Decoding Concrete’s Environmental Impact: A Path Toward Sustainable Construction

Abstract

The construction industry is a major contributor to global greenhouse gas emissions, driven by the extensive use of conventional concrete in building activities. This study evaluates the environmental impacts of various concrete types, including innovative alternatives, using a computational life cycle assessment (LCA) model tailored to the Australian context. Key stages considered include raw material extraction, production, transportation, and end-of-life recycling. Results demonstrate that replacing 40% of cement with supplementary cementitious materials (SCMs) such as fly ash reduces global warming potential (GWP) by up to 25% compared to conventional concrete. Furthermore, carbonation curing technology shows a 15% reduction in ${\mathrm{C}\mathrm{O}}_2$ emissions during the production phase, underscoring its potential to significantly enhance sustainability in construction. High-strength concrete poses significant ecological challenges; however, incorporating SCMs such as fly ash, blast-furnace slag, and silica fume effectively mitigates these impacts. Recycling 60% of concrete demolition waste further decreases environmental impacts by over 20%, aligning with circular economy principles and supporting resource recovery. The findings provide actionable insights for engineers, architects, and policymakers, facilitating the design of sustainable concrete solutions that balance structural performance with reduced ecological footprints. Future research should explore dynamic modelling and broader socio-economic factors to refine sustainable practices. This study underscores the critical importance of adopting innovative materials and recycling practices to minimise the environmental impact of construction activities globally.

1. Introduction

The aggregate real value of residential land and houses surged from $1.6 trillion to $9.5 trillion between 1988 and 2021, with a notable increase in per capita value. This surge was triggered by the 2008–2009 global financial crisis and the COVID-19 health and economic crisis [1,2]. In the Australian housing market, there has also been a notable increase in median house prices between 2012 and 2023. This trend is particularly pronounced in Sydney, where prices have risen significantly from AUD 600,000 to over AUD 1.2 million [3].

According to a research report produced by the Australian Housing and Urban Research Institute (AHURI), it is imperative for Australia to increase its current supply of social housing threefold by 2036 [4]. This expansion is necessary to address the existing backlog of demand, as well as accommodate the anticipated growth in future housing demands. The disproportionate emphasis on addressing housing needs, without adequate consideration for sustainable design practices from the outset, will inevitably result in environmental repercussions associated with the proliferation of construction activities [5].

The progress of construction activities is intricately linked to the expansion of concrete manufacturing to meet the demands of these projects [6]. The global production of concrete contributes to over five per cent of annual anthropogenic carbon dioxide emissions, primarily due to the production of cement clinker [7,8]. It is unsurprising that there is a strong correlation between the production of cement and the rate at which the population is growing. Cement is widely acknowledged as a highly significant material in modern society, and its importance is projected to endure due to anticipated trends in development, urbanisation, and population growth. Its demand is witnessing a notable surge as a result of the substantial expansion of the population [9,10].

Since the publication of the Brundtland [11] report, the concept of sustainability and sustainable design has garnered increasing attention on a global scale. It is well acknowledged that buildings use a significant quantity of resources during their entire life cycle, including both non-renewable energy and materials. Construction operations have been shown to have substantial adverse effects on the environment, including the contamination of air and water, as well as the discharge of waste [12]. The use of life cycle design principles has been advocated via the incorporation of design strategies such as deconstruction and demolition, which aim to enhance the ease of reusing and recycling building components and materials [13].

Using accelerated carbonation to improve the strength and quality of concrete has been suggested by some researchers in recent years [14,15]. However, there is limited evidence in the literature that may prove the influence of the carbonated acceleration technique in the early stage of concrete procedure on both the strength and environmental impact of concrete products. Geopolymer concrete emerges as a compelling solution for incorporating industrial by-products such as fly ash and slag into traditional Portland cement alternatives. By repurposing these waste materials, geopolymer concrete not only reduces environmental impact but also extends the life cycle of resources involved in concrete production [16]. This innovative approach aligns seamlessly with the principles of a circular economy, transforming industrial waste into a valuable resource while fostering sustainability and resilience in construction practices [17]. The application of these evaluation principles will enable the assessment and comparison of the impacts of traditional and innovative concrete technologies. Subsequently, designers and engineers can ascertain the appropriate concrete variant to employ for their project with the aim of mitigating the ecological impacts associated with the building’s construction.

To address these above challenges, this study employs a computational life cycle assessment (LCA) model tailored to the Australian context. The model evaluates the environmental impacts of various concrete types across key life cycle stages, including raw material extraction, production, transportation, and end-of-life recycling. The analysis incorporates regional datasets (e.g., Ecoinvent and AusLCI) and adheres to standards such as ISO 14025 and ISO 14040/44 [18,19], ensuring methodological robustness and alignment with international best practices.

The research objectives are: (1) Develop a comprehensive LCA model to assess the environmental impacts of concrete across different compressive strengths and material compositions; (2) Compare the effectiveness of supplementary cementitious materials (SCMs) such as fly ash, blast-furnace slag, and silica fume, alongside carbonation curing technology, in reducing greenhouse gas emissions; (3) Evaluate the role of recycling construction waste, particularly concrete debris, in enhancing environmental performance and aligning with circular economy principles.

This research aims to provide actionable insights for engineers, architects, and policymakers, enabling the development of sustainable concrete solutions that balance structural performance with reduced ecological footprints. By addressing the current gaps in the literature and emphasising practical implications, this study contributes to advancing sustainable construction practices in Australia and beyond.

2. Research Objectives and Framework

This research employs life cycle assessment (LCA) as a methodology to evaluate and compare the environmental impacts associated with various types of concrete utilised in real-world scenarios. These include conventional concrete as well as concrete products that utilise the ${\mathrm{C}\mathrm{O}}_2$ curing method.

The primary objective of this research is to develop a computational life cycle assessment (LCA) model tailored to the Australian context, enabling the assessment of environmental impacts across key stages such as raw material extraction, production, transportation, utilisation, and end-of-life recycling. By integrating regional datasets (e.g., AusLCI and Ecoinvent) and adhering to international standards (ISO 14025, ISO 14040/44 [18,19,20]), the model ensures transparency, reliability, and applicability within the local and broader global contexts.

The study further aims to evaluate the effectiveness of supplementary cementitious materials (SCMs), such as fly ash, blast-furnace slag, and silica fume, in mitigating greenhouse gas emissions and reducing resource depletion. By comparing SCM replacement levels of 30% and 40%, the research explores optimal trade-offs between environmental performance, structural integrity, and economic feasibility. Additionally, the potential of carbonation curing technology to reduce ${\mathrm{C}\mathrm{O}}_2$ emissions during concrete production is investigated, highlighting its viability as a complementary approach to sustainable construction. Another key focus is on the role of recycling post-demolition concrete. The study quantifies the environmental benefits of recycling under various rates (e.g., 40%, 60%, and 80%) while addressing challenges such as sorting, contamination, and economic barriers. This aligns the research with circular economy principles, emphasising resource recovery and waste minimisation.

