Aggregate packing characteristics of good and poor performing asphalt mixes

Paper presented at the 26th Annual Southern African Transport Conference 9 - 12 July 2007 "The challenges of implementing policy?", CSIR International Convention Centre, Pretoria, South Africa. ABSTRACT:The aggregate structure of the compacted mix is a determining factor for the performance of Hot-Mix Asphalt (HMA). In this paper, the grading characteristics of good and poor performing HMA mixes are explored using the concepts of the Bailey method and related techniques for determining the porosity of the Dominant Aggregate Size Range (DASR) and the permeability characteristics of the mix. The aim is to assess the potential benefits of these new gradation analysis techniques for HMA performance in South Africa. The aggregate gradation of past mix designs, for which the field performance is known, are analysed and discussed in the paper. Typical properties of the aggregate structures of good and poor performing medium continuously graded asphalt (ACM) mixes are identified. The primary differences between the grading of the studied good and poor performing mixes lie in the grading of the coarser aggregate. While the poor performing mixes are coarser according to the classical definition, the good performers have a more voluminous DASR. The paper concludes that the grading analysis concepts allow the design engineer new insights into the structure of aggregates. The principles can be used to develop more specific guidelines for aggregate structure selection.This paper was transferred from the original CD ROM created for this conference. The material on the CD ROM was published using Adobe Acrobat technology. The original CD ROM was produced by Document Transformation Technologies Postal Address: PO Box 560 Irene 0062 South Africa. Tel.: +27 12 667 2074 Fax: +27 12 667 2766 E-mail: [email protected] URL: http://www.doctech.co.z

Bitumen rubber asphalt mix testing for South African pavement design method

Paper presented at the 30th Annual Southern African Transport Conference 11-14 July 2011 "Africa on the Move", CSIR International Convention Centre, Pretoria, South Africa.The South Africa National Road Agency Ltd has entered into a research and laboratory testing agreement with the CSlR to support the revision of the South African Pavement Design Method (SAPDM). The research includes characterising a bitumen-rubber semiopen graded mix, known in South Africa as BRASO. The general concern was whether the BRASO asphalt mix can be tested under the same test conditions as conventional asphalt mixes using the recently developed test protocols for SAPDM. This paper presents the analyses of laboratory testing data of a BRAS0 mix. The fundamental mechanical properties, including dynamic modulus, permanent deformation and beam fatigue characteristics of the BRASO, were determined in laboratory to enable future monitoring of the field performance of BRASO. It is anticipated that the test results presented in this paper will provide the required basis to develop reliable BRAS0 resilient response and damage models for SAPDM.This paper was transferred from the original CD ROM created for this conference. The material was published using Adobe Acrobat 10.1.0 Technology. The original CD ROM was produced by Document Transformation Technologies Postal Address: PO Box 560 Irene 0062 South Africa. Tel.: +27 12 667 2074 Fax: +27 12 667 2766 E-mail: nigel@doctech URL: http://www.doctech.co.zaCD sponsored by TRANSNE

A new hot-mix design method for Southern Africa

Paper presented at the South African Transport Conference 17 - 20 July 2000 "Action in transport for the new millennium", CSIR International Convention Centre, Pretoria, South Africa.This paper was transferred from the original CD ROM created for this conference. The material on the CD ROM was published using Adobe Acrobat technology. The original CD ROM was produced by Document Transformation Technologies Postal Address: PO Box 560 Irene 0062 South Africa. Tel.: +27 12 667 2074 Fax: +27 12 667 2766 E-mail: [email protected] URL: http://www.doctech.co.z