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Applied Sciences
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Recycling Waste in Construction Materials
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Recycling Waste in Construction Materials

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

Deadline for manuscript submissions: closed (30 November 2020) | Viewed by 65719

Special Issue Editors

Dr. Jessica Giró Paloma

E-Mail Website
Guest Editor
Departament de Ciència de Materials i Química Física, Universitat de Barcelona, C/Martí i Franquès 1, 08028 Barcelona, Spain
Interests: materials in the construction field; recycling; valorization; by-products; revalorization and environment; inertization; MSW usage for construction aggregates; thermal and acoustic insulation; alternative binders; leaching tests; materials for the improvement of energy efficiency; thermal energy storage; industrial processes; pilot plants; optimization processes, circular economy; alkali-activated materials; magnesium phosphate cements; pozzolanic reaction; ceramic materials; lightweight materials
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Joan Formosa Mitjans

E-Mail Website
Guest Editor
Departament de Ciència de Materials i Química Física, Universitat de Barcelona, C/Martí i Franquès 1, 08028 Barcelona, Spain
Interests: sustainable construction materials; recycling and beneficiation of by-products in construction application materials; cement; supplementary cementitious materials (SCMs) and concrete; advanced materials for energy storage; green buildings; repairing materials for structural concrete; magnesium phosphate cements; alkali-activated materials and cements; waste materials for construction; fireproof materials; fire behavior; research in municipal solid waste management; environmental and mechanical behavior; environmental impact assessment; alternative binders
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Recycling is a key part of decreasing present-day waste. The reduction, reuse, and recycling of waste maintains an ecological economy by substituting crude material contributions to, and diverting waste yields out of, the monetary framework.

Due to the growing amount of residual waste, it is encouraged to apply a waste hierarchy to provide viable alternatives in managing waste and efficiently using resources to move towards a low-carbon economy. This includes the development of sustainable alternatives that can reuse different kinds of waste by formulating them into secondary materials.

Human activities, such as construction, impact the environment. Recycling waste reduces disposal costs and carbon emissions. It also helps to comply with environmental legislation and landfill restrictions. In this sense, it is important to find appropriate alternatives to ordinary Portland cement (OPC) in the field of construction.

This “Recycling Waste in Construction Materials” Special Issue solicits contributions on some of the following areas and subjects:

  • Sustainable development and production considering management, instruments, methods, and processes
  • Innovation processes and methodologies related to improving the productivity of waste/by-products and resource management practices
  • Life cycle assessment and management of waste/by-products to improve their efficiency and productivity
  • Construction and demolition waste (CDW). Properties and applications of recycled aggregates from construction and demolition waste
  • Development of construction material from nontraditional concrete including waste/by-products
  • Geopolymers and alkali-activated materials
  • Magnesium phosphate cements
  • Repairing materials
  • Lightweight materials and aggregates
  • Reliability studies of formulations including waste/by-products
  • Aggressive environments: damage and fracture
  • Long-term behavior
  • Environmental assessments of construction materials including waste/by-products
  • Recycling and reuse
  • Landfill disposal
  • Economic analysis

Dr. Jessica Giró Paloma
Dr. Joan Formosa Mitjans
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Applied Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • construction materials
  • waste recycling and management
  • demolition wastes
  • secondary materials
  • aggregates
  • reuse
  • life cycle assessment
  • landfill
  • profit and revaluation of industrial wastes and by-products
  • revalorization
  • valorization
  • inertization
  • environment

Published Papers (17 papers)

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17 pages, 3145 KiB  
Article
Coal Fly Ash–Clay Based Geopolymer-Incorporating Electric Arc Furnace Dust (EAFD): Leaching Behavior and Geochemical Modeling
by Eva Cifrian, Juan Dacuba, Tamara Llano, María del Carmen Díaz-Fernández and Ana Andrés
Appl. Sci. 2021, 11(2), 810; https://doi.org/10.3390/app11020810 - 16 Jan 2021
Cited by 9 | Viewed by 2265
Abstract
The recent recovery processes of electric arc furnace dust (EAFD) include stabilization within materials with potential uses in the construction sector. The stabilization of EAFD by alkaline activation of different alumina-silicates, resulting in low-cost and environmentally friendly materials. The leaching standards within the [...] Read more.
