Special Issue "Low Binder Concrete and Mortars"

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

Deadline for manuscript submissions: closed (31 December 2019).

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Special Issue Editors

Prof. Dr. Jorge de Brito
Website
Guest Editor
Department of Civil Engineering, Architecture and Georresources, 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
Dr. Rawaz Kurda
Website
Guest Editor
Department of Civil Engineering, Technical Engineering College, Erbil Polytechnic University, Erbil 44001, Kurdistan-Region, Iraq
Interests: Supplementary cementitious materials; recycled aggregates; sustainable concrete and mortar; Alkali activation; Life Cycle Assessment; quality performance; costs; multi-criteria analysis; optimization.
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

It is well known that after water, concrete and mortars are the most demanded materials worldwide. Therefore, they have a significant influence on environmental impacts (EI), namely, because of their cement content. Thus, many alternative materials such as supplementary cementitious materials have been proposed to be used in order to decrease the EI of mortar and concrete. However, studies regarding extremely low binder content, namely, cement, are still very scarce.

This Special Issue of Applied Sciences provides a forum for original studies and comprehensive reviews on the technical performance (e.g., mechanical and durability), economics, and EI (e.g., global warming and energy consumption) of concrete and/or mortar containing low binder content. In other words, any attempts or techniques, i.e., using any type of supplementary cementitious materials, alkali activation (e.g., geopolymers), strengthening systems (e.g., fibers), by-product nano materials, additives, etc., that help to decrease the cement content of concrete and mortars, are welcome.

Prof. Dr. Jorge de Brito
Dr. Rawaz Kurda
Guest Editors

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Keywords

  • Concrete and mortar technology
  • Sustainable development
  • Supplementary cementitious materials
  • Nano-materials
  • Alkali activation–polymer composites
  • Concrete admixtures
  • Fiber-reinforced concrete
  • Life cycle assessment
  • Costs

Published Papers (19 papers)

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Editorial

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Open AccessEditorial
Special Issue Low Binder Concrete and Mortars
Appl. Sci. 2020, 10(11), 3866; https://doi.org/10.3390/app10113866 - 02 Jun 2020
Abstract
It is well known that, after water, concrete and mortars are the most demanded materials worldwide [...] Full article
(This article belongs to the Special Issue Low Binder Concrete and Mortars) Printed Edition available

