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The aim of this study is to utilize the bulk proportion of waste concrete powder (WCP) as cementitious material in the fabrication of binder, and to investigate the impact of silica fume on the reactivity and hydration characteristics of thermomechanical activated WCP. A 29 Silicon Nuclear Magnetic Resonance (NMR) analysis confirmed the presence of reactive silica in the activated WCP. Various blends were prepared with a 50%–80% substitution of type CEM I 52.5 N cement. The combination of activated WCP and silica fume improved the reactivity of the binder blend and achieved a compressive strength comparable to cement. Mineralogical analysis revealed the development of secondary C–S–H gels in mixtures containing silica fumes and activated WCP, which is the result of a secondary hydration reaction between portlandite and reactive silica. The use of life cycle analysis software for the replacement of 60 wt % of cement with activated WCP was found to reduce carbon dioxide emissions by 80.42% due to the use of less cement, an environmentally friendly WCP activation process, even when considering the addition of 10% silica fume. This innovative approach not only enhances WCP reactivity and mechanical strength but also significantly contributes to the reduction of carbon emissions. By elucidating the formation mechanisms and environmental benefits, this study paves the way for a more eco-conscious and efficient construction methodology, promoting the vision of a greener future.

In the market for next‐generation energy storage, lithium‐sulfur (Li−S) technology is one of the most promising candidates due to its high theoretical specific energy and cost‐efficient ubiquitous active materials. In this study, this cell system was combined with a cost‐efficient sustainable solvent‐free electrode dry‐coating process (DRYtraec®). So far, this process has been only feasible with polytetrafluoroethylene (PTFE)‐based binders. To increase the sustainability of electrode processing and to decrease the undesired fluorine content of Li−S batteries, a renewable, biodegradable, and fluorine‐free polypeptide was employed as a binder for solvent‐free electrode manufacturing. The yielded sulfur/carbon dry‐film cathodes were electrochemically evaluated under lean electrolyte conditions at coin and pouch cell level, using the state‐of‐the‐art 1,2‐dimethoxyethane/1,3‐dioxolane electrolyte (DME/DOL) as well as the sparingly polysulfide‐solvating electrolytes hexylmethylether (HME)/DOL and tetramethylene sulfone/1,1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetrafluoropropyl ether (TMS/TTE). These results demonstrated that the PTFE binder can be replaced by the biodegradable sericin as the cycle stability and performance of the cathodes was retained. [ABSTRACT FROM AUTHOR]

An environmentally friendly hydrogel based on gelatin has been investigated as a gel polymer electrolyte in a symmetric carbon-based supercapacitor. To guarantee the complete sustainability of the devices, biomaterials from renewable resources (such as chitosan, casein and carboxymethyl cellulose) and activated carbon (from coconut shells) have been used as a binder and filler within the electrode, respectively. The electrochemical properties of the devices have been compared by using cyclic voltammetry, galvanostatic charge/discharge curves and impedance spectroscopy. Compared to the liquid electrolyte, the hydrogel supercapacitors show similar energy performance with an enhancement of stability up to 12,000 cycles (e.g., chitosan as a binder). The most performant device can deliver ca. 5.2 Wh/kg of energy at a high power density of 1256 W/kg. A correlation between the electrochemical performances and charge storage mechanisms (involving faradaic and non-faradaic processes) at the interface electrode/hydrogel has been discussed. [ABSTRACT FROM AUTHOR]