The recent recovery processes of electric arc furnace dust (EAFD) include stabilization within materials with potential uses in the construction sector. The stabilization of EAFD by alkaline activation of different alumina-silicates, resulting in low-cost and environmentally friendly materials. The leaching standards within the different European regulations allow evaluating waste materials and products. This work aims to study the introduction of EAFD in FA–clay geopolymers, assessing the environmental and geochemical behavior in two different scenarios, disposal, and utilization. For it, the compliance equilibrium-based batch test (EN 12457-2) and pH dependence test (EN 14429) have been used. The dosages of EAFD in the geopolymeric matrix are 5% to 20% with curing temperatures of 75 °C and 225 °C. The introduction of EAFD favors the development of the flexural strength. From the environmental point of view, metals related to EAFD, such as Zn, Pb, or Cu, are retained in the matrix. While As or Se, comes mainly from clay, present a high concentration. Therefore, the role of clay should be analyzed in future research. As expected by the high iron content in the EAFD, the iron complexes on the surface of the material are responsible for immobilization of metals in this type of matrix. Full article
(This article belongs to the Special Issue Recycling Waste in Construction Materials)
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14 pages, 3035 KiB  
Article
Sustainable Panels Made with Industrial and Agricultural Waste: Thermal and Environmental Critical Analysis of the Experimental Results
by Paola Ricciardi, Elisa Belloni, Francesca Merli and Cinzia Buratti
Appl. Sci. 2021, 11(2), 494; https://doi.org/10.3390/app11020494 - 06 Jan 2021
Cited by 17 | Viewed by 3298
Abstract
Recycled waste materials obtained from industrial and agricultural processes are becoming promising thermal and acoustic insulating solutions in building applications; their use can play an important role in the environmental impact reduction. The aim of the present paper is the evaluation of the [...] Read more.
Recycled waste materials obtained from industrial and agricultural processes are becoming promising thermal and acoustic insulating solutions in building applications; their use can play an important role in the environmental impact reduction. The aim of the present paper is the evaluation of the thermal performance of recycled waste panels consisting of cork scraps, rice husk, coffee chaff, and end-life granulated tires, glued in different weight ratios and pressed. Six panels obtained from the mixing of these waste materials were fabricated and analyzed. In particular, the scope is the selection of the best compromise solutions from the thermal and environmental points of view. To this aim, thermal resistances were measured in laboratory and a Life Cycle Assessment (LCA) analysis was carried out for each panel; a cross-comparative examination was performed in order to optimize their properties and find the best panels solutions to be assembled in the future. Life Cycle Analysis was carried out in terms of primary Embodied Energy and Greenhouse Gas Emissions, considering a ‘‘cradle-to-gate” approach. The obtained thermal conductivities varied in the 0.055 to 0.135 W/mK range, in the same order of magnitude of many traditional systems. The best thermal results were obtained for the panels made of granulated cork, rice husk, and coffee chaff in this order. The rubber granulate showed higher values of the thermal conductivity (about 0.15 W/mK); a very interesting combined solution was the panel composed of cork (60%), rice husk (20%), and coffee chaff (20%), with a thermal conductivity of 0.08 W/mK and a Global Warming Potential of only 2.6 kg CO2eq/m2. Considering the Embodied Energy (CED), the best solution is a panel composed of 56% of cork and 44% of coffee chaff (minimum CED and thermal conductivity). Full article
(This article belongs to the Special Issue Recycling Waste in Construction Materials)
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15 pages, 2550 KiB  
Article
Eco-Efficient Hybrid Cements: Pozzolanic, Mechanical and Abrasion Properties
by Segundo Shagñay, Leticia Ramón, María Fernández-Álvarez, Asunción Bautista, Francisco Velasco and Manuel Torres-Carrasco
Appl. Sci. 2020, 10(24), 8986; https://doi.org/10.3390/app10248986 - 16 Dec 2020
Cited by 16 | Viewed by 1862
Abstract
One of the most polluting industries is the cement industry and, for this reason, alternative lines of research recommend the use of substitute materials for traditional Portland cement. This study proposes the use of industrial (slag and fly ash) and ceramic wastes for [...] Read more.
