Fundamental and rheological properties of oil palm fruit ash modified bitumen Gatot Rusbintardjo a , Mohd. Rosli Hainin b , Nur Izzi Md. Yusoff c,⇑ a Dept. of Civil Engineering, Faculty of Engineering, Sultan Agung Islamic University (UNISSULA), Semarang, Indonesia b Faculty of Civil Engineering and Construction Research Alliance, Universiti Teknologi Malaysia, Skudai, Johor, Malaysia c Dept. of Civil & Structural Engineering, Universiti Kebangsaan Malaysia, Bangi, Selangor, Malaysia highlights  We investigate the suitability of using oil palm fruit ash as a bitumen modifier.  Several fundamental and rheological tests had been conducted in this study.  The OPFA-modified bitumen can be categorised as a binder with penetration grade of 60/70 or as PG 70-16. article info Article history: Received 7 January 2013 Received in revised form 31 July 2013 Accepted 29 August 2013 Available online 25 September 2013 Keywords: Bitumen OPFA Modifier Rutting Fatigue cracking Thermal cracking abstract This study was conducted to investigate the suitability of using oil palm fruit ash (OPFA) as a bitumen modifier. The OPFA was used to fulfil all bitumen modification requirements, as well as to take advantage of a waste by-product of the palm oil mill industry which could help to reduce environmental pollution. Twenty-four OPFA-modified bitumens (OPFA-MBs) were produced by the laboratory mixing of normal bitumen (80/100) from two sources with Fine and Coarse OPFAs of six different contents. This process was conducted at a mixing temperature of 160 °C, a mixing time of 60 min and a mixing stirring speed of 800 rpm. The consistency and rheological characteristics of the OPFA-MBs were analysed by means of conventional as well as dynamic mechanical analysis using dynamic shear rheometer (DSR), bending beam rheometer (BBR) and direct tension test (DTT). The results of the investigation indicate that binder compounded with OPFA becomes less susceptible to temperature, improve resistance to rutting at 70 °C, fatigue cracking at 20 °C, and thermal cracking at 17 °C of the surface pavement temperature compared to the unmodified bitumen. The OPFA-MB can be categorised as a binder with penetration grade of 60/70 or as PG 70–16 in the performance based system. Finally, it can be deduced that it is feasible to use OPFA as a modifier of bitumen. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction For several decades it was accepted that the empirical method of blending different types of base (unmodified or neat) bitumen was the only way to improve binding characteristics [1]. However, in recent years, increased traffic levels, larger and heavier trucks, new axle designs and increased tyre pressures have added to the already severe load and environmental demands on the highway system, resulting in the need to enhance the performance of the existing bituminous material [2,3]. Most base bitumen does not meet these requirements in regions with extreme climatic condi- tions [4,5]. Furthermore, a better understanding of the behaviour and characteristics of binders, in conjunction with the greater development of technology, has encouraged and enabled research- ers to examine the benefits of introducing additives and modifiers into bitumen. The modifiers currently available fall into various categories, such as naturally occurring materials, industrial by-products and waste materials, as well as carefully engineered products. Some of the more common categories include reclaimed rubber prod- ucts, fillers, fibres, catalysts, polymers (natural and synthetic) and extenders, to name a few [6]. Among them, a blend of bitumen and polymer is the most popular to improve the fundamental char- acteristics of bitumen, as its characteristics are related to the per- formance of asphalt mixtures. Polymer-modified bitumens, commonly abbreviated as PMBs, have been used for many years with asphalt mixtures and their usage is forecast to continuously increase in the immediate future, particularly in Europe, the United States of America, Canada and Australia [7]. For example, in the United Kingdom, the first polymer used, in the middle of the 1800s, was natural polymer latex rubber [8]. 0950-0618/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.conbuildmat.2013.08.056 ⇑ Corresponding author. Tel.: +60 3 8921 6447; fax: +60 3 8921 6147. E-mail address: izzi@eng.ukm.my (Nur Izzi Md. Yusoff). Construction and Building Materials 49 (2013) 702–711 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat