Abstract Manager

The TAC ME Design Subcommittee has been evaluating the AASHTOWare Pavement ME Design (PMED) since 2007-2008. Between September 2022 and February 2023, three sets of design trials were completed with different climatic inputs from nine weather stations across Canada to assess the effect of concrete mix properties such as compressive strength, cementitious materials content, coefficient of thermal expansion (CTE), w/c ratio and unit weight, concrete slab thickness, dowel size (diameter) and joint spacing on the PMED predicted distresses. A total of 46 (10 with software v2.6 and 36 with software v3.0) design runs with different combinations of inputs were completed for each climate station. 

The results from software v2.6 indicated that lower compressive strength, cementitious materials content, CTE and w/c ratio, and higher density provide a reduction in the predicted IRI and joint faulting. Only a high CTE of > 8.0 seems to affect the predicted transverse cracking. As in the case of other trials completed earlier, varying climate has shown to have significant effect on the predicted IRI, a lesser effect on the predicted faulting and no or negligible effect on the predicted transverse cracking. The trial results also showed some inconsistencies and significant differences in the predicted distresses between software v2.6 and 3.0.

The trial results (using the software v3.0) showed that an increase in the PCC thickness for the same dowel size results in an increase in the predicted IRI and faulting. These findings do not represent the well-known effect of increased concrete thickness on providing a smother pavement with reduced faulting over a long term due to the improvement in the aggregate interlock. An increase in the PCC thickness showed a reduction in the predicted transverse cracking, which is logical. The results also showed that thicker dowels provide a significant reduction in the predicted faulting and IRI, and have no or minimal effect on the predicted transverse cracking. PCC joint spacing showed no or minimal effect on the predicted IRI, a significant effect on the predicted joint faulting for concrete pavement thicker than 200 mm and for high CTE values, and a significant effect on the predicted transverse cracking.   

The objective of this paper is to present the details of the above stated trial results, analysis and findings. This information may help different agencies and other interested individuals in assessing the suitability of the current versions of the PMED software when designing concrete pavement structures and varying concrete mix properties, thickness, dowel size and joint spacing.