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Recycled Aggregate Concrete and Alternative Binders for Sustainable Building Engineering
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Recycled Aggregate Concrete and Alternative Binders for Sustainable Building Engineering

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Construction and Building Materials".

Deadline for manuscript submissions: closed (30 November 2021) | Viewed by 41193

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Prof. Dr. Miguel Bravo

E-Mail Website
Guest Editor
CERIS, IST-ID, Department of Civil Engineering, Architecture and Georresources, Instituto Superior Técnico (IST), Universidade de Lisboa, 1049-001 Lisbon, Portugal
Interests: materials science; sustainability in construction; recycled aggregate concrete; cementitious materials from industrial byproducts; supplementary cementitious materials; alkali-activated materials
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Rui Vasco Silva

E-Mail Website
Guest Editor
CERIS, IST-ID, Department of Civil Engineering, Architecture and Georesources, Instituto Superior Técnico (IST), Universidade de Lisboa, Lisbon, Portugal
Interests: materials science; civil engineering; sustainability in construction; recycled aggregate concrete; alkali-activated materials; supplementary cementitious materials
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. António P.C. Duarte

E-Mail Website
Guest Editor
CERIS, IST-ID, Department of Civil Engineering, Architecture and Georresources, Instituto Superior Técnico (IST), Universidade de Lisboa, Lisbon, Portugal
Interests: materials science and technology; recycled aggregate concrete; sustainability of construction; structural and computational mechanics; steel–concrete composite structures; composite materials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The construction industry is considered one of the most important sectors of socio-economic development. However, its dynamism gives rise to two major environmental issues: (i) a significant increase of construction and demolition waste (CDW), which represents more than 30% of the solid waste generated by all economic sectors, and (ii) an increase in the production of Portland cement concrete, which is the most widely used construction material in the world and, through the production of cement alone, constitutes about 7% of all greenhouse gas emissions. Hence, it is essential to find, on the one hand, solutions for discarded CDW, in addition to their use as recycled aggregates, and, on the other hand, alternative sustainable binders that can replace Portland cement.

This Special Issue focuses on the development of sustainable cementitious composites, either by the replacement of natural aggregates with recycled aggregates or by the use of sustainable binding technologies that constitute a viable alternative to Portland cement.

The main topics covered in this Special Issue are (but not limited to) the following:

  • Experimental characterization (rheological, physical, mechanical, durability-related, thermal, etc.) of cementitious composites containing recycled aggregates (from all origins);
  • Experimental characterization of new sustainable alternative binders and cementitious composites containing them;
  • Development and implementation of analytical methods, numerical models, and optimization algorithms applied to the characterization of sustainable materials and structures produced with them;
  • Development of inspection and diagnostic methodologies and techniques for evaluating the performance of sustainable materials and structures containing them;
  • Life cycle assessment (LCA) and life cycle cost analysis (LCC) of sustainable materials and structures with them;

Work on subjects other than the aforementioned that contribute to advancing knowledge of sustainable materials and their applications are also welcome in this Special Issue.

Further information on this Special Issue may be obtained at the following link:

https://www.mdpi.com/journal/materials/special_issues/Recycle_Aggregate_Concrete_Alternative_Binders_Sustainable

We kindly invite you to submit a manuscript(s) for this Special Issue. Full papers, communications, and reviews presenting and discussing the most recent trends in the field are all welcome.

Prof. Dr. Miguel Bravo
Prof. Dr. Rui Vasco Silva
Prof. Dr. António P.C. Duarte
Guest Editors

Manuscript Submission Information

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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. Materials 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 2600 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

  • sustainable construction
  • recycled aggregate concrete
  • sustainable alternative binders
  • supplementary cementitious materials
  • construction and demolition waste
  • carbon dioxide
  • alkali-activated materials
  • low environmental impact

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Published Papers (16 papers)

