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Special Issue "Recent Advances in Smart Materials for the Built Environment"

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (30 June 2018)

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

Special Issue Editors

Guest Editor
Prof. ing. Cesare Sangiorgi

Department of Civil, Chemical, Environmental and Materials Engineering, University of Bologna, Italy
Website | E-Mail
Interests: pavements; bituminous materials; recyled materials; smart materials
Guest Editor
Prof. Dr. Filippo Ubertini

Department of Civil and Environmental Engineering University of Perugia, Perugia, Italy
Website | E-Mail
Interests: smart concrete; smart bricks; earthquake-induced damage detection; vibration-based SHM; Self-sensing cement-based nanocomposites
Guest Editor
Dr. Anna Laura Pisello

Department of Engineering, University of Perugia, Italy
Website | E-Mail
Interests: energy efficiency in buildings; urban heat island; thermal-energy storage; environmental monitoring; building physics; mitigation; passive cooling; cool roof

Special Issue Information

Dear Colleagues,

The built environment of the future is expected to need novel smart and multifunctional construction materials that provide a variety of other features, in addition to strength and durability. In this view, many researchers worldwide are focusing on the development of such innovative and highly promising solutions with the purpose to enhance the construction material behavior in terms of environmental sustainability and technical performance including the new frontiers of self-sensing, self-healing, energy harvesting, overheating control, noise reduction, microclimate mitigation, and other capabilities.

Society itself will be the first beneficiary of such scientific discussion, since it will take advantage from these characteristics that will allow saving raw materials and energy, minimizing the externalities of construction, service and maintenance phases and impact. Furthermore, those solutions are expected to transform the physical and mechanical behavior of structural and non-structural elements into precious sources of data, renewable energy along with other functional advantages, such as noise and urban overheating reduction.

This Special Issue aims at presenting a number of high-quality up-to-date research contributions that have proven benefits and feasibility of smart materials in the built environment at large. Technical papers, review contributions and case histories on laboratory and in-situ experiments are all welcome. By acknowledging your important contribution in these fields, we would like to warmly invite you to submit a manuscript for consideration in the “Recent Advances in Smart Materials for the Built Environment” Special Issue in Materials.

Prof. ing. Cesare Sangiorgi
Prof. ing. Filippo Ubertini
Prof. ing. Anna Laura Pisello
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 papers will be 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. 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 1800 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

  • Smart materials
  • Self-sensing
  • Energy harvesting
  • Self-healing
  • UHI mitigation
  • Acoustic materials

Published Papers (12 papers)

