Microstructure of Concrete with Aggregates from Construction and Demolition Waste Recycling Plants

AbstractThis paper intends to analyze the microstructure of concrete with recycled aggregates (RA) from construction and demolition waste from various Portuguese recycling plants. To that effect, several scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses were performed. Various concrete mixes were evaluated in order to analyze the influence of the RA’s collection point and consequently of their composition on the mixes’ characteristics. Afterward all the mixes were subjected to the capillary water absorption test in order to quantitatively evaluate their porosity. Results from the SEM/EDS analysis were compared with those from capillary water absorption test. The SEM/EDS analysis showed that the bond capacity of aggregates to the new cement paste is greatly influenced by the RA’s nature. On the other hand, there was an increase in porosity with the incorporation of RA.

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Calcium Carbonate Bio-Deposition Technique by Using Fine Waste Mortar Particles as Bacteria-Immobilization Medium

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.633.149 ◽

2014 ◽

Vol 633 ◽

pp. 149-153 ◽

Cited By ~ 1

Author(s):

Geng Ying Li ◽

Zhong Yao Pan ◽

Yu Yu ◽

Hui Ling Kuang ◽

Fo Xiong Feng ◽

...

Keyword(s):

Calcium Carbonate ◽

Water Absorption ◽

Cement Mortar ◽

Absorption Test ◽

X Ray Diffraction ◽

Capillary Water ◽

Cement Concrete ◽

Capillary Water Absorption ◽

X Ray ◽

Water Absorption Test

A new immobilization technique that encapsulates B. pasteurii in the fine waste cement mortar particles (FWM) was being investigated to induce CaCO3 precipitation in reducing porosity and refining pore size of old cement mortar (OCM), where FWM particles were crushed from old cement concrete and passed through a size of 5 mm sieve. The capillary water absorption test (CWA) and scanning electron microscopy (SEM) were carried out to evaluate the pore-refining effect of this bio-treated methods. X-ray diffraction analysis (XRD) was used to analyze the morphology and the composition of the treated OCM. The results showed that a larger quantity of calcium carbonate bio-depositions were formed and filled the pores of OCM. As a result, the capillary water absorption was decreased by 47% compared with untreated-OCM, respectively.

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High-Performance Self-Compacting Concrete with Recycled Aggregates from the Precast Industry: Durability Assessment

Buildings ◽

10.3390/buildings10060113 ◽

2020 ◽

Vol 10 (6) ◽

pp. 113

Author(s):

Tiago Barroqueiro ◽

Pedro R. da Silva ◽

Jorge de Brito

Keyword(s):

Environmental Impact ◽

Water Absorption ◽

High Performance ◽

Construction And Demolition Waste ◽

Recycled Aggregates ◽

Absorption Test ◽

Self Compacting Concrete ◽

Quality Control Process ◽

Water Absorption Test ◽

Natural Aggregates

The main objective of this paper is to provide the industry with a simple and practical way of disposing and recovering recycled waste from precast reinforced concrete elements rejected during the quality control process, while minimizing the consumption of natural resources in the production of concrete and, consequently, significantly reducing the environmental impact of both (construction and demolition waste and extracting natural aggregates). In other words, with this work, the intention is to evaluate the feasibility of producing high-performance self-compacting concrete with a less environmental impact, by replacing natural aggregates (NA) with fine and coarse recycled aggregates resulting from the precast industry, which allows the future use of this type of aggregates in the industrial process without reservations concerning the expected durability performance. To achieve these objectives, six types of self-compacting concrete (SCC) were produced incorporating different amounts of recycled aggregates. Six replacement ratios for fine recycled aggregates (FRA) and coarse recycled aggregates (CRA) were considered: (FRA/CRA) 0/0; 25/25; 50/50; 100/100; 0/100 and 100/0%. Six different tests were carried out to characterize both the main concrete transport mechanisms and the main concrete degradation mechanisms, namely: the immersion water absorption test, capillary water absorption test, oxygen permeability test, chloride migration test, electrical resistivity test and carbonation test. The obtained results clearly demonstrate that, despite the negative influence of the inclusion of recycled aggregates, it is still possible to produce high-performance self-compacting concrete with perfectly acceptable durability properties.

