curing methods to mitigate early -age bridge deck cracking · thermal and stress modeling...
TRANSCRIPT
![Page 1: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/1.jpg)
Click to edit Master title style
www.wje.com
SOLUTIONS FOR THE BUILT WORLD
Curing Methods to Mitigate Early-Age Bridge Deck Cracking
Todd Nelson, P.E. – Associate Principal September11, 2019
![Page 2: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/2.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendation
Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking
Project Background Field Investigations Laboratory Evaluations Thermal and Stress Modeling Curing Recommendations
Solutions for the Built World Page 2
Curing Methods to Reduce Early Age Deck Cracking
![Page 3: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/3.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
In 2016, MDT communicated to WJE that severe transverse cracking was noted on a number of bridge decks in western Montana
In three bridges, cracking led to deck penetrations (holes in the deck)
Concrete decks were only 1 to 9 years old MDT and FHWA commissioned WJE in early 2016 to
investigate the problem
Solutions for the Built World Page 3
Project Background - General
![Page 4: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/4.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Solutions for the Built World Page 4
Project Background – MDT Documentation
![Page 5: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/5.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Solutions for the Built World Page 5
Project Background – Distress Reported by MDT
![Page 6: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/6.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Recommendations
Solutions for the Built World Page 6
Project Background – Distress Reported by MDT
![Page 7: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/7.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Solutions for the Built World Page 7
Project Background – Distress Reported by MDT
![Page 8: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/8.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Solutions for the Built World Page 8
Project Background – Distress Reported by MDT
![Page 9: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/9.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Solutions for the Built World Page 9
Project Background – Distress Reported by MDT
![Page 10: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/10.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Field Investigation Detailed investigation of four bridges
– Crack mapping
– Delamination survey
– Infrared thermography
– Drone (photographs, thermographic imagery, and video)
– Ground penetrating radar
– Concrete coring
Comparative investigations of eight additional bridges
Solutions for the Built World Page 10
Field Investigation
![Page 11: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/11.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Solutions for the Built World Page 11
Field Investigation – Types of Cracking
Map cracking
Transverse cracking
![Page 12: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/12.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Solutions for the Built World Page 12
Field Investigations – Transverse Cracking
![Page 13: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/13.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Solutions for the Built World Page 13
Field Investigation – Transverse Cracking
Transverse cracking
![Page 14: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/14.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Solutions for the Built World Page 14
Field Investigation – Transverse Cracking
Transverse cracking - Underside
![Page 15: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/15.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Hypothesis on crack progression:1. Transverse cracks develop, likely early – to be investigated
further 2. Transverse cracks progress over time3. Closely-spaced transverse cracks form “jump” cracks4. Continued volumetric movement and traffic loading -
widen and ravel transverse and “jump” cracks5. Deck penetrations may develop at “jump” cracks with the
right conditions: Deck penetrations more prone to occur with top and bottom
mats aligned
The more closely spaced the transverse cracks, the more likely deck penetrations will occur
Solutions for the Built World Page 15
Field Investigation - Characteristic Cracking
![Page 16: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/16.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Solutions for the Built World Page 16
Field Investigation - Characteristic Cracking
“Jump” cracking
Transverse Crack
“Jump” Cracks
![Page 17: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/17.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Solutions for the Built World Page 17
Field Investigation - Characteristic Cracking
![Page 18: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/18.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Solutions for the Built World Page 18
Field Investigation - Characteristic Cracking
![Page 19: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/19.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Solutions for the Built World Page 19
Field Investigation – Deck Penetration
![Page 20: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/20.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Transverse crack spacing varied from 2 to 4 feet on most bridges More frequent than typical
Transverse cracks predominately over transverse bars (GPR)
Width of transverse cracks were typically 15 to 25 mils Plastic shrinkage cracking noted on some decks, most
severe on Florence-East MP 10.640 - 1 year old and contained silica fume concrete.