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Research

26 pages, 5931 KiB  
Article
Influence of the Mix Proportion and Aggregate Features on the Performance of Eco-Efficient Fine Recycled Concrete Aggregate Mixtures
by Diego Jesus De Souza, Mayra T. de Grazia, Hian F. Macedo, Leandro F. M. Sanchez, Gabriella P. de Andrade, Olga Naboka, Gholamreza Fathifazl and Pierre-Claver Nkinamubanzi
Materials 2022, 15(4), 1355; https://doi.org/10.3390/ma15041355 - 12 Feb 2022
Cited by 4 | Viewed by 2405
Abstract
Most of the previous research on recycled concrete aggregates (RCA) has focused on coarse RCA (CRCA), while much less has been accomplished on the use of fine RCA particles (FRCA). Furthermore, most RCA research disregards its unique microstructure, and thus the inferior performance [...] Read more.
Most of the previous research on recycled concrete aggregates (RCA) has focused on coarse RCA (CRCA), while much less has been accomplished on the use of fine RCA particles (FRCA). Furthermore, most RCA research disregards its unique microstructure, and thus the inferior performance of concrete incorporating RCA is often reported in the fresh and hardened states. To improve the overall behaviour of RCA concrete advanced mix design techniques such as equivalent volume (EV) or particle packing models (PPMs) may be used. However, the efficiency of these procedures to proportion eco-efficient FRCA concrete still requires further investigation. This work evaluates the overall fresh (i.e., slump and rheological characterization) and hardened states (i.e., non-destructive tests, compressive strength and microscopy) performance of sustainable FRCA mixtures proportioned through distinct techniques (i.e., direct replacement, EV and PPMs) and incorporating different types of aggregates (i.e., natural and manufactured sand) and manufacturing processes (i.e., crusher fines and fully ground). Results demonstrate that the aggregate type and crushing process may influence the FRCA particles’ features. Yet, the use of advanced mix design techniques, particularly PPMs, may provide FRCA mixes with quite suitable performance in the fresh (i.e., 49% lower yield stress) and hardened states (i.e., 53% higher compressive strength) along with a low carbon footprint. Full article
(This article belongs to the Special Issue Recycled Aggregate Concrete and Alternative Binders for Sustainable Building Engineering)
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23 pages, 44440 KiB  
Article
Freezing and Thawing Resistance of Fine Recycled Concrete Aggregate (FRCA) Mixtures Designed with Distinct Techniques
by Cassandra Trottier, Mayra T. de Grazia, Hian F. Macedo, Leandro F. M. Sanchez, Gabriella P. de Andrade, Diego J. de Souza, Olga Naboka, Gholamreza Fathifazl, Pierre-Claver Nkinamubanzi and André Demers
Materials 2022, 15(4), 1342; https://doi.org/10.3390/ma15041342 - 11 Feb 2022
Cited by 9 | Viewed by 2366
Abstract
The pressure to use sustainable materials and adopt practices reducing the carbon footprint of the construction industry has risen. Such materials include recycled concrete aggregates (RCA) made from waste concrete. However, concrete made with RCA often presents poor fresh and hardened properties along [...] Read more.
The pressure to use sustainable materials and adopt practices reducing the carbon footprint of the construction industry has risen. Such materials include recycled concrete aggregates (RCA) made from waste concrete. However, concrete made with RCA often presents poor fresh and hardened properties along with a decrease in its durability performance, especially when using its fine fraction (i.e., FRCA). Most studies involving FRCA use direct replacement methods (DRM) to proportion concrete although other techniques are available such as the Equivalent Volume (EV) and Particle Packing Models (PPMs); yet their impact on the durability performance, especially its performance against freezing and thawing (F/T), remains unknown. This work, therefore, appraises the F/T resistance of FRCA mixtures proportioned through various mix proportioning techniques (i.e., DRM, EV and PPMs), produced with distinct crushing processes (i.e., crusher’s fines vs. finely ground). The results show that the mix design technique has a significant influence on the FRCA mixture’s F/T resistance where PPM-proportioned mixtures demonstrate the best overall performance, exceeding the specified requirements while DRM-proportioned mixtures failed F/T resistance requirements. Moreover, the crushing process plays an important role in the recycled mixtures’ cracking behavior under F/T cycles, where less processing leads to fewer cracks while remaining the most sustainable option overall. Full article
(This article belongs to the Special Issue Recycled Aggregate Concrete and Alternative Binders for Sustainable Building Engineering)
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14 pages, 5720 KiB  
Article
Utilization of Waste Glass in Autoclaved Silica–Lime Materials
by Katarzyna Borek and Przemysław Czapik
Materials 2022, 15(2), 549; https://doi.org/10.3390/ma15020549 - 12 Jan 2022
Cited by 5 | Viewed by 2047
