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Evaluation of ASTM C 494 Procedures for Polycarboxylate Admixtures used in Precast Concrete Elements

Microcracking focused on the top of flange at a TxDOT producer precast plant

What Was the Need?

"Over the past few decades surface cracking has become more and more apparent on girders produced at precast plants all throughout Texas. The cracking became a cause for concern when TxDOT’s quality control noticed that the map cracking would develop even prior to girder installation, occurring in the precast yard. These micro-cracks represent a loss in resources (time, money, labor, materials) for the precast producers and TxDOT since the micro-cracks have resulted in the rejection of several girders... TxDOT was prompted to consider whether the high range water reducers (HRWRs), specifically the polycarboxylate admixtures, could be contributing to the cracking issue."

What's the Solution?

"[This research found that] Polycarboxylate HRWRs are unlikely to be the source of the cracking. More likely “culprits” include ambient humidity and the extremely low w/cm ratio. One recommendation is that precast plants lower their cementitious content, to the lowest extent possible without compromising strength. This could be accomplished by optimization of aggregate gradation since this enables a paste content reduction and thus mitigates volumetric changes in the concrete. Evaluating the impact of fly ash and other supplementary cementitious mixtures on micro-cracking behavior in low cementitious content precast concrete mixtures should be investigated. Also recommended is using the highest w/cm ratio that provides adequate durability and strength, as well as re-evaluating concreting procedures to mitigate surface self-desiccation (e.g., better curing) and shrinkage (e.g., chemical shrinkage)." --Project Summary Report

Project Number

0-6813

Status

Completed

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Project Details

Start Date

8/15/2014

Renewal date

12/31/2015

End Date

12/31/2016

Performing Institution(s)

Center for Transportation Research (CTR)

Research Team

RS: Raissa Ferron

Sponsor

Project Manager

Sonya Badgley

Contract Specialist

Annette Trevino

Amount Funded

FY14: $11,961
FY15: $120,333
FY16: $106,696
FY17: $27,452

Publications from this Project

Page:

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Functional Area

Construction and Maintenance

Index Terms

Admixtures
Polycarbonates
Water reducing agents
Precast concrete
Self compacting concrete
Specifications

Lead University

CTR

Researcher

Ferron, Raissa Patricia Douglas

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Comments

nugentml

Related content:

2018 web presentation (March 6, 2018): "Release Strengths: Prestressed Girder Deterioration" / Jason Tucker, P.E. http://ftp.dot.state.tx.us/pub/txdot-info/brg/webinars/2018-0306/tucker.pdf

4/24/2020 at 4:58 PM

Helpful?

Record Added:

11/26/2013

Record Updated:

1/25/2022 5:31 AM EST

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