Stabilization of clay using lime or cement is conventionally accepted practice. Although it is effective, they impose several implications on the environment. Hence, it is high time that an alternate sustainable binder needs to be investigated. Eggshell, a waste from food industry, is an alternate source for calcite and can be considered to produce eggshell lime (EL). Also, rice husk ash (RHA), an agricultural waste product, is a silica rich source which is a pozzolanic material. In the current study, the efficiency of both the materials in stabilizing the soft soil is investigated and the results suggests that the plasticity and the strength characteristics of soft clay can be significantly improved by the addition of EL. After adding optimum concentration of 3 % EL, the liquid limit decreased from 74 % to 53 %, plastic limit increased from 27 % to 46 % and shrinkage limit increased from 8 % to 44 %. On increasing the EL content, the swelling got reduced from 88 % of virgin clay to 17 % in case of 3 % EL and finally to zero with 5 % of EL. Also, the addition of combination of EL and RHA to the soft clay has improved the strength characteristics significantly. As the curing days increased, slight variation was only seen in the plasticity characteristics which may be due to rapidity of cation exchange. But strength characteristics increased suggesting the occurrence of pozzolanic reactions and formation of gel. The 28th day strength of the clay treated with 3 % EL increased to as high as 757 kPa. The strength characteristics showed that as we increase the percentages of EL and RHA combination, the strength would increase tremendously much better than the treatment with eggshell lime alone. This is because of the supply of CaO and SiO 2 sources. For 5 % of EL and 15 % of RHA, the 1 day curing strength was near to 500 kPa. With less concentration of eggshell lime and RHA, the treated soil was appearing to be more porous in SEM while when the binder concentration was increased, the pores were filled and presence of C-S-H gel was also detected. XRD test results also showed the presence of C-S-H gel. • Innovative application of eggshell lime as an environmentally friendly alternative to traditional lime. • Innovative application of eggshell lime with RHA as a sustainable alternative replacing cement for soil stabilization. • Geotechnical, microstructural and mineralogical characterization of clay modified with eggshell lime and RHA. • Valorization of waste materials such as Eggshells and RHA. [ABSTRACT FROM AUTHOR]

An environmentally friendly hydrogel based on gelatin has been investigated as a gel polymer electrolyte in a symmetric carbon-based supercapacitor. To guarantee the complete sustainability of the devices, biomaterials from renewable resources (such as chitosan, casein and carboxymethyl cellulose) and activated carbon (from coconut shells) have been used as a binder and filler within the electrode, respectively. The electrochemical properties of the devices have been compared by using cyclic voltammetry, galvanostatic charge/discharge curves and impedance spectroscopy. Compared to the liquid electrolyte, the hydrogel supercapacitors show similar energy performance with an enhancement of stability up to 12,000 cycles (e.g., chitosan as a binder). The most performant device can deliver ca. 5.2 Wh/kg of energy at a high power density of 1256 W/kg. A correlation between the electrochemical performances and charge storage mechanisms (involving faradaic and non-faradaic processes) at the interface electrode/hydrogel has been discussed.

Batteries with good stability and capacity are required to maximize the role of electrical energy storage. The use of a binder is essential for maintaining the structural integrity of the electrodes and optimizing battery performance. Polyvinylidene fluoride (PVDF) has been a commonly used binder; however, its high toxicity and the expensive solvent (N-methyl-2 pyrrolidone) used in its processing pose concerns. In this study, we show that as an alternative to replace PVDF, to some extent, sodium alginate (SA) demonstrates better electrochemical performance owing to its cross-linking with Zn2+ ions, which maintains the stability of the a-MnO 2 electrode in zinc-ion batteries (ZIBs). The strong and reversible chemical bonding of the binder with the active material causes the binder to fill the cracks occurring during electrochemical cycling and self-repairing these cracks upon cycling. After prolonged cycling, the electrode with SA as the binder exhibited better stability than that with PVDF. Furthermore, the rate capability test also suggested that the electrode with the SA binder recovered well after cycling at high current rates. This study highlights the potential of SA as an alternative, self-healing, and environmentally friendly binder for aqueous ZIB applications, thereby opening avenues for maximizing its usage in energy-storage systems. • The water-soluble SA binder was mechanically cross-linked with Zn ions to generate a solid binder that is water-insoluble. After cross-linking, the insoluble network structure generated by Zn-SA can increase the mechanical properties of the electrode material, allowing it to withstand damage during the charge/discharge process. • The α-MnO2 electrode with SA as the binder performed better and more consistently than the α-MnO2 electrode with PVDF as the binder, despite having lower capacities in the beginning cycles. • The rate capability test further revealed that the electrode with SA as the binder remained stable. • Ex-situ studies indicated that the electrode integrity of the α-MnO2 with SA improved during electrochemical cycling. • These findings indicate that SA has the potential to be an environmentally friendly binder for aqueous ZIBs. [ABSTRACT FROM AUTHOR]

