Department of Civil Engineering
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Item Influence of Environmental Conditions on the Performance of Bituminous Mixtures(ASME, 2018-05) Bhargava, NishantAging and moisture damage are considered as major environmental factors which affect the performance of bituminous mixtures. This study investigated the effect of aging and moisture invasion on the performance of bituminous mixtures in terms of tensile strength and rutting resistance. Two different types of aggregates sources and one unmodified bituminous binder with and without warm additive were used. Bituminous mixtures were subjected to two levels of aging conditions (short-term and long-term aged) and two levels of moisture conditions (1 and 3 freeze-thaw cycles). A total of 24 different combinations were investigated for tensile strength and permanent deformation characteristics. Mineralogical investigations characterized the crushed stone as calcareous and bank run as siliceous aggregates. Results from this study demonstrate that levels of aging had a significant impact on the tensile strength of bituminous mixtures with warm mix additive as compared to conventional bituminous mixtures. Fracture work density, a surrogate cracking parameter was able to adequately capture the influence of aggregate mineralogy on the moisture susceptibility of long term aged mixtures. In addition, moisture conditioning was found to influence fracture work density of mixtures more than aging. Further, the rutting resistance of mixtures was determined in terms of flow numbers obtained using Francken model. In general, the rutting resistance of conventional mixtures was relatively higher than a mixture with warm mix additive. As expected, the flow number of conventional mixtures increased with aging and further reduced with moisture conditioning. Interestingly, the flow numbers of bituminous mixtures with warm mix additive was not negatively impacted by moisture at short term aged conditions. However, flow number of both mixtures after long term aging exhibited a similar trend. Additionally, statistical analysis showed that an increase in freeze-thaw cycles from one to three did not significantly impact the tensile characteristics of the mixtures.Item Synergistic influence of aging and moisture on performance of warm mix asphalt(IJPRT, 2018) Bhargava, NishantIn this study, the influence of aging and moisture on the two different mechanical behaviors of warm mix asphalt was studied. The cracking and permanent deformation resistance were assessed in terms of tensile strength and flow number computed using a three stage model respectively. The influence of temperature on the tensile strength and both stress and temperature levels on the permanent deformation response of aged and moisture conditioned warm mix asphalt were investigated. Results show that moisture and increase in temperature had a negative impact on the tensile strength of warm mix asphalt while aging had a positive impact. However, the variation in tensile strength of mixtures was strongly related to variation in percent air voids. Aging and interestingly moisture conditioning were found to increase the resistance to permanent deformation of warm mix asphalt. Permanent deformation behavior of moisture conditioned samples was further studied to assess the impact of saturation. Results showed that the presence of moisture in samples increases the permanent deformation resistance. From the statistical analysis it was found that both the individual and interaction of aging and moisture had a significant effect on the tensile strength and flow numbers.Item Laboratory Investigation on the Effect of Emulsion Type and Additive on Microsurfacing Mix(ASME, 2019-10) Bhargava, NishantIn this article, the effect of emulsion type and additive on the performance of microsurfacing mix is evaluated both for initial mix characteristics and long-term performance. Three mix formulations were used for microsurfacing performance assessment, including cationic slow set (CSS) 1-h, cationic quick set (CQS) 1-h Mix 1 with additive, and CQS 1-h Mix 2 without additive. Here, the additive used primarily imparts rapid setting and acts as an adhesion promoter. Also, for each formulation, microsurfacing performance was assessed at 4 emulsion contents. The initial properties were evaluated in terms of workability, set and cure time of the mix, and filler–emulsion compatibility. On the other hand, long-term performance of the mix was assessed in terms of resistance to raveling and rutting. It was found that the emulsion type had a major effect on cohesion development where the mix with CSS 1-h emulsion had relatively lower cohesion than CQS 1-h Mix 1. The abrasion loss and sand adhesion were also affected by emulsion type, which could probably be attributed to better compatibility of CQS 1-h emulsion with the aggregates used in this study. It was also interesting to note that although the performance of CQS 1-h Mix 1 was acceptable, the addition of additive resulted in substantial improvement of both workability and performance. The filler–emulsion compatibility increased from 4 to 12 points with the use of additive. The abrasion loss was reduced by 262 to 663 % depending on the emulsion content. Statistical analysis at the 5 % significance level also showed that both emulsion type and additive had a significant influence on microsurfacing performance in terms of mixing time, consistency, cohesion, raveling, and rutting resistance. However, the resistance to moisture damage provided by additive resulted in insignificant differences between CSS 1-h and CQS 1-h Mix 1.Item State of the art review on design and performance of microsurfacing(Taylor & Francis, 2019-04) Bhargava, NishantOver the years, microsurfacing had gained popularity owing to the effectiveness, economic and environmental benefits as a pavement preventive maintenance treatment. The review study explores the merits and demerits of mix design procedures along with modifications suggested by various studies. Subsequently, studies on the performance of microsurfacing had been extensively reviewed and significant parameters contributing to variation in performance were identified. Literature review indicated that the microsurfacing mix design, unlike conventional hot mix asphalt, was complicated due to chemically controlled curing system and additional components involving microsurfacing production. Despite simple test procedures, most commonly adopted mix design parameters such as mixing and setting time, and torque-measurements exhibit operator specific variability in test results. In order to overcome such issues, mechanical modifications for mixing and automated measurements of parameter values were proposed by several researchers. Laboratory investigations on microsurfacing performance highlighted that the inclusion of process control parameters and environmental conditions to mimic field conditions could further improve the evaluation of microsurfacing durability. In terms of field performance, even though microsurfacing contribute to road safety, issues related to noise and reflective cracking would require further research for better understanding and possible solutions. Hence, the evaluation of synergistic influence of parameters on microsurfacing performance by simulating production and environmental conditions in a laboratory would allow better quantification of the associated failures and help to find probable solutions.Item Systematic approach to address challenges in microsurfacing mix design(Elsevier, 2021-02) Bhargava, NishantThis paper presents a systematic laboratory approach for microsurfacing mix design to address the challenges faced due to multiple components and associated chemical complexity. A comprehensive laboratory study was undertaken to understand the variation in microsurfacing mix performance with respect to filler characteristics, mineral filler and emulsion components including emulsifier dosage, asphalt binder type and solvent. First, replacement of filler was done to address the issue of pre-mature breaking which was related to very high reactivity of aggregates. Next, the type and dosage of mineral filler was selected using cohesion test. Interestingly, the combination of cement (2%) and fly ash (1%) imparted highest cohesion highlighting the benefits associated with incorporation of waste materials having pozzolanic characteristics in the mix. In terms of emulsion components, use of higher emulsifier dosage showed a delay in the curing process which in turn, resulted in inferior cohesion, raveling and rutting resistance. Further, incorporation of harder asphalt binder and the use of solvent during emulsion production resulted in reduction in rutting by>61%. Raveling resistance was also found to be dependent on the use of solvent indicating the importance of maintaining equiviscous temperature during emulsion production. From the results, a narrow range diagram illustrating the acceptable range of emulsion content considering all design parameters was recommended to determine optimum emulsion content (OEC). The mid-point of acceptable emulsion content range was termed as OEC which, in the present study, was found to be 14% by dry weight of aggregates.Item Assessment of Asphalt Mixture Performance Subjected to Production and Paving Segregation(ASCE, 2020-11) Bhargava, NishantIn this study, the effect of aggregate segregation on the performance of hot mix asphalt was studied. The possible levels of aggregate segregation were arrived from the field core samples. Considering the level of segregation observed in the field, four levels of segregation that range from very fine to very coarse were simulated in the laboratory. Both production and paving segregation were simulated to explore the effect on asphalt mixture performance. Production segregation was imitated by sieving aggregates through 2.36 mm and batching in different proportions. Alternatively, a loose hot asphalt mixture was sieved on a 4.75-mm sieve and combined in different proportions to mimic paving segregation. The performance of segregated mixtures was evaluated in terms of moisture susceptibility, cracking resistance, fatigue life, raveling, and rutting resistance. The results of the investigations indicated that finer mixtures due to production segregation and coarser mixtures due to paving segregation were highly susceptible to moisture damage, raveling, and fatigue. In addition, the rutting potential for both production and paving segregation was higher for finer mixtures than coarser mixtures. The overall ranking of the performance parameters showed that finer mixtures resulting from production segregation had an inferior performance, whereas coarser mixtures resulting from paving segregation performed poorly relative to the control asphalt mixture.Item Utilizing Photodetection Technique to Assess Moisture Damage of Asphalt Mixtures(ASCE, 2021-08) Bhargava, NishantIn this study, asphalt mixtures were subjected to the boiling water test, and the stripping potential was quantified in terms of loss index using the photodetection technique. Initially, the change in loss index due to variability in testing protocols like boiling time, drying time, and drying method was evaluated. Subsequently, loss index (LI), and tensile strength ratio (TSR) were determined for three different aggregate types, five liquid anti-stripping