Pt-Pd Bimetallic Nanocomposites Catalyst Formed on Graphene Surface: Preparation and high-performance for Methanol Electro-Oxidation

Ultra high performance fiber concrete (UHPFC) is an advanced formula concrete that is proven to be more superior than conventional concrete because it embrace the qualities of steel and concrete. Therefore UHPFC properties which include high durability and strength are fully exploited in the research of rehabilitation and strengthening in concrete and even non-concrete structures. This article presents the findings of an experimental study carried out to examine the bonding strength behaviour between normal concrete (NC) substrate and UHPFC as a repair material, under flexural strength test by using third-point loading beam test method. Three types of NC substrate surface preparation were used: as-cast (without surface preparation) as a reference, wire-brushed, and sand-blasted. The flexural test results clearly indicated that all failures occurred through the NC substrate and no de-bonding was observed in the interface between NC substrate and UHPFC. The results of the flexural strength confirmed that adhesion bond strength between NC substrate and UHPFC was stronger than the substrate regardless, the substrate roughness. This proves that UHPFC is able to link and bond strongly with the substrate.

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Ultra-High-Performance Concrete Shear Keys in Concrete Bridge Superstructures

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198120964725 ◽

2020 ◽

pp. 036119812096472

Author(s):

Elsy Y. Flores ◽

Jordan Varbel ◽

William K. Toledo ◽

Craig M. Newtson ◽

Brad D. Weldon

Keyword(s):

High Performance ◽

Load Transfer ◽

Mechanical Performance ◽

High Performance Concrete ◽

Surface Preparation ◽

Ultra High Performance Concrete ◽

Direct Tension ◽

Girder Bridges ◽

Grouting Material ◽

Shear Keys

This research investigated the use of locally produced, non-proprietary ultra-high-performance concrete (UHPC) as a grouting material to repair deteriorated shear keys. Shear keys are used in adjacent girder superstructures to produce monolithic behavior and load transfer across the structure. Shear key degradation can jeopardize the integrity of the structure. Transportation agencies have reported that 75% of distress in adjacent girder bridges is because of cracking and de-bonding along shear keys. Previous research has shown that locally produced UHPC has excellent mechanical and durability properties. UHPC has also been shown to have good bonding characteristics that are desirable in a potential grouting material. Bond strength between UHPC grout and substrate concrete was evaluated using slant-shear and direct tension tests. Results showed that adequate bond was achieved at 7 days. Low strengths at 28 days were observed because of low strength of the substrate concrete. Shrinkage of UHPC grout was also investigated. Shrinkage at 28 days was less than 600 µstrain which is acceptable for repair practices. Full-scale testing was used to evaluate load-deflection behavior of channel girder assemblages with grouted shear keys. Results showed that UHPC grout and non-shrink grout had similar mechanical performance. Excellent bond was achieved with all grouts, even with minimal surface preparation. The similar performances of the non-shrink grout and the UHPC grout indicates that UHPC grout does not provide a mechanical benefit over the non-shrink grout.

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