MnROAD Environmental Factors that Affect Ride

The performance of asphalt-treated mixtures used in low-volume roads was evaluated, and their environmental benefits were assessed. Laboratory tests, including permeability, modified Lottman, Hamburg-type loaded wheel tracking, flow number, semicircular bend, dissipated creep strain energy, and dynamic modulus tests, were performed to examine the physical and mechanical properties of the asphalt-treated mixtures. Mechanistic–Empirical Pavement Design Guide (MEPDG) software was used to compare the performance of low-volume pavement sections with asphalt-treated mixtures to that of a conventional hot-mix asphalt (HMA) mixture. Life-cycle assessment was also conducted to quantify the environmental impacts of using asphalt-treated mixtures in lieu of conventional HMA mixtures in the construction of low-volume roads. Test results demonstrated that asphalt-treated mixtures containing limestone and reclaimed asphalt pavement exhibited similar properties to those of well-performing conventional HMA mixtures. MEPDG analysis showed that pavement sections with asphalt-treated mixtures exhibited similar performance to those with conventional low-volume HMA mixtures. Life-cycle assessment indicated that using asphalt-treated mixtures in low-volume roads could result in reductions of up to 29% in carbon dioxide emissions, 29% in energy consumption, 39% in water consumption, and 42% in hazardous waste generation.

Low-volume roads in regions susceptible to freezing and thawing periods are often at risk of load-related damage during the spring thaw. Reduced support capacity during this period results from excess melt water that becomes trapped above underlying frozen layers. Many agencies place spring load restrictions (SLRs) during the thaw period to reduce damage to roadways. The period of SLRs set forth by the Minnesota Department of Transportation is effective for all flexible pavements; however, experience suggests that many aggregate-surfaced roads require additional time relative to flexible pavements to recover strength sufficient to carry unrestricted loads. An investigation was performed to improve local agencies’ abilities to evaluate the duration of SLR on aggregate-surfaced roadways. This was accomplished through seasonal measurements of in situ shear strengths, measured with the dynamic cone penetrometer, on various Minnesota county routes. In situ strength tests were conducted on selected county gravel roads over the course of 3 years. Strength levels recorded during the thaw-weakened period were compared with fully recovered periods that typically occur in late spring or summer. Results indicate that aggregate-surfaced roads generally require 1 to 3 additional weeks over that required by flexible pavements to reach recovered bearing capacity.

The U.S. encompasses over 4 million roadway miles, with about half of them located in seasonal frost areas. Roads are especially susceptible to damage when the subsurface is saturated with water (i.e., spring thaw). Spring load restrictions (SLR) are important for maintaining the integrity of roads. Routine determinations of road freeze–thaw (FT) state are limited to vertically embedded temperature data probes (TDP). Although TDPs are valuable to departments of transportation for determining SLRs, TDPs only represent individual points within the road network and are costly to install and maintain. Recent updates to spaceborne technology and algorithms made physically based retrievals of FT conditions possible at improved accuracy and temporal resolution (every 3 days) and have potential use for assisting with SLRs. Although instruments such as NASA’s Soil Moisture Active Passive (SMAP) platform cannot resolve individual roads, past comparisons have shown good correspondence with TDPs. The main objective of this study is to provide information on the potential value of NASA’s SMAP FT tool to supplement other methods for making seasonal load restriction decisions. Results are compared against data and protocols by the Minnesota Department of Transportation (MnDOT) at 10 sites in Minnesota, over four winter seasons (2016–2019). Results show that even when a simple criterion is used—the date of the third consecutive thaw from the SMAP afternoon retrieval—those dates typically fell within a week of MnDOT road postings (61% of the time). In addition, SMAP FT typically matches TDP FT states throughout the year (79% of the time).

Seal surfacing is frequently used on low-volume roads throughout the world. However, seal surfacing is also used on high-volume roads in Turkey. Seventy-nine percent of the total amount of road length for which the General Directorate of Turkish Highways is responsible is coated with seal surfacing, and most of the 15 000 km of divided roads under construction are projected to be seal-surfacing roads. For this reason, there is a need for more information about seal surfacing. Within the context of the present study, the state and provincial roads located in the south-western part of Anatolia were investigated and core samples were taken from multi-layered seal-surfacing pavements. The core samples were fixed in size to match the standard Marshall sample size. The physical characteristics were defined by carrying out unit weight tests, ultrasound tests and Marshall stability tests. Skid resistance tests were performed around the core extraction areas on the road surfaces. In order to conduct analyses of the binder portions and the aggregate portions of the core samples, binder was extracted from the core samples through the use of a centrifuge extractor. As a consequence, attempts were made to determine the physical characteristics and actual conditions of multi-layer seal surfacing. In conclusion, it emerged that in the case of both building techniques and material characteristics, seal surfacing differs from hot mix asphalt. However, multi-layer seal surfacing demonstrates properties that are similar to those of hot mix asphalt. It must be taken into consideration that there are significant differences in stability and yield values.

