Alkali-silica reaction in concrete bridge piles: strengthening with fibre-reinforced polymers

Knight, Tracey Anne (2014) Alkali-silica reaction in concrete bridge piles: strengthening with fibre-reinforced polymers. [USQ Project]

[img]
Preview
Text
KNIGHT_2014 .pdf

Download (147Mb) | Preview

Abstract

Unexpected and premature degradation of concrete bridge structures due to alkali-silica reactivity (ASR) is a significant problem facing most, if not all, road and infrastructure authorities around the world. Alkali-silica reaction occurs between the highly alkaline cement paste and reactive non-crystalline silica in concrete aggregates; the resulting byproduct is an expansive gel. Deleterious ASR expansion can inflict serious damage and expose the structure to further forms of structural damage. This research focused on assessing the extent of degradation caused by deleterious ASR and the use of fibrereinforced
polymers to reinstate compressive strength in ASR damaged concrete bridge piles.

The Queensland Department of Transport and Main Roads (TMR) has an extensive use for concrete infrastructure. However, an asset survey conducted in 2000 indicated that approximately 105 Queensland bridges were known to be suffering from the effects of ASR (Carse, 2000). A number of studies around the world have shown that physical
restraint or containment significantly reduces deleterious ASR expansion. As such, fibre-reinforced polymers are a strong, lightweight material that can be manipulated to
encase ASR affected structures with the potential to restore structural integrity.

During this research, a baseline development of compressive strength loss due to deleterious ASR has been investigated and retrofitting techniques have been explored.
ASR damage was successfully replicated in laboratory concrete samples using the ASTM C1260 test procedure; the resulting map cracking was classified as severe and
significant.

The investigation concluded that if the specimen was completely engrossed by map cracking it is possible to expect up to a 50% reduction in compressive strength.
Furthermore, a 37.5% reduction in the modulus of elasticity was observed in samples showing minor signs of ASR distress, and it may be possible that the modulus of
elasticity could be further reduced in more severely affected samples.

Carbon fibre-reinforced polymers are a promising material for retrofitting ASR damaged structures. The key to the successful use of FRPs is that the fibre wrap is not
engaged in strengthening until the concrete begins to dilate and fail. This is when the FRP produces a confining pressure and strengthens the concrete structure. With further ASR expansion in the transverse direction, even if the ASR itself is left untreated, it is possible that the structural strength could be reinstated and maintained for a significant period of time. During testing of the CFRP wrapped concrete cylinders, compressive strengths of almost three times the design strength and six times the ASR deteriorated strength, were achieved. Whilst these results were achieved with very high proportions of FRP to the column size, it is estimated that with approximately 2.25% increase in a pile’s diameter, by the application of a lapped hoop CFRP wrap, restoration of the original compressive strength could be achieved.

There are many possibilities to extend and improve on this work. A significant amount of time has been invested in developing the laboratory techniques for ASR replication.
The resources required for continued testing have been identified, such that samples could be moulded and the ASR replication process could commence again immediately.
Therefore, an improved test schedule could be developed, with a longer test window, giving a more detailed review of categorical periodization of crack development and the
strength reduction relationship. It is recommended that further research be carried out to extend the scope of investigation to complimentary techniques of alkali-silica reaction treatment with FRP strengthening, and testing of larger scale reinforced and unreinforced concrete models.


Statistics for USQ ePrint 27241
Statistics for this ePrint Item
Item Type: USQ Project
Item Status: Live Archive
Additional Information: Bachelor of Engineering (Civil) project.
Faculty / Department / School: Current - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying
Supervisors: Zhuge, Yan; Roberts, Wayne
Date Deposited: 09 Sep 2015 04:56
Last Modified: 04 Mar 2016 05:30
Uncontrolled Keywords: alkali-silica reaction, concrete, fibre-reinforced polymers
Fields of Research : 09 Engineering > 0905 Civil Engineering > 090503 Construction Materials
URI: http://eprints.usq.edu.au/id/eprint/27241

Actions (login required)

View Item Archive Repository Staff Only