Developing QC/QA Specifications for Hot Mix Asphalt Concrete in Illinois

In this study, the rut susceptibility of warm mix asphalt (WMA) was evaluated by laboratory material characterization tests that included repeated creep testing using universal testing machine (UTM-5P) on WMA and conventional hot mix asphalt (HMA) mixtures. With regard to the fact that aggregate makes up a high proportion of volume and mass of mixtures, this parameter is considered as an important constituent of asphalt concrete. So, one aggregate source, three gradations and three different percentages of Sasobit® content were used to manufacture mixtures. Four creep parameters, namely, flow number (FN), creep stiffness (CS), creep strain slope (CSS) and secondary initial point (SIP), were used to analyze the test results. The primary objective of this research effort was to conduct a comparison between permanent deformation of HMA and WMA mixtures and also to evaluate the effect of aggregate gradation and different Sasobit® contents on introduced creep parameters. Analysis of data shows that the creep behavior of both asphalt mixtures (HMA and WMA) was influenced by aggregate gradation and also by Sasobit® content. Comparison of test results between HMA and WMA exhibits that, in general, WMA mixtures exhibit improved rut resistance compared to conventional mixtures. Also, it is concluded that creep strength of WMA mixes are more susceptible to change in aggregate gradation compared to HMA mixes, while increasing in Sasobit® content produce more stable mixtures. In addition, it is determined that finer aggregate gradations were more influenced by change in the Sasobit® content.

PurposeThe ability to measure and assess “quality” is essential in building and maintaining a safe and effective transportation system. Attaining acceptable quality outcomes in transportation projects has been a reoccurring problem at both the federal and state levels, at least partially, as a result of poorly developed, inefficient or nonexistent quality assurance/quality control (QA/QC) processes. The purpose of this paper is to develop and implement a new QA/QC process that focuses on a novel double-bounded performance-related specification (PRS) and corresponding pay factor policy that includes both lower and upper quality acceptance and payment reward boundaries for bridge concrete.Design/methodology/approachThe authors use historical data to design different payment scenarios illustrating likely industry responses to the new PRS, and select the single scenario that best balances risk between the agency and industry. The authors then convert that payment scenario to a pay factor schedule using a search heuristic and determine statistical compliance with the PRS using percent-within-limits (PWL).FindingsThe methodology offers an innovative approach for developing an initial set of pay factors when lifecycle cost data are lacking and the PRS are new or modified. An important finding is that, with a double-bounded PRS, it is not possible to represent pay factors using the simplified table PWL currently employed in practice because each PWL value occupies two separate positions in the payment structure – one above the design target and one below it. Therefore, a more detailed set of pay factors must be employed which explicitly specify the mean sample value and the design target. The approach is demonstrated in practice for the Agency of Transportation in state of Vermont.Research limitations/implicationsThe authors demonstrate a novel approach for developing a double-bounded PRS and introduce a payment incentive/disincentive policy with the goal of improving total product quality. The new pay factor policy includes both a payment penalty below the contracted price for failing to meet a specified performance criterion as well as a payment premium above the contracted price that increases as the sample product specification approaches an “ideal” design value. The PRS includes both an upper and lower acceptance boundary for the finished product as opposed to only a lower tail acceptance boundary, which is the traditional approach.Practical implicationsThe authors illustrate a research collaboration between academia and a state agency that highlights the role academic research can play in advancing quality management practices. The study involves the use of actual product performance data and is operational as opposed to conceptual in nature. Finally, the authors offer important practical insights and guidance by demonstrating how a new PRS and pay factor policy can be developed without the use of site-specific historical lifecycle cost (LCC) data that include detailed manufacturing, producing and placement cost data, as data related to product performance over time. This is an important contribution, as the development and implementation of pay factor policies typically involve the use of historical LCC data. However, in many cases, these data are not available or may be incomplete.Social implicationsWith the new PRS and pay factor schedule, the Agency expects shrinkage and cracking on bridge decks to decrease along with overall maintenance and rehabilitation costs. A major focus the new PRS is to actively involve industry partners in quality improvement efforts.Originality/valueThe authors focus on a major modification to an existing QA/QC process that involves the development of a new PRS and an associated pay factor policy undertaken by the Vermont Agency of Transportation. The authors use empirical data to develop a novel double bounded PRS and payment schedule for concrete and offer unique operational/practical insight and guidance by demonstrating how a new PRS and pay factor policy can be developed without the use of site-specific historical LCC. Typically, PRS for in-place concrete have only a lower tail acceptance boundary.

