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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-334-06

Date: 

September 30, 2019

Author(s):

Diego Jesus De Souza, Leandro Sanchez, Faraz Ahimoghadam and Gholamreza Fathifazl

Publication:

Symposium Papers

Volume:

334

Abstract:

Various studies on the use of recycled concrete aggregate (RCA) were developed in the past decades. Yet, very often direct replacement techniques are adopted to proportion RCA concrete, which leads to inferior performance of the recycled material when compared to conventional concrete. RCA is a multi-phase material comprised of original virgin aggregate and residual mortar (RM) and thus these distinct phases should be considered during the RCA mix-design process. The Equivalent Mortar Volume (EMV) mix-design method accounts for the RM to proportion RCA concrete. Although great results are normally achieved in the hardened state, EMV-designed mixtures may present important challenges in the fresh state. Modifications of the original EMV such as the modified-EMV and the Equivalent Volume method were recently proposed to tackle issues related to the fresh state and binder efficiency of recycled mixtures. This paper discusses the differences among the recent mix-design procedures developed to proportion RCA concrete.


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-334-07

Date: 

September 30, 2019

Author(s):

A.M. Said, O. Saleh and A. Ayad

Publication:

Symposium Papers

Volume:

334

Abstract:

There is a growing need for alternative binders with smaller carbon footprint. The cement manufacture is an energy intensive process that is one of the major global contributors to carbon dioxide emission. Fly ash-based geopolymer binders represent one of these potential alternatives. Beside consuming a largely produced byproduct, fly ash-based geopolymers generally have better mechanical performance when exposed to elevated temperatures. This study evaluates the effect of the initial curing temperature and the alkaline activation solution proportions on the strength, pores structure and crystal structure of fly ash-based geopolymer mortars. The geopolymer was synthesized using Class F fly ash, potassium hydroxide solution and sodium silicate solution. The specimens were made using various ratios of sodium silicate to potassium hydroxide and were initially cured at different temperatures and their properties were studied in terms of mechanical and microstructural properties.


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