Page 152 - RoadCem Manual - PCT BV

Fatigue - bound foundation
Repeated load application on a bound foundation can lead to cracks in the lower part of the construction. The cracks could carry on through the construction and appear on the surface. For a foundation material with RoadCem the fatigue ratio has not yet been determined, but knowing the properties of RoadCem with its special fibrous crystal structure is can be assumed. With bound foundation materials there are 2 fatigue ratios known:
• with sand cement (>8% cement), and
• AGREC (3,5% cement) foundations.
The ratio with sand cement is less favorable compared with AGREC. The percentage of cement in a construction with RoadCem is approx. 8% and based on this it comes close to that of a sand cement foundation. Yet it has been chosen to use the AGREC-fatigue ratio for RoadCem. This is because of the crystalline structure that RoadCem develops and the resulting improved fatigue resistance. This must be verified for each project. With standard construction the AGREC fatigue ratio is used as shown in formula 5.4.
∑log(Nfatfund,L )i =0,5⋅log(Nfatfund,L )full +0,5⋅log(Nfatfund,L )empty NCA =i
log(Nfatfund,L)full =21,37−7,72⋅ε(r,fund)full log(Nfatfund,L )empty =21,37−7,72⋅ε(r, fund)empty
Formula 5.4 Fatigue bounded foundation (AGRAC).
Nfatfund,L = Permissible number of load repetitions based on strain at the lower level of foundation
ε(r,fund)full =Horizontal strain at the lower level of unbound foundation with full truck load on the road construction.
ε(r,fund)empty =Horizontal strain at the lower level of unbound foundation with empty truck load on the road construction.
Figure 5.39 Fatigue Cracks in asphalt.
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