Special Issue "New Trends in Recycled Aggregate Concrete"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Materials".

Deadline for manuscript submissions: closed (30 September 2018).

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A printed edition of this Special Issue is available here.

Special Issue Editors

Prof. Dr. Jorge de Brito
E-Mail Website
Guest Editor
Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais, 1049–001 Lisbon, Portugal
Interests: sustainable construction (recycled aggregates in concrete and mortars); bridge and building management systems; buildings service life (prediction); life cycle assessment; construction technology
Special Issues and Collections in MDPI journals
Prof. Dr. Chi Sun Poon
E-Mail Website
Guest Editor
Department of Civil & Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong M1504, China
Interests: Eco-friendly construction materials; waste recycling and management; high performance concrete
Dr. Baojian Zhan
E-Mail Website
Guest Editor
Department of Civil & Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong M1504, China
Interests: recycling and reuse of solid wastes; design and evaluation of cement-based materials; R&D of Eco-friendly construction materials

Special Issue Information

Dear Colleagues,

Concrete is the most used manufactured material in the world and certainly one of most impacting ones on the environment. However, there is no envisaged alternative to this material within a developing world context. Therefore, there is a pressing need to promote the reduction of the environmental impacts of concrete, guaranteeing, at the same time, that its technological and economic advantages remain valid.

One of the ways to achieve this objective is by replacing part or all of the natural aggregates with alternatives resulting from recycled materials or various types of waste/by-products from several industries, including construction. Many of the consequences on the technical, economic and environmental performance of recycled aggregate concrete have been established by the very dynamic research on this subject. Nevertheless, there is both a lag between research and industry practical applications and a number of subjects that still need to be explored, which represent new trends in the search for sustainable recycled aggregate concrete.

This Special Issue is therefore dedicated to “New Trends in Recycled Aggregate Concrete” and it intends to welcome contributions on, but not limited to, the following subjects:

  • Upscaling the use of recycled aggregate concrete in structural design;
  • Large scale applications of recycled aggregate concrete;
  • Long-term behaviour of recycled aggregate concrete;
  • Performance of recycled aggregate concrete in very aggressive environments;
  • Reliability of recycled aggregate concrete structures;
  • Life cycle assessment of recycled aggregate concrete;
  • Mesostructure analysis of recycled aggregate concrete.

Prof. Dr. Jorge de Brito
Prof. Dr. Chi Sun Poon
Dr. Baojian Zhan
Guest Editors

Manuscript Submission Information

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Keywords

  • recycled aggregates
  • mix design
  • structural concrete design
  • environmental performance
  • upscaling

Published Papers (17 papers)

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Editorial

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Open AccessEditorial
Special Issue: New Trends in Recycled Aggregate Concrete
Appl. Sci. 2019, 9(11), 2324; https://doi.org/10.3390/app9112324 - 06 Jun 2019
Abstract
Concrete is the most used manufactured material in the world and certainly one of those having the most impact on the environment [...] Full article
(This article belongs to the Special Issue New Trends in Recycled Aggregate Concrete) Printed Edition available

