Low Carbon Materials Research Articles

Closing the gap to sufficiency-based absolute climate targets for wood buildings

This research investigated the distribution of the global climate planetary boundary (PB) on a national scale. Then it was distributed to a sector-specific carrying capacity by the principles of acquired rights (grandfathering) and sufficientarianism. Then, four wood dwellings were compared against these carrying capacities using the life cycle assessment methodology. The climate safe operating space for new dwellings is about three times larger when using the principle of sufficiency compared to acquired rights. The rationale for the sufficiency perspective is that it considers the fundamentals of a society leading to a fulfilling life. The concept disregards the current surplus elements in society, which gives more space for emissions for the remaining elements in a fulfilling society. The acquired rights reflect the current society as optimal but require systemic changes in the different sectors to reduce their total impacts to remain within climate PB while keeping the sector’s current share of impacts. However, building with wood cannot alone contribute to society staying within the climate target. The end of life contributes most to the impact due to biogenic carbon release, and energy consumption follows next. Reduction of the average yearly built area shows considerable potential to close the target gap. In addition, improving and implementing circularity, carbon capture, and material efficiency would reduce biogenic carbon’s end of life impacts. Combined with energy-positive buildings and low-carbon materials, this could be a viable mitigation pathway to explore further.

Expansion properties of concrete containing circulating fluidised bed fly ash for use in concrete-filled steel tubes

In the context of green and low-carbon materials development, the influence of replacing cement with circulating fluidised bed fly ash (CFBFA) on the expansion properties of paste under different curing conditions was first systematically investigated. Then, self-compacting concretes (SCCs) with recycled aggregate (RA) and CFBFA were prepared for filling steel tubes. The experimental results showed that, because of its unique physicochemical properties, the incorporation of CFBFA significantly increased the water requirement needed to achieve standard consistency of the paste and the pore structure was optimised by a reduction in the number of large pores due to the formation of more expansion components (ettringite, gypsum and portlandite are the main expansive products of CFBFA–cement paste). The influence of factors such as curing condition, age and CFBFA on the expansion effect was notable. With a 40% CFBFA content, the RA SCC in the steel tube showed an expansion of 41 μm/m, while the 28-day compressive strength reached 48.9 MPa.

Crab-claw inspired high performance and flame-retardant magnesium oxychloride cement based adhesive reinforced by 4-arms EDTA and tartaric acid for wood industry

The high CO2 emissions and instability of silicate cement binders during production and use have encouraged the development of low-carbon materials. In this study, an environmentally friendly and flame-retardant building material was produced from magnesium oxychloride cement (MOC) and wood. In practice, the considerable microcracking that forms during the hardening process makes MOC materials very sensitive to water, which limits their further use. Inspired by the predation of crabs, a simple and effective method was proposed to obtain better water resistance and mechanical strength of MOC composite by co-modifying with ethylenediaminetetraacetic acid (EDTA) or disodium ethylenediaminetetraacetic acid (EDTA-Na) in conjunction with tartaric acid. The four –COOH of EDTA and EDTA-Na coordinated well with the 5-phase structure and tightly aggregated the 5-phase crystals, effectively reducing the formation of microcracks. The synergistic effect between EDTA/EDTA-Na and tartaric acid prevented the disruption of 5-phase crystal structures by water molecules, thus improving the water resistance of the MOC composite. The softening coefficients of the MOC composite modified by EDTA and EDTA-Na in cooperation with tartaric acid after soaking for seven days were 0.97 and 0.98, respectively, which is significantly higher than that of the MOC composite modified by tartaric acid alone (0.54). At the same time, the co-modified MOC composite can be utilised as an inorganic adhesive for plywood, and the wet strength of plywood modified with EDTA in cooperation with tartaric acid being 25% higher than that of the unmodified MOC composite. In addition, the resulting composites showed great potential for application in low-carbon building materials, which can help alleviate the environmental impact of construction industries.

