Mechanical Performance of Self Consolidating Concrete M. D.

Mechanical Performance of Self Consolidating Concrete M. D.

Mechanical Performance of Self Consolidating Concrete
M. D. D'Ambrosia, D. A. Lange , A. J. Brinks
University of Illinois at Urbana-Champaign

OBJECTIVE

EXPERIMENTS

Determine how SCC strategies
high paste content
VMA (thickeners)
smaller aggregate & controlled gradation
HRWR, SP (CAE)
Mineral fillers & additives

Strain ()

Restrained

0

6

-50

5

Cumulative
Shrinkage + Creep

-100

4
3

-200

2

Free Shrinkage

Load

-250

1

-300

0
0

Slump flow of SCC mixtures was

strain virtually constant over time (to
within 0.005mm )
Summation of restrained deformation
allows for creep calculation

specimens was measured from time
of casting
Internal relative humidity in sealed
prism was also measured to asses
the driving force for autogenous
shrinkage

AUTOGENOUS SHRINKAGE AND TOTAL
SHRINKAGE DURING DRYING
0

8000
6000

OPC1, w/c = 0.40
SCC1, w/c = 0.39

4000

SCC1, w/c = 0.39

1000

SCC3, w/c = 0.41
SCC4, w/c = 0.34

800
600
400

SCC2, w/c = 0.33
SCC3, w/c = 0.41

-100
-200

-50

-100

OPC1, w/c = 0.40

-150

SCC1, w/c = 0.39

10

20

30

40

50

0

60

2

4

6

8

-600

OPC1, w/c = 0.40

-700

SCC1, w/c = 0.39

-800

SCC3, w/c = 0.41

SCC2, w/c = 0.33

-1000
0

10

5

10

Age (days)

Concrete Age (Days)

-500

-900

-200

0

-400

SCC4, w/c = 0.34

SCC3, w/c = 0.41

0

-300

SCC2, w/c = 0.33

200

SCC4, w/c = 0.34

0

Free Shrinkage (x10-6)

10000

7

0

1200

2000

2.0

6

system applies a restraining force
with servo hydraulic actuator
Instron Controller operated by a
Restraint Simulation Program
(RSP) (LabView)

SCC2, w/c = 0.33

2.5

5

Autogenous shrinkage of sealed

OPC1, w/c = 0.40

12000

SCC proportions differ from ordinary concrete

3
4
Time (days)

Restraint Simulation Program keeps

Autogenous Shrinkage (10-6 m/m)

Graded
Aggregate

2

1400

14000

Tensile Strength (psi)

High Paste

measure deformation
Sealed barrier of aluminum foil applied
to impose symmetric drying

1

Feedback controlled closed loop

EARLY AGE COMPRESSIVE AND TENSILE
STRENGTH DEVELOPMENT

Compressive Strength (psi)

Average w/cm = 0.41, w/p = 0.35
33% contain limestone powder (LSP)
52% contain fly ash, 37% contain slag
30% contain slag and fly ash
0% contain both LSP and pozzolans
45% contain VMA
1% contain both VMA and LSP
Only 3% contain 3 different size
aggregates

Drying began at concrete age of 1 day
Environment was 50% RH and 23C
An LVDT extensometer was used to

measured for quality control
A separate rheological study
was conducted (L. Shen, L.
Struble, J. Hidalgo)

UIUC SCC DATABASE

15

20

25

0

30

5

Age (d)

10

15
Age (days)

20

25

SCC Database

SCC mixtures tend to have low w/c ratio and high paste%, and thus higher strength than most

Low w/c drives autogenous shrinkage, which can then be a major contributor to total shrinkage

Mixtures studied

ordinary concrete. When compared to OPC with same w/c and paste%, strength is similar,
indicating that SCC admixtures had little effect of strength

at early age. High early age shrinkage leads to tensile stress and cracking when concrete is
restrained

1.5

30

SCC1
SCC2

SCC3

RESTRAINED STRESS DEVELOPMENT, STRESS STRENGTH RATIO AND
RELAXATION BY TENSILE CREEP

Typical non-SCC
materials, according to
ACI mixture
proportioning method

SCC4

0.5

OPC1

0.0
50%

55%

60%

65%

70%

75%

80%

85%

90%

95%

100%

Selected control mixtures from literature explore
various strategies of SCC mixture proportioning
SG
Cement (Type I)
Fly Ash (Class C)
Coarse Aggregate, 3/4" (20mm)

