scholarly journals Preliminary Study of Recycled Aggregate Mortar for Electric Arc Furnace Dust Encapsulation

2021 ◽  
Vol 11 (20) ◽  
pp. 9525
Author(s):  
Enrique F. Ledesma ◽  
Angélica Lozano-Lunar ◽  
Ruan L. S. Ferreira ◽  
José María Fernández-Rodríguez ◽  
José Ramón Jiménez
Keyword(s):  
Fine Fraction ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Natural Aggregate ◽  
Before And After ◽  
Preliminary Study ◽  
Natural Aggregates ◽  
Mechanical Strengths

This article shows the preliminary results of a study carried out to determine the technical feasibility of encapsulating a high percentage of EAFD in cement-based mortars manufactured with the fine fraction of recycled concrete aggregates (RCA). Two families of mortars, with natural aggregate as a reference and with RCA, were studied. An incorporation rate by weight of two parts mortar to one part EAFD was tested. The mechanical strengths (compressive strength and tensile strength) before and after immersion in water, the rate of delitescence and the leaching behavior were studied. Mortars made with RCA showed similar mechanical strengths to the reference mortars made with natural aggregates; however, the incorporation of EAFD decreased the mechanical strengths. Encapsulation considerably reduced the leaching of heavy metals, although the Pb concentration remained above the hazardous waste limit. With this preliminary study, two wastes are managed together, and the results have shown that the use of RCA instead of natural aggregate is a viable alternative since it does not significantly impair the mechanical or leaching properties of the cement-based matrices used to encapsulate EAFD.

Durable Performance of Recycled Concrete Using Coarse and Fine Recycled Concrete Aggregates in Air Environment

2011 ◽  
Vol 261-263 ◽  
pp. 446-449 ◽  
Author(s):  
Ping Hua Zhu ◽  
Xin Jie Wang ◽  
Jin Cai Feng
Keyword(s):  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Structural Concrete ◽  
Aggregate Concrete ◽  
Cube Strength ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Natural Aggregate ◽  
Concrete Mixtures

The influence of synchronous use of coarse and fine recycled concrete aggregates on durable performance of recycled aggregate concrete (RAC) in air environment were determined. In this study, three series of concrete mixtures were prepared, in which the coarse recycled aggregate was used as 0%, 30%, 60% and 90% replacements of coarse natural aggregate and fine recycled aggregate as 0%, 10%, 20%, and 30% replacements of fine natural aggregate. Meanwhile, fly ash and slag were used as 15%, 25%, 35% and 45% replacements of cement, respectively. The carbonation depths, compressive cube strength, workability of RACs were tested. The experimental results showed that RAC with synchronous use of coarse and fine recycled concrete aggregates had satisfactory durable performance. When RAC was used as structural concrete in air environment, the optimum synchronous replacements are 60% for coarse recycled aggregate and 20% for fine recycled aggregate.

scholarly journals Mechanical Behavior of Hot-Mix Asphalt Made with Recycled Concrete Aggregates from Construction and Demolition Waste: A Design of Experiments Approach

2019 ◽  
Vol 11 (13) ◽  
pp. 3730 ◽  
Author(s):  
Juan J. Galan ◽  
Luís M. Silva ◽  
Ignacio Pérez ◽  
Ana R. Pasandín
Keyword(s):  
Hot Mix Asphalt ◽  
Water Saturation ◽  
Recycled Concrete ◽  
Construction And Demolition Waste ◽  
Demolition Waste ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Natural Aggregate ◽  
Indirect Tensile ◽  
Natural Aggregates

The present work is a re-evaluation of previous research on the durability of hot-mix asphalt made with recycled concrete aggregates from construction and demolition waste (CDW) with a different approach. Response surface methodology (RSM) was used to conduct this study. The kind of natural aggregates (schist and calcite-dolomite), the recycled concrete aggregates percentage (0%, 20%, 40% and 60%) and the water saturation (0% and 100%) were the pertinent factors for this methodology. Indirect tensile stress (ITS) was determined in mixtures fabricated with 0%, 20%, 40% and 60% recycled concrete aggregates. According to the results, the ITS of the bituminous mixtures increases as the percentage of recycled concrete aggregate increases. This behavior is more significant when calcite-dolomite is used as a natural aggregate. Water saturation has the same influence in both natural aggregates. The indirect tensile strength ratio (ITSR) was calculated to evaluate the stripping potential. According to the Spanish specifications, the results suggest that the percentage of CDW that can be used for hot mixes is 17% when schist is used as natural aggregate and 14% for calcite-dolomite.

