Feipeng Xiao

Laboratory Investigation of Moisture Damage in Warm-Mix Asphalt Containing Moist Aggregate

In recent years, rising energy prices, global warming, and more stringent environmental regulations have generated interest in warm-mix asphalt (WMA) technologies as a means to decrease energy consumption and emissions associated with conventional hot-mix asphalt. In this study, a laboratory investigation was conducted of moisture damage in WMA mixtures containing moist aggregates. Indirect tensile strength (ITS), tensile strength ratio, deformation, and toughness tests were performed to determine the mixtures’ moisture susceptibilities. The experimental design included two percentages of moisture content (0% and ∼0.5% by weight of the dry mass of the aggregate), two WMA additives (Asphamin and Sasobit), and three aggregate sources. In this study 15 mix designs were performed, and 180 specimens were tested. Test results indicated that, as expected, dry ITS values were affected by aggregate moisture and hydrated lime contents, whereas a WMA additive did not significantly alter the dry ITS and toughness values. Statistical analysis showed no significant differences in the wet ITS values of WMA mixture of three types of mixtures (control, Asphamin, and Sasobit) under identical conditions (same moisture and lime contents). Statistical analysis also showed that wet ITS values, generally, were statistically different for mixtures made with various aggregate sources. The deformation resistance values of mixtures containing moisture were lower than those of mixtures made with dry aggregate. However, the results indicated that the addition of hydrated lime increased the deformation resistance of all mixtures.

Evaluation of Rutting Resistance in Warm-Mix Asphalts Containing Moist Aggregate

In recent years, rising energy prices and more stringent environmental regulations have resulted in an interest in warm-mix asphalt (WMA) technologies to decrease the energy consumption and emissions associated with conventional hot-mix asphalt production. In this study, the objective was to conduct a laboratory investigation of rutting resistance in WMA mixtures containing moist aggregates. Rut depth, weight loss, and gyration number of dry and conditioned specimens were measured for all of the mixtures. The experimental design included two aggregate moisture contents (0% and ∼0.5% by weight of the dry mass of the aggregate), two lime contents (1% and 2% lime by weight of dry aggregate), three WMA additives (Aspha-min, Sasobit, and Evotherm), and three aggregate sources. Thirty-six mixtures were prepared, and 216 specimens were tested in this study. Test results indicated that the aggregate source significantly affects the rutting resistance regardless of the WMA additive, lime content, and moisture content. In addition, rut depth of the mixture containing moist aggregate generally satisfies the demand of pavement performance without additional treatment. The mixture with Sasobit additive exhibited the best rutting resistance. The mixtures containing Aspha-min and Evotherm additives generally showed a rut resistance similar to that of the control mixture.

Influence of Antistripping Additives on Moisture Susceptibility of Warm Mix Asphalt Mixtures

Rising energy prices, global warming, and more stringent environmental regulations have resulted in an interest in warm mix asphalt (WMA) technologies as a means to decrease the energy consumption and emissions associated with conventional hot mix asphalt production. However, the utilization of the hydrated lime and liquid antistripping agents (ASA) in WMA mixture makes these issues more complicated. The objective of this study was to investigate and evaluate the moisture susceptibility of the mixtures containing ASA and WMA additives. The experimental design for this study included the utilizations of one binder source (PG 64-22), three ASA additives and control, two WMA additives and virgin, and three aggregate sources. A total of 36 types of mixtures and 216 specimens were fabricated and tested in this study. The performed properties include indirect tensile strength (ITS), tensile strength ratio (TSR), flow, and toughness. The results indicated that the hydrate lime exhibits the best moisture resistance for WMA mixtures, the liquid ASA additives can increase the ITS values of the mixtures but the liquid ASA generally exhibits a weak moisture resistance compared to the hydrate lime regardless of WMA and aggregate types in this study. In addition, the wet ITS values of mixtures containing WMA additives were lower than that of the mixtures without WMA additives.