To achieve these objectives, the research follows a structured framework. It begins with an extensive literature review to identify gaps in existing knowledge and contextualise the study’s significance. A robust LCA model is then developed in compliance with ISO standards, incorporating clear system boundaries, functional units, and reliable data sources. The analysis evaluates environmental impacts across concrete strength levels (20 MPa to 100 MPa) and SCM replacement scenarios, while sensitivity analysis ensures robustness by addressing uncertainties in data and assumptions. Results are interpreted to provide actionable recommendations for engineers, architects, and policymakers, enabling the adoption of sustainable practices in construction. By integrating innovative materials, advanced technologies, and recycling strategies, this research offers a comprehensive pathway to reducing the environmental impact of concrete production and supports the transition toward more sustainable construction practices globally.

The paper is structured in the following manner. The article includes Section 1 that presents the motivations for conducting research, performing estimations, and conducting environmental impact assessments of concrete throughout a project’s lifespan. Section 2 defines the structure and research goals, Section 3 discusses the research methodologies and the process of model building, Section 4 highlights the findings and provides discussions, and Section 5 concludes the paper.

3. Research Methodology

3.1. Assessment Model Development

The practice of generating Environmental Product Declarations (EPDs) is becoming more prevalent among manufacturers of materials and products [21,22]. EPDs are developed using a standardised set of rules known as Product Category rules (PCRs). The concept of a “product category” has significant importance within the context of EPDs. It refers to a distinct classification of items that have a common purpose or function. PCRs establish the parameters for a particular product category and outline the prerequisites that must be satisfied when formulating an environmental product declaration for items falling within this category [23,24].

The EPD of this study provides an account of the environmental impacts associated with the utilisation of carbon dioxide in the curing process of one cubic metre of concrete, resulting in the creation of a structure that is environmentally sustainable. The concrete products evaluated in this study are categorised into three primary types: standard class, low-carbon, and specialised concrete products.

a.

Goal and scope definition

The model is performed in conformance with ISO 14025, ISO 14040/44, ISO 21930 [18,19,20,25], and EN 15804 [26], as well as the PCR from UL Environment, Part A and Part B [27]. The components of studied concrete types are calculated automatically in MS Excel by input of concrete compressive strength, aggregate types, and external conditions as requirements in Australian standard AS 1379:2007 [28]. The model is developed based on the combination of the Australian Life Cycle Inventory Database Initiative [24] and the Ecoinvent Database v3 [25] database and used in SimaPro 9.5 software. However, certain limitations and assumptions in data collection are acknowledged. For instance, AusLCI provides region-specific data tailored to Australian contexts, but it may not fully capture variations in material properties, energy consumption, and transportation impacts in other geographical regions. Similarly, while Ecoinvent Database v3 is comprehensive, its global datasets may not align perfectly with local Australian conditions, potentially introducing discrepancies. Assumptions such as average transport distances (e.g., 50 km from batching plant to construction site) and energy usage during production are standardised for calculation simplicity, though these may not represent all real-world scenarios [29,30]. The exclusion of capital assets, such as infrastructure and plant, was deemed necessary to streamline the scope of the study and focus solely on the operational impacts of concrete production. While this decision simplifies the modelling process, it may underestimate the total environmental burden, particularly in scenarios where infrastructure contributes significantly to the life cycle impacts. Addressing these limitations in future research by integrating dynamic, region-specific datasets and performing sensitivity analyses could enhance the robustness and applicability of the model for LCA pra. To address potential uncertainties in input data, this paper acknowledges variability in regional datasets and standardised assumptions such as transport distances and energy consumption. Sensitivity analysis will be incorporated to quantify the influence of key parameters on environmental outcomes.

b.

Functional unit

This functional unit used in the paper analyses the composition and life cycle environmental impacts of 1 cubic meter of concrete in the compressive strength range of 20–100 MPa in accordance with the AS 1379:2007 standard [28].

c.

System boundaries

The description of the system boundary establishes the specific processes and life cycle phases that are included within the scope of the life cycle assessment research. Figure 1 displays the system boundary diagram for concrete types under this research. The system boundary encompasses many processes involved in concrete production, which include the inflow and outflow of energy and materials. The resources that are shared across many entities are visually represented with grey shading in Figure 1 in order to enhance clarity and comprehension. The system boundary excluded capital assets, such as infrastructure and plant. A comprehensive analysis of the whole fuel cycle was conducted for all energy consumption activities. To quantify GHG during the life cycle stages, this study adopts region-specific emission factors and energy consumption data from databases such as AusLCI and Ecoinvent, ensuring that the results are representative of local conditions. These databases provide standardised values for GHG emissions associated with material extraction, production, and transportation. For instance, emissions from cement production are calculated based on the average clinker-to-cement ratio and the associated energy inputs, while transportation emissions account for the distance travelled and vehicle efficiency.

3.2. Life Cycle Carbon Dioxide Emissions Breakdown

To enhance the understanding of the ecological implications of a particular asset, it is necessary to analyse its life cycle, which is segmented into various stages and modules, as specified in the ISO 21930:2017 [25] and AS ISO 14040:2019 [31] guidelines for life cycle environment assessment (refer to Figure 2). The subject matter under consideration in this guidance document pertains specifically to the quantification of greenhouse gas emissions (GHG) and its associated environmental impacts.

a.

Environmental impacts in the product stage

The product stage, commonly referred to as the “cradle to gate” phase, is demonstrated through three modules A1 to A3. The quantity of GHG emissions generated over the production period of a product includes the extraction, processing, manufacturing, and transportation of materials between these modules, up until the time when the product departs the factory gate for delivery to its intended construction site (Refer to Equation (1)):

$${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{P}\mathrm{r}\mathrm{o}\mathrm{d}\mathrm{u}\mathrm{c}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}} = {\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{A}1}+ {\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{A}2}+ {\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{A}3}$$

(1)

where ${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{P}\mathrm{r}\mathrm{o}\mathrm{d}\mathrm{u}\mathrm{c}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}}$ presents the total amount of GHG emission released in the production phase; ${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{A}1}$ shows the amount of GHG emissions released from material extraction and processing activities; ${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{A}2}$ refers to the measurement of GHG emissions released by a vehicle during the transportation of materials; and ${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{A}3}$ presents the GHG emissions amount relating to the manufacture module of materials. In this study, beside the normal class concrete, one novel type of concrete is assessed is accelerated carbonation concrete. Although the carbon dioxide injection varied significantly from batch to batch, it is estimated to be 0.15% of the cement weight [32,33,34]. The ${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{P}\mathrm{r}\mathrm{o}\mathrm{d}\mathrm{u}\mathrm{c}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}}$ value in this case will be calculated as in Equation (2)):

$${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{P}\mathrm{r}\mathrm{o}\mathrm{d}\mathrm{u}\mathrm{c}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}} = {\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{A}1}+ {\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{A}2}+ {\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{A}3}+ {\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{c}\mathrm{u}\mathrm{r}\mathrm{i}\mathrm{n}\mathrm{g}}$$

(2)

In the production process, the primary contributor to energy consumption and subsequent ${\mathrm{C}\mathrm{O}}_2$ emissions is predominantly observed during the drying procedure and thermal activation processes.

b.