Research

Jump to: Editorial, Review

Open AccessFeature PaperArticle
Effect of Alkali Concentration on the Activation of Carbonate-High Illite Clay
Appl. Sci. 2020, 10(7), 2203; https://doi.org/10.3390/app10072203 - 25 Mar 2020
Cited by 1
Abstract
The present study explores the effect of activating solution concentration (4, 6 and 8 M NaOH) on mechanically and thermally pre-treated carbonate-high illite clay (LCR). Pastes were prepared with an alkaline solution/clay (S/B) ratio of 0.55, which were cured at room temperature and [...] Read more.
The present study explores the effect of activating solution concentration (4, 6 and 8 M NaOH) on mechanically and thermally pre-treated carbonate-high illite clay (LCR). Pastes were prepared with an alkaline solution/clay (S/B) ratio of 0.55, which were cured at room temperature and relative humidity > 90% in a climatic chamber. At two and 28 days, compressive mechanical strength was determined, and the reaction products were characterised by X-ray Powder Diffraction analysis (XRPD), Fourier-transform infrared spectroscopy (FTIR) and Scanning Electron Microscopy - Energy Dispersive X-ray spectroscopy (SEM/EDX). Results obtained showed that the presence of reactive calcium in the starting clay induces co-precipitation of a mix of gels: An aluminium-enriched C-S-H gel (C-A-S-H) and a N-A-S-H gel, in which sodium is partially replaced by calcium (N,C)-A-S-H. Pastes prepared with higher (6 or 8 M) activator concentrations exhibit a more compact matrix than the ones prepared with 4 M NaOH. The findings show that the use of a 6 M NaOH solution yields a binder with two days compressive strength >20 MPa and 28 days strength of over 30 MPa. Full article
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Open AccessArticle
Evaluation of the Ecotoxicological Potential of Fly Ash and Recycled Concrete Aggregates Use in Concrete
Appl. Sci. 2020, 10(1), 351; https://doi.org/10.3390/app10010351 - 03 Jan 2020
Cited by 2
Abstract
This study applies a methodology to evaluate the ecotoxicological potential of raw materials and cement-based construction materials. In this study, natural aggregates and Portland cement were replaced with non-conventional recycled concrete aggregates (RA) and fly ash (FA), respectively, in the production of two [...] Read more.
This study applies a methodology to evaluate the ecotoxicological potential of raw materials and cement-based construction materials. In this study, natural aggregates and Portland cement were replaced with non-conventional recycled concrete aggregates (RA) and fly ash (FA), respectively, in the production of two concrete products alternative to conventional concrete (used as reference). The experimental program involved assessing both the chemical properties (non-metallic and metallic parameters) and ecotoxicity data (battery of tests with the luminescent bacterium Vibrio fischeri, the freshwater crustacean Daphnia magna, and the yeast Saccharomyces cerevisiae) of eluates obtained from leaching tests of RA, FA, and the three concrete mixes. Even though the results indicated that RA and FA have the ability to release some chemicals into the water and induce its alkalinisation, the respective eluate samples presented no or low levels of potential ecotoxicity. However, eluates from concrete mixes produced with a replacement ratio of Portland cement with 60% of FA and 100% of natural aggregates and produced with 60% of FA and 100% of RA were classified as clearly ecotoxic mainly towards Daphnia magna mobility. Therefore, raw materials with weak evidences of ecotoxicity could lead to the production of concrete products with high ecotoxicological potential. Overall, the results obtained highlight the importance of integrating data from the chemical and ecotoxicological characterization of materials’ eluate samples aiming to assess the possible environmental risk of the construction materials, namely of incorporating non-conventional raw materials in concrete, and contributing to achieve construction sustainability. Full article
(This article belongs to the Special Issue Low Binder Concrete and Mortars) Printed Edition available
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Open AccessArticle
The Influence of Thermo-Mechanical Activation of Bentonite on the Mechanical and Durability Performance of Concrete
Appl. Sci. 2019, 9(24), 5549; https://doi.org/10.3390/app9245549 - 17 Dec 2019
Cited by 1
Abstract
Despite presenting a very high global warming toll, Portland cement concrete is the most widely used construction material in the world. The eco-efficiency, economy, and the overall mechanical and durability performances of concrete can be improved by incorporating supplementary cementitious materials (SCMs) as [...] Read more.