Laboratory investigation of moisture damage in rubberised asphalt mixtures containing reclaimed asphalt pavement

In many parts of the world, highway officials are utilising crumb rubber and reclaimed asphalt pavement (RAP) in order to save money, protect the environment, and improve the life of asphalt pavement. However, due to the use of these materials, the effects of moisture damage should be investigated for rubberised asphalt concrete (RAC) mixtures containing RAP. The objective of this research involved investigating the moisture susceptibility of RAC containing RAP. The testing conducted included the determination of binder viscosity, toughness and indirect tensile strength (ITS) analysis. Several mixtures containing different crumb rubber types, two different RAP sources and various percentages of rubber and RAP were evaluated. The results indicated that, in general, the additional of RAP was beneficial in improving the ITS values and reducing the moisture susceptibility of the mixture although the addition of crumb rubber had a slightly negative effect.

Influence of Carbon Nanoparticles on the Rheological Characteristics of Short-Term Aged Asphalt Binders

Nanotechnology has the potential to create many new materials and devices with wide-ranging purposes. Nano-sized particles have been used in numerous applications to improve the properties of various materials. The utilization of nanotechnology in civil engineering is expected to increase and may become an attractive alternative for asphalt binder modification. The objective of this study was to investigate and evaluate the rheological properties of binders containing various percentages of carbon nanoparticles after a short-term aging process. The experimental design for this study included five binder sources (three grades including PG 64-22, PG 64-16, and PG 52-28), three nano percentages (0.5, 1.0, and 1.5% by weight of the virgin binder), and control binders. The rheological characteristics of the rolling thin film oven (RTFO) binders, including failure temperature, performance grade, creep and creep recovery, viscous flow, and frequency and amplitude sweep, were tested. The results of the experiments indicated that the addition of nanoparticles was helpful in increasing the failure temperature, complex modulus, and elastic modulus values and in improving rutting resistance of the RTFO binder. The phase angle of the binders generally decreased with an increase in nano content and RTFO aging procedure. In addition, statistical analysis indicated that the asphalt binder source plays a key role in determining the rheological properties because of significant evaluations.

Utilization of Foaming Technology in Warm-Mix-Asphalt Mixtures Containing Moist Aggregates

In this study, the objective was to conduct a laboratory investigation of moisture susceptibility and rutting resistance of warm mix asphalt (WMA) mixtures containing moist aggregates using a foaming technology. Gyration number of various samples, indirect tensile strength (ITS), tensile strength ratio (TSR), rut depths of dry and conditioned specimens, as well as deformation (flow) were measured for all mixtures. The experimental design included two aggregate moisture contents (0% and ~0.5% by weight of the dry mass of the aggregate), two lime contents (1% and 2% lime by weight of dry aggregate), one liquid anti-stripping agent (ASA) and non ASA, three foaming water contents (2, 3, and 4%) with control, and two aggregate sources. A total of 42 mixtures were used and 420 specimens were tested in this study. The test results indicated that the aggregate source significantly affects the ITS and rutting resistance regardless of the foaming water content, ASA, and aggregate moisture content. In addition, the ITS and rut depth of some foamed mixture containing moist aggregate satisfies the demand of pavement performance without additional treatment while some mixture needs a completely dry aggregate or additional treatments. The mixture with various hydrated lime contents exhibited similar rutting and moisture resistance under dry and wet conditions. The liquid ASA used in this study is not recommended to use in foaming WMA mixture with moist aggregates as it is sensitive to moisture.

Artificial Neural Network Approach to Estimating Stiffness Behavior of Rubberized Asphalt Concrete Containing Reclaimed Asphalt Pavement

Accurately predicting the stiffness of asphalt pavements is difficult due to the complex behavior of materials under various loading, pavement structure, and environmental conditions. This study explores the utilization of the artificial neural network (ANN) in predicting the stiffness behavior of rubberized asphalt concrete mixtures with reclaimed asphalt pavement (RAP). A total of 296 asphalt mixture beams were constructed from two different rubber types (ambient and cryogenic), two different RAP sources, and four rubber contents (0, 5, 10, and 15%). All samples were tested at two different testing temperatures of 5 and 20°C. The regression statistical method was used to predict the stiffness behavior of these mixtures via the 7 input variables covering the material engineering properties of the asphalt beams. In addition, the data were organized into 5 independent variables and one dependent variable (the stiffness values of the modified mixture beams) in ANN models. Results showed the ANN techniques to be more effective in predicting the fatigue life of the modified mixture than traditional regression-based prediction models.

