Table 13.  Estimated Maintenance Schedule for Different ESAL Levels

 34

FINDINGS 

 

The main findings of this study concerning the technical and economic evaluations of 

composite pavement systems to be used during the PTS process are the following: 

 

•  According to the literature, countries (e.g., the U.K., Spain) that have used composite 

pavement systems in their main road network have had a positive experience in terms 

of functional and structural performance.  The review suggests that this type of 

pavement can also perform satisfactorily in Virginia.  Furthermore, good performance 

could also be expected from existing CRCP overlaid with high-quality HMA surfaces 

if the overlay is applied when the existing pavement is still in relatively good 

condition. 

 

•  At the technical level, composite pavements mitigate various structural and functional 

problems that typical flexible or rigid pavements tend to present.  The use of rigid 

bases minimize (or eliminate) the development of distresses such as HMA fatigue 

cracking, subgrade rutting, PCC erosion, and PCC loss of friction, among others.   

 

•  However, other types of distresses such as reflective cracking and rutting within the 

HMA layer need to be considered because they affect composite pavement systems 

more than the traditional pavement structures.  Premium HMA surfaces and/or 

reflective cracking mitigation techniques may be required to mitigate these potential 

problems.  The minimum thickness of the HMA layers to mitigate reflective cracking 

range from 100 to 200 mm (4 to 8 in).  One of the countries with more experience 

concerning composite pavements is the U.K., which uses an HMA layer thickness of 

175 mm (7 in). 

 

•  The use of a high-stiffness base layer under the HMA surface course provided the 

following benefits: 

 

─  Deflections at the HMA surface are significantly reduced as the stiffness of the 

base layer increases.   

─  Fatigue (bottom-up) cracking in the HMA, due to high tensile strain at the bottom 

of the layer, is greatly minimized; in some cases the number of repetitions to 

fatigue cracking was determined to be unlimited. 

─  Permanent deformations (rutting) due to vertical compressive strains and stresses 

in the unbound subbase and, most importantly, subgrade layer are significantly 

minimized.   

 

•  On the other hand, permanent deformations within the HMA layer tend to increase as 

the stiffness of the base increases; however, the use of rut resistant mixes such as 

SMA may reduce this effect.   

 

•  A deterministic LCCA (considering only agency costs) showed that of the composite 

pavement with CTB can cost less than the traditional flexible and rigid pavement 

alternatives.  Comparing the composite with CTB to the flexible pavement, the 

 35

composite alternative requires a lower HMA thickness due to the high support 

provided by the rigid base. 

 

•  A sensitivity analysis of the agency costs over the life-cycle of the pavements, 

suggests that CRCP base composite pavements can become a cost-effective 

alternative for very high-traffic high-priority highways (carrying more than 

approximately 140 million ESALs). 

 

 

CONCLUSIONS 

 

Composite pavement systems can become a cost-effective pavement alternative during 

the PTS process for high-volume high-priority highways because of the functional, structural, 

and economic benefits they can provide during their service life.  These types of structures can 

provide long-life pavement that offers good serviceability levels and rapid, cost-effective 

maintenance operations.  While likely to be more suited for new construction, composite 

pavements are still relevant for VDOT in that they should be considered for lane addition 

projects (such as truck climbing lanes) that are expected to carry high traffic volumes and heavy 

truck loads. 

 

The feasibility-level LCCA suggests that the use of a composite pavement with a CTB 

can be a cost-effective alternative for a typical Interstate traffic (e.g., 35 million ESALs).  

Alternatively, composite pavement with CRCP base may become more cost-effective for very 

high volumes of traffic (approximately 140 million ESALs and greater). 

 

Finally, it is important to note that the maintenance schedule for the CRCP base 

composite pavements analyzed was determined based on the literature review, and its 

applicability to Virginia highways should be verified.  The costs of reflective cracking mitigation 

actions were not included in the feasibility analysis. 

 

 

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