Effect of using available GGBFS, silica fume, quartz powder and steel fibres on the fracture behavior of sustainable reactive powder concrete

Reactive Powder Concrete (RPC) is a relatively new composite concrete material type. The development of RPC aims to achieve a microstructural improvement primarily through incorporating fine aggregates rather than coarse aggregates, more tightly packed particles, increased toughness, and supplementary cementing materials. Although the RPC has excellent engineering properties, its brittleness is the main drawback that can be mitigated by adding steel fibres. This research aims to assess the efficiency of fibrous RPC made from silica fume (SF), ground granulated blast furnace slag (GGBFS), and quartz powder (QZ). In this context, twelve mixtures comprising a combination of GGBFS (75, 85 and 100%), SF (0, 15 and 30%), QZ (20 and 30%) and steel fibres (1 and 2% by volume) were prepared and examined. The experimental program includes flow test, compressive strength, and fracture toughness test under various modes. Many cracked disc-shaped RPC specimens were subjected to pure (I and III) and mixed (I/III) modes to evaluate the fracture toughness. Besides, the micro-structure properties were analyzed using X-ray diffraction analysis and scanning electron microscope images. The Findings unveiled that increasing QZ from 20 to 30% resulted in a marginal improvement in fracture toughness under all three loading modes. The addition of 15% and 30% SF to the RPC specimen with 1% fibre resulted in a 5.65% and 7.91% increase in fracture toughness under mode I, respectively; the addition of 2% fibre resulted in a 4.51% and 7.75% increment, compared to the reference specimen. The improved mixed mode fracture toughness ranged from 1.09 to 6.88% for a 20 degrees loading angle and 1.35 to 4.33% for a 50 degrees loading angle. Furthermore, increased fracture toughness was measured between 0.71 and 6.63% under pure mode III. It is worth highlighting that the contribution of fibre is remarkable in increasing the fracture toughness than the SF and QZ. Besides, the mode III fracture is more critical and recorded fewer values than the mode I and mixed mode.