Experimental assessment of self-tapping screws for the reinforcement of multiple holes in laminated veneer lumber beams

In recent times, there is increased focus in the built environment on the use of low carbon materials. In tall timber buildings, service ducting needs to be facilitated. Multiple holes in elements may be required in buildings where a high demand of services exist. Limited investigations have been conducted on laminated veneer lumber (LVL) beams in comparison to the literature on timber and glued laminated timber beams and no experimental testing has been conducted where multiple holes in LVL have been reinforced. Such openings are of particular concern when positioned in high shear zones. Therefore, an experimental programme in which seventy-five LVL beams were monotonically tested in three-point bending was conducted. The programme included standard beams, beams with a single round hole, and beams with double round holes for three different hole diameters and two holes spacings. The openings were concentrically positioned and were reinforced using internal screw reinforcement in which three configurations were examined. The programme was designed to evaluate the guidance that is currently available which has been developed based on testing with glued laminated timber. Throughout, it was seen that the self-tapping screws orientated at 60° were the most effective in comparison to when the reinforcement was orientated at 45° or positioned vertically. For LVL beams with single holes and up to hole diameters of 0.45 diameter (d) which far exceeded the current guidance of 0.3d maximum hole size, the reinforcement when positioned at 60°, achieved midspan failures like standard beams. The failure loads of such reinforced beams were in the same range as the standard beams. The screw reinforcement when orientated at 60o, was most effective for the double holed beams when a hole size of 0.35 d for both spacings (0.5 d and 0.75 d) was studied. The load carrying capacity was also in the same range as the standard beams but the failure mode was hole edge failure. Strain profile readings indicated the effectiveness of the reinforcement such that strains at the soffit of the beam where two holes were reinforced with screws exceeded the strains at the soffit of the standard beams.

Ultra-lightweight low-carbon LC3 cement composites: Uniaxial mechanical behaviour and constitutive models

The present study aims to characterize the constitutive models of a novel ultra-lightweight low-carbon LC3 cement composite (ULCC-LC3) under monotonic uniaxial compression and tension tests. The compressive stress–strain curves of ULCC-LC3 were obtained based on axial compressive tests. The curve characteristics were analyzed and the data was fitted with the existing concrete compression constitutive model. Modified axial compression constitutive model for ULCC-LC3 was proposed and verified using the independent test data and related data of ULCC in other literatures. The characteristics of tensile stress–strain curves of ULCC-LC3 were also analyzed and studied. Based on existing experimental data, the applicability of the Tetsushi et. al.’s model to this composite was verified. The experimental results show that use of PE fibers can improve the ductility of ULCC-LC3. As compared with normal concrete, ULCC-LC3 exhibits a higher compressive peak strain (over 0.3% for fiber reinforced specimens and over 0.5% for non-fiber reinforced specimens). These findings contribute to the understanding of the mechanical behavior of ULCC-LC3 and provide constitutive models that can be used in numerical simulations and engineering applications to promote the use of this novel ultra-lightweight low-carbon material.

Characteristics of embodied carbon emissions for high-rise building construction: A statistical study on 403 residential buildings in China

High-rise residential buildings are prevalent in Chinese cities and have considerable impacts on the sustainable construction industry. Although individual case studies have assessed the embodied carbon emissions, there is still a need to explore the general characteristics and driving factors. This study established a dataset containing 403 buildings and assessed the statistics and distribution of relevant embodied carbon intensities using a cradle-to-site system boundary. An average embodied carbon intensity of 424.1 kgCO2e/m2 was obtained, with 2/3 of the carbon emissions attributed to structural materials including steel, concrete, and prefabricated members. Based on contribution analyses and significance tests, the influences of driving factors encompassing building height, structural form, seismic design grade, delivery type, and building investment were examined, and carbon reduction strategies were discussed. The results indicated a potential 28.8% reduction in the embodied carbon intensity considering a cascaded strategy of substituting low-carbon materials, optimizing material use, and using local materials.