Major highways are designed to withstand heavy vehicles and high volumes of traffic year round. However, low-volume roads in seasonal frost areas are highly susceptible to damage from trafficking by heavy vehicles during spring thaw. Conventional practice is to place partial or full spring load restrictions on low-volume roads during spring thaw. This practice reduces road damage significantly. However, companies whose livelihood depends on trucking can suffer major economic losses as they await the removal of load restrictions. Using reduced tire pressure constitutes a less conventional technique that can reduce springtime damage. Reducing tire pressure generally appears to be less effective than reducing load. Nevertheless, it does appear that the load restriction window can be shortened in duration by implementing a reduction in tire pressure for a few weeks, starting toward the latter part of the standard spring load restriction period. With a mechanistic pavement design and evaluation model for seasonal frost areas, a critical combination of load and tire pressure reduction was developed; it contributes to optimizing the balance between minimizing springtime road damage and minimizing disruption to local economies caused by load restrictions. This analysis constitutes the first step in the development of simplified, general application guidelines for shortening the springtime load restriction window for a variety of pavement structures.

Recent studies have concluded that measured surface deflections can be used as a low-cost pavement monitoring and condition assessment tool to determine remaining structural life and pavement performance. Moving load devices are being used more often to measure continuous surface deflections. They are considered a faster alternative to falling weight deflectometer–based structural condition evaluation applications. The objective of the study was to compare the analytical dynamic simulation of slow-moving deflection measurements with field data. The surface pavement deflections and the pavement structural responses generated by the Euroconsult Curviametro loading at the Minnesota Department of Transportation’s MnROAD facility near Maplewood, Minnesota, were used in the evaluations. Four geophones were embedded near the pavement surface to measure surface deflections during field trials at each of three tested MnROAD cells. In addition, numerous other sensors, such as strain gauges and thermocouple trees, were available at the MnROAD facility. The 3D-Move program was used in the simulations because it can accommodate moving loads and the viscoelastic properties of pavement layers and produce continuous deflection basins. The viscoelastic properties of pavement layers were estimated on the basis of the actual temperatures at the time of the field trials and the appropriate loading frequency of the Curviametro. The proposed dynamic analytical model provided a good match with a variety of independent pavement responses, which included surface deflection basins (measured by embedded geophone sensors) as well as horizontal strains at the bottom of the asphalt concrete layers (measured by MnROAD sensors).

Geosynthetic reinforcements have shown effective performances in basal reinforcement of low volume roads under traffic loads. In recent years, these reinforcements have also been used to improve roads against environmental loading. This study evaluates the performance of geosynthetic-reinforced and lime-treated low volume roads under both traffic loads and environmental conditions. Thirty two test sections were constructed in 2006 over expansive clay subgrade in Grimes County, TX. The sections involved eight different cross sections, including control (unreinforced) sections, subbase lime-treated sections, base geosynthetic-reinforced sections with three geosynthetics types, and combinations of subbase lime-treated with base geosynthetic-reinforced systems. An index of pavement performance was used to compare and rank the overall performance of the road sections. The geogrid reinforced sections were found to significantly enhance the performance of the road sections by preventing the development of longitudinal cracks in paved area. On the other hand, lime treatment showed only limited improvements to the performance of the reinforced sections.

