Appraisal of Processing Techniques for Recycled Aggregates in Concrete

Due to depletion of natural aggregates the need for the usage of recycled aggregate in concrete has gained significance. In this regard, the present study is an attempt to evaluate the performance of M20 grade of concrete made with 100% recycled aggregate processed using various techniques. Handpicked aggregate from concrete rubble is used to prepare recycled aggregate concrete. The use of chemical admixture is mandatory to compensate the extra water (3 to 6%) required by the RCA (Recycled Aggregates). RCA treated with calcite mineral precipitating bacterial suspension enhances its surface permeability. RCA exposed to different acid concentrations improved the surface of the aggregate with the removal of the loosely adhered mortar. In thermal – mechanical method the recycled aggregates from rubble are heated in microwave to 300°C to remove adhered mortar from the aggregate and placed in a rotating drum containing iron balls. In chemical– mechanical method the recycled aggregate is exposed to Na2So4 and is subjected to freeze-thaw cycles to create mechanical to separate adhered mortar from RCA. In acid soaking beneficiation method the mortar around RCA is removed by immersing them in 5% HCl and H2SO4 for 24 hours. All the above mentioned recycled aggregate processing techniques are however to be tested in full scale to study the efficiency of these treatment techniques. Compressive strength and water absorption capacities of various concrete samples made with recycled aggregate prepared using above discussed processing techniques are evaluated.

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A Review on Alkali-Silica Reaction Evolution in Recycled Aggregate Concrete

Materials ◽

10.3390/ma13112625 ◽

2020 ◽

Vol 13 (11) ◽

pp. 2625 ◽

Cited By ~ 3

Author(s):

Miguel Barreto Santos ◽

Jorge De Brito ◽

António Santos Silva

Keyword(s):

Recycled Aggregate Concrete ◽

Recycled Aggregate ◽

Recycled Aggregates ◽

Mitigation Measures ◽

Alkali Silica Reaction ◽

Aggregate Concrete ◽

Reactive Silica ◽

Natural Aggregates ◽

Exposure Conditions ◽

Lack Of Knowledge

Alkali-silica reaction (ASR) is one of the major degradation causes of concrete. This highly deleterious reaction has aroused the attention of researchers, in order to develop methodologies for its prevention and mitigation, but despite the efforts made, there is still no efficient cure to control its expansive consequences. The incorporation of recycled aggregates in concrete raises several ASR issues, mainly due to the difficult control of the source concrete reactivity level and the lack of knowledge on ASR’s evolution in new recycled aggregate concrete. This paper reviews several research works on ASR in concrete with recycled aggregates, and the main findings are presented in order to contribute to the knowledge and discussion of ASR in recycled aggregate concrete. It has been observed that age, exposure conditions, crushing and the heterogeneity source can influence the alkalis and reactive silica contents in the recycled aggregates. The use of low contents of highly reactive recycled aggregates as a replacement for natural aggregates can be done without an increase in expansion of concrete. ASR expansion tests and ASR mitigation measures need to be further researched to incorporate a higher content of recycled aggregates.

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Effect of Recycled Aggregates on the Energy Dissipation Capacity of RC Beam subjected to Reverse Cyclic Flexural Loading

Mehran University Research Journal of Engineering and Technology ◽

10.22581/muet1982.2101.13 ◽

2021 ◽

Vol 40 (1) ◽

pp. 140-151

Author(s):

Muhammad Rizwan Riaz ◽

Rashid Hameed ◽

Usman Akmal ◽

Asad Ali Gillani ◽

Muhammad Ilyas

Keyword(s):

