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Title: Splitting of Concrete with Steel, Glass Fiber-Reinforced Polymer, and Basalt Fiber-Reinforced Polymer Bars Exposed to MgSO4

Author(s): Yail J. Kim and Yufei Chai

Publication: Structural Journal

Volume: 117

Issue: 3

Appears on pages(s): 3-16

Keywords: bond; deterioration; durability; fiber-reinforced polymer (FRP); interface; magnesium sulfate; performance-based design

DOI: 10.14359/51726799

Date: 5/1/2020

This paper presents the splitting characteristics of concrete interfaced with various reinforcing bars when subjected to magnesium sulfate. Glass and basalt fiber-reinforced polymer composites (GFRP and BFRP, respectively) and conventional deformed steel bars are employed, and their performance is comparatively studied. Interface test specimens are prepared and submerged in a magnesium sulfate solution at a 5% concentration for 10 weeks. Based on the gray level co-occurrence matrix (GLCM) method, microscopic investigations are conducted to examine the surface texture of these reinforcing bars. The initiation and progression of splitting cracks are visually assessed by digital image correlation (DIC). The measured potential of hydrogen (pH) indicates that the concrete reacts with magnesium sulfate, which permeates through the cement paste and weakens the concrete-reinforcement interface. The surface morphology of the reinforcement controls the interfacial behavior together with the condition of the concrete substrate deteriorated by the solution. The capacity reduction rate of the BFRP bars is the least among the three reinforcing types, although the load-carrying capacity of the steel is higher than that of the GFRP and BFRP. The fracture energy of the interface is quantified, and its spatial distribution is elaborated. The developed analytical model predicts the circumferential stress and internal pressure of the test specimens, which are crucial to understand the splitting mechanism of the interface. The random uncertainty of the reinforcing bars interacting with the concrete deteriorated by magnesium sulfate is appraised. For design recommendations, environmental reduction factors are calibrated as per reliability performance.