• A route is proposed to up recycling rates of construction and demolition wastes C&DW. • Pulverized hardened concrete (PHC) from C&DW is used as precursor in novel cements. • PHC is chemically active towards commercial sodium silicate, reaching 16.05 MPa. • Cements of PHC, portland cement and sodium silicate reached 45 and 50 MPa. • The new cements have low CO 2 emissions, energy demand and cost than portland cement. Construction and demolition wastes amount to 10,000 Mt/year worldwide, a large fraction of these is concrete, along with other potentially useful constituents, like bricks, ceramics, glass, etc. This study investigates the potential of harnessing this environmental passive into cementitious precursors in novel one-part alkaline cements, in which pulverized hardened concrete was blended with 0–80 % of Portland cement and activated with 15 % Type G sodium silicate. Paste specimens underwent curing at 20 or 60 °C for 24 h and then completed 28-days at 20 °C under dry and underwater conditions to test the hydraulicity. The pastes cured at 20 °C having 45 and 25 % recycled concrete reached 45 and 50 MPa, respectively; further characterization suggested the formation of cementitious gels like C-S-H and silica gel. An evaluation of the environmental footprint as CO 2 emissions, energy requirements and cost suggest that these novel cements offer a promising and sustainable alternative for the construction industry. [Display omitted] [ABSTRACT FROM AUTHOR]

Featured Application: The use of a residue that is currently disposed of in landfills was considered in this study, to obtain binder materials more sustainable and respectful to the environment. The recycling glass industry is identified as a model to advance towards a circular economy. The recycling glass rate in Europe is around 74%; meanwhile, in Spain it is approximately 70%, as reported elsewhere. However, in Spain, there is a problem with a residue obtained during the glass recycling process. The residue is named CSP (ceramic, stone, and porcelain). The results of this contribution show that is possible to use this residue as the precursor for developing alkali-activated cements (AAC). Due to the small amount of aluminum in CSP, it is desirable to use it as a non-hydraulic binder for specific purposes, such as prefabrication, decoration, insulation walls, or flooring material. Otherwise, for future works, it will be necessary to include aluminum for hydraulic binder development. During the glass selection process by optical sorting equipment, a rejection material called CSP (ceramic, stone, and porcelain) is generated, which is lower than 2 wt % of the glass cullet collected in Catalonia (Spain). Although this process should only separate non-glass impurities from the glass cullet, around 84 wt % of glass is found in the CSP. The CSP characterization reveals that CSP is mainly compound by SiO2, Al2O3, alkali metals, and CaO, which are key components for the alkali-activated cement (AAC) development. Consequently, this study is focused on the potential of CSP as a precursor to synthesize AAC. The concentration of the alkali activator (NaOH: 1 M, 4 M, and 8 M) and the liquid-to-solid (L/S) ratio were tested in the formulation of the AAC. The AAC specimens at 28 days cured were evaluated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FIR), scanning electron microscopy (SEM), apparent density (ρapp), and compressive strength (σs). The results obtained showed that the L/S of 0.5 and 4.0 M for NaOH concentration are the best conditions, due to the mechanical properties (ρapp = 1.75 g·cm−3; σs = 52.8 MPa), cohesion (SEM), and formed phases (XRD and FT-IR). Therefore, CSP can be a precursor for developing new, sustainable binders. [ABSTRACT FROM AUTHOR]

Environmentally friendly energy storage devices have been fabricated by using functional materials obtained from completely renewable resources. Gelatin, chitosan, casein, guar gum and carboxymethyl cellulose have been investigated as sustainable and low-cost binders within the electrode active material of water-processable symmetric carbon-based supercapacitors. Such binders are selected from natural-derived materials and industrial by-products to obtain economic and environmental benefits. The electrochemical properties of the devices based on the different binders are compared by using cyclic voltammetry, galvanostatic charge/discharge curves and impedance spectroscopy. The fabricated supercapacitors exhibit series resistance lower than a few ohms and values of the specific capacitance ranged between 30 F/g and 80 F/g. The most performant device can deliver ca. 3.6 Wh/kg of energy at a high power density of 3925 W/kg. Gelatin, casein and carboxymethyl cellulose-based devices have shown device stability up to 1000 cycles. Detailed analysis on the charge storage mechanisms (e.g., involving faradaic and non-faradaic processes) at the electrode/electrolyte interface reveals a pseudocapacitance behavior within the supercapacitors. A clear correlation between the electrochemical performances (e.g., cycle stability, capacitance retention, series resistance value, coulombic efficiency) ageing phenomena and charge storage mechanisms within the porous carbon-based electrode have been discussed.

