Electrical Monitoring of Setting and Hardening of UHPC/UHPFRC with Graphene

Setting and hardening of ultra-high-performance concrete (UHPC) and ultra-high fiber reinforced concrete (UHPFRC) have been monitored with electrical conductivity in laboratory experiments with an equipment suitable for in-field remote sensing. Key parameters permitting to identify key stages during cement hydration could be determined. The electrical conductivity mildly changed during the fluid state, remaining at relatively high levels. During setting and early hardening, a sharp transition was observed toward much lower conductivity values. In the late-hardening further conductivity reduction occurred. The contribution of graphene has been investigated in those identified stages, showing both in UHPC and UHPFRC an effect to accelerate the fluid to solid transition and to mitigate the conductivity reduction in the late hardening stage. The role of fibers has also been investigated.