Effect of TIPA on mechanical properties and hydration properties of cement-lithium slag system

Experimental Study Based on Box-Behnken Design and Response Surface Methodology for Optimization Proportioning of Activated Lithium Slag Composite Cement-Based Cementitious Materials

Cement-based cementitious materials occupy a central position in the construction industry, but the problem of high carbon dioxide(CO2) emissions from cement production has attracted global attention. To meet this challenge, finding low-carbon alternative materials has become a top priority in the research of new building materials. At the same time, the problem of large amounts of lithium slag piling up needs to be solved, and resource utilization has become its potential way out. In this study, the volcanic ash activity of lithium slag was activated by composite activation means of high-temperature calcination and sodium silicate, and it was used as an alternative mix to cement. The Box-Behnken design and response surface method (BBD-RSM) was utilized to optimize the ratio of activated lithium slag composite cement-based cementitious materials, and high-performance new solid waste cementitious materials were prepared. The results show that activated lithium slag composite cementitious materials activated lithium slag exhibit excellent performance when activated lithium slag mass fraction is 7.3%, the sodium silicate dosage is 8.8%, and water-solid ratio is 0.6:1. The composite cementitious material under this ratio shows excellent performance, with fluidity 235.69 mm, gelation time 73.54 s, water evolution rate 1.123%, 3d and 28d compressive strengths, respectively, are 11.54 MPa and 22.9 MPa. Compared with ordinary Portland-cement-based cementing materials, the uniaxial compressive strength, modulus of elasticity, and tensile strength at break of activated lithium slag cementitious material solidified body were increased by 34.33%, 36.43%, and 34.98%, and the compressive deformation and tensile deformation were enhanced by 37.78% and 40%. This study not only provides a theoretical basis and experimental foundation for the preparation of new solid waste cementitious materials, but also provides a new solution for the reinforcement of crushed rock bodies in engineering practice, which is of great significance for promoting the low-carbon development of the construction industry.

High-value utilization of modified magnesium slag solid waste and its application as a low-carbon cement admixture

A large amount of magnesium slag solid waste, insufficient comprehensive disposal capacity, high disposal costs, and uncertain environmental stability hinder the low-carbon, green, and sustainable development of magnesium and magnesium alloy smelting. Therefore, this study proposed a high-quality, large-scale, and industrialized disposal method for modified magnesium slag (MMS). Through relevant experimental tests and microscopic characterization methods (physical and chemical performance, hydration heat, resistivity, and microstructure tests), the physical and chemical properties, curing mechanism, and social benefits of MMS low-grade magnesium slag were investigated. The physical and chemical properties, curing mechanism, and social benefits of modified magnesium slag low-carbon Portland cement (MMSPC) produced by MMS as a cement admixture were elucidated. The results showed that (1) the physical and chemical properties of MMSPC met the requirements of the GB 175-2007 "General Portland Cement" standard. (2) A significant difference was observed in the early hydration heat release of fresh MMSPC slurry, confirming a hydration composite effect between MMS and clinker, which was also the key reaction mechanism of MMS replacing clinker to produce MMSPC. (3) The resistivity of MMSPC increased, decreased, and then increased with time, which was mainly controlled by the settling of the aggregate, the dissolution of the binder, and the hydration reaction of the system. However, the variation in resistivity with time and value was influenced by the mixing ratio of the system. (4) MMSPC could also offer certain environmental and economic benefits. Carbon emissions per ton of cement produced were reduced by 7.95%, and the total cost per ton of cement produced was reduced by more than 10%. This study provided a theoretical basis for the high-value disposal of MMS and the reduction of carbon emissions in the cement industry.

A Review on Cementitious and Geopolymer Composites with Lithium Slag Incorporation

This study critically reviews lithium slag (LS) as a supplementary cementitious material (SCM), thereby examining its physiochemical characteristics, mechanical properties, and durability within cementitious and geopolymer composites. The review reveals that LS's particle size distribution is comparable to fly ash (FA) and ground granulated blast furnace slag (GGBS), which suggests it can enhance densification and nucleation in concrete. The mechanical treatment of LS promotes early hydration by increasing the solubility of aluminum, lithium, and silicon. LS's compositional similarity to FA endows it with low-calcium, high-reactivity properties that are suitable for cementitious and geopolymeric applications. Increasing the LS content reduces setting times and flowability while initially enhancing mechanical properties, albeit with diminishing returns beyond a 30% threshold. LS significantly improves chloride ion resistance and impacts drying shrinkage variably. This study categorizes LS's role in concrete as a filler, pozzolan, and nucleation agent, thereby contributing to the material's overall reduced porosity and increased durability. Economically, LS's cost is substantially lower than FA's; meanwhile, its environmental footprint is comparable to GGBS, thereby making it a sustainable and cost-effective alternative. Notwithstanding, there is a necessity for further research on LS's fine-tuning through grinding, its tensile properties, its performance under environmental duress, and its pozzolanic reactivity to maximize its utility in concrete technologies. This study comprehensively discusses the current strengths and weaknesses of LS in the field of building materials, thereby offering fresh perspectives and methodologies to enhance its performance, improve its application efficiency, and broaden its scope. These efforts are driving the sustainable and green development of LS in waste utilization and advanced concrete technology.

High performance C-A-S-H seeds from fly ash-carbide slag for activating lithium slag towards a low carbon binder

In this work, one-step synthesis of high-performance C-A-S-H (calcium alumina silicate hydrate) seeds from low-calcium fly ash (FA) and carbide slag (CS) by 7 days of mechanochemical mixing was proposed and used to activate lithium slag (LS) cement. The results showed that the seeding effect of C-A-S-H seeds was increased with the increasing Ca/Si (i.e. from 1.0 to 1.5), i.e. the mortar compressive strength of 1 day and 28 days were increased by 67% and 29% with the addition of 1.0% C-A-S-H nano-seeds at Ca/Si = 1.5 in the presence of polycarboxylate superplasticizer (PCE), respectively. Moreover, the chloride resistance of lithium slag cement was improved significantly, i.e. the electric flux was decreased by more than 30% than that of plain lithium slag cement mortar. The performance difference of various C-A-S-H seeds is mainly attributed to their high proportion and polymerization degree, more stretch and three-dimensional foil-like morphology at high Ca/Si. This study provides guidance for obtaining low-cost and high-performance C-A-S-H seeds from wastes and the highly efficient utilization of LS as supplementary cementitious materials (SCMs) in the future.