Research

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Open AccessArticle
A Study on the Properties of Recycled Aggregate Concrete and Its Production Facilities
Appl. Sci. 2019, 9(9), 1935; https://doi.org/10.3390/app9091935 - 10 May 2019
Cited by 5
Abstract
In recent years, the amount of construction waste and recycled aggregate has been increasing every year in Korea. However, as the recycled aggregate is poor quality, it is not used for concrete, and the Korean government has strengthened the quality standards for recycled [...] Read more.
In recent years, the amount of construction waste and recycled aggregate has been increasing every year in Korea. However, as the recycled aggregate is poor quality, it is not used for concrete, and the Korean government has strengthened the quality standards for recycled aggregate for concrete. In this study, research was conducted on the mechanical and durability characteristics of concrete using recycled aggregate, after developing equipment to improve the quality of recycled aggregate to increase the use of recycled aggregate for environmental improvements. The results illustrated improvements in the air volume, slump, compressive strength, freezing and thawing resistance, and drying shrinkage. Furthermore, this study is expected to contribute to the increased use of recycled aggregate in the future. Full article
(This article belongs to the Special Issue New Trends in Recycled Aggregate Concrete) Printed Edition available
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Open AccessArticle
Performance Evaluation of Reinforced Recycled Aggregate Concrete Columns under Cyclic Loadings
Appl. Sci. 2019, 9(7), 1460; https://doi.org/10.3390/app9071460 - 08 Apr 2019
Cited by 7
Abstract
Recycled concrete aggregates (RCAs) generated from construction and demolition activities have been recognized as a feasible alternative to natural aggregates (NAs). Naturally, the columns fabricated with reinforced recycled concrete (RRC) have been proposed and investigated to promote the structural use of recycled aggregate [...] Read more.
Recycled concrete aggregates (RCAs) generated from construction and demolition activities have been recognized as a feasible alternative to natural aggregates (NAs). Naturally, the columns fabricated with reinforced recycled concrete (RRC) have been proposed and investigated to promote the structural use of recycled aggregate concrete (RAC). There is still, however, very limited modeling research available to reproduce, accurately and efficiently, the seismic response of RRC columns under lateral cyclic loading; proper evaluations are also lacking on addressing the columns’ seismic behaviors. To fill some of those research gaps, a fiber-based numerical model is developed in this study and then validated with the experimental results published in the literature. Subsequently, the numerical model justified is applied to carry out a comprehensive parametric study to examine the effects of a range of variables on the hysteretic characteristics of RRC columns. Furthermore, a grey relational analysis is conducted to establish quantifiable evidence of key variable sensitivities. The evaluation results imply that the use of the additional water method (AWM) for manufacturing RAC is likely to reduce the lateral load-carrying capacity of the RRC columns (up to 10%), whereas the opposite would occur if a conventional mixing procedure is adopted. Moreover, compared with other factors such as steel area ratio, the content of RCA replacement has a less remarkable effect on the seismic performance of the RRC columns. In general, the RRC columns possess acceptable seismic-resistant properties, and they can be used in earthquake-prone regions with confidence. Full article
(This article belongs to the Special Issue New Trends in Recycled Aggregate Concrete) Printed Edition available
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Open AccessArticle
Mechanical Characteristics and Water Absorption Properties of Blast-Furnace Slag Concretes with Fly Ashes or Microsilica Additions
Appl. Sci. 2019, 9(7), 1279; https://doi.org/10.3390/app9071279 - 27 Mar 2019
Cited by 1
Abstract
The paper shows the results of an experimental tests campaign carried out on concretes with recycled aggregates added in substitution of sand. Sand, in fact, has been totally replaced once by blast-furnace slag and fly ashes, once by blast-furnace slag and microsilica. The [...] Read more.
The paper shows the results of an experimental tests campaign carried out on concretes with recycled aggregates added in substitution of sand. Sand, in fact, has been totally replaced once by blast-furnace slag and fly ashes, once by blast-furnace slag and microsilica. The aim is both to utilize industrial by-products and to reduce the use of artificial aggregates, which impose the opening of pits with high environmental damage. The results show that in the concretes so made the water absorption capacity has reduced and durability has improved. The test campaign and the results described in the present article are certainly useful and can be especially utilized for research on a larger scale in this field. Full article
(This article belongs to the Special Issue New Trends in Recycled Aggregate Concrete) Printed Edition available
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Open AccessArticle
Material Characterization for Sustainable Concrete Paving Blocks
Appl. Sci. 2019, 9(6), 1197; https://doi.org/10.3390/app9061197 - 21 Mar 2019
