Low-carbon Construction Materials Research Articles

Full-scale shaking table tests of cross-laminated timber structures adopting dissipative angle brackets and hold-downs with soft-steel and rubber

Cross-laminated timber (CLT) has recently attracted significant interest in building timber or hybrid structures owing to the rapidly growing demand for low-carbon construction materials with excellent mechanical properties. To investigate the seismic performance of CLT structures adopting novel dissipative angle brackets and hold-downs with soft-steel and rubber (i.e., SRD-ABs and SRD-HDs), a series of shaking table tests were performed on two full-scale specimens, i.e., a benchmark specimen (Specimen Ⅰ) and a specimen with a multi-doorway at the ground (Specimen Ⅱ). Several representative ground motions, including the Turkey wave, El Centro wave, Wenchuan wave, and Shanghai artificial wave, were selected as excitations, whose peak acceleration increased gradually from 0.035 g to 0.80 g. The damage patterns of the structures were revealed, and the dynamic characteristics and responses were obtained and analyzed. The results show that the fundamental frequencies of Specimen Ⅰ and Specimen Ⅱ were 4.125 Hz and 3.625 Hz, respectively. The mode shapes of each specimen remained similar before tests with peak ground acceleration (PGA) of 0.51 g, with only a slight decrease of approximately 5 % in the fundamental frequency, indicating that the specimens only suffered minor damage because of the great energy-dissipating capacity of the SRD-ABs and SRD-HDs. After experiencing tests with PGA of 0.80 g, the specimen exhibited a maximum inter-story drift of 1/60 with a structural damping ratio of 13 %, and the damage was mainly exhibited at the SRD-ABs and SRD-HDs, which realized the performance objective of replaceability of dissipative connections and repairability of structures under the 9-degree rare earthquakes. Furthermore, non-linear numerical models were developed to duplicate the dynamic characteristics and responses of the test specimen, and the analytical results from the models show satisfactory agreement with the test results. Overall, the outcomes of this paper can provide valuable references for future research and applications of CLT structures with the SRD-ABs and SRD-HDs.

Environmental Life Cycle Assessment of a Novel Hemp-Based Building Material.

The global construction sector contributes a significant share of total greenhouse gas (GHG) emissions. In Australia, infrastructure activity alone generates 18% of the GHG emissions. The use of low-embodied carbon building materials is crucial to decarbonise the construction sector and fulfil national and international climate goals. Industrial hemp (Cannabis sativa L.) is a promising feedstock for low-carbon construction materials because of its carbon sequestration capacity, fast-growing cycles, and technical functionality comparable to traditional materials. This study utilised the life cycle assessment (LCA) guideline ISO 14040:2006 to estimate the carbon footprint (CF) of hemp-based building materials in Western Australia capturing region-specific variations in terms of inputs, soil, productivity, and energy mix. The functional unit was 1 m2 of a hemp-based board, and the system boundary was cradle-to-gate, i.e., pre-farm, on-farm, and post-farm activities. The CF of 1 m2 of hemp-based board was estimated to be -2.302 kg CO2 eq. Electricity from the public grid for bio-based binder production during the post-farm stage was the main contributor to total CO2 eq emissions (26%), followed by urea production (14%) during the pre-farm stage. Overall, the use of electricity from the public grid during the post-farm stage accounted for 45% of total emissions. Sensitivity analysis showed that the CF of hemp-based boards was highly sensitive to the source of energy; i.e., total replacement of the public grid by solar power decreased the CF by 164% (-2.30 to -6.07 kg CO2 eq). The results suggested that hemp-based boards exhibit lower embodied GHG emissions compared to traditional materials, such as gypsum plasterboards.