Longitudinal cracking noted, but not significant
Solutions for the Built World Page 20
Field Investigation – Cracking
![Page 21: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/21.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Solutions for the Built World Page 21
Field Investigation – Drone Photographs
![Page 22: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/22.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Solutions for the Built World Page 22
Field Investigation – Infrared Thermography
![Page 23: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/23.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Why?
Solutions for the Built World Page 23
Field Investigation – Infrared Thermography
![Page 24: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/24.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Concrete deck surface and underside temperatures were measured Surface temperatures varied from 42 F to 104 F Underside temperatures varied from 40 to 58 F Very high temperature swings! Fairly unique to
Montana Relevant to subsequent thermal analysis and modeling
Solutions for the Built World Page 24
Field Investigations – Deck Temperatures
![Page 25: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/25.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Laboratory Evaluations
42 Cores were extracted from the field Petrographic Analyses (ASTM C856) Physical Properties
– Compressive Strength (ASTM C42)
– Splitting Tensile Strength (ASTM C469)
– Thermal property evaluation (COTE)
Others (Chloride ion content, x-ray diffraction, SEM)
Solutions for the Built World Page 25
Laboratory Evaluations
![Page 26: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/26.jpg)
Solutions for the Built World Page 26
Laboratory Evaluations - Petrography
![Page 27: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/27.jpg)
Solutions for the Built World Page 27
Laboratory Evaluations - Petrography
![Page 28: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/28.jpg)
Solutions for the Built World Page 28
Laboratory Evaluations - Petrography
All transverse and “jump” cracks appeared to have initiated very early –cracks propagate around aggregates
No signs of internal distress Air void system is good for freeze/thaw
durability Aggregates are sound W/cm ratios were adequate,
occasionally slightly elevated
![Page 29: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/29.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Thermal and stress modeling on three bridges Temperature model: ConcreteWorks Stress model: Mathcad tool based on Zuk (1961)1
Why? Have a better understanding of early age temperature
changes and gradients and associated stresses Sensitivity analysis – curing options, daily temperature
changes, concrete temperatures, placement times, deck thickness, etc.
Results to help guide recommendations
Solutions for the Built World Page 29
Thermal and Stress Modeling
1Zuk, W. “Thermal and Shrinkage Stresses in Composite Beams,” Journal of the American Concrete Institute, (1961): 327-340.
![Page 30: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/30.jpg)
0
20
40
60
80
100
120
6/7 6/8 6/9 6/10 6/11 6/12 6/13 6/14
Max
. Dec
k Te
mpe
ratu
re (°
F)
Date/Time
Bridge 6
6:00 AM 12:00 PM (noon)6:00 PM7:00 AM (Actual) Ambient
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Solutions for the Built World Page 30
Thermal and Stress Modeling
35 oF difference!
![Page 31: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/31.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Sensitivity Analysis: Key Findings High sensitivity to tensile stresses caused by early-age
ambient temperature drops and corresponding drop in peak hydration temperatures
Stresses due to thermal gradients (e.g., cooling of deck surfaces) are greater magnitude than stresses due to uniform temperature changes
Strains due to temperature generally larger than strains due to autogenous shrinkage for bridges investigated
Drying shrinkage may be significant at later ages
Solutions for the Built World Page 31
Thermal and Stress Modeling
![Page 32: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/32.jpg)
Solutions for the Built World Page 32
0%10%20%30%40%50%60%70%80%90%
100%
Shrinkage
AutogenousSettlementPlasticThermalDrying
![Page 33: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/33.jpg)
Transverse cracks are likely initiated at early ages Driven by early age temperature gradients
Cracks continue to propagate “Jump” cracks occur with tightly spaced transverse
cracks Deck penetrations occur under right conditions
Deck penetrations more prone to occur with top and bottom mats aligned
The more closely spaced the transverse cracks, the more likely deck penetrations will occur
Driving lanes and under wheel paths more susceptible
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Solutions for the Built World Page 33
Conclusion
![Page 34: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/34.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Solutions for the Built World Page 34
Recommendations Goals of recommendations?
