Tensile creep performance and modeling of ultra early-age cement paste under high stress levels

This study conducted tensile creep tests on ultra early-age (from initial setting to final setting) cement specimens under high stress levels. The results revealed that cement specimens exhibit two types of deformation under high stress: stable deformation and failure deformation. Specimens with lower water-cement ratios are more prone to creep failure at earlier loading ages. At the same stress level, the creep strain of cement specimens is proportional to the water-cement ratio but decreased with the loading age. Higher stress levels result in greater creep rates and shorter holding times to creep failure for the cement specimens. The coupling effect of flow deformation due to water movement and damage deformation due to micro-crack accumulation are the main causes for creep. For specimens with stable deformation, the movement of adsorbed water into larger capillary pores and the consequent sliding of solid particle surfaces are the main reason for creep development; while for specimens undergoing destructive deformation, the propagation of microcracks is the main factor. The study established an ultra early-age tensile creep model by integrating the Abel dashpot element and a variable viscosity dashpot element in series. The parameters in the model have practical physical significance and can reflect the rheological evolution and micro-crack development characteristics of cement specimens.