1. Crack-Opening and Crack-Spacing in Cement
Treated Base Layers
CROW Infradagen 2014
Woldekidan M.F., Huurman M.
Presenter: R. Huurman
2. Bound Base layers : Semi-rigid Pavements
- Offer some advantages of Rigid Pavements
• distribute higher loads better minimize subgrade loads
•When succesull, offers good durability & high performance
- Attractive from environmental aspect (eg use of recycled
materials)
Disadvantage:
- Cracking is envitable
- When cracks grow to surface performance is
compromised
Background
3. CTB advantages are maintained only if cracking is controlled
Prediction tools are of paramount importance
Background
5. Concept: crack initiation mechanism
Approach
• Fixed ends with infinite length
• Shrinkage in CTB (Hydration+Temperature fluctuation)
• Restrained interfaces
DT
Tensile stresses develop at the center
6. Crack initiation to crack growth
Approach
• Crack initiationcrack tip
• Fracture mechanics:
- analysis of crack tip to full crack formation
Scope : crack initiation moment
7. Material strength & stress state sxx
Approach
All factors direct-indirect dictate the ultimate stress sxx in the CTB
Material strength sxx dictate moment of crack initiation
H
Establish relationship between sxx and the various influencing factors !
8. - 2D FE Modeling
Finite Element Modeling
- Temprature loads are appliedDevelopment of sxx is analyzed
Variables:
•Geometry: Thickness (H) and Length (L)
•Boundary condition (Bedding constant, Ch)
•Material Properties ( aT, E-modulus )
H
16. Tool Outputs
Interface
jaar 1985
doorlopend 1
eerste dag 150
lineaire temp coefficient 1.06E-05 [-/°C] 7 tot 10 E-6
Horizontale beddingconstante 0.00100 [Mpa/mm] tussen 0.01 en 0.001??? Zoek dit uit!
Dikt 250.00 [mm]
a b 28 dgn
druksterkte 0.417651 0.5 2.21
Eo 900 dit is 1800 bij beton
eps sc inf -4.00E-04 dit is 1 tot 7E-04 voor beton
sig traffic 0.004587 0.5
open 28
precracklength 0 <=25 m; uncracked = 0
21. Practical tool for predicting performance
Suitable for incorporating expected variations in Material
properties
Useful for optimization (performance vs Material
selection/pavement geometry)
Future improvements:
Traffic stress estimates can be improved: relations can be
developed using Multi-layer analyses.
Conclusions