One of the most polluting industries is the cement industry and, for this reason, alternative lines of research recommend the use of substitute materials for traditional Portland cement. This study proposes the use of industrial (slag and fly ash) and ceramic wastes for the total or partial replacement of Portland cement in the manufacturing of both alkaline-activated and hybrid cements. To carry out this study and evaluate the behavior of the proposed materials, different mortars were manufactured: Portland cement (CEM I), two alkaline-activated slag systems and six hybrid systems, with an 80–20% waste-to-Portland-cement ratio for all the proposed wastes. An assessment of the pozzolanic activity was carried out for the different materials. The behavior of all the systems regarding mechanical resistance and durability to abrasion was studied. All the proposed materials, especially those with ceramic wastes, showed pozzolanic activity and suitable characteristics for use in the manufacturing of alternative cements. The mortar made of slag activated with waterglass presented the highest mechanical strength and lowest porosity, but the hybrid materials presented competitive results. After being subjected to the Böhme abrasion test, their effectiveness as substitutes for Portland cement is reiterated, some of them improving their durability to wear. Full article
(This article belongs to the Special Issue Recycling Waste in Construction Materials)
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15 pages, 3904 KiB  
Article
Soil Stabilization Using Waste Paper Fly Ash: Precautions for Its Correct Use
by Hani Baloochi, Diego Aponte and Marilda Barra
Appl. Sci. 2020, 10(23), 8750; https://doi.org/10.3390/app10238750 - 07 Dec 2020
Cited by 11 | Viewed by 3439
Abstract
This paper deals with the valorization of waste paper fly ash (WPFA) as a binder for soil stabilization. The mineralogical characterization shows the presence of free lime, as well as some non-reactive and cementitious phases. The hydration of lime is an expansive reaction [...] Read more.
This paper deals with the valorization of waste paper fly ash (WPFA) as a binder for soil stabilization. The mineralogical characterization shows the presence of free lime, as well as some non-reactive and cementitious phases. The hydration of lime is an expansive reaction and can be problematic in soil stabilization. Therefore, to study its effect on stabilized soil, an in-house experimental set-up is proposed to measure the possible expansion. Furthermore, to study the effect of water reduction and delay time on strength, unconfined compressive strength with different mixes is conducted. The obtained results showed that using WPFA causes expansion in stabilized soil, but a delay time of 30 min, after mixing the material with water and then compacting it, can decrease the expansion. Additionally, decreasing the water content by a point of Proctor can be essential for improving the strength in soil samples, even reaching the same strength values as control samples cured at 7 days. Finally, all the results obtained in this study have shown that WPFA is a suitable material for use as a binder for soil stabilization while reducing its optimum water content, adding a proper delay time, and taking into consideration WPFA’s expansive behavior at the moment of its use. Full article
(This article belongs to the Special Issue Recycling Waste in Construction Materials)
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15 pages, 42434 KiB  
Article
Granular Material Development Applied in an Experimental Section for Civil Engineering Purposes
by Jessica Giro-Paloma, Joan Formosa and Josep M. Chimenos
Appl. Sci. 2020, 10(19), 6782; https://doi.org/10.3390/app10196782 - 28 Sep 2020
Cited by 8 | Viewed by 2457
Abstract
In this study, a granular material (GM) derived from wastes generated in waste-to-energy plants was developed. Weathered bottom ash (WBA) and air pollution control (APC) ashes obtained from municipal solid waste incineration (MSWI) were used as raw materials. A mortar (M) with 50 [...] Read more.
In this study, a granular material (GM) derived from wastes generated in waste-to-energy plants was developed. Weathered bottom ash (WBA) and air pollution control (APC) ashes obtained from municipal solid waste incineration (MSWI) were used as raw materials. A mortar (M) with 50 wt. % of APC and 50 wt. % of Ordinary Portland Cement (OPC) CEM-I was prepared. The GM formulation was 20 wt. % M and 80 wt. % WBA. At the laboratory scale, WBA, APC, M, and crushed GM were evaluated by means of dynamic leaching (EN 12457-4) tests, and WBA, M, and crushed GM by percolation column (CEN/TS 16637) tests. The metal(loid)s analyzed were below the non-hazardous limits, regarding the requirement of the metal(loid)s released for waste revalorization. In order to simulate a road subbase real scenario, the crushed GM was tested in an experimental section (10 × 20 × 0.2 m). During a 600-day period, the leachates generated by the percolation of rainwater were collected. This research shows outstanding results regarding the metal(loid)s released for both the “accumulated” and “punctual” leachates collected. An accomplishment in the immobilization of metal(loid)s from APC residues was achieved because of the encapsulation effect of the cement. The GM formulation from both MSWI wastes can be considered an environmentally safe procedure for revalorizing APC residues. Full article
(This article belongs to the Special Issue Recycling Waste in Construction Materials)
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12 pages, 1564 KiB  
Article
An Experimental Study on Alkali Silica Reaction of Concrete Specimen Using Steel Slag as Aggregate
by So Yeong Choi and Eun Ik Yang
Appl. Sci. 2020, 10(19), 6699; https://doi.org/10.3390/app10196699 - 25 Sep 2020
Cited by 8 | Viewed by 2195
Abstract
In this study, the characteristics of the alkali-silica reaction (ASR) expansion of steel slag itself, mortar bars, and concrete specimens using steel slag as aggregate are individually investigated by the expansion test method, to determine if steel slag aggregate in concrete can provide [...] Read more.