Environmental impacts in the construction stage

The amount of GHG emissions in the modules A4 and A5 in the construction activities stage are produced from the transportation of materials and products to the construction site, the energy consumption resulting from on-site activities such as the use of site offices and machinery. This quantity also related with the manufacturing, transit, and disposal of items that are wasted on site (Refer to Equation (3)):

$${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{C}\mathrm{o}\mathrm{n}\mathrm{s}\mathrm{t}\mathrm{r}\mathrm{u}\mathrm{c}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}} = {\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{A}4}+ {\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{A}5}$$

(3)

where ${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{C}\mathrm{o}\mathrm{n}\mathrm{s}\mathrm{t}\mathrm{r}\mathrm{u}\mathrm{c}\mathrm{i}\mathrm{t}\mathrm{o}\mathrm{n}}$ shows the total amount of GHG emissions released during the construction phase; ${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{A}4}$ refers to the quantity of GHG emissions released during materials and equipment transport activities; and ${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{A}5}$ presents the amount of GHG emissions released during the construction module.

c.

Environmental impacts during a building’s life

In the period of the building utilisation and maintenance, the GHG quantity are generated as a result of the utilisation (B1), maintenance (B2), repair (B3), replacement (B4), refurbishment (B5), energy consumption (B7), and water usage (B8) during the period in which the building is actively used. In addition to adhering to the ISO 21930:2017 guidelines [25], this study incorporates module B6, which pertains to the transportation activities associated with modules B3, 4, and 5 (Refer to Equation (4)):

$${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{U}\mathrm{t}\mathrm{i}\mathrm{l}\mathrm{i}\mathrm{s}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}/\mathrm{M}\mathrm{a}\mathrm{i}\mathrm{n}\mathrm{t}\mathrm{e}\mathrm{n}\mathrm{a}\mathrm{n}\mathrm{c}\mathrm{e} } ={\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{B}1–5}+{\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{B}6}+{\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{B}7}$$

(4)

where ${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{U}\mathrm{t}\mathrm{i}\mathrm{l}\mathrm{i}\mathrm{s}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}/\mathrm{M}\mathrm{a}\mathrm{i}\mathrm{n}\mathrm{t}\mathrm{e}\mathrm{n}\mathrm{a}\mathrm{n}\mathrm{c}\mathrm{e}}$ presents the total amount of GHG emissions in the period of the building utilisation and maintenance; ${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{B}1–5}$ refers to GHG emissions from the use of materials and equipment during this period; ${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{B}6}$ refers to the quantity of GHG emissions from the use of materials and equipment relating to all maintenance, repair, replacement, and refurbishment activities; and ${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{B}7}$ presents the amount of GHG emissions convert from the energy consumption quantity. While the frequency of repair and restoration of concrete buildings is relatively low, the evaluation of the ${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{B}6}$ value becomes relevant when a building’s external condition reaches a state of substantial erosion [35].

d.

Environmental impacts in Demolition/Recycling/Disposal stage

The emissions related to different activities, such as demolition, deconstruction, transportation of items off-site, waste processing, and disposal of materials, during the building’s end-life period are considered and included in Modules C1 to C4 (Refer to Equation (5)):

$${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{D}\mathrm{e}\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{i}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}/\mathrm{R}\mathrm{e}\mathrm{c}\mathrm{y}\mathrm{c}\mathrm{l}\mathrm{i}\mathrm{n}\mathrm{g}/\mathrm{D}\mathrm{i}\mathrm{s}\mathrm{p}\mathrm{o}\mathrm{s}\mathrm{a}\mathrm{l}}={\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{C}1}+{\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{C}2}+{\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{C}3}+{\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{C}4}$$

(5)

where ${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{D}\mathrm{e}\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{i}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}/\mathrm{R}\mathrm{e}\mathrm{c}\mathrm{y}\mathrm{c}\mathrm{l}\mathrm{i}\mathrm{n}\mathrm{g}/\mathrm{D}\mathrm{i}\mathrm{s}\mathrm{p}\mathrm{o}\mathrm{s}\mathrm{a}\mathrm{l}}$ presents the total amount of GHG emissions in the final period of the building, including disposal and recycling activities; ${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{C}1}$ refers to the quantity of GHG emissions released during this period; ${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{C}2}$ refers to the quantity of GHG emissions of demolition debris transport; and ${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{C}3}$ and ${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{C}4}$ represent the amount of GHG emissions equivalent relating disposal and recycling periods, respectively.

Despite steady improvements in recycling and resource recovery practices, several challenges persist in the demolition and recycling stages that significantly influence the overall GHG emissions. Contaminants such as gypsum and hazardous materials (e.g., heavy metals) in recycled aggregates require additional sorting and processing, leading to higher emissions during the process involving to the parameters of ${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{C}3}$ and ${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{C}4}$ [36]. These contaminants not only increase processing complexity but also affect the quality of recycled aggregates, limiting their reuse in high-strength applications.

In addition, variations in recycling rates across Australian states highlight discrepancies in regional waste management policies and practices. For example, South Australia achieved an 81% resource recovery rate in 2020-21 through extensive recycling programs and energy recovery strategies, setting an example for other jurisdictions (Refer to

Table 1. Industrial recycling rates in Australia by state.

Australian’s State	2010/2011	2020/21
Northern Territory	19%	19%
Queensland	47%	47%
Tasmania	51%	51%
Victoria	67%	67%
New South Wales	67%	67%
Western Australia	64%	64%
Australian Capital Territory	69%	69%
South Australia	77%	81%
Average rate	57.63%	58.13%

) [37]. This achievement can be attributed mostly to the extensive implementation of recycling practices, complemented by a combination of energy recovery and waste reuse strategies. The following jurisdictions, listed in sequential order, along with their respective recovery rates in parentheses, were as follows: the Australian Capital Territory (69%), New South Wales and Victoria (67%), Western Australia (64%), Tasmania (51%), Queensland (47%), and the Northern Territory (19%) [38]. The recovery and recycling rates at the national level are showing an increasing trajectory. In Australia, resource recovery rates have steadily increased, rising from 57.63% in the 2010–2011 fiscal year to 58.13% in the 2020–2021 fiscal year. The differences underline the need for uniform national standards to improve recycling efficiency and reduce emissions from disposal and recycling periods.

