Moisture Damage Analysis of Bituminous Mix by Durability Index Utilizing Waste Plastic Cup

Abstract

Moisture damage is a major problem in every tropical country that may occur in pavement structures during their design life due to inappropriate selection of aggregates and bitumen from a material point of view. Silica content of aggregates and existence of carboxylic acids in bitumen of the hot mix asphalt (HMA) are suspected to play a crucial role in such damage. The application of polymer-modified bitumen (PMB) may be an effective solution against such problems, as suggested by different investigations. However, high tariffs on PMB decreases the interest of construction agencies, particularly for constructing low-budget bituminous pavement. To address this issue, this study uses elastomeric municipal solid waste (MSW) composed of thermoplastic elastomers based on polypropylene (PP) in the form of plastic cups (PCs) to modify virgin bitumen. This research outlines a method to quantify the moisture susceptibility of the virgin and PC-modified bituminous mixes by second durability index (SDI) using a modified Marshall immersion test due to its applicability in wider temperature-fluctuation ranges. A gradual decrease of stability loss in the SDI curve from 0- to 7-day immersion periods is observed due to short chain propagation of PP in bituminous medium up to 2% by weight PC-modified bituminous mix in the wet process. However, experimental results of this investigation show that addition of 2% by weight PCs to the bituminous mix in the wet process gives the lowest moisture damage (i.e., 9.38%), which may lead to a longer life span of the bituminous mix by resisting the moisture damage of the constructed pavement.