@article{malladi_asnake_lacroix_castorena_2018, title={Low-Temperature Vacuum Drying Procedure for Rapid Asphalt Emulsion Residue Recovery}, volume={2672}, ISSN={["2169-4052"]}, DOI={10.1177/0361198118791913}, abstractNote={ Asphalt emulsions are used extensively in tack coats and preservation surface treatments. The current specifications for asphalt emulsion residue recovery in AASHTO PP 72 are based on low-temperature evaporative drying. The shortest residue recovery procedure included in AASHTO PP 72 requires 6 h of conditioning in an oven to dry an emulsion. The ability to recover emulsion residues efficiently is of great interest given the ongoing efforts to develop emulsion performance-graded specifications based on residual binder properties. In this study, a rapid, vacuum drying technology was evaluated for asphalt emulsion residue recovery. The procedure enables the recovery of sufficient residual binder for dynamic shear rheometer (DSR) testing within 20–40 min. Five emulsions of different classifications were evaluated using both the vacuum drying procedure and the AASHTO PP 72 procedures. The vacuum drying procedure leads to similar water loss to the AASHTO PP 72 procedures. Based on the temperature-frequency sweep and multiple stress creep and recovery (MSCR) test results, the vacuum-dried residues are softer and more viscous than residues recovered using the AASHTO PP 72 procedures. Fourier transform infrared spectroscopy (FTIR) was performed to identify if oxidation levels could explain the observed in rheological trends. However, the results suggest no clear trend in the oxidation levels of residues recovered using AASHTO PP 72 compared with the rapid vacuum procedure. Future work is necessary to infer which method best reflects residual binders placed in the field. }, number={28}, journal={TRANSPORTATION RESEARCH RECORD}, author={Malladi, Haritha and Asnake, Meron and LaCroix, Andrew and Castorena, Cassie}, year={2018}, month={Dec}, pages={256–265} }
 @article{lacroix_underwood_kim_2011, title={Reduced Testing Protocol for Measuring the Confined Dynamic Modulus of Asphalt Mixtures}, volume={2210}, ISSN={0361-1981 2169-4052}, url={http://dx.doi.org/10.3141/2210-03}, DOI={10.3141/2210-03}, abstractNote={ Research project NCHRP 9–19 identifies the confined dynamic modulus as one of three favorable indicators for evaluating the rutting potential of a mixture. Though important, dynamic modulus testing at multiple confining pressures takes too long for state highway agencies to use it routinely. Therefore, several methods have been suggested to measure and predict confined dynamic modulus values without the need to run numerous tests. Experimental results show that the linear viscoelastic properties of an asphalt mixture are not affected by different confinements and that all confining stress effects are manifest in the elastic modulus at equilibrium, similar to unbound granular materials. The proposed method uses a Prony series representation of the dynamic modulus curve and master curve shift factors obtained from unconfined testing. This method uses the elastic modulus values predicted from a modified version of the universal material model to predict dynamic moduli at different levels of confinement. Beyond the typical AASHTO TP62 testing procedure under an unconfined condition, additional testing is conducted at 54°C at three levels of confinement. This reduced testing protocol provides reasonable results, with most errors less than 20%. The largest errors between the measured confined and unconfined data were generally overpredicted values at 54°C because the universal model overpredicted the elastic modulus. The applicability of this method is verified for the asphalt mixture performance tester as long as three levels less than 250 kPa are used, because 250 kPa is the maximum confining pressure that the tester can handle. }, number={1}, journal={Transportation Research Record: Journal of the Transportation Research Board}, publisher={SAGE Publications}, author={Lacroix, Andrew and Underwood, B. Shane and Kim, Y. Richard}, year={2011}, month={Jan}, pages={20–29} }
 @article{lacroix_kim_ranjithan_2008, title={Backcalculation of Dynamic Modulus from Resilient Modulus of Asphalt Concrete with an Artificial Neural Network}, ISSN={["2169-4052"]}, DOI={10.3141/2057-13}, abstractNote={ The NCHRP Project 1-37A Guide for Mechanistic–Empirical Design of New and Rehabilitated Pavement Structures introduces the dynamic modulus (|E*|) as the material property for the characterization of hot-mix asphalt mixtures. This is a significant change from the resilient modulus used in the previous AASHTO Guide for the Design of Pavement Structures. One of the challenges of changing the material characterization is that databases, such as the Long-Term Pavement Performance Materials Database, contain older material characterization information. Thus, such databases must convert their data to the currently accepted standard (i.e., |E*|). Other investigators have presented evidence that the resilient modulus can be predicted from the dynamic modulus by using the theory of viscoelasticity. By using their prediction method, this study proposes the population of a database of measured dynamic moduli with the corresponding predicted resilient moduli to train an artificial neural network (ANN). The ANN model was verified with four 12.5-mm surface course mixtures with different aggregate types and binder types and one 25.0-mm base mixture. The dynamic moduli predicted from the measured resilient moduli with the trained ANN were found to be reasonable compared with the measured dynamic moduli. }, number={2057}, journal={TRANSPORTATION RESEARCH RECORD}, author={Lacroix, Andrew and Kim, Y. Richard and Ranjithan, S. Ranji}, year={2008}, pages={107–113} }
 @article{lacroix_khandan_kim_2007, title={Predicting the resilient modulus of asphalt concrete from the dynamic modulus}, ISSN={["0361-1981"]}, DOI={10.3141/2001-15}, abstractNote={ The NCHRP 1-37A Guide for Mechanistic-Empirical Design of New and Rehabilitated Design Structures introduces the dynamic modulus as the material property to characterize asphalt concrete. This is a significant change from the resilient modulus used in the previous AASHTO pavement design guide. This paper presents an analytical method of calculating the resilient modulus from the dynamic modulus. It involves the application of multiaxial linear viscoelastic theory to linear elastic solutions for the indirect tension test developed by Hondros. The prediction method is verified by using three 12.5-mm surface course mixtures with different aggregate shapes and binder types and one 25.0-mm base mixture. Results show that the predicted and measured resilient modulus values are in close agreement. The results provide a forward model for the potential back-calculation of the dynamic modulus from resilient modulus databases already available in highway agencies, such as the Long-Term Pavement Performance Materials Database. }, number={2001}, journal={TRANSPORTATION RESEARCH RECORD}, author={Lacroix, Andrew and Khandan, A. Ardalan Mosavi and Kim, Y. Richard}, year={2007}, pages={132–140} }