During the glass selection process by optical sorting equipment, a rejection material called CSP (ceramic, stone, and porcelain) is generated, which is lower than 2 wt % of the glass cullet collected in Catalonia (Spain). Although this process should only separate non-glass impurities from the glass cullet, around 84 wt % of glass is found in the CSP. The CSP characterization reveals that CSP is mainly compound by SiO2, Al2O3, alkali metals, and CaO, which are key components for the alkali-activated cement (AAC) development. Consequently, this study is focused on the potential of CSP as a precursor to synthesize AAC. The concentration of the alkali activator (NaOH: 1 M, 4 M, and 8 M) and the liquid-to-solid (L/S) ratio were tested in the formulation of the AAC. The AAC specimens at 28 days cured were evaluated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FIR), scanning electron microscopy (SEM), apparent density (ρapp), and compressive strength (σs). The results obtained showed that the L/S of 0.5 and 4.0 M for NaOH concentration are the best conditions, due to the mechanical properties (ρapp = 1.75 g·cm−3; σs = 52.8 MPa), cohesion (SEM), and formed phases (XRD and FT-IR). Therefore, CSP can be a precursor for developing new, sustainable binders.

Agricultural-industrial wastes, like rice-husk ash (RHA) and carbide lime (CL), have great potential applications in such earthworks as the stabilization of slopes and pavement layers and the spread footings and bed of pipelines, particularly in the regions near where the waste is produced. Present research evaluates the potential use of RHA mixed with CL as a binder, improving strength, stiffness and durability properties of a uniform sand. Two different curing temperatures, 23 °C and 40 °C, and curing periods, 7 and 28 days, of compacted sand-RHA-CL blends (distinct dry unit weights and contents of RHA and CL) were evaluated to determine the importance of these changes on the reactions between the materials. The experimental program aims to assess the following parameters: initial shear modulus (G 0), unconfined compressive strength (q u), and accumulated loss of mass (ALM). Studies have been carried out to quantify these parameters as a function of a novel index called porosity/volumetric binder content (η/B iv). The results showed higher values of G 0 and q u , as well as a small rate of ALM with reduction of porosity and with rise of the environment friendly binder content. The latter is achieved either by increasing eith the RHA or the CL content. The curing temperature acts as a catalyser, accelerating the pozzolanic reactions between RHA and CL. Longer curing periods also benefit reactions between materials by enhancing their geotechnical properties. An analysis of variance (ANOVA) was carried and the results showed the dry unit weight, RHA content and curing type are significantly effect the strength results. It was also possible to verify that curing for 28 days at 23 °C and for 7 days at 40 °C are statistically equivalent in terms of strength. The G 0 results after weathering cycles tended to decrease in specimens at a 40 °C curing temperature and increase in specimens at a 23 °C curing temperature. [ABSTRACT FROM AUTHOR]

Conventional concrete production that uses ordinary Portland cement (OPC) as a binder seems unsustainable due to its high energy consumption, natural resource exhaustion and huge carbon dioxide (CO2) emissions. To transform the conventional process of concrete production to a more sustainable process, the replacement of high energy-consumptive PC with new binders such as fly ash and alkali-activated slag (AAS) from available industrial by-products has been recognized as an alternative. This paper investigates the effect of curing conditions and steel fiber inclusion on the compressive and flexural performance of AAS concrete with a specified compressive strength of 40 MPa to evaluate the feasibility of AAS concrete as an alternative to normal concrete for CO2 emission reduction in the concrete industry. Their performances are compared with reference concrete produced using OPC. The eco-efficiency of AAS use for concrete production was also evaluated by binder intensity and CO2 intensity based on the test results and literature data. Test results show that it is possible to produce AAS concrete with compressive and flexural performances comparable to conventional concrete. Wet-curing and steel fiber inclusion improve the mechanical performance of AAS concrete. Also, the utilization of AAS as a sustainable binder can lead to significant CO2 emissions reduction and resources and energy conservation in the concrete industry.

