Performance Evaluation of Styrene-butadiene-styrene (SBS) Modified Asphalt Mixtures using Dynamic Modulus Test

Abstract

Asphalt often has polymers added to it to enhance properties that effectively lengthen the asphalt's lifespan. Styrene-butadiene-styrene is one polymer that is often added to asphalt A common modifier with a high molecular weight polymer, styrene-butadiene- styrene (SBS), has the potential to modify asphalt binder by becoming miscible with it. Characterizing the performance of SBS modified asphalt mixes and untreated asphalt mixes was the aim of this investigation. PG 60/70 AC, NHA Class B gradation and SBS YH-791 modifier has been used in this research. The dynamic modulus |E*| test conducted through a simple performance tester (SPT), was used to look at stiffness behaviour & dynamic response and was the key component of laboratory characterization testing. (21) AC specimens (3 replicas per percentage) were fabricated using a Superpave gyratory compactor for performance testing. SBS was applied in various proportions ranging from 2 percent to 7 percent by the weight of bitumen. The SPT was used to perform the |E*| test at 4.4,21.1,37.8 & 54.4 ֯ C temperatures and 0.1,0.5,1,5,10 & 25 Hz frequencies. Marshall Mix Design approach was employed to find Optimum Bitumen Content (OBC), The research explored the links between dynamic modulus and mixture composition under investigation and found that temperature loading frequency and SBS significantly influenced the dynamic modulus of HMA. By creating the master curves of E*, the research also produced default dynamic modulus values for conventional mixes at different temperatures and frequencies, simplifying the use of a performance-based mechanistic- empirical structural design and analysis methodology. Further, the current research attempted to estimate the dynamic modulus of SBS-modified HMA utilising Artifical intelligence (AI) modelling using Multi Expression Programming (MEPX) and Regression modelling with validation. Results showed that SBS may be easily utilized as a modifier in bitumen since it lowered penetration and ductility values by up to 46% and 56 %, respectively, and raised softening point by 63% owing to the stiffness of the mix upon increasing SBS percentage upto 7%. A blend with 6% SBS by weight of bitumen has been shown to perform better than other mixtures. In addition, an average 2.10% times increase in dynamic modulus has been observed in comparison to a conventional mix. The phase angle initially rose with rising temperature before beginning to decline after reaching a high value at 37.8◦C. The HMA mix with a 6% SBS component produces the greatest outcomes overall.