Long-term ageing influence on rheological characteristics of asphalt binders containing carbon nanoparticles

Nano-sized particles have been used in numerous applications to improve properties of various materials. The utilisation of nanotechnology in civil engineering area is relatively new and its use and applications are expected to increase rapidly. The objective of this study was to investigate and evaluate the rheological properties of binders containing various percentages of carbon nanoparticles after a long-term ageing process. The experimental design for this study included the utilisations of five binder sources (three grades of PG 64-22, PG 64-16 and PG 52-28) and four nano percentages (0.0, 0.5, 1.0 and 1.5% by weight of the virgin binder). The rheological characteristics of these pressurised aged vessel (PAV) binders were tested including G* value, creep and creep recovery, and frequency and amplitude sweep at an intermediate temperature and deflection, stiffness and m-value at a low temperature as well. The results of the experiments indicated that the addition of nanoparticles does not increase the G* values and does have an obvious effect on complex modulus, phase angle under a frequency sweep test. However, nanoparticles have a slight effect on creep angle and compliance of a binder. Moreover, at a low tested temperature, the experimental results indicate that the nanoparticles have no effect on deflection, stiffness and m-value of PAV residue. Furthermore, statistical analysis indicates that the asphalt binder source and grade rather than nanoparticles play a key role in determining the rheological properties

Evaluation of High Temperature Rheological Characteristics of Asphalt Binder with Carbon Nano Particles

In recent years, nano technology, a relatively new field in science dealing with structures that are on the nano scale, have been used in numerous applications to improve properties of various materials. However, the use of this technology has not been explored in detail in the area of asphalt binder materials. The objective of this study was to investigate and evaluate the high temperature rheological properties of the binders containing various percentages of carbon nano particles. The experimental design for this study included the utilization of five binder sources, three binder grades (PG 64-22, PG 64-16, and PG 52-28), one type of nano particle, and four percentages of nano particles (0.0 %, 0.5 %, 1.0 %, and 1.5 % by weight of the virgin binder). Some of the rheological characteristics of these binders were obtained, including rotational viscometer (four testing temperatures of 120, 135, 150 , and 165°C) and dynamic shear rheometer. The results of the experiments indicated that the addition of nano particles was helpful in increasing the viscosity, failure temperature, phase angle, and viscous and elastic modulus values and in improving the rutting resistance of the binders. On the other hand, the binder sources and grades generally influenced their rheological properties as the nano particles were added to the asphalt binder.

Resilient Modulus Behavior of Rubberized Asphalt Concrete Mixtures Containing Reclaimed Asphalt Pavement

ABSTRACT The resilient modulus is the modulus to be used with the elastic theory during any analysis of a flexible pavement. It is well known that most paving materials (e.g., asphalt pavements) are not elastic but experience some permanent deformation after each load application. With respect to the complexity of the Rubberized Asphalt Concrete (RAC) containing Reclaimed Asphalt Pavement (RAP), the Indirect Tensile Strength (ITS) and resilient modulus evaluation of modified mixtures are important to understand. The aging of binder containing crumb rubber obviously alters the visco-elastic and plastic characteristics of the modified mixtures. The deformation of the mixture under repeated loading, nearly completely recoverable, should also be considered. The experimental design included the use of two aggregate sources, one rubber type (ambient), four rubber contents (0%, 5%, 10%, and 15%), one crumb rubber size (-40 mesh [-0.425 mm]), and four RAP contents (0%, 15%, 25%, and 30%). The findings indicated that an increase in the rubber content in the modified mixture leads to a decrease in ITS and resilient modulus values regardless of rubber content, and this increase also improves the aging resistance and increases the viscous characteristics of the modified binder. However, as RAP content increased, not only the viscosity and G*sinδ values of the modified binder increased, the ITS and resilient modulus values of the modified mixtures also increased.