VARIATIONS IN THE SURFACE FREE ENERGY (SFE) OF MODIFIED ASPHALT BINDER UNDER THE INFLUENCE OF TESTING

Additives can modify and enhance the important properties of asphalt binder. An attempt was made in this work to use four types of additives (sulfur, fumed silica, Phosphogypsum and fly ash) to alter the properties of asphalt binder. The modified asphalt cement binders were tested for static and dynamic contact angles determination and SFE evaluation using the Sessile drop (SD) and the Wilhelmy plate (WP) techniques. It was noticed that the SFE increased by (33.4, 51.5, 98.1, 114.4, and 77.3) % for control, (sulfur, fly ash, fumed silica, and phosogypsum) modified mixtures respectively when WP method was used as compared to that of the SD method. The use of the additives increased the base component element of static contact angle (SCA) by (5.15, 24.1, 38.7, 44.3) % for sulfur, fly ash, silica fumes, and Phospho-gypsum additives respectively while the Lifshitz-van der Walls (LW)component element increased by (13.4, 12.2, and 24) % for fly ash, silica fumes, and Phospho-gypsum additives respectively when compared with that of the control binder, However, implementation of sulfur exhibit decline in the LW component element of SCA of 2.1 %. Implementation of sulfur shows significant increase in the dynamic contact angle (DCA)of (67, 42, and 67.7) % and for LW, base, and acid components respectively, while implementation of phosogypsum showed an increase in the DCA components of (18.3, and 10.8) % for LW, and acid components respectively. Sulfur additive exhibits the highest SFE, and it is recommended for modification of the asphalt binder.