Ecological and mechanical properties of ultra high performance – Fiber reinforced cementitious composites containing high volume fly ash

Ultra High Performance – Fiber Reinforced Cementitious Composites (UHP-FRCC) has successfully developed in the last decades. They show excellent mechanical properties and durability, due to the highly dense microstructure produced by extremely low water/binder ratio and large amounts of cement. Thus, replacing part of the cement content with High Volume Fly Ash (HVFA) could be an effective way to improve also the ecological properties of UHP-FRCC. Indeed, most of the carbon footprint of cement-based composites is caused by the CO₂ production of cement manufacturing. On the other hand, HVFA tends to reduce the mechanical properties of UHP-FRCC, especially at the early age. To evaluate the effect of some cement replacement (20, 50 and 70% by weight), a series of uniaxial compression and tensile tests have been performed and described in this paper. At the same time, through the Eco-Mechanical Index (EMI), ecological performances are evaluated on the basis of the measured mechanical properties. As a result, the application of UHP-FRCC in full-scale structures (e.g., composite concrete columns) is really convenient in the presence of HVFA, although the material properties (the compressive strength, in particular) show an opposite trend.