Energy Dissipation ◽

Recycled Aggregate Concrete ◽

Recycled Aggregate ◽

Recycled Aggregates ◽

Rc Beam ◽

Rc Beams ◽

Aggregate Concrete ◽

Flexural Loading ◽

Energy Dissipation Capacity ◽

Natural Aggregates

The energy dissipation capacity of concrete is an important aspect for a Reinforced Concrete (RC) structure to be seismically resistant. Various types of concrete incorporating sustainable materials are being developed these days such as recycled aggregate concrete. Determination of energy dissipation capacity of such new types of concrete is of great importance for their application in RC structures which are to be constructed in seismically active areas. In this regard, the experimental study presented in this contribution investigated the energy dissipation capacity of RC beams constructed using recycled aggregate concrete and subjected to three different deflection amplitude levels of reverse cyclic flexural loading. For this purpose, a total of 20 RC beams of cross section 75 x 150 mm and length of 1350 mm were cast using five different concrete compositions and tested. Among five different concrete compositions, one was control concrete containing 100% natural aggregates while the remaining four compositions were of recycled aggregate concrete containing natural and recycled aggregates. Four replacement levels (25%, 50%, 75%, and 100%) of natural aggregates with recycled aggregates were examined. Results indicated that the amplitude level of imposed deflection is an important factor which influenced the value of energy dissipated by RC beams. Further, results showed that RC beam constructed using recycled aggregate concrete containing 25% recycled aggregates exhibited energy dissipation capacity similar to or even better than that of control RC beam containing 100% natural aggregates.

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Performance of Recycled Aggregate Concrete for M25 Grade Concrete

International Journal of Engineering and Advanced Technology - Regular Issue ◽

10.35940/ijeat.b5130.129219 ◽

2019 ◽

Vol 9 (2) ◽

pp. 4694-4700

Keyword(s):

Tensile Strength ◽

Compressive Strength ◽

Flexural Strength ◽

Recycled Concrete ◽

Recycled Aggregate Concrete ◽

Recycled Aggregate ◽

Recycled Aggregates ◽

Aggregate Concrete ◽

Inorganic Particles ◽

Natural Aggregates

Recycled aggregates (RCA) are the aggregates which are made up of crushed, inorganic particles that are obtained from the construction demolition debris. Now a day’s protection of environment is the ultimate challenge to the society. So the usage of RCA’s is the best alternative for the aggregates which are obtained naturally in the construction activity. The scope of using these recycled concrete aggregates is increasing day by day. It reduces the cost effectively as we are using waste concrete as recycled aggregates. The main focus of this paper is to use find the strength qualities of recycled aggregates so as to use it as an alternative for the natural aggregates in high strength concrete for various construction activities. Comparison of workability, compressive strength, tensile strength, elastic modulus and flexural strength of recycled aggregate concrete is made with natural aggregate concrete. Here M25 grade concrete is taken and the natural aggregates were replaced with recycled aggregates in various percentages of 0%, 25%, 50%, 75% and 100%. The mix design for these replacement ratios are done by using code of IS 10262-2009. In order to determine the properties which were mentioned above a total of 60 cubes, 10 beams and 40 cylinders were casted. The compressive strength and tensile strength of RCA concrete have been determined for 7 days and 28 days where as the modulus of elasticity and the flexural strength of RCA concrete are determined after curing for the period of 28 days. The tests done on RCA concrete are compared with concrete which is obtained by natural aggregates As per IS codification the parameters which were determined are reducing moderately as the amount of aggregates which are recycled is being raised

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Experimental Characterization of Recycled Aggregate Concrete

MATEC Web of Conferences ◽

10.1051/matecconf/201930305004 ◽

2019 ◽

Vol 303 ◽

pp. 05004

Author(s):

Khaoula NAOUAOUI ◽

Azzeddine BOUYAHYAOUI ◽

Toufik CHERRADI

Keyword(s):