Abstract
This paper aims to investigate the possibility of using waste glass of different colours as a complete substitute for quartz sand in autoclaved silica–lime samples. On the one hand, this increases the possibility of recycling waste glass; on the other hand, it allows [...] Read more.
This paper aims to investigate the possibility of using waste glass of different colours as a complete substitute for quartz sand in autoclaved silica–lime samples. On the one hand, this increases the possibility of recycling waste glass; on the other hand, it allows obtaining autoclaved materials with better properties. In this research, reference samples with quartz sand (R) and white (WG), brown (BG), and green (GG) waste container glass were made. Parameters such as compressive strength, bulk density, and water absorption were examined on all samples. The samples were examined using a scanning electron microscope with an energy dispersive spectroscopy detector (SEM/EDS) and subjected to X-ray diffraction (XRD) analysis. The WG samples showed 187% higher compressive strength, BG by 159%, and GG by 134% compared to sample R. In comparison to the reference sample, volumetric density was 16.8% lower for sample WG, 13.2% lower for BG, and 7.1% lower for GG. Water absorption increased as bulk density decreased. The WG sample achieved the highest water absorption value, 15.84%. An X-ray diffraction analysis confirmed the presence of calcite, portlandite, and tobermorite phases. Depending on the silica aggregate used, there were differences in phase composition linked to compressive strength. Hydrated calcium silicates with varying crystallisation degrees were visible in the microstructure image. Full article
(This article belongs to the Special Issue Recycled Aggregate Concrete and Alternative Binders for Sustainable Building Engineering)
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22 pages, 7205 KiB  
Article
Influence of Bentonite on Mechanical and Durability Properties of High-Calcium Fly Ash Geopolymer Concrete with Natural and Recycled Aggregates
by Rana Muhammad Waqas, Faheem Butt, Aamar Danish, Muwaffaq Alqurashi, Mohammad Ali Mosaberpanah, Bilal Masood and Enas E. Hussein
Materials 2021, 14(24), 7790; https://doi.org/10.3390/ma14247790 - 16 Dec 2021
Cited by 29 | Viewed by 3457
Abstract
In this study, bentonite (a naturally occurring pozzolana) was incorporated as a partial replacement (up to 20%) for high-calcium fly ash (HCFA)-based geopolymeric natural aggregate concrete (GNAC) and geopolymeric recycled aggregate concrete (GRAC). The mechanical (compressive strength and splitting tensile strength), durability (chloride [...] Read more.
In this study, bentonite (a naturally occurring pozzolana) was incorporated as a partial replacement (up to 20%) for high-calcium fly ash (HCFA)-based geopolymeric natural aggregate concrete (GNAC) and geopolymeric recycled aggregate concrete (GRAC). The mechanical (compressive strength and splitting tensile strength), durability (chloride migration coefficient, water absorption, and acid attack resistance), and rheological properties (slump test, fresh density, and workability) were investigated. The results revealed that incorporation of bentonite (10 wt % with ordinary Portland cement) showed appreciable improvement in the strength and durability of both the GNAC and GRAC, though its effect is more significant for GRAC than the GNAC. Full article
(This article belongs to the Special Issue Recycled Aggregate Concrete and Alternative Binders for Sustainable Building Engineering)
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22 pages, 3794 KiB  
Article
Evaluation of Eco-Efficient Concretes Produced with Fly Ash and Uncarbonated Recycled Aggregates
by Miren Etxeberria
Materials 2021, 14(24), 7499; https://doi.org/10.3390/ma14247499 - 7 Dec 2021
Cited by 9 | Viewed by 2176
Abstract
The fabrication of conventional concrete, as well as remains from demolition, has a high environmental impact. This paper assessed the eco-efficiency of concrete made with uncarbonated recycled concrete aggregates (RCA) and fly ash (FA). Two concrete series were produced with an effective water/cement [...] Read more.
The fabrication of conventional concrete, as well as remains from demolition, has a high environmental impact. This paper assessed the eco-efficiency of concrete made with uncarbonated recycled concrete aggregates (RCA) and fly ash (FA). Two concrete series were produced with an effective water/cement ratio of 0.50 (Series 1) and 0.40 (Series 2). In both series, concretes were produced using 0% and 50% of RCA with 0%, 25% and 50% FA. After analysing the compressive strength, and carbonation and chloride resistance of those concretes, their eco-efficiency based on the binder intensity and CO2-eq intensity was assessed. We found that the use of 50% uncarbonated RCA improved the properties of concretes produced with FA with respect to using natural aggregates. The concrete made of 25% FA plus RCA was considered the most eco-efficient based on the tests of compressive, carbonation and chloride properties with the values of 4.1 kg CO2 m−3 MPa−1, 76.3 kg CO2 m−3 mm−1 year0.5 and 0.079 kg CO2 m−3 C−1, respectively. The uncarbonated RCA improved carbonation resistance, and FA improved chloride resistance. It can be concluded that the use of 50% un-carbonated RCA combined with FA considerably enhanced the properties of hardened concrete and their eco-efficiency with respect to concretes produced with natural aggregates. Full article