Concrete debris to be reused accounts for approximately 60% of reprocessed masonry materials. Further advancements in sorting and recycling technologies, coupled with policy support to standardise processes, are essential to maximising resource recovery rates and minimising environmental impacts [39]. Equation (6) assumes a quantity of disposal of 35% (which is derived from 60% × 58.13%):

$${\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{C}4}=35\%{\mathrm{G}\mathrm{H}\mathrm{G}}_{\mathrm{C}3}$$

(6)

3.3. Concrete Mixture Analysed

The combinations studied included a wide range of concretes with strengths ranging from 20 and 100 MPa. The quantity of cement increases significantly with strength, starting at 239.13 kg for 20 MPa and reaching 634.62 kg for 100 MPa. The model uses coarse aggregate as crushed gravel with an average size between 9.5 mm and 25 mm, which is appropriate for both conventional and high-strength concrete [40,41,42,43]. The amount of coarse aggregate remains relatively consistent, with a slight decrease as the concrete strength increases, ranging from 1432.45 kg (20 MPa) to 1341.62 kg (100 MPa). Supplementary cementitious materials (SCMs), such as blast-furnaced slag, fly ash, and silica fume, are supplanted with 30% and 40% of cement content as options for obtaining Green-Star certification for green-building projects in Australia [44,45]. The anticipated slump range used in the development of the model is 30 to 100 mm, as the model’s focus is on general-purpose concrete applications. Varying slumps and aggregate sizes determine the quantity of water used, which in turn determines the water-to-cement ratio of the various concrete types. The water content remains relatively constant across all strength classes, ranging from 193.85 kg to 191.9 kg.

Relating to electricity and fuel using to develop the model, the assessed quantity of ${\mathrm{C}\mathrm{O}}_2$ and other air pollutants would vary between regions and nationally depending on the fuel mix utilised to produce energy [46,47]. In this model, energy consumption of each phase of concrete’s life cycle can be adjusted on a national scale. However, for the purpose of producing results and within the scope of this study, the aforementioned data will be adjusted within Australian LCI datasets [48]. If any units or systems were not available in Australian paths, global databases were used to do the research.

Concerning the transportation of materials and concrete products, vehicle speed restrictions range from 10 km/h in shared zones to 100 km/h on highways. The average distance travelled from a batch plant to a construction site is assumed to be 50 km in the calculation [49,50]. The average fuel consumption for transporting materials and machinery to concrete batching facilities using the standard 32-metric-tonnes truck is assessed.

A 100 kW pump engine was adopted with a concrete flow rate of 20 m³ and an energy consumption of 5 kWh/m3 of concrete [51]. The fuel consumption amount from a 100 kW pump engine (with a consumption rate of 180 g/(hp × h) and 1 mechanical horsepower = 0.745 kW) working for two hours, which is adopted as the best concrete workability period, can be converted into 0.241 kg/KWh [52,53].

4. Results and Discussion

4.1. Contribution of Cement to Environmental Impacts

The creation and application of concrete in construction projects have detrimental effects on the environment [54]. However, this study’s model demonstrates the potential for mitigating these impacts through various treatments incorporated within and beyond the concrete production process. The analysis process in

Table 2. Comparison of environmental impacts for ordinary concrete types—CML-IA baseline V3.09/EU25.

Impact Category	Unit	20 MPa		35 MPa		40 MPa
		Normal	${\mathrm{C}\mathrm{O}}_2$ Curing	Normal	${\mathrm{C}\mathrm{O}}_2$ Curing	Normal	${\mathrm{C}\mathrm{O}}_2$ Curing
Abiotic depletion	kg Sb-eq	$8.95\times {10}^{-4}$	$5.95\times {10}^{-4}$	$9.00\times {10}^{-4}$	$5.99\times {10}^{-4}$	$9.02\times {10}^{-4}$	$6.00\times {10}^{-4}$
Abiotic depletion (fossil fuels)	MJ	2269.647	2026.065	2285.067	2039.723	2290.023	2044.113
Global warming (GWP100a)	$\mathrm{kg}{\mathrm{C}\mathrm{O}}_2$-eq	299.710	268.954	301.797	270.819	302.468	271.419
Ozone layer depletion (ODP)	kg CFC-11-eq	$1.88\times {10}^{-6}$	$1.72\times {10}^{-6}$	$1.89\times {10}^{-6}$	$1.73\times {10}^{-6}$	$1.90\times {10}^{-6}$	$1.73\times {10}^{-6}$
Human toxicity	kg 1.4-DB-eq	277.587	217.4607	279.5103	218.949	280.1285	219.4274
Fresh water aquatic ecotox.	kg 1.4-DB-eq	505.216	490.055	508.810	493.540	509.965	494.660
Marine aquatic ecotoxicity	kg 1.4-DB-eq	549,661.3	516,825.2	553,545	520,471.4	554,793.4	521,643.5
Terrestrial ecotoxicity	kg 1.4-DB-eq	0.745	0.492	0.751	0.495	0.752	0.496
Photochemical oxidation	$\mathrm{kg}{\mathrm{C}}_2{\mathrm{H}}_4$-eq	$3.92\times {10}^{-2}$	$3.30\times {10}^{-2}$	$3.95\times {10}^{-2}$	$3.32\times {10}^{-2}$	$3.96\times {10}^{-2}$	$3.33\times {10}^{-2}$
Acidification	$\mathrm{kg}{\mathrm{S}\mathrm{O}}_2$-eq	0.826	0.738	0.831	0.743	0.833	0.744
Eutrophication	$\mathrm{kg}{\mathrm{P}\mathrm{O}}_4$-eq	$6.25\times {10}^{-1}$	$5.93\times {10}^{-1}$	$6.30\times {10}^{-1}$	$5.98\times {10}^{-1}$	$6.31\times {10}^{-1}$	$5.99\times {10}^{-1}$
Impact category	Unit	50 MPa		65 MPa		80 MPa		100 MPa
		Normal	${\mathrm{C}\mathrm{O}}_2$ curing	Normal	${\mathrm{C}\mathrm{O}}_2$ curing	Normal	${\mathrm{C}\mathrm{O}}_2$ curing	Normal	${\mathrm{C}\mathrm{O}}_2$ curing
Abiotic depletion	kg Sb eq	$9.04\times {10}^{-4}$	$6.01\times {10}^{-4}$	$9.05\times {10}^{-4}$	$6.02\times {10}^{-4}$	$9.07\times {10}^{-4}$	$6.03\times {10}^{-4}$	$9.12\times {10}^{-4}$	$6.06\times {10}^{-4}$
Abiotic depletion (fossil fuels)	MJ	2294.662	2048.221	2297.291	2050.55	2303.312	2055.883	2315.176	2066.391
Global warming (GWP100a)	$\mathrm{kg}{\mathrm{C}\mathrm{O}}_2$-eq	303.096	271.980	303.452	272.298	304.267	273.026	305.873	274.461
Ozone layer depletion (ODP)	kg CFC-11 eq	$1.90\times {10}^{-6}$	$1.73\times {10}^{-6}$	$1.90\times {10}^{-6}$	$1.74\times {10}^{-6}$	$1.91\times {10}^{-6}$	$1.74\times {10}^{-6}$	$1.92\times {10}^{-6}$	$1.75\times {10}^{-6}$
Human toxicity	kg 1.4-DB-eq	280.707	219.875	281.035	220.129	281.786	220.710	283.266	221.855
Fresh water aquatic ecotox	kg 1.4-DB-eq	511.046	495.708	511.659	496.302	513.062	497.663	515.827	500.343
Marine aquatic ecotoxicity	kg 1.4-DB-eq	555,961.8	522,740.4	556,623.9	523,361.9	558,140.6	524,785.9	561,128.6	527,591.1
Terrestrial ecotoxicity	kg 1.4-DB-eq	0.754	0.497	0.755	0.497	0.757	0.498	0.761	0.501
Photochemical oxidation	$\mathrm{kg}{\mathrm{C}}_2{\mathrm{H}}_4$-eq	$3.97\times {10}^{-2}$	$3.34\times {10}^{-2}$	$3.97\times {10}^{-2}$	$3.34\times {10}^{-2}$	$3.98\times {10}^{-2}$	$3.35\times {10}^{-2}$	$4.00\times {10}^{-2}$	$3.37\times {10}^{-2}$
Acidification	$\mathrm{kg}{\mathrm{S}\mathrm{O}}_2$-eq	0.835	0.746	0.836	0.747	0.838	0.749	0.842	0.753
Eutrophication	$\mathrm{kg}{\mathrm{P}\mathrm{O}}_4$-eq	$6.33\times {10}^{-1}$	$6.00\times {10}^{-1}$	$6.33\times {10}^{-1}$	$6.01\times {10}^{-1}$	$6.35\times {10}^{-1}$	$6.02\times {10}^{-1}$	$6.38\times {10}^{-1}$	$6.06\times {10}^{-1}$

