Abstract
The formulation of ultra-high performance (UHPC) concrete is characterized by the presence of fine inert and reactive filling materials to cement with proper superplasticizer and low water-to-cement ratio. In this study, the use of crystalline nanocellulose (CNC) and carbon nanotube (CNT) to reinforce the flexural resistance of the cementitious matrix at the nano level is investigated. CNC and CNT were utilized in the presence of hybridized polyvinyl alcohol (PVA) microfibers with either macrosteel or microsteel fibers of different physicomechanical properties. Additionally, fine aggregates of a maximum particle size of 4 mm and two types of desert sands were incorporated and evaluated in the presence of fly ash (FA) and silica fume (SF). The use of FA has led to an improvement in workability with elevated compactness integrated with SF nanoparticles. The optimal combination of aggregates with maximum packing density was selected in the mix composition. The effect of CNC and CNT on the temperature evolution profiles and superplasticizer dosage on the setting time was individually evaluated. The results have confirmed that there had been a limited zone of accepted workability with CNC, after which a substantial workability loss was noticed. Macrosteel fibers have limited content, after which a remarkable reduction in compressive strength becomes evident in contrast to the microsteel fibers that can be incorporated in much higher contents. The image analysis technique was used to support the interpretation of data. It is concluded that the utilization of fine aggregates of a maximum particle size of 4 mm has limited the properties of UHPC mixes.