LABORATORY EVALUATION AND NEURAL NETWORK MODELING FOR ROTATIONAL VISCOSITY OF REACTED AND ACTIVATED RUBBER MODIFIED BINDERS

Crumb rubber surface activation and pretreatment are considered as one of the promising newly introduced methods for asphalt rubber production. Reacted and Activated Rubber (RAR) is an elastomeric asphalt extender produced by the hot blending and activation of crumb rubber with asphalt and Activated Mineral Binder Stabilizer (AMBS). Besides RAR ability in enhancing the performance of asphaltic mixtures, its dry granulate industrial form enabled its addition directly into the mixture utilizing pugmill or the dryer drum with very minimal to no modification required on the plant level. This study aims to evaluate the rotational viscosity of RAR modified binders and develop an Artificial Neural Network (ANN) viscosity prediction model for extracting a stand-alone viscosity prediction equation. Three different Performance Graded (PG) asphalt binders modified by ten dosages of RAR were tested and evaluated under this study. Sixty-six samples that generated more than three thousand viscosity data point were utilized in binder performance evaluation and ANN modeling. The study concluded that RAR addition has decreased binder temperature susceptibility in considerable amounts when compared to the virgin binders. Furthermore, it was demonstrated that the testing shearing rate had a significant effect on the measured viscosity values for binders modified with high RAR content. The developed ANN model as well as the extracted stand-alone viscosity prediction equation had a high value of the coefficient of determination and were statistically valid. Both of them has the ability to predict the RAR modified binder viscosity as a function of binder grade, temperature, testing shearing rates, and RAR content

Increasing Electron Transfer Rates with Increasing Donor-Acceptor Distance

Electron transfer can readily occur over long (≥15 Å) distances. Usually reaction rates decrease with increasing distance between donors and acceptors, but theory predicts a regime in which electron-transfer rates increase with increasing donor–acceptor separation. This counter-intuitive behavior can result from the interplay of reorganization energy and electronic coupling, but until now experimental studies have failed to provide unambiguous evidence for this effect. We report here on a homologous series of rigid rodlike donor-bridge-acceptor compounds in which the electron-transfer rate increases by a factor of 8 when the donor–acceptor distance is extended from 22.0 to 30.6 Å, and then it decreases by a factor of 188 when the distance is increased further to 39.2 Å. This effect has important implications for solar energy conversion

Heterodinuclear ruthenium(II)-cobalt(III) complexes as models for a new approach to selective cancer treatment

Heterodinuclear ruthenium(ii)-cobalt(iii) complexes have been prepared as part of investigations into a new approach to selective cancer treatment. A cobalt(iii) centre bearing amine ligands, which serve as models for cytotoxic nitrogen mustard ligands, is connected by a bridging ligand to a ruthenium(ii)-polypyridyl moiety. Upon excitation of the ruthenium centre by visible light, electron transfer to the cobalt(iii) centre results in reduction to cobalt(ii) and consequent release of its ligands. We have synthesised several such structures and demonstrated their ability to release ligands upon excitation of the ruthenium centre by visible light

Transition Metal Donor-Peptide-Acceptor Complexes: From Intramolecular Electron Transfer Reactions to the Study of Reactive Intermediates

The trans-polyproline (PII) oligomers (Figure 1) are unusually rigid peptide structures which have been extensively studied by our group for peptide mediated intramolecular electron transfer (ET) at long distances. We have previously studied ET across a series of metal ion donor (D) acceptor (A) oligoproline peptides with different distances, driving forces and reorganizational energies. The majority of these experiments involve generating the ET intermediate using pulse radiolysis methods, although more recently photochemical methods are also used. Results of these studies showed that ET across peptides can vary by more than twelve orders of magnitude. Using ruthenium bipyridine donors, ET reaction rate constants across several proline residues (n = 4 - 9) occurred in the millisecond (ms) to {micro}s timescale, thus limiting the proline peptide conformational motions to only minor changes (far smaller than the large changes that occur on the ms to sec timescale, such as trans to cis proline isomerization). The present report describes our large data base of experimental results for D-peptide-A complexes in terms of a model where the involvement of both superexchange and hopping (hole and electron) mechanisms account for the long range ET rate constants observed. Our data shows that the change from superexchange to hopping mechanisms occurs at different distances depending on the type of D and A and their interactions with the peptides. Our model is also consistent with generalized models for superexchange and hopping which have been put forward by a number of theoretical groups to account for long range ET phenomena

Development of Deflection Parameters to Evaluate the Structural Capacity of Flexible Pavements at the Network Level: Case Study for the State of Texas

Pavement deflection has been used widely as a nondestructive technique to evaluate the structural capacity of pavements at both network and project levels. Various transportation agencies use several evaluation methods to evaluate the integrity of the pavement layers. Most of these up-to-date developed indices are exclusively based on either central deflections or one deflection point along FWD deflection bowl. However, no standardized method that utilizes the full FWD deflection bowl is available. This study aims to introduce new comprehensive pavement layer deflection and deflection bowl area parameters that are based on the entire FWD deflection bowl rather than one single deflection point and to relate the developed parameters to the field measured distress data. Thirty-five different pavement sections in the State of Texas were utilized in the study. Two comprehensive deflection parameters and a ranking scale were developed that may be utilized for the overall pavement structural condition evaluation

Modifying Existing Asphalt Mix Design Procedures for RAP/RAS Surface Mixtures

NCDOT RP 2021-06The NCDOT mixture design procedure assumes 100 percent of the binder contained within reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) is available for blending with virgin asphalt. However, the literature shows that this assumption is flawed due to the presence of recycled asphalt material (RAM) agglomerations that prevent complete recycled binder availability (RBA). As a result, RAM mixtures designed using current practices may suffer from an inadequate amount of virgin asphalt, rendering them susceptible to cracking. Furthermore, past research highlights significant variability in the rheological properties of RAP and RAS stockpiles across North Carolina. Correspondingly, the objectives of this study were to: (1) modify the NCDOT\u2019s procedures for the design of surface mixtures containing RAP and RAS to improve performance, and (2) modify the NCDOT\u2019s current specifications to improve the consistency of RAP and RAS mixtures. To meet these objectives, a literature review was conducted that identified two approaches for addressing partial RBA in mixture design: the corrected optimum asphalt content (COAC) method specified by Georgia DOT and the availability adjusted mixture design method (AAMD) developed in NCDOT RP 2019-21. A review of plant operations was conducted to identify the range of RAP and RAS management and characterization processes in the state and select six plants to include in the experimental plan. \u2018Control\u2019 mixture designs were then identified from each of the selected plants for evaluation. The control mixtures correspond to approved Job Mix Formulas (JMFs) and thus, reflect mixture designs prepared according to current NCDOT practices. The control mixture designs were redesigned according to the COAC and AAMD approaches. The performance of the control and redesigned mixtures were evaluated through laboratory testing and pavement performance simulations. The COAC and AAMD methods produced mixtures with enhanced cracking performance compared to control mixtures. The COAC approach yielded negative consequences on asphalt mixture rutting susceptibility compared to the current practice. In contrast, the AAMD method, which addresses the role of RAM agglomerations on both RBA and aggregate structure, resulted in rut depths similar to the respective control mixtures for mixtures prepared with fixed RAP content. Consequently, the research team recommends that the NCDOT consider adopting the AAMD method for designing surface mixtures