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Research

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Open AccessArticle
Development of Self-Sensing Textile Strengthening System Based on High-Strength Carbon Fiber
Materials 2018, 11(10), 2062; https://doi.org/10.3390/ma11102062
Received: 26 September 2018 / Revised: 19 October 2018 / Accepted: 20 October 2018 / Published: 22 October 2018
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Abstract
The monitoring of structures is one of the most difficult challenges of engineering in the 21st century. As a result of changes in conditions of use, as well as design errors, many building structures require strengthening. This article presents research on the development [...] Read more.
The monitoring of structures is one of the most difficult challenges of engineering in the 21st century. As a result of changes in conditions of use, as well as design errors, many building structures require strengthening. This article presents research on the development of an externally strengthening carbon-fiber textile with a self-sensing option, which is an idea is based on the pattern of resistive strain gauges, where thread is presented in the form of zig-zagging parallel lines. The first laboratory tests showed the system’s high efficiency in the measurement of strains, but also revealed its sensitivity to environmental conditions. This article also presents studies on the influence of temperature and humidity on the measurement, and to separate the two effects, resistance changes were tested on unloaded concrete and wooden samples. The models were then placed in a climatic chamber, and the daily cycle of temperature and humidity changes was simulated. The research results confirmed preliminary observations of resistivity growths along with temperature. This effect is more visible on concrete samples, presumably due to its greater amount of natural humidity. The strain measurement with carbon fibers is very sensitive to temperature changes, and applications of this method in practice require compensation. Full article
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Open AccessArticle
Mechanical and Thermal Performance of Macro-Encapsulated Phase Change Materials for Pavement Application
Materials 2018, 11(8), 1398; https://doi.org/10.3390/ma11081398
Received: 30 June 2018 / Revised: 27 July 2018 / Accepted: 2 August 2018 / Published: 10 August 2018
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Abstract
Macro-encapsulated phase change material (PCM) lightweight aggregates (ME-LWA) were produced and evaluated for their mechanical and thermal properties in road engineering applications. The ME-LWAs were first characterised in terms of their physical and geometrical properties. Then, the ME-LWAs were investigated in detail by [...] Read more.
Macro-encapsulated phase change material (PCM) lightweight aggregates (ME-LWA) were produced and evaluated for their mechanical and thermal properties in road engineering applications. The ME-LWAs were first characterised in terms of their physical and geometrical properties. Then, the ME-LWAs were investigated in detail by applying the European Standards of testing for the Bulk Crushing Test and the Polished Stone Value (PSV) coefficient as well as Micro-Deval and laboratory profilometry. In addition, the thermal performance for possible construction of smart pavements with the inclusion of ME-LWAs for anti-ice purposes was determined. The crushing resistance of the ME-LWAs was improved, while their resistance to polishing was reduced. Thermal analysis of the encapsulated PCM determined it to possess excellent thermal stability and a heat storage capacity of 30.43 J/g. Based on the research findings, the inclusion of ME-LWAs in surface pavement layers could be considered a viable solution for the control of surface temperatures in cold climates. Road safety and maintenance could benefit in terms of reduced ice periods and reduced treatments with salts and other anti-ice solutions. Full article
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Open AccessFeature PaperArticle
Preliminary Research on the Physical and Mechanical Properties of Alternative Lightweight Aggregates Produced by Alkali-Activation of Waste Powders
Materials 2018, 11(7), 1255; https://doi.org/10.3390/ma11071255
Received: 28 June 2018 / Revised: 18 July 2018 / Accepted: 18 July 2018 / Published: 21 July 2018
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Abstract
There is growing interest in construction field issues related to environmental protection, energy saving and raw materials. Therefore, the interest in recycling waste materials to produce new construction ones is constantly increasing. This study proposes a new methodology to produce lightweight aggregates (LWAs) [...] Read more.
There is growing interest in construction field issues related to environmental protection, energy saving and raw materials. Therefore, the interest in recycling waste materials to produce new construction ones is constantly increasing. This study proposes a new methodology to produce lightweight aggregates (LWAs) by alkali-activation of two different waste powders: a digested spent bentonite clay and a basalt powder. Metakaolin, as secondary precursor, was added to the mixtures according to mix-design proportions, to improve the mechanical properties of the final materials, while a specific activators mix of Sodium Silicate and Sodium Hydroxide enabled the alkali-activation. The expansion process, on the other hand, was obtained using Peroxide within the liquid mix. The experimental LWAs were analyzed and tested in compliance with the EN 13055-1 standard. A more in-depth analysis on LWAs’ air voids content and porosity was also carried out by the means of Mercury Intrusion Porosimetry and Nuclear Magnetic Resonance. The results were compared with those obtained from commercial Lightweight Expanded Clay Aggregate, which represents one of the most common LWAs in the construction field. According to the presented preliminary results, the use of alkali-activated waste powders seems to be a suitable solution for the production of eco-friendly LWAs by allowing the recycling of waste materials and energy saving for their production. Full article
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Open AccessArticle
Effect of PCM on the Hydration Process of Cement-Based Mixtures: A Novel Thermo-Mechanical Investigation
Materials 2018, 11(6), 871; https://doi.org/10.3390/ma11060871
Received: 26 April 2018 / Revised: 15 May 2018 / Accepted: 17 May 2018 / Published: 23 May 2018
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Abstract
