Using soybean-derived materials to rejuvenate reclaimed asphalt pavement (RAP) binders and mixtures

Over the past few years, the use of reclaimed asphalt pavement (RAP) has been growing consistently from 15% in 2009 to 20.3% in 2015. The desire to use higher amounts of RAP is inspired by the need to lower costs, conserve energy, and preserve the environment. Increasing asphalt prices, and limited supply of higher quality virgin aggregates, are strong motivations to use RAP as a replacement for the more expensive virgin asphalt and aggregates. The main obstacle from using higher amounts of RAP is the aged and deteriorated properties of the RAP binder. With aging, asphalt binders suffer from oxidation which results in the conversion of part of the maltenes fraction to asphaltenes. Asphaltenes are primarily responsible for increasing the asphalt stiffness. The use of rejuvenators help restore the balance between the asphaltenes and maltenes, by adding more maltenes and/or improving the dispersion of asphaltenes. Current rejuvenators that are available in the market are based on several materials including petroleum-based aromatic extracts, distilled tall oil, and other natural oils (i.e., organic oils). Bio-based rejuvenators have proven to be a better and safer alternative to petroleum-based rejuvenators containing aromatic compounds. This research introduces a soybean-derived rejuvenator which is used to enhance the low temperature and fatigue properties of asphalt binders. During the first phase of the research, the effect of the rejuvenator is assessed by blending it with a neat PG58-28 and a polymer modified PG64-28 binders. Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) tests are conducted to characterize the rheological properties of the rejuvenated binders. Temperature-frequency sweeps are conducted and complex shear modulus curves are constructed to compare between the control and the rejuvenated binders. Dynamic modulus specimens are made using the rejuvenated PG58-28 and PG64-28 binders. The impact of the rejuvenator on both the dynamic modulus and phase angles is studied using master curves. A comprehensive statistical analysis using split-plot repeated measures (SPRM) is conducted to reveal statistical differences between the performance of the rejuvenator in both types of binders. The preliminary results indicate that the soybean-derived rejuvenator was successful at lowering both the high and low critical temperatures of both types of binders. The statistical analysis revealed that the extent of modification brought about by the rejuvenator was dependent on the binder type. The results of the dynamic modulus testing showed a consistent reduction in the dynamic modulus values and an increase in the phase angles with the use of the rejuvenator. A Fourier-transform Infrared study (FTIR) performed on the rejuvenated binders indicated that their aging behavior was similar to that of the control binders, indicating that the rejuvenator did not adversely impact the durability of the binders. In the second phase of this research, a rejuvenated PG58-28 binders was blended with an extracted reclaimed asphalt pavement (RAP) binder. The fatigue behavior of the rejuvenated RAP binder is evaluated using linear amplitude sweep (LAS) testing. A significant increase in the fatigue life, particularly at low temperatures and increasing shear rate, is noted with the use of the rejuvenator. The rejuvenator was successful in lowering the performance grade of the stiff aged RAP binder to acceptable ranges. 100% RAP mixtures made and compacted into dynamic modulus and disk-compact tension (DCT) specimens were made using the neat PG58-28 and rejuvenated PG58-28 binders. The DCT specimens containing the rejuvenator showed higher fracture energy at a test temperature of -6oC which indicates better thermal cracking resistance. To assess the effect of blending efficiency, additional DCT specimens were prepared using extracted RAP binder blended with the rejuvenated PG58-28 binder. The RAP/rejuvenated PG58-28 blend was then remixed with the extracted RAP aggregate to simulate full blending. The DCT specimens prepared as such yielded even higher fracture energies indicating the significance of proper blending. The thermal stability of the rejuvenated RAP binder was verified using thermogravimetric analysis (TGA). The mass loss due to thermal decomposition of the rejuvenated RAP binder was similar to that of the control binder. A study of the evolved gases using FTIR showed that the rate of mass loss of the rejuvenator can be inferred by comparing the FTIR spectra at different times

