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Abstract: This study investigates the effects of fly ash and silica fume on the mechanical properties and microstructure characteristics of interfacial transition zone (ITZ) between macro-synthetic fiber and the bulk matrix of the fiber reinforced concrete. The experimental results show that the concrete is able to withstand significant post-cracking loads and undergo remarkable deflections under flexural loads due to the bridging effect of macro-synthetic fiber. The mechanical properties of concrete incorporating fly ash plus silica fume are much better than those prepared with no mineral admixtures or mono addition. The work of adhesion is an integrated index to evaluate the bonding behaviors between fiber and matrix, which exhibits a trend similar to that noted in the flexural toughness. The compound addition of fly ash and silica fume presents the most distinct improvement effects on microstructure of ITZ and the bonding behaviors between fiber and matrix. The amount of hydrated calcium silicate (C-S-H) gel and compaction of ITZ play key roles in the fiber - matrix interfacial bond and the mechanical properties of concrete.
DOI: 10.6135/ijprt.org.tw/2015.8(2).94
Key words: Fiber reinforced concrete; Interfacial transition zone; Macro-synthetic fiber; Microstructure; Mineral admixtures.
(ProQuest: ... denotes formulae omitted.)
Introduction 12
Reinforcements with fiber have proven to be an effective and economical way to eliminate the brittle failures of concrete structures under dynamic loads [1-3]. Randomly distributed fibers were employed to enhance the resistance to both crack initiation and propagation [3, 4]. Moreover, the positive effects of fibers on ductility, energy absorption and toughness were also investigated. The mechanical properties of fiber reinforced concrete (FRC) are mainly dependent on the performance of fiber, matrix, and fiber-matrix interface. Due to the wall effect and bleeding, the matrix at the vicinity of fiber surface shows higher porosity compared to the bulk matrix, forming an interfacial transition zone (ITZ) between the fiber and the bulk matrix. Therefore, a sound knowledge of the fiber-matrix interaction is of key importance for predictions and design of the optimum mechanical properties of composite materials [5, 6].
Because of its important role in cementitious composite materials, the performance of ITZ between fiber and matrix has been studied extensively. Caggiano et al. [5] proposed a unified formulation for simulating the overall bond behavior of fibers embedded in cementitious matrices...