Quantification of the fatigue life of warm mix asphalt (WMA) is challenging due to various factors such as the extent of aging and moisture susceptibility, to mention a few. Hydrated lime as an antistripping material can enhance the fatigue life of moisture conditioned WMA mixture; however, due to the filler effect of lime, the fatigue life can be reduced. In this investigation, samples of hot mix asphalt (HMA) and WMA with and without hydrated lime were subjected to fatigue testing using four-point bending at three strain levels (400, 600, and 800 microstrain) for unconditioned and moisture damaged conditions. The collected data was analyzed appealing to various post-processing methods, and it was seen that the beneficial effect of warm mix additives or hydrated lime was seen at lower strain level (400 microstrain) and not at higher strain levels (600 and 800 microstrain) based on the evolution of flexural stiffness and energy dissipation.

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.

This study evaluates the effects of asphalt binder's performance grade (PG) on the dynamic modulus (|E*|) mastercurves of Superpave (SP) mixes typically found in the state of New Mexico. A total of three hot-mix asphalt (HMA) mixes were collected. They were produced from three different binder grades and one with aggregate gradation containing 35% of reclaimed asphalt pavement (RAP). Field collected HMA mixes were compacted and cored to cylindrical specimens. The specimens were then tested for dynamic modulus at five different temperatures and six different frequencies of loading. Master curves for all the HMA mixes were then developed and compared. A noticeable amount of divergence was found while comparing these mastercurves among each other. It was observed that stiffer binder produces HMA concrete with high dynamic modulus value. However, this trend is not always true. In the case of HMA mixes with RAP, the dynamic modulus of the HMA increases considerably, although the mix has a softer binder. The dynamic modulus of these RAP-included HMA materials could be as high as twice the dynamic modulus of HMA without RAP.

Warm mix asphalt (WMA) is increasingly recognised as a green paving technology in terms of energy saving and emission reduction. The reduction in mix production temperature associated with the WMA additives is very desirable from the environmental aspect. However, researchers and practitioners desire a comparable performance with hot mix asphalt (HMA). The major issue with WMA is their moisture susceptibility especially in the pavement early life. Therefore, this study aims at investigating moisture susceptibility of WMA using both laboratory characterisation and field performance compared to HMA. Three mixtures were investigated, namely; HMA mixture, foaming and Evotherm WMA mixture. The laboratory tests included; resilient modulus (M R), Indirect Tensile test, and Hamburg wheel tracking test. Test sections on Farm to Market FM 973 Highway near Austin, Texas, were constructed using these three mixtures. The results of field performance monitoring for five years are represented in this paper. Laboratory test results revealed small differences between measured dry and wet tensile strength and M R of HMA and WMA which shows some improvements using antistripping agents. The field performance evaluation showed that the Evotherm WMA mixture had the least transverse and reflected cracks while the HMA performed better in both ravelling and longitudinal cracking.

A number of warm mix asphalt (WMA) technology has been developed to allow asphalt mixtures to be produced and compacted at a significantly lower temperature. This eco-friendly technology has been spread so quickly in the world. Recently, an innovative WMA additive has been developed to reduce mixing and paving temperatures applied in asphalt paving process by Korea Institute of Construction Technology (KICT) and Kumho Petrochemical in Korea. It is named low energy and low carbon-dioxide asphalt pavement (LEADCAP), which is an organic additive of a wax-based composition including crystal controller and artificial materials. In this study, WMA mixtures using LEADCAP additive along with the control hot mix asphalt (HMA) mixtures were evaluated with respect to their moisture susceptibility and rutting resistance in the laboratory. The WMA pavement using LEADCAP additive along with a conventional HMA pavement were evaluated with respect to their density and air void in the field trials. Based on the limited laboratory and field test results, WMA mixtures using LEADCAP additive is superior to HMA mixtures in the moisture susceptibility and rutting resistance. The LEADCAP additive is found effective in producing and compacting WMA mixtures that are comparable to HMA mixtures.

