Experimental investigation on asphalt mixtures containing plastic waste

We live in a world in which almost every single plastic piece created still exists because this material lasts for about four centuries. It became an environmental issue that could be contrasted with some actions in daily activities, personal and professional. That means that is a problem everyone should face also in the professional area, for that reason this thesis will describe one way in which the civil engineering can approach the previous formulated problem: it is possible to construct asphalt roads having a percentage of waste plastic, treated in particular ways that improve some of the properties of the road such as the resistance, stability and durability. Nowadays it is possible to find some scientific research that analyze how the plastic waste influence the mixture with the aggregates and bitumen and it is possible also to find some implementations in rural roads in some countries as India and the United Kingdom. This document has the objective to prove if the local domestic waste, from Turin, Italy, is usable to produce the asphalt for the road construction. This will be evaluated in an experimental way in the Politecnico di Torino, road materials laboratory in DIATI department. For the experiments it will be used two types of plastic: the first one will be a High-Density Polyethylene and the second one will be a blend of some domestic plastic waste composed by PET-1, LDPE-4, PP-5 and PS-6. The first step was focused on the determination of the geometrical properties and characterization of the aggregates available in the laboratory, where three different types of materials were provided, sieve analysis and maximum density tests were performed in each type. Then, a mix design was carried out by finding an adequate aggregate gradation and optimal binder content that satisfy the requirements proportioned at the beginning of these activities. Once having the optimal mixture design, were prepared five different mixtures of which, one mixture was prepared as a control mixture without addition of waste plastic, three mixtures with addition of shredded waste plastic polyethylene (PE) by varying the percentage of plastic by weight of aggregates in 0.27%, 1.5% and 5%, and the other mixture with an addition of shredded waste plastic with 1.5% by weight of aggregates using a mixture of waste plastic recycled and treated in a manual and domestic way. There were compacted six cylindrical specimens by means of the gyratory shear compactor for each mixture mentioned before. The volumetric properties of each mixture, maximum density and bulk density, were evaluated to find the air voids content of each of them since this is a parameter of such importance that it is related to many of the distresses that occur in the asphalt pavements. The results were compared with the control mixture without addition of plastic to evaluate the influence of the addition of shredded plastic in a bituminous mixture. Finally, mechanical tests were performed on all cylindrical specimens of the five bituminous mixtures for which some specimens were conditioning in water at elevated temperatures and the rest were dry specimens. The test were indirect tensile stiffness modulus test and indirect tensile strength test and was determined the water sensitivity of each mixture by means of the indirect tensile strength ratio. All the results were compared with respect the control mixture without plastic and between them to assess the behavior when adding shredding plastic and their implications in terms of stiffness