3.15

2.65

2.70

Unit

OPC1

SCC1

SCC2

SCC3

SCC4

3

lb/yd

726

661

601

685

679

kg/m3

431

392

357

407

403

lb/yd3

0

157

325

0

151

kg/m3

0

93

193

0

90

1853

367

1365

1627

579

3

lb/yd

1099

218

810

965

343

3

lb/yd

0

1075

0

0

1018

kg/m3

0

638

0

0

604

lb/yd3

1192

1403

1336

1389

1389

kg/m3

707

832

792

824

824

lb/yd3

290

311

301

278

267

3

172

185

179

165

158

fl oz/yd3

22

63

29

49

36

l/m3

0.84

2.44

1.12

1.89

1.38

kg/m3

Coarse Aggregate, 3/8" (10mm)
Fine Aggregate (FM = 2.57)
Water

2.70

2.64

1.00

kg/m

Superplasticizer (CAE)
VMA

1.06

1.00

fl oz/yd
l/m

Paste content by Volume

Air Content
w/cm

0.84

3

32%

37%

40%

33%

34%

0.64

0.97

0.98

0.85

0.87

in

5

30

28

26

27

mm

100

750

700

650

700

%

2.5%

1.0%

2.5%

3.5%

3.0%

0.40

0.38

0.33

0.41

0.32

%

FA/CA ratio
Slump flow (standard slump for OPC1)

22

3

Shrinkage Stress (psi)

Aggregate Content (%)

450

1.0

400

0.9

350

0.8

300
250
200
OPC1, w/c = 0.40

150

SCC1, w/c = 0.39

100
50

0.7
0.6
0.5
0.4
OPC1, w/c = 0.40

0.3

SCC1, w/c = 0.39

0.2

SCC3, w/c = 0.41

SCC4, w/c = 0.34

0.1

SCC4, w/c = 0.34

2

4

6
Age (days)

8

10

0.4

0.3

0.2
OPC1, w/c = 0.40
SCC1, w/c = 0.39

0.1

SCC3, w/c = 0.41
SCC4, w/c = 0.34

0.0

0.0
0

An investigation of the EA mechanical

0.5

SCC3, w/c = 0.41

0

SUMMARY

0.6

Specific Creep (x10-6 m/m/psi)

1.0

Stress-Strength Ratio

FA/CA Ratio

7

-150

early age cracking
long term durability
surface scaling
freeze-thaw resistance
abrasion resistance

Mineral
Fillers

8

Load (kN)

50

segregation
shrinkage and creep
entrained air system
permeability
strength

VMA

9

Creep

Free Specimen

100

and affect performance.

Restrained Specimen

150

change hardened properties

10

Applied Load (kN)

200

0

2

4

6
Age (d)

8

10

0

2

4

6

8

10

Age (days)

Stress measurements indicate that to reduce the risk of early age cracking in SCC, using a w/cm ratio of 0.40 to 0.42 can prevent autogenous
shrinkage from causing significant stress, while at the same time minimizing drying shrinkage.
Stress-strength ratios demonstrate that microcracking and damage may be occurring as early as one or two days after drying at early age.
Creep capacity is directly proportional to paste content and is inversely proportional to w/cm ratio. The high stress-strength ratio of SCC1
induced microcracking damage High cracking risk
In SCC4 the stress develops rapidly due to the lack of relaxation by creep and damage occurs rapidly right before failure Also high cracking risk

behavior of SCC has revealed a potentially
high risk for cracking in some mixtures
Mechanical properties can be influenced
by higher paste content and low w/c, BUT
it is best not to treat SCC as a group of
materials with similar mechanical behavior.
Autogenous shrinkage may cause
significant stress at early age
SCC Mix Design should minimize cement
paste content and use a w/cm that avoids
significant autogenous shrinkage while
achieving necessary flow characteristics
Providing external water during curing in
field applications will delay shrinkage
stress development at early age and
reduce the overall magnitude of shrinkage
and cracking risk.

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