Geometric design and performance of single and dual-printed lattice-reinforced cementitious composite

Recent advances in additive manufacturing have enabled the design and fabrication of auxetic materials with programmable geometries and tailorable properties, but ongoing challenges remain in integrating them for composite design. In this work, we exploit a composite design strategy on cementitious material units embedded with three-dimensional re-entrant (3DR) lattices fabricated by single and dual material printing. Guided by experimental tests, the effect of additive manufacturing parameters on the mechanical properties of rigid and flexible 3DR lattices is confirmed. Then, we characterize the compressive behavior of lattice-reinforced cementitious composite (LRCC) units embedded with 3DR lattices printed using rigid, flexible, and dual materials with various spatial distributions. We found comparable ultimate strengths and higher energy-absorbing capabilities despite weaker 3D-printed materials embedded in LRCC units. A similar observation was found on LRCC columns with various geometric patterns. We envision that our proposed composite design strategy can produce next-generation low-carbon material systems with high performance and production efficiency toward a sustainable built environment.

Exploring Low-Carbon Design and Construction Techniques: Lessons from Vernacular Architecture

This paper presents a comprehensive review of low-carbon materials and construction techniques commonly used in vernacular buildings. The study highlights the relevance of vernacular architecture in the context of the shift towards sustainable construction practices. A combination of a climatic zone map, vernacular language type map, and continent map is used to identify the vernacular regions. Eight bio-based low-carbon materials, including wood, adobe, rammed earth, cob, sod, thatch, bamboo, and straw bales, are discussed, along with their characteristics, availability, and environmental impacts. The construction techniques associated with these materials are explained, emphasizing their simplicity, cost-effectiveness, and adaptability. The paper also explores two important design approaches: design for disassembly and design for modularity that were used in vernacular building. The review found the use of low-carbon materials and construction techniques derived from vernacular architecture can contribute to minimizing waste, reducing environmental impacts, and promoting a circular economy in the building industry. This research provides valuable insights for architects, engineers, and policymakers seeking sustainable alternatives in the construction sector.

A Comprehensive Overview of the Utilization of Recycled Waste Materials and Technologies in Asphalt Pavements: Towards Environmental and Sustainable Low-Carbon Roads

Given the prevailing concerns about greenhouse gas emissions, global warming, and the growing demand for renewable resources, the pavement industry, among others, is actively engaged in researching and exploring low-carbon materials and technologies. Despite the growing interest in low-carbon asphalt pavement, there is still a significant knowledge gap regarding the use of various waste materials and technologies to achieve this goal. This study aims to close this gap by conducting a systematic review and scientometric assessment of the existing studies on the use of waste materials and technologies for low-carbon asphalt pavement. The study spans the years 2008 to 2023, and the scientometric analysis was conducted using the VOS viewer application. The study identifies materials and technologies in this area by examining co-authored country studies, publication sources, and keyword co-occurrence. It should be noted that a limited number of waste materials that allow CO2 emissions reduction was analyzed in this study. However, other waste categories, such as bio-oils and polymers, which can provide positive either environmental or economic impacts on the production of paving materials, were not considered in the scope of the study. Based on the current review, it was found that integrating recycled waste materials like recycled asphalt pavement, biochar, or crumb rubber with alternative mixing technologies such as warm mix asphalt and cleaner energy can significantly reduce CO2 emissions. China and the United States were identified as key research contributors to the low-carbon pavement. Furthermore, biomass-based fuel and electric construction equipment lower carbon and greenhouse gas emissions by 36–90% and 67–95%, respectively. However, before various recycled waste materials and technologies can be widely used in the asphalt industry, various challenges need to be addressed, including cost concerns, performance and durability concerns, standardization and regulations, availability, integration with existing facilities, and insufficient field and long-term data. The review identified critical research gaps, such as the absence of a homogeneous and reliable standard method for low-carbon asphalt pavement, limited field performance data, and a life cycle assessment approach in analyzing the emission reduction effects. The reviews will aid in the paradigm shift to a more carbon-friendly pavement industry that uses recycled waste materials and technologies.