Compressive Strength ◽

Developed Countries ◽

Tourism Industry ◽

Recycled Concrete ◽

Recycled Aggregate Concrete ◽

Recycled Aggregate ◽

Recycled Aggregates ◽

Aggregate Concrete ◽

Different Types ◽

Natural Aggregates

The field of construction is evolving rapidly over the last decade. This is justified by the evolution of human activity in various fields mainly tourism, industry … and the aging of several buildings which implies a renovation or a demolition/re-construction. These construction activities involve a large need for aggregates for new construction and a large tonnage of waste from demolitions. In order to remedy this, various stakeholders in the field (suppliers, cement works, research centers, etc.) have valued recycled aggregate concrete (RAC). Recycled aggregates concrete is considered a new type of concrete based on the use of aggregates retrieved from the demolished structures instead of natural aggregates. This replacement affects, for sure, the characteristics of the concrete produced specially the mechanical properties. Developed countries have made a great progress in normalizing the use of recycled aggregates (RA) in concrete implementation as a result of many studies done since 80’s. In Morocco, recycled aggregates do not have any specific standards, and is used mainly in roads and pavements construction. Even if it’s not normalized this use is not recent, in 1999 during the rehabilitation of the expressway road of Casablanca which was severely damaged on both channels, the authorities have opted for the reuse of aggregates instead of reloading the existing pavement with a new one. The study is based on the use of recycled concrete crushed from an old building in Rabat- Morocco as aggregates and compared it with naturel aggregates from Morocco to determinate the effect of this replacement on several characteristics of concrete. This article is aiming to investigate experimentally the effect of RA in concrete using different replacement levels, different types of adjuvant and different percentages of it. The results show that over 30% of replacement, the compressive strength decreases considerably for basic concrete. In order to increase the compressive strength for the RAC with a percentage of replacement over 50%, we used different types of additives (Plasticizer, superplasticizer and new generation superplasticizer) and different percentage of it (0.5%, 1% and 1.5%): We concludes that, for our case, the add of plasticizer gives the best result and that the 1% replacement is the optimum percentage. The tests done on RCA made by plasticizer with different replacement level confirm the results without plasticizer: Compressive strength decreases when the replacement percentage increases.

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Concrete produced with recycled aggregates

Revista IBRACON de Estruturas e Materiais ◽

10.1590/s1983-41952012000500006 ◽

2012 ◽

Vol 5 (5) ◽

pp. 692-701 ◽

Cited By ~ 2

Author(s):

J. J. L. Tenório ◽

P. C. C. Gomes ◽

C. C. Rodrigues ◽

T. F. F. de Alencar

Keyword(s):

Coarse Aggregate ◽

Recycled Aggregate Concrete ◽

Recycled Aggregate ◽

Recycled Aggregates ◽

Hardened Concrete ◽

Specific Mass ◽

River Sand ◽

Recycled Coarse Aggregate ◽

Coarse Aggregates ◽

Natural Aggregates

This paper presents the analysis of the mechanical and durable properties of recycled aggregate concrete (RAC) for using in concrete. The porosity of recycled coarse aggregates is known to influence the fresh and hardened concrete properties and these properties are related to the specific mass of the recycled coarse aggregates, which directly influences the mechanical properties of the concrete. The recycled aggregates were obtained from construction and demolition wastes (CDW), which were divided into recycled sand (fine) and coarse aggregates. Besides this, a recycled coarse aggregate of a specific mass with a greater density was obtained by mixing the recycled aggregates of the CDW with the recycled aggregates of concrete wastes (CW). The concrete was produced in laboratory by combining three water-cement ratios, the ratios were used in agreement with NBR 6118 for structural concretes, with each recycled coarse aggregates and recycled sand or river sand, and the reference concrete was produced with natural aggregates. It was observed that recycled aggregates can be used in concrete with properties for structural concrete. In general, the use of recycled coarse aggregate in combination with recycled sand did not provide good results; but when the less porous was used, or the recycled coarse aggregate of a specific mass with a greater density, the properties of the concrete showed better results. Some RAC reached bigger strengths than the reference concrete.

