The analysis of asphalt mixtures based on two-dimensional scanned images

Abstract

The internal structure of the aggregate skeleton Is very important for performance of asphalt mixtures, in particular regarding their resistance to permanent deformation. However, the analysis of gradation and volumetric properties of asphalt mixtures do not provide sufficient information to describe performance of asphalt mixtures in exploitation. In this paper the computer program iPas2, developed at the University of Wisconsin has been used. The program uses indexes that describe the structure of aggregate skeleton, like: number of contact zones between aggregate particles, total length and orientation of contact zones. These indices show very good correlation with resistance of asphalt mixture to permanent deformation. Program iPas2 has been used for the analysis of five asphalt mixtures that have been used in recent road construction and rehabilitation projects in Serbia, for base and wearing course, with regular and modified bitumen. The internal structure indicators for all mixtures have satisfactory values. The paper also identifies some problems encountered during the use of the latest software version.

Struktura agregatnog skeleta ima velikog uticaja na ponašanje asfaltnih mešavina, pre svega u pogledu njihove otpornosti na trajnu deformaciju. Međutim, analiza granulometrijskog sastava mineralne mešavine i zapreminske strukture asfaltne mešavine ne daju dovoljno podataka kako bi se opisalo ponašanje mešavine u fazi eksploatacije. U radu je korišćen program iPas2, razvijen na Univerzitetu Wisconsin, u okviru koga su definisani indeksi koji opisuju strukturu mineralnog skeleta, kao što su: broj kontaktnih zona između zrna agregata, ukupna dužina i orijentacija kontaktnih zona. Ovi indeksi pokazuju dobru korelaciju sa otpornošću asfaltne mešavine na trajnu deformaciju. Program iPas2 je primenjen za analizu pet asfaltnih mešavina koje su se u poslednje vreme koristile u projektima izgradnje ili rehabilitacije puteva u Srbiji za noseće i habajuće slojeve, sa običnim i polimer modifikovanim bitumenom. Dobijeni indikatori mirostrukture za sve mešavine zadovoljavaju. U radu su identifikovani i određeni problemi u radu sa najnovijom verzijom programa iPas2.