Improvement Of Thermal Insulation Research Articles

Physical and Mechanical Properties of Autoclaved Aerated Concrete (AAC) with Ceramic and Gypsum Waste (CGW) Addition Before and After Exposure to Direct Fire at Temperatures up to 920°C

This research endeavors to comprehensively explore the physical and mechanical properties of Autoclaved Aerated Concrete (AAC) with ceramic and gypsum waste (CGW) addition before and after exposure to direct fire at temperatures up to 920°C. The investigation focuses on determining the effects of CGW addition on AAC properties before and after exposure to direct fire at temperatures reaching 920℃ for 300 seconds. The main objective of this research was to determine the work density and compressive strength of AAC-CGW on the surface of direct fire exposure. In pursuit of this goal, various compositions of AAC with CGW, ranging from 5% to 30% wt/wt, were accurately prepared. The physical and mechanical were conducted before and after subjecting to direct fire testing. Important parameters such as work density, ranging from 593.71kg/m3 to 672.70kg/m3, and compressive strength from 1.64MPa to 2.39MPa, were analyzed. The findings demonstrated that the compressive strength exhibited an increase with CGW addition, particularly within the 5% wt/wt. The high point compressive strength value recorded was 2.39MPa for a 5% wt/wt CGW addition, reflecting a 45.73% increase in compressive strength compared to the reference sample (RS). The study also revealed convincing fire resistance results. Indicating for the reference sample (RS), the samples exhibited surfaces devoid of cracks, burns, or melting during direct fire exposure exceeding 920℃ for 300 seconds. Furthermore, CGW addition contributed to a remarkable 20.1% improvement in thermal insulation compared to the RS. Direct fire resistance testing had a positive influence on the physical and mechanical characteristics of AAC-CGW samples. The average work density experienced a 9.9% reduction, while compressive strength exhibited an 18.8% increase. Direct fire exposure led to an outstanding 53.30% enhancement in compressive strength compared to the sample.

Advancing sustainable molded packaging: Integrating silica aerogel into recycled paper pulp for the fabrication of thermally and mechanically stable superhydrophobic composites

In recent years, the growing demand for sustainable packaging has significantly fueled the quest to explore novel approaches that enhance the applicability of renewable alternatives. This study leverages the unique properties of silica aerogel (SA) to address the limitations of traditional molded pulp products. By integrating SA into recycled paper pulp (RP), we aimed to improve water resistance, thermal stability, and mechanical properties. Composites were prepared with varying SA concentrations (1–10 %). Contact angle measurements showed enhanced hydrophobicity, with RP/SA3 % achieving a contact angle of 152.09°, compared to 122.39° for neat RP. The tensile index (TI) of RP/SA composites with 3 % SA increased by 21.09 % compared to neat RP, indicating better mechanical strength. Thermal conductivity significantly decreased, with RP/SA10 % reducing from 0.155 W m−1·K−1 in neat RP to 0.088 W m−1·K−1, a 43.2 % improvement in thermal insulation. Additionally, composites with 1 % and 3 % SA maintained high biodegradability, showing over 50 % degradation after six weeks in soil. These results suggest that incorporating SA into RP composites enhances their functionality without compromising biodegradability, offering a promising solution for sustainable packaging. As regulatory bodies emphasize resource management and waste reduction, the potential of these innovative and environmentally friendly packaging solutions becomes increasingly significant.

Thermal and energy efficiency in 3D-printed buildings: Review of geometric design, materials and printing processes

Applying 3D printing in construction is a promising, sustainable alternative to conventional methods. However, the thermal and energy performance of 3D-printed buildings remains underexplored, particularly regarding the interactions between geometric design, material selection, and printing parameters. This review addresses this gap by critically examining how the main steps of the printing process impact the thermal efficiency of 3D-printed buildings. Key findings indicate that material development needs to focus on mixes that balance thermal properties,printability,and structural integrity. The review demonstrates how optimising wall cross-sections and cavity shapes can reduce thermal conductivity and enhance energy efficiency. Innovative geometric designs, such as cellular and honeycomb structures, have shown improvements in thermal insulation. Optimising printing parameters, such as extrusion rate and nozzle travel speed, is crucial to minimising thermal bridges and reducing material anisotropy. Advanced numerical models, validated by experimental data and incorporating factors like inhomogeneous porosity, anisotropy, and surface roughness, are essential for accurately predicting the thermal behaviour of 3D-printed structures. The review underscores the need for large-scale, long-term performance studies of 3D-printed buildings under diverse climatic conditions. Additionally, developing standardised fabrication protocols and testing methods is essential for ensuring consistent quality and broader adoption. Addressing these research gaps is crucial to fully realising the potential of 3D printing in sustainable construction and accelerating the adoption of additive manufacturing in the construction sector.