scholarly journals Effect of Recycled Concrete Aggregates on Compressive Strength and Water Permeability of Concrete

2020 ◽  
Vol 14 ◽  
Keyword(s):  
Compressive Strength ◽  
Negative Impact ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Aggregate Concrete ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Coarse Aggregates ◽  
Natural Aggregates

This paper discusses the effects of recycled concrete aggregates (RCA) on compressive strength and permeability of recycled aggregate concrete (RAC) by using recycled concrete aggregates as a replacement of natural coarse aggregates (NCA). Four replacement percentages were used to study the effect of replacement. Replacement percentages used were 30%, 50%, 70% and 100% with 0% replacement was used as control. Mix design of 1:1.24:2.6 was used in the study with water to cement ratio of 0.43. Influence of RCA on compressive strength was determined for all the mixes as per ASTM C39 standard. The permeability of all the mixes was determined by measuring absorption, sorptivity and Darcy’s coefficient. Results of compressive strength indicated that concrete with 30% replacement of NCA can be successfully used in structural concrete without compromising too much on strength. Whereas, the replacement of natural aggregates with RCA has a negative impact on the permeability of concrete at all replacement levels. Absorption, sorptivity and permeability of natural aggregate concrete is lower as compared to RAC with 30% replacement showing the better performance as compared to other replacement ratios.

scholarly journals Characterisation and Life Cycle Assessment of Pervious Concrete with Recycled Concrete Aggregates

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 209
Author(s):  
Adilson C. Paula Junior ◽  
Cláudia Jacinto ◽  
Thaís M. Oliveira ◽  
Antonio E. Polisseni ◽  
Fabio M. Brum ◽  
...  
Keyword(s):  
Environmental Performance ◽  
Treatment Plant ◽  
Recycled Concrete ◽  
Pervious Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Positive Contribution ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates

The search for environmental preservation and conservation of natural resources gives rise to new concepts and viable technical solutions on the path to sustainable development. In this context, this study’s main objective is to analyse the influence of recycled concrete aggregates (RCAs) on the development of pervious concrete, whose use as a floor covering represents an excellent device to mitigate the urban soil sealing phenomena. For this, mechanical and hydraulic tests were carried out, in addition to microstructural analyses and the assessment of its environmental performance. The results obtained were compared to reference studies also involving the incorporation of recycled aggregates. A pilot-scale case study was conducted, involving a parking space lined with pervious concrete moulded “in situ”. In laboratory tests, permeability coefficients and mechanical strengths compatible with the literature and above the normative limit for light traffic were found. The case study demonstrated higher permeability than in the laboratory, but the flexural strength was lower, being indicated only for pedestrian traffic. The environmental assessment showed that the RCA represents a positive contribution to the environmental performance of pervious concrete. Still, attention should be given to the recycled aggregate transport distance between the concrete plant and the RCA treatment plant.

scholarly journals Strength and Water Absorption of Sustainable Concrete Produced with Recycled Basaltic Concrete Aggregates and Powder

2021 ◽  
Vol 13 (11) ◽  
pp. 6277
Author(s):  
Ibrahim Sharaky ◽  
Usama Issa ◽  
Mamdooh Alwetaishi ◽  
Ahmed Abdelhafiz ◽  
Amal Shamseldin ◽  
...  
Keyword(s):  
Water Absorption ◽  
Edge Length ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Partial Substitution ◽  
Small Reduction ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Sustainable Concrete

In this study, the recycled concrete aggregates and powder (RCA and RCP) prepared from basaltic concrete waste were used to replace the natural aggregate (NA) and cement, respectively. The NA (coarse and fine) was replaced by the recycled aggregates with five percentages (0%, 20%, 40%, 60% and 80%). Consequently, the cement was replaced by the RCP with four percentages (0%, 5%, 10% and 20%). Cubes with 100 mm edge length were prepared for all tests. The compressive and tensile strengths (fcu and ftu) and water absorption (WA) were investigated for all mixes at different ages. Partial substitution of NA with recycled aggregate reduced the compressive strength with different percentages depending on the type and source of recycled aggregate. After 28 days, the maximum reduction in fcu value was 9.8% and 9.4% for mixtures with coarse RCA and fine RCA (FRCA), respectively. After 56 days, the mixes with 40% FRCA reached almost the same fcu value as the control mix (M0, 99.5%). Consequently, the compressive strengths of the mixes with 10% RCA at 28 and 56 days were 99.3 and 95.2%, respectively, compared to those of M0. The mixes integrated FRCA and RCP showed higher tensile strengths than the M0 at 56 d with a very small reduction at 28 d (max = 3.4%). Moreover, the fcu and ftu values increased for the late test ages, while the WA decreased.

