Physical and Marshall Properties of Borogypsum Used as Filler Aggregate in Asphalt Concrete

For construction of roads and highways, a large amount of aggregate usage is needed. Because the natural aggregate resources are limited, the demand for the use of alternative aggregates has increased. For this reason, borogypsum in Turkey was used as a mineral filler aggregate in hot-mix asphalt concrete. When this is directly released to nature as boron waste, it may cause various environmental problems. In order to prevent this waste's harmful effects to the environment, the use of borogypsum as an alternative aggregate in highway engineering may be effective. For this purpose, the physical properties of borogypsum were investigated by thermogravimetry differential thermal analysis (TG-DTA), x-ray diffraction (XRD), and scanning electron microscope energy dispersion analysis of x-ray (SEM-EDAX). Also, the surface properties of borogypsum were identified by polarized optical microscope (POM). In this study, two groups of hot-mix asphalt concrete were obtained. For the first group, asphalt concrete was produced with limestone aggregate, and for the second one, borogypsum was used as mineral filler in asphalt concrete. In both groups, limestone was used as fine and coarse aggregate. Marshall stability and other mechanical properties were determined. It is believed that the evaluated borogypsum has a similar crystal structure with tincalconite and its usage for hot-mix climate regions may be effective to reduce problems. Also, another crucial finding is that using borogypsum as a mineral filler aggregate in asphalt concrete can be convenient for the binder course of pavements exposed to heavy traffic potential. DOI: 10.1061/(ASCE)MT.19435533.0000580. (C) 2013 American Society of Civil Engineers.