Evaluation of emulsion based warm mixes for paving applications

Abstract

Due to increase in energy costs and emission problems in hot mix asphalt, it brought a great interest to the researchers to develop the warm mix technology for pavement constructions. It is a typical method in the bituminous paving technology, which allows production and placement of bituminous mixes at lesser temperatures than that of hot mix asphalt (HMA), which involves an environmental friendly production process that involves the use of organic additives, chemical additives and water based technologies. In this study an attempt has been made to prepare warm mixes by first pre-coating the stone chips with medium setting bitumen emulsion (MS) and then mixing coated aggregates with VG 30 bitumen at a lower temperature than normally required. These two binders have been taken in equal proportions to form the binder. Three mixing temperatures were maintained, namely temperatures 110°C,
120°C and 130°C. Marshall Samples have been prepared using this methodology with dense bituminous macadam (DBM) and bituminous concrete (BC) gradings as per the specifications of MORTH and subsequently Marshall Properties were studied with the main objective of deciding the type of filler, setting time of emulsion, optimum temperature of mix
preparation and optimum bitumen-emulsion composition forming the binder. In this study it has been observed that out of three mixing temperatures tried, the mixes prepared at 1200C with bitumen-emulsion composition 80:20 for DBM warm mix and 70:30 for BC warm mix offer highest Marshall Stability and highest indirect tensile strength (ITS), while satisfying other Marshall parameters. It is also seen that the optimum binder contents for warm mixes are 5.1% with 80:20 bitumen emulsion composition for DBM warm mix and 4.9% binder with 70:30 bitumen emulsion composition for BC warm mix, each prepared at 120°C. The tensile strength ratio and retained stability parameters are also found to be reasonably satisfactory in such warm mixes, thus prepared. The results of warm mixes are found to be comparable to the HMA.