Abstract:

To investigate the synergistic enhancement effects of silica fume and glass fiber on the mechanical properties of fully recycled coarse aggregate concrete （FRCAC）， natural coarse aggregates were fully replaced by recycled coarse aggregates to prepare FRCAC. Different content of silica fume （0%， 5% and 10%， mass fraction， the same below） and glass fiber （0%， 0.5%， 1.0% and 1.5%， volume fraction， the same below） were incorporated. The workability and mechanical properties （cubic compressive strength， splitting tensile strength， and flexural strength） of FRCAC were systematically tested， and its microstructure was analyzed using scanning electron microscopy （SEM）. The results indicate that the synergistic effect of silica fume and glass fiber significantly enhances the mechanical properties of FRCAC. When the silica fume content is 10% and the glass fiber content is 1.0%， the 28 d cubic compressive strength， splitting tensile strength， and flexural strength of FRCAC increased by 26.1%， 49.2%， and 45.5%， respectively， compared to the control group without silica fume or glass fibers. Silica fume， through its filling effect and the formation of C-S-H gel via secondary hydration reactions， not only densifies the cement matrix but also improves the structure of the interfacial transition zone between the glass fibers and the cement matrix. This enhancement allow the crack-bridging and resistance effects of the fibers to be fully utilized. This study provides a theoretical support for advancing the resource utilization of construction waste.

Key words: fully recycled coarse aggregate concrete, silica fume, glass fiber, workability, mechanical property, microstructure