Fracture and tensile characteristics of asphalt-rubber concrete

Fracture and tensile characteristics of asphalt concrete mixtures affect th e structural performance of pavements, particularly under low-temperature c onditions. This paper reports a study of the tensile and fracture propertie s of asphalt-rubber (AR) concrete mixtures that formed the basis for the re commendation of an optimum asphalt mixture design incorporating crumb rubbe r from scrap tires. The work involved a full-factorial experiment with thre e different rubber contents (19, 22, and 24%), and three different AR binde r contents (6, 7.5%, and 9%) in a surface mixture. Fracture and indirect te nsion tests were performed on AR concrete beams and Marshall test samples, respectively, at two different test temperatures of 25 and 5 degrees C.: Th e variables studied were indirect tensile strength, peak center-point load carried, load-point displacement, and unit fracture energy. The results sho w that higher mean values of indirect tensile strength and fracture energy were obtained corresponding to the highest AR binder content (9%), irrespec tive of rubber contents, particularly at lower temperatures. A statistical analysis of the test results reveals that there are no significant differen ces among the means of most of the variables studied corresponding to diffe rent rubber contents. However, the differences are significant for differen t binder contents.