Review of Studies concerning Effects of Unbound Crushed Concrete Bases on PCC Pavement Drainage

1996 ◽  
Vol 1519 (1) ◽  
pp. 51-58 ◽  
Author(s):  
Mark B. Snyder ◽  
James E. Bruinsma
Keyword(s):  
Drainage System ◽  
Field Studies ◽  
Recycled Concrete ◽  
Concrete Aggregate ◽  
Drainage Systems ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Crushed Concrete ◽  
Pavement Structures ◽  
Natural Aggregates

Recycled concrete aggregate (RCA) products are sometimes used as replacements for virgin aggregate products in concrete pavement structures. Recent concerns have centered on the deposit of RCA-associated fines and precipitate suspected of reducing the drainage capacity of RCA base layers and associated drainage systems. Environmental concerns have focused on the relatively high pH of the effluent produced by untreated RCA base layers. Several studies have examined these concerns and others; the results of some of these studies have not been published or publicized. The most relevant of these studies are summarized herein. These research efforts demonstrate that calcium-based compounds are present in most recycled concrete aggregates in quantities sufficient to be leached and precipitated in the presence of carbon dioxide. Precipitate potential appears to be related to the amount of freshly exposed cement paste surface. Thus, selective grading or blending with natural aggregates can reduce, but not eliminate, precipitate problems. It was also noted that insoluble, noncarbonate residue makes up a major portion of the materials found in and around pavement drainage systems. Washing the RCA products before using them in foundation layers appears to reduce the potential for accumulation of dust and other fines in the drainage system, but probably has little effect on precipitate potential. Field studies have shown that precipitate and insoluble materials can significantly reduce the permittivity of typical drainage fabrics but that attention to drainage design details can minimize the effects of these materials on pavement drainage.

Structural Concrete with Recycled Aggregate: Advances in Mechanical Properties, Durability and Sustainability

2016 ◽  
Vol 847 ◽  
pp. 553-558 ◽  
Author(s):  
Marc Antonio Liotta ◽  
Marco Viviani ◽  
Carlotta Rodriquez
Keyword(s):  
Cement Mortar ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Mix Design ◽  
Elastic Behavior ◽  
Structural Concrete ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Ordinary Concrete

A large number of tests has been carried out in the last 15 years all around the world to study the possibility to use recycled concrete aggregates (RCA) to produce structural concrete.Earlier tests indicated that RCA concrete had lower properties in comparison to ordinary concrete, such as lower elastic modulus, a more brittle post-elastic behavior, lower workability, higher shrinkage and creep.Most of these issues have been addressed to the content of cement mortar remaining in adhesion to the aggregate after the recycling processes and that cannot be totally eliminated without high economic and ecological costs. This cement mortar which has undergone the crushing process creates zones of weakness in the RCA, causes higher water absorption, higher concrete porosity and causes the decay of the aforementioned properties.More recent tests prove that Recycled Concrete shows this peculiar problems only with a percentage of substitution of standard aggregates with RCA higher than 30%. Under this percentage recycled aggregate concrete (RAC) can be considered as a standard concrete, on condition that an appropriate mix design is performed.

scholarly journals Modulus and Strength of Concretes with Alternative Materials

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4378
Author(s):  
Ana Elisabete Paganelli Guimarães de Avila Jacintho ◽  
Ivanny Soares Gomes Cavaliere ◽  
Lia Lorena Pimentel ◽  
Nádia Cazarim Silva Forti
Keyword(s):  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Concrete Aggregates ◽  
Recycled Concrete Aggregates ◽  
Model Code ◽  
Alternative Materials ◽  
Model Code 2010 ◽  
The Difference ◽  
Natural Aggregates ◽  
Predicted Values

This paper presents a study with concretes produced with natural aggregates, recycled concrete aggregates (RCA) and waste porcelain aggregates (WPA). The study analyzed the influence of recycled aggregates in the mechanical properties of conventional concretes and evaluated the difference between measured and predicted values of elasticity modulus. The incorporation of WPA in concrete showed better mechanical results compared to the concretes produced with RCA. Measured elasticity moduli were lower than moduli predicted by NBR 6118:2014 and fib Model Code 2010, while measured results were greater than values predicted by Eurocode 2:2004 and ACI 318:2014, as expected, which indicated the safety of the latter two standards.

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