(This article belongs to the Special Issue Recycled Aggregate Concrete and Alternative Binders for Sustainable Building Engineering)
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15 pages, 4993 KiB  
Article
Influence of Asphalt Emulsion Inclusion on Fly Ash/Hydrated Lime Alkali-Activated Material
by Thanon Bualuang, Peerapong Jitsangiam, Teewara Suwan, Ubolluk Rattanasak, Weerachart Tangchirapat and Suriyah Thongmunee
Materials 2021, 14(22), 7017; https://doi.org/10.3390/ma14227017 - 19 Nov 2021
Cited by 10 | Viewed by 2131
Abstract
Supplementary cementitious materials have been widely used to reduce the greenhouse gas emissions caused by ordinary Portland cement (OPC), including in the construction of road bases. In addition, the use of OPC in road base stabilization is inefficient due to its moisture sensitivity [...] Read more.
Supplementary cementitious materials have been widely used to reduce the greenhouse gas emissions caused by ordinary Portland cement (OPC), including in the construction of road bases. In addition, the use of OPC in road base stabilization is inefficient due to its moisture sensitivity and lack of flexibility. Therefore, this study investigates the effect of hybrid alkali-activated materials (H-AAM) on flexibility and water prevention when used as binders while proposing a new and sustainable material. A cationic asphalt emulsion (CAE) was applied to increase this cementless material’s resistance to moisture damage and flexibility. The physical properties and structural formation of this H-AAM, consisting of fly ash, hydrated lime, and sodium hydroxide, were examined. The results revealed that the addition of CAE decreased the material’s mechanical strength due to its hindrance of pozzolanic reactions and alkali activations. This study revealed decreases in the cementitious product’s peak in the x-ray diffraction analysis (XRD) tests and the number of tetrahedrons detected in the Fourier transform infrared spectroscopy analysis (FTIR) tests. The scanning electron microscope (SEM) images showed some signs of asphalt films surrounding hybrid alkali-activated particles and even some unreacted FA particles, indicating incomplete chemical reactions in the study material’s matrix. However, the H-AAM was still able to meet the minimum road base strength requirement of 1.72 MPa. Furthermore, the toughness and flexibility of the H-AAM were enhanced by CAE. Notably, adding 10% and 20% CAE by weight to the hybrid alkali-activated binder produced a significant advantage in terms of water absorption, which can be explained by its influence on the material’s consolidation of its matrices, resulting in significant void reductions. Hence, the outcomes of this study might reveal an opportunity for developing a new stabilizing agent for road bases with water-prevention properties and flexibility that remains faithful to the green construction material concept. Full article
(This article belongs to the Special Issue Recycled Aggregate Concrete and Alternative Binders for Sustainable Building Engineering)
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19 pages, 9258 KiB  
Article
Thermal Properties of Calcium Sulphoaluminate Cement as an Alternative to Ordinary Portland Cement
by Małgorzata Gołaszewska, Barbara Klemczak and Jacek Gołaszewski
Materials 2021, 14(22), 7011; https://doi.org/10.3390/ma14227011 - 19 Nov 2021
Cited by 9 | Viewed by 2061
Abstract
This paper presents the results of research into the heat of hydration and activation energy of calcium sulphoaluminate (CSA) cement in terms of the dependence on curing temperature and water/cement ratio. Cement pastes with water/cement ratios in the range of 0.3–0.6 were tested [...] Read more.
This paper presents the results of research into the heat of hydration and activation energy of calcium sulphoaluminate (CSA) cement in terms of the dependence on curing temperature and water/cement ratio. Cement pastes with water/cement ratios in the range of 0.3–0.6 were tested by isothermal calorimetry at 20 °C, 35 °C and 50 °C, with the evolved hydration heat and its rate monitored for 168 h from mixing water with cement. Reference pastes with ordinary Portland cement (OPC) were also tested in the same range. The apparent activation energy of CSA and OPC was determined based on the results of the measurements. CSA pastes exhibited complex thermal behaviour that differed significantly from the thermal behaviour of ordinary Portland cement. The results show that both the w/c ratio and elevated temperature have a meaningful effect on the heat emission and the hydration process of CSA cement pastes. The determined apparent activation energy of CSA revealed its substantial variability and dependence, both on the w/c ratio and the curing temperature. Full article