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Quality Improvement of Recycled Aggregates from a Construction and Demolition Waste Recycling Pilot Plant

Materials Science Forum ◽

10.4028/www.scientific.net/msf.730-732.630 ◽

2012 ◽

Vol 730-732 ◽

pp. 630-635

Author(s):

D. Algarvio ◽

Maria Margarida Rolim Augusto Lima ◽

M.L. Cunha

Keyword(s):

Quality Improvement ◽

Magnetic Separation ◽

Pilot Plant ◽

Waste Recycling ◽

Separation Process ◽

Construction And Demolition Waste ◽

Recycled Aggregates ◽

Demolition Waste ◽

Size Fractions ◽

Cumulative Curves

The construction and demolition wastes (C&DW) frequently are abandoned in private properties, roads, and landfills or collected by non-licensed companies. In Portugal they are few recycling plants operating with this residue, and this work makes the bridge between the mechanical recycling process developed on semi-industrial scale, and the recycling products characterization process developed on laboratorial scale. The main goal of the present work is the quality improvement of the recycled aggregates produced by a construction and demolition waste recycling pilot plant with 50 ton/h located in Montemor-o-Novo. Process operations are the hammer mill comminution, magnetic separation and sieving (bar sieves: 0-4mm, 4-8mm and 8-12mm; and square sieves: 12-22mm, 22-31mm and above 31mm). In order to improve the magnetic separation process, several tests with different distances between the magnet and the conveyor belt were made (21-31cm). On the other hand, to improve the quality of the produced aggregates, the bar screen size fractions were analyzed, according to the Portuguese Standard (NP EN 933-1 2000). The most efficient distances for the magnetic separation process were identified as between 21 and 27cm, with efficiency between 85% and 90% respectively. According to the histograms, the more frequent red aggregate from 0-4mm size fraction are +0.425-0.850; +0.850-1.7 and +1.7-3.35. From the 4-8mm red aggregates, the more frequent size fractions are +4.75-6.7 and +6.7-9.95. Finally, from the 8-12mm red aggregates, the more frequent new size fractions are +6.7-9.50 and +9.50-13.20. Sieving results obtained from cumulative curves for red aggregate showed an decrease in the mass % amount for the size fractions: 0-4mm: 97%, 4-8mm:76% and 8-12mm: 56%. The results from cumulative curves for grey aggregate showed a light decreased in the amount mass % for the size fractions: 0-4mm: 90%, 4-8mm:56% and 8-12mm: 60%.

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Production of upgraded recycled aggregates from construction and demolition waste for replacement of primary sand in cement mortars

10.5194/egusphere-egu2020-5137 ◽

2020 ◽

Author(s):

Michael Galetakis ◽

Athanasia Soultana ◽

Theodoros Daskalakis

Keyword(s):

Water Absorption ◽

Cement Paste ◽

Cement Mortar ◽

Recycled Concrete ◽

Construction And Demolition Waste ◽

Recycled Aggregates ◽

Demolition Waste ◽

Cement Mortars ◽

Limestone Sand ◽

Crushed Limestone

<p>Waste concrete is the most predominant constituent material among construction and demolition waste. Recycling of this material could minimize landfilled waste and mineral resources depletion. This study investigates, in laboratory scale, the production of upgraded recycled concrete aggregates, suitable for the replacement of primary (crushed limestone sand) used in cement mortars, by means of selective crushing and autogenous grinding. These particle size reduction techniques, compared to traditional crushing/grinding, have the potential to remove the brittle cement paste from the aggregates, thus significantly improving their quality. The granulometry, the density, the water absorption (EN 13755) and the flow coefficient (EN 933-6) of the produced upgraded sand was determined and compared to crushed limestone sand. Subsequently, cement mortar specimens were manufactured using upgraded aggregates for total replacement of crushed limestone sand. Specimens were tested for their compressive and flexural strength (EN 196-1), density and water absorption. Results indicated that the upgraded recycled sand produced through the selective crushing and autogenous grinding processes had improved properties compared to the one produced by conventional crushing processes (flexural and compressive strength of cement mortar specimens were increased by 29% and 7%, respectively). However, the quality of the upgraded sand is lower than that of the primary crushed limestone. To further explore the issue, it is planned to investigate in more detail the process of autogenous grinding and to investigate the use of other selective aggregate-cement paste liberation technologies.</p>

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Caracterización físico-mecánica del hormigón estructural fabricado con áridos reciclados: comparativa experimental con sustitución de áridos finos y gruesos = Physical-mechanical characterization of the structural concrete made with recycled aggregates: experimental comparative with substitution of fine and coarse aggregates

