Improved Maxwell model with structural dashpot for characterization of ultraslow creep in concrete

Abstract

Ultraslow creep follows a logarithmic law, which exists in high strength self-compacting concrete. The traditional and fractal derivative rheology models can respectively capture exponential and power law behaviors, but are not capable of characterizing ultraslow creep. The Lomnitz model is feasible to describe ultraslow creep, but it is an empirical model without clear physical meaning. In this study, an improved Maxwell model is developed to describe ultraslow creep behavior based on structural dashpot, which is constructed by using the local structural derivative. The structural Maxwell model provides a physical interpretation of the Lomnitz model. The creep deformations of a high strength self-compacting concrete at the early ages of 12 h, 16 h, 20 h, and 24 h are used to test the structural Maxwell model. The results show that the structural Maxwell model can accurately fit the experimental data, and the values of the goodness of fit for the structural Maxwell model and the Lomnitz model are much closer to 1. The creep processes of the self-compacting concrete at the ages of 12 h, 16 h, 20 h, and 24 h belong to ultraslow dynamics, and can well be interpreted by using the structural Maxwell model.