Use of Vietnam Steel Slag as Aggregate for Roller-Compacted Concrete Pavement

Abstract

This research was undertaken to investigate the feasibility of using Vietnam electric are furnace (EAF) slag on roller-compacted concrete pavement (RCCP). In this research, EAF slag with size in range of 4.75 - 19 mm sourced from Southern Vietnam was used to replace natural coarse aggregate at three ratios of replacement (i.e. 0%, 50%, and 100%). First of all, the feasibility of using Vietnam EAF slag as aggregate in RCCP was evaluated by the expansion testing. Then, RCCP characteristics made of EAF slag were assessed through the mixing proportions, mechanical properties and durability properties. Moreover, the effect of fly ash on RCCP made with EAF slag aggregate (slag-RCCP) also was studied in this work. Fly ash as cement substitution was used at three levels (i.e. 0%, 20%, and 40%) in the RCCP mixtures. It was observed that the expansion value of EAF slag aggregate caused by hydration reactions is lower than 0.5% that is the limit value given by ASTM D4792. Therefore, Vietnam EAF slag exhibited the volume stability and can be used as coarse aggregate in RCCP after exposing to outdoor condition for several months. Furthermore, it was found that EAF slag used in this study is non-active aggregate by alkali-silica reactions. The results from this study on RCCP showed that the optimum water content of slag-RCCP is higher than that of traditional RCCP. The natural aggregate replacement by EAF slag aggregate resulted in the compressive strength, splitting tensile strength and elastic modulus of RCCP decreased at all ages. The higher the replacement ratio of EAF slag aggregate is, the lower the mechanical properties of RCCP is. And, there was a slight reduction of sulfate resistance of slag-RCCP. Nevertheless, slag-RCCP fulfilled the requirements of pavement. Additionally, the higher abrasion resistance of slag-RCCP in comparison with traditional RCCP was found. On the other hand, fly ash as a partial cement substitution in slag-RCCP resulted in the reduction of mechanical and durability properties at early age. However, the conjunction of EAF slag aggregate and fly ash in the RCCP mixtures improved the mechanical and durability properties in the long-term ages. And, a replacement of 20% fly ash provided slag-RCCP which reached the strength and durability requirements for pavement.