Influence of Volume-to-Surface Area Ratio on the Creep Behavior of Steel Fiber Ceramsite Concrete Beams

To explore the influence of the volume-to-surface area ratio (V/S) on the creep of ceramsite concrete beams, the creep performance of ceramsite concrete beams with different V/S was studied through a long-term deformation observation test, theoretical derivation analysis and finite element modeling. First, by observing the creep deflection of ceramsite concrete beams with five different V/Ss for 180 days, the relationship between creep deflection and loading time as well as the influence of V/S on creep deflection were obtained. Then, referring to the ACI209 and ACI435 creep coefficient calculation formula, the creep theory of ceramsite concrete beams involving V/S was established. Finally, the numerical model was built according to the test parameters. The results showed that the growth rate of the creep of ceramsite concrete beams increased rapidly in the early stage, but gradually slowed down with the passage of time and tended to be stable after 120 days of loading. The V/S had a significant impact on the creep of ceramsite concrete beams. In the first 7 days, the creep growth rate of each beam was approximately the same. Thereafter, the higher the V/S was, the lower the creep became. After 28 days, the creep of ceramsite concrete beams with varied V/Ss showed sharp differences. After the V/S exceeded 30, the increasing V/S could effectively reduce the creep value and the creep growth rate under a long-term load. The calculated results were in good agreement with the measured values, which fully reflected its creep variation. The finite element simulation further verified the influence of V/S on the creep of ceramsite concrete beams and the reliability of the creep calculation formula.