Multi-Scale Investigation of Microstructure, Fiber Pullout Behavior, and Mechanical Properties of Ultra-High Performance Concrete with Nano-CaCO₃ Particles


The mechanical properties of a fiber-reinforced concrete are closely related to the properties of the matrix, fiber, and fiber-matrix interface. The fiber-matrix bond property is mainly governed by the adhesion between the fiber and surrounding cement materials, as well as the strength of materials at the interfacial transition zone. In this paper, the effect of nano-CaCO3 content, varying between 0 and 6.4%, by mass of cementitious materials, on microstructure development, fiber-matrix interfacial bond properties, and mechanical properties of ultra-high performance concrete (UHPC) reinforced with 2% steel fibers were investigated. The bond properties, including bond strength and pullout energy, were evaluated. Mercury intrusion porosimetry (MIP), backscattered electron microscopy (BSEM), optical microscopy, and micro-hardness testing were used to characterize the microstructure of matrix and/or interfacial transition zone (ITZ) around an embedded steel fiber. Test results indicated that the incorporation of 3.2% nano-CaCO3 significantly improved the fiber-matrix bond properties and the flexural properties of UHPC. This was attributed to densification and strength enhancement of ITZ as observed from micro-structural analyses. Beyond the nano-CaCO3 content of 3.2%, the fiber bond and mechanical properties of UHPC decreased due to increased porosity associated with agglomeration of the nano-CaCO3.


Civil, Architectural and Environmental Engineering


The authors would like to acknowledge the financial support of the National Science Foundation of China (Nos. U1305243 and 51378196) and the RE-CAST University Transportation Center (No. DTRT13-G-UTC45) at Missouri University of Science and Technology (Missouri S&T).

Keywords and Phrases

Bond strength (materials); Calcium carbonate; Calcium compounds; Concretes; Fibers; High performance concrete; Mechanical properties; Mercury (metal); Microhardness; Microstructure; Reinforced concrete; Reinforced plastics; Steel fibers; Steel testing; Backscattered electron microscopy; Fiber-matrix bonds; Interfacial transition zone; Mercury intrusion porosimetry; Nano-CaCO3; Statistical modeling; UHPC; Ultra high performance concretes; Fiber reinforced materials; Fiber-matrix bond properties; Statistical model

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Article - Journal

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© 2018 Elsevier, All rights reserved.

Publication Date

01 Feb 2018