Cited by 1
Abstract
Recycled aggregates have been widely studied and used in concrete products nowadays. There are still many waste materials that can be used as recycled aggregates other than crushed concrete particles. This paper aims to study the property variations of sustainable concrete paving block [...] Read more.
Recycled aggregates have been widely studied and used in concrete products nowadays. There are still many waste materials that can be used as recycled aggregates other than crushed concrete particles. This paper aims to study the property variations of sustainable concrete paving block incorporating different contents of construction wastes. Five different types of waste materials were used in this project, including: recycled concrete coarse aggregate (RCCA), recycled concrete fine aggregate (RCFA), crushed glass (CG), crumb rubber (CB), and ground granulated blast furnace slag (GGBS). According to the test results of the properties of blocks mixed with different levels of wastes materials, it is concluded that adding both RCCA and RCFA in the block can decrease its strength and increase the water absorption. The suggested replacement levels for RCCA and RCFA are 60% and 20%, respectively. Mixing crushed glass in the concrete paving blocks as a type of coarse aggregates can improve the blocks’ strength and decrease the blocks’ water absorption. Addition of crumb rubber causes a significant deterioration of blocks’ properties except for its slip resistance. Full article
(This article belongs to the Special Issue New Trends in Recycled Aggregate Concrete) Printed Edition available
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Open AccessArticle
Analysis of Life Cycle Environmental Impact of Recycled Aggregate
Appl. Sci. 2019, 9(5), 1021; https://doi.org/10.3390/app9051021 - 12 Mar 2019
Cited by 3
Abstract
This study assessed the influence of matter discharged during the production (dry/wet) of recycled aggregate on global warming potential (GWP) and acidification potential (AP), eutrophication potential (EP), ozone depletion potential (ODP), biotic resource depletion potential (ADP), photochemical ozone creation potential (POCP) using the [...] Read more.
This study assessed the influence of matter discharged during the production (dry/wet) of recycled aggregate on global warming potential (GWP) and acidification potential (AP), eutrophication potential (EP), ozone depletion potential (ODP), biotic resource depletion potential (ADP), photochemical ozone creation potential (POCP) using the ISO 14044 (LCA) standard. The LCIA of dry recycled aggregate was 2.94 × 10−2 kg-CO2eq/kg, 2.93 × 10−5 kg-SO2eq/kg, 5.44 × 10−6 kg-PO43eq/kg, 4.70 × 10−10 kg-CFC11eq/kg, 1.25 × 10−5 kg-C2H4eq/kg, and 1.60 × 10−5 kg-Antimonyeq/kg, respectively. The environmental impact of recycled aggregate (wet) was up to 16~40% higher compared with recycled aggregate (dry); the amount of energy used by impact crushers while producing wet recycled aggregate was the main cause for this result. The environmental impact of using recycled aggregate was found to be up to twice as high as that of using natural aggregate, largely due to the greater simplicity of production of natural aggregate requiring less energy. However, ADP was approximately 20 times higher in the use of natural aggregate because doing so depletes natural resources, whereas recycled aggregate is recycled from existing construction waste. Among the life cycle impacts assessment of recycled aggregate, GWP was lower than for artificial light-weight aggregate but greater than for slag aggregate. Full article
(This article belongs to the Special Issue New Trends in Recycled Aggregate Concrete) Printed Edition available
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Open AccessArticle
Crushing Performance of Ultra-Lightweight Foam Concrete with Fine Particle Inclusions
Appl. Sci. 2019, 9(5), 876; https://doi.org/10.3390/app9050876 - 01 Mar 2019
Cited by 1
Abstract
Foam concrete is a low-density controlled strength material that can potentially be used for accommodating different types of particles—recycled fine aggregate being an example. The paste matrix of this material has a cellular microstructure, and bulk performance is readily affected by the inclusion [...] Read more.
Foam concrete is a low-density controlled strength material that can potentially be used for accommodating different types of particles—recycled fine aggregate being an example. The paste matrix of this material has a cellular microstructure, and bulk performance is readily affected by the inclusion of fines. To study the effect of inclusion of fines on mechanical performance and foam structure of foam concrete, a group of 0.55 g/cm3 foam–sand composite mixtures with high-volume fly ash replacement are investigated. The elastic modulus is measured by a vibrational frequency test. The crushing mechanics are determined by the load-displacement response from a penetration test. The effect of particle inclusion on the foam concrete microstructure is characterized using micro computed tomography. The results indicate that use of fine-graded sand particles at a small dosage simultaneously reduces cement content and enhances the crushing performance, however poor material performance is observed for a high sand content. The cellular structure of the foam–sand composite, and thus its mechanical behavior, can be substantially diminished by larger sand particles, especially when the particle size is larger than the voids in foam. Full article
