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Guidelines for the Use of Waste Concrete Fines

Dufalla, Nicole (2015) Guidelines for the Use of Waste Concrete Fines. Master's Thesis, University of Pittsburgh. (Unpublished)

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The production and maintenance of Portland cement concrete pavements creates a considerable amount of waste water, usually with a high pH and high levels of dissolved and suspended solids and the safe disposal of this material can be costly. The ability to reuse this waste water as mixing water into new concrete production would be a more cost efficient option, which would greatly reduce waste. Due to the presence of existing cement particles and elevated pH, waste water with both hydrated and unhydrated cement particles used as mixing water affects the performance of the concrete. These effects can potentially be beneficial, even if the water has a percent solids higher than recommended in current mix water specifications. Therefore, a method of quantifying the characteristics of the waste water is necessary to predict the performance of the concrete based on measurable properties of the waste water. This study quantifies the characteristics of the waste water, including pH, conductivity, and index of refraction. Models are then developed using a regression analysis. This is accomplished by characterizing waste water produced using multiple different sources of both grinding and wash out fines. Then, mortar properties are tested from mortar batches made with the characterized waste water, including compressive strength and set time. The laboratory data is then used for the development of regression equations for predicting the performance (set time and compressive strength) of the concrete, as a function of the waste water characteristics that are easily measured using in-line sensors. These relationships makes it possible to use waste water from a variety of sources in the production of new concrete while, being able to predict the effects of the inclusion of the waste water on the concrete performance a priori. Finally, a mock set up of a plant water circulation system was constructed using in-line sensors for measuring the waste water properties. Concrete is then cast using water pulled from the lab-scale water circulation system to provide insight into the adequacy of the final models.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Thesis AdvisorVandenbossche, Julie M.jmv7@pitt.eduJMV7
Committee MemberJanssen,
Committee MemberVidic, Natasa S.nav9@pitt.eduNAV9
Date: 4 June 2015
Date Type: Publication
Defense Date: 10 September 2014
Approval Date: 4 June 2015
Submission Date: 23 March 2015
Access Restriction: 5 year -- Restrict access to University of Pittsburgh for a period of 5 years.
Number of Pages: 141
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Civil and Environmental Engineering
Degree: MS - Master of Science
Thesis Type: Master's Thesis
Refereed: Yes
Uncontrolled Keywords: concrete, recycling, waste water, compression strength, set time testing, sustainability
Date Deposited: 04 Jun 2015 14:02
Last Modified: 04 Jun 2020 05:15


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