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2 pages, 194 KiB

Open AccessEditorial

Sustainable Composites with Solid Waste Materials

by Edyta Pawluczuk, Iwona Skoczko and Enrique Fernández Ledesma

Crystals 2022, 12(3), 411; https://doi.org/10.3390/cryst12030411 - 17 Mar 2022

Viewed by 1086

Abstract

This Special Issue on “Sustainable Composites with Solid Waste Materials” is a collection of 15 original articles (including one review paper) dedicated to theoretical and experimental research works, providing new insights and practical findings in the field of waste-related topics [...] Full article

(This article belongs to the Special Issue Sustainable Composites with Solid Waste Materials)

Research

Jump to: Editorial, Review

13 pages, 1984 KiB

Open AccessArticle

Improving the Performance of Mortars Made from Recycled Aggregates by the Addition of Zeolitised Cineritic Tuff

by Domingo A. Martín, Jorge L. Costafreda, Jorge L. Costafreda, Jr. and Leticia Presa

Crystals 2022, 12(1), 77; https://doi.org/10.3390/cryst12010077 - 06 Jan 2022

Cited by 3 | Viewed by 1339

Abstract

Metropolitan construction and demolition waste (CDW) is currently an important source of recycled materials that, despite having completed their useful life cycle, can be reincorporated into the circular economy process (CEP); however, the recycling process is very selective, and waste material is not [...] Read more.

Metropolitan construction and demolition waste (CDW) is currently an important source of recycled materials that, despite having completed their useful life cycle, can be reincorporated into the circular economy process (CEP); however, the recycling process is very selective, and waste material is not always fully satisfactory due to the intrinsic nature of the waste. This work aims to demonstrate and establish how to increase the effectiveness of the construction and demolition waste in more resistant mortars, by mixing it with zeolitised cinerite tuff (ZCT) at varying normalised proportions. To attain the objectives of this research, a series of tests were done: First, a chemical, physical and mineralogical characterisation of the CDW and the ZCT through XRF, XRD, SEM and granulometric methods. Second, a technological test was made to determine the mechanical strength at 7, 28 and 90 days of specimens made with Portland cement (PC) and mixtures of PC/CDW, PC/ZCT, and PC/CDW-ZCT. The results obtained through the characterisation methods showed that the sample of construction and demolition waste consisted of the main phase made of portlandite and tobermorite, and by a secondary phase consisting of quartz, ettringite and calcite; whereas the ZCT has a main phase of mordenite and a secondary phase of smectite (montmorillonite), amorphous materials consisting of devitrified volcanic glass, quartz and plagioclase. Mechanical strength tests established that specimens made with PC/CDW mixtures have very discreet compressive strength values up to 44 MPa at 90 days, whereas specimens made with PC/ZCT mixtures achieved a remarkably high mechanical strength consisting of 68.5 MPa. However, the most interesting conclusion in this research is the good result obtained in mechanical strength of the specimens made up of mixtures of PC/CDW-ZCT, which increased from 52.5 to 62 MPa at 90 days of curing; this fact establishes the positive influence of ZCT on waste in the mortar mixtures, which permits the authors to establish that the objective of the work has been fulfilled. Finally, it can be argued that the results obtained in this research could contribute to more effective use of construction and demolition waste in metropolitan areas. Full article

(This article belongs to the Special Issue Sustainable Composites with Solid Waste Materials)

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13 pages, 2775 KiB

Open AccessArticle

Effect of the Composition of Mixed Recycled Aggregates on Physical–Mechanical Properties

by Antonio López-Uceda, Enrique Fernández-Ledesma, Lorenzo Salas-Morera, José Ramón Jiménez and David Suescum-Morales

Crystals 2021, 11(12), 1518; https://doi.org/10.3390/cryst11121518 - 05 Dec 2021

Cited by 6 | Viewed by 1921

Abstract

Recycled aggregates (RA) from construction and demolition waste are an alternative to natural aggregates in the construction sector. They are usually classified according to their composition. The main constituent materials are separated into the following categories: unbound natural aggregates, ceramic particles, cementitious particles, [...] Read more.