Reduce early age temperature gradient and associated stresses
Reduce autogenous shrinkage Reduce the potential for early age and long term drying
shrinkage Maintain low permeability concrete Maintain durability and service life Work with MDT to achieve practical implementation
![Page 35: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/35.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Solutions for the Built World Page 35
Specific Recommendations Curing
Immediately fog mist placements until wet curing media is in place
Contractor to measure evaporation rate Apply wet-curing methods immediately after finishing
Pre-Wet burlap, cotton blankets, but no plastic!
Why is this important?
![Page 36: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/36.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Why?
Solutions for the Built World Page 36
Specific Recommendations Curing
Application of insulation blankets shortly after peak hydration temperatures
Contractor to monitor concrete temperatures When concrete temperatures are within 5ºF of ambient and
vertical temperatures through deck thickness are uniform -remove insulation
Minimum of 72 hours old (or 96 hours old if concrete contains silica fume), remove all curing and allow deck to dry.
After the surface has dried, white-pigmented curing compounds may be applied.
![Page 37: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/37.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Solutions for the Built World Page 37
Specific Recommendations Placement Times
Move placement times to afternoon– Based on modeling, late afternoon likely best
Prevents peak hydration temperatures to occur during peak ambient temperatures
Moves peak concrete temperature to 2 to 3 days later -concrete has higher tensile strength
![Page 38: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/38.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Solutions for the Built World Page 38
Specific Recommendations
0
20
40
60
80
100
120
7/25 7/26 7/27 7/28 7/29 7/30 7/31 8/1
Max
. Dec
k Te
mpe
ratu
re (°
F)
Date/Time
Bridge 1
6:00 AM 12:00 PM (noon)6:00 PM2:00 AM (Actual) Ambient
![Page 39: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/39.jpg)
Solutions for the Built World Page 39
0
100
200
300
400
500
600
700
800
900
1000
0
20
40
60
80
100
120
140
0 10 20 30 40 50 60 70 80
Mat
urity
(F-H
ours)
Tem
pera
ture
(F)
Time after Placement
Precast Curing Temp Modified Curing Temp
Standard Deck Cure Temp Precast - Maturity
Standard Curing - Maturity Modified Curing- Maturity
![Page 40: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/40.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
Solutions for the Built World Page 40
Additional Recommendations Mixture Proportions Recommendations
Reduce plastic concrete temperatures < 75F Limit silica fume replacement to 5% Specify w/cm between 0.42 and 0.45 Limit cementitious material contents to 600 lb./yd3 or less Optimized gradation and crushed aggregates
Why are these important?
![Page 41: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/41.jpg)
Outline
Project Background
Field Investigation
Laboratory
Evaluations
Thermal and Stress
Modeling
Recommendations
WJE’s recommendations implemented on approximately 24 new bridge decks since early 2017 MDT reports a decrease transverse cracking. WJE briefly inspected one new deck placed in the Helena area
(built in summer of 2017), approximately three weeks after placement – transverse cracks were difficult to find (very tight) and spaced far apart
Additional research initiated in 8/2019 to evaluate bridges constructed with recommendations, instrument new bridge decks to capture actual early age temperatures and strains, and perform additional detailed modeling and laboratory evaluations.
Page 41
Implementation
![Page 42: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/42.jpg)
Matt Needham – MDT Paul Bushnell – MDT Paul Krauss – WJE Elizabeth Nadelman - WJE
Solutions for the Built World Page 45
Special Thanks!
![Page 43: Curing Methods to Mitigate Early -Age Bridge Deck Cracking · Thermal and Stress Modeling Recommendation Montana DoT Case Study: Curing Methods to Mitigate Early Age Cracking Project](https://reader030.vdocuments.mx/reader030/viewer/2022013020/5e9c4ae0ad0b17142c2c962c/html5/thumbnails/43.jpg)
Questions?Thank you very much for the opportunity!
Solutions for the Built World Page 46