Mechanical properties and microstructure of glass fiber reinforced polymer (GFRP) rebars embedded in carbonated reactive MgO-based concrete (RMC)

Reactive MgO cement (RMC) is an emerging low-carbon material which can be a sustainable alternative to ordinary Portland cement (OPC) due to its capability to sequester CO2. However, the application of carbonated RMC concrete in conventional steel reinforced concrete infrastructure is restricted by its inherent low alkalinity (∼10.4), which cannot protect steel from rusting. To address this issue, glass fiber reinforced polymer (GFRP) rebars can be employed. In this study, the mechanical properties and microstructures of RMC-GFRP exposed to various temperatures (23, 40 or 60 °C) for 21, 45 and 90 days were investigated. Experimental results showed that the low-alkalinity carbonated RMC concrete was less aggressive than the normal concrete (NC) to GFRP rebars, remarkably enhancing the tensile strength retention of GFRP rebars from 73.6% to 90.4% after 90 days of exposure at 40 °C. Micromorphology observation indicated that the higher tensile strength retention was ascribed to the reduced GFRP degradation (i.e., matrix cracking, fiber erosion and fiber/matrix interfacial debonding) under the low-alkalinity condition. Additionally, the flexural strength of 90-day aged RMC- and NC-GFRP samples at 60 °C were close to that of unconditioned GFRP samples (791 MPa and 788 MPa vs. 791 MPa), which was attributed to the unchanged glass transition temperature and stable elastic modulus of GFRP. The RMC- and NC-GFRP samples also showed very little change in inter-laminar shear strength as compared to the unconditioned GFRP samples, as the middle layer of GFRP rebars was well-protected from external water and chemicals. Based on the empirical degradation model and activation energy derived from test results at different temperatures, the predicted tensile strength retention of RMC-GFRP after an extended period (∼100 years) under Canadian climate is still sufficient. This study will shed light on the understanding of degradation mechanism and practical application of GFRP reinforced RMC in infrastructure construction.

Assessment of Carbon Reduction Benefits of A/O-Gradient Constructed Wetland Renovation for Rural Wastewater Treatment in the Southeast Coastal Areas of China Based on Life Cycle Assessment: The Example of Xiamen Sanxiushan Village

The enhancement of carbon sequestration and emissions reduction has emerged as a primary concern in China’s rural regions. Nevertheless, numerous completed rural wastewater treatment facilities necessitate retrofitting due to suboptimal operational conditions. Consequently, evaluating the greenhouse gas (GHG) emissions impact and carbon reduction advantages of rural wastewater treatment facility retrofitting is essential. Existing research predominantly focuses on urban wastewater treatment plants, with minimal attention given to GHG emissions impact during the construction and demolition stages of wastewater treatment facilities. In this investigation, we developed a life cycle assessment (LCA)-based evaluation model to appraise the GHG emissions impact and carbon reduction benefits of retrofitting rural wastewater treatment facilities. We examined a renovation project in Sanxiushan Village, Xiamen City, Fujian Province, incorporating the integrated plant treatment technology of constructed wetlands. Our findings indicate that retrofitting offers significant advantages in terms of GHG emissions reduction, even when accounting for implicit GHG emissions. The establishment of supplementary terraced constructed wetlands and landscape greening can yield more substantial carbon reduction benefits. Moreover, we discovered that implicit GHG emissions during the construction stage can be mitigated by employing local, recycled, and low-carbon materials. Modifying vegetation community structure and prioritizing vegetation species selection can enhance the carbon storage capacity of plants, reducing overall life cycle GHG emissions and augmenting emissions reduction benefits. The evaluation model developed in this study can facilitate the promotion of low-carbon construction and operation of rural wastewater treatment facilities.

