Assessment of fiber factor for the fracture toughness of polyethylene fiber reinforced geopolymer. (14th February 2022)

• Record Type: Journal Article
• Authors: Zhang, Ning; Yan, Chenyu; Li, Li; Khan, Mehran
• Is Part Of: Construction & building materials. Volume 319(2022)
• Publication Date: 2022-02-14
• Subjects: Polyethylene fiber -- Geopolymer -- Fracture -- Toughness -- Fiber factor; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2021.126130
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: DIC is used to observe the deformation process of the PFRG. Fiber factor is Introduced as an index to evaluate PE fiber. Fiber factor increases, fracture toughness first increases and then decreases. Fracture toughness calculation model of PFRG is established. Abstract: The influence of polyethylene fiber and water-binder ratio on the fracture properties of high toughness geopolymer is studied in this paper. Polyethylene fibers with 6 vol fractions (0, 0.25%, 0.45%, 0.65%, 0.85%, 1.05% and 1.25%) and different lengths (6 mm and 12 mm) were mixed into geopolymers having various water-binder ratios (0.35 and 0.38). A total of 26 experimental groups of polyethylene fiber reinforced geopolymer (PFRG) for notched beams were set up to observe the development process of displacement and deformation field during the three-point bending test by digital image correlation (DIC). The length, width, and height of the specimen were 160 mm, 40 mm, and 40 mm, respectively, with the initial crack length of 10 mm. The fracture test loading was displacement control, and the loading rate was 0.5 mm/min. The results indicated that the fiber factor (product of fiber length-diameter ratio and volume fraction) for PFRG can describe the comprehensive effect of fiber length and content. The literature shows that the fiber factor effectively improves the fracture performance of concrete materials, but the fracture toughness does not monotonously increase with the increase of the fiber factor. The fracture toughness of PFRG increased first and then decreased with the increase of fiber factor. The gain ratio of initial cracking toughness and unstable fracture toughness was reached to 4.395 and 6.332, respectively. Particularly, the optimum fiber factor can be set as 580.65. The fracture toughness of PFRG with a water-binder ratio of 0.35 was generally greater than that of 0.38. The gain ratio of unstable fracture toughness was greater than that of initial cracking toughness. This increased gain ratio indicates that the polyethylene fiber fully exerts its crack resistance effect only after the cracks appear in the specimen. By comparing the fracture toughness gain ratio of this paper with other literature, it is found that polyethylene fiber has a good toughening effect on geopolymer. Additionally, a fracture toughness prediction model was established via regression analysis, considering fiber factor and water-binder ratio as independent variables. The dense fiber factor F d of polyethylene in this paper can be set as 600, which is higher than that of the other fibers due to its greater stiffness.