Effect of the Welan Gum Biopolymer on Rheological Properties and Storage Stability of Bitumens

The welan gum, as a biopolymer, is commonly used in the cement mortar to control bleeding and prevent segregation due to its long-chain molecules. This paper studied the effect of welan gum on the rheological behavior of base bitumen and the storage stability of bitumen modified with montmorillonite (MMT). Four contents (0.2, 0.5, 1, and 3 % by weight) of welan gum were used to mix with base bitumen at a suitable temperature of 160 degrees C. The dynamic shear rheometer was adopted to evaluate the viscosity as the function of shear rate. The results indicated that the welan gum, especially with 0.5 % by weight, notably reinforced the shear-thinning behavior of base bitumen at 135 and 160 degrees C. It implied that the welan gum can improve the drainage resistance of asphalt mixture during storage and transportation. Based on this result, the storage stability of MMT modified bitumens with and without 0.5 % welan gum by weight was characterized by the difference in the complex modulus (G*) and the phase angle (delta) of bitumen sampled from the top and bottom layer of the storage tube. The result indicated that the welan gum can apparently improve the storage stability of the MMT modified bitumen.