Enhanced Aggregate-Asphalt Adhesion and Stability of Local Hot Mix Asphalt

A polymer modification is used to improve th e fundamental properties of asphalt binders as those properties relate to the p erformance of asphalt mixtures. Adhesion and cohesion are two important related properties of asphalt binders that can affect asphalt mixture performance. The first t arget of this study is to quantify the effects of polymers on the adhesion and cohesio n of the binders. Two types of stones are used in this study, limestone and sandst one. The pneumatic adhesion tensile tester (PATTI) is used to measure the pull- off tensile strength in Wisconsin University, it is found that the tensile strength b etween limestone and styrene butadiene styrene (SBS) polymer increase 26% to 55% as using 2% and 4% of SBS respectively, while increase 54% to 76% when use 2% and 3.5% of Functionalized Polyethylene (PE) polymer respectively. For sandstone, 2% and 4% of SBS causes increasing the strength 5% and 18% respectively, while these values becomes 29% and 51% for asphalt binder modified with 2% and 3.5% of PE respectively. The second objective of this paper is to find the e ffect of the fine aggregate and polymer on the stability of the local asphalt mixtu re. To achieve this target two blends have been selected, the first blend is passi ng under restricted zone (Sshaped blend) and second blend passing through rest ricted zone (fine blend). The pressure distribution analyzer (PDA) which is devel oped to Gyratory Load-cell Plate assembly (GLPA) by asphalt research group in Wisconsin University to measure and evaluate the resistance of mixture to d istortion, the (PDA) is placed in the gyratory compactor mold and provide load measure which is recorded simultaneously with deflection, the vertical load a nd the eccentricity of the load are measured using three load cells placed at the e dge of the plate, the measurements are used to calculate the resistive ef fort (w) as a function of number of gyrations. Functionalized polyethylene (PE) poly mer and styrene-butadienestyrene (SBS) are used to show effect of polymers o n Construction Force Index (CFI) which is related to the amount of the work do ne for rising density of the mix to 92%. The results indicated that CFI is reduc ed by about 68% as using 3.5% of PE, while it is reduced about 42% when usin g 4% of SBS which give good indication for contractors to use polymers for reducing cost. Resistive effort results show that fine blend has higher stab ility than coarse (S-shape) blend, all the tests of local asphalt binders are done in the University of WisconsinMadison- USA.