C-S-H seeding was used in limestone calcined clay cement (LC3) to reduce the ordinary Portland cement (OPC, equivalent to clinker factor) while maintaining strength similar to that of neat OPC. The combination of calcined clay with other supplementary cementitious materials (LC3+), including microsilica, slag (GGBFS), and fly ash, was investigated. The impact of anhydrite content and Na 2 SO 4 was studied. The results showed that C-S-H seeding dramatically enhanced strength from hours to 1 year. The OPC content can be <50 wt% in LC3 and LC3+ cement with C-S-H seeding to achieve comparable strength. The combination of calcined clay, GGBFS and portlandite with C-S-H seeding significantly reduced the OPC content to 20 wt%. Replacing part of the calcined clay by fly ash, GGBFS or limestone improved the mortar flow. Correlations of heat release and pore size with strength showed that C-S-H seeding increased strength by not only acceleration but also through microstructural changes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Activation of WCP phases at comparatively lower temperature of 650 °C. • Thermo-mechanical activation of waste concrete powder (WCP) improved the reactivity. • Up to 40% activated WCP can be effectively utilized without degradation of strength. • The presence of cementitious phases in activated WCP were characterized. • WCP based binder resulted in 37.6% less CO2 emission in comparison to OPC. The objective of present study is to utilize and study the reactivity and hydration behaviour of thermo-mechanically activated waste concrete powder (WCP). For activation, the WCP was burned for 2 h at 650 °C, followed by mechanical grinding through ball milling. The reactivity of the activated WCP was improved significantly, as corroborated through the Chapelle test, hydration analysis and compressive strength analysis. Different blends were prepared with 10 to 40 % OPC replacement. Activated WCP was found to be effective in enhancing the reactivity of cement mixtures for all replacement proportions and developed comparable compressive strength in comparison to OPC. At 56 days, the application of activated WCP resulted in the developed of 75.5 % better compressive strength than the application of as received WCP. Mineralogical analysis exhibited the development of more secondary C-S-H gel with the formation of calcite at the later age. Using lifecycle analysis software, the replacement of 40 wt% of OPC with activated WCP was calculated with 37.6 %, 39.8 % and 19.7 % less CO 2 emissions, less mineral resources consumption and less energy consumption, respectively. [ABSTRACT FROM AUTHOR]

The feasibility of making a cleaner cement via elevated-temperature carbonation of steel slag was investigated. Two types of steel slags were examined, a high-lime ladle steel slag (LSS) and a low-lime electric-arc furnace steel slag (ESS). In comparison to ambient-temperature (23 °C) carbonation, the optimized elevated temperature (55 °C) carbonation process improved the compressive strength of LSS and ESS binders by 72% and 48%, reaching a 12-h paste strength of 91.2 MPa and 39.9 MPa respectively. Meanwhile, LSS and ESS recorded 15% and 9% CO 2 uptake under the optimized carbonation scenario. Serving as the commercial benchmark control, ordinary Portland cement (OPC) paste conventionally hydrated for 28-d recorded an average strength of 43 MPa. The mineralogical and microstructural changes in the steel slag binders under the two carbonation curing scenarios (ambient and 55 °C) were examined by quantitative X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis coupled with a mass spectrometer, mercury intrusion porosimetry, nitrogen adsorption and desorption, and scanning electron microscopy. The analyses revealed that the degree of carbonation and the formation of reaction products were enhanced under the elevated temperature curing conditions, leading to a finer pore structure as well as the development of larger and more crystalline calcium carbonate crystals that contributed to the superior strength of the final product. The sustainability assessment including the embodied carbon analysis confirmed that the carbonated steel slag binder is a cleaner alternative to OPC. This study highlights the wide-ranging prospects to incorporate less reactive, and otherwise landfilled, steel slags into construction cement materials. [Display omitted] • Both high- and low-reactive steel slags can be converted into cementing material. • Steel slags can be activated effectively using carbonation curing. • Elevated curing temperature enhances the CO 2 uptake and performance of slag binders. • Activated slag is a cleaner alternative cement than OPC. [ABSTRACT FROM AUTHOR]

