Title:
Effect of Ultra-High-Performance Concrete on Pullout Behavior of High-Strength Brass-Coated Straight Steel Fibers
Author(s):
Kay Wille and Antoine E. Naaman
Publication:
Materials Journal
Volume:
110
Issue:
4
Appears on pages(s):
451-462
Keywords:
equivalent bond strength; single-fiber pullout; straight fibers; ultra-high-performance concrete (UHPC); ultra-high-performance fiberreinforced concrete (UHP-FRC).
DOI:
10.14359/51685792
Date:
7/1/2013
Abstract:
The objective of this research was to investigate the pullout behavior of straight high-strength steel fibers embedded in different ultra-high- performance concretes (UHPCs) with a compressive strength ranging from 190 to 240 MPa (28 to 35 ksi). Particular attention was placed on obtaining matrixes with high packing density to enhance the physicochemical bond with the embedded fiber. The parameters investigated included the use of different sand ratios, silica fume (SF) and glass powder with different mean particle sizes, different superplasticizers, and the addition of hydrophilic or hydrophobic nanosilica particles. Thus, by tailoring the matrix composition, significantly different bond stress versus slip-hardening behaviors were achieved. This is atypical for straight smooth steel fibers, which are normally characterized by a bond-slip softening behavior. Microscopical studies revealed that scratching and delaminating of the brass-coated fiber surface by fine sand and by abrading matrix particles is one reason for this phenomenon, and help explain the maximum equivalent bond strength observed of up to 20 MPa (2.9 ksi).