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Resistance of Recycled Aggregate Concrete (RAC) Subjected to Drying-Wetting Cycles to Attack of Magnesium and Sodium Sulfates

Journal of Engineering ◽

10.1155/2020/9746341 ◽

2020 ◽

Vol 2020 ◽

pp. 1-9

Author(s):

Esam Hewayde ◽

Alireza Pachenari ◽

Hussin Al-Eleaj

Keyword(s):

Compressive Strength ◽

Recycled Aggregate Concrete ◽

Recycled Aggregate ◽

Recycled Aggregates ◽

Partial Immersion ◽

Concrete Mixtures ◽

Sulfate Solutions ◽

Mass Losses ◽

Natural Aggregates ◽

Sodium Sulfates

Recycled aggregates were widely used in the concrete industry as a replacement of natural aggregates in the last two decades. In this study, the resistance of concrete mixtures having various levels of recycled aggregate as a replacement of natural coarse aggregate to the attack of magnesium and sodium sulfates was investigated. Five mixtures made with 0%, 25%, 50%, 75%, and 100% recycled aggregate were partially immersed in magnesium and sodium sulfate solutions having concentrations of 2.5%, 4.5%, and 6.5% and subjected to drying-wetting cycles for a total of 10 weeks. Mass losses of concrete specimens owing to the attack of sulfate solutions and the effect of drying-wetting cycles were recorded weekly. Results show that the incorporation of recycled aggregate decreased the compressive strength of concrete at ages of 7 and 28 days. The decline in the compressive strength was more significant when the replacement percentage exceeds 50%. Mass losses of concrete specimens were found to be increased as the level of recycled aggregate increased. Mass losses of concrete specimens having 100% recycled aggregate were approximately as twice as those of concrete specimens having 0% recycled aggregate owing to 10 weeks of partial immersion in magnesium sulfate solutions of concentrations of 2.5%, 4.5%, and 6.5%. The attack of sodium sulfates was less aggressive than that of the magnesium sulfates. Results also show that the reduction in the compressive strength is directly proportional to the mass loss following a linear equation of R-squared value of 0.937.

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Effect of Aggregate Size on Recycled Aggregate Concrete under Equivalent Mortar Volume Mix Design

Applied Sciences ◽

10.3390/app112311274 ◽

2021 ◽

Vol 11 (23) ◽

pp. 11274

Author(s):

Haneol Jang ◽

Jeonghyun Kim ◽

Alena Sicakova

Keyword(s):

Mechanical Properties ◽

Distribution Curve ◽

Aggregate Size ◽

Recycled Aggregate Concrete ◽

Recycled Aggregate ◽

Mix Design ◽

Recycled Aggregates ◽

Particle Size Distribution Curve ◽

Aggregate Concrete ◽

Natural Aggregates

In this paper, the effect of the original aggregate size of the recycled aggregate on the mechanical properties of the recycled aggregate concrete was evaluated. A series of concretes were produced in which natural aggregates, recycled aggregates, and original aggregates in recycled aggregates were matched for a single particle size distribution curve. The replacement levels of recycled aggregate were 25% and 50%, and equivalent mortar volume mix design was applied for recycled aggregate concrete. The results show that the mechanical strength of recycled aggregate concrete increases with increasing original aggregate size. This effect was observed to be greater in concrete using recycled aggregate with a high residual mortar content.

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Recycled Aggregates Produced from Construction and Demolition Waste for Structural Concrete: Constituents, Properties and Production

Materials ◽

10.3390/ma14195748 ◽

2021 ◽

Vol 14 (19) ◽

pp. 5748

Author(s):

João Pacheco ◽

Jorge de Brito

Keyword(s):

