Effects of recycled PET fibres on the mechanical properties and seawater curing of Portland cement-based concretes Fernando Fraternali ⇑ , Saverio Spadea, Valentino P. Berardi University of Salerno, Department of Civil Engineering, Viale Ponte don Melillo, 84084 Fisciano, SA, Italy highlights  We present an experimental study on the mechanical properties and seawater curing of RPETFRC.  We examine compressive strength, first crack strength, and energy absorption capacity of RPETFRC.  Special attention is given to the influence of the mix-design on RPETFRC properties.  The presented results show that seawater conditioning significantly lowers the ultimate ductility of the analysed RPETFRC.  The same conditioning instead leads to minor modifications of the compressive strength and first-crack strength. article info Article history: Received 9 January 2014 Received in revised form 12 March 2014 Accepted 17 March 2014 Keywords: PET FRC Crack Ductility Toughness Durability Seawater curing abstract This paper deals with an experimental study on the mechanical properties of recycled polyethylene tere- phthalate fibre-reinforced concrete (RPETFRC) and its durability in an aggressive seawater environment. A Portland limestone cement-based concrete with a 0.38 water/cement ratio is used to cast cubic and prismatic specimens, in association with two different PET fibres obtained through extrusion of recycled PET flakes (R-PET). Some of these specimens were conditioned in the Salerno harbour seawater for a per- iod of 6/12 months. Compressive strength and four-point bending tests are performed in order to inves- tigate the mechanical properties of such RPETFRCs. Comparison of the present results and those in the literature for air-cured RPETRCs highlights the influence of the analysed R-PET fibres on the mechanical properties of concretes showing different water/cement ratios and binders. The given results for seawa- ter-cured specimens demonstrate that such a curing condition slightly modifies the first-crack strength and markedly reduces the toughness of the RPETFRCs examined in the present work. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction The attention towards an effective recycling of post-consumer plastics in different industrial sectors has grown considerably over the past two decades. The interest in plastic waste materials mainly originates from environmental reasons, due to the fact that post-consumer plastics are the most relevant wastes with a low rate of biodegradation, and in consideration of the severe environ- mental problems created by the disposal of such materials in land- fills, or their floating in the ocean. On the other hand, in recent years, it has been shown that recycled plastic can be profitably used to manufacture low-cost aggregates and/or reinforcing fibres of cementitious materials in the construction industry (refer, e.g., to [1–10] and therein references). It is well known that plain cementitious mixes may suffer considerable shrinkage during cur- ing and can be affected by diffuse cracking. The addition of a suit- able amount of reinforcing fibres to the mix design can effectively contrast such phenomena, leading to significant increases in the material toughness and durability [11–13]. Nowadays, fibre-rein- forced concretes (FRCs) are widely employed for industrial floors, tunnel coatings, and the retrofitting of structures exposed to chem- ical attacks or undergoing structural rehabilitation. Natural (cellu- lose, carbon, cotton, coconut, agave, jute, etc.) or synthetic (steel, polypropylene, polyethylene, polyester, nylon, Kevlar, etc.) rein- forcing fibres are frequently used. It has been recognized that plas- tic fibres offer several advantages over more traditional steel fibres, including: markedly lower weight for equal volume content; lower transportation costs; higher corrosion resistance, major imperme- ability of the fibre-reinforced concrete; enhanced compatibility with additives; lower thermal conductivity; higher workability; http://dx.doi.org/10.1016/j.conbuildmat.2014.03.019 0950-0618/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +39 089964083; fax: +39 089964045. E-mail address: f.fraternali@unisa.it (F. Fraternali). Construction and Building Materials 61 (2014) 293–302 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat