Prediction of Thermal Behavior of Pervious Concrete Pavements in Winter

Because application of pervious concrete pavement (PCPs) has extended to cold-climate regions of the United States, the safety and mobility of PCP installations during the winter season need to be maintained. Timely application of salt, anti-icing, and deicing agents for ice/snow control is most effective in providing sufficient surface friction when done at a suitable pavement surface temperature. The aim of this project was to determine the thermal properties of PCP during the winter season, and to develop a theoretical model to predict PCP surface temperature. The project included a laboratory and a field component. In the laboratory, thermal conductivity of pervious concrete was determined. A linear relationship was established between thermal conductivity and porosity for pervious concrete specimens. In the field, the pavement temperature in a PCP sidewalk installation at Washington State University was monitored via in-pavement instrumentation. Based on the field data, the Enhanced Integrated Climatic Model (EICM) was developed and validated for the site, using PCP thermal properties and local climatic data. The EICM-predicted PCP surface temperature during the winter season agreed well with the field temperature. Overall, the predicted number of days that the pavement surface fell below 32°F agreed well with the number based on field data for 85% of the days. Therefore, the developed model is useful in identifying those days to apply deicer agents. Finally, a regression model using climatic indices was developed for PCP surface temperature prediction in the absence of a more advanced temperature model

Influence of aggregate type and gradation on critical voids in the mineral aggregate in asphalt paving mixtures

The implementation of Superpave has led to concerns with volumetric mix design; in particular, the minimum voids in the mineral aggregate (VMA) requirements, which are based exclusively on nominal maximum aggregate size (NMAS). Achieving the minimum VMA requirement is one of the most difficult tasks in Superpave volumetric mix design. Under current specifications, many otherwise sound mixtures are subject to rejection solely on the basis of failing to meet the VMA requirement;The goal of this research was to validate the existing VMA criterion and to see if including additional aggregate factors would improve it. The work was accomplished in three phases: a literature review; extensive laboratory testing; and statistical analysis of test results;The available literature on the development of the minimum VMA criterion is sketchy; the relationship was originally presented without supporting research or data and the suggestion that it would be modified with experience and test data. The literature review also suggested that the triaxial test was the preferred laboratory test for identifying when a mixture transitions from sound to unsound behavior, i.e., becomes plastic;The laboratory testing involved triaxial testing with the Nottingham Asphalt Tester of 36 mixes with different aggregate properties. ANOVA and linear regression was used to examine the effects of identified aggregate factors on critical state transitions in asphalt paving mixtures and to develop predictive equations;The results clearly demonstrate that the volumetric conditions of an asphalt mixture at the stable/unstable threshold are influenced by a composite measure of the maximum aggregate size and gradation and by aggregate shape and texture. The currently defined VMA criterion, while significant, is seen to be insufficient, by itself, to correctly differentiate sound from unsound mixtures. Based on the laboratory data and statistical analysis, a new paradigm to volumetric mix design is proposed that explicitly accounts for several aggregate factors (gradation, shape, and texture) in predicting the critical VMA of an asphalt paving mixture