Research on crystalline admixtures for low carbon buildings based on the self-healing properties of concrete

The increasing fascination surrounding low carbon construction materials has propelled self-healing concrete into the realm of vital technologies for attaining low carbon objectives. This investigation through artificial cracking and precompression experiments demonstrates the efficacy of two specific crystalline admixtures (CAs), namely L-aspartic acid (LAA) and Ethylenediaminetetraacetic acid (EDTA), in augmenting the self-healing characteristics of concrete. The flexural and compressive strength as well as chloride ion diffusion coefficient tests, were used to evaluate the mechanical properties and durability, and the microstructures was analyzed by X-ray diffraction (XRD), differential thermogravimetric analysis (TG-DTG), scanning electron microscopy (SEM), Bruno-Emmett-Teller (BET) and mercury intrusion pore size measurement (MIP). The findings indicate that the optimum dosage for both LAA and EDTA is determined to be 0.5%. At this dosage level, these admixtures effectively fill the pores by stimulating the production of hydrated calcium silicate gel (CSH) and calcium carbonate, leading to a reduction in porosity, enhanced concrete compactness, and successful activation of the self-healing mechanism. Moreover, the incorporation of these admixtures results in improved strength grade and enhanced resistance against chloride ion penetration.

Carbon reduction performance and economic analysis in building construction - a pilot trial of low-carbon construction in the O•PARK2 construction phase

With the wide application of green building standards to reduce the carbon emissions from the operation phase, the carbon emissions during the construction phase are becoming more and more significant. Carbon footprint management is necessary and low-carbon measures, including low-carbon construction materials, construction site electrification, on-site renewable energy systems, and low-carbon alternative fuels should be considered. Taking a real case of a Design-Build-Operate project, O•PARK2, as a pilot trial, this study investigates the carbon reduction efficiency and cost increment of various low-carbon measures, and introduces the Green Premium Index to explore the tradeoff between carbon reduction and carbon offsetting by credit purchasing. Low-carbon measures adopted in O•PARK2 were proved to be carbon reduction efficient, achieving 4,612 tonnes of CO2e emission reduction. Early development of decarbonisation strategy enables further emission reduction and lower cost increments during the construction phase, in which low-carbon construction material should be prioritised, followed by construction site electrification, and the use of solar panels and B5 biodiesel. With low-carbon construction materials locally manufactured, construction decarbonisation progress in Hong Kong will be significantly enhanced. Lowcarbon construction should see carbon reduction as the main direction, and carbon offsetting as supplemental.

The Industrialisation of Sustainable Construction: A Transdisciplinary Approach to the Large-Scale Introduction of Compacted Mineral Mixtures (CMMs) into Building Construction

Increasing demand for sustainable, resilient, and low-carbon construction materials has highlighted the potential of Compacted Mineral Mixtures (CMMs), which are formulated from various soil types (sand, silt, clay) and recycled mineral waste. This paper presents a comprehensive inter- and transdisciplinary research concept that aims to industrialise and scale up the adoption of CMM-based construction materials and methods, thereby accelerating the construction industry’s systemic transition towards carbon neutrality. By drawing upon the latest advances in soil mechanics, rheology, and automation, we propose the development of a robust material properties database to inform the design and application of CMM-based materials, taking into account their complex, time-dependent behaviour. Advanced soil mechanical tests would be utilised to ensure optimal performance under various loading and ageing conditions. This research has also recognised the importance of context-specific strategies for CMM adoption. We have explored the implications and limitations of implementing the proposed framework in developing countries, particularly where resources may be constrained. We aim to shed light on socio-economic and regulatory aspects that could influence the adoption of these sustainable construction methods. The proposed concept explores how the automated production of CMM-based wall elements can become a fast, competitive, emission-free, and recyclable alternative to traditional masonry and concrete construction techniques. We advocate for the integration of open-source digital platform technologies to enhance data accessibility, processing, and knowledge acquisition; to boost confidence in CMM-based technologies; and to catalyse their widespread adoption. We believe that the transformative potential of this research necessitates a blend of basic and applied investigation using a comprehensive, holistic, and transfer-oriented methodology. Thus, this paper serves to highlight the viability and multiple benefits of CMMs in construction, emphasising their pivotal role in advancing sustainable development and resilience in the built environment.