The use of Phase Change Material (PCM) for improving building indoor thermal comfort and energy saving has been largely investigated in the literature in recent years, thus confirming PCM’s capability to reduce indoor thermal fluctuation in both summer and winter conditions, according to [...] Read more.
The use of Phase Change Material (PCM) for improving building indoor thermal comfort and energy saving has been largely investigated in the literature in recent years, thus confirming PCM’s capability to reduce indoor thermal fluctuation in both summer and winter conditions, according to their melting temperature and operation boundaries. Further to that, the present paper aims at investigating an innovative use of PCM for absorbing heat released by cement during its curing process, which typically contributes to micro-cracking of massive concrete elements, therefore compromising their mechanical performance during their service life. The experiments carried out in this work showed how PCM, even in small quantities (i.e., up to 1% in weight of cement) plays a non-negligible benefit in reducing differential thermal increases between core and surface and therefore mechanical stresses originating from differential thermal expansion, as demonstrated by thermal monitoring of cement-based cubes. Both PCM types analyzed in the study (with melting temperatures at 18 and 25 C) were properly dispersed in the mix and were shown to be able to reduce the internal temperature of the cement paste by several degrees, i.e., around 5 C. Additionally, such small amount of PCM produced a reduction of the final density of the composite and an increase of the characteristic compressive strength with respect to the plain recipe. Full article
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Open AccessArticle
Self-Healing Capacity of Asphalt Mixtures Including By-Products Both as Aggregates and Heating Inductors
Materials 2018, 11(5), 800; https://doi.org/10.3390/ma11050800
Received: 13 April 2018 / Revised: 4 May 2018 / Accepted: 11 May 2018 / Published: 15 May 2018
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Abstract
Major advances have been achieved in the field of self-healing by magnetic induction in which the addition of metallic particles into asphalt mixtures enables repairing their own cracks. This technology has already been proven to increase the life expectancy of roads. Nevertheless, its [...] Read more.
Major advances have been achieved in the field of self-healing by magnetic induction in which the addition of metallic particles into asphalt mixtures enables repairing their own cracks. This technology has already been proven to increase the life expectancy of roads. Nevertheless, its higher costs in comparison with conventional maintenance caused by the price of virgin metallic particles still makes it unattractive for investment. This research aimed at making this process economically accessible as well as environmentally efficient. To this end, an intense search for suitable industrial by-products to substitute both the virgin metal particles and the natural aggregates forming asphalt mixtures was conducted. The set of by-products used included sand blasting wastes, stainless shot wastes, and polished wastes as metallic particles and other inert by-products as aggregates. The results demonstrated that the by-products were adequately heated, which leads to satisfactory healing ratios in comparison with the reference mixture. Full article
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Open AccessArticle
Smart Metamaterial Based on the Simplex Tensegrity Pattern
Materials 2018, 11(5), 673; https://doi.org/10.3390/ma11050673
Received: 20 February 2018 / Revised: 8 April 2018 / Accepted: 23 April 2018 / Published: 26 April 2018
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Abstract
In the present paper, a novel cellular metamaterial that was based on a tensegrity pattern is presented. The material is constructed from supercells, each of which consists of eight 4-strut simplex modules. The proposed metamaterial exhibits some unusual properties, which are typical for [...] Read more.
In the present paper, a novel cellular metamaterial that was based on a tensegrity pattern is presented. The material is constructed from supercells, each of which consists of eight 4-strut simplex modules. The proposed metamaterial exhibits some unusual properties, which are typical for smart structures. It is possible to control its mechanical characteristics by adjusting the level of self-stress or by changing the properties of structural members. A continuum model is used to identify the qualitative properties of the considered metamaterial, and to estimate how the applied self-stress and the characteristics of cables and struts affect the whole structure. The performed analyses proved that the proposed structure can be regarded as a smart metamaterial with orthotropic properties. One of its most important features are unique values of Poisson’s ratio, which can be either positive or negative, depending on the applied control parameters. Moreover, all of the mechanical characteristics of the proposed metamaterial are prone to structural control. Full article
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Open AccessArticle
An Innovative Approach to Control Steel Reinforcement Corrosion by Self-Healing
Materials 2018, 11(2), 309; https://doi.org/10.3390/ma11020309
Received: 29 January 2018 / Revised: 11 February 2018 / Accepted: 12 February 2018 / Published: 20 February 2018
Cited by 1 | PDF Full-text (5152 KB) | HTML Full-text | XML Full-text
Abstract
The corrosion of reinforced steel, and subsequent reinforced concrete degradation, is a major concern for infrastructure durability. New materials with specific, tailor-made properties or the establishment of optimum construction regimes are among the many approaches to improving civil structure performance. Ideally, novel materials [...] Read more.
The corrosion of reinforced steel, and subsequent reinforced concrete degradation, is a major concern for infrastructure durability. New materials with specific, tailor-made properties or the establishment of optimum construction regimes are among the many approaches to improving civil structure performance. Ideally, novel materials would carry self-repairing or self-healing capacities, triggered in the event of detrimental influence and/or damage. Controlling or altering a material’s behavior at the nano-level would result in traditional materials with radically enhanced properties. Nevertheless, nanotechnology applications are still rare in construction, and would break new ground in engineering practice. An approach to controlling the corrosion-related degradation of reinforced concrete was designed as a synergetic action of electrochemistry, cement chemistry and nanotechnology. This contribution presents the concept of the approach, namely to simultaneously achieve steel corrosion resistance and improved bulk matrix properties. The technical background and challenges for the application of polymeric nanomaterials in the field are briefly outlined in view of this concept, which has the added value of self-healing. The credibility of the approach is discussed with reference to previously reported outcomes, and is illustrated via the results of the steel electrochemical responses and microscopic evaluations of the discussed materials. Full article
