Shielding Effectiveness Measurements of Drywall Panel Coated with Biochar Layers

Shielding against electromagnetic interference (EMI) is a critical issue in civil applications generally solved with metal screens. In recent years, the properties of many composite materials filled with carbon nanotubes or graphene or materials with a carbon-based coating have been analysed with the aim of using them for electromagnetic shielding applications. Among other carbon materials, biochar, derived from biomass and characterized by high carbon content, emerges as a sustainable, renewable, environmentally friendly, and inexpensive material. In this paper, commercial biochar thermally treated at 750 °C is used to coat with several layers common building components such as drywall panel. Shielding effectiveness is measured in the frequency band 1–18 GHz for normal incidence and skew angles 10, 20 and 30 deg in a full anechoic chamber with double ridged, vertically and horizontally polarized broadband horn antennas. The results show that the proposed biochar-coated drywall panels provide a good shielding effectiveness compared to similar solutions, with the advantage of a less expensive and easier to realize building material

A holistic life cycle design approach to enhance the sustainability of concrete structures

The development of innovative cementitious materials such as Ultra High Performance Concrete (UHPC) requires tailored approaches to assess both the environmental and economic impact of structural applications employing them. For this purpose, in this paper, Life Cycle Assessment (LCA) and Life Cycle Cost (LCC) methodologies are integrated into a Durability Assessment-Based Design (DAD) workflow which combines structural design algorithms for UHPC with the assessment of the durability performance, with the aim of predicting the evolution of the structural performance all along the service life (SL) in the intended scenarios. As a case study a water tank made of UHPC has been herein selected and compared to a reference made of Ordinary Reinforced Concrete (ORC). While the ORC solution was designed with cantilever cast in situ walls, two different design concepts were assessed for the UHPC basin: one with cast in situ walls and one with precast slabs supported by ORC columns. Moreover, two different mix designs (mainly differing on the alternative presence of silica fume or slag) have been investigated for the UHPC basin and a SL equal to 50 years has been taken into account for each structure. The optimized design, together with the reduced frequency of the maintenance activities for the UHPC structure, allowed by the UHPC superior material and structural durability, resulted into consistent reductions of environmental impacts, up to 76% as for Human Toxicity and Fresh Water Aquatic Ecotoxicity in comparison to the ORC solution. In addition to this, an assessment of the overall construction and maintenance costs that occur during the lifetime of the structures showed a cost reduction higher than 40% for both UHPC solutions, mainly due to a reduction of up to 6% during the construction phase and 91% for the maintenance activities. This also highlights the importance of the correct metrics in evaluating the sustainability of UHPC structural applications, which has to move forward from the units volume or mass of material and its individual constituents to functional units, represThe development of innovative cementitious materials such as Ultra High Performance Concrete (UHPC) requires tailored approaches to assess both the environmental and economic impact of structural applications employing them. For this purpose, in this paper, Life Cycle Assessment (LCA) and Life Cycle Cost (LCC) methodologies are integrated into a Durability Assessment-Based Design (DAD) workflow which combines structural design algorithms for UHPC with the assessment of the durability performance, with the aim of predicting the evolution of the structural performance all along the service life (SL) in the intended scenarios. As a case study a water tank made of UHPC has been herein selected and compared to a reference made of Ordinary Reinforced Concrete (ORC). While the ORC solution was designed with cantilever cast in situ walls, two different design concepts were assessed for the UHPC basin: one with cast in situ walls and one with precast slabs supported by ORC columns. Moreover, two different mix designs (mainly differing on the alternative presence of silica fume or slag) have been investigated for the UHPC basin and a SL equal to 50 years has been taken into account for each structure. The optimized design, together with the reduced frequency of the maintenance activities for the UHPC structure, allowed by the UHPC superior material and structural durability, resulted into consistent reductions of environmental impacts, up to 76% as for Human Toxicity and Fresh Water Aquatic Ecotoxicity in comparison to the ORC solution. In addition to this, an assessment of the overall construction and maintenance costs that occur during the lifetime of the structures showed a cost reduction higher than 40% for both UHPC solutions, mainly due to a reduction of up to 6% during the construction phase and 91% for the maintenance activities. This also highlights the importance of the correct metrics in evaluating the sustainability of UHPC structural applications, which has to move forward from the units volume or mass of material and its individual constituents to functional units, representative of the benefits of using advanced cement based materials in structurally and environmentally challenging service scenarios. entative of the benefits of using advanced cement based materials in structurally and environmentally challenging service scenarios

