Experimental study on mechanical property strengthening and mechanism of sand 3D-printed rock analogs under heat treatment

Sand powder 3D printing technology provides a novel approach for specimen preparation in laboratory rock mechanics tests;however,the mechanical strength of existing sand powder 3D-printed rock analogs remains insufficient. As an important post-treatment method for improving binder curing degree and microstructural characteristics, the strengthening mechanism of heat treatment has not yet been fully clarified. In this study, sand powder 3D-printed rock analogs were investigated through uniaxial compression tests,acoustic emission (AE) monitoring,and scanning electron microscopy (SEM). The strengthening mechanism induced by heat treatment was analyzed from both macroscopic mechanical responses and microscopic structural characteristics. The results show that heat treatment has a significant influence on the uniaxial compressive strength (UCS) of the specimens,and the strength exhibits a non-monotonic variation with increasing heat treatment temperature and duration. The maximum UCS of 52. 37 MPa was achieved under the T120-t5 condition(heat treatment temperature of 120 ℃ and duration of 5 h),representing an increase of approximately 119. 7% compared with the untreated specimens. Appropriate heat treatment promotes binder curing and forms continuous and dense bonding structures on the surfaces of sand particles, thereby improving the load-bearing capacity of the specimens. However,excessive heat treatment at 150 ℃ reduces the stability of the bonding structure and induces thermally induced stress cracks,resulting in deterioration of mechanical properties. The variations in mechanical properties of sand powder 3D-printed rock analogs are closely related to the competition between binder strengthening and thermal damage effects,and their interaction governs the mechanical response after heat treatment.