Warm mix asphalt (WMA) is a cost effective means for reducing the mixing and compaction temperature of hot mix asphalt (HMA). These additives, which come in several forms, reduce the mixing and compaction temperatures by approximately 30°C. The challenge for researchers has been determining how the additives impact or change traditional HMA mixes. The purpose of this research is to use collected laboratory data as inputs into the Mechanistic-Empirical Pavement Design Guide (MEPDG) to determine if there are statistically significant differences in the amount of pavement cracking when comparing HMA and WMA. The MEDPG is a model that has been developed into software for the purpose to provide state-of-the-practice pavement design for both new and rehabilitated pavement structures. The pavement design includes site condition parameters such as traffic, climate, subgrade, and existing pavement conditions in the case of rehabilitation. The MEPDG evaluates a proposed design for various distresses such as rutting, fatigue cracking, longitudinal cracking, transverse cracking, and roughness. Samples from field produced WMA mixes have been tested and material information has been collected and statistically analyzed over a period of several years. Data analysis showed some statistically significant differences in laboratory dynamic modulus (E*) data when comparing HMA control mix with the WMA mix. This study will use the laboratory measured E* as input into the MEPDG model to predict the pavement cracking in order to determine if there are differences in the pavement distresses. Within the design inputs, various factors can be manipulated such as various traffic loading and pavement thickness. Changing these inputs show which site condition variables have the most impact on pavement performance, how pavement distresses may differ when comparing HMA and WMA and how this translates to differences in pavement life.

The objective of this research was to investigate the variability of base layer construction in hot-mix asphalt (HMA) pavements and to assess the impact of base layer variability or nonuniformity on pavement performance. Subjective acceptance criteria of base layer construction may lead to variable pavement performance and may result in early pavement distresses and failure. Eleven existing HMA pavement projects with aggregate base course layers constructed in the past few years were selected for falling weight deflectometer (FWD) testing and visual distress surveys. In six of these projects, issues with aggregate base performance (stability and uniformity) had been observed and reported during paving of the HMA surface layer. Later, these pavements exhibited various levels of early distresses, including cracking (longitudinal, transverse, and alligator), aggregate base failure, and pavement surface roughness or irregularities (for ride quality). The remaining five HMA pavement projects, for which no issues related to aggregate base layer behavior were reported during construction, performed well after construction. A test section of approximately 1 mi on each project was subjected to FWD testing. The existing HMA pavements that showed early distresses exhibited high levels of spatial variability and nonuniformity in aggregate base course layers, as demonstrated by FWD testing and backcalculated base layer modulus values and distributions. The existing HMA pavements that performed well exhibited low levels of spatial variability and good uniformity in aggregate base course layers, as shown by the FWD test results and the backcalculated base layer modulus values and distributions.

The objective of this study was to investigate the effects of various factors affecting bond strength between hot mix asphalt (HMA) overlay and underlying pavement layers in the field. The effect of interface bonding on short-term pavement performance was also evaluated. A list of candidate HMA field rehabilitation projects was identified across the United States, representing different traffic and environmental conditions. These projects included the rehabilitation of new, existing, and milled HMA pavements, and PCC pavements. Each field project involved at least one slow setting and one rapid setting non-tracking tack coat material, thereby creating one or more pairs of tack coats for comparison. The HMA overlay construction used different types of tack coat materials at various residual application rates. Specimens were cored from the evaluated test sections at different service times to determine the interface shear strength (ISS) according to AASHTO TP 114, “Standard Method of Test for Determining the Interlayer Shear Strength of Asphalt Pavement Layers.” Results of this study showed that ISS was largely dependent on the type of pavement surface (i.e., HMA vs. PCC) receiving tack coat, and pavement surface texture (i.e., milled vs. non-milled). In general, milled HMA surface yielded the highest ISS, followed by new HMA, existing HMA, and PCC surface types. Non-tracking rapid setting tack coats with stiff base asphalt cement exhibited the highest ISS compared to slow setting tack coats. With respect to the effect of service time, ISS increased with service time due to tack coat curing effect and densification of overlays. Laboratory measured ISS values correlated well with short-term cracking performance of field pavements. Results presented herein were part of NCHRP Project 9-40A on the “Field Implementation of the Louisiana Interface Shear Strength Test.”

This paper evaluates the replacement of natural aggregate coarse fraction for recycled concrete aggregate (RCA) in hot mix asphalt (HMA) concrete production, an area in which studies are recent and scarce. Crushed stone coarse aggregates (CSCA) were replaced by RCA with a 30 MPa compressive strength in the following percentages: 0, 25, 50, 75, and 100%, and mixed with asphalt cement (AC) 50-70. Volumetric and mechanical properties resulting from the Marshall mix design method, along with permanent deformation and durability by the moisture-induced damage test (Lottman), were analyzed. The results indicate that, although RCA shows higher absorption, higher Los Angeles abrasion, and lower density than the crushed stone aggregates, the mixtures showed satisfactory results for use as an asphalt concrete surface layer on low-volume roads. Wheel tracking tests presented permanent deformations ranging between 4.4 and 9.3%. It was also perceived as an adhesiveness improvement in the RCA mixture. The resul...

