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In this investigation, the influence of adding 2 %, 4 %, 7 %, and 10 % sodium gluconate (SG) on the setting time of hybrid alkaline paste, and hardened and microstructure properties of hybrid alkaline mortar mixes were examined, and the results were compared with a control mix that made without addition of sodium gluconate. The hybrid alkaline paste and mortar mixes were prepared using a fixed proportion of OPC/fly ash (25 %/75 %), NaOH solution molarity of 9 M, and sodium silicate to hydroxide ratio of 1.5. The results of this investigation found that the quick setting and abrupt loss of flowability of the control mix were improved by adding sodium gluconate, however, more promising results were observed at 7 % and 10 % sodium gluconate. The delay in polymerization due to lower availability of calcium ions, and adsorption of carboxyl and hydroxyl groups associated with sodium gluconate on the unreacted particles of binding materials and earlier formed products assisted in prolonging the time required for hardening. Further, the compressive strength declined at a higher dosage of sodium gluconate, however, the mortar mixes made with 2 % and 4 % sodium gluconate exhibited higher compressive strength than the control mix. The peak intensity of albite, nepheline, and C–S–H gel decreased at higher dosages of sodium gluconate, which was supported by a weaker microstructure characterized by more pores, micro-cracks, and partially reacted fly ash particles. Furthermore, the lower bridging oxygen content and greater Si–O–Na/ Si–O–T ratio at higher dosage of sodium gluconate confirms the delayed polymerization process. [Display omitted] • Addition of sodium gluconate (SG) assisted in improving setting time and flowability. • Incorporating SG at lower dosage improved compressive strength, while the decline in strength was observed at higher dosage. • The lower bridging oxygen content and higher non bridging-to-bridging oxygen indicate delay in the polymerization at higher SG dosage. [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]

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]