Experimental Study of Cyclic Loading and Unloading Creep of Hydraulic Concrete: A Statistical Perspective

Concrete is a complex composite material. Even if hydraulic concrete is creep-tested under uniform test conditions, the magnitude relationship between the tensile and compressive creep properties of concrete is still affected by the randomness of the aggregate distribution and inhomogeneity of mortar during the formation of the specimen. Therefore, we designed and implemented eight groups of cyclic loaded and unloaded creep tests of secondary aggregate grading hydraulic concrete under uniform test conditions. Based on the standard definition of the concrete compressive strength and the creep test results, the standard specific creep curve is defined by the upper limit statistics of the specific creep at the reliable probability of 85%. This work thus statistically explores the magnitude relationship between the tensile and compressive standard specific creep of hydraulic concrete. The results show that, with increasing loading time, the tensile and compressive creep of the concrete gradually becomes less discrete. At the beginning of the test, the tensile and compressive creep produced highly discrete results, and the dispersion coefficient exceeded 25%. Over time, although the discreteness decreased, it remained above 8%. In addition, the discreteness of the second stage loading exceeded that of the first stage. The 85% reliable probability comprehensively reflects the average value and discreteness of the test data. The standard specific tensile creep of hydraulic concrete under the 85% reliable probability exceeds the standard specific compressive creep.