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Open AccessArticle
Poly(hydroxyalkanoate)s-Based Hydrophobic Coatings for the Protection of Stone in Cultural Heritage
Materials 2018, 11(1), 165; https://doi.org/10.3390/ma11010165
Received: 4 December 2017 / Revised: 11 January 2018 / Accepted: 17 January 2018 / Published: 20 January 2018
Cited by 8 | PDF Full-text (7053 KB) | HTML Full-text | XML Full-text
Abstract
Reversibility is a mandatory requirement for materials used in heritage conservation, including hydrophobic protectives. Nevertheless, current protectives for stone are not actually reversible as they remain on the surfaces for a long time after their hydrophobicity is lost and can hardly be removed. [...] Read more.
Reversibility is a mandatory requirement for materials used in heritage conservation, including hydrophobic protectives. Nevertheless, current protectives for stone are not actually reversible as they remain on the surfaces for a long time after their hydrophobicity is lost and can hardly be removed. Ineffective and aged coatings may jeopardise the stone re-treatability and further conservation interventions. This paper aims at investigating the performance of PHAs-based coatings for stone protection, their main potential being the ‘reversibility by biodegradation’ once water repellency ended. The biopolymer coatings were applied to three different kinds of stone, representative of lithotypes used in historic architecture: sandstone, limestone and marble. Spray, poultice and dip-coating were tested as coating techniques. The effectiveness and compatibility of the protectives were evaluated in terms of capillary water absorption, static and dynamic contact angles, water vapour diffusion, colour alteration and surface morphology. The stones’ wettability after application of two commercial protectives was investigated too, for comparison. Finally, samples were subjected to artificial ageing to investigate their solar light stability. Promising results in terms of efficacy and compatibility were obtained, although the PHAs-based formulations developed here still need improvement for increased durability and on-site applicability. Full article
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Open AccessArticle
Study of the Thermal Properties and the Fire Performance of Flame Retardant-Organic PCM in Bulk Form
Materials 2018, 11(1), 117; https://doi.org/10.3390/ma11010117
Received: 27 October 2017 / Revised: 29 December 2017 / Accepted: 29 December 2017 / Published: 12 January 2018
Cited by 2 | PDF Full-text (1772 KB) | HTML Full-text | XML Full-text
Abstract
The implementation of organic phase change materials (PCMs) in several applications such as heating and cooling or building comfort is an important target in thermal energy storage (TES). However, one of the major drawbacks of organic PCMs implementation is flammability. The addition of [...] Read more.
The implementation of organic phase change materials (PCMs) in several applications such as heating and cooling or building comfort is an important target in thermal energy storage (TES). However, one of the major drawbacks of organic PCMs implementation is flammability. The addition of flame retardants to PCMs or shape-stabilized PCMs is one of the approaches to address this problem and improve their final deployment in the building material sector. In this study, the most common organic PCM, Paraffin RT-21, and fatty acids mixtures of capric acid (CA), myristic acid (MA), and palmitic acid (PA) in bulk, were tested to improve their fire reaction. Several flame retardants, such as ammonium phosphate, melamine phosphate, hydromagnesite, magnesium hydroxide, and aluminum hydroxide, were tested. The properties of the improved PCM with flame retardants were characterized by thermogravimetric analyses (TGA), the dripping test, and differential scanning calorimetry (DSC). The results for the dripping test show that fire retardancy was considerably enhanced by the addition of hydromagnesite (50 wt %) and magnesium hydroxide (50 wt %) in fatty acids mixtures. This will help the final implementation of these enhanced PCMs in building sector. The influence of the addition of flame retardants on the melting enthalpy and temperatures of PCMs has been evaluated. Full article
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Open AccessArticle
Self-Sealing Cementitious Materials by Using Water-Swelling Rubber Particles
Materials 2017, 10(8), 979; https://doi.org/10.3390/ma10080979
Received: 25 July 2017 / Revised: 15 August 2017 / Accepted: 18 August 2017 / Published: 22 August 2017
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Abstract
Water ingress into cracked concrete structures is a serious problem, as it can cause leakage and reinforcement corrosion and thus reduce functionality and safety of the structures. In this study, the application of water-swelling rubber particles for providing the cracked concrete a self-sealing [...] Read more.
Water ingress into cracked concrete structures is a serious problem, as it can cause leakage and reinforcement corrosion and thus reduce functionality and safety of the structures. In this study, the application of water-swelling rubber particles for providing the cracked concrete a self-sealing function was developed. The feasibility of applying water-swelling rubber particles and the influence of incorporating water-swelling rubber particles on the mechanical properties of concrete was investigated. The self-sealing efficiency of water-swelling rubber particles with different content and particle size was quantified through a permeability test. The sealing effect of the water swelling rubber particles was monitored by X-ray computed tomography. The experimental results show that, by using 6% of these water swelling rubber particles as a replacement of aggregates in concrete, up to 64% and 61% decrease of water permeability was realized for 0.7 mm and 1.0 mm cracks. Furthermore, when the concrete cracks, the water swelling rubber particles can act as a crack bridging filler, preventing the crack from fully separating the specimens in two pieces. Full article
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Review

