Experimental study on strength modification of bituminous mixture using Fuller’s earth

Material quality, environmental conditions, and traffic loads that lead to pavement deterioration pose significant challenges for the design of flexible pavements. This study concerns common distress affecting the surface course, which undermines its longevity and effectiveness. This key layer is composed of bituminous mixtures, and its behaviour directly influences the pavement’s durability. In the present study, it is proposed to improve the mechanical properties of these mixtures by adding Fuller’s earth, a natural clay with adsorptive properties and low cost. The modified mixtures were compared with conventional mixtures for strength and flow characteristics using the Marshall stability test. This modification was carried out by replacing the conventional filler with Fuller’s earth at replacement levels of 5% and 10% by weight. The prepared samples were tested rigorously to find the optimum replacement level. The modified mixes showed improved deformation and crack resistance, which indicates a significant improvement in overall pavement performance. The Marshall stability was increased by 28.42% for the mixture modified by 5 and 30.81% for the mixture modified by 10%. However, the difference between the two modification levels was 1.78% for stability and 2.22% for flow, indicating that the 5% Fuller’s Earth mixture provides a better balance between strength and material economy.