EFFECT OF NATURAL AND ARTIFICIAL WEATHERING ON THE LONG-TERM FLEXURAL PERFORMANCE OF POLYMER MORTARS M. C. S. Ribeiro,* A. J. M. Ferreira,** and A. T. Marques** Keywords: polymer mortars, epoxy and polyester matrices, weatherability, natural and artificial weathering tests The weathering resistance of two different polymer mortar (PM) formulations to strong corrosive environments is analyzed and assessed by means of both natural and artificial weathering tests. In an experimental program, speci- mens of both formulations were exposed to the natural environment during one year at a maritime site in the middle of Portugal. In another experimental program, by means of a solar box and salt fog chamber devices, the effects of artificial weathering were considered. The flexural strength retained after exposure to the environments was the key parameter for assessing the weatherability of the PM formulations. Acceleration factors, based on a one-year time scale, were determined and employed to predict the flexural strength of the materials under a long-term outdoor ex- posure at a natural maritime site. 1. Introduction Polymer concrete is one of the newest construction materials with a wide range of diverse properties. In this class of materials, a thermosetting resin is used as a binder of natural or artificial aggregates, which replaces the paste of Portland cement/water of conventional hydraulic concretes. A higher strength, an excellent resistance to a chemical at- tack, a reduced water permeability, and greater resistance to the damage caused by freeze-thaw cycles are some of the attractive features exhibited by these composite materials [1]. Other advantages include a fast curing time and the ability to form complex shapes and an excellent finishing, which are significant assets in the production of precast concrete elements [2]. Overlays for pavements and floorings, patching materials for repair and rehabilitation purposes, recycling and waste encapsulation are other well-known and successful applications of these composite materials. In operation, polymer concrete (PC) and polymer mortar (PM) are often exposed to an outdoor environment. Thus, there is a natural concern for the weatherability of these polymer composites, partially because they are rather new materials. Another aspect is related with prediction of their useful life. Sunlight, temperature, moisture, wind, dusts, and pollutants are among the main variables or agents of the weather that cause degradation [3]. Due to a synergistic effect, the combined action of the aforementioned weather components has a higher deterioration power than the sum of the damages caused by them singly if they could act one at a time. Atmospheric pollutants, such as sulphur oxides, hydrocarbons, dust and soot particles, may cause some deterioration, but in combination with solar ra- 515 0191-5665/09/4505-0515 © 2009 Springer Science+Business Media, Inc. *Composite Materials Unit, Institute of Mechanical Engineering and Industrial Management (INEGI), Rua do Barroco 174, 4465-591 Leca do Balio, Por tu gal. M. C. S. Ribeiro is the cor re spond ing au thor; e-mail: cribeiro@inegi.up.pt .**Department of Mechanical Engineering and Industrial Management (DEMEGI), Faculty of Engineer- ing, University of Porto, Rua Dr. Roberto Frias, w/n°, 4200-465 Porto, Portugal. Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 45, No. 5, pp. 739-758, September-October, 2009. Original article submitted February 4, 2008. Mechanics of Composite Materials, Vol. 45, No. 5, 2009