Low cement/fly ash blends for modification of Crushed Rock Base material Alireza Rezagholilou a,⇑ , Behnoud Ganjavi b , Hamid Nikraz c a Department of Petroleum Engineering, Curtin University, Australia b Department of Civil Engineering, University of Mazandaran, Iran c Department of Civil Engineering, Curtin University, Australia Received 5 February 2017; received in revised form 18 July 2018; accepted 29 August 2018 Abstract Crushed Rock Base (CRB) material sometimes needs to be modified typically due to the moisture susceptibility. Resilient modulus is the dominant design parameter of unbound materials and should be high enough to avoid distress or failure of a pavement. In Western Australia (WA), some modification methods such as dry-back or Hydrated Cement Treated Crushed Rock Base (HCTCRB) have been implemented in trial sections of pavements. But they could not provide the desired performances by poor drainability or widely-spaced open cracks in surface of thin bituminous pavements. As such, this paper attempts to review the challenges of each method and show how design requirements can be provided by another option so-called low cement/fly ash blends even in saturated conditions. This method covers the deficiencies of two previous methods in terms of cracking or moisture susceptibility as observed in limited field tests. Series of laboratory tests including uniaxial compression strength, resilient modulus, tube suction and shrinkage tests are undertaken to explore the key features of this modification method. Typical results indicated that resilient modulus improved two times while strength, shrinkage and capillary rise of this material are in the acceptable level. Ó 2018 Chinese Society of Pavement Engineering. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Keywords: Cement; Fly ash; Modification; Crushed rock; UCS; Resilient modulus; TST; ICC and shrinkage 1. Introduction At construction, Crushed Rock Base (CRB) material is often compacted near optimum moisture content to get the highest density. This moisture content can vary due to different seasonal, environmental or drainage condi- tions. Any increase in moisture content, however, adversely affects the design modulus or strength of base course layer in pavement [29,34]. Typically in fine grain soils, stiffness or resilient modulus drops nearly 50% from optimum to satu- ration moisture condition [8]. For CRB material, a section of the Kwinana Freeway in Western Australia (WA) showed high curvatures and deflections in Benkelman beam surveys [14]. They were due to unexpected saturations after three years of being in service [37]. Loss of resilient modulus (MR) in this type of base course material led to premature fatigue cracking of asphalt [20]. Thus, Main Roads of Western Australia (MRWA) called for some advanced laboratory tests to investigate CRB material in 1994. As such, Repeated Load Triaxial (RLT) test results were undertaken to understand modulus changes versus moisture contents. Results revealed that MR values decrease about 20–25% for every 1% increase https://doi.org/10.1016/j.ijprt.2018.08.006 1996-6814/Ó 2018 Chinese Society of Pavement Engineering. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). ⇑ Corresponding author. E-mail address: Ali.rezagholilou@curtin.edu.au (A. Rezagholilou). Peer review under responsibility of Chinese Society of Pavement Engineering. www.elsevier.com/locate/IJPRT Available online at www.sciencedirect.com ScienceDirect International Journal of Pavement Research and Technology xxx (2018) xxx–xxx Please cite this article in press as: A. Rezagholilou et al., Low cement/fly ash blends for modification of Crushed Rock Base material, Int. J. Pavement Res. Technol. (2018), https://doi.org/10.1016/j.ijprt.2018.08.006