Investigation of Impact of Aggregate Coating by Bitumen on Change of Micro Texture Values

Zuzana Florkova,Peter Hrabovsky,Jana Pastorkova,Matus Farbak,Zuzana Kolkova

doi:10.33422/ejest.v3i1.161

Zuzana Florkova, Peter Hrabovsky + Show 3 more

Open Access

https://doi.org/10.33422/ejest.v3i1.161

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Abstract

Asphalt pavement micro texture values primarily depend on aggregate properties used in asphalt pavement mixture and by aggregate surfaces is secured the basic contact medium with vehicle tires. It often happens that new asphalt surfaces have not required skid resistance properties and is needed a certain period of time to eliminate film of bitumen binder which is coating the aggregate grain on the surface of pavement by action of vehicles. In most cases, the investigation of the aggregate micro texture impact on the pavement skid resistance properties is carried out under laboratory conditions and generally relates only to measurements on natural aggregate samples (without bitumen). However, due to coating of aggregate by bitumen binder, valleys between the individual peaks of aggregate are filled. Obviously, it can be supposed that the usage of high amount of bitumen content can leads to decreasing of aggregate micro texture values. From this point of view, it can be expected that change in micro texture values depends on the content of binder in the asphalt mixture. Particular aggregate grains were taken from asphalt mixtures samples (AC 8, AC 11 and SMA 11) produced in the laboratory, in order to determine the impact of aggregate coating by bitumen binder on micro texture change. Each usage asphalt mixture was produced with three different bitumen binder contents. Digital image analysis method was used for subsequent evaluation. Changes in the micro texture values depending on the amount of used bitumen binder and also on the calculated theoretical bitumen film thickness are investigated in the conclusion.

Highlights

Asphalt pavement micro texture ensures elementary friction level between tire and pavement and has the significant influence on the skid resistance properties of asphalt pavement
The basic parameter for the evaluation was determined as a microtexture change value (MCV in table), microtexture change value was calculated as a difference of values of volumetric parameter Zvd between coated and clear aggregates
Measurements by optical microscope method and subsequent evaluation by volumetric parameter Zvd were performed on aggregate grains with and without bitumen in order to obtain the value of microtexture change by coating of the aggregate by bitumen

Summary

Introduction

Asphalt pavement micro texture ensures elementary friction level between tire and pavement and has the significant influence on the skid resistance properties of asphalt pavement. Kandhal et al (1998) in the review described that asphalt mixtures produced with large surface area of the aggregate and low amount of bitumen content had a thin bitumen binder film and do not had sufficient durability. These mixtures are susceptible to cracking and scouring. Due to coating of aggregate by bitumen binder, valleys between the individual peaks of aggregate are filled From this point of view, it can be expected that change in micro texture values depends on the content of binder in the asphalt mixture. The exposed aggregate surfaces become polished and, within a year, the skid resistance normally falls to an equilibrium level (PeiZhong, 2015) (Figure 1)

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Conclusion