reveals a gradual rise in impact across various categories as the concrete strength increases. The alterations in mass of the components constituting a cubic meter of concrete collectively contribute to its environmental impact. Nevertheless, the predominant influence in the calculated results stems from the volume of cement. Table 2 indicates that the abiotic depletion impact increases from 7.52 $\times {10}^{-4}$ to 7.68 $\times {10}^{-4}$ kg Sb-eq, the global warming impact shifts from 2.59 $\times {10}^2$ to 2.65 $\times {10}^2$ kg ${\mathrm{C}\mathrm{O}}_2$-eq, the ozone layer depletion impact changes from 9.96 $\times {10}^{-7}$ to 1.02 $\times {10}^{-6}$ kg CFC-11-eq, the photochemical oxidation impact changes from 2.99 $\times {10}^{-2}$ to 3.05 $\times {10}^{-2}$ kg ${\mathrm{C}}_2{\mathrm{H}}_4$-eq, and the eutrophication impact changes from 1.82 $\times {10}^{-1}$ to 1.85 $\times {10}^{-1}$ kg ${\mathrm{P}\mathrm{O}}_4$-eq when the concrete strength is increased from 20 MPa to 100 MPa.

Research highlights that cement’s contribution is particularly significant in acidification and human toxicity categories due to emissions of sulphur oxides (${\mathrm{S}\mathrm{O}}_{\mathrm{x}}$) and heavy metals during clinker production (the acidification impact rises from 6.65 $\times {10}^{-1}$ to 6.79 $\times {10}^{-1}$ kg ${\mathrm{S}\mathrm{O}}_2$-eq; the human toxicity impact rises from 6.33 × 10 to 6.47 × 10 kg 1.4-DB eq within the studied concrete strength range). For example, the acidification potential is closely linked to ${\mathrm{N}\mathrm{O}}_{\mathrm{x}}$ and ${\mathrm{S}\mathrm{O}}_{\mathrm{x}}$ emissions, which can be substantially reduced by replacing cement with SCMs such as fly ash and slag [55]. Similarly, human toxicity impacts, largely driven by chromium and lead emissions from cement production, can be mitigated by using SCMs that require less energy-intensive processing [56,57].

While the global warming potential (GWP) receives significant focus, these results underscore the importance of other indicators, such as acidification and ecotoxicity, which also exhibit substantial increases as concrete strength rises. (As can be seen in Table 2, the freshwater aquatic ecotoxicity impact increases from 3.87 × 10 to 3.95 × 10 kg 1.4-DB eq and the terrestrial ecotoxicity impact shifts from 6.09 $\times {10}^{-1}$ to 6.22 $\times {10}^{-1}$ kg 1.4-DB eq for the same range of concrete strength). The use of SCMs such as silica fume and slag can effectively address these impacts. For instance, silica fume is particularly effective in reducing acidification potential by decreasing ${\mathrm{S}\mathrm{O}}_{\mathrm{x}}$ emissions through its pozzolanic reaction [58]. Blast-furnace slag, on the other hand, demonstrates strong performance in mitigating freshwater aquatic ecotoxicity and terrestrial ecotoxicity by lowering heavy metal leaching during its life cycle [59].

This indicates that adjusting the amount of cement by utilising supplement cementitious materials such as fly ash, blast-furnace slag, and silica fume can help minimise the environmental impact of concrete production. Furthermore, SCMs not only reduce GWP but also provide broader benefits across multiple environmental categories, including photochemical oxidation and ozone layer depletion. Fly ash, despite its effectiveness in reducing GWP, contributes to ozone depletion due to nitrogen oxides (${\mathrm{N}\mathrm{O}}_{\mathrm{x}}$) released during its collection and processing. Mitigation strategies such as localised sourcing and advanced processing technologies can help address these drawbacks [60].

As per the calculation program employed in this study’s model, higher concrete strength corresponds to reduced volumes of coarse and fine aggregate, alongside an increased amount of cement incorporated in the batch. This signifies a diminished environmental footprint stemming from aspects associated with the aggregate utilised in concrete. However, the heightened volume of cement amplifies the environmental impact [61].