(This article belongs to the Special Issue Recycled Aggregate Concrete and Alternative Binders for Sustainable Building Engineering)
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19 pages, 1743 KiB  
Article
Performance of Mortars Made Using Ternary Binders with Addition of Slag, Fly Ash and Limestone Exposed to a Real Environmental Condition Compatible with Exposure Class XC3
by Javier Ibáñez-Gosálvez, Teresa Real-Herraiz and José Marcos Ortega
Materials 2021, 14(20), 5937; https://doi.org/10.3390/ma14205937 - 10 Oct 2021
Cited by 2 | Viewed by 1593
Abstract
The use of eco-friendly cements prepared with ternary binders could contribute to improving the sustainability of cement production. However, their use for manufacturing commercial cements is very low, at least in Spain. The purpose of this research is to study the behavior in [...] Read more.
The use of eco-friendly cements prepared with ternary binders could contribute to improving the sustainability of cement production. However, their use for manufacturing commercial cements is very low, at least in Spain. The purpose of this research is to study the behavior in the long term of mortars made with ternary binders which incorporated ground granulated blast furnace slag, fly ash, and limestone, exposed to environmental conditions compatible with the specifications of exposure class XC3 of the Eurocode 2, compared to mortars without additions and mortars with binary binders. The exposure station was placed in an underground floor of a building used as a garage with circulation of vehicles and moderately high CO2 concentration. The ternary and binary binders verified the prescriptions of cement type CEM II/B. The microstructure was characterized using mercury intrusion porosimetry and electrical resistivity. Water absorption, diffusion coefficient, carbonation depth, mechanical strengths, and ultrasonic pulse velocity were determined. A loss of microstructure refinement with time was noted for all the analyzed binders, probably related to the development of carbonation and drying shrinkage. The binary mortars with slag and fly ash and the ternary binder which combined them showed the best mechanical performance at 250 days. Full article
(This article belongs to the Special Issue Recycled Aggregate Concrete and Alternative Binders for Sustainable Building Engineering)
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22 pages, 10161 KiB  
Article
Eurocode Shear Design of Coarse Recycled Aggregate Concrete: Reliability Analysis and Partial Factor Calibration
by João Pacheco, Jorge de Brito, Carlos Chastre and Luís Evangelista
Materials 2021, 14(15), 4081; https://doi.org/10.3390/ma14154081 - 22 Jul 2021
Cited by 11 | Viewed by 2000
Abstract
This paper contributes to the definition of design clauses for coarse recycled aggregate concrete. One of the main reasons for scepticism towards recycled aggregate concrete is the perceived notion that the heterogeneity of recycled aggregates may increase the uncertainty of the behaviour of [...] Read more.
This paper contributes to the definition of design clauses for coarse recycled aggregate concrete. One of the main reasons for scepticism towards recycled aggregate concrete is the perceived notion that the heterogeneity of recycled aggregates may increase the uncertainty of the behaviour of concrete. Therefore, the paper uses structural reliability concepts to propose partial factors for recycled aggregate concrete’s design for shear failure. The paper builds upon a previous publication by the authors, in which the model uncertainty of recycled aggregate concrete elements designed for shear, with and without shear reinforcement, was compared with that of natural aggregate concrete elements. In that paper, the statistics of the model uncertainty for recycled aggregate concrete shear design were indeed found to be less favourable than those of natural aggregate concrete. Therefore, a partial factor for recycled aggregate concrete design is needed to ensure safety. This paper presents partial factors calibrated with explicit reliability analyses for different cases of design concerning beams (in the case of shear design of elements with shear reinforcement) and slabs (for the design of elements without shear reinforcement). For full incorporation of coarse recycled concrete aggregates and the design of elements without shear reinforcement, the calibrated partial factor reduces the design value of shear resistance by 10% (design with EN1992) or 15% (design with prEN1992) in comparison to natural aggregate concrete’s design. For the shear design of elements with shear reinforcement, the partial factor decreases resistance by 5% but a sensitivity analysis showed that the reduction might be, under pessimistic expectations, of up to 20%. Full article
(This article belongs to the Special Issue Recycled Aggregate Concrete and Alternative Binders for Sustainable Building Engineering)
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14 pages, 15184 KiB  
Article