USE OF A TWO-STAGE COMBINED SCHEME FOR HEAT EXCHANGERS CONNECTION IN HEATING POINTS FOR HOT WATER SUPPLY OF INSULATED BUILDINGS

The article addresses the features of the functioning of centralised heat supply systems of residential micro-districts considering the improvement of thermal insulation of existing buildings. It also analyses the performance characteristics of hot water supply heaters installed on individual heat points of insulated buildings. The authors compared the heat transfer surface area of heaters and network water flow rate through the heating point for one-stage and two-stage combined schemes of connection of heat exchangers and heat networks. The analysis of calculation results showed that using a two-stage combined connection scheme reduces the consumption of network water through the individual heat supply unit compared to the one-stage scheme. However, the two-stage scheme causes the necessity to increase the heat transfer surface area compared to the one-stage connection scheme. We generalised the results by formulas for calculating water flow rate from distribution heat networks and heat transfer surface area. It is possible to use the obtained results to develop a strategy for reforming micro-district centralised heating systems. Using a two-stage combined connection scheme for hot water supply heat exchangers installed on individual heating points (IHP) of additionally insulated buildings reduces network water consumption through the individual heating point by 8–16% compared to a one-stage connection scheme. The device of a two-stage combined scheme in comparison with a one-stage scheme causes the increase of heat transfer surface area of heat exchangers of the hot water supply of individual heating points from one and a half to two times depending on the accepted design temperature of heating of cold water at the first stage of the heating unit. The results of calculations are approximated by equations, allowing, with acceptable accuracy, to compare the indicators of two-stage combined and one-stage schemes of connection of water heaters for individual heating points of insulated buildings. Keywords: centralised heat supply, individual heating point, water heaters, hot water supply.

Controlling the Size of Hydrotalcite Particles and Its Impact on the Thermal Insulation Capabilities of Coatings.

This study focuses on the development of high-performance insulation materials to address the critical issue of reducing building energy consumption. Magnesium-aluminum layered double hydroxides (LDHs), known for their distinctive layered structure featuring positively charged brucite-like layers and an interlayer space, have been identified as promising candidates for insulation applications. Building upon previous research, which demonstrated the enhanced thermal insulation properties of methyl trimethoxysilane (MTS) functionalized LDHs synthesized through a one-step in situ hydrothermal method, this work delves into the systematic exploration of particle size regulation and its consequential effects on the thermal insulation performance of coatings. Our findings indicate a direct correlation between the dosage of MTS and the particle size of LDHs, with an optimal dosage of 4 wt% MTS yielding LDHs that exhibit a tightly interconnected hydrotalcite lamellar structure. This specific modification resulted in the most significant improvement in thermal insulation, achieving a temperature difference of approximately 25.5 °C. Furthermore, to gain a deeper understanding of the thermal insulation mechanism of MTS-modified LDHs, we conducted a thorough characterization of their UV-visible diffuse reflectance and thermal conductivity. This research contributes to the advancement of LDH-based materials for use in thermal insulation applications, offering a sustainable solution to energy conservation in the built environment.

