Key Takeaways & Executive Findings
- •• Steam-cured mortar with up to 15% molybdenum tailings powder achieves high early strength, reaching 85% of 28-day moisture-cured strength at 3 days and at least 90% of pure cement mortar at 28 days. • The addition of 15% MTs significantly reduces harmful and more harmful pore proportions by 71.4% and 72.2%, respectively, and decreases most probable pore diameter from 12.7 nm to 10.8 nm. • SEM analysis reveals that steam-cured paste with 15% MTs exhibits denser microstructure and more hydration products, attributed to the pozzolanic and filling effects of MTs. • Molybdenum tailings powder serves as an effective alternative admixture to refine pore structure and enhance durability of steam-cured cementitious materials, promoting sustainable utilization of solid waste.
Abstract
Molybdenum tailings are the solid waste left from ore processing, which damages soil and water resources. To address that, molybdenum tailings (MTs) powder obtained from molybdenum tailings sands was processed as an admixture. Compared with moisture-cured conditions, the influence of MTs on the steam-cured mortar’s mechanical properties, surface and internal pore characteristics, and microscopic morphology was investigated. The results show that steam-cured mortar containing appropriate MTs can still have high early strength. When the content of MTs doesn’t exceed 15%, the mechanical strength of mortar steam-cured for 3 d can reach 85% of that of corresponding mortar moisture-cured for 28 d, and that of mortar steam-cured for 28 d isn’t lower than 90% of that of pure cement mortar. The proportion of harmful pores (HFP) and more harmful pores (MHFP) and most probable pore diameters (MPD) on the mortar surface containing MTs steam-cured for 28 d are significantly decreased. When MTs’ content is 15%, the proportion of HFP and MHFP on the surface of paste is decreased by 71.4% and 72.2%, respectively, with MPS decreasing from 12.7 nm to 10.8 nm. SEM analysis shows that the surfaces of steam-cured paste containing 15% MTs have more hydration products and dense microstructures. The effect of pozzolanic and dense filling of MTs effectively refines the pore structure, reducing the large pore-size pores.
1. Introduction
In the process of development and utilization of mineral resources, a large number of tailings are produced [1−3], which occupy land, cause environmental pollution, and waste resources [4−6]. Therefore, the resource utilization of tailings is imperative. The use of tailings to prepare building materials such as ceramics, cement, and concrete is an important way of utilizing resources [7−9]. Molybdenum tailings are solid wastes produced after molybdenum ore dressing, and the application of molybdenum tailings as aggregate or active admixture in concrete can not only reduce production costs and energy consumption but also effectively solve the problem of tailings accumulation.
Concrete is the most widely used construction material in the world, and the enhancement of concrete properties has always been a focus of research. The pore structure of concrete influences the strength, permeability, and volume change of the hardened cementitious system, which determines its long-term performance, such as durability [10, 11]. The pore properties of concrete are a key indicator for evaluating durability. Steam curing is an important method to improve the early strength of concrete and is widely used in the production of precast concrete components. Steam-cured concrete has the advantages of high early strength and fast mold turnover efficiency. However, while steam curing improves the early strength of concrete, it also leads to the appearance of surface pore coarsening and other phenomena detrimental to the durability of concrete [12, 13].
Studies have shown that traditional admixtures such as fly ash have pozzolanic effects, interfacial effects, and superimposed composite effects, which play an important role in refining the pore structure and microstructure of concrete [14−16]. However, the quality of traditional admixtures such as fly ash is uneven, and the cost is high. Therefore, the search for new admixtures (solid waste) to replace traditional admixtures is essential to reduce the shortage of admixtures and meet the growing demand for building materials. Molybdenum tailing (MT) powder is a powdered material of molybdenum tailings sand that is ball-milled to a certain fineness by certain technical methods. Some researchers studied the effect of MTs on the hydration process and hydration characteristics of cement and found that MTs has better volcanic ash activity and filler effect, and it has the possibility of being used as an active admixture in concrete [17−20]. Some people prepared ultra-high-performance composites (UHPC) with MTs based on the green activation method, and the results showed that MTs can effectively reduce the porosity of UHPC with good mechanical properties and durability [21]. Some researchers used molybdenum tailing sand as filler to prepare mortar, and the results showed that 20% of molybdenum tailing sand can increase the strength of mortar, and 10% of that can reduce the water absorption and porosity of mortar [22]. And other researchers prepared concrete by substituting an equal mass of cement with MTs particles. The results indicated that
Loading authentic research manuscript (Pages 1–5)...
HAN Zhi-yuan, MENG Wei-qi, MA Kun-lin, LONG Guang-cheng, FAN Jia-zhi (2025). Influence of steam curing on the pore characteristics of cementitious materials containing molybdenum tailings powder. Journal of Central South University. https://doi.org/10.1007/s11771-025-6107-z
Research & Educational Purpose Only:The translations, structured abstracts, analytical annotations, and data reports provided by SinoTechIntel are intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoTechIntel claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What is the effect of molybdenum tailings powder on the early strength of steam-cured mortar?