additive contents, and four dosages of hydrated lime. Results indicated that LI increased with the increase in boiling time, whereas LI decreased due to moisture. In terms of the drying method, the recommended hot-air-gun drying method was suitable for quantifying stripping. Furthermore, the results of both LI and TSR had a good correlation. The threshold limits for LI with respect to specified TSR requirement was evaluated and was found to be sensitive to variation in aggregate type and additive content. Therefore, LI values estimated using a quick tool could facilitate quality control during the asphalt mixture’s production stage.Item Relative Contribution of Process Control Parameters on the Raveling Resistance of Microsurfacing Mix(Sage, 2021-09) Bhargava, NishantRaveling is one of the key performance parameters of microsurfacing treatment. During the material handling and mix production, process control parameters including aggregate gradation, emulsion content, and water content vary inevitably and might increase the risk of raveling. The objective of this study was to quantify the relative contribution of these process control parameters on the raveling resistance of the microsurfacing mix. For this purpose, a total of 30 combinations of aggregate gradation, emulsion content, and water content were subjected to raveling using wet track abrasion test. The investigations showed that the raveling increased for coarser gradation and lower emulsion content, whereas the variation in raveling was minimal with water content. Further, the test results were modeled using an artificial neural network (ANN). The ANN model was able to capture the influence of process control parameters on the raveling resistance of the microsurfacing mix. Garson’s algorithm was used to quantify the relative contribution of each process control parameter on raveling. It was found that the relative contributions of aggregate gradation, emulsion content, and water content were 40%, 28%, and 32%, respectively. Because of their substantial contribution, it is critical to ensure proper quality control of process control parameters during material handling and production of microsurfacing mix. In particular, coarser aggregate gradation in conjunction with lower emulsion content should be avoided to minimize the risk of raveling.Item Effect of Cement and Fly Ash Dosages on the Characteristics and Performance of Microsurfacing Mix(ASCE, 2021-11) Bhargava, NishantIn this study, the role of mineral fillers on the microsurfacing mix characteristics and performance was assessed for 10 different combinations of mineral filler type (cement and fly ash) and dosages (0%–3%). The mixes were initially characterized in terms of compatibility, cohesion, and adhesion using Schulze-Breuer and Ruck test, cohesion test, and boiling water test, respectively. Subsequently, the performance of microsurfacing mixes, that is, raveling and rutting resistance, was determined using wet track abrasion test and loaded wheel test, respectively. Results indicated that the filler–emulsion system’s compatibility improved significantly with the addition of cement at the proper dosage. In contrast, mixes with only fly ash as mineral filler had inferior filler–emulsion compatibility. Also, the rate of strength development and adhesion was higher with cement than fly ash. The performance, that is, raveling and rutting resistance, positively correlates with the 60-min cohesion, adhesion, and compatibility (abrasion loss). Interestingly, the combination with 2% cement and 1% fly ash as mineral filler had the best mix characteristic and performance, indicating that the careful selection of the type and the dosage of mineral filler could maximize the durability of the microsurfacing mix.Item Modeling the Factors Influencing the Rutting and Bleeding Characteristics of Microsurfacing Mix(ASCE, 2022-01) Bhargava, NishantIn this study, the effect of process control parameters, including aggregate gradation, emulsion content, and water content, on the rutting and bleeding characteristics of the microsurfacing mix was determined. A total of 30 combinations were selected to account for the synergistic variation of process control parameters in the field. Rutting and bleeding were assessed using a loaded wheel test and sand adhesion test, respectively. Laboratory investigations results showed that rutting was predominantly influenced by the combination of aggregate gradation and emulsion content. On the other hand, the combination of coarser gradation, higher emulsion content, and relatively lower water content led to increased risk of bleeding. Multigene symbolic genetic programming was used to model the rutting and bleeding behavior to better understand the complex behavior. The developed model was able to capture the behavior of the microsurfacing mix. A sensitivity analysis was conducted on the developed model by varying the values of input parameters one-by-one from 0.85 to 1.15 at an increment of 0.005. The results showed that the lateral displacement increased up to 1.6, 1.5, and 1.2 times the control mix for coarser aggregate gradation, higher emulsion content, and higher water content, respectively. Moreover, at the optimal emulsion content value, the lateral displacement was minimal. Sand adhesion increased up to 1.4, 1.2, and 1.1 times the control mix for coarser aggregate gradation, higher emulsion content, and lower water content, respectively. Hence, this study outcome identifies the aggregate gradation tending toward the coarser side, higher emulsion content, and variation of water content, either the dry or wet side, during production lead to poor rutting or bleeding performance of the microsurfacing mix