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The increasing concern for decarbonization and sustainability in construction materials is calling for green binders to partially replace cement since its production is responsible for approximately 8% of global anthropogenic greenhouse gas emissions. Supplementary cementitious materials (SCMs), including fly ash, slag, silica fume, etc., can be used as a partial replacement for ordinary Portland cement (OPC) owing to reduced carbon dioxide emissions associated with OPC production. This study aims to investigate the sustainable use of waste oyster shell powder (OSP)-lithium slag (LS)-ground granulated blast furnace slag (GGBFS) ternary SCM system in green concrete. The effect of ternary SCMs to OPC ratio (0%, 10%, 20%, and 30%) on compressive strength and permeability of the green concrete were studied. The reaction products of the concrete containing OSP-LS-GGBFS SCM system were characterized by SEM and thermogravimetric analyses. The results obtained from this study revealed that the compressive strength of concrete mixed with ternary SCMs are improved compared with the reference specimens. The OSP-LS-GGBFS ternary SCMs-based mortars exhibited a lower porosity and permeability compared to the control specimens. However, when the substitution rate was 30%, the two parameters showed a decline. In addition, the samples incorporating ternary SCMs had a more refined pore structure and lower permeability than that of specimens adding OSP alone. This work expands the possibility of valorization of OSP for sustainable construction materials. [ABSTRACT FROM AUTHOR]

In order to control energy consumption and reduce pollution, the use of supplementary cementitious materials (SCMs) instead of cement to produce green cementitious materials can save energy, reduce emissions and achieve sustainable development. This study demonstrates the possibility of developing SCMs with iron tailings (IOTs), fly ash (FA) and ceramic powder (CP) ternary system, as well as the optimization and improvement scheme of gelation activation. The effects of activator dosage, mix ratio and substitution rate on mechanical properties of ternary SCMs system were investigated. The formation and evolution of hydration products were analyzed by differential thermogravimetric analysis (DTA) and scanning electron microscopy (SEM). The results of the study show that there is synergy in the system. The results show that there is synergy in the system and the hydration reaction is sufficient. At the substitution rate of 30%, the doping ratio of IOTs, CP and FA is 1:2:2 and the Ca(OH)2 is 0.6%, the strength reaches 39.9 MPa and the activity index is 91.5%, which can provide a basis for the application and more in-depth study of IOTs multi SCMs. [ABSTRACT FROM AUTHOR]

As cement manufacturing accounts for 8% of global CO2 emissions, there is an urgent need to tackle the environmental impacts of cement production and address the decarbonization of construction materials. Adopting supplementary cementitious materials (SCMs), including fly ash, slag, silica fume, etc., can be used as a partial replacement for ordinary Portland cement (OPC) to reduce CO2 emissions related to the OPC industry, while providing benefits for waste valorization. This study aims to explore the sustainable utilization of a waste oyster shell powder (OSP)–lithium slag (LS)–ground granulated blast furnace slag (GGBFS) ternary SCM system in green concrete. The effect of OSP fineness on compressive strength, hydration products, pore structure, and transport properties in ternary SCM-based mortars was studied using a wide array of experimental techniques, including thermogravimetric analysis (TGA), scanning electron microscopy (SEM) analysis, Mercury intrusion porosimetry (MIP), the water absorption test and the rapid chloride penetration test (RCPT). The results revealed that the concrete with the ternary SCMs showed equivalent compressive strength compared to reference specimens. The water absorption and chloride ion charge of the RCPT in the concrete containing the ternary SCMs decreased by up to 30% and 81.4%, respectively. It was observed that the specimens incorporating the OSP with a mesh size of 3000 exhibited the highest compressive strength and the most refined microstructure. [ABSTRACT FROM AUTHOR]