An Experimental Study of Possible Post-War Ferronickel Slag Waste Disposal in Szklary (Lower Silesian, Poland) as Partial Aggregate Substitute in Concrete: Characterization of Physical, Mechanical, and Thermal Properties
by Marcin Małek, Mateusz Jackowski, Waldemar Łasica, Kamil Dydek and Anna Boczkowska
Materials 2021, 14(10), 2552; https://doi.org/10.3390/ma14102552 - 14 May 2021
Cited by 5 | Viewed by 2694
Abstract
Aggregates derived from waste, due to the growing awareness of global warming, are more and more often used in the concrete production process. This way, their disposal not only reduces the pollution of the Earth but also lowers the consumption of natural aggregates, [...] Read more.
Aggregates derived from waste, due to the growing awareness of global warming, are more and more often used in the concrete production process. This way, their disposal not only reduces the pollution of the Earth but also lowers the consumption of natural aggregates, which are limited. One of the new “eco” aggregates may be a ferronickel slag waste (FNSW), which was generated in post-war metallurgical processes and stored in Szklary (Lower Silesian, Poland). In order to determine the possibility of using ferronickel slag waste aggregate (FNSWA) in the concrete production process, new concrete mixtures were designed and tested. Physical properties (cone slump, air content, pH, and density), mechanical properties (compressive strength, flexural strength, and tensile strength), and thermal properties (thermal conductivity) were assessed for all new laboratory recipes. Moreover, the modulus of elasticity and Poisson’s ratio were determined. This study includes five different contents of FNSWA in the amount of 5%, 10%, 15%, 20%, and 25% of the mass of natural aggregate as its partial substitute. The final results were compared to the base sample (BS) containing 100% natural aggregate, which was granite. Full article
(This article belongs to the Special Issue Recycled Aggregate Concrete and Alternative Binders for Sustainable Building Engineering)
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15 pages, 5323 KiB  
Article
Characteristics of Waste Iron Powder as a Fine Filler in a High-Calcium Fly Ash Geopolymer
by Toon Nongnuang, Peerapong Jitsangiam, Ubolluk Rattanasak, Weerachart Tangchirapat, Teewara Suwan and Suriyah Thongmunee
Materials 2021, 14(10), 2515; https://doi.org/10.3390/ma14102515 - 12 May 2021
Cited by 22 | Viewed by 2586
Abstract
Geopolymer (GP) has been applied as an environmentally-friendly construction material in recent years. Many pozzolanic wastes, such as fly ash (FA) and bottom ash, are commonly used as source materials for synthesizing geopolymer. Nonetheless, many non-pozzolanic wastes are often applied in the field [...] Read more.
Geopolymer (GP) has been applied as an environmentally-friendly construction material in recent years. Many pozzolanic wastes, such as fly ash (FA) and bottom ash, are commonly used as source materials for synthesizing geopolymer. Nonetheless, many non-pozzolanic wastes are often applied in the field of civil engineering, including waste iron powder (WIP). WIPs are massively produced as by-products from iron and steel industries, and the production rate increases every year. As an iron-based material, WIP has properties of heat induction and restoration, which can enhance the heat curing process of GP. Therefore, this study aimed to utilize WIP in high-calcium FA geopolymer to develop a new type of geopolymer and examine its properties compared to the conventional geopolymer. Scanning electron microscopy and X-ray diffraction were performed on the geopolymers. Mechanical properties, including compressive strength and flexural strength, were also determined. In addition, setting time and temperature monitoring during the heat curing process were carried out. The results indicated that the addition of WIP in FA geopolymer decreased the compressive strength, owing to the formation of tetrahydroxoferrate (II) sodium or Na2[Fe(OH)4]. However, a significant increase in the flexural strength of GP with WIP addition was detected. A flexural strength of 8.5 MPa was achieved by a 28-day sample with 20% of WIP addition, nearly three times higher than that of control. Full article
(This article belongs to the Special Issue Recycled Aggregate Concrete and Alternative Binders for Sustainable Building Engineering)
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20 pages, 5803 KiB  
Article
Stabilized High Clay Content Lateritic Soil Using Cement-FGD Gypsum Mixtures for Road Subbase Applications
by Phattharachai Maichin, Peerapong Jitsangiam, Toon Nongnuang, Kornkanok Boonserm, Korakod Nusit, Suriyavut Pra-ai, Theechalit Binaree and Chuchoke Aryupong
Materials 2021, 14(8), 1858; https://doi.org/10.3390/ma14081858 - 8 Apr 2021
Cited by 27 | Viewed by 4238
Abstract
With a lack of standard lateritic soil for use in road construction, suitable economical and sustainable soil-stabilization techniques are in demand. This study aimed to examine flue gas desulfurization (FGD) gypsum, a by-product of coal power plants, for use in soil–cement stabilization, specifically [...] Read more.