In this study, the characteristics of the alkali-silica reaction (ASR) expansion of steel slag itself, mortar bars, and concrete specimens using steel slag as aggregate are individually investigated by the expansion test method, to determine if steel slag aggregate in concrete can provide volume stability. The results show that when steel slag is aged in water for one month, its self-expansibility is below the permitted limit of 1.5% according to the JIS A 5015 standard. The ASR test results show that the ASR expansion of the mortar bars continuously increased with the increase in the test period. However, all mortar bars were below the permitted limit of 0.1% after 14 days according to the ASTM C 1260 standard. In contrast, the ASR expansion of concrete specimens was above the criteria prescribed by the ASTM C 1293 standard. From the results, the expansion of concrete specimens could not be controlled within the permitted limit by the ASTM 1293 criteria, even if the expansivity of steel slag did not exceed the criteria. Meanwhile, considering the crack propagation patterns of the concrete specimens, the cracks due to ASR expansion developed and connected even when the expansion was below the permitted limit. Besides, when mineral admixtures were used as the binder in the concrete specimens, there were discrepancies in the results between the expansion rate and the crack properties, such as maximum length and total crack length. Therefore, to accurately determine the change in volume due to ASR expansion in concrete using steel slag as coarse aggregate, it is necessary to check the crack patterns in addition to evaluating the expansion rate. Full article
(This article belongs to the Special Issue Recycling Waste in Construction Materials)
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13 pages, 5039 KiB  
Article
Using Waste in Producing Bio-Composite Mycelium Bricks
by Jason Maximino C. Ongpeng, Edward Inciong, Vince Sendo, Crizia Soliman and Adrian Siggaoat
Appl. Sci. 2020, 10(15), 5303; https://doi.org/10.3390/app10155303 - 31 Jul 2020
Cited by 34 | Viewed by 11791
Abstract
One of the major causes of an increase in the consumption of resources is the progress of the construction industry. Although it leads to new technologies, it heavily contributes to global warming. In this study, the use of sustainable construction materials from waste [...] Read more.
One of the major causes of an increase in the consumption of resources is the progress of the construction industry. Although it leads to new technologies, it heavily contributes to global warming. In this study, the use of sustainable construction materials from waste in brick production with mycelium as a binder is investigated. The ability of mycelium, the root fibers of fungi, obtained from microorganisms is used as stabilizing and binding material on bricks. Forty-eight brick specimens from six design mixes were produced with a size of 200 mm length × 90 mm width × 60 mm height. The mechanical tests conducted were compressive and flexural strength. The changes in weight were recorded against its age to monitor the progress of mycelium growth inside the brick specimens. From the test, bricks made from sawdust and rice bran with mycelium had an increase of 31.0% to 38.5% in average compressive strength compared to the non-mycelium bricks, respectively. Furthermore, the bricks with mycelium experienced an increase in both flexural strength and midpoint displacement for all types of bricks (rice bran, sawdust, and clay). These mycelium-induced bricks can reduce the use and consumption of traditional construction materials with enhanced mechanical properties. Full article
(This article belongs to the Special Issue Recycling Waste in Construction Materials)
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15 pages, 4189 KiB  
Article
Municipal Solid Waste Incineration Bottom Ash as Sole Precursor in the Alkali-Activated Binder Formulation
by Àlex Maldonado-Alameda, Jessica Giro-Paloma, Anna Alfocea-Roig, Joan Formosa and Josep Maria Chimenos
Appl. Sci. 2020, 10(12), 4129; https://doi.org/10.3390/app10124129 - 16 Jun 2020
Cited by 27 | Viewed by 3165
Abstract
The concern about the large amount of weathered bottom ash (WBA) produced in waste-to-energy plants (WtE) has caused an increased search for alternatives to reduce their environmental impact. The present study aims to provide an added value through the WBA valorization from municipal [...] Read more.
