Selecting the Optimum Graphical Method to Find Aggregate Blend Proportions in the Production of HMA

Abstract

The proportions of aggregate directly affect the performance of HMA depending on their shape, texture, and strongly on the gradation. The determination of aggregate proportions depends strongly on the number of aggregate types to be blended, and the limits of the desired gradation. In this research, ten samples had been taken from different text books and papers. Each one contains three types of aggregates; coarse, fine, and filler. The samples were solved individually by seven different methods; five of them by graphical method, the sixth method was solved by running MATLAB, and the last method by using Excel sheet. In this research, five graphical methods were applied, and the aim of using them is to find graphically the tentative blending values and then compare their results individually with optimum values which was found from an Excel spreadsheet, and finally selecting the optimum method. For this purpose, more than 210 readings were utilized. SPSS program was run two times. In the first run, the values of person correlation (r) of method, Balanced-Areas (Rothfuchs), Walace, Equal Distance, Triangular, and Asphalt Institute when correlated with optimum values were 0.973, 0.964, 0.958, 0.953, and 0.869, respectively. In the second SPSS run, the values of samples No.4 and No.10 were removed because they gave zeros readings, the person correlation of Triangular, Balanced-Area, Walace, Equal Distance, and Asphalt Institute methods were 0.972, 0.970, 0.959, 0.952, and 0.869, respectively. In this research, it has been found that the Equal Distances method would be considered as an accurate, fast, and even easy method, and can be used for any number of aggregate.