Abstract: The alkali activation of one low calcium hard coal fly ash and four high calcium lignite coal fly ashes was studied by means of conduction calorimetry, X-ray diffraction, thermogravimetric analysis and scanning electron microscopy to assess their potential for mortar and concrete production. The ashes were activated by different additions of sodium silicate with a molar SiO2/Na2O ratio of 1.0. Besides the chemical analysis of the hydrated samples, strength tests have been carried out on mortars, applying different curing regimes. The results indicate that a high content of vitreous phase and low calcium content are important factors determining the reactivity and performance of fly ashes in alkali activated systems. In the high calcium fly ashes, less alkali aluminate silicate hydrates and a much more porous microstructure are formed compared to the low calcium fly ash. Consequently, the low calcium fly ash seems to be suited best for the production of building materials. [Copyright &y& Elsevier]

Environmentally friendly energy storage devices have been fabricated by using functional materials obtained from completely renewable resources. Gelatin, chitosan, casein, guar gum and carboxymethyl cellulose have been investigated as sustainable and low-cost binders within the electrode active material of water-processable symmetric carbon-based supercapacitors. Such binders are selected from natural-derived materials and industrial by-products to obtain economic and environmental benefits. The electrochemical properties of the devices based on the different binders are compared by using cyclic voltammetry, galvanostatic charge/discharge curves and impedance spectroscopy. The fabricated supercapacitors exhibit series resistance lower than a few ohms and values of the specific capacitance ranged between 30 F/g and 80 F/g. The most performant device can deliver ca. 3.6 Wh/kg of energy at a high power density of 3925 W/kg. Gelatin, casein and carboxymethyl cellulose-based devices have shown device stability up to 1000 cycles. Detailed analysis on the charge storage mechanisms (e.g., involving faradaic and non-faradaic processes) at the electrode/electrolyte interface reveals a pseudocapacitance behavior within the supercapacitors. A clear correlation between the electrochemical performances (e.g., cycle stability, capacitance retention, series resistance value, coulombic efficiency) ageing phenomena and charge storage mechanisms within the porous carbon-based electrode have been discussed. [ABSTRACT FROM AUTHOR]

The aim of this study is to explore the feasibility of valorization of steelmaking ladle slag into a high-strength cementing material through a carbonation-activation step that uses flue-gas, so that a closed-loop recycling solution can be achieved. Flue-gas (20% CO 2) carbonation was carried out at ambient (23°C) and elevated (55°C) temperatures. After 24 h of flue gas carbonation at 55°C, ladle slag compacts achieved an average compressive strength of 74.7 MPa with a CO 2 uptake equivalent to 12.1 wt.%. In comparison, conducting carbonation at the ambient temperature recorded lower values for strength and CO 2 uptake, and yielded a less refined and more porous microstructure. Nevertheless, carbonated compacts under both ambient and elevated temperatures achieved better strength performances at all testing ages than the hydrated OPC control reference specimens. The CO 2 in flue gas precipitated as calcite in the paste matrix regardless of curing temperature; however, the elevated temperature of 55°C was found to additionally promote the precipitation of aragonite crystals. In an environmental impact assessment model that uses conventionally-cured OPC as the industry-standard baseline with global warming potential (GWP) of 1204.4 kg CO 2 -eq/m3, the alternative use of carbonation-activated ladle slag was found to greatly reduce the overall GWP to a range between 39.2 and 247.5 kg CO 2 -eq/m3, even when taking the increased curing temperature into consideration. This work presents a possible future scenario where high-strength cementing material could be produced by recycling locally sourced slag, stack-captured flue gas, and waste heat energy from steel plants. [Display omitted] [ABSTRACT FROM AUTHOR]