THE EFFECTS OF FUNDAMENTAL MIXTURE PARAMETERS ON HOT-MIX ASPHALT PERFORMANCE PROPERTIES

Asphalt pavements are composed of three components: aggregate, asphalt binder, and air. In the process of plant production and on-site construction, the construction quality can vary in the three component and the variability can further affect a pavement\u27s future performance.. This research identifies aggregate gradation, binder content, and air voids content as the fundamental parameters. Understanding the fundamental parameters\u27 influence on the HMA mixture\u27s performance properties can provide valuable information on how to improve the current quality insurance practice. The objective of this study is to conduct well-controlled experiments to investigate how mix gradation, air voids and small range binder content deviation from design binder content can affect the performance properties of asphalt concrete. In this study, three aggregate sources were utilized, and two gradations (fine-graded and coarse-graded) were tested from each aggregate source. Two levels of binder content and air voids content were used to represent the construction variability levels of binder content and density, respectively. The three aspects of mixture performance that were evaluated include rutting, tensile cracking and moisture susceptibility. It is found that aggregate gradation is significant to rutting and IDT performance. In rutting, the gradation effect is aggregate specific. The effect of gradation on ITS can be reflected by the design binder content, which is closely related to the VMA value of the aggregate gradation. Therefore, the rutting performance seems more sensitive to gradation variation than the tensile strength of a mixture. Binder content variation in a permissible range can statistically affect the rutting and IDT strength performance. A \u27binder content window\u27 is determined from a fracture energy point of view; however, the rutting performance should not be compromised. On pavement density variation, the study showed that reducing air voids content can increase the mixtures\u27 engineering properties, both rutting and ITS. Several statistical regression models were developed using the fundamental parameters. The equations can effectively summarize the experimental data set, creating quantitative relationships that can be used to predict the response variables

Alternative Fillers in Asphalt Concrete Mixtures: Laboratory Investigation and Machine Learning Modeling towards Mechanical Performance Prediction

In recent years, due to the reduction in available natural resources, the attention of many researchers has been focused on the reuse of recycled materials and industrial waste in common engineering applications. This paper discusses the feasibility of using seven different materials as alternative fillers instead of ordinary Portland cement (OPC) in road pavement base layers: namely rice husk ash (RHA), brick dust (BD), marble dust (MD), stone dust (SD), fly ash (FA), limestone dust (LD), and silica fume (SF). To exclusively evaluate the effect that selected fillers had on the mechanical performance of asphalt mixtures, we carried out Marshall, indirect tensile strength, moisture susceptibility, and Cantabro abrasion loss tests on specimens in which only the filler type and its percentage varied while keeping constant all the remaining design parameters. Experimental findings showed that all mixtures, except those prepared with 4% RHA or MD, met the requirements of Indian standards with respect to air voids, Marshall stability and quotient. LD and SF mixtures provided slightly better mechanical strength and durability than OPC ones, proving they can be successfully recycled as filler in asphalt mixtures. Furthermore, a Machine Learning methodology based on laboratory results was developed. A decision tree Categorical Boosting approach allowed the main mechanical properties of the investigated mixtures to be predicted on the basis of the main compositional variables, with a mean Pearson correlation and a mean coefficient of determination equal to 0.9724 and 0.9374, respectively

Asphalt Mix Design and performance

Premature flexible pavement distress became a major concern in Indiana. As a result, a study was conducted investigating the major underlying factors. Pavement sections were investigated based on a factorial study with four factors comprised of climate, truck traffic, pavement base type, and wheel path. The distresses evaluated were rutting, thermal cracking and stripping. All were evaluated against control sections with zero distress. The pavement condition of each section was determined. Laboratory tests of field sample included physical properties, dynamic creep and recompaction. Results of the study indicate that the Asphalt Institute mix design criteria identify an asphalt content that is too high. In place densities were found to be inadequate and a recommendation was made to use higher field compactive effort. The USAE Gyratory Testing Machine (GTM) was used in laboratory studies to recompact density and air voids. Testing confirm that the in situ asphalt content was too high. Gap graded gradations were found to be prone to rutting. Benefit is shown in using dynamic modulus to evaluate mixtures. A statistical analysis method, discriminate analysis, was used to accurately predict mixture field performance using laboratory data