Rational design of high‐performance epoxy/expandable microsphere foam with outstanding mechanical, thermal, and dielectric properties

AbstractPrevious studies on epoxy foams were subjected to the specific property, and improvements in thermal insulation or dielectric property were usually accompanied by the sacrifice of mechanical strength or thermal stability. The current research reported a high‐performance epoxy foam by the pre‐curing process using E‐51/DDS and expandable microsphere (EMP) as polymer matrix and physical blowing agent, respectively. The effect of EMP loading on the structure & property of epoxy foam was reported. The mean diameter of E‐51/EMP foam was in the range of 19–21 μm. The compression property of E‐51/EMP foam was fit for the power‐law model and its integrity was well maintained during compressive test. Compared with bulky epoxy, a significant decrease of thermal conductivity of 62.93% was observed in 10 wt% EMP‐filled epoxy foam. E‐51/EMP foam showed superior thermal stabilities, with a T5% of over 300°C. The dielectric constant was decreased by 54.5% from 4.92 in bulky epoxy to 2.24 in E‐51/EMP foam (10 wt% EMP). Notably, there was a percolation phenomenon of EMP (6 wt%) regarding on the structure & property of E‐51/EMP foam. This study provides lightweight, robust, high‐temperature‐resistant, and low‐dielectric‐constant epoxy foams with the wide application prospects in buoyant, electronic packaging, and energy‐saving industries.

Method of arrangement of internal thermal insulation of external protective structures of the room

This article aims to discuss the conditions of insulation and avoidance of moisture condensation in the enclosing structures of buildings whose facades cannot be insulated from the outside due to historical and cultural value. The paper presents a study of the energy-efficient design of the facade of a residential building, which uses insulating materials that are suitable for internal thermal insulation of historical buildings. The analysis of domestic and European literary sources regarding the improvement of the level of thermal protection of buildings shows that the improvement of energy efficiency is important for ensuring a sustainable, affordable and safe energy system. The paper presents the results of a study aimed at increasing energy efficiency in residential buildings, as well as an analysis of the humidity state and the possibility of condensation when using internal insulation. Numerical simulations were performed to confirm the results. The obtained results indicate that the use of mineral insulation "BETOL®" and aluminium foil as a vapour barrier, applied from the inside, contributes to the improvement of thermal insulation of the walls and reduces the risks of condensation. Computer simulations have shown that under the considered conditions, condensation does not occur. The relative humidity in the structure does not reach 90%. The same structure without the vapour barrier causes condensation because the relative humidity exceeds 100 % in whole thickness of the brickwork, which will cause destruction of the historical structure. This research makes an important contribution to the development of energy-efficient solutions for the construction industry, as it will ensure the minimum permissible value of the heat transfer resistance of the enclosing structures and extend the service life of them and buildings as a whole.

METHOD OF ARRANGEMENT OF INTERNAL THERMAL INSULATION OF EXTERNAL PROTECTIVE STRUCTURES OF THE ROOM

The paper presents the results of a study aimed at increasing energy efficiency in residential buildings, as well as an analysis of the humidity state and the possibility of condensation when using internal insulation. Numerical simulations were performed to confirm the results. The obtained results indicate that the use of mineral insulation "BETOL®" and aluminum foil used as a vapor barrier, applied from the inside, contributes to the improvement of thermal insulation of the walls and reduces the risks of condensation. Computer modeling showed that under the formed conditions, condensation is not observed. This research has an important contribution to the development of energy-efficient solutions for the construction industry, as it allows to ensure the minimum permissible value of heat transfer resistance of external enclosures, to extend their service life.

Analysis of Mechanical and Thermal Performance and Environmental Impact of Flax-Fiber-Reinforced Gypsum Boards

Gypsum board is a building material known for its various qualities and functional characteristics, including its low density, fire resistance, thermal insulation, moisture regulation, and decorative appeal. However, it is important to consider the environmental aspects, as the production of one ton of gypsum board releases approximately 355 kg of CO2 into the atmosphere. This research aims to reduce the carbon footprint while improving the mechanical and thermal properties of gypsum boards. To achieve this objective, flax fibers of three different lengths (12 mm, 24 mm, and 36 mm) were used to replace gypsum at a certain volume fraction. Incorporating up to 10% flax fiber effectively offsets the carbon footprint of gypsum boards. However, practical constraints related to the processing conditions and mechanical strength limited the addition of flax fiber to levels of 1%, 2%, and 3%. A 3% fiber incorporation gave us a more homogeneous mix with good workability, ensuring good mechanical performance and a 29% reduction in the carbon footprint. This study showed an improvement in flexural strength for flax-fiber-reinforced composites regardless of their length. In particular, the addition of 3% flax fiber (36 mm in length) showed the most significant increase in flexural strength, exceeding 438%. In addition, the mechanical behavior, including toughness, showed improvements over unreinforced gypsum. Flax fibers were found to be effective in bridging microcracks and limiting their propagation. Notably, all reinforced composites showed a decrease in thermal conductivity, resulting in a 47% improvement in thermal insulation with the addition of flax fibers.

