Creep failure of alkali activated slag concrete in compression: Effect of loading age and stress level

With the rapid advancement of 3D printing, concrete is required to bear significant stress loads during its early-age period. The high stress creep failure behavior is directly associated with the structural stability and build ability requirements of 3D printed concrete elements during layer deposition. Nonlinear creep manifests in concrete subjected to high stresses. This process results in the accumulation of damage, which culminates in creep failure of concrete materials. However, limited information exists on this phenomenon in alkali-activated slag concrete. In this study, the creep failure of alkali-activated slag concrete under high uniaxial stress was investigated, and the creep failure characteristics of alkali-activated slag concrete were obtained. Additionally, the effects of loading age and stress ratio were investigated. The failure mechanism, creep coefficient, and nominal Poisson’s ratio of alkali-activated slag concrete specimens were investigated. Findings indicated that as age increases, the influence of loading age on the nonlinear creep of alkali-activated slag concrete progressively diminishes. Stress levels significantly affect the nonlinear creep of alkali-activated slag concrete. Specifically, when the stress level reached 0.95 f c , the alkali-activated slag concrete specimen failed after sustaining the load for a few seconds. During the creep phase, the circumferential creep coefficient and nominal Poisson’s ratio of the specimen exhibited a substantial increase, with the circumferential creep coefficient markedly exceeding the axial creep coefficient. Furthermore, the specimens exhibited significant lateral expansion upon destruction. Non-destructive and crack analyses were conducted to identify the creep-failure mechanism. The creep-failure study indicated that the propagation of microcracks inside the specimen influenced the nonlinear creep and creep-failure characteristics of alkali-activated slag concrete specimens subjected to high sustained compressive stress. The deterioration of the adhesive substance between particles progressively culminated in extensive fractures, which resulted in creep failure. • The creep failure behavior of alkali activated slag concrete was studied. • The effect of loading ages and stress ratio was investigated. • The non-destructive and crack analysis were conducted to identify the creep failure mechanism.