Recycled aggregates (RA) from construction and demolition waste are an alternative to natural aggregates in the construction sector. They are usually classified according to their composition. The main constituent materials are separated into the following categories: unbound natural aggregates, ceramic particles, cementitious particles, bituminous materials, and other materials considered impurities, such as glass, plastic, wood, or gypsum. In this research, a large number of samples of RA were collected from three different recycling plants and their properties were studied. After that, 35 samples were selected randomly, and their RA constituents were separated under laboratory conditions. Cementitious particles were differentiated into two subcategories: masonry mortar and concrete particles. Subsequently, their physical–mechanical properties were measured. The statistical analysis carried out exhibited that the constituents had a statistically significant influence on the physical–mechanical properties studied. Specifically, masonry mortar particles had higher water absorption and worse mechanical properties than concrete and ceramic particles. Secondly, multiple regression models were performed to predict the physical–mechanical properties of RA from their composition since mean absolute percentage error (MAPE) ranged between 0.9% and 8.6%. The differentiation in the subcategories of concrete and masonry mortar particles in compositional testing is useful for predicting the physical–mechanical properties of RA. Full article

(This article belongs to the Special Issue Sustainable Composites with Solid Waste Materials)

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15 pages, 7902 KiB

Open AccessArticle

Fabrication of Metal (Cu and Cr) Incorporated Nickel Oxide Films for Electrochemical Oxidation of Methanol

by Rimsha Liaqat, Muhammad Adil Mansoor, Javed Iqbal, Asim Jilani, Sehar Shakir, Abul Kalam and S. Wageh

Crystals 2021, 11(11), 1398; https://doi.org/10.3390/cryst11111398 - 16 Nov 2021

Cited by 16 | Viewed by 2227

Abstract

Methanol electrochemical oxidation in a direct methanol fuel cell (DMFC) is considered to be an efficient pathway for generating renewable energy with low pollutant emissions. NiO−CuO and Ni_0.95Cr_0.05O_2+δ thin films were synthesized using a simple dip-coating method and [...] Read more.

Methanol electrochemical oxidation in a direct methanol fuel cell (DMFC) is considered to be an efficient pathway for generating renewable energy with low pollutant emissions. NiO−CuO and Ni_0.95Cr_0.05O_2+δ thin films were synthesized using a simple dip-coating method and tested for the electro-oxidation of methanol. These synthesized electrocatalysts were characterized by X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), and Raman spectroscopy. Different electrochemical techniques were used to investigate the catalytic activity of these prepared electrocatalysts for methanol oxidation, including linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CA). In the presence of 0.3 M methanol, the current densities of NiO−CuO and Ni_0.95Cr_0.05O_2+δ thin films were found to be 12.2 mA·cm⁻² and 6.5 mA·cm⁻², respectively. The enhanced catalytic activity of NiO−CuO and Ni_0.95Cr_0.05O_2+δ thin films may be a result of the synergistic effect between different metal oxides. The Chronoamperometry (CA) results of the mixed metal oxide thin films confirmed their stability in basic media. Furthermore, the findings of electrochemical impedance spectroscopy (EIS) of mixed metal oxide thin films demonstrated a lower charge transfer resistance as compared to the pure NiO, CuO, and Cr₂O₃ thin films. Full article

(This article belongs to the Special Issue Sustainable Composites with Solid Waste Materials)

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17 pages, 2057 KiB

Open AccessArticle

A Taguchi Approach for Optimizing Design Mixture of Geopolymer Concrete Incorporating Fly Ash, Ground Granulated Blast Furnace Slag and Silica Fume

by Sundaravadivelu Karthik and Kaliyaperumal Saravana Raja Mohan

Crystals 2021, 11(11), 1279; https://doi.org/10.3390/cryst11111279 - 22 Oct 2021

Cited by 25 | Viewed by 5707

Abstract

In recent decades, geopolymer concrete (GPC) has been extensively researched as a potential substitute sustainable building material that may reduce CO₂ emissions due to its utilization of industrial by-products. Fly ash (FA) and ground-granulated blast-furnace slag (GGBFS) are preferred geopolymer raw materials [...] Read more.