Effect of hooked end steel fibers on strength and durability properties of ambient cured geopolymer concrete

Growing carbon emissions in the construction industry have warranted the use of alternative materials such as geopolymer concrete. At the same time exposure of concrete material to harsh environmental conditions has compelled to design of durable geopolymer concrete. The use of hooked-end steel fibers in conventional fiber-reinforced concrete has proven to improve its crack resistance, and thus, positively influence the durability properties of concrete structures. Nevertheless, limited studies explore the effect of hooked-end steel fibers on the strength and durability properties of ambient cured geopolymer concrete with a low NaOH content (i.e., 8 M concentration). In this study, ambient cured geopolymer concrete was prepared by fly ash, ground granulated blast furnace slag (GGBS), NaOH, Na2SiO3, manufactured sand, and natural coarse aggregates. Additionally, hooked-end steel fibers with an aspect ratio of 67 were added to the mix by volume fraction in dosages of 0 %, 0.5 %, 1 %, 1.5 %, and 2 %. The experimental results showed that the addition of fibers reduced the workability with a minimum slump of 70 mm and a maximum Vee Bee time of 8 s for mixes with 2 % steel fibers. The addition of fibers improved the compressive strength, split tensile strength, and flexural strength of geopolymer concrete, with a maximum strength of 41.44 MPa, 4.28 MPa, and 5.23 MPa at an optimum fiber dose of 1 %, respectively. Above the optimum dose, the strength of the steel fiber-reinforced geopolymer concrete (SFRGPC) was reduced. The depth of water penetration reduced in SFRGPC when compared to GPC. Moreover, the resistance to chloride ion penetration was not significantly affected by addition of steel fibers till optimum dose of 1 %. The scanning electron microscopic results revealed the positive effect of steel fibers in restricting the progression of cracks. This has resulted in smaller crack width in the SFRGPC when compared to GPC. Overall, steel fibers in optimum dose have improved the performance of geopolymer concrete and this will contribute towards low carbon material.

Making embodied carbon mainstream: a framework for cities to leverage waste, equity, and preservation policy to reduce embodied emissions in buildings

With anticipation building around embodied carbon as a “new frontier” of climate policy, it may appear that cities need to develop a whole suite of dedicated institutions and mechanisms to support its implementation. However, to do so risks placing an undue burden on already overstretched local and regional governments. Instead, embodied carbon policy can build on existing priorities that already galvanize resources and attention and have benefited from decades of policy development. Making strong links to a larger urban agenda offers a way to forge buy-in from a wide range of stakeholders. Current visions for embodied carbon policy broadly fall into two categories: (1) material substitution strategies, or technical solutions that incrementally reduce emissions, and (2) demand reduction strategies, more transformative solutions that avoid emissions. Both of these areas have strong ties to existing urban strategies for waste, equity, and preservation. Foundations in waste policy include increasing waste diversion, expanding green demolition, and increasing material efficiencies. Foundations in equity-oriented policy include retrofitting affordable housing, workforce development for deconstruction, and building lower carbon, lower cost housing. Foundations in preservation policy include incentivizing building reuse, supporting the use of low carbon materials for retrofits, and encouraging vertical infill. Amplifying existing policy efforts can bring substantive embodied carbon reductions to the forefront, leapfrogging a long technical start-up phase for implementing stand-alone embodied carbon policy.

Potential of low carbon materials facing biodeterioration in concrete biogas structures

Potential of low carbon materials facing biodeterioration in concrete biogas structures

Development of low-carbon materials from GGBS and clay brick powder for 3D concrete printing

