85 >> back to Table of Content NHL 3.5 MORTARS WITH SCRAP TIRE RUBBER Faria, P. 1 *; Piteira, R. 2 * 1* : ICIST, CERIS, Department of Civil Engineering, NOVA University of Lisbon Email: paulina.faria@fct.unl.pt 2* : Department of Civil Engineering, NOVA University of Lisbon Email: r.piteira@campus.fct.unl.pt Key words: Mortar; Rubber; Natural hydraulic lime; scrap tire rubber. Abstract : The use of wastes and industrial by-products as building materials is an important issue in order to decrease costs with waste management and the embodied energy of building products. Scrap tire rubber has been studied as aggregate for cementitious materials. Natural hydraulic limes are natural binders with particular characteristics of both air and hydraulic binders. Their specifications became stricter with the last version of EN 459-1:2010. In this study scrap tire rubber was used as additional aggregate of mortars based on NHL3.5 and natural sand. Different particle size fractions and proportions of scrap tire rubber were used: a mix obtained almost directly from industry (only after sieving for preparation of particle sizes similar to mortar aggregate) and separated fine, medium and coarse fractions; 0%, 18%, 36% and 54% weight of binder, corresponding to 2.5%, 5% and 7.5% weight of sand. The influence of the rubber´s additions on the mortars´ fresh state, mechanical and physical performance is presented, namely by flow table consistency, water retention, fresh bulk density, dynamic elasticity modulus, flexural and compressive strength, open porosity and bulk density, capillary absorption, drying and thermal conductivity. The use of the rubber mix coming from the waste tire industry seems advantageous and may open possibilities for use as raw material by the mortars industry. 1 Introduction The progress of technology brought to the society more requirements relative to living standards. Due to this improvement, there are direct environmental issues associated that did not exist a century ago. One of the biggest issues is the recycling of tires. This problematic is a big concern, because there are legal procedures that do not allow their fire burst in open air or its dump in landfills. Retreading companies try to avoid part of this problem, enlarging the life cycle of used tires, replacing the used tire tread for a new one. However, this procedure leads to another one: what to do with the scrap tire rubber waste? These companies agglomerate the waste and have very little use to it (IGAOT 2007). In recent years, the construction field tried to apply this waste in various manners, such as pavements (artificial turfs or roads), cementitious mortars (Eiras et al. 2014) and concrete (Thomas et al. 2014). Studies performed on scrap tire rubber concluded that the rubber is an elastic waste that can provide some deformability and improve thermal characteristics to cement- based mortars, although the mechanical characteristics could be compromised (Al–Akhras et al. 2002). Natural hydraulic limes (NHL) are natural binders with particular characteristics of both air and hydraulic binders, that can be very beneficial in several types of application, namely when applied on the rehabilitation of buildings. NHL specifications became stricter with the last version of EN 459-1 (CEN 2010a) and some limes previously named NHL have been reclassified as natural lime HL. EN 459-1 NHL are only produced in few countries of the world, namely in Portugal. Because of the previous reasons the study of the properties of natural hydraulic lime NHL 3.5 mortars have recently regain the interest of the scientific community (Grilo et al. 2014a; Grilo et al. 2014b). Very few studies address the characterization of mortars with scrap tire rubber and the majority of