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International Concrete Abstracts Portal

Showing 1-5 of 14 Abstracts search results

Document: 

SP334

Date: 

October 9, 2019

Author(s):

Moncef L. Nehdi

Publication:

Symposium Papers

Volume:

334

Abstract:

To improve the eco-efficiency and sustainability of concrete, the cement and concrete industry can exploit many byproducts in applications that could, in some cases, outperform conventional materials made with traditional ingredients. This Special Publication of the American Concrete Institute Committee 555 (Concrete with Recycled Materials) is a contribution towards improving the sustainability of concrete via using recycled materials, such as scrap tire rubber and tire steel wire fiber, GFRP waste, fluff, reclaimed asphalt pavements, recycled latex paint, 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 quality and long-term performance of the concrete civil infrastructure.


Document: 

SP-334-13

Date: 

September 30, 2019

Author(s):

Luz Angélica Rodríguez-Bello, Pedro Nel Quiroga, Juan Pablo Agudelo, and María Paulina Villegas-De-Brigard

Publication:

Symposium Papers

Volume:

334

Abstract:

Construction and demolition waste (CDW) has become an environmental, social and economic problem in some regions. Many initiatives to increase CDW recycling and concrete with recycled aggregates have failed or have not accomplished the goals, due to the lack of good management. In Bogotá, even though regulations establish that 25% must be harnessed, only 17% is achieved. To obtain rates as high as the global ones, a CDW diagnosis in works is run and policy instruments that would allow the application of a circular economy concept as opposed to a linear economy are determined. It is found that economic and informative instruments are the most popular worldwide and the most requested at the national level, in comparison to regulatory instruments which currently prevail in Bogotá. Likewise, the literature highlights prevention actions and the national context prefers recycling and disposition actions.


Document: 

SP-334-10

Date: 

September 30, 2019

Author(s):

Ahmed A. Gheni and Mohamed A. ElGawady

Publication:

Symposium Papers

Volume:

334

Abstract:

Statistics show an increase in the use of fly ash in concrete to improve both sustainability and performance. However, concrete incorporating high volume fly ash has encountered an issue with incompatibility between fly ash and air entraining admixture (AEA). This study investigates using ground recycled rubber (GRR) as an eco-friendly alternative to AEA to improve the freeze-thaw performance of mortar mixtures incorporating two different types and ratios of fly ash. Two different sizes and ratios of GRR were used in this study. The results were compared with mixtures having two different types and dosages of AEA as well as a reference mortar mixture having neither GRR nor AEA. Foam indices were determined for both types of fly ash and compared with cement. The compressive strength retention values of mortar cubes after exposing them to 36 freeze-thaw cycles were determined and linked to the air content of each mixture. This study revealed that the GRR outperformed the AEA in terms of the freeze-thaw durability where all mixtures retained their compressive strengths. However, the performance of mixtures including AEA was inconsistent depending on the chemical composition of the fly ash, fly ash replacement ratio, and AEA dosage.


Document: 

SP-334-11

Date: 

September 30, 2019

Author(s):

Eslam Y. Gomaa, Ahmed A. Gheni, and Mohamed A. ElGawady

Publication:

Symposium Papers

Volume:

334

Abstract:

The durability of alkali activated concrete (AAC) synthesized using high calcium fly ashes (FAs) was studied. Surface resistivity, bulk electrical resistivity, rapid chloride ions penetration, and freeze-thaw resistance tests were carried out on AAC made with five different FAs. The specimens were either oven-or moist-cured. The effect of adding air entraining admixture (AEA) and recycled crumb rubber to the AAC specimens on the freeze-thaw resistance was investigated as well. It was found that the durability of AAC was higher than that of comparable ordinary Portland cement (OPC) concrete. Adding the AEA improved the freeze-thaw resistance but not enough to complete the 300 cycles, per ASTM C666-15. Adding the rubber to the AAC mixtures improved the freeze-thaw resistance significantly.


Document: 

SP-334-02

Date: 

September 30, 2019

Author(s):

Anol Mukhopadhyay and Xijun Shi

Publication:

Symposium Papers

Volume:

334

Abstract:

Potential issues associated with depletion of good aggregate sources and management of excess RAP stockpiles increasingly motivate use of RAP in PCC as a coarse aggregate replacement. Texas has shown great interest in disposing excess RAP stockpiles and a systematic study on using RAP in PCC for Texas pavement applications was conducted by the authors recently. This paper provides a concise summary of the findings from this study. The major conclusions are (1) PCC mixture with dense aggregate gradation can be achieved by adding coarse RAP with adequate intermediate sized particles, which offers better overall performance in terms of workability and mechanical properties, (2) RAP-PCC with coarse RAP replacement up to 40% showed considerable reduction for modulus of rupture. Asphalt cohesive failure (crack passing through the asphalt layer) was found to be the main mechanism responsible for the strength reductions, (3) the addition of allowable amounts of RAP into PCC provides equivalent durability performance relative to plain PCC, and (4) constructing pavements with RAP-PCC yields economic, environmental and social benefits.


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