Thermal transformation of bamboo sawdust for its advanced cementitious composites

This paper investigates a vacuum heat treatment (VHT) technology at 160℃, 200℃ and 240℃ for 6–14 h to modify bamboo sawdust (BS) and then BS/cement composites for the development of low carbon construction materials. The hydration process, thermal stability, micro-morphology and crystallinity, and chemical and mechanical changes for both VHT BS and composites are examined by FTIR, TG-DTG, XRD and SEM analyses. The mechanism of improving the mechanical properties of modified BS on composite materials is further elaborated together with the physical and mechanical properties and durability. The results show that the flexural strength and compressive strength of the modified BS/cement composites after VHT at 200℃ for 10 h are increased by 61.2% and 13.8%, respectively, compared with those in the untreated group, and the composites have better durability in the modified group. VHT resulted in cellulose and hemicellulose degradation to certain degrees, lignin undergoes cross-linked condensation reaction and cellulose crystallinity increases. These changes reduce the number of BS hydrophilic groups and result in changes in BS microstructure and surface topography, providing favorable conditions for the bonding and interface development of BS/cement composites. The impact of BS/cement composites on the carbon footprint in the production stage was analyzed, showing that the carbon emissions of BS/cement composites after VHT were reduced by 5.7% compared with that of the corresponding OPC composites.

Parametric BIM-Based Lifecycle Performance Prediction and Optimisation for Residential Buildings Using Alternative Materials and Designs

Residential building construction is resource-intensive and significantly impacts the environment by embodied and operational carbon emissions. This study has adopted a parametric building information modelling (BIM)-based approach for a residential building to analyse its lifecycle carbon performance and to evaluate the optimisation potential through alternative material use and design. The study looks at a residential development project, applying an automatic calculation and analysis tool of upfront embodied carbon and BIM-based lifecycle energy simulation to predict carbon emissions from operating the built spaces. A parametric BIM model has been established to aid energy simulation and operational carbon assessment across a 50-year building lifetime, considering 1.5 °C Net-Zero World and 3 °C Hot House World climate scenarios. Various improvement opportunities for future residential development projects, from material selection to operational efficiencies, are explored. This includes quantitative analysis on architectural-structure design, low-carbon construction materials (e.g., cement substitutes, steel scraps, and green hydrogen steel), and novel design for construction approaches (such as modular integrated construction), with discussion around their impacts on optimising the building lifecycle carbon performance. This study provides a deeper understanding and insights into the lifecycle performance of residential buildings to facilitate further exploration of achieving a more sustainable and low-carbon built environment.

Recycling and optimum utilization of engineering sediment waste into low-carbon geopolymer paste for sustainable infrastructure

The development of underground space is an important trend for urban infrastructure in cities supporting socio-economic activities, while it also results in an enormous accumulation of sediment waste, which consumes vast land resources, causes serious environmental problems and endangers public safety. It is urgent to explore pathways of recycling sediment waste with low carbon impact for sustainable infrastructure. This study employed calcination and alkali activators to recycle sediment waste into geopolymer paste. The mechanical properties and working performance of recycled geopolymer paste were investigated and the underlying mechanism of this recycling scheme was revealed with microscale characterizations. Results showed that the compressive strength of recycled geopolymer paste could reach 50 MPa. The environmental impact of geopolymer paste and cement-based paste has been analyzed via life cycle assessment (LCA). Recycled geopolymer paste can save 310 kg CO2eq/t of carbon emissions, which is 39% lower than that of cement-based material. Moreover, the multi-criteria approach was adopted to evaluate geopolymer paste and cement paste considering mechanical properties, working performance, carbon emissions, energy consumption and cost, and geopolymer paste exhibits better overall performance. The findings inspire a construction waste management strategy and contribute to low-carbon construction materials for sustainable urban infrastructure.

A New Approach to the Viable Ranking of Zero-Carbon Construction Materials with Generalized Fuzzy Information

