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Effect of HMA Density, VMA and AC Content on PMED Software Predicted Distresses in Flexible Pavement

Abstract

An  empirical  pavement  design  method  such  as  the  American  Association  of  State  Highway  and  Transportation Officials (AASHTO) 1993 pavement design guide uses structural layer coefficient (ai) value to determine thickness of each layer material or to convert a selected layer thickness to structural number (SN). Any change in material composition and properties will affect the ai value, which will directly affect the  required  thickness  of  that  layer  in  a  logical  manner.  However,  there  are  concerns  regarding  the  sensitivity and trends of predicted distresses using the AASHTOWare Pavement Mechanistic‐Empirical Design  (PMED)  software  for  different  design  inputs  including  material  properties  and  the  consistency  among the PMED software versions. Two sets of design trials were completed between November 2023 and February 2024 in this study, using the latest web version (v3.0) of the PMED software, to assess the effect of hot mix asphalt  (HMA) in‐place compaction, which ranged from 90  to 97%, and the voids in  mineral aggregates (VMA), which ranged from 13 to 17%, on the predicted distresses. Climatic data from nine to ten weather stations across Canada were used.

The analysis showed that a lower density/compaction (increased air voids) in an HMA mat results in an increase of predicted IRI, total and HMA (i.e., asphalt concrete) layer rutting, bottom‐up fatigue cracking (BUFC),  and  thermal  cracking  (TC),  but  an  inconsistent  variation  of  top‐down  fatigue  cracking  (TDFC).  Increased VMA and asphalt cement (AC) content results in a reduction of predicted IRI, BUFC, TDFC and TC, and an increase in total and HMA layer rutting. In general, the predicted distresses were shown to be very  sensitive  to  changes  in  HMA  density  (air  voids),  VMA,  and  AC  content.  The  impact  of  climatic  condition on predicted distresses was not shown to be as expected or practically experienced. This paper presents the details of these trials including trend analyses and findings.

Conference Paper Details

Session title:
Innovations in Pavement Management, Engineering and Technology
Author(s):
Ahammed, M. Alauddin
Podborochynski, Diana
Leung, Yuen‐Ting Fiona
Liu, Qingfan
Lapain, Shawn
Topics:
Pavements
Year:
2024