The concern about the large amount of weathered bottom ash (WBA) produced in waste-to-energy plants (WtE) has caused an increased search for alternatives to reduce their environmental impact. The present study aims to provide an added value through the WBA valorization from municipal solid waste incineration (MSWI) for its use as a sole precursor for developing alkali-activated binders (AABs). Alkali-activated weathered bottom ash binders (AA-WBA) were formulated with a liquid-to-solid ratio of 1.0 and using sodium silicate (80 wt.%) and NaOH (20 wt.%) at different concentrations (2, 4, 6, and 8M) as alkali-activator solutions. AA-WBA were cured at room temperature to extend their applicability. The effect of the alkali-activator solution molarity on the final properties of the AA-WBA was evaluated. The physicochemical characterization by XRD, FTIR, and SEM evidenced the presence of the typical phases (calcium silicate hydrate and gehlenite) of C-(A)-S-H gel. Leaching concentrations of As, Cu, and Mo exceed the acceptance in landfills for inert waste, while the leaching concentration of Sb exceeds the one for non-hazardous waste. The structure of the binders depends on the alkalinity of the activator, obtaining better results using NaOH 6M in terms of microstructure and compressive strength (6.7 MPa). The present study revealed that AA-WBA for non-structural purposes can be obtained. The AA-WBA formulation contributes to the WBA valorization and development of low-carbon cements; therefore, it is an encouraged alternative to ordinary Portland cement (OPC). Considering the amounts and costs of the WBA, sodium silicate, NaOH, and water, the total cost of the developed formulations is comprised in a range between 137.6 and 153.9 €/Tn. Full article
(This article belongs to the Special Issue Recycling Waste in Construction Materials)
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14 pages, 1519 KiB  
Article
Use of Unbound Materials for Sustainable Road Infrastructures
by Donato Ciampa, Raffaele Cioffi, Francesco Colangelo, Maurizio Diomedi, Ilenia Farina and Saverio Olita
Appl. Sci. 2020, 10(10), 3465; https://doi.org/10.3390/app10103465 - 17 May 2020
Cited by 20 | Viewed by 3276
Abstract
The growing environmental sensitivity and the reduction of natural resources create, in Italy and other developed countries, an increasing interest in the search for alternative materials to be used in road construction works. In recent years, the problems related to environmental sustainability have [...] Read more.
The growing environmental sensitivity and the reduction of natural resources create, in Italy and other developed countries, an increasing interest in the search for alternative materials to be used in road construction works. In recent years, the problems related to environmental sustainability have made it increasingly difficult to remove natural aggregates from quarries and, at the same time, the regulations for the management of waste dumps are more and more restrictive. For this reason, the use of recycled aggregates is experiencing a continuous increase in the civil construction sector. This paper deals with the study of construction and demolition waste (CDW) in the field of road construction, in particular for the construction of embankment, road subgrades, foundation layers and unbound bases for flexible superstructures. Three different particle size fractions were used to prepare the mixtures: the first having a coarse size and designation 0–63 mm, the second intermediate size with aggregates of 0–31.5 mm grain size and the third with the finest aggregates having a grain size of 0–4 mm. The study was carried out by analyzing three granulometric fractions, verifying the best application for each of them. Subsequently, the mix-design was investigated, operating in compliance with the requirements imposed by UNI 11531-1, EN ISO 14688, EN 13242 and EN 13285. For the unbound layers of subgrade, foundation and base, which require greater resistance to fragmentation, the use of CDW alone has shown some limitations. Therefore, in the experimentation, it was decided to mix the CDW with a granulated slag coming from the steel production in the electric arc furnaces (EAF) and with an additional CDW (0–31.5 mm) coming from the recovery of concrete with slag. EAF granulated slag was used in small quantities, due to its relatively high cost. Four eco-friendly and recycled mixtures were studied, with low economic impact and high environmental sustainability, suitable for the construction of unbound layers of road superstructures. Full article
(This article belongs to the Special Issue Recycling Waste in Construction Materials)
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14 pages, 2198 KiB  
Article
Effect of Heat-Treatment Remediation on the Mechanical Behavior of Oil-Contaminated Soil
by Meng-Chia Weng, Chiou-Liang Lin and Cheng-Hsi Lee
Appl. Sci. 2020, 10(9), 3174; https://doi.org/10.3390/app10093174 - 02 May 2020
Cited by 6 | Viewed by 2317
Abstract
The heat treatment of oil-contaminated sites is widely carried out for the purposes of remediation. However, heat treatment changes the physical and chemical properties of soil. Before the soil can be reused as a construction material in civil engineering, such as in backfill [...] Read more.