In recent decades, geopolymer concrete (GPC) has been extensively researched as a potential substitute sustainable building material that may reduce CO₂ emissions due to its utilization of industrial by-products. Fly ash (FA) and ground-granulated blast-furnace slag (GGBFS) are preferred geopolymer raw materials due to their obtainability and high alumina and silica concentrations. GGBFS-FA based GPC offers a clean and sustainable development technology alternative. In this study, the Taguchi method was used to optimize the mixed proportions of geopolymer concrete to achieve desired strength criteria. Four factors and four levels were considered: binder content, including four combinations of FA and GGFBS dosage, dosage of superplasticizer (0.5, 1.0, 1.5 and 2%), Na₂SiO₃/NaOH ratio (1.5, 2.0, 2.5 and 3), and molarity (6, 8, 10 and 12). Using these ingredients and factors, the effect of compressive strength was examined. The Taguchi approach using an L16 orthogonal array was employed to find the optimum condition of every factor while limiting the number of experiments. The findings indicated that the optimum synthesis conditions for maximum compressive strength obtained from the binder comprised 45% of FA, 45% of GGBFS and 10% of silica fume, 1.5% dosage of superplasticizer, Na₂SiO₃/NaOH ratio = 1.5, and 12 molar contents. Full article

(This article belongs to the Special Issue Sustainable Composites with Solid Waste Materials)

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20 pages, 2028 KiB

Open AccessArticle

Research Summary on the Processing, Mechanical and Tribological Properties of Aluminium Matrix Composites as Effected by Fly Ash Reinforcement

by Alaa Mohammed Razzaq, Dayang Laila Majid, Uday M. Basheer and Hakim S. Sultan Aljibori

Crystals 2021, 11(10), 1212; https://doi.org/10.3390/cryst11101212 - 08 Oct 2021

Cited by 12 | Viewed by 2705

Abstract

Fly ash is the main waste as a result of combustion in coal fired power plants. It represents about 40% of the wastes of coal combustion products (fly ash, boiler ash, flue gas desulphurization gypsum and bottom ash). Currently, coal waste is not [...] Read more.

Fly ash is the main waste as a result of combustion in coal fired power plants. It represents about 40% of the wastes of coal combustion products (fly ash, boiler ash, flue gas desulphurization gypsum and bottom ash). Currently, coal waste is not fully utilized and waste disposal remains a serious concern despite tremendous global efforts in reducing fossil fuel dependency and shifting to sustainable energy sources. Owing to that, employment of fly ash as reinforcement particles in metallic matrix composites are gaining momentum as part of recycling effort and also as a means to improve the specifications of the materials that are added to it to form composite materials. Many studies have been done on fly ash to study composite materials wear characteristics including the effects of fly ash content, applied load, and sliding velocity. Here, particular attention is given to studies carried out on the influence FA content on physical, mechanical, and the thermal behavior of Aluminium-FA composites. Considerable changes in these properties are seen by fly ash refinement with limited size and weight fraction. The advantage of fly ash addition results in low density of composites materials, improvement of strength, and hardness. It further reduces the thermal expansion coefficient and improve wear resistance. Full article

(This article belongs to the Special Issue Sustainable Composites with Solid Waste Materials)

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10 pages, 2296 KiB

Open AccessArticle

Effect of Fly Ash Belite Cement on Hydration Performance of Portland Cement

by Yongfan Gong, Jianming Yang, Haifeng Sun and Fei Xu

Crystals 2021, 11(7), 740; https://doi.org/10.3390/cryst11070740 - 25 Jun 2021

Cited by 8 | Viewed by 1904

Abstract

Fly ash belite cement is a green, low carbon cementitious material, mainly composed of hydraulic minerals of dicalcium silicate and calcium aluminate. In this study, we used fly ash belite cement to control the setting time, hydration heat, strength, composition and microstructure of [...] Read more.

Fly ash belite cement is a green, low carbon cementitious material, mainly composed of hydraulic minerals of dicalcium silicate and calcium aluminate. In this study, we used fly ash belite cement to control the setting time, hydration heat, strength, composition and microstructure of hydration products in Portland cement. Results showed that incorporating fly ash belite cement into Portland cement can shorten the setting time, accelerate hydration reaction speed, enhance early hydration heat release rate of silicate minerals and reduce total hydration heat. Moreover, replacing composite cement with 30% FABC causes the 90 d compressive strength of pastes and mortars to reach 107 and 46.2 MPa, respectively. The mechanical properties can meet the requirements of P·F 42.5 cement. During the hydration reaction process, clinker and Portland cement have a synergistic hydration effect. Notably, hydration of fly ash belite cement promotes the formation of C-S-H gel, Ettringite and calcium hydroxide, thereby significantly enhancing long-term strength. With the increase of FABC contents, the long-term strength would be improved with the densification of hydration products. The porosity has a great influence on the strength, and the high porosity was the main cause of the low early strength of FABC pastes. FABC and its composite cement show promise for mass concrete applications and can be applied as a setting agent for Portland cement. Full article

