Study on the bond properties between basalt fiber-reinforced spontaneous combustion coal gangue concrete and BFRP bars

Abstract

Microstructural characterization of spontaneous combustion coal gangue (SCCG), the hydration products and mechanism of spontaneous combustion coal gangue concrete (SCCGC) were discerned through microscopic analysis. The bond performance was assessed employing a central pull-out test on samples variably substituted with SCCG (0%, 25%, 50%, 75%, and 100%) and augmented with basalt fiber (BF) (0%, 0.1%, 0.15%, and 0.2%). The failure mode and bonding mechanism were also revealed by this test. The bond-slip curves were fitted by various bond-slip constitutive models and a suitable model was found for each section. As indicated by the results, SCCGC possessed a lower carbon content and higher Al and Si element contents. These elements would undergo secondary hydration reactions with CH, which could enhance the strength of the ITZ and the compactness of the bond interface between BFRP bars and concrete. The failure modes were splitting and pull-out. An inverse correlation was observed between bond strength and the increment in SCCG aggregate substitution, ranging from a decline of 2.6% to 23.1%. As the BF content increased, the bond strength and peak slip increased by 3.9% ∼ 19.7% and 4.0% ∼ 14.6%, respectively. Furthermore, the reinforcing effect of BF on bond strength increased from 3.9% ∼ 10.3% to 8.8% ∼ 19.7% as the SCCG replacement rate increased, which was noticeable. The Malvar model and the Continuous Curve model were the best fitting models for the ascending and descending sections of bond-slip curves, respectively, while the residual stage was well fitted by the Hao Qingduo model.

Keywords:

• Bond strength
• spontaneous combustion coal gangue
• basalt fiber
• BFRP bar
• bond-slip constitutive model

Author contributions statement

Conception and design: Zhenrong Liu, Huaxin Liu; Analysis and interpretation of the data: Zhenrong Liu, Huaxin Liu, Weixing Xu; Drafting of the paper: Zhenrong Liu, Weixing Xu, Beibei Liu; Revising paper critically for intellectual content: Zhenrong Liu, Huaxin Liu, Yue Zhong, Jian Geng, Genjin Liu; Final approval of the version to be published: Zhenrong Liu, Huaxin Liu, Weixing Xu, Beibei Liu, Yue Zhong, Jian Geng, Genjin Liu. All authors agree to be accountable for all aspects of the work.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Zhejiang Provincial Natural Science Foundation of China (Grant No. LQ22E080024), the Natural Science Foundation Project of Liaoning Provincial Department of Education, China (Grant No. JJL201915404), and the Zhejiang Province Department of Education Fund (Grant No. Y202146776).