(This article belongs to the Special Issue New Trends in Recycled Aggregate Concrete) Printed Edition available
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Open AccessArticle
Effect of Nylon Fiber Addition on the Performance of Recycled Aggregate Concrete
Appl. Sci. 2019, 9(4), 767; https://doi.org/10.3390/app9040767 - 22 Feb 2019
Cited by 2
Abstract
The adhered mortars in recycled aggregates (RA) may lower the performance of the concrete, by for instance reducing its strength and durability, and by cracking. In the present study, the effect of nylon fiber (NF) on the permeability as well as on the [...] Read more.
The adhered mortars in recycled aggregates (RA) may lower the performance of the concrete, by for instance reducing its strength and durability, and by cracking. In the present study, the effect of nylon fiber (NF) on the permeability as well as on the mechanical properties of concrete incorporating 100% RA was experimentally investigated. Concrete was produced by adding 0, 0.6 and 1.2 kg/m3 of NF and then cured in water for a predetermined period. Measurements of compressive and split tensile strengths, ultrasonic pulse velocity and total charge passed through concrete were carried out, and the corresponding test results were compared to those of concrete incorporating crushed stone aggregate (CA). In addition, the microstructures of 28-day concretes were examined by using the FE-SEM technique. The test results indicated that recycled coarse aggregate concrete (RAC) showed a lower performance than crushed stone aggregate concrete (CAC) because of the adhered mortars in RA. However, it was obvious that the addition of NF in RAC mixes was much more effective in enhancing the performance of the concretes due to the crack bridging effect from NF. In particular, a high content of NF (1.2 kg/m3) led to a beneficial effect on concrete properties compared to a low content of NF (0.6 kg/m3) with respect to mechanical properties and permeability, especially for RAC mixes. Full article
(This article belongs to the Special Issue New Trends in Recycled Aggregate Concrete) Printed Edition available
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Open AccessArticle
Residual Properties Analysis of Steel Reinforced Recycled Aggregate Concrete Components after Exposure to Elevated Temperature
Appl. Sci. 2018, 8(12), 2377; https://doi.org/10.3390/app8122377 - 24 Nov 2018
Cited by 2
Abstract
The application of recycled aggregate concrete (RAC) has developed rapidly in recent years. But how to evaluate the residual properties of RAC after the fires is more beneficial to the further popularization and application of RAC. This paper presents the residual properties of [...] Read more.
The application of recycled aggregate concrete (RAC) has developed rapidly in recent years. But how to evaluate the residual properties of RAC after the fires is more beneficial to the further popularization and application of RAC. This paper presents the residual properties of RAC and steel reinforced recycled aggregate concrete (SRRAC) components after exposure to elevated temperature. A total of 176 specimens (120 rectangular prisms specimens, 24 SRRAC short columns and 32 SRRAC beams) were designed and tested after exposure to elevated temperature. The parameters were considered in the test, including replacement percentage of recycled coarse aggregate (0%, 30%, 50%, 70% and 100%) and exposure to different temperatures (20, 200, 400, 600 and 800 degrees centigrade). According to the test results, heat damage and residual properties of specimens were analyzed in detail, such as surface change, mass loss, bearing capacity degradation, stiffness degradation, ductility and energy dissipation of specimens under the elevated temperature. The results showed that a series of significant physical phenomena occurred on the surface of RAC and SRRAC components after exposure to elevated temperature, such as the color changed from green-grey to gray-white, chapped on the concrete surface after 400 degrees centigrade and the mass loss of concrete is less than 10%. The degradation of mechanical properties degenerated significantly with the increase of temperature, such as the strength of RAC, and compressive capacity, bending capacity, shear capacity and stiffness of SRRAC components, among that, the degradation of the strength of RAC was most obvious, up to 26%. The ductility and energy dissipation of SRRAC components were insignificant affected by the elevated temperature. Mass loss ratio, peak deformation and bearing capacity showed a slight increase trend with the increase of replacement percentage. But the stiffness showed significant fluctuation when replacement percentage was 70% to 100%. And the ductility and energy dissipation showed significant fluctuation when replacement percentage was 30% to 70%. Full article
(This article belongs to the Special Issue New Trends in Recycled Aggregate Concrete) Printed Edition available
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Open AccessArticle
An Experimental Study on Flexural Behaviors of Reinforced Concrete Member Replaced Heavyweight Waste Glass as Fine Aggregate under Cyclic Loading
Appl. Sci. 2018, 8(11), 2208; https://doi.org/10.3390/app8112208 - 09 Nov 2018
Cited by 1
Abstract
