Effect of curing regimes on mechanical properties and microstructure of ultra-high performance concrete with full aeolian sand

The fine particle size and high water absorption capacity of aeolian sand are significant factors limiting its comprehensive application in ultra-high performance concrete (UHPC). To effectively overcome the shortcomings of aeolian sand (AS) and rapidly enhance the strength of UHPC with full aeolian sand (ASUHPC), this study investigated the influence of various curing regimes on the physico-mechanical and microstructure of ASUHPC. The experimental findings indicate that with increasing curing temperature and duration, the mechanical properties of ASUHPC are enhanced. Specifically, water-bath curing or steam curing at 90 degrees C for 48 hours results in flexural strength exceeding 35 MPa and compressive strength surpassing 150 MPa within the initial 7 days. Conversely, dry-heating curing diminishes the beneficial effects brought about by increased temperatures. Microstructural analysis reveals that thermal curing promoted the formation of a more dense network or honeycomb structure of C-S-H gel. Both steam curing and water bath curing are beneficial to reduce the defects caused by the adsorption of more water on the surface of eolian sand particles, thereby enhancing the interfacial transition zone between the aeolian sand and the matrix. Moreover, with the increase of curing temperature and duration, the dissolution degree of aeolian sand increases. However, excessively high steam curing temperatures can impede its dissolution. This research highlights the critical role of a suitable curing protocol in the fabrication of ASUHPC, providing valuable insights for advancing UHPC usage in regions rich in aeolian sand resources.