Development of ductile and ultra-high performance engineered cementitious composite (ECC) with lightweight microsphere additive

Hesse, Gareth Grant (2014) Development of ductile and ultra-high performance engineered cementitious composite (ECC) with lightweight microsphere additive. [USQ Project]

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Abstract

Concrete has exceptional strength when under compression; however when exposed to tensile loading, the brittle behaviour governs its failure. Tensile strength of the concrete can be improved by the addition of randomly dispersed short fibres within the matrix. The allowable tensile loads carried by such composites however are not as high as conventionally reinforced concrete. Various forms of fibres can be used within cementitious composites, but Polyvinyl Alcohol (PVA) fibre is of particular interest in recent research due to this high tensile strength when compared to other synthetic fibres and its extremely high bond with the cementitious matrix.

An Engineered Cementitious Composite (ECC) is a ultra-high performance fibre reinforced concrete that can be produced by the inclusion of PVA fibre, in addition to other fibre types. The design of ECCs has eventuated through the process of micromechanics and although ECCs do not achieve as high a tensile strength to that of conventionally reinforced concrete, they do however behave in a similar manner as a isotropic materials, such as steel, by achieving strain-hardening. This is the characteristic that distinguishes ECCs from other fibre reinforced concretes. However, in order to achieve strain-hardening, there is a requirement for surface coating the PVA fibre with a oil substance in order to slightly reduce the bond of the fibre/matrix interface.

This research investigates the development of a new lightweight ECC that includes hollow glass microspheres as a lightweight additive with the inclusion of uncoated PVA fibre. The addition of microspheres is expected to reduce the bond of fibre/matrix interface in a similar fashion as typical PVA fibre surface coating. Two types of microspheres (Potters Industries Pty. Ltd. Sphericel 110P8 & Potters Industries Pty. Ltd. Q-Cel 5070S) at 10%, 15% & 20% fraction volume were included within the PVA-ECC. Lightweight ECC mix designs with randomly dispersed uncoated PVA fibre and varying hollow glass microspheres were created and test specimens were prepared. The specimens were exposed to compression, flexure and impact testing whereby the results were analysed and compared to the properties of a standard PVA-ECC in order to assess if there was a reduction in density, an increase or maintained compressive strength, changes in flexural properties, impact strength and whether strain-hardening was achieved.

The outcomes suggest that the density is reduced with the inclusion of microspheres, more so with the Q-Cel than the Sphericel. The compressive strength has minor reductions with the Sphericel microsphere addition and may be considered negligible. The Q-Cel however resulted in higher reductions of compressive strength. Flexural strength and strain of the composites with uncoated PVA fibre and microsphere additions performed similar to that of plain concrete, with only minor increases in flexural strength and strain. The addition of microspheres is therefore considered not have the same effect on the fibre bond strength as typical surface coating would. The impact testing suggested that PVA fibre improves the impact strength at low strain rates, however at medium to high strain rates there seems to be no greater increase in strength compared to the plain concrete. The inclusion of microspheres to the PVA-ECC adversely affects the impact strength of the low strain rates to match that of plain concrete. Again, no noticeable change is witnessed to the PVA-ECC at medium to high strain rates with the inclusion of microspheres.


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Item Type: USQ Project
Item Status: Live Archive
Additional Information: Bachelor of Engineering Honours (Civil) project.
Faculty / Department / School: Current - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying
Supervisors: Zhuge, Yan
Date Deposited: 09 Sep 2015 05:21
Last Modified: 08 Mar 2016 02:08
Uncontrolled Keywords: concrete; tensile strength; polyvinyl-alcohol fibres; PVA fibres; ECC; engineered cementitious composite; glass microsphere
Fields of Research : 09 Engineering > 0905 Civil Engineering > 090503 Construction Materials
09 Engineering > 0905 Civil Engineering > 090599 Civil Engineering not elsewhere classified
URI: http://eprints.usq.edu.au/id/eprint/27085

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