Shielding Properties of Cement Composites Filled with Commercial Biochar

The partial substitution of non-renewable materials in cementitious composites with eco-friendly materials is promising not only in terms of cost reduction, but also in improving the composites’ shielding properties. The water and carbon content of a commercial lignin-based biochar is analyzed with thermal gravimetric analysis. Cementitious composite samples of lignin-based biochar with 14 wt.% and 18 wt.% are realized. Good dispersion of the filler in the composites is observed by SEM analysis. The samples are fabricated in order to fit in a rectangular waveguide for measurements of the shielding effectiveness in the X-band. A shielding effectiveness of 15 dB was obtained at a frequency of 10 GHz in the case of composites with 18 wt.% biochar. Full-wave simulations are performed by fitting the measured shielding effectiveness to the simulated shielding effectiveness by varying material properties in the simulator. Analysis of the dimensional tolerances and thickness of the samples is performed with the help of full/wave simulations. Lignin-based biochar is a good candidate for partial substitution of cement in cementitious composites, as the shielding effectiveness of the composites increases substantially

The sustainability profile of a biomimetic 3D printed vascular network to restore the structural integrity of concrete

Among the various possibilities to tackle the issue of concrete damage within its structural service life, the biomimetic approach has favoured the development of innovative solutions such as the use of 3D printed vascular networks suitably incorporated into concrete structural elements to inject and convey the most suitable healing agent upon crack occurrence. These systems, able to cope with damage of different intensities, may lead to improvements of the structure’s durability, through the closure of cracks, and a consequent reduction of the frequency of major maintenance activities. The present work investigates the environmental sustainability of the aforesaid self-healing technology through a Life Cycle Assessment (LCA) analysis. The attention has been also focused on the 3D printing process of the network due to the key role that it could play, in terms of environmental burdens, when upscaled to real-life size applications. The case study of a beam healed by means of polyurethane injected through the network and exposed to a chloride environment is reported to better predict the potential improvements in terms of overall durability and consequent sustainability within the pre-defined service life

Nirmatrelvir treatment of SARS-CoV-2-infected mice blunts antiviral adaptive immune responses

Alongside vaccines, antiviral drugs are becoming an integral part of our response to the SARS-CoV-2 pandemic. Nirmatrelvir-an orally available inhibitor of the 3-chymotrypsin-like cysteine protease-has been shown to reduce the risk of progression to severe COVID-19. However, the impact of nirmatrelvir treatment on the development of SARS-CoV-2-specific adaptive immune responses is unknown. Here, by using mouse models of SARS-CoV-2 infection, we show that nirmatrelvir administration blunts the development of SARS-CoV-2-specific antibody and T cell responses. Accordingly, upon secondary challenge, nirmatrelvir-treated mice recruited significantly fewer memory T and B cells to the infected lungs and mediastinal lymph nodes, respectively. Together, the data highlight a potential negative impact of nirmatrelvir treatment with important implications for clinical management and might help explain the virological and/or symptomatic relapse after treatment completion reported in some individuals

Towards a Conscious and Far-Sighted Construction Market Through the Use of Sustainability Indexes

The ever-changing needs of the end user in the construction industry, together with the increasing awareness about the great influence of the sector on the worldwide sustainability, require some tools to be employed by the stakeholders to drive the market towards conscious and appropriate choices. An example in this regard are advanced cement-based materials that, either by partially replacing cement with supplementary cementitious materials and virgin aggregates with recycled ones or by increasing durability, are generating interest in the market thanks to their potentially better environmental performance. Therefore, besides the sustainability analyses such as the Life Cycle Assessment (LCA) and Life CycleCost (LCC) ones, some recent literature already tackled the problem proposing a more immediate evaluation approach represented by a series of indexeswhich are focused on the ecological and structural (generally, the compressive strength) performance of the material. To this end, from a comprehensive perspective, in this work two indexes are proposed able to include a wider range of environmental performances besides the costs and the durability characteristics. One is aimed to determine the suitability of using certain cementitious materials, encompassing the aforesaid parameters for the cubicmeter scale. A second one is aimed to define the bestmix design to be used to build certain structures (or components). For such purpose, the case of precast panels made with Ultra High Performance Concrete (UHPC) is here addressed, to assess the consistency of such indexes, upgrading from the material scale to the product scale