Due to the constant climate change and the high demand of the vehicle fleet, as well as the exponential growth of traffic, there is now a necessity to experiment and include innovative materials to improve the mechanical performance of bituminous mixtures. The use of new additives is an interesting alternative to reduce the different damages generated by traffic loads, climate agents and any other phenomenon; and thus, be able to prolong its useful life. In this research, different additives were evaluated experimentally in a hot mix asphalt with a maximum nominal size of 19 mm (MDC-19). The additives selected as modifiers of the mixes were: hydrated lime (HL), coconut fiber (FC), polypropylene fiber (PP) and grained crumb rubber (GCR). A total of 72 specimens were manufactured; twelve of them were made to determine the optimum asphalt content by using the Marshall methodology and the remaining 60 were made for the experimental evaluation of the bituminous mixtures. The experimental tests carried out were: Marshall test, indirect tension test and particle loss test; these following the INVIAS regulations. From the experimental results, it was found that the modified mixture with HL was the most favorable and promising additive in the hot dense asphalt mixture, This is because it presents improvements in mechanical performance as it has greater resistance to deformation in addition to good stability and less moisture damage, which is a good alternative for the overall performance in the mixture.

Low-volume roads (LVRs) are typically not expected to withstand large amounts of traffic, consequently they have relatively thin pavement structures. However situations can occur when traffic loading rapidly increases, resulting in rapid structural deterioration of the pavement. Examples include resource exploration and production, new industrial facilities, and military operations. Improved evaluation procedures, including computation of pavement structural responses, are needed to accommodate these scenarios. This paper reports recent advances in methods for computing the structural response of LVRs that incorporate viscoelastic asphalt material behavior and accommodate moving loads. Application of layered elastic analysis, using a Hankel transform with numerical integration methods, is popular in several mechanistic-empirical pavement design procedures. This paper describes an application of the collocation method for approximating the creep compliance and viscoelastic solution, which removes the necessity for approximating the Laplace transform inversion. This was coupled with Boltzmann’s superposition principle for moving loads. Comparisons showed that the proposed approximate method matched well with the viscoelastic solution, and with the full-scale instrumented test data of highway pavements. The measured near surface response of a thin LVR test pavement subjected to military truck loads was then modeled to determine the suitability of the approach for LVR. The modeled results for asphalt strain and vertical pressure in the granular layers showed generally good agreement with the measured instrumentation data. The developed structural response model provided a more realistic simulation of flexible pavement viscoelastic material behavior and accommodation of moving loads with similar computational speed to a conventional layered elastic approach.

The management of low-volume rural roads in developing countries presents a range of challenges to road designers and managers. Rural roads comprise over 85 percent of the road network in India. The present study aims at development of deterioration models for the optimum maintenance management of the rural roads under a rural road programme namely Pradhan Mantri Gram Sadak Yojana (PMGSY) in India. Visual condition survey along the selected low-volume rural roads considers parameters like condition of shoulders, drainage features, cross-drainage structures, and camber, and pavement distresses, namely, potholes, crack area, and edge break, are collected for a period of three years. The deterioration models have a significant role in the pavement maintenance management system. However, the performance of a pavement depends on several factors. Cluster analysis can be used to group the pavement sections so that the performance of pavements in different clusters can be studied. Nonhierarchical clustering technique of k-means clustering was considered. Separate deterioration models have been developed for each of the clusters. A comparison of the models developed with and without clustered sections reveals that the clustering of pavement sections are preferred for the efficient rural road maintenance management.

Warm mix asphalt (WMA) is a relatively new and emerging technology for the asphalt industry. It offers potential construction and environmental advantages over traditional hot mix asphalt (HMA). However, WMA must perform at least as well as HMA before it can be used extensively. This study evaluates the performance of WMA mixtures and their corresponding HMA control mixtures obtained from various field sites in the state of Washington. Four WMA technologies are examined, including Sasobit® and three water-foaming technologies, Gencor®, Aquablack™ and ALmix Water Injection. Performance tests are conducted on the field cores to evaluate and compare the rutting, moisture susceptibility, fatigue and thermal resistance of WMA and HMA, respectively. Also, the extracted binders from the field cores are evaluated. In addition, the early-age field performance of WMA and HMA control pavements are compared.