Despite presenting a very high global warming toll, Portland cement concrete is the most widely used construction material in the world. The eco-efficiency, economy, and the overall mechanical and durability performances of concrete can be improved by incorporating supplementary cementitious materials (SCMs) as partial substitutions to ordinary Portland cement (OPC). Naturally found bentonite possesses pozzolanic properties and has very low carbon footprint compared to OPC. By applying activation techniques, the reactivity of bentonite can be improved, and its incorporation levels can be maximized. In this study, the influence of mechanical and thermo-mechanical activation of bentonite is investigated on properties of concrete. Bentonite was used for 0%, 10%, 15%, 20%, 25%, 30%, and 35% mass replacements of OPC. Mechanical (compressive strength and split tensile strength) and durability (water absorption, sorptivity coefficient, and acid attack resistance) properties were studied. Results of experimental testing revealed that, concrete containing bentonite showed good mechanical performance, while durability was significantly improved relative to control mix. Application of thermo-mechanical activation can enhance the incorporation levels of bentonite in concrete. At 15% and 25%, bentonite produced optimum results for mechanical and thermo-mechanical activation, respectively. Bentonite inclusion is more beneficial to the durability than the mechanical strength of concrete. Full article
(This article belongs to the Special Issue Low Binder Concrete and Mortars) Printed Edition available
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Open AccessArticle
Potential Activity of Recycled Clay Brick in Cement Stabilized Subbase
Appl. Sci. 2019, 9(23), 5208; https://doi.org/10.3390/app9235208 - 29 Nov 2019
Cited by 1
Abstract
Construction waste is one of the products in the process of urbanization. From the perspective of economy and environmental protection, this study used crushed construction waste clay brick to replace the fine aggregate of cement stabilized macadam subbase in certain proportions, and the [...] Read more.
Construction waste is one of the products in the process of urbanization. From the perspective of economy and environmental protection, this study used crushed construction waste clay brick to replace the fine aggregate of cement stabilized macadam subbase in certain proportions, and the optimum proportion was obtained according to the unconfined compressive strength of 7 days (d), 28 d, and 90 d. The “modified EDTA titration experiment" was also used to explain how the potential activity of construction waste clay brick works in cement stabilized macadam. The result obtained is that an optimal replacement ratio of 50% exists when using construction waste clay brick to replace the fine aggregate of cement stabilized macadam, and its unconfined compressive strength is higher than that of the 0% replacement ratio specimens; that is, the potential activity of the construction waste clay brick contributes the most to the unconfined compressive strength of the specimens at this proportion. According to the blending method and proportion obtained in this study, the application of construction waste clay bricks in a practical project can maximize environmental protection in road engineering and economic benefits simultaneously. Full article
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Open AccessArticle
Predicting Compressive Strength of Cement-Stabilized Rammed Earth Based on SEM Images Using Computer Vision and Deep Learning
Appl. Sci. 2019, 9(23), 5131; https://doi.org/10.3390/app9235131 - 27 Nov 2019
Cited by 5
Abstract
Predicting the compressive strength of cement-stabilized rammed earth (CSRE) using current testing machines is time-consuming and costly and may harm the environment due to the samples’ waste. This paper presents an automatic method using computer vision and deep learning to solve the problem. [...] Read more.
Predicting the compressive strength of cement-stabilized rammed earth (CSRE) using current testing machines is time-consuming and costly and may harm the environment due to the samples’ waste. This paper presents an automatic method using computer vision and deep learning to solve the problem. For this purpose, a deep convolutional neural network (DCNN) model is proposed, which was evaluated on a new in-house scanning electron microscope (SEM) image database containing 4284 images of materials with different compressive strengths. The experimental results show reasonable prediction results compared to other traditional methods, achieving 84% prediction accuracy and a small (1.5) oot Mean Square Error (RMSE). This indicates that the proposed method (with some enhancements) can be used in practice for predicting the compressive strength of CSRE samples. Full article
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Open AccessArticle
Short-Term Deformability of Three-Dimensional Printable EVA-Modified Cementitious Mortars
Appl. Sci. 2019, 9(19), 4184; https://doi.org/10.3390/app9194184 - 08 Oct 2019
Cited by 2
Abstract
This study experimentally examined the deformability of cementitious mortars modified with ethylene-vinyl acetate (EVA) for use in extrusion-based additive construction. The research was based on the author’s previous study of the properties of fresh EVA-modified cementitious mixtures for use in additive construction via [...] Read more.