The heat treatment of oil-contaminated sites is widely carried out for the purposes of remediation. However, heat treatment changes the physical and chemical properties of soil. Before the soil can be reused as a construction material in civil engineering, such as in backfill or road base materials, the changes to its physical properties must be understood. Therefore, this study investigates the changes in the physical and chemical properties of oil-contaminated soil after heat treatment. In this investigation, experimental samples of soil with added oil from a refinery plant are used to investigate the removal rate of total petroleum hydrocarbons (TPHs) by thermal desorption and incineration. The physical properties of the soil, including water permeability and mechanical properties, are compared before and after heat treatment. The results of this study are as follows. (1) Particle size analysis reveals that heat treatment makes soil particles finer. (2) In the burning reduction test, heat treatment at 900 °C removes more than 90% of THP. (3) In the direct shear test, the friction angle (ϕ) increases with the removal rate. (4) In the hydraulic test, as the removal rate increases, the permeability coefficient increases after heat treatment. Full article
(This article belongs to the Special Issue Recycling Waste in Construction Materials)
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15 pages, 5667 KiB  
Article
Bi-Layered Porous/Cork-Containing Waste-Based Inorganic Polymer Composites: Innovative Material towards Green Buildings
by Rui M. Novais, Luciano Senff, João Carvalheiras and João A. Labrincha
Appl. Sci. 2020, 10(9), 2995; https://doi.org/10.3390/app10092995 - 25 Apr 2020
Cited by 11 | Viewed by 2759
Abstract
Reduction of the energy consumption and CO2 emissions by the building sector might be a huge driver to mitigate climate change. One promising approach to mitigate energy consumption is the use of lightweight and low thermal-conductivity materials that could reduce the energy [...] Read more.
Reduction of the energy consumption and CO2 emissions by the building sector might be a huge driver to mitigate climate change. One promising approach to mitigate energy consumption is the use of lightweight and low thermal-conductivity materials that could reduce the energy losses inside buildings and at the same time the use of heating and cooling devices that generate associated CO2 emissions. In this study, different strategies to produce lightweight and low thermal conductivity inorganic polymers were evaluated and compared, including the first ever production of bi-layered porous/cork-containing waste-based inorganic polymer composites. The bi-layered composites showed the lowest density (461 kg/m3) and thermal conductivity (94.9 mW/m K) values and reasonable compressive strength (0.93 MPa) demonstrating their interesting potential for enhancing the energy efficiency of buildings. Moreover, these composites were produced at room temperature, using an industrial waste (biomass fly ash) as precursor and a highly sustainable and renewable resource as light aggregate (cork), preventing the depletion of natural resources and the use of fossil-fuel derivates, respectively. Full article
(This article belongs to the Special Issue Recycling Waste in Construction Materials)
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16 pages, 6129 KiB  
Article
Rock Material Recycling in Tunnel Engineering
by Klaus Voit and Erik Kuschel
Appl. Sci. 2020, 10(8), 2722; https://doi.org/10.3390/app10082722 - 15 Apr 2020
Cited by 18 | Viewed by 4443
Abstract
In the construction industry, especially in tunneling or large-scale earthworks projects, huge quantities of excavation material are generated as a by-product. Although at first glance such material is undesirable, in many cases this material, if suitably treated and processed, can be recycled and [...] Read more.
In the construction industry, especially in tunneling or large-scale earthworks projects, huge quantities of excavation material are generated as a by-product. Although at first glance such material is undesirable, in many cases this material, if suitably treated and processed, can be recycled and reused on the construction site and does not necessarily need to be removed and deposited as waste at a landfill. In the simplest case, the material can be used as filling material with the least demanding requirements with regard to rock quality. Material of better quality often can be recycled as aggregate and be used as a substitute for conventional mineral aggregates. This approach generates numerous benefits regarding the costs for material procurement, storage and transport. In addition, reduction in environmental impact and demand for landfill volume can be achieved. The challenge lies in the fact that excavation material is not a standard aggregate in terms of geometric, physical and chemical characteristics and is subject to quality deviations during tunnel driving, mainly depending on the varying geology and applied excavation method. Therefore, preliminary research and experimental testing as well as specific evaluation and continuous examination of the rock quality during tunnel driving is necessary as well as ongoing adjustment of the rock processing plant to finally accomplish a high-quality level of recycled aggregates. This article illustrates the material investigations and treatment processes for the specific example of the Brenner Base Tunnel, the longest underground railway line in the world that is currently under construction. There, material recycling has already been successfully implemented. Full article
(This article belongs to the Special Issue Recycling Waste in Construction Materials)
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16 pages, 3574 KiB  
Article
Improvement of Marine Clay Soil Using Lime and Alkaline Activation Stabilized with Inclusion of Treated Coir Fibre
by Fatin Amirah Kamaruddin, Haslinda Nahazanan, Bujang Kim Huat and Vivi Anggraini
Appl. Sci. 2020, 10(6), 2129; https://doi.org/10.3390/app10062129 - 20 Mar 2020
Cited by 21 | Viewed by 4973
Abstract
Waste products have recently been used as one of the techniques in soil stabilization. The material is not just environmentally friendly, but also cheap. In this study, two different types of soil stabilizer—lime and alkaline activator (AA) with the inclusion of treated coir [...] Read more.
