Page 13: Evaluation of concrete made with coarse recycled aggregate ...

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%.

Page 14: Evaluation of concrete made with coarse recycled aggregate ...

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

Page 15: Evaluation of concrete made with coarse recycled aggregate ...

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

Page 16: Evaluation of concrete made with coarse recycled aggregate ...

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.

Page 17: Evaluation of concrete made with coarse recycled aggregate ...

G R A DU A T E P R O G R AM

CIVIL ENGINEERING

Results

Relationship between compressive strength and tensile

strength

Page 18: Evaluation of concrete made with coarse recycled aggregate ...

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.

Page 19: Evaluation of concrete made with coarse recycled aggregate ...

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

Page 20: Evaluation of concrete made with coarse recycled aggregate ...

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 [email protected]

[email protected]

Ms. Micheli S. GONÇALVES

Ms. Alessandra P. CAVALHEIRO

Dra. Marlova P. KULAKOWSKI

Dr. Claudio S. KAZMIERCZAK

Page 21: Evaluation of concrete made with coarse recycled aggregate ...

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:

Page 22: Evaluation of concrete made with coarse recycled 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

Page 23: Evaluation of concrete made with coarse recycled aggregate ...

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.


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