This study experimentally examined the deformability of cementitious mortars modified with ethylene-vinyl acetate (EVA) for use in extrusion-based additive construction. The research was based on the author’s previous study of the properties of fresh EVA-modified cementitious mixtures for use in additive construction via extrusion. The particular focus was on these mortars’ short-term deformation factors, including the modulus of elasticity, drying shrinkage, and thermal expansion. The experimental results indicate that as the EVA/cement ratio was increased, the compressive strength and elastic modulus tended to decrease but the maximum compressive strain increased. At 28 days, the drying shrinkage tended to increase as the EVA/cement ratio was increased. The coefficient of thermal expansion was also found to increase as the EVA/cement ratio was increased. A very high correlation was found between these three deformation factors and the EVA/cement ratio. Given these results, it was determined that the addition of EVA powder to EVA-modified cementitious mortars used in extrusion-based additive construction could adversely affect their short-term deformation factors. However, increasing the EVA/cement ratio resulted in a decrease in the modulus of elasticity, thereby reducing the level of stress caused by drying shrinkage and thermal expansion. This effect will eventually lead to improvements in the degree of extensibility, thereby offsetting the negative impacts. However, it is still desirable to minimize the EVA/cement ratio to the extent that adequate properties for the fresh material can be obtained. Full article
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Open AccessArticle
Mechanical Properties of Sandstone Cement-Stabilized Macadam
Appl. Sci. 2019, 9(17), 3460; https://doi.org/10.3390/app9173460 - 22 Aug 2019
Cited by 1
Abstract
Application of sandstone in cement-stabilized macadam (CSM) is an effective way to utilize sandstone. To determine the feasibility of using sandstone as a CSM aggregate, a series of experimental investigations, such as unconfined compressive strength (UCS) tests, Brazilian splitting tests and freeze-thaw cycle [...] Read more.
Application of sandstone in cement-stabilized macadam (CSM) is an effective way to utilize sandstone. To determine the feasibility of using sandstone as a CSM aggregate, a series of experimental investigations, such as unconfined compressive strength (UCS) tests, Brazilian splitting tests and freeze-thaw cycle tests, were conducted on sandstone cement-stabilized macadam (SCSM). Three mixed variables, covering the cement content, aggregate type and curing period, were set as influence factors. The testing results indicated that the UCS, indirect tensile strength (ITS) and frost resistance property of the test-pieces increased with cement content and curing age. Considering the asphalt pavement design specifications for China, the UCS and ITS values of the SCSM complied with the requirements of light traffic road construction before freeze-thaw cycles. However, the SCSM subjected to freezing and thawing meets the requirements only when the cement content is 4.5%. Therefore, it is noteworthy that CSM containing sandstone aggregates should be applied with caution in cold region because of insufficient freeze resistance. Full article
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Open AccessArticle
Advances in the Study of the Behavior of Full-Depth Reclamation (FDR) with Cement
Appl. Sci. 2019, 9(15), 3055; https://doi.org/10.3390/app9153055 - 29 Jul 2019
Cited by 3
Abstract
Road maintenance and rehabilitation are expected to meet modern society’s demands for sustainable development. Full-depth reclamation with cement as a binder is closely linked to the concept of sustainability. In addition to the environmental benefits of reusing the existing pavement as aggregate, this [...] Read more.
Road maintenance and rehabilitation are expected to meet modern society’s demands for sustainable development. Full-depth reclamation with cement as a binder is closely linked to the concept of sustainability. In addition to the environmental benefits of reusing the existing pavement as aggregate, this practice entails significant technical and economic advantages. In Spain, in the absence of tests specifically designed to determine the behavior of recycled pavements stabilized with cement, these materials are treated as soil-cement or cement-bound granular material. This assumption is not entirely accurate, because this recycled pavement contains some bituminous elements that reduce its stiffness. This study aimed to obtain the relationships between flexural strength (FS) and the parameters that describe the pavement behavior (long-term unconfined compressive strength (UCS) and indirect tensile strength (ITS)) and compare the findings with the relationships between these parameters in soil-cement and cement-bound granular materials. The results showed that the similar behavior hypothesis is not entirely accurate for recycled pavements stabilized with cement, because they have lower strength values—although, this is not necessarily an indication of poorer performance. Full article
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Open AccessArticle
Mechanical Properties and Microstructure of Polyvinyl Alcohol (PVA) Modified Cement Mortar
Appl. Sci. 2019, 9(11), 2178; https://doi.org/10.3390/app9112178 - 28 May 2019
Cited by 3
Abstract
