This document summarizes the results of a study on the shrinkage behavior of ultra high performance concrete (UHPC) at the manufacturing stage. Key findings include: 1) UHPC experiences significant autogenous and drying shrinkage that can lead to cracking without proper measures. 2) Mix designs and material properties tested included water-to-binder ratio, cement content, silica fume, and steel fibers. 3) Tests measured mechanical properties, setting behavior, autogenous shrinkage, free shrinkage under different exposure conditions, and restrained shrinkage using a ring test setup. 4) Results showed the combined use of a shrinkage reducing agent and expansive admixture reduced free and rest

1. Shrinkage Behavior of Ultra High Performance
Concrete at the Manufacturing Stage
Sungwook KIM

2. 2
Introduction
Mix Proportion & Material Properties
Test Results
On Going Study
CONTENT
Conclusion

3. 3
1. Introduction (Problems)
Shrinkage
cracking
Typical Shrinkage Strains of UHPC
Edge
Steel reinforcementAutogenous shrinkage
Drying shrinkage
“Highly vulnerable to premature shrinkage cracking”

4. 4
Stress
Time
Elastic stress generated
by shrinkage only
(σ=EC·εsh)
Delay in cracking
Age of cracking
Creep relaxation
Residual stress
regarding stress
relaxation
Material
strength
※ What are the influencing factors for shrinkage cracking?
“Influencing factors”
“by J. Weiss, 1999”
• Strength test
• Setting test
• Ring-test
• Free shrinkage testTensile
creep
Shrinkage
rate
Tensile
strength
Shrinkage
potential

5. 5
2. Mix Proportions and Material Properties
Nomenclature W/B Cement
Silica Fume
(SF)
Filler Sand
Superplasticizer
(SP)
SRA* EA** Steel
fiber
Mix. A
0.2 1.0 0.25 0.3 1.1 0.012
- -
Vf=2%
Mix. B 0.01 0.075
* : Shrinkage reducing agent
** : Expansive admixture
Type of fiber
Density
(kg/cm3)
Tensile strength
(MPa)
Length of fiber
(mm)
Aspect ratio
(mm/mm)
Straight type 7.8 2,500 13 65
Composition %
(mass)
CaO Al2O3 SiO2 Fe2O3 MgO SO3 K2O F-CaO
Specific surface
(cm2/g)
Density
(g/cm3)
Cement 61.33 6.40 21.01 3.12 3.02 2.30 - - 3,413 3.15
Silica fume (SF) 0.38 0.25 96.00 0.12 0.10 - - - 200,000 2.10
EA 13.55 18.66 3.80 - - 51.35 0.56 16.02 3,117 2.98
Chemical Compositions of Materials
Properties of Steel Fiber
Mix Proportions (ratio in weight)
Relative Humidity & Temp.
Relative
Humidity (RH)
Temperature
(℃)
60±5% 23±1℃

6. 6
Compressive strength Flexural tensile strength Secant elastic modulus








tb
a
f
fc
exp
28
Mixture
Flow
(mm)
Compressive strength
(MPa)
Flexural tensile strength
(MPa)
Secant elastic modulus
(GPa)
1day 3days 7days 28days 1day 3days 7days 28days 1day 3days 7days 28days
Mix. A 235 78.8 105.6 126.2 152.4 26.3 28.7 33.8 34.1 28.2 40.3 41.2 43.3
Mix. B 240 70.7 98.7 127.3 152.2 24.1 25.1 32.5 33.4 30.9 41.1 44.6 46.0








tb
a
f
f ft
exp
28








tb
a
E
E
c
c
exp
28
Mixture a b R2
Mix. A 0.971 -0.271 0.9842
Mix. B 1.162 -0.326 0.9862
Mixture a b R2
Mix. A 0.303 -0.058 0.9916
Mix. B 0.456 -0.101 0.9732
Mixture a b R2
Mix. A 0.389 0.001 0.9948
Mix. B 0.381 0.001 0.9986
3. Test Results (Mechanical Properties)

7. 7
3. Test Results (Setting properties)
Setting properties of UHPC (ASTM C 403)
)(Log)(Log tabPR 
where, PR=penetration resistance (psi)
t=elapsed time (min)
(1)
Mixture a b R2 Initial Setting (hr) Final Setting (hr)
Mix. A 5.1483 11.0284 0.99507 11.0 13.5
Mix. B 8.3353 20.6517 0.99519 7.5 11.5
※I.S.: PR=3.5MPa, F.S.: PR=28MPa
Initial setting
Final setting
● Mix.A
◆ Mix.B

