# Prediction of the Time-Dependent Elastic Modulus of Fly-Ash Concrete Under Sustained Loads

## TL;DR

This paper studies how fly ash concrete's elastic modulus changes over time under sustained loads and proposes a model to predict these changes.

## Contribution

A new prediction model for the time-dependent elastic modulus of fly ash concrete under sustained loads is proposed.

## Key findings

- Elastic modulus increases for fly ash concrete under sustained compressive load.
- The model incorporates hydration and aggregate concentration effects under load.
- Parameter analysis shows the influence of initial loading age and loading level.

## Abstract

In this paper, the time-dependent properties of the elastic modulus of fly ash concrete under sustained compressive load were studied. An experiment was conducted and showed an increment of elastic modulus for two types of fly ash concrete (20% and 40% fly ash replacement) under sustained load. The mechanisms of this increment were analyzed, and two Representative Volume Elements (RVEs) were established to represent the micro-heterogeneous space of binder and concrete based on continuum mechanics. The shrinking core models of hydration and pozzolanic reaction were adopted to quantify the volume fraction of each phase within the binder RVE. A prediction model was proposed by incorporating the effects of extra hydration and time-dependent aggregate concentration rate under sustained load. Finally, parameter analysis including the influences of initial loading age and the loading level was conducted.