(This article belongs to the Special Issue Sustainable Composites with Solid Waste Materials)

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13 pages, 7347 KiB

Open AccessArticle

Mechanical and Durability Properties of Aerated Concrete Incorporating Rice Husk Ash (RHA) as Partial Replacement of Cement

by Tariq Ali, Abdullah Saand, Daddan Khan Bangwar, Abdul Salam Buller and Zaheer Ahmed

Crystals 2021, 11(6), 604; https://doi.org/10.3390/cryst11060604 - 27 May 2021

Cited by 29 | Viewed by 4060

Abstract

In today’s world, the implementation of industrial ecology for sustainable industrial development is a common practice in the field of engineering. This practice promotes the recycling of by-product wastes. One of those by-product wastes is rice husk ash. This paper describes an investigation [...] Read more.

In today’s world, the implementation of industrial ecology for sustainable industrial development is a common practice in the field of engineering. This practice promotes the recycling of by-product wastes. One of those by-product wastes is rice husk ash. This paper describes an investigation into the effect of rice husk ash (RHA) as a partial replacement for cement, to produce lightweight, aerated concrete. Type I Portland cement, fine aggregate, and aluminum powder as an aerating agent were used in this study. The RHA was used in different replacement levels, i.e., RHA was used to replace cement at 0%, 2.5%, 5%, 7.5%, 10%, 12.5% and 15% by weight. Aluminum powder was added during mixing at 0.5% by weight of binder to obtain lightweight, aerated concrete. Test results are presented in terms of physical, mechanical, and durability aspects that include density, compressive strength, split tensile strength, and flexural strength of concrete cured at different curing regimes, i.e., 3, 7, 28, and 90 days along with corrosion analysis, and sulphate attack at 28 days of curing. The test results show that using 10% RHA as a partial replacement of cement in aerated concrete is beneficial in triggering the strength and durability properties of concrete. Full article

(This article belongs to the Special Issue Sustainable Composites with Solid Waste Materials)

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13 pages, 2327 KiB

Open AccessArticle

Oxidation of Cr(III) to Cr(VI) and Production of Mn(II) by Synthetic Manganese(IV) Oxide

by Kaiyin Chen, Lauren Bocknek and Bruce Manning

Crystals 2021, 11(4), 443; https://doi.org/10.3390/cryst11040443 - 19 Apr 2021

Cited by 15 | Viewed by 3067

Abstract

The heterogeneous oxidation of Cr(III) to Cr(VI), a toxic inorganic anion, by a synthetic birnessite (δ-MnO₂) was investigated in batch reactions using a combination of analytical techniques including UV–Vis spectrophotometry, microwave plasma–atomic emission spectrometry, X-ray diffraction (XRD), X-ray photoelectron [...] Read more.

The heterogeneous oxidation of Cr(III) to Cr(VI), a toxic inorganic anion, by a synthetic birnessite (δ-MnO₂) was investigated in batch reactions using a combination of analytical techniques including UV–Vis spectrophotometry, microwave plasma–atomic emission spectrometry, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR), to evaluate both the solution speciation of Cr(III)/Cr(VI) and the surface of the reacted δ-MnO₂. The formation of dissolved Mn(II) was determined during the batch reactions to evaluate the extent and stoichiometry of the Cr(III) oxidation reaction. A stoichiometric 3:2 Mn(II):Cr(VI) molar relationship was observed in the reaction products. The reductive dissolution of the δ-MnO₂ by Cr(III) resulted in a surface alteration from the conversion of Mn(IV) oxide to reduced Mn(II) and Mn(III) hydroxides. The results of this investigation show that naturally occurring Cr(III) will readily oxidize to Cr(VI) when it comes in contact with MnO_2, forming a highly mobile and toxic groundwater contaminant. Full article

