Analysis of different reclaimed asphalt pavements to assess the potentiality of RILEM cohesion test
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ORIGINAL ARTICLE
Analysis of different reclaimed asphalt pavements to assess the potentiality of RILEM cohesion test Edoardo Bocci
. Emiliano Prosperi
Received: 5 May 2020 / Accepted: 19 August 2020 RILEM 2020
Abstract In the last years, RILEM Technical Committee 237-SIB proposed a new test protocol for reclaimed asphalt pavement (RAP) characterization, the cohesion test, with the goal to facilitate the identification of the most suitable solution for the recycling within new pavement layers. However, this procedure actually allows discriminating between different RAP sources but it does not exactly indicate the effective ‘‘activity’’ of the binder in the RAP. The present paper deals with the analysis of different RAP materials through the RILEM cohesion test. In particular, two ‘‘young’’ RAPs, different in composition and milled immediately after being laid, were aged in the laboratory and tested at different ageing levels. Moreover, an in-site aged RAP was tested as reference, either in neat conditions or after being sprayed with a rejuvenator. The results showed that the actual cohesion test approach, based on the evaluation of the indirect tensile strength (ITS), is not able to distinguish between RAP binders with stiff-brittle behaviour or good residual binding properties (despite the first is an unwanted condition while the second is a E. Bocci (&) eCampus University, Via Isimbardi 10, 22060 Novedrate, CO, Italy e-mail: [email protected] E. Prosperi Universita` Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy e-mail: [email protected]
desired condition, both of them determine an increase in ITS). Differently, the Cracking Tolerance Index (CTIndex ) defined by ASTM D8225-19 can emphasize the RAP bitumen ductility and highlight any residual binding and adhesive properties. For this reason, a RILEM cohesion test improvement is proposed by including the CTIndex calculation in the analysis. Keywords Reclaimed asphalt pavement Cohesion test RAP characterization Cracking Tolerance Index Laboratory ageing
1 Introduction Worldwide, one of the outcomes of flexible pavement rehabilitation and maintenance works is the generation of huge amounts of reclaimed asphalt pavement (RAP). RAP is the material resulting from the milling of asphalt concrete (AC) pavement layers and includes mineral aggregate, bitumen and air voids. It can appear in form of clusters (‘‘pieces’’ of AC with various sizes), single aggregate particles covered by bitumen and powder of bituminous mastic [1, 2]. During its service life, AC ages as a consequence of the traffic and environmental conditions, determining physico-chemical changes in the bitumen [3]. On the one side, bitumen is subjected to oxidation, i.e. the polymeric chains of bitumen capture oxygen
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molecules. On the other side, bitumen suffers volatilization, i.e. the reduction of the aromatic component and the increase of the asphaltene content (in percentage) [4–6]. The effe
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