This paper aims to put forward an integrated decision approach, with generalized fuzzy information for the viable selection of zero- and low-carbon materials for construction. In countries such as India, the construction sector accounts for high pollution levels and high carbon emissions. To restore sustainability and eco-friendliness, the adoption of low-carbon materials for construction is essential and, owing to the multiple attributes associated with the selection, the problem is viewed as a multi-criteria decision-making problem. Earlier studies on material selection have faced certain issues, such as the following: (i) the modeling of uncertainty is an ordeal task; (ii) the flexibility given to experts during preference elicitation is lacking; (iii) the interactions among the criteria are not well captured; and (iv) a consideration of the criteria type is crucial for ranking. To alleviate these issues, the primary objective of this paper was to develop an integrated framework, with decision approaches for material selection in the construction sector that promote sustainability. To this end, generalized fuzzy information (GFI) was adopted as the preference style as it is both flexible and has the ability to model uncertainty from the following three dimensions: membership, non-membership, and hesitancy grades. Furthermore, the CRITIC approach was extended to the GFI context for calculating criteria weights objectively, by effectively capturing criteria interactions. Furthermore, the COPRAS technique was put forward with the GFI rating for ranking zero- and low-carbon construction materials, based on diverse attributes. The usefulness of the framework was demonstrated via a case example from India and the results showed that the design cost, the financial risk, safety, water pollution, and land contamination were the top five criteria, with blended cement, mud bricks, and bamboo as the top three material alternatives for zero- and low-carbon construction. Finally, a sensitivity analysis and a comparison with other methods revealed the theoretical positives of this framework’s robustness and consistency–but it also revealed some limitations of the proposed framework.

A framework for specifying low-carbon construction materials in government procurement: A case study for concrete in a new building investment

There are numerous strategies that can be used to reduce the embodied carbon footprint of real property investments, many of which can be accomplished for no additional cost and with minimal performance impacts. This study aims to propose the incorporation of the life cycle carbon quantification into the government procurement of real property process in order to reach out to low-carbon durable and sustainable structures as a theoretical contribution. As a practical contribution, an integrated embodied carbon measurement application is developed in a building information model (BIM) environment to act as a decision making tool in a government office building as a case study. It supports updating procurement policies and procedures to request construction materials with lower embodied carbon in construction. Analysis of concrete assembly groups in the case study along with determination of volume of concrete in each assembly is conducted to devise a reasonable list of elements to be considered for low-carbon concrete compliancy based on an industry average benchmarking approach. Considering the numerous concrete vendors that supply concrete products to a given region, a novel concrete embodied carbon measurement approach is proposed where cradle-to-construction impacts were accounted for. The outcome of the proposed integrated tool showed the procurement of concrete mix design from one specific nearby facility resulted in more efficient GHG reductions and the results showed especially the significance of considering transportation impacts of delivering ready-mixed concrete elements to the project site.

Developing carbon-neutral construction materials using wastes as carbon sink

Developing ecofriendly and low-carbon construction materials is essential to meet the ambitious target of global net zero emission by 2050. The concept of using wastes as carbon sink is taking advantage of alkaline solid wastes, which are rich in calcium or magnesium as a medium for absorbing carbon dioxide (CO2), and allowing manufacturing thermodynamically stable carbonate minerals for construction applications. Today, the major practical and successful applications of CO2 in the construction industry are through accelerated carbonation of granulated aggregates and precast concrete blocks manufactured with different proportions of calcium-rich waste materials. CO2 is also used as an activator in speciality nonhydraulic carbonate-binders or directly injected (in a liquid form) into fresh ready-mix concrete to produce a construction material with higher strength and lower carbon footprint. In addition, accelerated carbonation has become a promising approach to improve the quality of crushed concrete waste, and can be reused in new concrete to attain a sustainable concrete life cycle. In this paper, the progress in academic research of using CO2 in wastes and cement-based products as well as the key advantages and limitations related to the large scale application in the construction industry have been discussed in detail.

Earth as construction material in the circular economy context: practitioner perspectives on barriers to overcome.

The need for a vast quantity of new buildings to address the increase in population and living standards is opposed to the need for tackling global warming and the decline in biodiversity. To overcome this twofold challenge, there is a need to move towards a more circular economy by widely using a combination of alternative low-carbon construction materials, alternative technologies and practices. Soils or earth were widely used by builders before World War II, as a primary resource to manufacture materials and structures of vernacular architecture. Centuries of empirical practices have led to a variety of techniques to implement earth, known as rammed earth, cob and adobe masonry among others. Earth refers to local soil with a variable composition but at least containing a small percentage of clay that would simply solidify by drying without any baking. This paper discusses why and how earth naturally embeds high-tech properties for sustainable construction. Then the potential of earth to contribute to addressing the global challenge of modern architecture and the need to re-think building practices is also explored. The current obstacles against the development of earthen architecture are examined through a survey of current earth building practitioners in Western Europe. A literature review revealed that, surprisingly, only technical barriers are being addressed by the scientific community; two-thirds of the actual barriers identified by the interviewees are not within the technical field and are almost entirely neglected in the scientific literature, which may explain why earthen architecture is still a niche market despite embodying all the attributes of the best construction material to tackle the current climate and economic crisis. This article is part of the theme issue 'The role of soils in delivering Nature's Contributions to People'.

