Laboratory Study on the Combined Effect of Novolac and SBS Polymers on the Physical and Mechanical Properties of Hot Mix Asphalt

Abstract

With the growing need for sustainable and long-lasting paving materials, researchers have turned to innovative additives to improve the performance of bitumen and asphalt mixtures. Conventional bitumen often fails under heavy traffic loads and harsh climatic conditions, necessitating modification. This study aimed to improve the performance of bitumen and hot mix asphalt (HMA) by co-modifying them with a 4% styrene-butadiene-styrene (SBS) polymer and varying ratios of novolac resin. The results offered that the optimum ratio was 2% Novolac with 4% SBS. The physical and mechanical properties were evaluated through penetration tests, softening point, penetration index, dynamic shear rheometer (DSR), Marshall Stability tests, indirect tensile strength (ITS), tensile strength ratio (TSR), and wheel tracking. The modified mixture offered an improvement in penetration index from -1.89 to +1.3, a 38.7% increase in stability, a 40.9% increase in indirect tensile strength (ITS), and a 66.2% increase in moisture resistance. In comparison, the depth of permanent deformation was reduced by 58%. These results indicate significant improvements in stability, moisture, and deformation resistance, making it a promising option for developing more efficient asphalt mixtures. It also aligns with sustainable construction goals by reducing the need for frequent maintenance and extending pavement life.