Laboratory investigation of fatigue endurance limits in asphalt concrete

It is believed that Hot Mix Asphalt (HMA) mixtures used in long-lasting pavements contain a threshold of strain value below which no fatigue damage occurs. This concept is known as the fatigue endurance limit (FEL). Although previous studies have shown that an endurance limit does exist for HMA mixtures, an established value is yet to be determined, with values varying from 70-400 microstrain (με) based on mixture variability. Traditional FEL vii identification is based on the phenomenological approach, which relates the number of loading cycles to fatigue failure with applied tensile strain and initial stiffness of material. This study determined the FEL of two HMA mixtures, SP-II (coarse mix) and SP-III (fine mix), using the phenomenological approach as well as a fundamental energy based approach, the dissipated energy concept. Results show that the dissipated energy approach estimates higher FEL values for both mix types than those estimated using the phenomenological approach. The FEL values for the SP-II and SP-III mixtures are estimated to be approximately 200 and 300 με respectively. Furthermore, laboratory fatigue failure criterion is defined as the number of loading cycles at which the stiffness of a material reduces by 50%. This study evaluated stiffness-based failure criteria for laboratory fatigue testing using the viscoelastic continuum damage mechanics (VCDM) approach. Results show that fatigue failure criterion of the VCDM approach correlates well with the stiffness-based fatigue failure criterion. In addition, the effect of polymer-modified binder on the FEL of HMA materials is investigated. The addition of modified binder to the SP-II mixture reduced the estimated FEL by 27%. On the other hand, the addition of modified binder to the SP-III mixture improved its estimated FEL value by 30%

Laboratory and Field Evaluation of Modified Asphalt Binders and Mixes for Alaskan Pavements

In order to properly characterize modified asphalt binders and mixes for Alaskan pavements, this study evaluated properties of 13 asphalt binders typically used in Alaska from three different suppliers, and 10 hot mix asphalt (HMA) mixtures which were either produced in the lab or collected from existing paving projects in Alaska. Various binder and mixture engineering properties were determined, including true high binder grades, complex modulus (G*), and phase angle (δ) at high performance temperatures, multiple stress creep recovery rate and compliance, bending beam rheometer stiffness and m-value, Glover-Rowe parameter, ΔT, rheological index, and crossover frequency for binders, and rut depth, critical strain energy release rate (Jc), Indirect tensile (IDT) creep stiffness and strength for mixtures. Binder cracking temperatures were determined using asphalt binder cracking device. Mixture cracking temperatures were determined with IDT creep compliance and strength data. It was found that rutting and cracking resistances of the mixtures with highly modified binders were better than the mixture with unmodified asphalt binder (PG 52-28). Future recommendations for highly modified asphalt binders applications and research were provided based on laboratory testing results and field survey evaluation

Comprehensive Evaluation of Rutting Performance of Asphalt Concrete Mixtures

Rutting is the permanent deformation along the wheel paths of an asphalt pavement caused by repeated traffic loading. It is considered as one of the primary distresses of asphalt pavements. Recently, Hamburg Wheel Tracking Device (HWTD) has shown to measure the rutting performance of an asphalt mixture in the laboratory. In this study, this device has been used to measure rutting of asphalt concrete (AC) and relate them with the mixture’s dynamic modulus. To this end, the rut deformation of AC mixtures were modeled in this study using a semi-empirical |E*|-based rut predictive model based on the HWTD rut depth data of 25 mixes. This model utilizes creep compliance (D(t)) interconverted from laboratory tested DM (|E*|) results to predict rut depth. The model provides a fairly good prediction of AC rutting performance. Despite the fact that asphalt binder make up 4 to 8% of a pavement mix structure, it provides a level of rigidity and structural bonding which holds the total pavement mixture together as a solid body. However, with higher traffic densities, binder flows and dissipates energy. As a result, pavement rutting at high temperatures occur due to thermal susceptibility of asphalt. In this study, the binder’s contribution to rutting performance was assessed based on the evaluation of rheological rut properties of five warm mix modified mixtures. For this purpose, Frequency Sweep (FS), Multiple Stress Creep Recovery (MSCR), and Zero Shear Viscosity (ZSV) tests were conducted on extracted binders using Dynamic Shear Rheometer (DSR) device at a 50°C temperature to determine binder rut parameters. In this study, five widely used rheological rut parameters are examined: the Superpave® rutting parameter (G*/sinδ), Shenoy parameter (G*/(1-(1/sinδ.tanδ))), Zero Shear Viscosity (η0), Non-recoverable Creep Compliance (Jnr), and Percent Recovery (%R). Comparing these rheological rut parameters and HWDT results, it was found that warm mix modified mixtures exhibited increased rutting resistance compared to the control hot-mix asphalt