Performance Evaluation of Styrene Butadiene Styrene and Nano-Clay Modified Hot Mix Asphalt Concrete

Abstract

In Pakistan, commuter traffic and freight operations are facilitated by roads, which account for 96% of all interior transit. Pavements are untimely failing due to heavy weight, harsh weather, poor subgrade conditions, and binders with insufficient performance grade. The mechanical features that will lengthen the pavement's useful life are recommended to be improved with additives. Styrene Butadiene Styrene (SBS) Modification of HMA Wearing Course and Dynamic Complex Modulus Calculations Using SPT are included in this work. To find the best modifier content, four SBS percentages were involved, and their outcomes were compared. Literature Review of earlier studies on SBS reveals that the material is less susceptible to temperature changes and has improved adhesion qualities. This study investigated how plain and modified HMA mixtures responded dynamically to compressive sinusoidal loads. Aggregate that was purchased underwent ASTM testing. Class A gradations from the National Highway Authority were employed in this project. Consistency tests were used to compare plain and SBS modified binders. The SBS 2%, 4%, and 6% samples' softening point values rose by 5.7%, 9.6%, and 15.3%, respectively. Using a Simple Performance Tester (SPT), tests for the dynamic modulus (|E*|) were conducted in compliance with AASHTO TP62-07 at four temperatures (4.4, 21.1, 37.8, and 54.4 °C), representing the cold and hot situations in the field, and frequencies of (0.1 to 25 Hz). Typical isothermal and isochronal curves were used to observe how temperature and loading frequency affected the estimation of dynamic modulus values. The NCHRP 9-29 Master Curve Excel Solver was used to compare the Master Curves of all four SBS percentages at the reference temperature of 21°C to determine the optimal SBS percentage. A single graph comparing master curves revealed that 4% SBS had the highest dynamic modulus values. To assess the relevance of factors affecting the asphalt mixtures in terms of dynamic modulus, statistical analysis via two-level factorial was used. Frequency and SBS% till the optimal value were directly related to Dynamic Modulus values, as shown by the relative effects of Temperature, Frequency, and SBS percentages and their combined effect depicted using Main plots, Standard interactions plot, Analysis of Variance, and Pareto Chart in Minitab Software. Phase and temperature, however, exhibited an inverse relationship. Of all the parameters, high temperature had the most of an adverse impact on dynamic modulus. Results showed that SBS 4% was optimal, with an increase in Dynamic Modulus value of 39.4% at 21.1°C. Thus, we arrived to the conclusion that the inclusion of 4% SBS modifier can serve as a formula for our pakistani pavement is resistant to rust and wear.