Weifeng Liu

Basic magnesium sulfate cement (BMSC) exhibits rapid setting, early strength development, high ultimate strength, and good durability, making it a promising construction material for the extreme environments of Mars. Following the principle of in situ resource utilization (ISRU), this study employs the Martian regolith simulant NUAA-1M, developed by Nanjing University of Aeronautics and Astronautics, as both a mineral admixture and aggregate to prepare Martian basic magnesium sulfate cement (M-BMSC) and Martian basic magnesium sulfate cement concrete (M-BMSCC). The effects of NUAA-1M fines on the setting time, compressive strength, hydration heat evolution, hydration products, microstructure, and pore structure of M-BMSC were systematically investigated. Moreover, the fundamental physical and mechanical properties of M-BMSCC incorporating NUAA-1M as an aggregate were evaluated, and an empirical correlation model was established between its compressive strength (f_cu), flexural strength (f_t), and splitting tensile strength (f_sp). Results indicate that with increasing NUAA-1M fines content, the setting time of M-BMSC was prolonged, while its compressive strength initially increased and then decreased. The incorporation of NUAA-1M fines modified the hydration process and phase assemblage of M-BMSC, promoting the formation of magnesium (alumino)silicate hydrate (M-(A)-S-H) gels and refining the pore structure. Hydration monitoring within 24 h confirmed the rapid hydration characteristics of M-BMSC, demonstrating its suitability for Martian conditions. M-BMSCC exhibited excellent early- and high-strength performance, achieving a 28-day compressive strength of 59.2 MPa at a binder-to-aggregate ratio of 2:1, corresponding to a total NUAA-1M content of 84.75% in the mixture. This work provides a novel ISRU-based material strategy for the construction of Martian bases and infrastructure.

The salt lake and saline–alkali soil regions of high plateaus are characterized by widespread Alkali–silica reactive (ASR) aggregates, which severely threaten the durability of constructed infrastructure, including railways, highways, and buildings. The research systematically investigates the uniaxial compressive mechanical behavior and stress–strain constitutive relationship of high-performance concrete (HPC) with ASR mitigation measures (performance grades C40, C45, C50, and C60) after ten years of immersion in a standard alkali solution. A corresponding three-dimensional random aggregate mesoscopic concrete model was developed, and mesomechanical numerical simulations were performed to explore the failure process, failure patterns, and underlying mesoscopic damage mechanisms of the specimens. Results show that While the uniaxial compressive strength and elastic modulus of HPC show an expected increase with the concrete strength grade following long-term alkali exposure, both properties demonstrate a clear decline as the equivalent alkali content rises. Comparing and analyzing the C50 specimens of different admixtures, it was found that the air-entraining agent provided the most effective ASR suppression and obtained the highest uniaxial compressive strength compared with the rust inhibitor. By normalizing the stress–strain curves, the long-term constitutive behavior of HPC under alkali corrosion was summarized. Furthermore, mesoscopic model visualizations indicate that cracks initially appear in the mortar and gradually propagate inward during loading, leading to compressive failure characterized by diagonal cracks. Tracking the mesoscopic damage patterns within the specimens demonstrates that microcracks originate in the mortar and progressively extend through aggregates, revealing the underlying micro-damage mechanism. By studying the SEM-EDS images, it is found that HPC with a specific mix ratio designed in this paper can effectively inhibit the ASR effect, and it still has good corrosion resistance in long-term alkali immersion.

This study investigates the corrosion behavior, mass changes, and relative dynamic elastic modulus variations of PC (Portland cement concrete) and G60 (with 60% slag) under two treatment methods: immersion in 3.5% NaCl solution and composite (3.5% NaCl + 5.7% Na2SO4) solution, as well as dry–wet cycles. Results indicate that under water and NaCl conditions, no significant mass loss or modulus reduction occurred, with only minor surface efflorescence. However, in the composite solution, severe spalling was observed, with mass loss reaching approximately 1.4% and the relative dynamic modulus decreasing to around 90% after 540 days. Dry–wet cycling accelerated the corrosion process compared to immersion, leading to greater mass loss and modulus reduction. The incorporation of slag improved resistance to ionic penetration in both chemical corrosion and salt crystallization, though this effect diminished with prolonged exposure or increased cycling.

In regions characterized by the challenging combination of brine corrosion in the salt lakes and river sand with alkali silica reaction (ASR) activity in areas of the Northwest, high-performance concrete (HPC) formulated with high-volume composite mineral admixtures as ASR suppression measures has been preferred for civil engineering structures in the region. This study investigates the splitting tensile strength, corrosion products, microscopic structure characteristics, and mesoscopic mechanical mechanisms of splitting failure of such HPC under 10-year corrosion from salt lake brine. The relationship between mechanical properties and corrosion damage, as well as the characteristics of internal crack propagation paths and failure mechanisms of HPC under splitting load, are explored. The findings reveal that as the alkali content within HPC rises, corrosion damage intensifies, resulting in a reduction in splitting tensile strength. Moreover, a linear association between mechanical properties and corrosion damage is observed. Microscopic structural analysis and numerical simulation of the splitting failure process of HPC elucidate that while the substantial presence of mineral admixtures effectively suppresses the ASR risk associated with alkali-reactive aggregates in concrete, uneven ASR gel products persist. These discontinuous micro-fine interface cracks induced by the gel products and the cracks induced by the gel products around the selective alkali-active aggregate particles distributed in the local area are the initiation sources of mortar cracks in HPC splitting failure. In terms of the overall failure state observed during the concrete splitting process, mortar cracks manifest two distinct extension paths: along the coarse aggregate interface and directly through the aggregates themselves. Notably, a greater proportion of coarse aggregates are directly penetrated by mortar cracks, as opposed to the number of interface failures bypassing coarse aggregates. More importantly, the above work establishes a theoretical reference in three dimensions: macroscopic, mesoscopic, and microscopic, for studying concrete corrosion damage in complex environments such as salt lake brine corrosion and ASR inhibition.