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Moisture damage in flexible pavements might cause stripping in asphalt pavements and ultimately result in premature failure. Warm mix asphalt (WMA) technology as a means to decrease the energy consumption and emissions associated with conventional hot mix asphalt production is broadly being used recently. However, the utilisation of the hydrated lime and liquid anti-strip additives in WMA mixtures makes these issues more complicated. The objective of this study was to investigate and evaluate the moisture susceptibility of mixtures containing anti-stripping agents (ASAs) and WMA additives after long-term saturated durations. The experimental design for this study included the utilisations of one binder source (PG 64-22), three ASA additives and control, two WMA additives and hot mix, and three aggregate sources. A total of 36 types of mixtures and 540 specimens were fabricated and tested in this study. The performed properties included indirect tensile strength (ITS), tensile strength ratio, flow and toughness. The results indicated that the aggregate source has an effect on dry ITS and flow values but had no effect on wet ITS, wet flow and toughness values. In addition, hot mixture generally had higher dry and wet ITS values, and there were significant differences in flow and toughness values between hot and warm mixtures. Moreover, the hydrated lime exhibited the best moisture resistance in WMA mixtures; the liquid ASA additives could increase the ITS values of mixtures but exhibited a weak moisture resistance in this study. Furthermore, the storage and saturated duration generally had no effect on ITS values, and statistical analysis results did not show any differences among these mixtures. [ABSTRACT FROM AUTHOR]

The present study is focused on using warm mix asphalt (WMA) technology in stone matrix asphalt mixtures and investigated in detail on the moisture sensitivity of these mixtures using three different types of WMA technologies. The experimental design involved three sources of aggregates (A, B and C) and three WMA technologies using additives Asphamin®, Sasobit® and Evotherm® technology. Test results indicated that 13 mixtures failed to meet the minimum tensile strength ratio requirement of 85%, and all mixtures tested met the minimum wet indirect tensile strength (ITS) value of 448 kPa (65 psi) as per SCDOT specifications. Statistical analysis showed that there was significant difference in the wet ITS values between aggregate A (micaceous granite) and granite (C) for all the mixtures studied. Statistical analysis showed that except for two mixtures, there were no significant differences in the wet ITS values of WMA mixtures amongst four types of mixtures under identical conditions. The mixtures containing over 15% rubber (by weight of virgin binder) produced similar resistance to moisture susceptibility compared with mixtures made with PG 76-22+fibres. [ABSTRACT FROM PUBLISHER]

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 [ABSTRACT FROM PUBLISHER]

The primary objective of this study was to develop a series of artificial neural network (ANN) models to predict the viscosity values of crumb rubber-modified (CRM) binders using four input variables: asphalt binder source, rubber size, mixing duration and rubber content. The results indicated that ANN-based models are effective in predicting the viscosity values of CRM binders regardless of rubber type and can easily be implemented in a spreadsheet. In addition, the developed ANN model can be used to predict viscosity values of other types of CRM binders. Furthermore, the results also show that asphalt binder source, rubber size and rubber content are the most important factors in the developed ANN models while the mixing duration is relatively unimportant. The sensitivity analysis of input variables indicated that the viscosity changes significantly with changes in asphalt binder source, rubber size and rubber content. [ABSTRACT FROM AUTHOR]