Nurhan Gürel – CemenTürk Editor-in-Chief
1. Introduction
The cement industry stands at a critical juncture in balancing economic growth with environmental responsibility. As one of the most essential materials for global infrastructure, cement plays a vital role in modern construction. However, its production also significantly contributes to climate change, accounting for approximately 8% of global CO2 emissions. This striking environmental impact has created an urgent need for sustainable alternatives that can significantly reduce carbon emissions while maintaining structural integrity. The core issue lies in the industry’s reliance on traditional Portland cement, which is highly energyintensive and generates large amounts of CO2 emissions. As global regulations tighten and sustainability targets become more ambitious, the sector is increasingly seeking innovative solutions. This article explores various sustainable cement binders that are transforming the construction industry. By analysing their benefits, challenges, and real-world applications, it aims to provide a comprehensive overview of how alternative cement technologies can contribute to a more sustainable and resilient built environment. The transition to greener cement solutions is not merely a choice but a necessary step in combating climate change and aligning infrastructure development with environmental responsibility.
2. Types of Alternative Binders
Although numerous studies have been conducted on alternative binders, the most promising alternatives include geopolymer cements, magnesium-based binders, carbonated binders, calcium sulfoaluminate (CSA) cement, and reactive magnesium cement. These emerging technologies minimize dependence on traditional clinker-based cement by utilizing industrial by-products, waste materials, and advanced chemical processes.
2.1 Geopolymer Cement
Geopolymer cement is an inorganic polymer-based binder created by reacting aluminosilicate precursors with alkaline activators. Unlike traditional cement, which emits CO2 from limestone calcination, geopolymer cement uses industrial by-products, offering significantly lower emissions. Geopolymer cement is composed of key components such as aluminosilicate precursors (fly ash, metakaolin, slag) and alkaline activators (sodium hydroxide, potassium hydroxide, and silicates), with the geopolymerization process forming a three-dimensional polymeric network that provides superior mechanical strength and chemical resistance. Its advantages include lower CO2 emissions, enhanced durability and resistance to chemical attacks, utilization of industrial by-products, and energy efficiency due to the absence of high-temperature kilns.
Figure 1: Geopolymer Binder Production Flowsheet
These properties make geopolymer cement suitable for applications in infrastructure (bridges, roads), marine structures, underground tunnels, fireproof panels, refractory materials, and the retrofitting and rehabilitation of concrete structures.
Despite its advantages, challenges such as lack of standardization, dependence on regional availability of raw materials, and precise curing and mix design requirements remain. However, with continued innovation and industrial adoption, geopolymer cement stands as a promising alternative to traditional Portland cement in the drive toward a more sustainable construction industry.
2.2 Magnesium-Based Cements
Magnesium-based cements (MBCs) utilize magnesium oxide (MgO) as the primary component. Known for their environmental benefits and durability, these binders are gaining traction as sustainable alternatives.
Magnesium-based cements include magnesium oxychloride cement (MOC), known for its high strength and fast-setting properties; magnesium oxysulfate cement (MOS), which offers superior resistance to acid attack; and reactive magnesium oxide cement, which absorbs CO2 during curing to form stable carbonates; their advantages include lower calcination temperatures (600-800°C) that reduce energy consumption, superior resistance to sulfate attack, corrosion, and freeze-thaw cycles, carbon sequestration potential, and enhanced fire resistance and workability, making them suitable for applications in construction materials (panels, flooring), fireproofing and insulation, deep-well cementing, and green building projects, though challenges such as limited material availability, moisture sensitivity in certain formulations, and lack of regulatory standards remain.
Figure 2: Magnesium Based Cement Binder Production Flowsheet
Magnesium-based cements are increasingly gaining importance as a low-carbon alternative for a more sustainable construction industry.
2.3 Carbonated Binders
Carbonated binders utilize CO2 as a key component in their formation, actively sequestering carbon during curing. This innovation turns CO2 emissions into a resource, creating sustainable cementitious materials.
Carbonated binders are composed of reactive materials such as calcium hydroxide, magnesium oxide, slag, and fly ash, undergoing a carbonation process where they are exposed to CO2 under controlled conditions to form carbonates that strengthen the binder; their advantages include carbon-negative potential through CO2 sequestration, enhanced resistance to chemical degradation, utilization of industrial by-products, and faster strength development, making them suitable for applications in buprecast concrete elements (pavers, panels), waste utilization and recycling projects, and carbon capture and utilization (CCU) strategies, though challenges such as CO2 supply infrastructure, material compatibility and performance variability, and economic viability compared to traditional cement remain.
Figure 3: Carbonated binder production flowsheet
With continued advancements and increasing adoption, carbonated binders represent a promising pathway to decarbonizing the construction industry, turning CO2 from a pollutant into a valuable resource.
2.4 Calcium Sulfoaluminate (CSA) Cement
CSA cement offers rapid strength development, reduced shrinkage, and a lower carbon footprint. It hydrates through ye’elimite (C4A3S̅ ) rather than calcium silicates, requiring less energy for production.