The mechanical properties of cement mortars with 0~2.0% (by mass) polyvinyl alcohol (PVA) were experimentally studied, and the effects of PVA incorporation on the hydration products and microstructure of the cement mortar were determined with differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy [...] Read more.
The mechanical properties of cement mortars with 0~2.0% (by mass) polyvinyl alcohol (PVA) were experimentally studied, and the effects of PVA incorporation on the hydration products and microstructure of the cement mortar were determined with differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results show that the rational content of PVA formed evenly dispersed network-like thin films within the cement matrix, and these network-like films can bridge cracks in the cement matrix and improve the mechanical properties of the cement mortar. Over- incorporation of PVA may result in the formation of large piece polymer films that coat the cement particles, delay the hydration of the cement mortar and adversely affect its performance. The mechanical properties of the cement mortar show a significant increase and then decrease with a change in the PVA incorporation. When the PVA content was 0.6% and 1.0%, the mortar had the best compressive and flexural strengths, respectively. The compressive strength of the cement mortar increased by 12.15% for a PVA content of 0.6%, and the flexural strength of the cement mortar increased by 24.83% for a PVA content of 1.0%. Full article
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Open AccessArticle
Effect of Incorporating Waste Limestone Powder into Solid Waste Cemented Paste Backfill Material
Appl. Sci. 2019, 9(10), 2076; https://doi.org/10.3390/app9102076 - 20 May 2019
Cited by 3
Abstract
To effectively reuse waste limestone powder, which is a major solid waste around mines, we replaced limestone powder back into a part of cement in solid waste cemented paste backfill (SWCPB) and studied the parameters of pore structures. To optimize the pore microstructure [...] Read more.
To effectively reuse waste limestone powder, which is a major solid waste around mines, we replaced limestone powder back into a part of cement in solid waste cemented paste backfill (SWCPB) and studied the parameters of pore structures. To optimize the pore microstructure characteristics of SWCPB in mines, two different components and grade tailings were selected. The samples were characterized by scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR) to examine the pore properties and microstructure of SWCPB. The results showed that (1) at the later curing stage, with the optimization of pore characteristics and microstructure through the limestone powder admixture, the strength of SWCFB was guaranteed at a 20% replacement degree of cement. (2) Porosity, macropore proportion, and the average pore radius all negatively correlated with limestone powder content, which were reduced by 7.15%, 46.35%, and 16.37%, respectively. (3) Limestone powder as a crystal nucleus participated in the hydration reaction and was embedded into the product to enhance the strength. Full article
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Open AccessArticle
Experimental Study on Flexural Behavior of TRM-Strengthened RC Beam: Various Types of Textile-Reinforced Mortar with Non-Impregnated Textile
Appl. Sci. 2019, 9(10), 1981; https://doi.org/10.3390/app9101981 - 15 May 2019
Cited by 5
Abstract
In this study, to compare strengthening efficiency and flexural behaviors of textile- reinforced mortar (TRM) according to various types of strengthening methods without the textile being impregnated, ten specimens were tested. The results showed that TRM was beneficial for uniform distribution of cracks [...] Read more.
In this study, to compare strengthening efficiency and flexural behaviors of textile- reinforced mortar (TRM) according to various types of strengthening methods without the textile being impregnated, ten specimens were tested. The results showed that TRM was beneficial for uniform distribution of cracks and increased the strengthening efficiency and load-bearing capacity, as textile reinforcement ratio and textile lamination increased and the mesh size of the textile decreased and mechanical end anchorage applied. However, the strengthening effect was shown obviously until the yield load considering structural safety and serviceability. Full article
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Open AccessArticle
Limestone and Calcined Clay-Based Sustainable Cementitious Materials for 3D Concrete Printing: A Fundamental Study of Extrudability and Early-Age Strength Development
Appl. Sci. 2019, 9(9), 1809; https://doi.org/10.3390/app9091809 - 30 Apr 2019
Cited by 15
Abstract
The goal of this study is to investigate the effects of different grades of calcined clay on the extrudability and early-age strength development under ambient conditions. Four mix designs were proposed. Three of them contained high, medium, and low grades of calcined clay, [...] Read more.