Valorising cassava pomace biosolid in fired clay bricks production: Physical, mechanical and thermal evaluation

In this study, the practicability of recovering cassava pomace biosolids (CPB) for use as pore forming materials in fired clay bricks was examined. The raw materials were characterized for their chemical, mineral and thermal properties and found suitable for fired clay brick production. Modelled test brick samples containing up to 15% CPB were fabricated and fired at 900 and 1000 °C. Apparent porosity increased from 31.2% to 48.6% at 900 °C. Bulk density reduced from 1.97 g/cm3 to 1.58 g/cm3 at 1000 °C during firing with the progressive introduction of CPB in the brick bodies. Water absorption values of bricks fired at 1000 °C ranged between 10.80% and 28.82%. Compressive strengths of bricks declined from 20.01 MPa to 6.3 MPa at 900 °C firing. However, this decline was compensated with an over 30% improvement in thermal insulation as thermal conductivities reduced from 0.84 W/mK to 0.54 W/mK. Phase analysis evidenced kaolinite transformation into metakaoline and mullite, geothite dehydroxylation into hematite and the formation of wollastonites in the fired brick samples. Morphological analysis of CB-15 brick series showed significant differentials in terms of the nature of pores developed and clay vitrification due to changes in firing temperatures. Overall, CB-10 brick series was considered suitable for load supporting structural construction whereas CB-15 were most apt for thermal insulation walling construction. Consequently, by adjusting the CPB content within 2.5–15 wt% in the bricks’ bodies, the produced bricks could be applicable to a wide spectrum of construction applications.

Durability of Raw Earth Blocks Reinforced with Wheat Straw Fibers

The key drivers of the growing interest in the recovery of local materials, particularly land and waste plants, are low-cost building materials, thermal comfort, decreased energy consumption, and decreased carbon dioxide polluting emissions. This work's primary objective is to test a bio-sourced composite material that takes the form of a block of unfinished soil that has been stabilized with cement and blended with wheat straw. This study is being done with the objective of examining the impact of this fiber at different weight percentages (0, 2, 3%, and 4%) on the mechanical behavior, durability, and thermophysical properties of the produced blocks. The results obtained indicated an increase in thermal conductivity, from 2.75 W/mK for the blocks without wheat straw fiber to 0.398 W/mK for those getting 4% of the wheat straw fiber, signifying an improvement in thermal insulation. While retaining the low performance threshold required by the earth construction standard, this improvement was accompanied by an average decrease in mechanical performance.

Synthesis and characterization of fiber-reinforced lightweight foamed phosphogypsum-based composite

A foamed phosphogypsum-based composite (FPGC) was synthesized in this study via chemical foaming and the effect of hydrogen peroxide (H2O2) (0.5% to 2.5%) on its properties was investigated. With the increasing dosage of H2O2, more foamed pores were produced, causing a decline in the mechanical strength and water resistance of mixtures. Nonetheless, the increased pores resulted in an improvement in thermal insulation and acoustic absorption. Fiber addition resulted in slight enhancement in the acoustic absorption and thermal conductivity but significantly improved the mechanical strength and water resistance of fiber-reinforced FPGC, particularly polyvinyl alcohol (PVA) fiber. The calcium stearate (CS) (5% to 25%) as foam stabilizer was also incorporated to ascertain its effect on the properties of FPGC. CS content exceeding 15% had a positive effect on the properties of fiber-reinforced FPGC. Finally, the fiber-reinforced FPGC with 1% PVA fiber, 1.5% H2O2, and 20% CS attained a bulk density of 826 kg/m3, compressive strength of 5.08 MPa, softening coefficient of 0.69, and improved sound absorption and thermal conductivity of 0.483, and 0.221 W/m·K, respectively. This study presents a promising approach for the utilization of phosphogypsum (PG), and further works can be explored to evaluate the long-term performance and durability of FPGC in various environmental conditions.

