Fractional-order model of the compressive strength of hydraulic concrete in a real temperature and humidity environment

Concrete is a kind of composite material that is in a plastic flow state in its initial stage, gradually hardening with the cement hydration reaction and then finally reaching a relatively stable condition. In addition, the compressive strength of concrete is related to not only the curing age but also the curing temperature and humidity. The Kelvin model with a software element is used to describe the growth rule of the compressive strength of concrete. The equivalent age theory is used to consider the coupling effect of the temperature and humidity, and then a fractional-order model of the compressive strength of hydraulic concrete considering this coupling effect is proposed. Next, tests of the compressive strength of concrete under three different curing conditions for different concrete ages are performed, and a fractional-order model of the compressive strength is implemented using the test data. The analysis results show that the fitting effect of the fractional-order model can reach a high level of accuracy with only a few model parameters, and with a better fit than the combinatorial exponential model or combinatorial modified logarithmic model.