Study on the mechanical properties and prediction model of ultra-high performance concrete containing aeolian sand and recycled mixed powder

This paper addresses the feasibility of the synergistic preparation of ultra-high performance concrete (UHPC) with recycled mixed powder (RMP) and aeolian sand (AS). In this paper, UHPC was prepared by replacing cement (0, 10%, 20%) and river sand (RS) (0, 15%, 30%, 45%) with RMP and AS (by mass). The optimized mix design of UHPC was based on the Modified Andreasen & Andersen particle packing model. The compressive, flexural, and splitting tensile strengths of different formulations of UHPC were tested. The results show that RMP and AS have a synergistic effect on the strength improvement of UHPC. When the content of RMP is 10% and the content of AS is 30%, the compressive, flexural, and splitting tensile strengths of UHPC are 131.85 MPa, 18.46 MPa, and 11.81 MPa, respectively, which increase with the largest improvement by 9.56%, 8.91%, and 8.25%, compared with the control group. The ultra-fine particles (VFP) (<175 mu m) in AS adequately fill the pores generated by larger RS particles, and the void fraction of fine aggregate (FA) is minimized when the AS content is 30%. Moreover, a compressive strength model based on the pozzolanic activity effect was established. Finally, by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses, it is found that RMP and AS can not only promote hydration nucleation and improve the hydration rate of cement, but also enhance the adhesion and occlusal force between the matrix and aggregate and improve the microstructure of the matrix and interfacial transition zone (ITZ). The results of this paper have reference value for the eco-friendly development of UHPC.