With a lack of standard lateritic soil for use in road construction, suitable economical and sustainable soil-stabilization techniques are in demand. This study aimed to examine flue gas desulfurization (FGD) gypsum, a by-product of coal power plants, for use in soil–cement stabilization, specifically for ability to strengthen poor high-clay, lateritic soil but with a lower cement content. A series of compaction tests and unconfined compressive strength (UCS) tests were performed in conjunction with scanning electron microscope (SEM) analyses. Therefore, the strength development and the role of FGD gypsum in the soil–cement–FGD gypsum mixtures with varying cement and FGD gypsum contents were characterized in this study. The study results showed that adding FGD gypsum can enhance the strength of the stabilized substandard lateritic soil. Extra FGD gypsum added to the cement hydration system provided more sulfate ions, leading to the formation of ettringite and monosulfate, which are the hardening cementitious products from the cement hydration reaction. Both products contributed to the strength gain of the soil–cement–FGD gypsum material. However, the strength can be reduced when too much FGD gypsum is added because the undissolved gypsum has a weak structure. Examinations of FGD gypsum in the soil–cement–FGD gypsum mixtures by SEM confirmed that adding FGD gypsum can reduce the cement content in a soil–cement mix to achieve a given UCS value. Full article
(This article belongs to the Special Issue Recycled Aggregate Concrete and Alternative Binders for Sustainable Building Engineering)
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14 pages, 2022 KiB  
Article
Microstructure and Durability Performance of Mortars with Volcanic Powder from Calbuco Volcano (Chile) after 4 Hardening Years
by Rosa María Tremiño, Teresa Real-Herraiz, Viviana Letelier and José Marcos Ortega
Materials 2021, 14(7), 1751; https://doi.org/10.3390/ma14071751 - 2 Apr 2021
Viewed by 1382
Abstract
One of the most popular ways to lessen the impact of the cement industry on the environment consists of substituting clinker by additions. The service life required for real construction elements is generally long, so it would be interesting to obtain information about [...] Read more.
One of the most popular ways to lessen the impact of the cement industry on the environment consists of substituting clinker by additions. The service life required for real construction elements is generally long, so it would be interesting to obtain information about the effects of new additions after a hardening period of several years. Analyzed here are the effects of the incorporation of volcanic ashes, coming from Calbuco volcano’s last eruption (Chile), as clinker replacement, in the durability and pore structure of mortars, after approximately 4 hardening years (1500 days), in comparison with reference specimens without additions. The substitution percentages of clinker by volcanic powder studied were 10% and 20%. The microstructure was characterized with mercury intrusion porosimetry and impedance spectroscopy. In order to evaluate the pozzolanic activity of the volcanic powder after 1500 days, differential thermal analyses were performed. Water absorption after immersion, steady-state diffusion coefficient and length change were also studied. In accordance with the results obtained, the 10% and 20% substitution of clinker by volcanic powder from the Calbuco volcano showed beneficial effects in the mortars after 4 years, especially regarding the microstructure and chloride diffusion, without noticeable influence in their water absorption. Full article
(This article belongs to the Special Issue Recycled Aggregate Concrete and Alternative Binders for Sustainable Building Engineering)
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23 pages, 9347 KiB  
Article
Recycled Mortars with Ceramic Aggregates. Pore Network Transmutation and Its Relationship with Physical and Mechanical Properties
by Francisca Guadalupe Cabrera-Covarrubias, José Manuel Gómez-Soberón, Carlos Antonio Rosas-Casarez, Jorge Luis Almaral-Sánchez and Jesús Manuel Bernal-Camacho
Materials 2021, 14(6), 1543; https://doi.org/10.3390/ma14061543 - 21 Mar 2021
Cited by 4 | Viewed by 2580
Abstract
The porosity of mortars with recycled ceramic aggregates (10, 20, 30, 50, and 100% as a replacement of natural aggregate) was evaluated and analyzed using three different techniques. The results of gas adsorption (N2), Scanning Electron Microscopy (SEM) image analysis and [...] Read more.
