Effect of steel fibers on the thermal and mechanical properties of cementitious materials containing silicon carbide

It is not easy to simultaneously improve the thermal and mechanical properties of cementitious materials used in energy pile backfill. To study the effect of the percentage of silicon carbide (SiC) replacing fine aggregate (30% and 50%) and different steel fiber contents (0%-1.5% vol.) on the thermal and mechanical properties of cementitious materials, which were characterized by thermal constant test, compressive and flexural strength test, microstructural analysis, infrared thermography, and numerical simulation. The results showed that the thermal conductivity of the specimens increased from 1.8 W/(m center dot K) to 3.8 W/(m center dot K), and the specific heat capacity decreased from 750.1 J/(kg center dot K) to 560.5 J/(kg center dot K). When the SiC substitution ratio was 50%, the 7-day compressive and flexural strength of the specimen decreased by 10.8% and 7%, respectively, compared with the control specimen. Compared to the S50SF0 specimen, the compressive and flexural strength of the specimens containing 0.5-1.5% steel fibers were increased by 51.7-105% and 10.7-74.3% at 28 days, respectively. Infrared thermography tests further verified that the heat transfer efficiency of the specimens containing SiC and steel fibers was significantly higher than that of the control specimen. Moreover, the change in thermal conductivity has a more dramatic influence on the specimen's heat transfer than the change in specific heat capacity.