A new low-carbon material for 3D concrete printing by utilizing recycled ground granulated blast-furnace slag (GGBS) and clay brick powder (CBP) was developed to reduce the carbon footprint. The printability and hardened properties of 3D printed mortar were systematically investigated to reveal the coupling effect of GGBS and CBP. The results indicate that the printability of mortar is significantly influenced by the morphology and particle size distribution of admixtures. The vitreous surface of GGBS reduces the yield stress of the paste, while the porous surface of CBP has the opposite effect. Furthermore, increasing CBP replacement leads to a denser packing of binders, which releases more free water to increase the fluidity of mortar. The printing process not only increases the proportion of capillary and macro pores, but also reduces the sphericity of macro pores. As a result, 3D printed mortar experiences a 10 ∼ 50 % loss in compressive strength and mechanical anisotropy of 3D printed mortar. The secondary hydration reaction of GGBS and CBP reduces the average pore diameter from 41.7 nm to 15.3∼19.3 nm and increases the complexity of micro pores, resulting in a significant decrease in chloride ions migration in the mortar. These results demonstrate the feasibility of using low-carbon materials containing GGBS and CBP for 3D concrete printing.

Development of low-carbon cement: Carbonation of compounded C2S by β-C2S and γ-C2S

Widespread utilization of Portland cement (PC) with a large-scale carbon footprint has caused a vital climate crisis. The application of low-carbon materials rich in belite is hindered by the low hydraulic activity of C2S. Both β-C2S and γ-C2S can rapidly develop compressive strength and sequestrate CO2 after carbonation. To explore the role of β-C2S and γ-C2S played on compressive strength and carbonation degree in C2S paste, several groups of C2S samples composed of pure β-C2S and pure γ-C2S in different weight contents (wt.%) were homogenized and carbonated. Compressive strength was tested, and XRD, TGA, FT-IR, and SEM analysis methods were applied to observe the carbonation properties. Experimental results showed that compressive strength positively correlated with the proportion of β-C2S content, and the carbonation degree positively correlated with the proportion of γ-C2S content. Different ratios of β-C2S and γ-C2S mainly affected the growth rates of compressive strength and carbonation degree. When β-C2S was 60 wt% and γ-C2S was 40 wt%, both compressive strength (54.4 MPa) and carbonation degree (36.7%) of carbonated samples can reach an optimum value. The calcite content increased with γ-C2S content, while the crystallite size of calcite decreased with the γ-C2S content. Through the established carbonation kinetics equation and the measured carbonation heat curves of compounded C2S, the possible synery effect of β-C2S and γ-C2S was proposed. Combined β-C2S and γ-C2S in cement clinker can reduce CO2 emissions. Carbonating high-belite cement composed of a certain proportion of β-C2S and γ-C2S will contribute to developing early compressive strength and improving CO2 sequestration of this low-carbon cementitious material.

Composite alkali-activated materials with waste tire rubber designed for additive manufacturing: an eco-sustainable and energy saving approach

There is an increasing trend in research projects and case studies to demonstrate the potential of Additive Manufacturing (AM) with concrete, better known as 3D concrete printing. Like ordinary construction, the latest upgrades on this topic are strongly focused towards improving eco-sustainability in terms of low-carbon materials. Low-carbon binders’ alternative to Portland cement and the utilisation of selected waste materials in place to virgin aggregates has high potential in fulfilling the sustainable development goals. In this paper, an experimental study was performed by incorporating ground waste tire rubber aggregates of different size gradation (0–1 mm and 1–3 mm) and replacement levels (50 v/v% and 100 v/v%) in a “greener” alkali-activated mix designed for 3D printing applications. First, the experimental program involved the optimization of mix design rheology and printing parameters to successfully integrate rubber aggregates into the printable alkali-activated mixtures. Then, a comprehensive characterization, including static mechanical testing, dynamic thermo-mechanical analysis, thermal conductivity testing, and acoustic insulation measurements was conducted. Comparison with identical Portland-based rubberized formulations designed for AM revealed better mechanical isotropy, flexural strength, thermo-mechanical behaviour, heat insulation, and high-frequency acoustic insulation for alkali-activated composites. The influence of rubber aggregate size on the fresh and hardened state behaviour of the mixes was also studied and discussed. Keeping the losses in mechanical strength restrained, the rubberized composites designed in this study have demonstrated significant thermal and acoustic insulation properties that are desired for energy-saving applications in buildings. The research verified the practicability of using waste aggregates in low-carbon binders for sustainable lightweight and thermo-acoustically effective applications, establishing an attractive starting point to address future research on material optimization for practical purposes.

