Seminario Internacional de Buenas Prácticas y Mejoramiento del Desempeño de Hormigones para Pavimentos

2. Internal Curing Concrete
Dr Peter Taylor
With thanks to:
John Ries, ESCSI
Dale Bentz, NIST
Jason Weiss, Oregon State

3. Internal Curing - Why
• Curing is:
• Provision of moisture and temperature to allow hydration and
minimize dimensional change
• Keep it wet
• Keep it warm
• Start early
stay late

4. • Without curing we will increase risk of
• Cracking
• Scaling
• A soft surface
• What about strength?
Internal Curing - Why

5. Internal Curing - Why
Time
Property
Continuous cure
Curing stops
Elevated temperature curing

6. Water
Unhydrated
cement
Capillary
pores
HCP
W/C = 0.40 W/C = 0.75 W/C = 0.25

7. Internal Curing - Why

8. Internal Curing - Why

9. • Material should
• Hold sufficient water
• Hold the water until needed and not effect w/c
• Give up water at high RH (desorption)
• Not adversely effect
the concrete quality
Internal Curing - How

10. Internal Curing - How
• Lightweight fine aggregate

11. Internal Curing - How
• Super Absorbent Polymers

12. Internal Curing - How
• Desorption
Castro 2011

13. Water Moving From Aggregate
Detector
X-ray Source
Cement Paste
LWA
Water Can Move ~2 mm after some time
Schlitter (2010)

14. Internal Curing - How
• It’s All About the Distribution
Coarse LWA Fine LWA
Henkensiefken (2008)

15. How Much?
LWA
f
LWA
S
CSC
M
φ
α
*
** max
=where
MLWA = mass of (dry) LWA needed per unit volume of concrete (kg/m3
or lb/yd3);
Cf = cement factor (content) for concrete mixture (kg/m3 or lb/yd3);
CS = chemical shrinkage of cement (mass of water/mass of cement);
αmax = maximum expected degree of hydration of cement (0 to 1);
For ordinary Portland cement, the maximum expected degree of
hydration of cement can be assumed to be 1 for w/c ≥0.36 and to
be given by [(w/c)/0.36] for w/c < 0.36.
S = degree of saturation of aggregate (0 to 1);
ΦLWA = desorption of lightweight aggregate from saturation down to
93 % RH (mass water/mass dry LWA).
Bentz & Snyder (1999), Bentz, Lura, & Roberts (2005):
𝑀𝑀𝐿𝐿𝐿𝐿𝐿𝐿 =
𝐶𝐶𝑓𝑓 ∗ 𝐶𝐶𝐶𝐶 ∗ α𝑚𝑚𝑚𝑚𝑚𝑚
𝑆𝑆 ∗ 𝝓𝝓𝐿𝐿𝐿𝐿𝐿𝐿
Or… about 7lb IC water for 100 lb cement

16. Simple IC Mixture Design
• Need 7 lbs of IC water per 100 lbs of cementitious
• 600 lbs cementitious = 42 lbs of IC water
• Assume 18% LWA absorption in the field
• Assume LWA at 55 lbs/cf
• 55 x .18 = 9.9 lb/cf water at 90% desorption 8.9
• Need 42 lbs IC water / 8.9 = 4.7 cf of LWA
• 4.7 cf x 55 lb/cf = 259 lbs of LWA aggregate

17. NY State DOT Specifications
• Proper amount of water
• 30% replacement of fine aggregate
• Minimum 15% absorbed
moisture
• Place under sprinkler
for minimum of 48 hours
• Allow stockpiles to drain
for 12 to 15 hours
immediately prior to use

18. Internal Curing - How
• Can we do without this?
• Nope
• Still have to keep the surface hydrating
• That’s where the abuse happens

19. Internal Curing - So What
• Benefits
• Better hydration & SCM reaction
• Improved durability
• Less cement
• Less shrinkage, warping, cracking
• Extended service life
• Improved economics
• Increased
sustainability