This paper presents the results of tests of warm-mix asphalt (WMA) mixtures designed for airfield pavements. The study was conducted in two phases. The first phase included laboratory tests on 11 WMA technologies. The tests in Phase 2 were performed on three WMA mixtures and one hot-mix asphalt (HMA) mixture produced in an asphalt plant. The evaluation included performance tests to assess WMA susceptibility to permanent deformation and moisture damage compared with that of HMA produced with the same aggregate blend. Test results indicated that WMA potentially was a viable product for surface mixtures on airfield pavements. Although WMA exhibited poorer performance than HMA in moisture damage tests on laboratory-produced specimens, the plant-produced mix indicated little difference compared with HMA. Rutting potential for WMA was somewhat greater than for HMA for mixtures produced both in the laboratory and in an asphalt plant according to asphalt pavement analyzer and Hamburg wheel tracking tests. Differences in performance of WMA mixtures were not attributed to a specific WMA technology category. Variations in performance test results between laboratory-produced specimens and plant-produced specimens were noted and indicated a need to require performance testing as part of a comprehensive quality assurance plan.

Aggregate gradation and shape properties are known to affect pavement mechanistic response and performance significantly. Under repeated traffic loading, aggregate particles in pavement courses are routinely subjected to degradation through attrition, impact, grinding, and polishing mechanisms, which alter their shape and size properties. Machine vision provides an objective and quantitative measurement of aggregate particle shape or morphological properties, including flatness and elongation, angularity, and surface texture. This paper focuses on the effectiveness of two advanced and validated aggregate imaging systems: an enhanced University of Illinois aggregate image analyzer (E-UIAIA) and a second-generation aggregate imaging system (AIMS-II)—for capturing changes in shape and size properties of aggregate particles caused by breakage, abrasion, and polishing actions. The micro-Deval apparatus was used in the laboratory to evaluate field degradation and polishing resistance of 11 aggregate materials with different mineralogical properties, collected from throughout Illinois and neighboring states. More than 26,000 particles were scanned with both imaging systems at various time intervals, and changes in aggregate morphological indexes were recorded. Despite differences in image acquisition and processing capabilities, both E-UIAIA and AIMS-II successfully quantified changes in morphological properties of particles from the micro-Deval tests. However, AIMS-II more closely reflected historical data on aggregate frictional properties obtained by the Illinois Department of Transportation. The imaging results were used to develop regression-based statistical models for determining aggregate polishing and degradation trends by considering both rate and magnitude of changes in shape properties.

Moisture damage is one of the major concerns for warm-mix asphalt (WMA) because it is hypothesised that the reduction in mixing temperature could adversely affect the moisture sensitivity of WMA. The aggregate type and their properties are also one important factor affecting the moisture damage of WMA. This study focused on understanding the effect of aggregate structure and its physical properties on the mechanism of moisture damage in WMA. This study evaluated the moisture sensitivity of hot-mix asphalt (HMA) and WMA as reflected in the permanent deformation. The effects of aggregate gradation and aggregate types on the moisture damage were also evaluated. The results from this study show that WMA is more resistant to permanent deformation than HMA as indicated by lower permanent strain rate and higher flow number (FN). Gradation has an effect on the permanent deformation in granite and slag mixes due to the difference in aggregate properties. WMA is more sensitive to moisture damage than HMA as shown in lower ratios of FN and permanent deformation rate. Fine-graded mixtures appear to have greater resistance to moisture damage than coarse-graded mixtures for both HMA and WMA. The result could be due to the different structure of air void distribution in the mixes of different gradation. It was found that the proper selection of aggregate type and aggregate structure could reduce the moisture damage problem of WMA.