Environmentally friendly energy storage devices have been fabricated by using functional materials obtained from completely renewable resources. Gelatin, chitosan, casein, guar gum and carboxymethyl cellulose have been investigated as sustainable and low-cost binders within the electrode active material of water-processable symmetric carbon-based supercapacitors. Such binders are selected from natural-derived materials and industrial by-products to obtain economic and environmental benefits. The electrochemical properties of the devices based on the different binders are compared by using cyclic voltammetry, galvanostatic charge/discharge curves and impedance spectroscopy. The fabricated supercapacitors exhibit series resistance lower than a few ohms and values of the specific capacitance ranged between 30 F/g and 80 F/g. The most performant device can deliver ca. 3.6 Wh/kg of energy at a high power density of 3925 W/kg. Gelatin, casein and carboxymethyl cellulose-based devices have shown device stability up to 1000 cycles. Detailed analysis on the charge storage mechanisms (e.g., involving faradaic and non-faradaic processes) at the electrode/electrolyte interface reveals a pseudocapacitance behavior within the supercapacitors. A clear correlation between the electrochemical performances (e.g., cycle stability, capacitance retention, series resistance value, coulombic efficiency) ageing phenomena and charge storage mechanisms within the porous carbon-based electrode have been discussed.

• Physico-chemical characterization of LD slag shows presence of cementious phases in non-reactive crystalline form. • Chappelle test and slag activity index test confirms its low reactivity. • Mechano-chemical activation of slag significantly enhances the slag activity index. • Sodium silicate and sodium sulphates increases compressive strength by 12.6% and 2.6% respectively as compared to control specimens. • 30% of OPC can be gainfully replaced with sodium silicate or sodium sulphate activated LD slag for fabrication of cementitious binder. The aim of present paper is to develop a composite cementitious binder by improving reactivity of Linz Donawitz (LD) slag through mechano-chemical activation. The pozzolanic reactivity of LD slag has been significantly improved as corroborated through modified Chapelle test and slag activity index. The mechanical grinding is carried out with ball milling of LD slag for 20 min followed by chemical activation with four different types of chemical activators namely sodium silicate, sodium sulphate, sodium hydroxide and sodium carbonate. The physico-chemical and strength properties were studied to quantify the efficacy of different alkali activators with 70% of ordinary Portland cement and 30% of ball milled LD slag blend. The sodium silicate and sodium sulphate alkali activators were found effective to enhance the reactivity, which led to increased compressive strength of developed cementitious binder paste cubes as compared to control paste cubes. XRD and Rietveld method results also exhibited the development of more calcium silicate hydrates (CSH) in activated binders, which corroborates increased compressive strength. The normalized heat flow and normalized heat were also found better for both these hydrated blend pastes in comparison to the other blends. The SEM analysis observed more hydration products morphology in blend pastes activated with sodium silicate and sodium sulphate. Based on outcome of different analytical techniques, it was observed that ball milling for 20 min and chemical activation with sodium silicate or sodium sulphate can be applied to enhance the reactivity of LD slag to develop a sustainable composite cement. [ABSTRACT FROM AUTHOR]

Conventional concrete production that uses ordinary Portland cement (OPC) as a binder seems unsustainable due to its high energy consumption, natural resource exhaustion and huge carbon dioxide (CO₂) emissions. To transform the conventional process of concrete production to a more sustainable process, the replacement of high energy-consumptive PC with new binders such as fly ash and alkali-activated slag (AAS) from available industrial by-products has been recognized as an alternative. This paper investigates the effect of curing conditions and steel fiber inclusion on the compressive and flexural performance of AAS concrete with a specified compressive strength of 40 MPa to evaluate the feasibility of AAS concrete as an alternative to normal concrete for CO₂ emission reduction in the concrete industry. Their performances are compared with reference concrete produced using OPC. The eco-efficiency of AAS use for concrete production was also evaluated by binder intensity and CO₂ intensity based on the test results and literature data. Test results show that it is possible to produce AAS concrete with compressive and flexural performances comparable to conventional concrete. Wet-curing and steel fiber inclusion improve the mechanical performance of AAS concrete. Also, the utilization of AAS as a sustainable binder can lead to significant CO₂ emissions reduction and resources and energy conservation in the concrete industry.