Conductive paint-filled cement paste sensor for accelerated percolation

Cementitious-based strain sensors can be used as robust monitoring systems for civil engineering applications, such as road pavements and historic structures. To enable large-scale deployments, the fillers used in creating a conductive material must be inexpensive and easy to mix homogeneously. Carbon black (CB) particles constitute a promising filler due to their low cost and ease of dispersion. However, a relatively high quantity of these particles needs to be mixed with cement in order to reach the percolation threshold. Such level may influence the physical properties of the cementitious material itself, such as compressive and tensile strengths. In this paper, we investigate the possibility of utilizing a polymer to create conductive chains of CB more quickly than in a cementitious-only medium. This way, while the resulting material would have a higher conductivity, the percolation threshold would be reached with fewer CB particles. Building on the principle that the percolation threshold provides great sensing sensitivity, it would be possible to fabricate sensors using less conducting particles. We present results from a preliminary investigation comparing the utilization of a conductive paint fabricated from a poly-Styrene-co-Ethylene-co-Butylene-co-Styrene (SEBS) polymer matrix and CB, and CB-only as fillers to create cementitious sensors. Preliminary results show that the percolation threshold can be attained with significantly less CB using the SEBS+CB mix. Also, the study of the strain sensing properties indicates that the SEBS+CB sensor has a strain sensitivity comparable to the one of a CB-only cementitious sensor when comparing specimens fabricated at their respective percolation thresholds

Using soybean-derived materials to rejuvenate reclaimed asphalt pavement (RAP) binders and mixtures

Over the past few years, the use of reclaimed asphalt pavement (RAP) has been growing consistently from 15% in 2009 to 20.3% in 2015. The desire to use higher amounts of RAP is inspired by the need to lower costs, conserve energy, and preserve the environment. Increasing asphalt prices, and limited supply of higher quality virgin aggregates, are strong motivations to use RAP as a replacement for the more expensive virgin asphalt and aggregates. The main obstacle from using higher amounts of RAP is the aged and deteriorated properties of the RAP binder. With aging, asphalt binders suffer from oxidation which results in the conversion of part of the maltenes fraction to asphaltenes. Asphaltenes are primarily responsible for increasing the asphalt stiffness. The use of rejuvenators help restore the balance between the asphaltenes and maltenes, by adding more maltenes and/or improving the dispersion of asphaltenes. Current rejuvenators that are available in the market are based on several materials including petroleum-based aromatic extracts, distilled tall oil, and other natural oils (i.e., organic oils). Bio-based rejuvenators have proven to be a better and safer alternative to petroleum-based rejuvenators containing aromatic compounds. This research introduces a soybean-derived rejuvenator which is used to enhance the low temperature and fatigue properties of asphalt binders. During the first phase of the research, the effect of the rejuvenator is assessed by blending it with a neat PG58-28 and a polymer modified PG64-28 binders. Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) tests are conducted to characterize the rheological properties of the rejuvenated binders. Temperature-frequency sweeps are conducted and complex shear modulus curves are constructed to compare between the control and the rejuvenated binders. Dynamic modulus specimens are made using the rejuvenated PG58-28 and PG64-28 binders. The impact of the rejuvenator on both the dynamic modulus and phase angles is studied using master curves. A comprehensive statistical analysis using split-plot repeated measures (SPRM) is conducted to reveal statistical differences between the performance of the rejuvenator in both types of binders. The preliminary results indicate that the soybean-derived rejuvenator was successful at lowering both the high and low critical temperatures of both types of binders. The statistical analysis revealed that the extent of modification brought about by the rejuvenator was dependent on the binder type. The results of the dynamic modulus testing showed a consistent reduction in the dynamic modulus values and an increase in the phase angles with the use of the rejuvenator. A Fourier-transform Infrared study (FTIR) performed on the rejuvenated binders indicated that their aging behavior was similar to that of the control binders, indicating that the rejuvenator did not adversely impact the durability of the binders. In the second phase of this research, a rejuvenated PG58-28 binders was blended with an extracted reclaimed asphalt pavement (RAP) binder. The fatigue behavior of the rejuvenated RAP binder is evaluated using linear amplitude sweep (LAS) testing. A significant increase in the fatigue life, particularly at low temperatures and increasing shear rate, is noted with the use of the rejuvenator. The rejuvenator was successful in lowering the performance grade of the stiff aged RAP binder to acceptable ranges. 100% RAP mixtures made and compacted into dynamic modulus and disk-compact tension (DCT) specimens were made using the neat PG58-28 and rejuvenated PG58-28 binders. The DCT specimens containing the rejuvenator showed higher fracture energy at a test temperature of -6oC which indicates better thermal cracking resistance. To assess the effect of blending efficiency, additional DCT specimens were prepared using extracted RAP binder blended with the rejuvenated PG58-28 binder. The RAP/rejuvenated PG58-28 blend was then remixed with the extracted RAP aggregate to simulate full blending. The DCT specimens prepared as such yielded even higher fracture energies indicating the significance of proper blending. The thermal stability of the rejuvenated RAP binder was verified using thermogravimetric analysis (TGA). The mass loss due to thermal decomposition of the rejuvenated RAP binder was similar to that of the control binder. A study of the evolved gases using FTIR showed that the rate of mass loss of the rejuvenator can be inferred by comparing the FTIR spectra at different times.</p