Biochar-containing construction materials for electromagnetic shielding in the microwave frequency region: the importance of water content

Electromagnetic waves in the X-Band (8.2 – 12.4 GHz frequency) are used for radar, satellite communication, and wireless computer networks. in some countries. Shielding allows to protect humans and electronic devices from harmful effects of these waves. Cement based composites containing conductive material can be used for this purpose., and pyrolyzed carbonaceous residues (biochars) are promising in this respect. Two different biochars originated from wood (CB) and sewage sludge (SSB) pyrolysis were used as fillers in cement-based composites. The electromagnetic shielding properties of these composites have been tested vs the type and amount of biochar added. The influence of water content arising from different curing and ageing in ambient conditions has been investigated for one set of samples. Results show that CB and SSB contain 74% and 30% of graphitic carbon, respectively. In the composites, SSB particles are bulky and scarcely dispersed, while CB particles are elongated and homogenously distributed. High values of Shielding Effectiveness (SE>20 decibel, dB) are achieved at 10 GHz frequency for the composites containing 18% of CB biochar. A large role of ageing was also discovered in sample B18: increasing wet curing increases the shielding effectiveness up to 29 dB, while increasing ageing in air decreases the shielding effectiveness values: after 10 weeks the measured value is about 15 dB. The evidence suggests that the amount of physically adsorbed water is responsible for this behavior, and it should be taken into account when dealing with cement based composites used for electromagnetic shielding

Analysis of shielding effectiveness of cement composites filled with pyrolyzed biochar

Shielding against electromagnetic interference (EMI) is a crucial point in aerospace industry and for civil applications. In recent years, the mechanical and electrical properties of composites materials filled with carbon nanotubes or graphene have been analysed with the aim of substituting to standard metal structures used for electromagnetic shielding. In this work, an eco-friendly material as biochar obtained from biomass pyrolysis is used as filler in cement and the shielding properties of the composite in X-band are analysed

Environmental and economic sustainability of crack mitigation in reinforced concrete with SuperAbsorbent polymers (SAPs)

Due to the increasing awareness and sensitivity towards the environmental and economic sustainability issues, the concrete industry has to deliver innovative solutions, in terms of materials, products and structural concepts, to achieve higher durability of engineering feats in real service scenarios. The inclusion of SuperAbsorbent Polymers (SAPs) into the concrete mix, can not only stimulate the autogenous crack healing, but is also able to reduce the shrinkage cracking through internal curing. In this paper, Life Cycle Assessment (LCA) and Life Cycle Cost (LCC) analysis have been performed to assess both the ecological and economic profile, in real scale, of conventional reinforced concrete structures, made with concrete containing SAPs, in comparison to a reference solution without any addition. For this purpose, the corrosion of reinforcement has been regarded as the main degradation mechanism and different corrosion models have been considered and combined with the structural analysis principles to obtain reliable Service Life (SL) estimations. Four different scenarios, with a SL ranging from 50 up to 100 years, have been analyzed to assess the potential benefits of a wall, cast with SAP-containing concrete (Wall_SAP). Both Wall_SAP and a reference wall without SAP (Wall_Ref) are subjected to the concrete cover replacement as main maintenance activity while for the Wall_Ref also the crack filling by means of polyurethane resin is considered as an option (Wall_Resin). The adopted CML impact-assessment method, developed by the Center of Environmental Science of Leiden University, shows the advantage of using SAPs, since the environmental burdens were reduced up to 20% in the case of Fresh Water Aquatic Ecotoxicity impact category in comparison to the reference for the fourth scenario. In this scenario a hemispherical corrosion pit model for the steel bars and a service life of 100 years were taken into account. Furthermore, the economic assessment developed for the same scenario, pointed out for the SAPs based solution, there identified as Wall_SAP_M2_100, a consistent reduction in terms of costs up to 14% if compared to the reference, there named as Wall_Ref_M2_100. The outcomes definitely highlight the potential of the analyzed technology that can fulfil the future needs of the stakeholders involved in the construction sector