This study focused on the fatigue behaviour of warm mix asphalt (WMA) based on the dissipated energy (DE) approach. Two conventional binders consisting of 60/70 and 85/100 penetration-grade bitumens were used to prepare the control mix. WMA was prepared by incorporating 2% Sasobit by weight of bitumen. First, the basic properties of WMA containing optimum bitumen content were compared with those of control hot mix asphalt (HMA). The main laboratory programme included four-point flexural fatigue test that was accomplished at different strain levels of 250, 500, 750 and 1000 microstrain. The studied WMA had comparable Marshall stability and indirect tensile strength to those of control HMA. Furthermore, based on the resilient modulus test results, the temperature susceptibility of WMA was slightly more than that of the control mix. Fatigue lives of studied mixes were evaluated using the conventional fatigue curves that were developed based on the initial strain level. Comparison between these curves revealed the predominant fatigue behaviour of WMAs at different examined strain levels. The initial DE and the cumulative DE of WMAs were lower than those of HMAs. The latter issue justifies the predominant fatigue response of WMA. By considering the DE curve, the ratio of dissipated energy change (RDEC) was calculated. Afterward, the plateau value (PV) was determined using the moving average of fatigue data in the plateau stage of the RDEC curve. Finally, PV-based fatigue models were developed which could precisely estimate the fatigue life regardless of the mix type and testing condition.

Hot Mix Asphalt (HMA) has long been the main material for flexible pavement, and it is mixed and compacted at high temperatures, usually between 150 and 170 degrees Celsius. HMA has been valued for its durability and strength for a long time, but its production process leads to high fuel consumption and emissions of greenhouse gases. Additionally, Short-term aging of the materials is a major concern linked to HMA. Over the past few years, countries around the world have been moving towards making construction more sustainable, which has led to the creation of Warm Mix Asphalt (WMA) technologies. WMA can be produced and compacted at temperatures that are 20–40 degrees lower than those used for HMA which saves energy and reduces emissions without affecting the quality of the pavement. Adding Aspha-min, a synthetic zeolite, is a key technology used to help bitumen foam during WMA production. As a result, aggregates are more easily coated and become more compactable at lower temperatures, which also helps to reduce the amount of energy used. While several studies have examined the performance of Aspha-min modified WMA, no study has evaluated its behavior under Sri Lankan environmental and operational conditions. Moreover, the existing literature does not present a consistent trend regarding the performance impact of Aspha-min. This study focuses on evaluating the performance of Aspha-min modified WMA under local environmental and operational conditions. The primary objective is to determine the optimal dosage of Aspha-min and mixing temperature that would provide performance comparable to conventional HMA while offering environmental benefits. For this purpose, the study tested three Aspha-min dosages, which are 0.25%, 0.30%, and 0.35% by weight of asphalt mix at three mixing temperatures: 125 °C, 130 °C, and 135 °C. A control HMA sample was also made at 150 °C of mixing temperature for comparison. Specimens were prepared and evaluated using the Marshall mix design method, following the requirements of ASTM standard specifications. The main performance parameters analyzed were Marshall stability, bulk specific gravity (Gmb), and air void content. The results were checked against the SSCM guidelines for wearing course applications in Sri Lanka to assess the suitability of each Aspha-min dose and mixing temperature. The results showed that a mix with 0.30% Aspha-min and a mixing temperature of 130 °C gave the best combination of workability, stability and void structure. This mix achieved a high Marshall stability value, acceptable density values, and air voids within the recommended range. Furthermore, the compaction properties of the Aspha-min mix were similar to those of the standard HMA mix which means that Aspha-min did not negatively impact density or durability. The research shows that using Aspha-min modified WMA is a possible and lasting choice for constructing flexible pavements in Sri Lanka. Because it reduces the production temperature by up to 20 °C, it helps save fuel and cut emissions, making construction more environmentally friendly. In addition, the optimized mix guarantees the structure’s strength, making it suitable for use in local roads. Future efforts may consist of long-term testing in the field and cost analysis to confirm that large-scale adoption is feasible.