Performance of carbon nanotubes/cement composites using different surfactants

The performance of Carbon Nanotubes (CNTs) in cement-based composites relies to a great extent on its degree of dispersion. In this work, the performance of two commonly used surfactants; Sodium dodecyl sulfate (SDS) and Triton X-100, is being compared. The effect of surfactant-to-CNT ratio on dispersion efficiency is studied using UV-Vis spectrometry, to determine the optimum surfactant dosage. For the optimum ultra-sonication energy, Raman spectroscopy is used to assess the degree of imperfections on CNTs. CNTs-reinforced mortar specimens prepared using Triton X-100 and SDS are tested for compressive and flexural strength. Triton X-100 is shown to exhibit better dispersion efficiency than SDS, leading to more improvement in flexural and compressive strength. An ultra-sonication time of 60 minutes (19.4 KJ/ml) is shown to be sufficient to achieve proper dispersion, however notable degradation of CNTs was noted beyond 30 minutes (9.7 KJ/ml) of dispersion leading to a strength reduction.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Update of the PG Binder Map in California Using the Enhanced Integrated Climate Model (EICM) and LTTPBind Online

California has a diverse climate that ranges from desert regions with some of the hottest places in North America to coastal regions with mild climates and cold summers. The selection of the binder's performance grade (PG) in California is based on a climate map that was developed in 2005 using 1960 to 1990 data from the National Climate Data Center (NCDC) analyzed using the Enhanced Integrated Climate Model (EICM) and the Long-Term Pavement Performance (LTPPBind 2.0) software. Climate change is happening all around the world, and California is no exception. Based on observed pavement performance, there was a need to revise the PG map using updated climatic data from various sources. In this study, the PG binder map for California was updated to better predict pavement performance using the latest available weather data. Thirty years of climate data (1991-2019) were considered to update the current binder's PG map. The weather data were collected from two main sources: NCDC and Modern-Era Retrospective Analysis for Research and Applications (MERRA). It was found that pavement structure types and thermal coefficients have insignificant effects on the binder performance grade. Also, it is recommended that the binder high PG for the central valley of California be changed based on the results obtained from analysis using EICM and LTPPBind Online

Impact of Silo Storage on the Performance of Plant-Produced Mixes Containing High Content of Reclaimed Asphalt Pavement or Reclaimed Asphalt Shingles

Use of recycled materials, such as reclaimed asphalt pavement (RAP) and reclaimed asphalt shingles (RAS), is gaining widespread interest. Currently the California Department of Transportation standard specifications do not allow the use of RAS and limit the use of RAP contents to a maximum of 25% by dry weight of aggregate, though there is a non-standard special provision that allows use of up to 3% RAS by mass of aggregate and 40% RAP content by binder replacement. Nevertheless, mixes with high RAP and RAS are being produced across California for local agencies and commercial use. This study investigated the performance of four plant-produced high RAP or RAS mixes collected from different regions in California. The mixes were not designed and produced following Caltrans specifications. However, they provide insight into the effects of silo storage time on blending of virgin and RAP binder, the performancerelated properties of these mixes, and the measurement of properties by accepted performance-related tests. The mixes were collected before silo storage and after hours in the silo. Testing of the mixes included the following tests: four-point flexural beam stiffness and fatigue, Hamburg Wheel-Track (HWT), confined and unconfined repeated load triaxial (RLT), semicircular bending (SCB), and indirect tensile asphalt cracking test (IDEAL-CT). Additional testing was also conducted on the fine aggregate matrix (FAM) mixes to characterize fatigue and stiffness. This report presents preliminary findings from this study, including results related to the effects of silo storage time on stiffness, cracking resistance, and rutting resistance using performance-related tests as well as an initial comparison of the results from alternative cracking test types for these mixes. The results showed that silo storage time can increase stiffness on the order of 50% to 60%, with corresponding negative effects on fracture resistance and controlled-strain flexural fatigue life. The fatigue performance of the mixes reduced with increased silo storage, particularly at high strain levels, as measured by the flexural beam test. Use of a high rejuvenator dose could also potentially lead to rutting problems and poor fatigue performance. The FAM mix testing showed promising results in terms of characterizing fatigue. However, in its current form, it is not yet practical for use as a quality control/quality assurance test. The recommendation is that the effect of aging and blending of high RAP or RAS mixes be further investigated to understand the full impact of silo storage on these types of mixes. Performance-related specifications should consider the variation in mix properties due to silo storage