An assessment of GO addition to an NHL binder

Natural Hydraulic Lime (NHL) binders are generally preferred to those cement-based in case of restoration works, thanks to their good compatibility with historical substrates. Moreover, they can be considered more sustainable in comparison to cement, being sintered at lower temperatures. Nonetheless, while having a good compatibility with historic substrates, their performance might need improvement in terms of strength values and strength development without sensibly affecting their stiffness.
To this purpose, the incorporation of Graphene Oxide (GO) was considered, due to the beneficial effects showed by studies on cementitious binders. This work presents the characterization of NHL pastes (i.e. without aggregates) prepared with a water-to-binder ratio of 0.5 and 3 different dosages of GO retrieved from literature about cement and concrete, namely 0.01%, 0.06% and 0.12% by weight of NHL dry powder.
The NHL powder and the reacted binder were characterized via X-ray Powder Diffraction (XRD) and Scanning Electron Microscopy (SEM). From a mechanical standpoint, indirect tensile and compressive strengths were tested at 28 and 84 days of age, while stiffness was assessed via Ultrasonic Pulse Velocity (UPV) at 7, 14 and 28 days of age.
Preliminary results showed a minor strength improvement, which was more apparent at 84 days of age, with no remarkable modification of the stiffness. Results also indicates that it might be worth testing possible greater dosages of GO.