Effect of Elevated Temperature on Mechanical Properties of High-Volume Fly Ash-Based Geopolymer Concrete, Mortar and Paste Cured at Room Temperature

Jun Zhao; Kang Wang; Shuaibin Wang; Zike Wang; Zhaohui Yang; Eskinder Desta Shumuye; Xinglong Gong

doi:10.3390/polym13091473

Effect of Elevated Temperature on Mechanical Properties of High-Volume Fly Ash-Based Geopolymer Concrete, Mortar and Paste Cured at Room Temperature

Polymers (Basel). 2021 May 2;13(9):1473. doi: 10.3390/polym13091473.

Authors

Jun Zhao^{1

2}, Kang Wang¹, Shuaibin Wang¹, Zike Wang², Zhaohui Yang³, Eskinder Desta Shumuye¹, Xinglong Gong^{2

4}

Affiliations

¹ School of Civil Engineering, Zhengzhou University, Zhengzhou 450001, China.
² School of Mechanics and Safety Engineering, Zhengzhou University, Zhengzhou 450001, China.
³ School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164, USA.
⁴ CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, China.

Abstract

This paper presents results from experimental work on mechanical properties of geopolymer concrete, mortar and paste prepared using fly ash and blended slag. Compressive strength, splitting tensile strength and flexural strength tests were conducted on large sets of geopolymer and ordinary concrete, mortar and paste after exposure to elevated temperatures. From Thermogravimetric analyzer (TGA), X-ray diffraction (XRD), Scanning electron microscope (SEM) test results, the geopolymer exhibits excellent resistance to elevated temperature. Compressive strengths of C30, C40 and C50 geopolymer concrete, mortar and paste show incremental improvement then followed by a gradual reduction, and finally reach a relatively consistent value with an increase in exposure temperature. The higher slag content in the geopolymer reduces residual strength and the lower exposure temperature corresponding to peak residual strength. Resistance to elevated temperature of C40 geopolymer concrete, mortar and paste is better than that of ordinary concrete, mortar and paste at the same grade. XRD, TGA and SEM analysis suggests that the heat resistance of C-S-H produced using slag is lower than that of sulphoaluminate gel (quartz and mullite, etc.) produced using fly ash. This facilitates degradation of C30, C40 and C50 geopolymer after exposure to elevated temperatures.

Keywords: elevated temperature exposure; fly ash and slag blend; geopolymer; mechanical properties; micro-structure.