Despite the environmental and compaction benefits of warm mix asphalt (WMA), several researchers have expressed concerns over laboratory and field performances of WMA mixes. In this study, a wide range of laboratory tests, namely, dynamic modulus, creep compliance, fatigue, moisture damage, and rutting, was conducted to evaluate the performance of different types of WMA mixes. For this purpose, three WMA mixes, consisting of one mix produced using a zeolite-based WMA additive (containing water), one surface course mix, and one base course mix, the latter two produced with a chemical-based WMA additive with surfactant technology, were collected from different field projects in Texas. In addition, three hot mix asphalt (HMA) mixes with aggregate gradations similar to those of the collected WMA mixes were produced in the laboratory to compare the performance of WMA and HMA mixes. Overall, the WMA mixes yielded lower stiffness, reduced potential of low-temperature cracking, lower fatigue resistance, and a higher rutting potential compared with their HMA counterparts. However, a mixed trend of moisture-induced damage potential was observed for WMA and HMA mixes, when evaluated using retained tensile strength ratio (TSR) and stripping inflection point (SIP) obtained from the Hamburg wheel tracking (HWT) test. In other words, no correlation was found between TSR and SIP values, indicating that passing a TSR test does not guarantee better performance of a mix when tested using an HWT. The results from this study reveal that performance of a WMA mix widely depends on the technology and the type of other additives (e.g. anti-stripping agent) used. The findings of this study are expected to be useful to pavement professionals to better understand the performance of WMA mixes and to develop a database of input parameters for the Mechanistic-Empirical Pavement Design Guide.

As the construction industry continues to evolve globally, there is a need to develop best practices geared towards achieving sustainable construction. Asphalt concrete’s demand has been increasing steadily with an estimated global demand of 122.5 million tons in 2019. This is driven primarily by the growth in construction activities in developing countries as each country works towards enhancing its transportation facilities to cater to the ever-expanding population. Hence, there are needs to develop newer and more efficient means of asphalt consumption. One of such is identifying cheaper or waste materials for use in Asphalt production. This study, therefore, examined the viability of waste marble dust (WMD), an industrial waste produced during the shaping and polishing of marble blocks and also during its extraction from the mines, as a mineral filler in Hot-mix asphalt (HMA) concrete. Engineering properties such as Marshall stability and flow, Void characteristics, Indirect tensile strength and Tensile strength ratio properties were examined. It was observed that the addition of WMD steadily increased the Marshall Stability and indirect tensile strength values and lowered the voids percentages. The study’s major finding is that waste marble dust is highly suitable as a mineral filler in HMA and a 3% by volume addition of WMD in HMA at 4.5% binder content produced the most optimal mix for use in road pavements.

Currently the warm mix asphalt production is increasingly being adopted in road construction. This technology allows for lower production and paving temperatures for asphalt pavements from 30°C to 50°C. Such a significant temperature reduction contributes to lower production costs and also reduces heat emissions into the atmosphere, which is crucial for environmental protection. One of the most important functional characteristics of road pavement layers is their fatigue life, which can be improved by adding fibers to asphalt mixtures. Aramid (AR), glass (GL), and polymer-basalt (PB) fibers are often used for dispersed reinforcement of asphalt mixtures. This paper analyzes the results of tests on hot mix asphalt mixtures containing these fibers, determining their impact on fatigue life. Polymer-basalt fibers were selected for further testing, as they have a very favorable effect on the fatigue resistance of asphalt concrete (AC) and high modulus asphalt concrete (HMAC) mixtures. The important material, technological and construction problem is to determine the effectiveness of adding fibers to asphalt mixtures in warm mix technology. The article presents the results of research on an innovative technology for the production and paving of asphalt mixtures with the simultaneous use of a selected polymer-basalt fibers, a binder fluxing agent in the form of an ecological bio-derived additive (bio-flux) and the process of foaming asphalt with water, which allows the production of a mineral-asphalt composite at a reduced temperature and with improved technical parameters. To confirm their high functional properties, this paper presents fatigue test results of samples of asphalt mixtures intended for the wearing course and the subbase course with the addition of polymer-basalt fibers, prepared in the laboratory and collected from an experimental road section. The test results showed that the use of the technology of producing and paving warm mix asphalt AC 11 for the wearing course and HMAC 22 for the subbase course, using polymer-basalt fibers, is highly beneficial in terms of ensuring high fatigue life.