Enhanced aggregate-asphalt adhesion and stability of local hot mix asphalt

الملخص EN

A polymer modification is used to improve the fundamental properties of asphalt binders as those properties relate to the performance of asphalt mixtures.

Adhesion and cohesion are two important related properties of asphalt binders that can affect asphalt mixture performance.

The first target of this study is to quantify the effects of polymers on the adhesion and cohesion of the binders.

Two types of stones are used in this study, limestone and sandstone.

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 between 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 effect of the fine aggregate and polymer on the stability of the local asphalt mixture.

To achieve this target two blends have been selected, the first blend is passing under restricted zone (S shaped blend) and second blend passing through restricted zone (fine blend).

The pressure distribution analyzer (PDA) which is developed to Gyratory Load-cell Plate assembly (GLPA) by asphalt research group in Wisconsin University to measure and evaluate the resistance of mixture to distortion, the (PDA) is placed in the gyratory compactor mold and provide load measure which is recorded simultaneously with deflection, the vertical load and the eccentricity of the load are measured using three load cells placed at the edge of the plate, the measurements are used to calculate the resistive effort (w) as a function of number of gyrations.

Functionalized polyethylene (PE) polymer and styrene-butadiene-styrene (SBS) are used to show effect of polymers on Construction Force Index (CFI) which is related to the amount of the work done for rising density of the mix to 92 %.

The results indicated that CFI is reduced by about 68 % as using 3.5 % of PE, while it is reduced about 42 % when using 4 % of SBS which give good indication for contractors to use polymers for reducing cost.

Resistive effort results show that fine blend has higher stability than coarse (S-shape) blend, all the tests of local asphalt binders are done in the University of Wisconsin- Madison- USA.