Thermophysical Properties of Sawdust and Coconut Coir Dust Incorporated Unfired Clay Blocks

Sawdust and coconut coir dust are agro-wastes/by-products which are suitable for use as raw materials to manufacture unfired clay blocks due to their excellent physical and mechanical properties. A limited number of studies have been conducted on the utilisation of these agro-wastes in clay block production, and they have mostly been devoted to investigating the physicomechanical properties, with less attention given to the thermal properties. Moreover, the majority of the studies have used chemical binders (cement and lime) in combination with agro-waste, thus increasing the carbon footprint and embodied energy of the samples. Furthermore, no research has been performed on the thermal performance of these agro-wastes when incorporated into clay blocks at the wall scale. Therefore, to address these limitations, the present study developed unfired clay blocks incorporating sawdust and coconut coir dust (0, 2.5, 5, and 7.5% by weight), without the use of chemical binders, and evaluated their thermal performance, both at the individual and wall scales. The experiments were divided into two phases. In the first phase, individual sample blocks was tested for basic thermal properties. Based on the results of the first phase, small walls with dimensions of 310 mm × 215 mm × 100 mm were built in the second phase, using the best performing mixture from each waste type, and these were assessed for thermal performance using an adapted hot box method. The thermal performance of the walls was evaluated by measuring the heat transfer rate from hot to cold environments and comparing the results to the reference wall. The results showed that thermal conductivity decreased from 0.36 W/mK for the reference sample, to 0.19 W/mK for the 7.5% coconut coir dust sample, and 0.21 W/mK for the 7.5% sawdust sample, indicating an improvement in thermal insulation. Furthermore, the coconut coir dust and sawdust sample walls showed a thermal resistance improvement of around 48% and 35%, respectively, over the reference sample wall. Consequently, the findings of this study will provide additional essential information that will help in assessing the prospective applications of sawdust and coconut coir dust as the insulating material for manufacturing unfired clay blocks.

Dynamic modelling and thermoeconomic analysis for the energy refurbishment of the Italian building sector: Case study for the “Superbonus 110 %” funding strategy

• Development of a dynamic model simulating the thermal load for space heating of a building located in different weather zones. • Analysis of the thermostatic valve control applied to the emitters of the heating system. • Analysis of the refurbishment solutions applied in several combinations to the buildings considered. • The dynamic analysis of the CO2 heat pump reveals interesting perspective for the energy transition scenarios. • The thermoeconomic analysis shows a great economic profitability when the “Superbonus 110%” incentive is considered. The refurbishment of the building sector is a relevant issue in several Countries, such as Italy, where the poor energy performance of residential buildings dramatically affects the overall primary energy consumption and the related emissions of CO 2 . Such buildings are featured by a significantly poor efficiency of the conventional centralized boilers and by a scarce thermal insulation of the envelope. Therefore, the use of renewable technologies, as the solar ones, may significantly reduce the environmental impact of such residential buildings. Moreover, the use of modern and highly efficient boilers is crucial to reduce the primary energy consumption. The combination of these solutions along with the improvement of thermal insulation of the building envelope seems very promising to enhance the energy performance of existing residential buildings. In particular, this work proposes the integration of a CO 2 heat pump to replace a conventional gas-fired boiler. This solution aims to be suitable for the Italian economic funding policy, known as “ Superbonus 110%”, where some specific energy refurbishment actions are fully funded by the Government. In the layout presented in this paper, the existing radiators are supplied by a new CO 2 heat pump, since its high outlet temperature is very close to the boiler one. Furthermore, the thermal insulation of the building envelope and the use of photovoltaic panels are also considered in combination with the CO 2 heat pump. In this work, the dynamic, monthly, and annual results of the carried out dynamic simulations are then presented and discussed. The optimal solution of the proposed layout is detected by means of a detailed sensitivity analysis which considers different weather zones. The energy and environmental analyses show that the CO 2 heat pump coupled with all the other solutions leads to a reduction of the primary energy consumption by 52% and a total CO 2 emission savings of 49%. The Italian incentive is considered in the economic analysis and results show a Net Present Value of the investment of roughly 27 k€, considering a lifespan of 25 years.