The goal of this study is to investigate the effects of different grades of calcined clay on the extrudability and early-age strength development under ambient conditions. Four mix designs were proposed. Three of them contained high, medium, and low grades of calcined clay, respectively, and one was the reference without calcined clay. In terms of extrudability, an extrusion test method based on the ram extruder was introduced to observe the quality of extruded material filaments, and to determine the extrusion pressure of tested materials at different ages. For evaluating the very early-age strength development, the penetration resistance test, the green strength test, and the ultrasonic pulse velocity test were applied. Furthermore, the mechanical properties of the developed mix designs were determined by the compressive strength test at 1, 7 and 28 days. Finally, the main finding of this study was that increasing the metakaolin content in calcined clay could significantly increase the extrusion pressures and green strength, shorten the initial setting time and enhance the compressive strength at 1, 7, and 28 days. Full article
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Open AccessArticle
Components of the Fracture Response of Alkali-Activated Slag Composites with Steel Microfibers
Appl. Sci. 2019, 9(9), 1754; https://doi.org/10.3390/app9091754 - 27 Apr 2019
Cited by 2
Abstract
Knowledge of the mechanical and primarily fracture parameters of composites with a brittle matrix is essential for the quantification of their resistance to crack initiation and growth, and also for the specification of material model parameters employed for the simulation of the quasi-brittle [...] Read more.
Knowledge of the mechanical and primarily fracture parameters of composites with a brittle matrix is essential for the quantification of their resistance to crack initiation and growth, and also for the specification of material model parameters employed for the simulation of the quasi-brittle behavior of structures made from this type of composite. Therefore, the main target of this paper is to quantify the mechanical fracture parameters of alkali-activated slag composites with steel microfibers and the contribution of the matrix to their fracture response. The first alkali-activated slag composite was a reference version without fibers; the others incorporated steel microfibers amounting to 5, 10, 15 and 20% by weight of the slag. Prism specimens with an initial central edge notch were used to perform the three-point bending fracture tests. Load vs. displacement (deflection at midspan) and load vs. crack mouth opening displacement diagrams were recorded during the fracture tests. The obtained diagrams were employed as inputs for parameter identification, the aim of which was to transfer the fracture test response data to the desired material parameters. Values were also determined for fracture parameters using the effective crack model, work-of-fracture method and double-K fracture model. All investigated mechanical fracture parameters were improved by the addition of steel microfibers to the alkali-activated matrix. Based on the obtained results, the addition of 10 to 15% of microfibers by weight is optimal from the point of view of the enhancement of the fracture parameters of alkali-activated slag composite. Full article
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Open AccessArticle
Experimental Study on Mechanical Properties and Fractal Dimension of Pore Structure of Basalt–Polypropylene Fiber-Reinforced Concrete
Appl. Sci. 2019, 9(8), 1602; https://doi.org/10.3390/app9081602 - 17 Apr 2019
Cited by 8
Abstract
This study investigates the effects of basalt–polypropylene fibers on the compressive strength and splitting tensile strength of concrete and calculates the fractal dimension of the pore structure of concrete by using a fractal model based on the optical method. Test results reveal that [...] Read more.
This study investigates the effects of basalt–polypropylene fibers on the compressive strength and splitting tensile strength of concrete and calculates the fractal dimension of the pore structure of concrete by using a fractal model based on the optical method. Test results reveal that hybrid fibers can improve the compressive strength and splitting tensile strength of concrete, and the synergistic effect of the hybrid fibers is strongest when the contents of basalt fiber (BF) and polypropylene fiber (PF) are 0.05% each, and that the maximum increments in compressive strength and splitting tensile strength are 5.06% and 9.56%, respectively. The effect of hybrid fibers on splitting tensile strength is greater than on compressive strength. However, hybrid fibers have adverse effects on mechanical properties when the fiber content is too high. The pore structure of basalt–polypropylene fiber-reinforced concrete (BPFRC) exhibits obvious fractal characteristics, and the fractal dimension is calculated to be in the range of 2.297–2.482. The fractal dimension has a strong correlation with the air content and spacing factor: the air content decreases significantly whereas the spacing factor increases with increasing fractal dimension. In addition, the fractal dimension also has a strong positive correlation with compressive strength and splitting tensile strength. Therefore, the fractal dimension of the pore structure can be used to evaluate the microscopic pore structure of concrete and can also reflect the influence of the complexity of the pore structure on the macroscopic mechanical properties of concrete. Full article
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Review