The development of electronic technology has accelerated in recent decades. Consequently, electronic wastes such as cathode ray tube (CRT) glass are accumulated, and hazardous wastes including heavy metals are generated. Simultaneously, natural resources are required to create concrete; however, they are already exhausted. [...] Read more.
The development of electronic technology has accelerated in recent decades. Consequently, electronic wastes such as cathode ray tube (CRT) glass are accumulated, and hazardous wastes including heavy metals are generated. Simultaneously, natural resources are required to create concrete; however, they are already exhausted. Furthermore, heavyweight waste glass is considered to be the most suitable substitute for aggregate owing to its physical characteristics and chemical composition. However, structural results regarding the recycling of heavyweight waste glass as fine aggregate in Reinforced Concrete (RC) members are insufficient. Thus, herein, experimental study is conducted to evaluate whether RC members with heavyweight waste glass as fine aggregate can be applied for concrete structures. Flexural behavior tests of reinforced concrete members were performed. Fifteen specimens with different substitution ratios of heavyweight waste glass were prepared. The results showed that when all the fine aggregate is replaced by heavyweight waste glass in RC members, the heavyweight waste glass substitution ratio affected the crack occurrence patterns, and the possibility of a sudden failure of a member increased owing to concrete crushing in the compression zone. Additionally, the load capacity and flexural rigidity were affected by the substitution ratio of heavyweight waste glass; however, the flexural performance is improved when mineral admixture as a binder or a low water-binder ratio were used. Therefore, heavyweight waste glass is considered applicable for use as fine aggregate of concrete. Full article
(This article belongs to the Special Issue New Trends in Recycled Aggregate Concrete) Printed Edition available
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Open AccessArticle
Effect of Different Types of Recycled Concrete Aggregates on Equivalent Concrete Strength and Drying Shrinkage Properties
Appl. Sci. 2018, 8(11), 2190; https://doi.org/10.3390/app8112190 - 08 Nov 2018
Cited by 2
Abstract
Residual mortar attached to recycled concrete aggregate (RCA) always leads to a decrease in Young’s modulus and an increase in the drying shrinkage of RCA concrete, mainly due to an increase of total mortar volume. To overcome this inherent problem, the modified and [...] Read more.
Residual mortar attached to recycled concrete aggregate (RCA) always leads to a decrease in Young’s modulus and an increase in the drying shrinkage of RCA concrete, mainly due to an increase of total mortar volume. To overcome this inherent problem, the modified and equivalent mortar volume (EMV) methods were proposed by researchers. Despite the comparable test results, both models are still subject to the slump loss problem. Thus, under the same W/C (water to cement ratio) ratio and slump condition, this study assessed the influence of the modified EMV mix method on RCA concrete properties. A total of six mixes were proportioned using the modified EMV method with three different RCAs. Test results show that the concrete mixed with RCA produced from old PC concrete sleepers exhibited compressive strength, Young’s modulus, and flexural strength values within 2% variation, equivalent to those values of the companion natural aggregate concrete. In other mixes, compressive strength was found to decrease to 11–20%. It was observed that for 100% replacement of RCA mix, Young’s modulus increased to 10% and drying shrinkage increased to 8% only, while for 50% replacement of RCA mix, Young’s modulus decreased to 8% and drying shrinkage dropped to 4%. Full article
(This article belongs to the Special Issue New Trends in Recycled Aggregate Concrete) Printed Edition available
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Open AccessArticle
Using Neural Networks to Determine the Significance of Aggregate Characteristics Affecting the Mechanical Properties of Recycled Aggregate Concrete
Appl. Sci. 2018, 8(11), 2171; https://doi.org/10.3390/app8112171 - 06 Nov 2018
Cited by 3
Abstract
It has been proved that artificial neural networks (ANN) can be used to predict the compressive strength and elastic modulus of recycled aggregate concrete (RAC) made with recycled aggregates from different sources. This paper is a further study of the use of ANN [...] Read more.
It has been proved that artificial neural networks (ANN) can be used to predict the compressive strength and elastic modulus of recycled aggregate concrete (RAC) made with recycled aggregates from different sources. This paper is a further study of the use of ANN to analyze the significance of each aggregate characteristic and determine the best combinations of factors that would affect the compressive strength and elastic modulus of RAC. The experiments were carried out with 46 mixes with several types of recycled aggregates. The experimental results were used to build ANN models for compressive strength and elastic modulus, respectively. Different combinations of factors were selected as input variables until the minimum error was reached. The results show that water absorption has the most important effect on aggregate characteristics, further affecting the compressive strength of RAC, and that combined factors including concrete mixes, curing age, specific gravity, water absorption and impurity content can reduce the prediction error of ANN to 5.43%. Moreover, for elastic modulus, water absorption and specific gravity are the most influential, and the network error with a combination of mixes, curing age, specific gravity and water absorption is only 3.89%. Full article