8. 8
Relationship between Autogenous shrinkage and Setting time
3. Test Results (Autogenous Shrinkage)
Embedded
Strain
gage
Thermocouple
)()()( ttt plastictotalauto  
where, εauto(t) = autogenous shrinkage (με)
εtotal(t) = total shrinkage except drying shrinkage (με)
εtotal(t) = plastic shrinkage (με)
(2)
Plastic
Shrinkage
Reduction

9. 9
Free shrinkage with different exposed surface-to-volume ratios (S/Vs)
3. Test Results (Free Shrinkage)
Combined effect of SRA and EA
S/V=0.0132
S/V=0.0286
550mm
152mm 152mm246mm
35mm
Sealing SealingExposed concrete
Sealing SealingExposed concrete
550mm
165mm 220mm 165mm
76mm
550mm
152mm 152mm246mm
35mm
Sealing SealingExposed concrete
Sealing SealingExposed concrete
550mm
165mm 220mm 165mm
76mm
Embedded
Strain
gage
Thermocouple
≈ 40~44%
“by H. T. See, 2003”
Volume
expansion

10. 10
Inner steel ring
Outer ringWooden base
Inner steel ring
Outer ringWooden base
Teflon sheet
Inner steel ring
Outer ringWooden base
Teflon sheet
Strain gages
Thermocouple
Inner steel ring
Outer ringWooden base
Teflon sheet
Strain gages
Thermocouple
Inner steel ring
“Data Logger system”
3. Test Results (Test procedure: Ring-test (AASHTO PP34-98))

11. 11
3. Test Results (Ring-test)
tCtt mst   )()(
where, εst(t) = actual steel strain by shrinkage of concrete (με)
εm(t) = measured steel strain (με)
C = coefficient of thermal expansion of steel ring (16με/℃)
Δt = time (hours)
“Coefficient
of Thermal
Expansion
=16με/℃”
Temperature compensation of inner steel ring
(3)
Strain gage
Thermocouple

12. 12
Average strains of inner steel ring
3. Test Results (Ring-test)
A R1-
• Type of Mixture
A: Mix. A
B: Mix. B
• Thickness of concrete ring
R1:35mm
R2:76mm
“Mix. A” “Mix. B”
267mm
305mm
R1=375mm or R2=457mm
Silicon
sealing
Steel gage
Concrete
Steel ring
Drying direction
152mm
34%
48%

13. 13
0
5
10
15
20
25
30
35
40
0 4 8 12 16 20 24 28
Stess(MPa)
Age (day)
Mix.A Mix.B
계열7 계열8
Mix. A Mix. B
Relaxed stresses
stst
os
isos
i E
r
rr
P 2
22
2
)( 
 stst
icoc
ocic
os
isos
t E
rr
rr
r
rr

)(
)(
2
)(
22
22
2
22
max



Calculated maximum pressures and tensile stresses
Maximum interface pressures
by Eq. (4)
Maximum residual tensile stresses
by Eq. (5)
(4) (5)
3. Test Results (Restrained Shrinkage Behaviors)
Stresses generated
by shrinkage only
(σ=EC·εsh)
Residual stresses
considering stress
relaxation

14. 14
3. Test Results (Restrained Shrinkage Behaviors)
Tensile creep strains of UHPC with time dependent restrained forces
Tensile creep strains of UHPC
under restrained condition
Tensile creep strains-to-free shrinkage ratio
of UHPC under restrained condition
≈ 39%
≈ 0.46

15. 15
4. On Going Study (Tensile Test at very early Age)
Carrying out tensile test within 1 days after mixing
Strain of steel ring occurs
before initial setting time
Tensile tests are carrying in order to
estimate crack at very early age
“by Dao, 2009”

16. 16
4. Concluding Remarks
1
2
3
4
Ring tests also verified the possibility to compute the confining
tensile stress and strain according to the shrinkage of UHPC at
very early age
Further studies will investigate solutions enabling to get tensile
strength at very early age and simulate the cross-sectional
stiffness and restraint of the form, and verify these solutions
experimentally
This study investigated experimentally the shrinkage behavior
and the corresponding stresses in UHPC for the control of cracks
due to the restraint of forms at early age
Free shrinkage and restrained steel strains were reduced in terms of
the shrinkage reducing effect of EA and SRA

17. 17
Thank you for
your attention