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Open AccessFeature PaperReview
A Critical Review on the Influence of Fine Recycled Aggregates on Technical Performance, Environmental Impact and Cost of Concrete
Appl. Sci. 2020, 10(3), 1018; https://doi.org/10.3390/app10031018 - 04 Feb 2020
Cited by 1
Abstract
The aim of this critical review is to show the applicability of recycled fine aggregates (RFA) in concrete regarding technical performance, environmental impact, energy consumption and cost. It is not possible to judge the performance of concrete by considering one dimension. Thus, this [...] Read more.
The aim of this critical review is to show the applicability of recycled fine aggregates (RFA) in concrete regarding technical performance, environmental impact, energy consumption and cost. It is not possible to judge the performance of concrete by considering one dimension. Thus, this study focussed on the fresh and hardened (e.g., mechanical and durability) properties and environmental and economic life cycle assessment of concrete. Most literature investigated showed that any addition of recycled fine aggregates from construction and demolition waste as a replacement for natural fine aggregates proves detrimental to the functional properties (quality) of the resulting concrete. However, the incorporation of recycled fine aggregates in concrete was proven to enhance the environmental and economic performance. In this study, an extensive literature review based multi criteria decision making analysis framework was made to evaluate the effect of RFA on functional, environmental, and economic parameters of concrete. The results show that sustainability of RFA based concrete is very sensitive to transportation distances. Several scenarios for the transportation distances of natural and recycled fine aggregates and their results show that only if the transportation distance of the natural aggregates is more than double that of RFA, e the RFA based concrete alternatives would be considered as more sustainable. Full article
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Open AccessReview
Natural Kenaf Fiber and LC3 Binder for Sustainable Fiber-Reinforced Cementitious Composite: A Review
Appl. Sci. 2020, 10(1), 357; https://doi.org/10.3390/app10010357 - 03 Jan 2020
Cited by 2
Abstract
Low impact on the environment and low cost are the key drivers for today’s technology uptake. There are many concerns for cement production in terms of negative environmental impact due to greenhouse gas (GHG) emission, deficiency of raw materials, as well as high [...] Read more.
Low impact on the environment and low cost are the key drivers for today’s technology uptake. There are many concerns for cement production in terms of negative environmental impact due to greenhouse gas (GHG) emission, deficiency of raw materials, as well as high energy consumption. Replacement of the cement by appropriate additives known as supplementary cementitious materials (SCMs) could result in reduction in GHG emission. Limestone-calcined clay cement (LC3) is a promising binder in the concrete sector for its improvements to environmental impact, durability, and mechanical properties. On the other hand, the advantages of fiber-reinforced concrete such as improved ductility, versatility, and durability have resulted in increasing demand for this type of concrete and introduction of new standards for considering the mechanical properties of fibers in structural design. Thus, using natural fibers instead of synthetic fibers can be another step toward the sustainability of the concrete industry, which is facing increasing demand for cement-based materials. This review studies the potential of natural Kenaf fiber-reinforced concrete containing LC3 binder as a step toward green cementitious composite. While studies show that energy consumption and GHG emission can be reduced and there is a significant potential to enhance mechanical and durability properties of concrete using this composition, adjustment of the mix design, assessing the long-term performance and standardization, are the next steps for the use of the material in practice. Full article
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Open AccessReview
A Systematic Review of the Discrepancies in Life Cycle Assessments of Green Concrete
Appl. Sci. 2019, 9(22), 4803; https://doi.org/10.3390/app9224803 - 10 Nov 2019
Cited by 2
Abstract
It is challenging to measure the environmental impact of concrete with the absence of a consensus on a standardized methodology for life cycle assessment (LCA). Consequently, the values communicated in the literature for “green” concrete alternatives vary widely between 84 and 612 kg [...] Read more.
It is challenging to measure the environmental impact of concrete with the absence of a consensus on a standardized methodology for life cycle assessment (LCA). Consequently, the values communicated in the literature for “green” concrete alternatives vary widely between 84 and 612 kg eq CO2/m3. This does not provide enough evidence regarding the acclaimed environmental benefits compared to ordinary Portland cement concrete knowing that the average for the latter was concluded in this study to be around 370 kg eq CO2/m3. Thus, the purpose of this study was to survey the literature on concrete LCAs in an attempt to identify the potential sources of discrepancies and propose a potential solution. This was done through examining 146 papers systematically and attributing the sources of error to the four stages of an LCA: scope definition, inventory data, impact assessment and results interpretations. The main findings showed that there are 13 main sources of discrepancies in a concrete LCA that contribute to the incompatibility between the results. These sources varied between (i) user-based choices such as depending on a cradle-to-gate scope, selecting a basic volume-based functional unit and ignoring the impact allocation and (ii) intrinsic uncertainty in some of the elements, such as the means of transportation, the expected service life and fluctuations in market prices. The former affects the reliability of a study, and hence, a concrete LCA methodology should not allow for any of the uncertainties. On the other hand, the latter affects the degree of uncertainty of the final outcome, and hence, we recommended conducting scenario analyses and communicating the aggregated uncertainty through the selected indicators. Full article
(This article belongs to the Special Issue Low Binder Concrete and Mortars) Printed Edition available
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Open AccessReview
Crossover Effect in Cement-Based Materials: A Review
Appl. Sci. 2019, 9(14), 2776; https://doi.org/10.3390/app9142776 - 10 Jul 2019
Cited by 2
Abstract
Cement-based materials (CBMs) such as pastes, mortars and concretes are the most frequently used building materials in the present construction industry. Cement hydration, along with the resulting compressive strength in these materials, is dependent on curing temperature, methods and duration. A concrete subjected [...] Read more.
Cement-based materials (CBMs) such as pastes, mortars and concretes are the most frequently used building materials in the present construction industry. Cement hydration, along with the resulting compressive strength in these materials, is dependent on curing temperature, methods and duration. A concrete subjected to an initial higher curing temperature undergoes accelerated hydration by resulting in non-uniform scattering of the hydration products and consequently creating a great porosity at later ages. This phenomenon is called crossover effect (COE). The COE may occur even at early ages between seven to 10 days for Portland cements with various mineral compositions. Compressive strength and other mechanical properties are important for the long life of concrete structures, so any reduction in these properties is of great concern to engineers. This study aims to review existing information on COE phenomenon in CBMs and provide recommendations for future research. Full article
(This article belongs to the Special Issue Low Binder Concrete and Mortars) Printed Edition available
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