(This article belongs to the Special Issue New Trends in Recycled Aggregate Concrete) Printed Edition available
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Open AccessArticle
Investigation of the Use of Recycled Concrete Aggregates Originating from a Single Ready-Mix Concrete Plant
Appl. Sci. 2018, 8(11), 2149; https://doi.org/10.3390/app8112149 - 03 Nov 2018
Cited by 1
Abstract
The waste produced from ready-mixed concrete (RMC) industries poses an environmental challenge regarding recycling. Three different waste products form RMC plants were investigated for use as recycled aggregates in construction applications. Crushed hardened concrete from test specimens of at least 40 MPa compressive [...] Read more.
The waste produced from ready-mixed concrete (RMC) industries poses an environmental challenge regarding recycling. Three different waste products form RMC plants were investigated for use as recycled aggregates in construction applications. Crushed hardened concrete from test specimens of at least 40 MPa compressive strength (HR) and crushed hardened concrete from returned concrete (CR) were tested for their suitability as concrete aggregates and then used as fine and coarse aggregate in new concrete mixtures. In addition, cement sludge fines (CSF) originating from the washing of concrete trucks were tested for their properties as filler for construction applications. Then, CSF was used at 10% and 20% replacement rates as a cement replacement for mortar production and as an additive for soil stabilization. The results show that, although there is some reduction in the properties of the resulting concrete, both HR and CR can be considered good-quality recycled aggregates, especially when the coarse fraction is used. Furthermore, HR performs considerably better than CR both as coarse and as fine aggregate. CSF seems to be a fine material with good properties as a filler, provided that it is properly crushed and sieved through a 75 μm sieve. Full article
(This article belongs to the Special Issue New Trends in Recycled Aggregate Concrete) Printed Edition available
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Open AccessArticle
Effect of Recycled Aggregate Quality on the Bond Behavior and Shear Strength of RC Members
Appl. Sci. 2018, 8(11), 2054; https://doi.org/10.3390/app8112054 - 25 Oct 2018
Cited by 3
Abstract
During the aggregate crushing process, natural aggregate and clinging mortar from existing concrete will inevitably produce small cracks and weak bonds between the aggregate and the existing cement mortar. The weaknesses of the existing cement mortar, adhered to a natural aggregate, negatively affect [...] Read more.
During the aggregate crushing process, natural aggregate and clinging mortar from existing concrete will inevitably produce small cracks and weak bonds between the aggregate and the existing cement mortar. The weaknesses of the existing cement mortar, adhered to a natural aggregate, negatively affect the properties of a recycled aggregate concrete, which prevents its application in reinforced concrete (RC) structures. Recycled aggregate can be classified into several categories, according to its physical and mechanical properties. The properties of concrete incorporated with the recycled aggregate of various qualities can be controlled, and the variability in its strength can also be reduced. This study aims to promote the application of recycled aggregate by investigating the effects of recycled aggregate quality (i.e., water absorption and the number of fine particles) classified by the Japanese Industrial Standards (JIS) on material properties, mechanical properties, and shear behavior of RC beams with recycled aggregate. Full article
(This article belongs to the Special Issue New Trends in Recycled Aggregate Concrete) Printed Edition available
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Open AccessArticle
An Experimental Study on Dynamic Mechanical Properties of Fiber-Reinforced Concrete under Different Strain Rates
Appl. Sci. 2018, 8(10), 1904; https://doi.org/10.3390/app8101904 - 12 Oct 2018
Cited by 4
Abstract
Fiber-reinforced concrete (FRC) has a great advantage in earthquake-resistant structures, as compared with regular concrete. However, there are many difficulties in the construction and maintenance of concrete structures due to the high density and easy corrosion of the steel fiber in commonly used [...] Read more.
Fiber-reinforced concrete (FRC) has a great advantage in earthquake-resistant structures, as compared with regular concrete. However, there are many difficulties in the construction and maintenance of concrete structures due to the high density and easy corrosion of the steel fiber in commonly used steel FRC. With the development of polymer material science, polyvinyl alcohol (PVA) fiber has been rapidly promoted for use in FRC because of its low density, high strength, and large elongation at break value. Dynamic uniaxial compression and splitting tensile experiments of FRC with PVA fiber were carried out with two matrix strengths (i.e., C30 and C40), which were blended with PVA fibers with a length of 12 mm in different volume contents (0, 0.2, 0.4, and 0.6%), at the age of 28 days, under different strain rates (i.e., 