Calcium sulfoaluminate (CSA) cement is composed of key raw materials such as bauxite, limestone, and gypsum, and is produced at lower calcination temperatures (~1250°C), reducing energy consumption and emissions; its advantages include up to 40% lower CO2 emissions, faster setting times, enhanced sulfate resistance
Figure 4: Calcium sulfoaluminate (CSA) cement binder production flowsheet
and durability, and reduced shrinkage and cracking, making it suitable for applications in rapid repair and rehabilitation projects, precast concrete manufacturing, marine and wastewater structures, and green construction initiatives, though challenges such as the availability of raw materials like bauxite, higher production costs, and the need for adjusted construction practices remain.
With growing demand for low-carbon and high-performance construction materials, CSA cement is gaining recognition as a sustainable alternative to Portland cement.
2.5 Reactive Magnesia Cement
Reactive Magnesia Cement (RMC) utilizes MgO as its primary component, reacting with CO2 during curing to form stable magnesium carbonates. This unique property makes RMC both durable and sustainable.
Reactive magnesium oxide (MgO) cement is produced by calcining magnesium carbonate at lower temperatures to derive MgO, undergoing a carbonation process where it absorbs atmospheric or industrial CO2 during curing; its advantages include carbon sequestration potential, lower energy demand, resistance to cracking and chemical attacks, and the sustainable integration
Figure 5: Reactive magnesia cement binder production flowsheet
of waste materials, making it suitable for applications in green buildings and infrastructure, carbon capture projects, repair and restoration of concrete structures, and specialty uses in fireproofing and insulation, though challenges such as the limited availability of high-purity MgO, the need for controlled curing environments, and higher initial costs remain.
With the increasing interest in carbon capture and low-carbon construction, reactive magnesium cement presents a viable alternative to traditional cement.
Figure 6: Production rates of various binders over the years
3. Production, Quality, and Performance of Alternative Binders
The cement industry is no longer restricted by the limitations of traditional materials. The rapid growth of alternative binders proves that sustainability and performance can coexist. As production rates continue to rise, the industry’s commitment to innovation, standardization, and the acceptance of new products is crucial to creating a truly green built environment. A closer look at the production rates of geopolymer cement, magnesium-based cement, carbonated binders, calcium sulfoaluminate (CSA) cement, and reactive magnesium cement reveals a dynamic landscape in terms of growth, innovation, and adoption.
The remarkable rise of alternative binders is transforming the production model of the cement industry, promoting a shift from clinker-heavy processes to more circular and regenerative manufacturing practices. As global cement demand continues to grow, meeting this demand while significantly reducing CO2 emissions, energy consumption, and resource depletion presents a major challenge.
The coming decade will define the future of cement, and with the right investments and strategic collaborations, a low-carbon cement industry will transition from a vision to an imminent reality.
Each alternative binder offers a unique balance in terms of compressive strength, setting time, and durability, making them suitable solutions for various construction applications:
• Geopolymer cement boasts a compressive strength of 60 MPa, setting within 90 minutes, and lasting over 80 years, all while achieving an 80% reduction in CO2 emissions compared to Portland cement.
Figure 7: Quality indicators of various alternative cement binders
• Magnesium-based cement, with its 50 MPa strength and 70% lower emissions, is being hailed as a major breakthrough in carbonnegative building materials.
• Carbonated binders, leveraging natural CO2 absorption, provide 85% emissions reduction, a compressive strength of 55 MPa, and 75 years of durability.
• Calcium sulfoaluminate (CSA) cement, with its rapid setting time of just 60 minutes, is revolutionizing precast and high-performance concrete applications while reducing emissions by 60%.
• Reactive magnesia cement, leading the way with a 90% CO2 reduction, proves that negative-emission cement is not just a concept but a reality, though with slightly lower strength at 45 MPa.
With Portland cement historically emitting 800-900 kg of CO2 per ton, alternative binders offer a game-changing shift in reducing the cement industry’s environmental impact:
Figure 8: CO2 Reduction comparison of various binders
• Geopolymer and magnesium-based cements emerge as the most scalable options, combining high durability with substantial emission reductions.
• Carbonated binders take sustainability a step further by actively capturing CO2 during curing, making them an ideal solution for carbon-neutral projects.
• CSA cement, despite its slightly lower CO2 reduction rate, remains a vital solution for projects that require high early strength and rapid setting.
• Reactive magnesia cement, with the highest CO2 reduction potential, is gaining traction in next-generation carbon-negative construction.
4. Economic Factors in Alternative Binder Production
As the cement industry pivots towards sustainability and carbon neutrality, the economic viability of alternative binders is becoming a critical discussion point. The transition from ordinary Portland cement (OPC) to geopolymer cement, magnesium-based cement, carbonated binders, calcium sulfoaluminate (CSA) cement, and reactive magnesia cement is not just about reducing emissions. It is about creating a more cost-efficient and resource-optimized industry. While traditional cement plants require high capital expenditures (CAPEX) and energy-intensive operational expenditures (OPEX), alternative binders offer a compelling economic advantage by leveraging industrial by-products, lower energy consumption, and innovative chemistry.
The initial capital investment (CAPEX) in alternative binder production plants varies, but they often require lower kiln temperatures and less energy-intensive processes, making them more cost-competitive in the long run.
