Mechanical performances and microstructures of ultra-high performance concrete incorporating spent fluid cracking catalyst under various curing regime: A comparative study

In this study, the effect of five varying curing regimes (standard curing, 60 °C, 90 °C, 1 MPa, 2 MPa) and spent fluid cracking catalyst (SFCC) dosage (10–30 % by weight of cement) on the mechanical property, hydration kinetics and microstructural development of UHPC (ultra-high performance concrete) was studied. The outcomes shown that the aluminum phase in SFCC is activated to participate in the pozzolanic reaction under thermal curing. This resulted in the generation of more C-A-S-H in the UHPC. Thus, the mechanical performances of UHPC containing SFCC under autoclave curing were better than its mechanical properties under standard curing at 180 d. Furthermore, the generation of additional C-A-S-H would also enhance the polymerization degree and mean molecule chain-length of hydration products of UHPC with SFCC. Moreover, the microstructure of UHPC will be significantly deteriorated in excessively high temperatures and pressures, the microstructure deterioration of UHPC containing SFCC is more obvious due to the porous structure of SFCC.