4.2. Environmental Impacts by SCMs Utilisation

The median values of the estimated environmental impacts for the 49 concrete mixtures, including contemporary concrete and SCMs-utilised concrete (with 30% and 40% of fly ash, blast-furnace slag, and silica fume), were categorised into three groups: (1) Climate change impacts (Global warming—GWP100a and Ozone layer depletion—ODP), (2) Ecotoxicity and human impacts (Human toxicity, Freshwater aquatic ecotoxicity, Marine aquatic ecotoxicity, Terrestrial ecotoxicity), and (3) Other environmental effects (Photochemical oxidation, Acidification, and Eutrophication) are presented in Figure 3, Figure 4 and Figure 5. The various proportions of SCMs utilised in concrete products, namely with the suffixes 30F, 30S, 30Si, 40F, 40S, and 40Si, correspond to the specified concrete strengths in this series. The result of the GWP factor within the 100-year time span demonstrated a decrease in impact when substituting Supplementary Cementitious Materials (SCMs) for cement in 1 m³ of concrete (see Figure 3).

a.

Climate change impacts

The outcomes indicate that when utilising fly ash, the impact is lower than the impact from cement for all the assessed environmental impacts except for ozone layer depletion. Among SCM mixes, 40% slag substitution consistently shows the lowest ODP (Ozone Depletion Potential) values, such as 1.47 $\times {10}^{-6}$ kg CFC-11 eq at 20 MPa, while ordinary concrete has slightly higher ODP values across all strength levels (e.g., 1.71 $\times {10}^{-6}$ kg CFC-11 eq at 20 MPa). In contrast, fly ash mixes, particularly at 30%, exhibit the highest ODP impacts, reaching 5.52 $\times {10}^{-6}$ kg CFC-11 eq at 20 MPa. The analysis results demonstrate that the application of fly ash, while diminished in other categories of environmental impact, significantly contributes to ozone layer depletion, surpassing the impacts of slag, silica fume, and even cement. This finding aligns with the results from various recent studies that have examined the detrimental impacts of fly ash on stratospheric ozone depletion [62].

Although the cost of silica fume does not provide any advantage in comparison with cement, fly ash, and slag, it is worth considering that it has the highest compressive strength when used as a supplementary cementitious material, and it has the lowest environmental impact assessment index among other options. Therefore, it presents itself as a feasible possibility prospect ahead [63,64]. Research indicates that silica fume significantly reduces GWP and acidification impacts due to its high reactivity and reduced demand for clinker production [55]. However, its higher cost, attributed to energy-intensive manufacturing, limits its widespread adoption in cost-sensitive projects [57].

When it becomes necessary to balance cost, environmental impact, and concrete strength criteria, blast furnace slag arises as a viable cement replacement material capable of satisfying these demands. Figure 4 demonstrates that the environmental effect indicators of concrete containing 30% and 40% blast furnace slag are quite similar to those of concrete containing silica fume at equivalent rates. Blast furnace slag has a notable advantage in terms of cost-effectiveness compared to silica fume and fly ash. Its production involves utilising by-products from the steel industry, which reduces the overall environmental impact and cost. BFS is particularly effective in reducing terrestrial ecotoxicity and abiotic depletion, making it a suitable option for projects aiming to minimise resource depletion [65]. The cost of this material is also highly economical, making its application quite practical and aligned with economic and structural considerations. On the other hand, fly ash, while offering moderate cost benefits and effective reduction in GWP, exhibits a higher impact on ozone layer depletion due to the emissions generated during its collection and processing. To mitigate this, sourcing fly ash locally and integrating advanced processing technologies can reduce its environmental footprint while maintaining its workability and durability benefits in concrete applications [66].

Concrete strength levels (20 MPa to 100 MPa) show distinct trends in environmental impacts across all categories, which are largely influenced by the type and proportion of additional materials used. In general, as the compressive strength of concrete increases, so does the environmental impact. This is mainly due to the higher cement content required for higher-strength concrete, which results in increased emissions and resource depletion. Conventional concrete shows the highest environmental burden across all strength categories, suggesting that traditional cement mixtures contribute significantly to global warming, abiotic degradation, and toxicity categories.

Replacing cement with materials such as fly ash, slag, and silica fume is effective in reducing these impacts, with higher substitution rates (40% vs. 30%) performing better across most impact categories. For example, in terms of GWP, replacing 40% fly ash with 100 MPa concrete achieves a significantly lower carbon footprint than conventional concrete of the same strength. This trend remains consistent across metrics of abiotic degradation, fossil fuel consumption, and toxicity. Similarly, substituting slag and silica fume shows significant reductions in impact, especially at higher substitution levels. However, fly ash, despite its effectiveness in lowering GWP and enhancing durability, is associated with a notable impact on ozone layer depletion. This arises from the release of nitrogen oxides (${\mathrm{N}\mathrm{O}}_x$) and sulfur oxides (${\mathrm{S}\mathrm{O}}_x$) during its production and transportation processes, which are precursors to ozone-depleting substances [62,67]. To mitigate these impacts, regional sourcing of fly ash can significantly reduce transportation-related emissions, while advancements in processing technologies can minimise the release of harmful compounds [68].

At all strength levels, lower strength concretes (20 MPa and 35 MPa) have a smaller environmental impact than higher strength mixes (e.g., 80 MPa and 100 MPa). However, the environmental benefits of alternative materials are more pronounced at higher strengths, where reducing cement content has a greater absolute impact. For example, a 40% fly ash blend for 100 MPa concrete had significantly lower GWP and abiotic degradation than the corresponding 30% blend, demonstrating the cumulative benefits of using alternative materials in high-performance concrete.

However, the feasibility of adopting these substitution levels depends on practical and economic considerations. Research highlights that a 40% SCM replacement level may lead to challenges such as extended curing times and reduced early-age strength, particularly in high-strength applications [69]. These factors can affect project timelines and increase costs if modifications to construction schedules are required. Economic studies emphasise the importance of regional availability of SCMs such as fly ash and slag, as transportation and logistics significantly impact their cost-effectiveness [70]. Furthermore, incorporating SCMs such as silica fume and slag not only improves sustainability but also significantly affects mechanical properties and durability. Silica fume enhances compressive strength through its pozzolanic reaction, resulting in denser microstructures and higher resistance to chloride penetration, which is crucial for durability in aggressive environments [71]. Slag also contributes to long-term strength development by refining the pore structure and reducing permeability, although it may delay early-age strength due to its slower hydration process [72]. Additionally, the incorporation of fly ash improves workability and enhances long-term durability by filling pores and reducing the penetration of harmful ions [73]. These enhancements underscore the broader applicability of SCMs in developing high-strength and durable concrete.

b.