10−5, 10−4, 10−3, and 10−2 s−1). The results show that PVA has an obvious enhancing and toughening effect on concrete, which can improve its brittle properties and residual strength. With increasing strain rate, the compressive strength, split tensile strength, and elastic modulus increase to a certain extent, while the toughness index and the peak strain decrease to a certain degree. The post-peak deformation characteristic changes from a brittle failure of sudden caving to a ductile failure with dense cracking. The effect of PVA is different when enhancing the concrete with two different matrix strengths. The lower the matrix strength, the more obvious the enhancement effect of the fiber, showing characteristics of a higher compressive strength and low split tensile strength in FRC with low strength and a smoother post-peak stress–strain curve. Full article
(This article belongs to the Special Issue New Trends in Recycled Aggregate Concrete) Printed Edition available
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Open AccessArticle
Can We Truly Predict the Compressive Strength of Concrete without Knowing the Properties of Aggregates?
Appl. Sci. 2018, 8(7), 1095; https://doi.org/10.3390/app8071095 - 05 Jul 2018
Cited by 11
Abstract
This paper is focused on the influence of the geological nature and quality of the aggregates on the compressive strength of concrete and explains why it is important not to ignore the characteristics of aggregates in the estimation of the strength of concrete, [...] Read more.
This paper is focused on the influence of the geological nature and quality of the aggregates on the compressive strength of concrete and explains why it is important not to ignore the characteristics of aggregates in the estimation of the strength of concrete, even for virgin aggregates. For this purpose, three original (Abrams, American Concrete Institute Manual of concrete practice and Slater) and two modified (Bolomey and Feret) models were used to calculate the strength of concrete by considering results of various publications. The results show that the models do not properly predict the strength of concrete when the characteristics of aggregates are neglected. The scatter between the calculated and experimental compressive strength of concrete, even when made with natural aggregates (NAs) only, was significant. For the same mix composition (with similar cement paste quality), there was a significant difference between the results when NAs of various geological nature (e.g., limestone, basalt, granite, sandstone) were used in concrete. The same was true when different qualities (namely in terms of density, water absorption and Los Angles abrasion) of aggregates were used. The scatters significantly decreased when the mixes were classified based on the geological nature of the aggregates. The same occurred when the mixes were classified based on their quality. For both modified models, the calculated strength of mixes made with basalt was higher than that of the mixes containing other types of the aggregates, followed by mixes containing limestone, quartz and granite. In terms of the quality of the aggregates, the calculated strength of concrete increased (was overestimated) as the quality of the aggregates decreased. The influence of the aggregates on the compressive strength of concrete became much more discernible when recycled aggregates were used mainly due to their more heterogeneous characteristics. Full article
(This article belongs to the Special Issue New Trends in Recycled Aggregate Concrete) Printed Edition available
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Open AccessArticle
Analysis and Modelling of Shrinkage and Creep of Reactive Powder Concrete
Appl. Sci. 2018, 8(5), 732; https://doi.org/10.3390/app8050732 - 05 May 2018
Cited by 2
Abstract
The objective of this study was to examine the shrinkage and creep of reactive power concrete (RPC) with different steel fibre contents (0%, 1% and 2% by volume). A total of 37 RPC specimens were prepared and tested for compression strength, elastic modulus, [...] Read more.
The objective of this study was to examine the shrinkage and creep of reactive power concrete (RPC) with different steel fibre contents (0%, 1% and 2% by volume). A total of 37 RPC specimens were prepared and tested for compression strength, elastic modulus, shrinkage, and creep. In addition, different axial stress ratios (0.2, 0.3 and 0.4) were used in the creep tests. Furthermore, the accuracy of the ACI 209-82 model, CEB-FIP 90 model, B3 model, and GL 2000 model for predicting the shrinkage and creep of RPC was evaluated and new numerical shrinkage and creep models were developed. The experimental results revealed that the compressive strength and elastic modulus increase with increasing steel fibre content. The shrinkage and creep decreased with increasing addition of steel fibre from 0% to 2%. A good linear relationship was found between the axial stress ratios and creep strain. All four existing models were unable to accurately predict the shrinkage and creep of RPC. A good agreement between the experimental results and proposed shrinkage and creep numerical models was observed. Therefore, it is suggested that the proposed shrinkage and creep models can be used to calculate the shrinkage and creep of RPC. Full article
(This article belongs to the Special Issue New Trends in Recycled Aggregate Concrete) Printed Edition available
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