Thermo-physical and mechanical characterization of cement-based mortar incorporating spent tea

The use of biomass waste and plant fibers as aggregates for traditional binders has proven to be a green promising solution for reducing the overall energy consumption and carbon dioxide emissions related to the construction sector. Most research on plant-based additives reported an improvement in thermal insulation at the expense of mechanical strength. Thus, balancing the thermo-mechanical properties is a key to produce innovative insulating materials. In this work, the potential use of Spent Tea (ST) in the manufacturing of bio-sourced cement-based mortars was studied. Different weight ratios ranging of 0–10% were used to evaluate the influence of ST content on the cement performance. Thermal, mechanical, and physical properties of the produced bio-composites were characterized. The results showed that increasing ST content leads to a significant decrease in thermal conductivity (67%), thermal diffusivity (57%), density (24%), and compressive strength (97%). At last, it was found that adding up to 2.5 wt% ST meets the structural requirements of lightweight concretes (>3.5 MPa) and could be used for wall structures. However, the composite incorporating 7.5 wt% of ST should exclusively serve for insulation purposes.

Improvement of thermal insulation and compressive performance of Al2O3–SiO2 aerogel by doping carbon nanotubes

Carbon nanotubes (CNTs) have attracted significant attention from researchers due to their high specific strength and good extinction properties. In this study, Al2O3–SiO2 aerogel composites doped with 0–1.0 wt% CNTs were prepared by sol-gel and supercritical drying technologies, and the effects of CNT content on their microstructure, mechanical properties, heat insulation properties, and theoretical thermal conductivity were examined. With an increase in the CNT amount, the specific surface area and pore diameter of the aerogel composites decreased, while their compressive properties were enhanced. The obtained results revealed that the 1.0 wt% CNT-doped Al2O3–SiO2 aerogel composite exhibited the best comprehensive properties, while its thermal conductivity of 0.178 W/mK at 1000 °C was 15% lower than that of pure aerogel. In addition, the theoretical thermal conductivities of all samples were calculated in the temperature range of 25–1000 °C. This study explained that the addition of CNTs can significantly improve the comprehensive properties of Al2O3–SiO2 aerogel composites.

How Gas-Solid Interaction Matters in Graphene-Doped Silica Aerogels.

It was interesting to experimentally find that the thermal insulation of silica aerogels was improved by doping graphene sheets with high heat conductivity. The underlying mechanism is investigated in the present work from the perspective of gas-solid interaction using a comprehensive analysis of molecular dynamics (MD) simulations, theoretical modeling, and experimental data. The MD-modeled small pores are demonstrated to effectively represent big pores in silica aerogels because of similar heat conduction physics, because it is found that adsorption does not contribute to gas heat conduction. Meanwhile, based on the experimentally measured density, the porous structures are schematically re-engineered using molecular modeling for the first time. The evaluated pore size distributions numerically present a consistency with available experimental data. Inspired by the visualization of the 3D pore structure, we proposed a graphene/silica/nitrogen model to evaluate the role of graphene in heat conduction: it can not only reduce effective gas collision (impede heat transport) but also enhance the gas-solid coupling effect. The former is dominant because of the high porosity, leading to an improvement in thermal insulation. The competition between them can be the reason for the "trade-off" phenomenon in the graphene doping effect in the available experiment.

Improvement of insulation properties of glass fiber fabric/epoxy composites modified by polymeric and inorganic fillers

AbstractGlass fiber fabric‐reinforced epoxy composites (GEC) have some weakness on both thermal insulation and sound absorption insulation, which are very important for many application areas such as aircraft, train, and so on. The main aim of this study is to improve both sound absorbent and thermal insulation properties of GEC by incorporating different fillers such as hollow glass microspheres (HGMs), polystyrene (PS) microfiber membrane, and PS solution. Results show that incorporation of PS solution into glass fiber fabric epoxy composite (GEC‐PS) provides higher sound absorption coefficient leading to an increase in the max SAC value from 0.1 to 0.4 and improvement in thermal insulation by decrease of thermal conductivity coefficient of GEC from 0.48 to 0.448 W/mK. Thermal insulation properties of GEC were improved by the use of PS microfiber membrane, which decreases the thermal conductivity coefficient of GEC from 0.48 to 0.438 W/mK. HGM did not improve both the thermal insulation and sound absorption insulation properties of GEC due to the agglomeration.

