Moisture Susceptibility Of Warm Mix Asphalt Research Articles

Improving moisture and fracture resistance of warm mix asphalt containing RAP and nanoclay additive

Using warm mix asphalt (WMA) and reclaimed asphalt pavement (RAP) has both significant environmental and financial benefits for countries; however, fracture resistance of RAP in subzero temperatures and moisture susceptibility of WMA has been a setback for utilizing these technologies broadly in the field. Since the fracture behavior of WMA and RAP has not been studied simultaneously, this study undertakes to assess the performance of WMA mixtures incorporating various content of RAP materials with the addition of nano clay as additive. In order to meet this objective, fracture toughness of semi-circular bend (SCB) specimens made by different RAP ratio (0, 20, 30 and 40%) and nano clay content (0 and 3%) was studied in two subzero temperatures (−10 and −20 °C) under pure mode I, pure mode II, and two distinct mixed-modes (I/II). Moreover, indirect tensile strength (ITS) and AASHTO T283 tests were conducted to assess the influence of RAP and nano clay on moisture damage of WMA. The results show that the use of both RAP and nano clay has beneficial impacts on WMA mixtures in terms of fracture and moisture resistance. Moreover, the fracture resistance of samples rose with decreasing temperatures, and WMA mixtures are more prone to crack at mode mixities. Overall, the simultaneous use of WMA, RAP, and nano clay seems as an environmentally-friendly mixture that promises a better efficiency compared to conventional WMA.

Influence of water on warm-modified asphalt: Views from adhesion, morphology and chemical characteristics

It has been proven that warm mix asphalt (WMA) has great potential for reducing the fuel consumption and polluting emissions during the construction of asphalt pavement. However, the moisture susceptibility of WMA is one of the main concerns associated with this material, and it limits the wide application of this technology. In this study, a styrene–butadienestyrene (SBS) modified asphalt was selected as a control binder, and two types of WMA additives with different dosages were used to prepare warm modified asphalt binders. Atomic force microscopy (AFM), dynamic shear rheometer (DSR), and fourier transform infrared spectroscopy (FTIR) tests were carried out to evaluate the influence of water immersion on the nano-adhesion properties, morphological characteristics, stiffness, and chemical constituents of asphalt with and without the WMA additives. The results showed that several changes in the asphalt resulted from water immersion, including a decline in the adhesion performance, the appearance of small bumps on the surface of the asphalt, an increase in asphalt stiffness, and the amount of oxygen-containing functional groups and polar components in the asphalt. In addition, the SBS modifier in the asphalt remained stable during water immersion. Considering the effects of the WMA additives, it was found in this study that the water-induced adhesion degradation, oxidative aging, and increase of the polar components in asphalt could be delayed with the use of Sasobit.

Moisture resistance study on PE-wax and EBS-wax modified warm mix asphalt using chemical and mechanical procedures

Global warming, environmental concerns, and energy prices have led to increased use of wax additives to produce warm mix asphalt (WMA) as an alternative to hot mix asphalt (HMA). Despite many advantages, moisture susceptibility of WMAs is a legitimate concern. Although there have been many studies about moisture susceptibility of warm mix additives, mixtures containing ethylene-bis-stearamide (EBS) and polyethylene (PE) waxes have been less studied. In this research, moisture susceptibility of asphalt mixtures containing PE and EBS were evaluated. Furthermore, rheological and chemical evaluations of EBS and PE-wax modified binders were evaluated using dynamic shear rheometry and Fourier infrared spectroscopy, respectively. Moisture susceptibility was assessed using the modified Lottman test and the effects of aggregate type and production temperature were also evaluated. Results indicate improved moisture resistance for mixtures containing EBS. Additionally, the effect of PE-wax on moisture susceptibility was observed to be temperature dependent showing adverse effects at higher compaction temperatures.

Performance-Based Moisture Susceptibility Evaluation of Warm-Mix Asphalt Concrete through Laboratory Tests

This study used the cyclic direct tension test, indirect tensile strength test, and Hamburg wheel tracking device (HWTD) test to evaluate the moisture susceptibility of warm-mix asphalt (WMA) mixtures. The stripped areas that were quantified by digital imaging analysis were derived from the cyclic direct tension, indirect tensile strength, and HWTD tests and were compared with the mechanical properties of the mixtures to identify sensitive moisture susceptibility indicators. These methods were applied to a Superpave® 9.5-mm hot-mix asphalt mixture and five corresponding WMA mixtures that used the following technologies: (a) Evotherm 3G that contained a chemical additive, (b) foaming, (c) WMA-A that contained a chemical additive and was under development, (d) WMA-B that contained an organic additive and was under development, and (e) WMA-C that also contained an organic additive (different from that used in WMA-B) and was under development. Fatigue life ratios obtained from the simplified viscoelastic continuum damage model combined with layered viscoelastic analyses were determined to be the most sensitive indicators for moisture susceptibility. The stripping infection points derived from the HWTD tests also showed good sensitivity to moisture conditioning; however, each stripping infection point was affected by the permanent deformation characteristics of a given mixture as well as its moisture susceptibility; therefore, the observation was inconclusive.

Investigation of Moisture Susceptibility of Warm-Mix Asphalt Mixes through Laboratory Mechanical Testing

Moisture can lead to serious damage and failures in hot-mix asphalt concrete pavements. This is an even greater concern for warm-mix asphalt because the much lower production temperatures may not completely dry the aggregates. In this Maine Department of Transportation study, the use of fracture energy parameters was evaluated to determine the influence of incomplete drying of mixes on their mechanical properties. Fracture energy–based parameters [energy ratio (ER); ratio of energy ratio (RER)] were determined from the following testing of mixes with fully and partially dried aggregates, some of which were subjected to moisture conditioning: resilient modulus, creep compliance, and indirect tensile strength (ITS) at 5°C. The results indicate that (a) resilient modulus, creep compliance, and ITS were all affected by the presence of moisture in mixes; (b) the trend and the degree of influence of moisture for different mechanical parameters were different; (c) the moisture conditioning process caused larger decreases in modulus and ITS values than did incomplete drying of aggregates; however, the same moisture conditioning process caused much larger decreases in modulus and ITS in mixes prepared with incompletely dried aggregates than did the counterparts prepared with fully dried aggregates; and (d) fracture energy–based parameters (ER and RER) appeared to be more-distinctive moisture effect and damage indicators than are the other parameters.