Rutting and moisture-induced damage potential of foamed warm mix asphalt (WMA) containing RAP

Abstract

Despite significant economic and environmental benefits, performance of warm mix asphalt (WMA) containing reclaimed asphalt pavement (RAP) remains a matter of concern. Among the current WMA technologies, the plant foaming technique (called “foamed WMA” in this study) has gained the most attention, since it eliminates the need for chemical additives. In the present study, the laboratory performance, namely rutting and moisture-induced damage potential of foamed WMA containing RAP were evaluated and compared with those of similar hot mix asphalt (HMA) containing identical amount of RAP. Dynamic modulus, Hamburg wheel tracking (HWT) and flow number tests were performed to assess the rutting resistance of the mixes. Also, stripping inflection point from HWT tests and tensile strength ratio after AASHTO T 283 and moisture induced sensitivity test (MIST) conditioning were used to evaluate the moisture-induced damage of asphalt mixes. It was found that MIST conditioning effectively simulates the moisture-induced damage and can capture the propensity of asphalt mixes to moisture damage more distinctly compared to AASHTO T 283 method due to application of cyclic loadings. The foamed WMA was found to exhibit higher rutting and moisture-induced damage potential due to lower mixing and compaction temperatures compared to HMA. However, the increase in RAP content was found to reduce rutting and moisture-induced damage potential for WMA. Therefore, the lower stiffness of foamed WMA may be compensated with the addition of stiffer binder from RAP.

A Comparative Review of Hot and Warm Mix Asphalt Technologies from Environmental and Economic Perspectives: Towards a Sustainable Asphalt Pavement

“…Various types of recycled aggregates are used in WMA pavements, including reclaimed asphalt pavement (RAP), Recycled Asphalt Shingles (RAS), construction and demolition, and industry by-products (for example, copper or steel slags) [ 58 ]. The primary advantage of WMA is the potential to use a higher quantity of RAP [ 13 , 21 , 37 , 41 , 42 , 43 , 44 , 59 , 60 , 61 ]. Using RAP to replace the raw material eliminates the need to extract base raw materials and dump asphalt; this reduces the material and end-of-life consequences [ 31 ].…”

“…The economic benefit of the lower production temperature is directly proportional to the low energy consumption [ 18 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ], which reduces the financial costs [ 35 , 36 , 37 ]. WMA production and paving are beneficial because they modulate the mixture viscosity, enhance mixture workability, facilitate compaction [ 38 , 39 , 40 ], allow the use of reclaimed asphalt pavement (RAP) [ 41 , 42 , 43 , 44 ], and provide better working conditions and a healthy work environment [ 45 , 46 , 47 ]. In more detail, and from the environmental perspective, WMA technology reduces CO 2 emission based on temperatures during the paving process, which reflect the benefits of paving using WMA techniques that directly affect the workability and compaction of the mixture.…”

Warm mix asphalt use in Slovenia and in Europe: A review

“…The major concern is moisture-related damage, as lower production temperatures can lead to incomplete drying of aggregates and entrapment of residual moisture in the mix, causing striping and rutting and thus reducing pavement service life. [2,4,5,7,[9][10][11]15,17] Various studies also indicated that moist aggregates and lower production temperature can significantly reduce the resistance of asphalt mixtures to permanent deformation. [4,15,17] Consequently, increased susceptibility to moisture and reduced ageing may result in intensified maintenance also due to premature rutting.…”

A Study of Adhesion in Foamed WMA Binder-Aggregate Systems Using Boiling Water Stripping Tests

“…The majority of the works focus on the functional properties of the foamed binders, mostly showing no significant detrimental effects of the foaming process; however, decreased aging of the binders is often raised as a potential problem for the short-term high-temperature performance of these mixtures [ 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ]. A number of studies have been published on the resistance to moisture damage of warm-mix-asphalt produced using mechanical water foaming, showing that these mixtures may be more susceptible to the action of water [ 43 , 44 , 45 , 46 ]. In some studies [ 44 ], it was also shown that plant-produced foamed warm-mix asphalt exhibits similar moisture susceptibility to hot-mix asphalt, as opposed to laboratory-produced warm mixes.…”