(This article belongs to the Special Issue Sustainable Composites with Solid Waste Materials)

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19 pages, 5761 KiB

Open AccessArticle

Structural Optimization of Steel—Epoxy Asphalt Pavement Based on Orthogonal Design and GA—BP Algorithm

by Xunqian Xu, Yuwen Gu, Wei Huang, Dakai Chen, Chen Zhang and Xiao Yang

Crystals 2021, 11(4), 417; https://doi.org/10.3390/cryst11040417 - 13 Apr 2021

Cited by 12 | Viewed by 1947

Abstract

Fatigue cracks often occur in the deck asphalt pavement of steel bridges at the top of the longitudinal stiffening rib. To prevent this issue, the traditional design strategy of the steel bridge deck asphalt pavement structure was optimized, and a new approach is [...] Read more.

Fatigue cracks often occur in the deck asphalt pavement of steel bridges at the top of the longitudinal stiffening rib. To prevent this issue, the traditional design strategy of the steel bridge deck asphalt pavement structure was optimized, and a new approach is presented. This optimization technique exploits the strength simulation of the steel—epoxy asphalt pavement structure, and the stress concentration location is subsequently determined. A solid model of stress concentration including sensitive areas is then established. We examined the stress maximum point of the asphalt pavement layer at the top of the longitudinal stiffeners and the stress variation of the asphalt pavement layer at the top of the longitudinal stiffeners. To reduce the stress of the top pavement layer of the longitudinal stiffeners, an optimization method that combines orthogonal experimental design, neural network (BP), and genetic algorithm (GA) is presented. A design strategy for the steel—epoxy asphalt pavement structure and GA—BP optimization method was utilized to optimize the structure of the steel—epoxy asphalt pavement for Sutong Yangzi River Bridge. We confirmed that the presented approach improved fatigue reliability and established the efficacy of the design strategy and optimization method. Full article

(This article belongs to the Special Issue Sustainable Composites with Solid Waste Materials)

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14 pages, 4201 KiB

Open AccessArticle

Rheological Behavior of Warm Mix Asphalt Modified with Foaming Process and Surfactant Additive

by Guoyang Lu, Shaowei Zhang, Shaofeng Xu, Niya Dong and Huayang Yu

Crystals 2021, 11(4), 410; https://doi.org/10.3390/cryst11040410 - 12 Apr 2021

Cited by 10 | Viewed by 1906

Abstract

Surfactants are frequently used to improve the engineering performances of foamed bitumen. Additionally, the foaming process can also perform a significant influence on the foam characteristics and rheological properties of foamed bitumen. However, rare research investigates the synergistic effect of both surfactant and [...] Read more.

Surfactants are frequently used to improve the engineering performances of foamed bitumen. Additionally, the foaming process can also perform a significant influence on the foam characteristics and rheological properties of foamed bitumen. However, rare research investigates the synergistic effect of both surfactant and foaming process on the engineering properties of foamed bitumen. To fill the gap, this research investigated the synergistic effect of surfactant and foaming process on the foaming characteristics and rheological properties of foamed bitumen. Based on the experimental results, the synergistic effect shows a significant effect on improving the half-life of foamed bitumen, which reached up to 69 s when 6% foaming Evotherm-DAT content was used. In addition, the foaming temperature also has a significant effect on the foaming characteristics. This study shows that the best foaming conditions can be achieved when the foaming temperature and Evotherm-DAT content are 170 °C and 8%, respectively. Based on the study of synergistic effect, the engineering performances of surfactant foamed bitumen were further characterized in this research, for instance, the enhancement in high-temperature performance and fatigue resistance, and the improvement in workability. Generally, the results of this study have greatly promoted the application of surfactant foam bitumen in the engineering practice. Full article

(This article belongs to the Special Issue Sustainable Composites with Solid Waste Materials)

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19 pages, 2817 KiB

Open AccessArticle

Development of Cold In-Place Recycling with Bitumen Emulsion and Biomass Bottom Ash

by Jorge Suárez-Macías, Juan María Terrones-Saeta, Francisco Javier Iglesias-Godino and Francisco Antonio Corpas-Iglesias

Crystals 2021, 11(4), 384; https://doi.org/10.3390/cryst11040384 - 07 Apr 2021

Cited by 4 | Viewed by 1898

Abstract

Power generation from biomass is one of the most promising energy sources available today. However, this industry has a series of wastes derived from its activity, mainly biomass fly ash and biomass bottom ash. Biomass bottom ash is a waste that has no [...] Read more.

