SOME APPLICATIONS OF NUCLEAR-MAGNETIC-RESONANCE IMAGING TO CRUMB RUBBER-MODIFIED ASPHALTS

Nuclear magnetic resonance (NMR) imaging methods have been applied to study the behavior of crumb rubber materials in asphalt. Pieces of nat ural tire rubber and styrene-butadiene tire rubber were immersed in a high acid-content asphalt and heated at 170 degrees C for different pe riods of time up to 48 h. After heating, 3D images were acquired durin g cooling and after the samples were at room temperature. Images of th e natural and styrene butadiene rubber in asphalt, taken at room tempe rature after heating, showed a progressive loss of image intensity wit h increased heating time. From an NMR perspective the loss of signal c ould be due to the rubber having become more rigid as a result of heat ing, or because of possible dissolution of the rubber by the asphalt. However, images of the same samples, taken while the samples were at a n elevated temperature, showed that the crumb rubber materials had swe lled in the presence of the asphalt. Samples of the same materials in the absence of asphalt were heated and imaged in the same manner. Imag es of these samples showed only a small loss of signal with heating an d hardly any swelling. (C) 1998 Elsevier Science Ltd. All rights reser ved.