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Open AccessReview
Smart Crack Control in Concrete through Use of Phase Change Materials (PCMs): A Review
Materials 2018, 11(5), 654; https://doi.org/10.3390/ma11050654
Received: 3 April 2018 / Revised: 17 April 2018 / Accepted: 19 April 2018 / Published: 24 April 2018
Cited by 9 | PDF Full-text (15787 KB) | HTML Full-text | XML Full-text
Abstract
Cracks in concrete structures present a threat to their durability. Therefore, numerous research studies have been devoted to reducing concrete cracking. In recent years, a new approach has been proposed for controlling temperature related cracking—utilization of phase change materials (PCMs) in concrete. Through [...] Read more.
Cracks in concrete structures present a threat to their durability. Therefore, numerous research studies have been devoted to reducing concrete cracking. In recent years, a new approach has been proposed for controlling temperature related cracking—utilization of phase change materials (PCMs) in concrete. Through their ability to capture heat, PCMs can offset temperature changes and reduce gradients in concrete structures. Nevertheless, they can also influence concrete properties. This paper presents a comprehensive overview of the literature devoted to using PCMs to control temperature related cracking in concrete. First, types of PCMs and ways of incorporation in concrete are discussed. Then, possible uses of PCMs in concrete technology are discussed. Further, the influences of PCMs on concrete properties (fresh, hardened, durability) are discussed in detail. This is followed by a discussion of modelling techniques for PCM-concrete composites and their performance. Finally, a summary and the possible research directions for future work are given. This overview aims to assure the researchers and asset owners of the potential of this maturing technology and bring it one step closer to practical application. Full article
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Other

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Open AccessErratum
Erratum: Andreotti, S.; Franzoni, E.; Fabbri, P. Poly(hydroxyalkanoate)s-Based Hydrophobic Coatings for the Protection of Stone in Cultural Heritage. Materials 2018, 11, 165
Materials 2018, 11(3), 389; https://doi.org/10.3390/ma11030389
Received: 28 February 2018 / Revised: 2 March 2018 / Accepted: 2 March 2018 / Published: 7 March 2018
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Abstract
The authors wish to add a new author, Micaela Degli Esposti, who also contributed to performing the experiments and analyzing the data of this published paper [1]. [...] Full article
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