Bending Properties of High-Early-Strength Fiber Reinforced Concrete


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Title: Bending Properties of High-Early-Strength Fiber Reinforced Concrete

Author(s): Antoine E. Naaman and Fadi M. Al-Khairi

Publication: Special Publication

Volume: 159


Appears on pages(s): 351-374

Keywords: bending; ductility; fiber reinforced concretes; flexural strength; high-early-strength cements; high-performance concretes; polypropylene fibers; silica fume; toughness; Structural Research

Date: 2/1/1996

This paper provides a summary of part of the results of SHRP project C-205 on the Fresh and Hardened Properties of High Early Strength Fiber Reinforced Concrete (HESFRC). HESFRC was defined as achieving a minimum target compressive strength of 5 ksi (35 MPa) in 24 hours. Fresh HESFRC properties included air content, inverted slump test, temperature, and plastic unit weight. Tests on the mechanical properties included compressive strength, elastic modulus, flexural strength, splitting tensile strength, and fatigue life. Seventeen different combinations of parameters were investigated for each type of test. The main parameters included: (1) three different matrix mixtures (one control, one with silica fume, and one with latex), (2) two different volume fractions of fibers (1 percent) and (2 percent), (3) two fiber materials (steel and polypropylene), (4) two steel fiber lengths corresponding to aspect ratios of 60 and 100 respectively, and (5) hybrid mixes containing either an equal amount of steel and polypropylene fibers, or an equal amount of steel fibers of different lengths. The compression and the bending tests also included a time variable; the compressive properties were measured at ages 1, 3, 7, and 28 days, and the bending properties at ages 1, 7, and 28 days respectively. Information from the compression tests comprised the compressive strength, the elastic modulus, and the strain capacity. Information from the bending tests included the modulus of rupture and the toughness indices as per ASTM standards. Optimum mixtures that satisfied the minimum compressive strength criterion, and showed excellent values of modulus of rupture, toughness indices in bending, and fatigue life in the cracked state are identified. Potential applications in repair, rehabilitation, or construction of transportation structures are suggested. In this paper a description is given of key results of the bending tests only.