Experimental Study on potential use of blended steel slag dust and bagasse ash as mineral filler in HMA

Abstract

In highway pavement construction, one of the main problems is the insufficient amount of mineral filler from crushing rocks. This is due to the following: abundance, accessibility, high grinding costs, transportation costs, and the use of conventional filler (lime and crushed stone dust), which are the most commonly used filler in Ethiopia. To solve such a problem, it is important to look at other alternative filler materials that could replace crushed stone dust that can address the gap, whether partially or, if it is possible, fully. The aim of this research is to study the partial replacement of blended bagasse ash and steel slag dust as mineral fillers in hot mix asphalt. To determine the optimal bitumen content, three identical hot mix asphalt specimens were prepared (4.5%, 5.5%, and 6.5% crushed stone dust by weight of aggregates) and five different percentages of bitumen (4.0%, 4.5%, 5.0%, 5.5%, and 6.0% by weight of total mix). According to the procedure of the NAPA (National Asphalt Pavement Association) curve plotting method, the replacement of conventional filler (CSD) with non conventional filler was done by using optimum conventional filler content (5.5%), optimum bitumen content at 5.10%, and with different replacement proportions (0 control, 10%, 20%, and 30%) of blended bagasse ash and steel slag dust to get the optimum replacement percentage. The study compares the performance of asphalt mixes using stability and flow with corresponding volumetric properties, and at an optimum replacement percentage of non-conventional filler. One hundred two (102) samples were prepared. Forty-five (45) of these were prepared at each percentage of bitumen content and conventional filler content (CSD) in order to determine the optimum bitumen content (OBC) and the optimum filler content (OFC). The remaining forty-five (45) mixes were prepared to determine the optimum replacement proportion of non-conventional filler and twelves (12) for the Indirect Tensile Strength test. From the test results, the optimum replacement percentage of blended BA and SSD was found at 20% (5%BA and 15% SSD) by weight of optimum filler content (5.5%) at a bitumen content of 5.10%. Asphalt mixes prepared with blended BA and SSD filler are not sensitive to the action of water and result in better resistance to moisture-induced damage. The values at 20% blended BA and SSD (by weight of optimum filler content) replacement were stability of 11.0 KN, bulk density of 2.349 gm/cm3 ,air void (VA) of 4.0%, and TRS was 87.942%, which were the best when compared to other percentage replacement ratio values. Hence, 20% (by weight of optimum filler content) was adopted as the optimum replacement ratio of blended BA and SSD. Therefore, it can be concluded that blended BA and SSD can be used as mineral filler materials (crushed stone dust) substituted partially at 20% (5% BA and 15% SSD)