A considerable amount of carbon dioxide is released during the preparation of traditional Portland cement, which is not in conformity with the sustainable road. Developing supplementary cementitious material (SCMs) and reducing cement consumption are safe ways to solve this problem. Iron tailings (IOTs), a type of mining waste from the beneficiation process of iron ore concentrate, can be used as SCMs in concrete. In order to tackle the problem of low compressive performance of IOTs as SCMs in concrete, this study develops a multi-SCMs system based on IOTs. Mechanical properties and microstructure of samples with different activator contents and ratios were analyzed by compressive strength, differential thermal–thermal gravimetric analysis (DTA-TG), and scanning electron microscopy (SEM). The results show that the compressive strength of the composite gel blocks in different gel systems changed as follows: ternary SCMs system > binary SCMs system > unary SCMs system. The ternary SCMs system (IOTs: Steel slag(SS):Phosphorus slag(PS) = 1:2:2) without activator was added so that it resulted in the highest compressive strength in multi-SCMs system. With the increase in the content of activators, the compressive strength with ternary SCMs system shows a decreasing trend. It is well known from DTA-TG, as well as SEM, that NaOH and Na2SiO3 have an inhibitory effect on the secondary hydration reaction and inhibit the formation of C-S-H gel. [ABSTRACT FROM AUTHOR]

• Both mechanical and mechanochemical activation methods are effective to improve the chemical activity of iron ore tailings. • Less surface binding energy reflects less crystallinity and higher reactivity. • Ternary IOTs-based SCMs resulted in the comressive strength enhancement and pore structure refinement. The increasing concern for decarbonization calls for sustainable construction materials since carbon dioxide emissions from cement industries account for 8% of the total emissions. Incorporating municipal solid waste into concrete as supplementary cementitious materials (SCMs) is one of the fundamental ways to achieve urban sustainability. Iron ore tailings (IOTs), a type of mining waste from the beneficiation process of iron ore concentrates, can be used as SCMs via various activation methods. While activation of IOTs alone has been a topic of intensive research for years, there is a lack of comprehensive study on mechanical-chemical coupling activation of IOT-based ternary SCMs systems (IOT, fly ash, and ground granulated blast furnace slag) considering the utilization of other industrial by-products and waste. This study investigates the effect of grinding time and chemical activators on the properties of IOT-based ternary SCMs. XRD, XPS, DTA-TG, compression tests, Mercury intrusion porosimetry, and SEM were employed to investigate the crystal structure and crystallinity of IOTs, surface energy, mechanical properties, pore structure, and morphology of the hydration products of the ternary system. The results obtained from this study revealed that an increase in grinding time and chemical activators improved the activity index of IOTs-based ternary SCMs. In addition, Na 2 SiO 3 contributed the most to the activity index among the three types of activators. This work has expanded the possibility of utilizing IOT-based ternary SCMs via proper activation methods for sustainable construction. [ABSTRACT FROM AUTHOR]

Limestone Calcined Clay Cement (LC3) plays a pivotal role in the transition of cement industry toward lower carbon emissions. However, the reliance on limited, non-renewable limestone and expensive, high-grade kaolinite presents notable challenges for LC3, requiring a balance between using lower-quality materials and maintaining high performance. To address this challenge, this study introduced an innovative LC3 mix by incorporating shell powder and self-ignition coal gangue as substitutes for traditional ingredients. The study found that shell powder significantly increased the early-age compressive strength of LC3 at 3 days, raising it to 20.4 MPa, although it restricted the space for further hydration product development. In contrast, introducing self-ignition coal gangue fine-tuned the hydration process, resulting in enhanced compressive strengths of 34.3 MPa and 45.2 MPa at 7 and 28 days, respectively. Additionally, Backscattered Electron (BSE) analysis revealed notable microstructural heterogeneity and introduced a new image processing-based method for evaluating microstructure, emphasizing the importance of adjusting phase compositions around inert particles and reducing inter-particle overlap to optimize LC3 performance. • Novel LC3 formulation leverages solid wastes for improved strength and sustainability. • Shell powder and self-ignition coal gangue identified as effective substitutes in LC3 matrix. • Potential for self-ignition coal gangue in optimizing LC3 carbon footprint. • New directions for enhancing LC3 using controllable particle metrics suggested. [ABSTRACT FROM AUTHOR]