Laboratory evaluation of the effect of nano-organosilane anti-stripping additive on the moisture susceptibility of HMA mixtures under freeze–thaw cycles Mahmoud Ameri a,⇑ , Sareh Kouchaki a , Hossein Roshani b a School of Civil Engineering, Iran University of Science and Technology (IUST), Tehran, Iran b Department of Civil Engineering, University of Guilan, Rasht, Iran highlights  Addition of both anti-stripping additives significantly increased the ITS and TSR values of all asphalt mixtures.  Effects of anti-stripping additives on mixtures made with siliceous aggregate are more noticeable than limestone mixtures.  The fracture energy area under the load–deflection curve, for the Zycosoil-modified mixtures is higher than other mixtures.  Generally, influence of freeze–thaw cycling on resilient modulus and fracture energy was in accordance with TSR results. article info Article history: Received 25 April 2013 Received in revised form 14 July 2013 Accepted 18 July 2013 Available online 24 August 2013 Keywords: Moisture damage Nano-organosilane Fourier Transform Infrared Spectroscopy Resilient modulus Indirect tensile strength Tensile strength ratio Fracture energy abstract The objective of this research study was to evaluate moisture susceptibility of hot mix asphalt (HMA) with and without Zycosoil as a nano-organosilane anti-stripping additive and hydrated lime in the form of slurry. Moisture resistance was evaluated on mixtures prepared with two sources of aggregate: lime- stone and siliceous. The base bitumen used was AC 60–70 grade, and two anti-stripping additives. The functional characterization of the base bitumen with and without Zycosoil was analyzed by means of Fourier Transform Infrared Spectroscopy (FTIR). The performance of HMA mixtures under multiple freeze–thaw cycles was evaluated through the following tests: resilient modulus; indirect tensile strength; tensile strength ratio and fracture energy. The findings of this research indicate that use of both additives enhanced the resilient modulus ratio of the mixtures. It was also observed that the effects of anti-stripping additives on specimens made by siliceous aggregate are more pronounced than those pre- pared with limestone aggregates. Fracture energy results also proved that use of Zycosoil additive will increase adhesion bond between the aggregates and asphalt binders, and in turn influences the moisture resistance of the mixture to moisture damage. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The moisture damage of asphalt mixtures is defined as the pro- gressive loss of functionality of the material due to loss of the adhesive bond between the asphalt binder and the aggregate sur- face [1]. Penetration of moisture in asphalt mixtures reduces strength and stiffness of asphalt mixtures and prone the mixtures to develop various forms of premature pavement distress. The pre- mature deterioration of asphalt pavements caused by moisture in asphalt mixtures includes stripping, raveling, and hydraulic scour. Additional distresses provoked by moisture in asphalt mixtures are: rutting, alligator cracking, and potholes [2]. The presence of water in pavements can be detrimental if combined with other environmental factors such as freeze–thaw cycling [3]. The chemical and physical interactions that occur between bitumen and aggregate at the interface are influenced by freeze– thaw cycling over extended periods of time. Among these interac- tions affected by freeze–thaw cycling are those influencing adhe- sive strength [4]. To alleviate or to control the deformations due to water dam- age, various researches were performed leading to the utilization of anti-stripping additives. Anti-stripping additives are used to increase physico-chemical bond between the bitumen and aggre- gate and also to improve wetting by lowering the surface tension of the bitumen. The additives that are used in practice or tested in the laboratory include: (i) traditional liquid additives, (ii) metal ion surfactants, (iii) hydrated lime and quick lime, (iv) silane coupling agents, and (v) silicone. Among them, hydrated lime 0950-0618/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.conbuildmat.2013.07.030 ⇑ Corresponding author. Address: Iran University of Science & Technology (IUST), Hengam Ave., Narmak 16844, Iran. Tel.: +98 21 77240399; fax: +98 21 77240398. E-mail address: ameri@iust.ac.ir (M. Ameri). Construction and Building Materials 48 (2013) 1009–1016 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat