Effect of spatial distribution of polymer fibers on preventing spalling of UHPC at high temperatures. (February 2021)

• Record Type: Journal Article
• Authors: Zhang, Dong; Zhang, Yao; Dasari, Aravind; Tan, Kang Hai; Weng, Yiwei
• Is Part Of: Cement and concrete research. Volume 140(2021)
• Publication Date: 2021-02
• Subjects: Thermal spalling -- Ultra-high performance concrete -- PP fibers -- X-ray computer tomography -- Percolation; Cement -- Periodicals; Cement -- Research -- Periodicals; Concrete -- Periodicals; Concrete -- Research -- Periodicals; Ciment -- Périodiques; Béton -- Périodiques; Cement; Concrete; Periodicals; 620.135
• DOI: 10.1016/j.cemconres.2020.106281
• Languages: English
• ISSNs: 0008-8846

Abstract

Abstract: Polypropylene (PP) fibers are commonly used for the prevention of thermal spalling of ultra-high performance concrete (UHPC). In this work, the effect of fiber distribution on permeability and spalling resistance is investigated and an analytical model for permeability at 150 °C is proposed. This model, considering the parameters like fiber dimensions, dosage, and percolation, is based on Kozeny-Carman equation. It was found that the percolation of the interconnecting fiber network resulted in a significant increase in permeability of UHPC. X-ray tomography data on the three-dimensional spatial distribution of fibers reiterated that fiber aspect ratio and dosage (and fiber number density) were critical in increasing the fiber connectivity (percolation). It was also found that a vapor permeability of larger than 0.6 × 10 −16 m 2 at 150 °C could eliminate spalling. Further, based on a semi-empirical approach, aspect ratio between 300 and 600 was recommended for spalling prevention with a fiber dosage of 0.3–0.4 vol%.