394 Revista Română de Materiale / Romanian Journal of Materials 2015, 45 (4),394 -401 EFECTUL ÎNLOCUIRII AGREGATULUI CU GRANULE DIN CAUCIUC PROVENITE DIN ANVELOPE UZATE ASUPRA PROPRIETĂŢILOR MECANICE ALE BETONULUI THE EFFECT OF THE AGGREGATE REPLACEMENT BY WASTE TYRE RUBBER CRUMBS ON THE MECHANICAL PROPERTIES OF CONCRETE IONUŢ-OVIDIU TOMA, NICOLAE ŢĂRANU ∗ , OANA-MIHAELA BANU, MIHAI BUDESCU, PETRU MIHAI, RAREŞ-GEORGE ŢĂRAN 1 Universitatea Tehnică “Gheorghe Asachi” din Iaşi, Str. Prof.dr.doc D. Mangeron, nr 67, Iaşi, 700050, România The growing amount of waste rubber produced from used tires has resulted in an environmental problem needed to be addressed. The paper investigates the effect of fine aggregate replacement by waste tyre rubber crumbs on the mechanical properties of concrete at different curing ages. The aim is to assess the suitability of the newly obtained material to load bearing elements in civil engineering. The results presented in the paper are part of a larger research project related to the innovative use of all tyre components in concrete. The percentages considered were 40%, 60% and 80% by volume of fine aggregate. The general trend is a decreasing one in terms of mechanical properties. Even in such cases, the obtained values are above the minimum requirements, prescribed by norms, in terms of strength for some structural elements. The complete stress- strain curves determined at the age of 28 days show a softer descending trend for rubberized concrete compared to the reference mix. The embedded strain energy is larger in the post-peak region. Cantitatea mereu crescândă de cauciuc provenit din anvelopele uzate a condus la o problemă de mediu care trebuie soluţionată. În lucrare este investigat efectul înlocuirii părţii fine a agregatului din beton prin granule din cauciuc asupra proprietăţilor mecanice a betonului la diferite vârste de întărire. Principalul scop constă în evaluarea oportunităţii noului material la realizarea elementelor portante din ingineria civilă. Rezultatele expuse în lucrare reprezintă o parte din cadrul unui proiect de cercetare referitor la utilizarea inovatoare a componentelor anvelopelor uzate în elemente din beton. În lucrare se analizează influenţa înlocuirii părţii fine de agregat cu granule din cauciuc în proporţie de 40%, 60% şi 80% din volum. Tendinţa generală observată în cadrul programului experimental constă în descreşterea valorilor caracteristicilor mecanice. Totuşi, valorile obţinute depăşesc cerinţele minime prevăzute în norme pentru calculul de rezistenţă al elementelor structurale. Curbele caracteristice complete determinate la 28 de zile indică o descreştere atenuată în cazul betonului cauciucat comparative cu betonul obişnuit, iar energia potenţială înglobată este mai mare pe porţiunea descendentă a diagramei tensiune-deformaţie specifică. Keywords: rubberized concrete, modulus of elasticity, compressive strength, complete stress-strain curve 1. Introduction The innovation in the construction industry is driven by both the need of reducing the environmental footprint [1, 2] and by the increasing demand of lowering the costs [3]. This can only be achieved by a constant and sustained innovation process which should also anticipate the future environmental constraints [4, 5]. The use of rubber crumbs obtained from recycled tyres could represent a significant resource for the construction industry, tremendously reducing its environmental footprint. Researchers realized the huge potential of the RC construction industry for embedding significant quantities of industrial wastes. According to the latest report of European Tyre and Rubber Manufacturers Association [6], the European countries produced in 2013 roughly 4.67 million tonnes of tyres representing approximately 25% of the world production. From these, an average of 58% reached their end of life. It is estimated that in 2012 alone, 2.765 million tonnes of used tyres were generated. During 2004 – 2012 the average rate of worn tyre recuperation was 89%. Over the last 19 years, the combination of material and energy recovery of ELTs (End of Life Tyres) increased from 31% to 76% of total used tyres treatment while in the same time period landfilling decreased to only 6% (compared to nearly 50% in 1996). Out of the 1.05 million tonnes used for material or embedded ∗ Autor corespondent/Corresponding author, E-mail: taranu@ce.tuiasi.ro