Evaluation of mix design volumetrics and cracking potential of foamed Warm Mix Asphalt (WMA) containing Reclaimed Asphalt Pavement (RAP)

Abstract

In this study, the mix design volumetrics and cracking potential of foamed Warm Mix Asphalt (WMA) containing various amounts of Reclaimed Asphalt Pavement (RAP) were evaluated. It was found that the increased coating ability of the foamed WMA binder counteracted the lowering of mixing and compaction temperatures for WMA. Therefore, both control HMA and foamed WMA exhibited similar mix design volumetrics up to certain lower temperatures. However, further reductions in the mixing and compaction temperatures for foamed WMA were found to exhibit improper mixing between aggregates and foamed binder. Despite foamed WMA exhibiting similar volumetric properties as HMA up to certain lower temperature, their fatigue cracking performance was found to be significantly different. The foamed WMA was found to exhibit higher cracking resistance compared to HMA in Louisiana Semi-Circular Bending (SCB) and Illinois Flexibility Index Test (I-FIT) tests. A similar trend in the cracking resistance was observed for coarser mixes in the Abrasion Loss Test (commonly known as Cantabro test). However, the Cantabro test could not screen finer mixes for their cracking resistance as it lacks a mechanistic basis. Finally, the foamed WMA technology was found to increase the cracking resistance of asphalt mixes. The higher RAP content in the foamed WMA, on the contrary was found to lower the cracking resistance of asphalt mixes due to incorporation of aged and stiffer binder from RAP.

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

“…An increase in dynamic modulus values was observed with an increase in frequency and decrease in testing temperature. These results are compatible with expectations as an increase in testing frequency and/or a decrease in temperature increases the stiffness of asphalt mixes [13,24,32].…”

Characterizing the Aging and Performance of Asphalt Binder Blends Containing Recycled Materials

“…2). Based on these results, a modified CA parameter (CA mod ) was proposed to track the aging of binder blends containing rejuvenator as shown in equation (9). In this equation, the CA…”

“…2,3 Additionally, increasing use of reclaimed asphalt pavement (RAP), reclaimed asphalt shingles (RAS), and rejuvenating agents (used to promote blending of RAP/RAS and virgin binders and soften the blended binder) in pavement construction poses further challenges in predicting the effects of aging on asphalt concrete. 2,9 As part of efforts toward improving the cost and environmental sustainability of asphalt pavements, various recycled materials have been used in the maintenance, rehabilitation, and construction of new pavements for more than 40 years. 4,[9][10][11] A survey conducted by Williams, Willis, and Shacat 12 reported that about 94 % of RAP has been put back into new asphalt mixes in 2019.…”

“…2,9 As part of efforts toward improving the cost and environmental sustainability of asphalt pavements, various recycled materials have been used in the maintenance, rehabilitation, and construction of new pavements for more than 40 years. 4,[9][10][11] A survey conducted by Williams, Willis, and Shacat 12 reported that about 94 % of RAP has been put back into new asphalt mixes in 2019. The amount of RAP used in 2019 in the United States was 89.2 million tons, about 8.5 % more than in 2018 and about 60 % more than in 2009.…”

“…4,6,[13][14][15][16] However, an increase in RAP/RAS has been found to reduce low-temperature cracking resistance in the longer term. 5,9,17 For asphalt mixes with high recycled material contents (more than 30 % reclaimed binder), a suitable rejuvenator is typically used to reduce the effects of stiffer RAP/RAS binder and to increase low-temperature and block cracking resistance, both of which are top-down aging-related phenomena. However, the addition of all these materials causes more complexity in the asphalt aging behavior.…”