Anales de Edificación ◽

10.20868/ade.2017.3532 ◽

2017 ◽

Vol 3 (1) ◽

pp. 24

Author(s):

Sara Valverde Fernández

Keyword(s):

Water Absorption ◽

Modulus Of Elasticity ◽

Shrinkage Strain ◽

Construction And Demolition Waste ◽

Recycled Aggregates ◽

Fine Aggregate ◽

Demolition Waste ◽

Coarse Aggregates ◽

Static Modulus ◽

Static Modulus Of Elasticity

ResumenEste trabajo estudia las propiedades mecánicas y físicas de hormigones estructurales fabricados con áridos reciclados obtenidos de residuos de construcción y demolición. Se han seleccionado mezclas con una relación específica agua / cemento y una sustitución de agregados gruesos y finos similares. Se han comparado los resultados de la deformación, la resistencia a la compresión, la resistencia a la rotura por fraccionamiento, el módulo estático de elasticidad, la deformación por contracción, la densidad aparente y los ensayos de absorción de agua. Los datos muestran que las propiedades más afectadas debido a la sustitución de agregados naturales por agregados reciclados son la trabajabilidad, el módulo de elasticidad, la deformación por contracción y la absorción de agua.AbstractThis work studies the mechanical and physical properties of structural concretes made by recycled aggregates obtained from construction and demolition waste. Mixes with a specific water/cement ratio and a similar coarse and fine aggregate substitution have been selected. Results from slump, compressive strength, splitting tensile strength, static modulus of elasticity, shrinkage strain, bulk density and water absorption tests have been compared. The data show that the most affected properties because of natural aggregate substitution for recycled aggregates are workability, modulus of elasticity, shrinkage strain and water absorption.

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CONCRETO PERMEÁVEL COM AGREGADO DA RECICLAGEM DE RESÍDUOS DA CONSTRUÇÃO E DEMOLIÇÃO: REVISÃO BIBLIOGRÁFICA / PERMEABLE CONCRETE WITH AGGREGATE FROM CONSTRUCTION AND DEMOLITION WASTE RECYCLING: LITERATURE REVIEW

Brazilian Journal of Development ◽

10.34117/bjdv6n9-684 ◽

2020 ◽

Vol 6 (9) ◽

pp. 73169-73180

Author(s):

Kelly Patrícia Torres Vieira Brasileiro ◽

Bacus de Oliveira Nahime ◽

Michell Macedo Alves ◽

Pâmela Millena Kunan ◽

Vitor Alvares ◽

...

Keyword(s):

Literature Review ◽

Waste Recycling ◽

Construction And Demolition Waste ◽

Demolition Waste

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Application of Construction and Demolition Waste in Civil Construction in the Brazilian Amazon—Case Study of the City of Rio Branco

Materials ◽

10.3390/ma14092247 ◽

2021 ◽

Vol 14 (9) ◽

pp. 2247

Author(s):

Fernando da Silva Souza ◽

José Maria Franco de Carvalho ◽

Gabriela Grotti Silveira ◽

Vitória Cordeiro Araújo ◽

Ricardo André Fiorotti Peixoto

Keyword(s):

Mechanical Strength ◽

Raw Materials ◽

Amazon Region ◽

Construction And Demolition Waste ◽

Recycled Aggregates ◽

Federal State ◽

Construction Sites ◽

Demolition Waste ◽

Conventional Concrete ◽

Initial Adhesion

The lack of usable aggregates for civil construction in Rio Branco (capital of Acre, a Federal State in the Amazon region) makes the production and use of recycled aggregates from construction and demolition waste (CDW) an alternative of great interest. In this study, a comprehensive characterization of CDW collected from 24 construction sites of six building types and three different construction phases (structures, masonry, and finishing) was carried out. The fine and coarse recycled aggregates were produced and evaluated in 10 different compositions. The aggregates’ performance was evaluated in four mixtures designed for laying and coating mortars with a total replacement of conventional aggregates and a mixture designed for a C25 concrete with 50% and 100% replacement of conventional aggregates. CDW mortars showed lower densities and greater water retention, initial adhesion, and mechanical strength than conventional mortars. CDW concretes presented lower densities and greater resistance to chloride penetration than conventional concrete, with a small mechanical strength reduction. The recycled CDW aggregates proved to be technologically feasible for safe application in mortars and concrete; for this reason, it is believed that the alternative and proposed methodology is of great interest to the Amazonian construction industry, considering the high costs of raw materials and the need for defining and consolidating a sustainable development model for the Amazon region.

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