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International Concrete Abstracts Portal

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


Document: 

SP314-04

Date: 

March 1, 2017

Author(s):

Colter Roskos, Michael Berry, and Jerry Stephens

Publication:

Symposium Papers

Volume:

314

Abstract:

Concrete is the world’s most used construction material, and although it offers many advantages over other building materials from an environmental perspective (e.g., durability, thermal properties), the negative environmental impact of traditional concrete is of growing concern as its use increases. This paper highlights significant findings from a recent study focused on identifying alternate materials to be used in concrete to mitigate its negative environmental impacts. This study specifically researched structural-grade concrete in which 100 percent of the portland cement was replaced with self-cementitous hydraulic fly ash and the aggregates were replaced with pulverized post-consumer glass from the container industry. In particular, this paper presents the results of mechanical (compressive and tensile strength, elastic modulus), and durability (ASR, absorption, abrasion, chloride permeability) tests performed on two such concretes made with fly ashes from power plants in Wyoming and Kansas. Overall, the fly ash/glass concretes tested in this research program showed promise for use in the construction industry. They exhibited 28-day unconfined compression strengths in excess of 4,000 psi (28 MPa); although their corresponding tensile strengths were somewhat lower than would be expected based on the behavior of conventional concretes. Relative to durability, the results of the ASR tests were mixed, depending on the manner in which the ASR testing was conducted. The absorption results and abrasion resistance of the two concretes were found to be similar to conventional concretes, and the permeability test results indicate a total charge passed of less than 1,000 coulombs, which correlates with “very low” likelihood of chloride ion penetration being an issue.


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.


Document: 

SP314-09

Date: 

March 1, 2017

Author(s):

Ardavan Yazdanbakhsh, Lawrence C. Bank, and Jonathan Rosen

Publication:

Symposium Papers

Volume:

314

Abstract:

In the past, many investigations have studied the effect of replacing coarse natural aggregate (CNA) with coarse recycled concrete aggregates (CRCA) on “material” properties of concrete, particularly compressive strength. This article reports on a research program in which (1) commonly used and practical methods were used for mixture design, proportioning, and production of CRCA and CNA concrete batches, (2) reinforced concrete beam specimens were produced from both types of concrete and tested in a bending configuration for measuring load-deflection response, moment capacity, and failure mode, and (3) a theoretical investigation was performed to predict the effect of concrete strength on the moment capacity of the beams. The test results showed, as predicted by the theoretical study, that the reduction in moment capacity caused by the strength loss due to the replacement of natural aggregate with CRCA, was negligible. It was also observed that the scatter of load carrying capacities of CRCA and CNA concretes were both very low and had coefficient of variation values of 0.048 and 0.064 respectively.


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.


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