Steam-cured mortar containing up to 15% molybdenum tailings powder can achieve high early strength, reaching 85% of the 28-day moisture-cured strength at 3 days and at least 90% of pure cement mortar at 28 days.
How does molybdenum tailings powder affect the pore structure of steam-cured cementitious materials?
The addition of 15% molybdenum tailings powder significantly reduces the proportion of harmful and more harmful pores by 71.4% and 72.2%, respectively, and decreases the most probable pore diameter from 12.7 nm to 10.8 nm, refining the pore structure.
What are the environmental benefits of using molybdenum tailings powder in concrete?
Using molybdenum tailings powder as an admixture in concrete helps in the resource utilization of solid waste, reducing land occupation, environmental pollution, and resource waste, while also lowering production costs and energy consumption.
What is the mechanism behind the pore refinement by molybdenum tailings powder?
The pozzolanic and dense filling effects of molybdenum tailings powder promote the formation of hydration products and a denser microstructure, which effectively refines the pore structure and reduces large pores.
Is molybdenum tailings powder a suitable replacement for traditional admixtures like fly ash?
Yes, molybdenum tailings powder exhibits good volcanic ash activity and filler effect, making it a viable alternative to traditional admixtures, addressing the uneven quality and high cost of fly ash while meeting the growing demand for building materials.
Related Technical Papers & Translations
Direct Repair of the Crystal Structure and Coating Surface of Spent LiFePO4 Materials Enables Superfast Li-Ion Migration
The rapid accumulation of spent LiFePO4 (LFP) cathodes from retired lithium-ion batteries necessitates the development of effective and environmental-friendly recycling strategies. In this context, direct regeneration has emerged as a promising approach for reclaiming LFP cathode materials, offering a streamlined pathway to restore their electrochemical functionality. We report an integrated regeneration protocol that simultaneously repairs the degraded crystal structure and reconstructs the damaged carbon coating in spent LFP. The regenerated cathode material had superfast lithium-ion diffusion kinetics and a stable cathode–electrolyte interface, giving a remarkable rate capability with specific capacities of 122 mAh g−1 at 5C and 106 mAh g−1 at 10C (1C = 170 mA g−1). It also maintained capacities of 110.7 mAh g−1 (5C) and 84.1 mAh g−1 (10C) after 400 cycles. It could be used in harsh environments and could be stably cycled at subzero temperatures (−10 and −20 °C) and in solid-state electrolyte batteries. Life cycle assessment combined with economic evaluation using the EverBatt model reveals that this direct regeneration approach has high economic and environmental benefits.
Oxide Semiconductor for Advanced Memory Architectures: Atomic Layer Deposition, Key Requirement and Challenges
Oxide semiconductors (OSs), introduced by the Hosono group in the early 2000s, have evolved from display backplane materials to promising candidates for advanced memory and logic devices. The exceptionally low leakage current of OSs and compatibility with three-dimensional (3D) architectures have recently sparked renewed interest in their use in semiconductor applications. This review begins by exploring the unique material properties of OSs, which fundamentally originate from their distinct electronic band structure. Subsequently, we focus on atomic layer deposition (ALD), a core technique for growing excellent OS films, covering both basic and advanced processes compatible with 3D scaling. The basic surface reaction mechanisms—adsorption and reaction—and their roles in film growth are introduced. Furthermore, material design strategies, such as cation selection, crystallinity control, anion doping, and heterostructure engineering, are discussed. We also highlight challenges in memory applications, including contact resistance, hydrogen instability, and lack of p-type materials, and discuss the feasibility of ALD-grown OSs as potential solutions. Lastly, we provide an outlook on the role of ALD-grown OSs in memory technologies. This review bridges material fundamentals and device-level requirements, offering a comprehensive perspective on the potential of ALD-driven OSs for next-generation semiconductor memory devices.
Laser powder bed fusion of biodegradable Zn-4Cu alloy: Processing, microstructure and properties
Zn's natural degradability and biocompatibility make it a promising candidate for implants, however, its mechanical properties remain insufficient for bone applications. In this study, the performance of Zn was enhanced by developing Zn-Cu alloys via laser powder bed fusion (LPBF). Optimal LPBF parameters for forming stable tracks were achieved by adjusting laser power and scanning speed. Under optimized conditions of 100 W and 100 mm/s, high-density (99.58%) Zn-Cu alloys with improved hardness (68.2HV) and yield strength (160 MPa) were achieved. These improvements are attributed to solid solution strengthening, segregation strengthening, and grain refinement. The Zn-Cu alloys also demonstrated favorable degradation behavior, with a rate of 0.16 mm/year. This degradation is primarily driven by micro-galvanic corrosion between the CuZn5 phase and Zn matrix, along with refined grains and increased grain boundary density. This work demonstrates a viable strategy for fabricating Zn-based implants with enhanced structural integrity and mechanical performance via LPBF.