Construction Material ◽

Mineral Resources ◽

Heterogeneous Material ◽

Recycled Aggregate Concrete ◽

Construction And Demolition Waste ◽

Recycled Aggregate ◽

Recycled Aggregates ◽

Demolition Waste ◽

Adequate Quality ◽

Natural Aggregates

This paper concerns the recovery of construction and demolition waste as coarse recycled aggregates for concrete. Coarse recycled aggregates may be used as a partial or total replacement of natural aggregates, contributing to the circular economy and minimizing landfill disposals as well as the consumption of natural mineral resources. However, construction and demolition waste is a heterogeneous material with undefined quality and the processing of this waste into recycled aggregates needs to ensure that the recycled aggregates have suitable properties for concrete. This paper summarizes several aspects related to coarse recycled aggregates, specifically addressing: (i) the typical composition of construction and demolition waste; (ii) the influence of different types of constituents on the properties of recycled aggregates and recycled aggregate concrete; (iii) requirements for recycled aggregates to be used in concrete; and (iv) production methods of recycled aggregates. It is argued that coarse recycled aggregates are a suitable construction material with adequate quality, even when common equipment is used in their production and preliminary separation as a key operation for ensuring the quality of the aggregates is recommended.

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Strength and Durability Studies on Geopolymer Recycled Aggregate Concrete

International Journal of Engineering & Technology ◽

10.14419/ijet.v7i2.24.12087 ◽

2018 ◽

Vol 7 (2.24) ◽

pp. 370 ◽

Cited By ~ 3

Author(s):

P Saravanakumar

Keyword(s):

Construction Industry ◽

Coarse Aggregate ◽

Recycled Aggregate Concrete ◽

Recycled Aggregate ◽

Recycled Aggregates ◽

Geopolymer Concrete ◽

Aggregate Concrete ◽

Natural Aggregates ◽

Strength And Durability ◽

Durability Performance

This paper aims to study the engineering and durability properties of fly ash-based geopolymer recycled aggregate concrete and the results were presented in this paper. The addition of recycled coarse aggregate (RCA) retrieved from construction and demolition(C&D) wastes showed promising function in construction industry as an alternative to natural aggregates. It conserves enormous quantities of natural resources and reduces the space required for the landfill disposal of C&D wastes. In this study an increment of 25% partial replacements by weight of natural aggregates with recycled aggregates in geopolymer concrete up to 100% replacements were studied. The concrete containing virgin aggregate and ordinary Portland cement was consider as control concrete and the results of geopolymer recycled aggregate concrete (GP-RAC) were compared with this. The fresh and mechanical properties of all the above four concrete mixes has been investigated. Results indicated that workability of geopolymer concrete decreases than control concrete and it took more than 24 hours to set. Geo polymer based recycled aggregate concrete exhibits better strength and durability performance than ordinary recycled aggregate concrete.

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Mechanical Performance of Bio-Based FRP-Confined Recycled Aggregate Concrete under Uniaxial Compression

Materials ◽

10.3390/ma14071778 ◽

2021 ◽

Vol 14 (7) ◽

pp. 1778

Author(s):

Elhem Ghorbel ◽

Mariem Limaiem ◽

George Wardeh

Keyword(s):

Mechanical Performance ◽

Recycled Aggregate Concrete ◽

Recycled Aggregate ◽

Recycled Aggregates ◽

Fiber Reinforced ◽

Traditional System ◽

Concrete Mixtures ◽

Compressive Performance ◽

Natural Aggregates ◽

Frp Confinement

This research investigates the effectiveness of bio-sourced flax fiber-reinforced polymer in comparison with a traditional system based on carbon fiber-reinforced epoxy polymer in order to confine recycled aggregate concretes. The experimental investigation was conducted on two series of concrete including three mixtures with 30%, 50%, and 100% of recycled aggregates and a reference concrete made with natural aggregates. The concrete mixtures were intended for a frost environment where an air-entraining agent was added to the mixture of the second series to achieve 4% air content. The first part of the present work is experimental and aimed to characterize the compressive performance of confined materials. The results indicated that bio-sourced composites are efficient in strengthening recycled aggregates concrete, especially the air-entrained one. It was also found that the compressive strength and the strain enhancement obtained from FRP confinement are little affected by the replacement ratio. The second part was dedicated to the analytical modeling of mechanical properties and stress–strain curves under compression. With the most adequate ultimate strength and strain prediction relationships, the full behavior of FRP-confined concrete can be predicted using the model developed by Ghorbel et al. to account for the presence of recycled aggregates in concrete mixtures.

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