The porosity of mortars with recycled ceramic aggregates (10, 20, 30, 50, and 100% as a replacement of natural aggregate) was evaluated and analyzed using three different techniques. The results of gas adsorption (N2), Scanning Electron Microscopy (SEM) image analysis and open porosity allowed establishing the relationship between the recycled aggregate content and the porosity of these mortars, as well as the relationship between porosity and the physical and mechanical properties of the mortars: absorption, density, compressive strength, modulus of elasticity, and drying shrinkage. Using the R2 coefficient and the equation typology as criteria, additional data such as Brunauer, Emmett, and Teller (BET) surface area (N2 adsorption) established significant correlations with the mentioned properties; with SEM image analysis, no explanatory relationships could be established; and with open porosity, revealing relationships were established (R2 > 0.9). With the three techniques, it was confirmed that the increase in porosity is related to the increase in the amount of ceramic aggregate; in particular with gas adsorption (N2) and open porosity. It was concluded that the open porosity technique can explain the behavior of these recycled mortars with more reliable data, in a simple and direct way, linked to its establishment with a more representative sample of the mortar matrix. Full article
(This article belongs to the Special Issue Recycled Aggregate Concrete and Alternative Binders for Sustainable Building Engineering)
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13 pages, 2403 KiB  
Article
Influence of Cement Replacement with Fly Ash and Ground Sand with Different Fineness on Alkali-Silica Reaction of Mortar
by Suwat Ramjan, Weerachart Tangchirapat, Chai Jaturapitakkul, Cheah Chee Ban, Peerapong Jitsangiam and Teewara Suwan
Materials 2021, 14(6), 1528; https://doi.org/10.3390/ma14061528 - 20 Mar 2021
Cited by 13 | Viewed by 2318
Abstract
The alkali-silica reaction (ASR) is an important consideration in ensuring the long-term durability of concrete materials, especially for those containing reactive aggregates. Although fly ash (FA) has proven to be useful in preventing ASR expansion, the filler effect and the effect of FA [...] Read more.
The alkali-silica reaction (ASR) is an important consideration in ensuring the long-term durability of concrete materials, especially for those containing reactive aggregates. Although fly ash (FA) has proven to be useful in preventing ASR expansion, the filler effect and the effect of FA fineness on ASR expansion are not well defined in the present literature. Hence, this study aimed to examine the effects of the filler and fineness of FA on ASR mortar expansion. FAs with two different finenesses were used to substitute ordinary Portland cement (OPC) at 20% by weight of binder. River sand (RS) with the same fineness as the FA was also used to replace OPC at the same rate as FA. The replacement of OPC with RS (an inert material) was carried out to observe the filler effect of FA on ASR. The results showed that FA and RS provided lower ASR expansions compared with the control mortar. Fine and coarse fly ashes in this study had almost the same effectiveness in mitigating the ASR expansion of the mortars. For the filler effect, smaller particles of RS had more influence on the ASR reduction than RS with coarser particles. A significant mitigation of the ASR expansion was obtained by decreasing the OPC content in the mortar mixture through its partial substitution with FA and RS. Full article
(This article belongs to the Special Issue Recycled Aggregate Concrete and Alternative Binders for Sustainable Building Engineering)
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13 pages, 4787 KiB  
Article
Influence of Nano-SiO2 on the Mechanical Properties of Recycled Aggregate Concrete with and without Polyvinyl Alcohol (PVA) Fiber
by Shenglin Wang and Baolong Zhu
Materials 2021, 14(6), 1446; https://doi.org/10.3390/ma14061446 - 16 Mar 2021
Cited by 9 | Viewed by 2337
Abstract
In recent years, recycled aggregate concrete (RAC) has become a research hotspot in the field of urban construction because of its resource utilization of construction waste. However, compared with original concrete, its strength is still low, which requires additional nano-SiO2 (NS) and [...] Read more.
In recent years, recycled aggregate concrete (RAC) has become a research hotspot in the field of urban construction because of its resource utilization of construction waste. However, compared with original concrete, its strength is still low, which requires additional nano-SiO2 (NS) and fiber. In order to study the mechanism of strength improvement of RAC, this paper takes NS and polyvinyl alcohol (PVA) fiber as variable parameters; uniaxial and triaxial compression tests were carried out on RAC with PVA fiber and NS, and the mechanical properties of RAC were investigated The result shows that within the range of 3% NS content, an increase in the NS substitution rate causes the mechanical properties of RAC to improve significantly. The compressive strength of RAC increases again after adding PVA fiber; through a SEM (scanning electron microscopy) analysis of the specimen, it was found that the NS filled the micro-pores and micro-cracks in the RAC, and the PVA fiber changed the contact range between recycled aggregate and mortar, so the microstructure of the material was more compact. The mechanism of RAC strength improvement is explained in the microcosmic view. Full article
(This article belongs to the Special Issue Recycled Aggregate Concrete and Alternative Binders for Sustainable Building Engineering)
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