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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]

• 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]

• The activity index of solid waste based composites is higher than 95%. • Solid waste based composites can replace 40% cement in concrete. • The total amount of solid wastes in concrete is up to 83%. Waste rock is stripped from open pit iron mines, which is often used to prepare aggregate in concrete because of its stable performance. However, with the continuous improvement of aggregate performance, a vast amount of stone powder produced in the process of aggregate preparation causes secondary solid waste pollution. In this paper, the feasibility of preparing supplementary cementitious materials (SCMs) by using solid waste based composites was investigated. The results show that the 28-d activity index of iron ore waste powder (IOWP) based admixture is higher than 95%, and when it is used to replace cement in concrete, the admixture can reach 40% and the performance of concrete is stable. When iron ore waste completely replaces aggregates and IOWP based admixture replaces part of cement for concrete, the solid waste content of solid waste aggregate concrete (SWAC) is up to 83% compared to natural aggregate concrete (NAC). This study provides a new idea for high value, high efficiency and scale development of solid wastes. [ABSTRACT FROM AUTHOR]