Carbonaceous Catalyst Activated Persulfate for Degradation of Antibiotic Pollutants in Water

In recent years, the frequent use of antibiotics has led to the continuous release of antibiotics into the water environment, which not only poses a potential threat to public health, but also contributes to the generation and spread of antibiotic resistance. In addition, due to the high environmental persistence and low biodegradability of antibiotics, it is difficult to be effectively degraded by traditional water treatment processes. Therefore, it is urgent to develop clean and efficient treatment technologies. Advanced oxidation processes (AOPs), which can effectively remove refractory organic pollutants from water, has become a promising water treatment technology. In this regard, persulfate (PS)-based AOPs (PS-AOPs) has attracted extensive attention of researchers. In this system, PS can be activated by energy and catalysts to produce highly oxidizing active species, and achieve efficient degradation of antibiotics. Due to its rich surface functional groups, high specific surface area and high adsorption properties, researches on the activation of PS by carbonaceous materials have been reported continuously. In this paper, the research progress of carbon nanotubes, graphene, biological carbon, active carbon and hetero-atom doped carbon materials as catalysts to activate PS and degrade antibiotics is reviewed. In addition, the structure and properties of different carbon materials and the activation mechanism of free radical and non-free radical mediated by carbon materials were introduced, and the effects of PS dosage, catalyst dosage, temperature and pH on the degradation of antibiotics were discussed. Finally, this paper points out the important development direction in the future, that is, the development of environmental protection, high efficiency, low cost carbon materials and further research on the actual wastewater treatment performance.

Microscopic Mechanism of Tunable Thermal Conductivity in Carbon Nanotube-Geopolymer Nanocomposites.

Geopolymer has been considered as a green and low-carbon material with great potential application due to its simple synthesis process, environmental protection, excellent mechanical properties, good chemical resistance, and durability. In this work, the molecular dynamics simulation is employed to investigate the effect of the size, content, and distribution of carbon nanotubes on the thermal conductivity of geopolymer nanocomposites, and the microscopic mechanism is analyzed by the phonon density of states, phonon participation ratio, spectral thermal conductivity, etc. The results show that there is a significant size effect in the geopolymer nanocomposites system due to the carbon nanotubes. In addition, when the content of carbon nanotubes is 16.5%, the thermal conductivity in carbon nanotubes vertical axial direction (4.85 W/(m k)) increases by 125.6% compared with the system without carbon nanotubes (2.15 W/(m k)). However, the thermal conductivity in carbon nanotubes vertical axial direction (1.25 W/(m k)) decreases by 41.9%, which is mainly due to the interfacial thermal resistance and phonon scattering at the interfaces. The above results provide theoretical guidance for the tunable thermal conductivity in carbon nanotube-geopolymer nanocomposites.

Research on Green and Low-Carbon Development Path of China’s Automotive Industry

China’s automotive industry has been dedicated to a series of carbon-reduction efforts and has strived for comprehensive green and low-carbon transformation in order to achieve carbon peaking and carbon neutrality goals. On the basis of automobiles’ whole life-cycle (WLC) carbon emission accounting, this paper calculates life-cycle carbon emissions per vehicle, proposes green and low-carbon development path for China’s automotive industry, quantifies and analyzes implicated carbon-reduction potential, and puts forth suggestions for high-quality green and low-carbon development of China’s automotive industry. The first is to establish a sound standard and data management system; the second is to promote research, development and application of low-carbon materials and low-carbon technologies; the third is to accelerate the pace of fostering a new consumption model in the automotive industry. The research results can further support national policy-making regarding carbon emissions, promote corporations’ research, development and application of low-carbon technologies, encourage green and low-carbon consumption, and lead the automotive industry to achieve WLC neutrality.