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Showing 1-5 of 12 Abstracts search results

Document: 

SP314

Date: 

March 6, 2017

Publication:

Symposium Papers

Volume:

314

Abstract:

Editor: Moncef L. Nehdi

With increasing world population and urbanization, the depletion of natural resources and generation of waste materials is becoming a considerable challenge. As the number of humans has exceeded 7 billion people, there are about 1.1 billion vehicles on the road, with 1.7 billion new tires produced and over 1 billion waste tires generated each year. In the USA, it was estimated in 2011 that 10% of scrap tires was being recycled into new products, and over 50% is being used for energy recovery, while the rest is being discarded into landfills or disposed. The proportion of tires disposed worldwide into landfills was estimated at 25% of the total number of waste tires. Likewise, in 2013, Americans generated about 254 million tons of trash. They only recycled and composted about 87 million tons (34.3%) of this material. On average, Americans recycled and composted 1.51 pounds of individual waste generation of around 4.4 pounds per person per day. In 2011, glass accounted for 5.1 percent of total discarded municipal solid waste in the USA. Moreover, energy production and other sectors are generating substantial amounts of sludge, plastics and other post-consumer and industrial by-products. In the pursuit of its sustainability goals, the construction industry has a potential of beneficiating many such byproducts in applications that could, in some cases, outperform the conventional materials using virgin ingredients. This Special Publication led by the American Concrete Institute’s Committee 555 on recycling is a contribution towards greening concrete through increased use of recycled materials, such as scrap tire rubber, post-consumer glass, reclaimed asphalt pavements, incinerated sludge ash, and recycled concrete aggregate. Advancing knowledge in this area should introduce the use of recycled materials in concrete for applications never considered before, while achieving desirable performance criteria economically, without compromising the long-term behavior of concrete civil infrastructure.

Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-314

DOI:

10.14359/51689772


Document: 

SP314-01

Date: 

March 1, 2017

Author(s):

Mahmoud Reda Taha, Amr S. El-Dieb and Moncef L. Nehdi

Publication:

Symposium Papers

Volume:

314

Abstract:

The disposal of scrap tires has become an international concern. In Canada and the USA, hundreds of thousands of tires have been stockpiled with some authorities banning its landfill. The construction industry can beneficiate substantial volumes of shredded and crumb tire. This article is an overview of recycling tire rubber in concrete. It is shown that concrete with 20-30 MPa incorporating crumb and chipped tire rubber particles can be produced with a tire rubber aggregate replacement content less than 20%. Such a rubcrete can have adequate workability and air content, relatively low compressive strength, tensile strength and modulus of elasticity, high impact strength, high ductility and fracture toughness, and reasonable freeze-thaw resistance. The major concern with rubcrete is the significant loss of compressive strength and stiffness at high levels of aggregate replacement with tire rubber particles. However, surface treatments to enhance the bond of tire rubber particles to cement paste represent an efficient approach for enhancing the mechanical properties of rubcrete. Replacing coarse and/or fine aggregate with tire rubber particles results in increasing the strain capacity of concrete. Significant increase in material ductility and ability to absorb energy with increasing tire rubber particle content was reported. It is shown that rubcrete has a clear potential where flexibility and ductility are sought after, for example in tunnel linings, shock barriers, etc.

DOI:

10.14359/51689743


Document: 

SP314-02

Date: 

March 1, 2017

Author(s):

Osama Youssf, Mohamed A. ElGawady, Julie E. Mills, and Xing Ma

Publication:

Symposium Papers

Volume:

314

Abstract:

In recent years, a very important environmental issue all over the world is the disposal of waste tires. One possibility being explored is to use rubber from waste tires to replace part of the natural aggregates in conventional concrete, resulting in a product called crumb rubber concrete (CRC). Recent research on CRC is focusing on using it in structures subject to seismic loads, due to its higher ductility, damping ratio, and energy dissipation compared to conventional concrete. However CRC can have lower compressive strength (f’CRC), tensile strength (f’TRC), and modulus of elasticity (ERC) when compared with conventional concrete. This paper presents empirical models able to predict the CRC characteristics (f’CRC, f’TRC, and ERC). The proposed models are verified through the results of 148 CRC mixes as well as compared with two previous models. The proposed models resulted in predictions of the CRC characteristics with only 10.7%, 12.6%, and 11.3% errors in the predictions of f’CRC, f’TRC, and ERC, respectively. The proposed f’CRC model reduced the mean, standard deviation and maximum error percentages by 24.6%, 5.8%, and 20.2%, respectively, compared with the nearest best predictions by previous models. The proposed models can aid structural engineers who are considering CRC as an environmentally-friendly alternative to conventional concrete in structural applications.

DOI:

10.14359/51689742


Document: 

SP314-05

Date: 

March 1, 2017

Author(s):

Michael Berry, Bethany Kappes, and David Schroeder

Publication:

Symposium Papers

Volume:

314

Abstract:

This paper documents research focused on evaluating the feasibility of using minimally processed reclaimed asphalt pavement (RAP) as aggregate replacement in concrete pavements. A statistical experimental design procedure (response surface methodology – RSM) was used to investigate proportioning RAP concrete mixtures to achieve desired performance criteria. Based on the results of the RSM investigation, two concrete mixtures were selected for further evaluation: a high RAP mix with fine and coarse aggregate replacement rates (by volume) of 50 and 100 percent respectively, and a “high” strength mix with one half of the RAP used in the high RAP mix. These two concrete mixtures were subjected to a suite of mechanical and durability tests, and were used in a field demonstration project to evaluate their potential use in pavements. Mechanical properties tested were compressive and tensile strength, elastic modulus, shrinkage, and creep. Durability tests included alkali-silica reactivity, absorption, abrasion, chloride permeability, freeze-thaw resistance, and scaling. Overall, both mixes performed adequately in these mechanical and durability tests, although the inclusion of RAP negatively impacted most of the tested properties relative to those of control mixes made with 100 percent conventional aggregates.

DOI:

10.14359/51689739


Document: 

SP314-07

Date: 

March 1, 2017

Author(s):

Anto Sucic and Medhat H. Shehata,

Publication:

Symposium Papers

Volume:

314

Abstract:

Consideration of using high volume of Recycled Concrete Aggregate (RCA) in conventional concrete applications is rare due to the physical properties of RCA and its corresponding drawbacks. In the rare instance where RCA is utilized, replacement levels typically do not exceed 15-20% in order to minimize on the drawbacks. To take another approach, this paper presents results from a study aimed at maximizing the RCA replacement levels, while making only minor adjustments in mix design, to achieve both equivalent strength and durability performance of RCA concrete to their virgin aggregate counter parts. In order to investigate higher replacement levels, 15 MPa concrete criteria were followed to produce a high-volume, low-risk concrete readily produced in the ready-mix industry. Concrete specimens were tested for compressive strength, drying shrinkage, and effects of released alkalis from RCA on triggering disruptive expansion, if used with sand that marginally meets the alkali-silica expansion limit. Through modifications in mix design, the drawbacks of RCA (reduced strength, increased drying shrinkage, and promoting ASR potential) were successfully mitigated at coarse RCA replacement levels up to 100%.

DOI:

10.14359/51689737


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