Ecotoxicity and human impacts

Slag appears to be particularly effective in reducing terrestrial ecotoxicity and abiotic depletion of non-renewable resources, while silica fume contributes significantly to improvements in acidification and eutrophication. Additionally, blending fly ash with slag or silica fume has been found to dilute the environmental drawbacks associated with each individual SCM. For instance, while fly ash may impact ozone depletion, its combination with slag can offset this trade-off by reducing overall emissions during the production phase. This blending approach enhances not only environmental performance but also mechanical properties, creating a more balanced and sustainable alternative for high-strength concrete applications [74,75].

As can be seen in Figure 4, ordinary concrete consistently exhibits the highest environmental impacts across all strength levels in human toxicity (217.46–221.85 kg 1.4-DB eq), freshwater aquatic ecotoxicity (500.34 kg 1.4-DB eq at 100 MPa), marine aquatic ecotoxicity (516,825.22–527,591.08 kg 1.4-DB eq), and terrestrial ecotoxicity (0.4916–0.5008 kg 1.4-DB eq). In contrast, 40% slag substitution achieves the lowest impacts for human toxicity (200.82–204.86 kg 1.4-DB eq) and freshwater aquatic ecotoxicity (480.33 kg 1.4-DB eq at 20 MPa). Slag is also effective in reducing marine aquatic ecotoxicity at lower strengths, though its benefits diminish at higher strengths. For terrestrial ecotoxicity, 40% fly ash substitution proves most effective, with values ranging from 0.2392 to 0.2431 kg 1.4-DB eq.

c.

Other environmental impacts

Ordinary concrete consistently exhibits the highest environmental impacts across all categories. In photochemical oxidation (0.0330–0.0337 kg ${\mathrm{C}}_2{\mathrm{H}}_4$ eq) and acidification (0.7378–0.7526 kg ${\mathrm{S}\mathrm{O}}_2$ eq), it performs poorly at all strength levels. For eutrophication, its values range from 0.5933 to 0.6057 kg ${\mathrm{P}\mathrm{O}}_4$ eq (Figure 5).

In contrast, SCM substitutions significantly reduce impacts. A 40% fly ash substitution demonstrates the lowest photochemical oxidation (0.0244–0.0249 kg ${\mathrm{C}}_2{\mathrm{H}}_4$ eq), reducing impacts by about 25% compared to ordinary concrete. Fly ash also reduces acidification impacts (0.5557–0.5666 kg ${\mathrm{S}\mathrm{O}}_2$ eq) and provides notable reductions in eutrophication. However, 40% slag substitution achieves the lowest impacts in acidification (0.5422–0.5529 kg ${\mathrm{S}\mathrm{O}}_2$ eq) and eutrophication (0.5405–0.5517 kg ${\mathrm{P}\mathrm{O}}_4$ eq), outperforming other SCM mixes.

Silica and lower slag substitutions also reduce impacts but are less effective than fly ash or 40% slag. Overall, 40% SCM substitutions consistently outperform ordinary concrete, with slag showing superior performance in acidification and eutrophication, while fly ash excels in photochemical oxidation-reduction. Ordinary concrete remains the least sustainable choice due to its high impact across all categories.

Overall, while higher-strength concrete inherently poses greater environmental challenges due to increased material demands, the use of additional materials such as fly ash, slag, and silica fume helps to mitigate these impacts. Fly ash showed the most consistent performance across a range of impact categories, while slag outperformed in reducing resource depletion, and silica fume contributed to significant improvements in categories related to acidification and eutrophication. To further balance the environmental trade-offs, life cycle assessments should prioritise quantifying the ozone layer depletion potential of SCMs such as fly ash. Complementary measures, such as improving the efficiency of fly ash capture and storage technologies, can reduce its overall environmental footprint [76]. Moreover, greater emphasis on policy-driven incentives for the development and adoption of cleaner SCM technologies could help minimise these impacts while maintaining the performance advantages of SCMs [77]. These findings highlight the importance of optimising material composition to balance environmental sustainability with structural performance, especially in high-strength concrete applications.

4.3. Environmental Factor of Reusing Concrete Waste Post-Demolition

The ratio of demolished concrete reuse contributes to an emission reduction [78]. However, the current obstacles to the retrieval of reusable residual materials in concrete are the collecting processing of post-demolition products and the demolition processes. Technological advancements can significantly mitigate the environmental impacts that are frequently associated with concrete materials by facilitating the filtration and removal of demolition-related concrete products for the purpose of repurposing them [79]. These recycling practices align closely with the principles of the circular economy, which emphasise minimising waste and promoting resource recovery to extend the life cycle of materials. For example, advanced sorting technologies, such as sensor-based systems, have been shown to improve the quality of recycled concrete aggregates by efficiently removing contaminants such as gypsum and other unwanted materials [80]. These methods not only enhance the reusability of demolition waste but also reduce dependency on virgin materials, contributing to resource efficiency and the environment [81].

The assessment of the impact of reusing construction waste from concrete extracted after the demolition of a building is estimated, as depicted in Figure 6. The disposal rates for calculating the amount of construction waste are, respectively, 40%, 80%, and 100%. The results indicate that the reuse of concrete waste materials significantly reduces the environmental impact. The GWP impact index for concrete with compressive strengths ranging from 20 MPa to 100 MPa, without employing any recycling measures, varies from 268.95 to 274.46 kg${\mathrm{C}\mathrm{O}}_2$-eq. In contrast, this index varies between 239.38 and 244.25 kg${\mathrm{C}\mathrm{O}}_2$-eq when the landfill disposal rate is 80% of the construction demolition mass. The impact index is approximately 183.19 to 186.85 kg${\mathrm{C}\mathrm{O}}_2$-eq at a disposal rate of 40%.

These findings highlight that enhancing the reuse of demolition concrete through efficient waste management practices and advanced technologies can be a pivotal strategy for reducing the carbon footprint of the construction industry. Specifically, the significant drop in the GWP impact index at lower disposal rates demonstrates the environmental potential of reprocessing and incorporating recycled concrete in new construction projects. However, realising this potential requires coordinated efforts to overcome existing barriers, including the lack of standardised practices for sorting and processing post-demolition materials and the technological limitations in separating contaminants from reusable concrete.

