The effect of recycled plastic aggregate on chemico-physical and functional properties of composite mortars Barbara Liguori a,⇑ , Fabio Iucolano a , Ilaria Capasso b , Marino Lavorgna b , Letizia Verdolotti b a Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, Università di Napoli Federico II, Naples, Italy b Istituto per i Materiali Compositi e Biomedici, Consiglio Nazionale delle Ricerche, Portici, Naples, Italy article info Article history: Received 2 July 2013 Accepted 2 January 2014 Available online 11 January 2014 Keywords: Recycling of plastic waste Recycled aggregate Composite mortar Thermal degradation Fire properties abstract In this paper the interaction mechanism between recycled plastic aggregates and lime matrix in compos- ite mortars was investigated by means of thermal, morphological and Fourier Transform Infrared Spec- troscopy (FTIR) analyses. In order to assess the fire behavior of the composite mortars, a cone calorimeter method was adopted. The plastic aggregate, mainly made of polyolefin and polyethylene terephthalate, is obtained from an industrial waste, through a process that provides a plasticization and densification by extrusion of plastic waste. Several composite mortars were prepared by replacing silica powder with 10%, 15% and 20% of recycled aggregate. Experimental results attest that, even if the filler was not chemically modified, there is a good chemical interaction between the plastic aggregate and mortar, involving a reduction of the negative effects on physical and functional properties of the mor- tar composites, such as thermal degradation and fire resistance. In fact all the specimens showed a scarce sensitivity to flashover, and can be classified as low risk materials. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction A large development in the consumption of plastic is observed in the recent years, which leads to an increase of the production of plastic-related waste. Recycling appears as one of the best solu- tion for disposing of plastic waste, due to its economic and ecolog- ical benefits. In particular the use of this type of waste in the construction field may represent an effective response both to the problem of reducing the environmental impact of plastics and to the development of an increasingly sustainable building industry [1,2]. A lot of works have been already done on the use of these materials in manufacturing of cement [3] and concrete [4], as part of the binder or as aggregate substitute [4]. Polypropyl- ene (PP) [5,6], polyethylene (PE) [7], polyethylene terephthalate (PET) [8] and other materials [9] are examples of polymers used in building industry either in fiber or powder shape. In a previous paper [10] the plastic waste substitution was opti- mized in terms of physical, mechanical and thermal performance of the resulting mortars. The experimental mortars have shown a strong potential as a base of green building materials, adding to the typical qualities of a natural hydraulic lime (e.g. widespread availability, low energy consumption during production, perme- ability, and dehumidifying capacity) further features such as the low thermal conductivity. In fact the composite mortars have showed values of thermal conductivity of less than 50% compared to a traditional mortar. Several authors [11–13] explored the use of light aggregate based on polymeric waste, as a material in reducing the unit weight, the cost, the brittleness and the thermal insulation properties of building materials such as concrete or mortars. How- ever, these aggregates exhibit a series of drawbacks, mainly due to their poor chemical compatibility with inorganic matrix. The inho- mogeneity between the two phases which causes defects in the internal structure of the inorganic matrix, can result in: (a) a reduc- tion in fresh mortar workability, (b) a decrease in mechanical per- formances, such as strength and stiffness and (c) a worsening of thermal properties, such as a reduction of thermal degradation temperatures and fire resistance. Furthermore, when adding an organic material, it is essential to assess the fire behavior of this kind of composite mortar. There are several methods for determining the fire performance of materials in building applications, specified in many international standards [14,15 and ASTM:E119]. The cone calorimeter has emerged in re- cent years as the most widely used apparatus for this purpose. In fact it has been demonstrated that the cone calorimeter is suitable for measuring heat release rate (HRR) from materials and products with low heat content [16]. The heat release rate represents the most important variable to characterize the ‘‘flammability’’ of a product and its consequent fire hazard [17]. Therefore, this paper aims to investigate the bond mechanism between the plastic aggregate and lime matrix by means of thermal, morphological, FTIR analyses and fire behaviour. 0261-3069/$ - see front matter Ó 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.matdes.2014.01.006 ⇑ Corresponding author. Address: Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, Università di Napoli Federico II, P.le V. Tecchio, 80 – 80125 Naples, Italy. Tel.: +39 0817682395; fax: +39 0817682394. E-mail address: barbara.liguori@unina.it (B. Liguori). Materials and Design 57 (2014) 578–584 Contents lists available at ScienceDirect Materials and Design journal homepage: www.elsevier.com/locate/matdes