Effects of fly ash on the mechanical and impact properties of recycled aggregate concrete after exposure to high temperature

Abstract

Experiments were conducted on 180 specimens to investigate the mechanical and impact properties of recycled aggregates (RAs) concrete with different fly ash (FA) contents after exposure to temperature at 20 °C (room temperature), 200 °C, 400 °C, 600 °C and 800 °C. The compressive strength, elastic modules, peak strain, ultimate strain, Poisson’s ratio and recovering effect of air curing time on the tested specimens were analysed. The impact numbers and impact energy under the repeated drop-weight test were obtained. Test results showed that the numbers of blows causing the first and final crack decreased gradually with the increasing temperature and FA contents, and the temperature of 200 °C had a great influence on the impact resistance of RA concrete. The weight loss and compressive strength of the specimens suffering from high temperature alone decreased with the increasing FA content. The compressive strength of unheated specimens for 118 days curing was about 0.045–0.196% higher compared to that for only 28 days curing. The Poisson’s ratio of RAs concrete at 400 °C was less than half of that at 20 °C. Results of this study provided certain theoretical basis for research on fire-resistant design of concrete structures.

Keywords:

• Recycled aggregate concrete
• fly ash
• high temperature
• mechanical properties
• Poisson’s ratio
• impact resistance

Acknowledgments

The authors are grateful for the financial supports provided by all of those sponsors.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was sponsored by the China’s National Natural Science Foundation of China (grant 51108371), the Key Laboratory of the Shaanxi Province Department of Education (grant 16JS050), the Opening Funds of State Key Laboratory of Building Safety and Built Environment (grant BSBE2016-02), and Innovation Team of Xi’an University of Architecture and Technology.