Mohammad Tahir Ansari

Pavement management systems encompass pavement maintenance and rehabilitation (M&R) as critical components to postpone reconstruction by addressing pavement deterioration in the early stages of service life. Life-cycle cost analysis (LCCA) serves as a financial tool within these systems, aiding in determining pavement alternatives. The objective of this study was to determine the life-cycle cost of flexible and rigid pavement alternatives, including initial construction, M&R costs to users and agencies, and salvage value over 50-year life-cycle. The study examines four roadways having alternative flexible and rigid pavement designs using a deterministic approach. The frequency of treatment application varies based on average daily truck traffic. LCCA analysis shows that initial cost of pavements represented 72% to 91% of net present value (NPV), while user costs had negligible impact, comprising less than 6% of NPV for each alternative. The highest NPV observed is $0.90 M and $1.34 M for flexible and rigid pavements, respectively. The percentage difference between flexible and rigid pavement in NPV varies from 39% to 56%. In brief, LCCA indicates that flexible pavement is a more cost-effective alternative than rigid pavement across various traffic conditions and pavement thicknesses. However, actual performance in the field will ultimately determine their effectiveness.

Asphalt emulsions can be produced with colloid mills and high-speed shear mixers, but effects of equipment type on emulsion properties are largely unknown. The study objective was to assess the impact of different manufacturing equipments on emulsion properties. Particle size, viscosity, residue, sieve and storage stability properties were observed after production on three emulsion manufacturing devices. For each device, three emulsions were manufactured by three operator pairs. Median particle size was as small as 2.0 microns on recirculating and in-line equipment, but only 5.3 on high-speed shear mixer. Recirculating equipment also produced emulsion with better storage stability than high-speed shear mixer and in-line equipment. In-line manufactured emulsions had the highest viscosity while the shear-mixed emulsion viscosity was below specification. Sieve was significantly affected by the operator. These results demonstrate that emulsions produced by different laboratory equipment are not identical, and caution must be exercised when comparing and manufacturing lab-produced emulsions.

Many state agencies recognize that their current asphalt mixtures are susceptible to cracking and poor durability. Some agencies are adjusting their mix design procedures to increase the asphalt binder content, while others are moving toward a balanced mix design (BMD) to try and address both cracking and rutting. However, there is uncertainty on what asphalt mixture properties can impact cracking and rutting. This research explores the IDEALCT and APA data from two years of mix designs collected by ARDOT. To understand which asphalt mixture properties impact cracking and rutting in the field, Pearson correlation (PCM), Spearman rank correlation (SCM) and Kendall’s Tau (KCM) analysis methods were used. After running these analysis methods, CTIndex had the highest correlation with film thickness, while the rut depth had the highest correlation with the upper asphalt binder grade across all three. Interestingly, the second highest correlation was volumetric, with VFA or air voids for CTIndex and VMA or air voids for rut depth. As a part of this analysis, a preliminary recommendation for a minimum 9 microns asphalt film thickness has been made to ensure mixture durability. Finally, a procedure is provided for other owners to examine how their asphalt mixture properties impact their performance tests. Based on this research it is not recommended to use KCM, as it had the lowest correlation values. Both the PCM and SCM methods are recommended for use.