• Traditional Portland Cement Plants: Require CAPEX investments above 100 million USD per plant due to high-temperature clinker kilns, extensive raw material processing, and emissions control technologies.
• Geopolymer Cement Plants: Operate at nearly half the cost, with an estimated CAPEX of 50 million USD per plant, as they eliminate clinker production and use chemical activation of waste materials instead.
• Magnesium-Based Cement: While slightly higher in CAPEX (60 million USD per plant), its long-term economic benefits lie in CO2 absorption capabilities, which can generate revenue from carbon credit markets.
• Carbonated Binders: At 55 million USD per plant, these offer a low-energy alternative, harnessing CO2 from industrial emissions, effectively reducing both environmental impact and operational costs.
• CSA Cement & Reactive Magnesia Cement: While having relatively higher CAPEX values (65M and 58M USD per plant, respectively), these technologies are becoming key players in specialized markets such as rapid-setting and carbon-neutral construction.
The operational expenditures (OPEX) of alternative binders demonstrate significant cost reductions when compared to traditional cement production, which incurs expenses of $50–$70 per ton, driven by energy-intensive clinker grinding and raw material extraction.
• Geopolymer Cement: With an OPEX of $40 per ton, it benefits from using industrial waste materials (fly ash, slag) and eliminating high-temperature kilns, reducing fuel and electricity costs.
• Magnesium-Based Cement: Slightly higher at $45 per ton, but offsets costs with CO2 sequestration incentives and low-energy production processes.
• Carbonated Binders: The most cost-effective at $38 per ton, these binders rely on ambient CO2 curing instead of high-temperature kilns, making them an attractive low-cost solution.
Figure 9: CAPEX and OPEX comparison of various binders
• CSA Cement & Reactive Magnesia Cement: While CSA cement has a higher OPEX of $50 per ton, its fast-setting properties allow for quick construction turnover, reducing labor and time costs. Reactive magnesia cement, at $42 per ton, offsets costs through carbon capture technologies, making it a future-ready investment.
One of the largest cost drivers in cement production is energy consumption, measured in kilowatt-hours per ton (kWh/t).
• Traditional Portland Cement: Consumes over 900 kWh/t, as it requires clinker calcination at 1400-1500°C, significantly increasing fuel and electricity costs.
• Alternative Binders: Demonstrate significant energy savings, ranging between 250-320 kWh/t, cutting production costs by over 50% in some cases. Geopolymer cement, for example, operates at 300 kWh/t, while magnesium-based cement consumes only 250 kWh/t, making them strong competitors in a cost-driven market.
Figure 10: Energy consumption of various alternative binders
With rising prices of limestone, gypsum, and silica, alternative binders offer a cost advantage by utilizing abundant industrial byproducts or alternative minerals:
• Portland Cement: Requires $30–$40 per ton in raw materials, as it depends on high-purity limestone, which is increasingly scarce and expensive.
• Geopolymer & Carbonated Binders: Have some of the lowest raw material costs at $18–$20 per ton, thanks to their reliance on industrial waste streams.
• CSA Cement & Reactive Magnesia Cement: Require specialty materials, pushing costs to $22–$30 per ton, but these costs are justified by their unique performance advantages.
Figure 11: Raw material cost distribution of various binders
5. Conclusion
The cement industry is no longer solely focused on meeting construction demands; it is redefining the concepts of quality and sustainability for the building materials of the future. As alternative binders continue to grow, the potential of high-performance, lowemission cement will transform cities, infrastructure, and industries. Performance and sustainability are not opposing forces but complementary drivers steering the industry toward a net-zero future.
The economics of alternative binders present a compelling case for industry-wide adoption. Compared to traditional cement, these binders offer significant cost savings in operational expenditures (OPEX), energy consumption, and raw material sourcing while reducing CO2 emissions by up to 90%. The low capital investment (CAPEX) required for geopolymer, carbonated, and magnesiumbased cement plants makes them profitable long-term investments, while CSA and reactive magnesium cement provide high-value returns for specialized applications.
As regulatory bodies tighten CO2 emission standards and carbon pricing policies come into effect, cement manufacturers will need to adapt. Alternative binders are not just a sustainable option but an economic necessity for a resilient, profitable, and net-zero cement industry.
However, the widespread adoption of these innovations faces certain challenges. Regulatory barriers, raw material availability, cost competitiveness, and lack of standardization hinder their mainstream acceptance. Nevertheless, ongoing research, policy support, industry collaboration, and investment in new technologies can help overcome these obstacles. Encouragingly, pioneering companies and research institutions continue to develop these materials, paving the way for more sustainable construction practices.
A paradigm shift is needed in the construction sector—one that prioritizes low-carbon alternatives without compromising performance, durability, or economic feasibility. The widespread adoption of sustainable cement binders will enable the industry to contribute significantly to global climate action goals while aligning infrastructure development with environmental responsibility.
Achieving a greener cement industry is undoubtedly challenging, but through innovation, collaboration, and a commitment to sustainability, the construction sector will take a crucial step toward a future that is both resilient and environmentally responsible.
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