Mechanical assessment and environmental life-cycle analysis of modified waste rubber concretes Masoud Bakhtiari ghaleh ( m.bakhtiari-ghaleh@cv.iut.ac.ir ) Date of Submission Department of Civil Engineering Isfahan University of Technology, Isfahan 84156-83111, Iran Degree: M.Sc Language: Farsi Supervisor’s: Dr. Payam Asadi ( payamasadi@cc.iut.ac.ir ) Dr. mohammadreze eftekhar ( eft@cc.iut.ac.ir ) The finding best solve the proper disposal of the waste tire rubber (WTR) is one of the major environmental issues in the world. tockpiling, landfilling, and burning of scrap tires are dangerous and unsustainable ways to dispose the WTR for this environmental issue; and they can create serious environmental problems. Therefore, the reuse of waste tire rubber is one of the sustainable approaches for recycling WTR. Replacing WTR with part of natural materials in cement composites is one of the economically acceptable ways to reuse WTR. Thus, the use of WTR instead of aggregates in cement-based concretes has been expanded to produce lighter and more ductile concrete with more damping. However, it creates weaknesses in the mechanical properties of concrete such as: density, static modulus of elasticity, dynamic modulus of elasticity, compressive strength and flexural strength. This study proposes an innovative surface double pre-coating with resin and micro-silica to improve the bond at the Interfacial Transition Zone (ITZ) between Waste Tire Crumb Rubber (WTCR) and cement paste, resulting in significantly enhanced the mechanical properties of Rubberized Concretes (RC) .The Experimental results demonstrate that the compressive and flexural strength of the Rubber Modified Concrete (RMC) by Surface Modification Methods (SMM) improved up to 60% and 30%, respectively, compared to Rubber Unmodified Concrete (RUC) containing Unmodified Rubber (UR) .The waste tire Crumb Rubber aggregate (WTCR) replaced Natural Fine Aggregates (NFA) by volume ranging from 0% to 30%.The results show that the most proper (SMM) to enhance the mechanical performance of (RC)were Double-Pre-Coating (DPC) method with resin and micro-silica. The specimens were evaluated from the environmental point of view with the scoring coefficients provided by BEES and EPA. The results show that by increasing the amount of crumb rubber in the concrete containing crumb rubber, the negative effects and environmental scoring increased. It has also increased significantly with the use of environmental impact prevention methods. Key words: aste Tire Crumb rubber concrete; Crumb rubber; Tire rubber; Surface treatment; Pre-coating Method; Tire Rubber Concrete; Rubberized concrete; Rubber modified concrete; Surface modification; Enhancement method; Mechanical properties; Polyurethane resin; Epoxy resin; Micro-Sili ca.