Power generation from biomass is one of the most promising energy sources available today. However, this industry has a series of wastes derived from its activity, mainly biomass fly ash and biomass bottom ash. Biomass bottom ash is a waste that has no current use and, in most cases, is deposited in landfills. In turn, road construction is one of the activities that produces the most pollution, as it requires huge amounts of raw materials. Therefore, this research proposes the use of biomass bottom ashes, in an unaltered form, for the formation of cold in-place recycling with bitumen emulsion. This type of mixture, which is highly sustainable owing to the use of a high percentage of waste, was made with reclaimed asphalt pavement, biomass bottom ash, water, and bitumen emulsion. To this end, the grading curve of the materials was analyzed, different bituminous mixtures were made with varying percentages of emulsion and water, and the mechanical properties of the mixtures were analyzed. At the same time, the same type of mix was made with reclaimed asphalt pavement and commercial limestone aggregate, in order to compare the results. The tests showed a better mechanical behavior of the bituminous mixes made with biomass bottom ash, maintaining physical properties similar to those of conventional mixes. In short, it was confirmed that the production of this type of mix with biomass bottom ash was feasible, creating sustainable materials that reuse currently unused waste and avoid landfill disposal. Full article

(This article belongs to the Special Issue Sustainable Composites with Solid Waste Materials)

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17 pages, 1846 KiB

Open AccessArticle

Eurocode Design of Recycled Aggregate Concrete for Chloride Environments: Stochastic Modeling of Chloride Migration and Reliability-Based Calibration of Cover

by António Albuquerque, João Nuno Pacheco and Jorge de Brito

Crystals 2021, 11(3), 284; https://doi.org/10.3390/cryst11030284 - 13 Mar 2021

Cited by 7 | Viewed by 1986

Abstract

Recycled aggregate concrete is a solution used to minimize the environmental impact of the concrete industry. Notwithstanding research worldwide validating structural applications of recycled aggregate concrete, specific design guidelines are lacking and are needed to address reservations of construction agents. Design guidelines should [...] Read more.

Recycled aggregate concrete is a solution used to minimize the environmental impact of the concrete industry. Notwithstanding research worldwide validating structural applications of recycled aggregate concrete, specific design guidelines are lacking and are needed to address reservations of construction agents. Design guidelines should be based on reliability concepts, including the stochastic modeling of material properties and the calibration of design clauses through reliability methods. This paper concerns the concrete cover design of recycled aggregate concrete elements exposed to chloride ingress. Only coarse recycled aggregates produced from concrete waste are studied. The paper describes the chloride ingress model of fib Bulletin 34, presents experiments on the chloride ion migration of several analogue natural and recycled aggregate concrete mixes, tackles the stochastic modeling of the chloride migration coefficient, and calibrates concrete cover design for recycled aggregate concrete using reliability methods. The concrete cover design followed the deemed-to-satisfy provisions of Eurocode 2 and EN 206. The case studies used in the reliability analyses covered several design situations. A 5 mm increase of concrete cover is recommended as a simple option that ensures that the probability of depassivation due to chloride ingress on recycled aggregate concrete elements is equivalent to that for analogue natural aggregate concrete elements. Full article

(This article belongs to the Special Issue Sustainable Composites with Solid Waste Materials)

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21 pages, 2067 KiB

Open AccessArticle

Effect of Biomass Fly Ash on Fresh and Hardened Properties of High Volume Fly Ash Mortars

by Elisabete R. Teixeira, Aires Camões, Fernando G. Branco and José Campos Matos

Crystals 2021, 11(3), 233; https://doi.org/10.3390/cryst11030233 - 26 Feb 2021

Cited by 14 | Viewed by 2512

Abstract

The objective of this work was to assess the use of biomass fly ash (BFA) as cement replacement material or as an alkalinity source in high volume fly ash mortar and concrete. Mortar formulations were prepared with different types of cement replacement: fly [...] Read more.