Scaling low-carbon construction materials

Philip Isaac and Jonny Hawkshaw review the potential for materials with lower embodied carbon to be used more widely in both small-scale domestic projects and larger-scale residential and commercial projects.

Cement-treated recycled glass and crushed rock blends: modulus of rupture and stiffness properties

ABSTRACT Recycled waste materials are increasingly being used as low carbon construction materials in civil infrastructure works, as recycled materials have significant carbon savings compared with virgin quarried materials. In this research, the stiffness and modulus of rupture properties of crushed rock (CR) blended with recycled glass (RG) were evaluated. The engineering properties of the four cement-treated CR/RG blends evaluated were: 100% CR100 (100CR), 90% CR with 10% RG (CR90/RG10), 80% CR with 20% RG (CR80/RG20), 70% CR with 30% RG (CR70/RG30). 3% dosage of general blend (GB) cement was used in all the RG/ CR blends. The results indicated that cement-treated RG/CR blends, with up to 20% RG, are suitable as pavement subbase materials. Unconfined compression strength (UCS) values met the minimum requirement for 7 days of curing for all the CR/RG blends. The results of repeated load triaxial (RLT) tests and flexural beam tests were found to be within the ranges reported for the previous testing on other accepted recycled and quarry products. Based on this laboratory assessment, RG can be recommended for incorporation as a supplementary material in cement-treated CR pavement applications, which will increase the uptake of recycled products as a civil engineering construction material.

Approach to establish carbon emission benchmarking for construction materials

The construction industry will play a crucial rule in global carbon emission reduction as the embodied carbon of construction materials shares an increasing portion of a building’s life-cycle carbon dioxide (CO2) emissions. In order to reduce CO2 emissions by selecting low-carbon construction materials, it is inevitable that a proper benchmarking mechanism and severity representation of different emission levels should be established, as benchmarking is a useful tool for pursuing consumer purchasing habits toward selection of low-carbon materials. In addition, high variation of carbon emissions is observed among the large number of studies and databases, and there is no consensus on how these should be used in practice. Therefore, standardization and benchmarking of emissions for construction materials are essential. In this study, a novel benchmarking approach was developed for embodied carbon emissions of commonly used construction materials by applying a fuzzy set theory. Given that a reliable local database is lacking, the benchmark was developed by referring to the existing carbon inventories, linguistic variables of severity levels from a questionnaire survey, and the fuzzy set analysis. A six-step method was proposed based on a horizontal and graphical approach. This study offers an alternative approach in benchmarking where a database or a set of real data is not available. It is expected that the developed benchmarks will help practitioners and decision-makers compare the embodied CO2 emissions of a specific batch of construction materials and select low-carbon materials in construction projects.

Effect of Steel Slag and Granulated Blast-furnace Slag on the Mechanical Strength and Pore Structure of Cement Composites

Reuse of solid industrial wastes is an effective approach to develop low-carbon construction materials. This paper examines how two materials, steel slag (ST) and granulated blast-furnace slag (SL) impact the mechanical performance and pore structure of cement-based systems. Analysis was done on the variations of the porosity, pore size, and pore volume distribution with the curing age and replacement content, and the fractal dimensions of pore surfaces. The results suggested that systems with both supplementary materials had lower early strengths than pure cement, but could generally surpass pure cement paste after 90 d; higher SL content was particularly helpful for boosting the late strengths. The addition of ST increased the porosities and mean pore sizes at each age, and both increased with ST content; SL was helpful for decreasing the system’s late porosity (especially harmless pores below 20 nm); The lowest porosity and mean pore size were obtained with 20% SL. Both systems had notably fractal characteristics on pore surfaces, with ST systems showing the highest dimensions at 10% ST, and SL systems at 20% SL. Compressive strength displayed a significant linear increase with fractal dimension.