Coffee biowaste valorization within circular economy: an evaluation method of spent coffee grounds potentials for mortar production

PurposeSpent coffee grounds (SCG) are biowastes extensively generated within the coffee supply chain. Nowadays, their disposal represents an increasing environmental concern due to its toxicity and organic nature. With the estimated increase of coffee production and consumption in the upcoming years, there is an imperative need to find a proper reverse option, along with a novel industrial application, which allows for the valorization of this coffee by-product within a circular economy perspective. This study aims at investigating a potential reuse of spent coffee grounds to produce novel construction materials to be used for sustainable buildings.MethodsAfter having illustrated the forward flows within the coffee life cycle and the potential reverse flow options, an evaluation method based on multi-criteria analyses was elaborated to test not only the technical but also the environmental and economic performances of novel materials originating from the incorporation of SCG as an aggregate in natural hydraulic lime and geopolymer-based mortars. Moreover, we focus on the reuse of another waste streams— biomass fly ash—deriving from the paper-pulp industry, rarely investigated in both traditional construction applications and in geopolymer manufacture. The two (geopolymer- and lime-based) mortar typologies are here studied and compared as potential green material for applications in construction, with satisfying engineering performance and high insulation attitude, giving a new life to a common organic waste. Consequently, we compare eight formulations by means of multi-criteria approaches that are nowadays claimed as a useful and effective decision aiding support instrument to assess the development of new sustainable construction materials. They permit to consider simultaneously some controversial and often uncertain aspects like technological (as the usual scientific studies do), environmental, and economic (more difficult to easily approach and evaluate). For this purpose, in this paper, we have analyzed the performance of the novel bio-composite mortars using VIKOR and TOPSIS methods to rank a set of alternatives according to various evaluation criteria that often conflict one with each other.ResultsResults show that adding spent coffee grounds can efficiently improve the technical and sustainable performances of the novel mortars for different applications in the building sector. The presence of SCG increases water absorption and improves the insulation performance along with an environmental impact reduction. The considered technological properties are highly promising—such as the improvement in thermal insulation. In particular, even the addition of only 5% SCG leads to a significant reduction of the thermal conductivity and consequently to a greater insulating performance.ConclusionsTo date, most of the available literature on recycling SCG in construction materials do not consider mortar-based applications and, moreover, nor multi-criteria approaches. Therefore, our study proposes itself as an innovative track solution to food waste management lowering the employment of non-renewable natural resources and the costs associated to construction material production. At the same time, a novel and innovative way of such waste disposal is suggested, pursuing the sustainability and substantially reducing the environmental impact of construction and building materials. This study is a fundamental step in assessing the applicability of our designed and produced materials and its potentials to be produced at an industrial scale.

Lightweight Concrete Precast Panels for the Improvement of Thermal Insulation of Housing with Expanded Polystyrene Beads

The precast concrete elements in the construction of buildings are increasingly used due to their better quality control, constructive speed, reduction of the number of workers and less waste of resources compared to conventional construction; for wall applications, to these advantages, the design to ensure thermal comfort requires the improvement of the low thermal insulation of conventional concrete panels. The use of materials with lower thermal conductivity such as Expanded PolyStyrene Beads (EPSB) in lightweight concrete for the construction of precast panels in housing, contributes to improve thermal insulation and the saving operational energy during its operation phase, because the aggregate has a small size, low density and thermal conductivity; applied in higher volumes in concrete, reduces indoor heat loss in cold climates and indoor heat gain in warm climates in housing. The purpose of this research is to study the behavior of lightweight concrete with EPSB for 16%, 26% and 36% addition and evaluate the air-dry density, compressive strength, thermal conductivity, relationship between air-dry density with compressive strength and thermal conductivity. The results indicate that the higher the percentage of EPSB the air-dry density, compressive strength and thermal conductivity decrease; the relationships between air-dry density with compressive strength and thermal conductivity follow a linear trend and are similar.