The objective of this work was to assess the use of biomass fly ash (BFA) as cement replacement material or as an alkalinity source in high volume fly ash mortar and concrete. Mortar formulations were prepared with different types of cement replacement: fly ash from thermal power plants, BFA, a blend of two pozzolans, and small amounts of BFA or/and hydrated lime (HL). Mortar formulations were tested both in the fresh and hardened state. The replacement of cement by the two fly ashes led to a decrease in the mechanical strength. The best strength values were obtained when higher HL content was introduced in mortars, however, mortars with the lower BFA content presented the best results for the majority of the tests. In general, BFA has a similar effect on cementitious mortars to coal fly ash, having good performance as cement replacement. Full article

(This article belongs to the Special Issue Sustainable Composites with Solid Waste Materials)

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29 pages, 16137 KiB

Open AccessArticle

Characterisation and Life Cycle Assessment of Pervious Concrete with Recycled Concrete Aggregates

by Adilson C. Paula Junior, Cláudia Jacinto, Thaís M. Oliveira, Antonio E. Polisseni, Fabio M. Brum, Elisabete R. Teixeira and Ricardo Mateus

Crystals 2021, 11(2), 209; https://doi.org/10.3390/cryst11020209 - 20 Feb 2021

Cited by 14 | Viewed by 3347

Abstract

The search for environmental preservation and conservation of natural resources gives rise to new concepts and viable technical solutions on the path to sustainable development. In this context, this study’s main objective is to analyse the influence of recycled concrete aggregates (RCAs) on [...] Read more.

The search for environmental preservation and conservation of natural resources gives rise to new concepts and viable technical solutions on the path to sustainable development. In this context, this study’s main objective is to analyse the influence of recycled concrete aggregates (RCAs) on the development of pervious concrete, whose use as a floor covering represents an excellent device to mitigate the urban soil sealing phenomena. For this, mechanical and hydraulic tests were carried out, in addition to microstructural analyses and the assessment of its environmental performance. The results obtained were compared to reference studies also involving the incorporation of recycled aggregates. A pilot-scale case study was conducted, involving a parking space lined with pervious concrete moulded “in situ”. In laboratory tests, permeability coefficients and mechanical strengths compatible with the literature and above the normative limit for light traffic were found. The case study demonstrated higher permeability than in the laboratory, but the flexural strength was lower, being indicated only for pedestrian traffic. The environmental assessment showed that the RCA represents a positive contribution to the environmental performance of pervious concrete. Still, attention should be given to the recycled aggregate transport distance between the concrete plant and the RCA treatment plant. Full article

(This article belongs to the Special Issue Sustainable Composites with Solid Waste Materials)

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Jump to: Editorial, Research

20 pages, 3412 KiB

Open AccessReview

Low-Carbon Sustainable Composites from Waste Phosphogypsum and Their Environmental Impacts

by Kai Ren, Na Cui, Shuyuan Zhao, Kai Zheng, Xia Ji, Lichao Feng, Xin Cheng and Ning Xie

Crystals 2021, 11(7), 719; https://doi.org/10.3390/cryst11070719 - 22 Jun 2021

Cited by 16 | Viewed by 2943

Abstract

Phosphogypsum (PG) is an industrial waste from the production of phosphoric acid and phosphate fertilizer. Disposal and landfill of PG pose significant environmental problems due to its hazardous components. Although many researchers have explored the possibility of PG recycling, challenges still exist before [...] Read more.

Phosphogypsum (PG) is an industrial waste from the production of phosphoric acid and phosphate fertilizer. Disposal and landfill of PG pose significant environmental problems due to its hazardous components. Although many researchers have explored the possibility of PG recycling, challenges still exist before it can be high-effectively reused. In particular, a great deal of recent attention has been attracted to explore using PG as raw material to manufacture sustainable composites. The impurities movement, recycling efficiency, and environmental impacts have to be further investigated. This review article summarized the state of the art of the purification process, application areas, and the environmental impacts of PG waste. The main challenges and potential application approaches were discussed. This article is focused on reviewing the details of the PG reusing which benefits the readers on learning the knowledge from previous efforts. The main challenges of reusing PG were discussed from the chemical, physical, and materials perspectives. Full article

(This article belongs to the Special Issue Sustainable Composites with Solid Waste Materials)

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