An input–output virtual laboratory in practice – survey of uptake, usage and applications of the first operational IELab

ABSTRACTThe Industrial Ecology Virtual Laboratory (IELab) is a collaborative cloud-computing platform for compiling large-scale, high-resolution, enviro-socio-economic accounts based on multi-region input–output tables and for conducting integrated sustainability assessment projects. These include, for example, assessments of biofuels and low-carbon construction materials or high-resolution waste modelling. This contribution provides a structured review of IELab applications that were published in either peer-reviewed journal papers or in the form of conference proceedings. The main research question posed is ‘What are the specific features of IELab that were used in the research and could the research have happened without them?’ It is investigated whether the IELab has actually and truly enabled new research. A detailed analysis of IELab characteristics and their usage is presented. The results can help with the design of new research projects and inform existing and prospective users of the IELab about the options for academic research and practical applications.

Mechanical characterisation of structural laminated bamboo

Low carbon construction materials are needed to reduce carbon dioxide emissions in the built environment. Laminated bamboo is an example of such a material. However, to be used in structural applications, fundamental mechanical properties are needed to establish the design values used in architecture and engineering practice. Recent studies on laminated bamboo have focused on the use of timber standards for small clear specimens, with little work published on structural-scale testing. The work presented in this paper is the first study to utilise structural-scale test methods for timber in a multi-laboratory test programme to investigate all mechanical properties of an outdoor laminated bamboo product. The study provides a comparison of the full-scale structural performance with conventional timber and a pathway for use in engineering design and practice. The work shows that laminated bamboo is comparable to conventional timber and timber-based products in structural properties and forms a foundation for the use of laminated bamboo in design and construction.

A Study on Life Cycle CO2 Emissions of Low-Carbon Building in South Korea

There have been much interest and many efforts to control global warming and reduce greenhouse gas (GHG) emissions throughout the world. Recently, the Republic of Korea has also increased its GHG reduction goal and searched for an implementation plan. In buildings, for example, there have been technology developments and deployment policies to reduce GHG emissions from a life cycle perspective, covering construction materials, building construction, use of buildings and waste disposal. In particular, Korea’s Green Standard for Energy and Environmental Design is a certification of environmentally-friendly buildings for their energy saving and reduction of environmental pollution throughout their lives. In fact, the demand and adoption of the certification are rising every year. In construction materials and buildings, as a result, an environmentally-friendly aspect has become crucial. The importance of construction material and building development technologies that can reduce environmental load by diminishing GHG emissions in buildings has emerged. Moreover, there has been a rising necessity to verify the GHG reduction effects of buildings. To assess the reduction of carbon emissions in the buildings built with low-carbon construction technologies and materials, therefore, this study estimated life cycle carbon emissions in reference buildings in which general construction materials are used and in low-carbon buildings. For this, the carbon emissions and their reduction from construction materials (especially concrete) between conventional products and low-carbon materials were estimated, using Life Cycle Assessment (LCA). After estimating carbon emissions from a building life cycle perspective, their reduction in low-carbon buildings compared to the reference buildings was reviewed. The results found that compared to conventional buildings, low-carbon buildings revealed a 25% decrease in carbon emissions in terms of the reduction of Life Cycle CO2 (LCCO2) per unit area. If diverse production technologies and sales routes are further developed for low-carbon construction materials, carbon emission reduction effects would considerably increase.

Durability Performance of Concrete Structures Built with Low Carbon Construction Materials

Here, we demonstrate the feasibility of industrial application of low carbon supplementary cementitious materials (i.e. geopolymer concrete) by investigating the durability performance of eight years aged reinforced geopolymer concrete structure exposed to ambient environment. The corrosion performance of reinforcement bar in concrete and permeability characteristic of cover concrete is investigated by using non-destructive techniques. The results reveal that the reinforcement in geopolymer concrete exhibits higher corrosion risk in atmospheric environment and this attributes to the deterioration of long term durability performance for geopolymer concrete.