Flexural properties of high ductility cementitious composites with totally recycled fine aggregate

摘要

The natural fine aggregate was totally replaced by recycled fine aggregate (RFA) containing crush dust to prepare recycled high ductility cementitious composites (R-HDCC) for making full use of waste concrete and obtaining better properties. A total of 45 slab specimens in 15 groups were manufactured to systematically investigate the effects of RFA particle size distribution, RFA-binder ratio (R/B), water-binder ratio (W/B), fiber volume fraction (Vf), fly ash content (FA/B) and fiber length (Lf) on the flexural properties of R-HDCC through the third-point test. The results showed that the specimens with the RFA containing crush dust and smaller particles performed best due to the denser matrix. The specimens with a moderate R/B of 0.4 had the highest peak flexural stress whereas the specimens with a smaller R/B of 0.2 had a higher ductility and energy absorption ability. The peak flexural stress and ductility decreased with the increase in W/B, but the fiber strengthen effect was greatest for specimen with a moderate W/B of 0.35. The peak flexural stress of specimen increased continuously as Vf increased from 0 to 2.0% whereas the ductility and energy absorption ability reached maximum when Vf increased to 1.5%. Small amount of fly ash could slightly improve the peak flexural stress of specimen while the achievement of higher ductility and energy absorption ability needed a higher FA/B. Finally, the prediction models of peak flexural stress and ductility ratio of R-HDCC were proposed, which showed good agreements with test results.