Research On The Preparation, Performance And Application Of Basic Oxygen Slag Based Aspahlt Concrete

Steel slag including basic oxygen furnace slag (BOF) is one of the largest amount of solid waste in the world. Its environmental friendly treatment and reutilization are one of the researching hot spots. At the moment high-speed development of road construction in China makes asphalt pavement a promising field for reasonable reutilization of BOF in large amounts.This paper is to systematically investigate the composition, structure and performance of BOF and its related asphalt mixture. Modern testing approaches were used to characterize BOF, including XRD, SEM, XRF. EPMA, TG-DSC and mercury injection. The investigation of endothermic property for BOF indicated the main wrongdoer for dramatic decrease of BOF production was the dust on it. instead of its specific heat capacity. BOF was thermal-stable and not harmful to environment. Innovatively. results showed that BOF was porous. Also the results of bulk-impregnate test indicated that the asphalt absorption of BOF was time dependent at a decreasing rate. The final absorption is almost two times as its instant absorption, based on what the predicting regression model for related absorptive characteristic of asphalt mixture was estabilished and had good correlation with experiment results. With spherical model, the author introduced a new method to determining specific surface factors of aggregates.The specific surface area factors of BOF were significantly less than the ones specified in Chinese norm JTG F40-2004.Dynamic creep test and four-points bending test were carried out. The permanent deformation behavior was dominated by temperature and exhibited three-stage rheological properties, which could be modeled precisely. The fatigue life at0℃of BOF based asphalt mixture was superior to that of limestone based asphalt mixture.The investigation based on the interface properties between BOF and asphalt was carried out to investigate the moisture sensitivity and accelerated damage mechanisms of BOF based asphalt mixture.The results of pull-off test exhibited that the bond strength and fracture energy between asphalt and BOF are both superior to those with basalt or granite. Also dissipated Creep Strain Energy limits (DCSEf). master curve of dynamic modulus and fatigue life all indicated the BOF based asphalt mixture exhibited less moisture damage. The new designed dynamic moisture treatment was cast on asphalt mixture and results showed that the fatigue life of BOF based asphalt mixture was superior to that of basalt based asphalt mixture. With regression analysis by fitting the dynamic modulus master curve, the author found that the dynamic modulus within higher frequency of BOF based asphalt mixture decreased significantly. Mechanisms analysis showed that the generation of hydrated calcium silicate, calcium hydroxide and calcium sulfate took the major responsibilities duringr destruction of BOF based asphalt mixture.Slag residue can be used as an antistripper in asphalt mixture. There was only physical adsorption instead of chemical reaction between slag residue and asphalt. The equilibrium radius model showed that slag residue exhibited the largest’equilibrium radius’ than limestone filler, which represented its strong ability to adsorb asphalt.The storage condition of BOF aggregates should be attached much more attention to maintain clean and dry. Much work should be done on the preventing of the clogged screens during aggregate crushing. Keeping BOF aggregate dry is the major solution to prevent thermal segregation during compaction and rolling of asphalt mixture.