20. Internal Curing - So What
• More Hydration
Espinoza-Hajazin (2010)

21. Internal Curing – So What
• Less Shrinkage

22. Internal Curing – So What
• Less Shrinkage = Less Cracking
Schlitter (2010)

23. Internal Curing – So What
• Less Shrinkage = Less Warping

24. Internal Curing – So What
• Lower Absorption
Henkensiefken (2009)

25. Internal Curing – So What
• Reduced Conductivity

26. Internal Curing – So What
• Service Life Prediction
Cusson (2010)

27. Internal Curing – So What
• Initial & Life Cycle Cost
Cusson (2010)

28. • Three span bridge at Pine Creek
• One half conventional (both lanes)
• Other half using Internal Curing Concrete
• About 20% (by mass) of fine aggregate replaced with light
weight aggregate
• Other mix proportions
unchanged
Buchanan County

29. Construction
Looking West – IC placed first

30. Construction

31. Potential Benefits to Pavements
• Higher strength
• Thinner slabs (?)
• Less curling
• Bigger panels
• Better resistance to salts
• Cheaper maintenance

32. • Fundamental concept makes sense
• Lab data is promising
• Field data looking good
Closing

33. Fibers
Dr Peter Taylor
With thanks to:
PCA
Kaiser, GCP
Rupnow / Kevern

34. Types of Fibers
• Steel
• Glass
• Synthetic
• Natural
PCA

35. Critical Properties
• Stiffness
• Bond
• Strength
• Size
• Durability
PCA

36. Effects of Different Fibers on
Concrete Properties
Effect Type of Fiber
Reduced plastic
shrinkage cracking
Synthetic,
Steel
Increased tensile
strength
Glass,
Steel,
Carbon
Increased flexural
strength
Steel,
Glass
PCA

37. Properties of Steel Fibers
Relative
density
Diameter,
µm
(0.001 in.)
Tensile
strength,
MPa (ksi)
Modulus of
elasticity,
MPa (ksi)
Strain at
failure, %
7.80 100-1000 500-2600 210,000 0.5-3.5
(4-40) (70-380) (30,000)
PCA

38. Properties of Glass Fibers
Glass
fiber
type
Relative
density
Diameter,
µm
(0.001 in.)
Tensile
strength,
MPa (ksi)
Modulus of
elasticity,
MPa (ksi)
Strain at
failure,
%
E 2.54 8-15 2000-4000 72,000 3.0-4.8
(0.3-0.6) (290-580) (10,400)
AR 2.70 12-20 1500-3700 80,000 2.5-3.6
(0.5-0.8) (220-540) (11,600)
PCA

39. Properties of Synthetic Fibers
Synthetic
fiber type
Relative
density
Diameter,
0.001 in.
Tensile
strength, ksi
Modulus of
elasticity, ksi
Strain at
failure, %
Acrylic 1.18 0.2-0.7 30-145 2,500-2,800 28-50
Aramid 1.44 0.4-0.47 300-450 9,000-17,000 2-3.5
Carbon 1.90 0.3-0.35 260-380 33,400-55,100 0.5-1.5
Nylon 1.14 0.9 140 750 20
Polyester 1.38 0.4-3.0 40-170 1,500-2,500 10-50
Poly-
ethylene
0.96 1-40 11-85 725 12-100
Poly-
propylene
0.90 0.8-8 65-100 500-750 6-15
PCA

40. Properties of Natural Fibers
Natural
fiber
type
Relative
density
Diameter,
µm
(0.001 in.)
Tensile
strength,
MPa (ksi)
Modulus of
elasticity,
MPa (ksi)
Strain at
failure,
%
Wood
cellulose
1.50
25-125
(1-5)
350-2000
(51-290)
10,000-40,000
(1,500-5,800)
Sisal
280-600
(40-85)
13,000-25,000
(1,900-3,800)
3.5
Coconut 1.12-1.15
100-400
(4-16)
120-200
(17-29)
19,000-25,000
(2,800-3,800)
10-25
Bamboo 1.50
50-400
(2-16)
350-500
(51-73)
33,000-40,000
(4,800-5,800)
Jute 1.02-1.04
100-200
(4-8)
250-350
(36-51)
25,000-32,000
(3,800-4,600)
1.5-1.9
Elephant
grass
425 180 (17)
4,900
(26)
4,900
(710)
3.6
PCA