Waste products have recently been used as one of the techniques in soil stabilization. The material is not just environmentally friendly, but also cheap. In this study, two different types of soil stabilizer—lime and alkaline activator (AA) with the inclusion of treated coir fibre as soil reinforcement in marine clay soil—were examined. The inclusion of fibre in the treated soil has had a positive impact in increasing the strength of the soil. Therefore, to assess the effectiveness of the soil treatment, mechanical tests such as indirect tensile strength, flexural test and unconfined compressive strength test were performed at three different curing periods (7, 28 and 90 days) on both untreated and treated soil. From the results, the inclusion of fibre in both lime and alkaline activation indicates an enhancement on post-peak behaviour from brittle to more ductile. Microstructural analyses of Field Emission Scanning Electron Microscope (FESEM) and Energy Dispersive X-ray (EDX) were also conducted after shearing to evaluate the changes of the soil before and after the treatment. Overall, results indicate that the treatment transformed the structure of the soil to become denser where it filled the large pores compared to untreated soil. Full article
(This article belongs to the Special Issue Recycling Waste in Construction Materials)
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20 pages, 6037 KiB  
Article
Recycling and Application of Mine Tailings in Alkali-Activated Cements and Mortars—Strength Development and Environmental Assessment
by Nuno Cristelo, João Coelho, Mafalda Oliveira, Nilo Cesar Consoli, Ángel Palomo and Ana Fernández-Jiménez
Appl. Sci. 2020, 10(6), 2084; https://doi.org/10.3390/app10062084 - 19 Mar 2020
Cited by 20 | Viewed by 3382
Abstract
Mine tailings (MT) could represent a step forward in terms of the quality of the aggregates usually used in civil engineering applications, mostly due to its high density. The Portuguese Neves Corvo copper mine, owned by the Lundin Mining Corporation, produces approximately 3 [...] Read more.
Mine tailings (MT) could represent a step forward in terms of the quality of the aggregates usually used in civil engineering applications, mostly due to its high density. The Portuguese Neves Corvo copper mine, owned by the Lundin Mining Corporation, produces approximately 3 million tonnes per year. Nevertheless, it cannot be used in its original state, due to its high levels of sulphur and other metals (As, Cr, Cu, Pb, Zn). This paper focuses on the stabilisation/solidification of high-sulphur MT, without any previous thermal treatment, using alkali-activated fly ash (FA). The variables considered were the MT/FA ratio and the activator type and concentration. A fine aggregate was then added to the pastes to assess the quality of the resulting mortar. Maximum compressive strengths of 14 MPa and 24 MPa were obtained for the pastes and mortars, respectively, after curing for 24 h at 85 °C. Thermogravimetric analysis, scanning electron microscopy, X-ray energy dispersive spectroscopy, X-ray diffraction, and infrared spectroscopy were used to characterize the reaction products, and two types of leaching tests were performed to assess the environmental performance. The results showed that the strength increase is related with the formation of a N-A-S-H gel, although sodium sulphate carbonate was also developed, suggesting that the total sodium intake could be optimized without strength loss. The solubility of the analysed metals in the paste with 78% MT and 22% FA was below the threshold for non-hazardous waste. Full article
(This article belongs to the Special Issue Recycling Waste in Construction Materials)
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11 pages, 7423 KiB  
Article
Characterization of Fresh and Cured Properties of Polymer Concretes Based on Two Metallurgical Wastes
by Andres Seco, Angel Maria Echeverría, Sara Marcelino, Benat García and Sandra Espuelas
Appl. Sci. 2020, 10(3), 825; https://doi.org/10.3390/app10030825 - 23 Jan 2020
Cited by 2 | Viewed by 1760
Abstract
Polyester polymer concretes can substitute conventional concretes based on their usually good mechanical strength, adequate physical properties, and high resistance against aggressive chemical environments. They also show a high potential for using recycled targets in their manufacturing. This paper analyzes the fresh and [...] Read more.
