ANTIOXIDANT IN BITUMEN

Conventional virgin bitumen used in road pavement construction is susceptible to aging problem. Aging, or in its scientific term; oxidation reaction, occurs due to the presence of oxidizing agents (free radicals) that are formed during oxidation reaction in the bitumen. Oxidation in bitumen can cause an increase in asphalt viscosity as well as harden the bitumen, eventually loses its flexibility making it brittle and prone to cracking. This however can be counteracted by mixing the bitumen with antioxidant materials. In this project, the antioxidant material used is rice husk powder (75-micron size). The material contains lignin compound which could slows down the oxidation process via electron donation, preventing the free radicals from reacting with asphaltene (a vital compound in bitumen), and hence, prolong the lifespan of the bitumen. Not only the lignin-containing rice husk is environmental friendly, they are also cost-effective material since production price of rice husk powder is relatively cheaper than any other production of available bitumen modifier in the market. In this project, a total of three (3) types of modified bitumen have been prepared; virgin bitumen, 5%-containing rice husk bitumen, and 10%-containing rice husk bitumen. Two (2) laboratory aging tests which is Rolling Thin-Film Oven (RTFO) and Pressure Aging Vessel (PAV) tests have been conducted to simulate the aging of bitumen; short-term aging and long-term aging respectively. To support the evidence of antioxidizing properties of antioxidants towards virgin bitumen, a total of two (2) physical tests; Penetration Test and Softening Point Test have been conducted before and after the laboratory aging tests. From the laboratory tests results, the rice husk potential in term of improving current bitumen‟s service life are proven by analyzing the physical changes before and after the aging process of all samples. Up to this point, the rice husk bitumen possess better quality in term of lower rate of bitumen degradation (hardening effect), lesser amount of volatiles lost during short-term aging, and possess low temperature susceptibility value.