4.4. Comparison with Other Technologies

The study demonstrates that carbonation curing is a highly effective method for ${\mathrm{C}\mathrm{O}}_2$ sequestration and improving the strength of concrete production. To enhance the discussion, the findings are compared with other technologies, such as ${\mathrm{C}\mathrm{O}}_2$ capture during cement production, to provide a broader perspective. For instance, accelerated carbonation curing (ACC) has shown a remarkable potential to reduce greenhouse gas emissions through the conversion of ${\mathrm{C}\mathrm{O}}_2$ into stable calcium carbonate (${\mathrm{C}\mathrm{a}\mathrm{C}\mathrm{O}}_3$). Studies indicate that ACC achieves not only sequestration but also a significant improvement in early compressive strength, with increases of up to 30% in some mixes compared to conventional curing techniques. Additionally, ACC promotes microstructural densification, which enhances durability and reduces porosity [82,83]. Other emerging technologies include mineral carbonation of blended cements, such as those incorporating wollastonite or calcium silicate. These materials enable ${\mathrm{C}\mathrm{O}}_2$ uptake rates of up to 20 wt.% under controlled curing conditions, with some blends reaching compressive strengths of over 80 MPa [84,85]. Mineral carbonation is particularly appealing due to its compatibility with both traditional and novel cementitious systems, potentially enabling its application in a broader range of construction scenarios [86]. The integration of cement kiln dust (CKD) as a partial cement replacement material during carbonation curing further enhances ${\mathrm{C}\mathrm{O}}_2$ uptake and environmental performance. CKD-rich mixtures have demonstrated ${\mathrm{C}\mathrm{O}}_2$ sequestration capacities as high as 14 wt.% while maintaining high alkalinity, which is critical for corrosion resistance in reinforced concrete [87].

Carbon dioxide sequestration at the production stage, such as through carbon capture and storage (CCS) technologies in cement kilns, offers the advantage of mitigating emissions at their source. However, CCS technologies often involve higher operational costs and energy demands compared to ACC or mineral carbonation. These factors make ACC a more accessible and cost-effective solution for precast concrete applications [88,89]. A combined approach leveraging ACC, mineral carbonation, and ${\mathrm{C}\mathrm{O}}_2$ capture during cement production could potentially optimise both environmental and economic outcomes, driving the adoption of greener construction practices globally. Future research should explore synergies between these technologies to establish standardised frameworks for ${\mathrm{C}\mathrm{O}}_2$ utilisation in the construction industry.

5. Conclusions

Failure to prioritise sustainable design in housing initiatives can lead to significant ecological consequences driven by the intensification of construction activities. The advancement of construction is closely tied to the expansion of concrete manufacturing, a major source of greenhouse gas emissions. This study developed and applied a computational model to evaluate the environmental impacts of various concrete types commonly used in civil construction projects. The study focused on key environmental indicators such as global warming potential and life cycle impacts, encompassing stages from material extraction to production, transportation, and end-of-life recycling. Regional factors, including differences in material availability, energy grid emissions, and transportation distances, play a critical role in shaping the environmental impact of concrete production. For instance, regions with limited access to SCMs such as fly ash and blast furnace slag may face higher transportation-related emissions and costs, which could diminish the environmental benefits of these materials.

The findings reveal a direct correlation between the compressive strength of concrete and the quantity of cement used. Consequently, high-strength concrete results in greater environmental impacts compared to lower-strength concrete. However, the differences in environmental impacts across various concrete types are not substantial. The study underscores that the adoption of the carbonation curing technique, which involves injecting carbon dioxide into freshly mixed concrete, is a practical and effective strategy for reducing greenhouse gas emissions throughout the life cycle of concrete.

Another promising approach for mitigating greenhouse gas emissions is the incorporation of SCMs such as fly ash, blast-furnace slag, and silica fume, as outlined by Australia’s Green Star criteria. The computational model demonstrates that utilising SCMs at 30% and 40% replacement levels significantly reduces most environmental impact indices. However, the findings also highlight that the use of fly ash has a comparatively greater effect on ozone layer depletion than cement and the other SCMs, emphasising the need for a balanced selection of materials.

Additionally, exploring other innovative materials such as bioconcrete and chemically treated recycled aggregates could broaden the scope of sustainable concrete solutions. Bioconcrete, which incorporates self-healing properties through the use of bacteria and calcium carbonate, reduces the need for frequent maintenance and extends the lifespan of structures, thereby minimising resource depletion. Chemically treated recycled aggregates enhance the performance of recycled concrete, offering a viable alternative to virgin aggregates while promoting circular economy principles. These emerging materials, coupled with established SCMs and curing techniques, present opportunities for future research and practical application, particularly in regions with limited access to traditional raw materials.

The life cycle assessment further emphasises the importance of incorporating recycled construction waste post-demolition. The results indicate that higher recovery and recycling rates significantly mitigate greenhouse gas emissions. This underscores the necessity of adopting material recovery practices as a proactive measure to reduce the environmental impact of concrete across its life cycle.

This study provides comprehensive insights into the environmental consequences of conventional and alternative concrete technologies, offering guidance for designers, engineers, and policymakers. By applying these assessment principles, stakeholders can make informed decisions about material selection, ensuring the reduction of environmental impacts associated with building construction. Future studies should explore optimised blends of SCMs tailored to specific construction contexts, considering factors such as material compatibility, curing conditions, and economic trade-offs to enhance their applicability in sustainable construction practices. Further integration of recycled aggregates into SCM-based concrete could amplify sustainability impacts by promoting circular economy principles in the construction industry.

While the conclusions of this study offer valuable insights, they are specific to the datasets and scenarios modelled, with findings relevant to the Australian context. Variations in supply chains, material sources, or technological implementations may influence the results. Future research should expand on these findings by exploring dynamic modelling approaches and incorporating broader factors such as economic feasibility, social impacts, and regional variations. Sustainable supply chain management in concrete production requires a multifaceted approach that integrates local sourcing of materials, optimised logistics, and the adoption of digital technologies. For instance, sourcing SCMs such as fly ash and slag locally can significantly reduce transportation-related emissions and costs, aligning with regional sustainability goals. Furthermore, dynamic modelling approaches incorporating supply chain variability can help identify bottlenecks and optimise resource allocation across different regions. For example, life cycle cost analyses that consider regional energy prices and material availability could provide actionable insights for decision-makers.

In conclusion, the adoption of SCMs, innovative curing methods, and efficient recycling practices align with the principles of sustainable development and the circular economy. These strategies ensure that environmental impacts are minimised throughout the life cycle of concrete, paving the way for more sustainable construction practices globally. Achieving sustainability indicators simultaneously presents challenges. For instance, silica fume effectively reduces carbon emissions due to its pozzolanic reaction, which reduces clinker demand, yet its high production cost limits its economic feasibility in many projects. Multi-criteria decision-making frameworks, such as Multi-Criteria Decision Analysis (MCDA), can help balance these conflicting indicators by assigning weights to each sustainability goal based on project-specific priorities. Dynamic scenario modelling, incorporating variations in SCM availability and cost, offers a promising pathway to optimise material composition while balancing environmental and economic objectives. These methods ensure that decisions regarding SCM adoption and curing techniques are context-sensitive, addressing both global sustainability objectives and localised constraints. By integrating such approaches, future construction practices can achieve a more balanced alignment of environmental, economic, and social indicators.