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

Materials ◽  
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.

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

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.

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

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2625 ◽  
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.

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

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.

scholarly journals Appraisal of Processing Techniques for Recycled Aggregates in Concrete

2019 ◽  
Vol 8 (6) ◽  
pp. 1661-1665 ◽  
Keyword(s):  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Bacterial Suspension ◽  
Mechanical Method ◽  
Treatment Techniques ◽  
Chemical Admixture ◽  
Surface Permeability ◽  
Natural Aggregates ◽  
Processing Techniques

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.

scholarly journals Performance of Recycled Aggregate Concrete for M25 Grade Concrete

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

scholarly journals Experimental Characterization of Recycled Aggregate Concrete

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.

Microstructural Features of Recycled Aggregate Concrete: From Non-Structural to High-Performance Concrete

2019 ◽  
Vol 25 (3) ◽  
pp. 601-616 ◽  
Author(s):  
Diogo Pedro ◽  
Mafalda Guedes ◽  
Jorge de Brito ◽  
Luís Evangelista
Keyword(s):  
High Performance ◽  
Mechanical Performance ◽  
High Performance Concrete ◽  
Concrete Strength ◽  
High Strength ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Sequential Approach

AbstractThe use of concrete-recycled aggregates to produce high-performance concrete is limited by insufficient correlation between resulting microstructure and its influence on mechanical performance reproducibility. This work addresses this issue in a sequential approach: concrete microstructure was systematically analyzed and characterized by scanning electron microscopy and results were correlated with concrete compressive strength and water absorption ability. The influence of replacing natural aggregates (NA) with recycled concrete aggregates (RCA), with different source concrete strength levels, of silica fume (SF) addition and of mixing procedure was tested. The results show that the developed microstructure depends on the concrete composition and is conditioned by the distinct nature of NA, recycled aggregates from high-strength source concrete, and recycled aggregates from low-strength source concrete. SF was only effective at concrete densification when a two-stage mixing approach was used. The highest achieved strength in concrete with 100% incorporation of RCA was 97.3 MPa, comparable to that of conventional high-strength concrete with NA. This shows that incorporation of significant amounts of RCA replacing NA in concrete is not only a realistic approach to current environmental goals, but also a viable route for the production of high-performance concrete.

scholarly journals Concrete produced with recycled aggregates

2012 ◽  
Vol 5 (5) ◽  
pp. 692-701 ◽  
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.

scholarly journals Flexural fatigue characteristics of steel fiber reinforced recycled aggregate concrete (SFRRAC)

2009 ◽  
Vol 7 (1) ◽  
pp. 19-33 ◽  
Author(s):  
M. Heeralal ◽  
Rathish Kumar ◽  
Y.V. Rao
Keyword(s):  
Steel Fiber ◽  
Research Work ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Fiber Reinforced ◽  
Aggregate Concrete ◽  
Flexural Fatigue ◽  
Rigid Pavements ◽  
Structural Applications

This research work is aimed at investigating the flexural fatigue behavior of Steel Fiber Reinforced Recycled Aggregate Concrete (SFRRAC). This study gains importance in view of the wide potential for demolished concrete to serve as a source of quality aggregate feed stock in a variety of structural and non-structural applications. This is a continuation of a series of investigations being conducted aimed at optimizing the utilization of recycled aggregate concrete in rigid pavements. A total of 72 standard flexure specimens of 100mm x 100mm x 450mm were cast and tested for flexure under both static and fatigue loading. The parameters of the investigation included the different replacements of recycled aggregate in natural aggregate, presence of steel fiber and different stress levels. The study showed that the recycled aggregates can be used in rigid pavements also and the inclusion of fibers can benefit the fatigue performance of recycled aggregate concrete.

scholarly journals Durability Indicators in High Absorption Recycled Aggregate Concrete

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Luis F. Jiménez ◽  
Eric I. Moreno
Keyword(s):  
Fluid Transport ◽  
Coarse Aggregate ◽  
Chloride Ion ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Concrete Mixtures ◽  
Concrete Production ◽  
High Absorption

The use of recycled aggregates in structural concrete production has the inconvenience of increasing the fluid transport properties, such as porosity, sorptivity, and permeability, which reduces the resistance against penetration of environmental loads such as carbon dioxide and chloride ion. In this paper, behavior of ten concrete mixtures with different percentages of coarse aggregate replacement was studied. The recycled material was recovered by crushing of concrete rubble and had high absorption values. The results showed that it is possible to achieve good resistance to carbonation and chloride penetration with up to 50% replacement of recycled coarse aggregate for 0.5 water/cement ratio. Finally, new indexes for porosity and sorptivity were proposed to assess the quality of concrete.

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