41. Mechanism
• Internal reinforcement
• Crack stopping
Kaiser

42. “Micro” vs. “Macro” Fibers
• Micro (Low Volume Addition) Fibers
• Diameters < 0.004” (0.1 mm)
• Polypropylene, Nylon, Carbon, Cellulose
• 0.03 – 0.1% volume (0.5-1.5#/cy)
• Mainly control plastic shrinkage cracking
• Macro (High Volume Addition) Fibers
• Diameters: 0.008 – 0.03” (0.2 – 0.8 mm)
• Synthetic, Steel 0.2 – 1.0% volume [3 - 15#/cy (Synthetic) or 20-
100#/cy (Steel)]
• Improve concrete material characteristics
• Flexural toughness, Impact resistance,
Fatigue resistance
• NOT STRUCTURAL
“Micro” Fibers
“Macro” FibersKaiser

43. Testing
• ASTM C1609-10 (Synthetic Macro Fibers)
• ASTM C820 (Steel Macro Fibers)
• ASTM C1399-11
• ASTM C1550-10 (Round Determinate Panel)
Kaiser

44. Third Point Loading Test
(ASTM C 1609-10)
• Closed Loop System
• Sample Size: 6” x 6” x 20” (150mm x 150mm x 500mm)
Kaiser

45. Australian Round Determinate Panel Test
(ASTM 1550)
• Mode of failure dominated by flexure.
• This can test higher deflections compared to ASTM
1609
• 32” (810 mm) diameter x 3” (76 mm) thick panel
Kaiser

46. Laboratory Fatigue Evaluation of
Continuously Fiber Reinforced Concrete
Pavement
Rupnow/Kevern Rupnow/Kevern

47. Concrete Mix Design
Coarse
Aggr.
(lb/yd3
)
Fine
Aggr.
(lb/yd3
)
Water
(lb/yd3
)
Polypropylene
Macro
Fibers
(lb/yd3
)
Carbon
Fibers
(lb/yd3
)
Steel
Fibers
(lb/yd3
)
Polypropylene
Fibrillated
Fibers
(lb/yd3
)
1938 1290 250
1911 1267 250 1.5
1907 1268 250 3.0
1899 1270 250 4.5
1895 1274 250 4.5
1894 1267 250 7.5
1900 1253 250 10.5
1888 1252 250 15.0
1895 1274 250 9.0
1890 1259 250 21.0
1883 1251 250 30.5
1888 1266 250 85
Rupnow/Kevern

48. Results – Fatigue Testing
Rupnow/Kevern

49. Results – Fatigue Testing
Rupnow/Kevern

50. Results – Fatigue Testing
Rupnow/Kevern

51. Results – Toughness Testing
Rupnow/Kevern

52. Results – Toughness Testing
Rupnow/Kevern

53. Results – Toughness Testing
Rupnow/Kevern

54. Conclusions
• Fibers improve fatigue performance
• Carbon fibers increase performance when dosed
above 21 pcy compared to steel
• Polypropylene fibrillated and macro fibers increase
fatigue performance when dosed correctly
• Fiber reinforcement can inhibit performance
compared to steel when overdosed, but not below
that of plain concrete
Rupnow/Kevern

55. Conclusions
• Toughness testing showed that tensile strength and
dosage rate were critical for ductility
• Fibers with increased tensile strengths had a greater
residual load carrying capacity AND carried greater
loads at larger deflections
• Pre-cracked fatigue testing showed that the length of
the fiber is also crucial to the performance
Rupnow/Kevern

56. Field Testing