Polyester polymer concretes can substitute conventional concretes based on their usually good mechanical strength, adequate physical properties, and high resistance against aggressive chemical environments. They also show a high potential for using recycled targets in their manufacturing. This paper analyzes the fresh and cured properties of polyester polymer concretes containing two metallurgical wastes, namely: ladle slag and alumina filler. Both targets require a higher resin dosage than sand. The standard consistency test showed a low representativeness of the recycled fresh mixes’ workability. The ladle slag and alumina filler samples showed a higher length plastic shrinkage than those containing sand. All of the targets obtained cured density values in the range of 1.589–1.912 g/cm3. From a mechanical point of view, the sand and alumina filler containing polyester polymer concretes reached 11.02 and 10.93 kN, respectively, of flexural strength, while the ladle slag samples showed the best result with 19.31 kN. In the compressive strength test, the sand and alumina filler combinations reached 106.16 and 104.21 MPa, respectively, while the ladle slag achieved 160.48 MPa. The flexural and compressive elasticity modulus showed similar trends related to the resin content. Full article
(This article belongs to the Special Issue Recycling Waste in Construction Materials)
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Review

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20 pages, 1598 KiB  
Review
Inorganic Waste Generated in Kraft Pulp Mills: The Transition from Landfill to Industrial Applications
by Margarida J. Quina and Carolina T. Pinheiro
Appl. Sci. 2020, 10(7), 2317; https://doi.org/10.3390/app10072317 - 28 Mar 2020
Cited by 28 | Viewed by 6951
Abstract
Kraft pulp mills produce the main raw material for paper, while several waste products are generated in large quantities in the process. This review study addresses four of the main inorganic wastes formed by this industry, namely green liquor dregs (GLD), slaker grits [...] Read more.
Kraft pulp mills produce the main raw material for paper, while several waste products are generated in large quantities in the process. This review study addresses four of the main inorganic wastes formed by this industry, namely green liquor dregs (GLD), slaker grits (SG), lime mud (LM) and boiler fly ash (BFA), which are still mostly discarded in landfills. A brief overview of a typical industrial process was included to outline the waste generation points. The main chemical and physical properties are indicated for highlighting the most relevant characteristics to determine which applications may be considered in each case. An in-depth literature review allowed the identification of the main applications that have been tested mainly at the laboratory scale and some at an industrial scale. The applications are grouped into construction materials, geotechnical, environmental, agricultural and others. This assessment shows that the circular economy and the sustainable development goals of the UN are important issues for organizations in general, and the pulp mill in particular. In fact, this industry has managed to close the chemicals loops, recover energy and reduce water consumption in the process. However, the current situation of inorganic waste can still be improved if industrial applications are developed to avoid landfill. Full article
(This article belongs to the Special Issue Recycling Waste in Construction Materials)
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9 pages, 1833 KiB  
Review
Utilization of Molybdenum Tailings in Concrete Manufacturing: A Review
by Shan Gao, Xiaowei Cui and Sumei Zhang
Appl. Sci. 2020, 10(1), 138; https://doi.org/10.3390/app10010138 - 23 Dec 2019
Cited by 24 | Viewed by 2947
Abstract
Dealing with mineral tailings is one of the most important topics for solving the environmental problems in the mining industry. Among the techniques converting stacked molybdenum tailings to reusable cleaner products, one of the most effective ones is to use molybdenum tailings in [...] Read more.
Dealing with mineral tailings is one of the most important topics for solving the environmental problems in the mining industry. Among the techniques converting stacked molybdenum tailings to reusable cleaner products, one of the most effective ones is to use molybdenum tailings in concrete productions. The physical properties including density, microscopic structure and finesse module, and chemical composition of molybdenum tailings are similar with those of natural sand. The radionuclide assessment of molybdenum tailing meets the requirements for using as structural materials. Therefore, Molybdenum tailing is suitable to be used as the replacement of cement and fine aggregates in mortar and concrete. Based on the results of strength and duration performance comparison, the usage of molybdenum tailing as a replacement of natural sand is a more feasible way than that of ground super-fine molybdenum tailings in cement binder. It is feasible to use molybdenum tailings as fine aggregate in the preparation of structural concrete. When the amount of ground super-fine molybdenum tailings replacing cement is less than 10%, it is beneficial to improve the freeze-thaw and carbonization resistance of the concrete. Full article
(This article belongs to the Special Issue Recycling Waste in Construction Materials)
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