With the progressive advancement of Mars exploration, in-situ resource utilization (ISRU) for the construction of Martian infrastructure has become a critical research focus. Basic magnesium sulfate cement (BMSC), which can be synthesized entirely from Martian resources, is a promising material. However, the mechanisms by which Martian regolith influences BMSC performance remain unclear. In this study, Nanjing University of Aeronautics and Astronautics-1 Mars (NUAA-1M) regolith simulant was employed for the first time as a mineral admixture to systematically investigate its pozzolanic effect and reaction mechanisms in BMSC. The results indicate that NUAA-1M, when incorporated into BMSC, functions through both filler and pozzolanic effects. Multi-scale analyses including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS) reveal that, in the amorphous phase of BMSC, 5Mg(OH)(2)MgSO4nH(2)O (51n, n > 7), together with small amounts of poorly crystalline Mg(OH)(2) and 5Mg(OH)(2)MgSO47 H2O (517 phase), can dissociate to release Mg2 + , SO42-, and OH- ions, which subsequently react with Si and Al species in the glassy phase of NUAA-1M to generate amorphous gel products. Complementary solid-state nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) analyses further indicate that these pozzolanic reaction products are predominantly magnesium silicate hydrate (M-S-H-type) hydration products, accompanied by minor amounts of magnesium aluminosilicate hydrate (M-A-S-H-type).

With the extension of building service life and the erosion of various environments, the demand for building reinforcement is increasing. This study aims to investigate the flexural performance of reinforced concrete (RC) beams strengthened with magnesium phosphate cement (MPC) combined with glass fiber-reinforced textile (GFRT). Through experiments and analysis, the study examined the flexural capacity, midspan deflection, crack development, and failure modes of RC beams with different concrete strength grades (including coral aggregate RC beams, basic magnesium sulfate RC beams (BMRCB), and ordinary Portland RC beams) before and after strengthening. The results show that the MPC-GFRT strengthening significantly increased the crack moment of the beams, with enhancements ranging from 125.0 to 200.0

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 (fcu), flexural strength (ft), and splitting tensile strength (fsp). 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.

This study proposes a novel and structured life cycle assessment (LCA) framework for evaluating low-carbon, high-durability concrete, with a specific focus on salt-freeze resistance in cold regions. The framework consists of four components: (1) a durability-normalized carbon emission index combining compressive strength and salt-freeze resistance; (2) a climate-adaptive service life prediction model based on environmental data from six representative global cities; (3) optimized mix designs utilizing ground granulated blast furnace slag (GGBS), air-entraining agents, and polypropylene fibers; and (4) quantitative validation under both laboratory and regional environmental conditions. Results show that the proposed high-performance concrete (e.g., HPC5-P-HSRF-S) achieves over 11.3 times the salt-freeze service life of conventional OPC concrete, while reducing life cycle carbon emissions from 397 kg CO2/m3 to 10.8 kg CO2/m3, representing a 97.3 % reduction. Even across varying climatic zones, the durability-normalized emissions index remains consistent, demonstrating the robustness and practical relevance of the model. These findings highlight the potential of integrating durability into LCA for more accurate, engineering-oriented design of sustainable infrastructure materials.

This research focuses on the development of the Anti-freezing Durability-Oriented Carbon Emission Indicator (CEI) system for assessing concrete's carbon footprint with an emphasis on durability, particularly in freeze-thaw conditions. This novel approach reduces the environmental impact of concrete by integrating durability metrics into carbon emission evaluations. The paper presents experimental findings on mix designs for high-strength, low-carbon concrete, which demonstrate improved freeze-thaw durability. And found out that concrete mixes using sulfate-resistant cement with GGBS outperform those with FA and OPC in terms of low-carbon performance, in the newly developed 19 mixes, concrete mix incorporating air-entraining agents with sulfate-resistant cement and 40% GGBS as a supplementary cementitious material, namely the HPC1-P center dot HSRF-S group, demonstrates a distinct low-carbon advantage across various indicators. Overall, the inclusion of fibers is shown to improve freeze-thaw durability, though with limited impact on compressive strength. The research underlines the importance of optimizing concrete mix designs for both environmental and durability considerations, presenting a significant step towards more sustainable construction practices.

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To study the durability of magnesium oxychloride cement (MOC) in practical applications, samples from 6 to 80 years in different regions of China, including both north and south China, were collected. Phase composition and microstructure of MOC were analyzed, and phase transition patterns and microstructure characteristics of MOC were explored. The results show that, for MOC material, the main hydration product is 5Mg(OH)(2) center dot MgCl2 center dot 8H(2)O (phase 5 center dot 1 center dot 8), and the carbonation products are Mg(OH)(2) center dot MgCl2 center dot 2MgCO(3) center dot 6H(2)O (phase 1 center dot 1 center dot 2 center dot 6) and 4MgCO(3) center dot Mg(OH)(2) center dot 4H(2)O (phase 4 center dot 1 center dot 4). For MOC samples with ages less than 20 years, the content of phase 5 center dot 1 center dot 8 and the total content of carbonized phases (phase 1 center dot 1 center dot 2 center dot 6 and phase 4 center dot 1 center dot 4) increases and decreases in turn. The change of the total content of the carbonized phase is opposite to that of the phase 5 center dot 1 center dot 8 and is affected by phase 5 center dot 1 center dot 8. A calculation formula for the carbonation degree of MOC material system is proposed. The calculation results show that when the age is less than 14 years, the carbonation rate of MOC samples in the dry environment from north China is slow, but obviously increases when the age exceeds 14 years. Carbonation degree of the MOC samples at 6 years in the high humid environment of south China is close to that of the samples at about 20 years in north China. The crystal morphologies of different phases in MOC are varied. There are needle rod-like and flocculent crystals of phase 5 center dot 1 center dot 8, short rod-like crystals of phase 1 center dot 1 center dot 2 center dot 6, flaky crystals of phase 4 center dot 1 center dot 4, and nubbly crystals of MgCO 3 in MOC. Phase 5 center dot 1 center dot 8 ensures the integrity of the glass fiber, while sawdust shows disadvantages on the long-term service of MOC. (c) 2023 American Society of Civil Engineers.

Magnesium oxychloride cement (MOC) is widely used as fireproof materials, decorative materials, and adsorption materials, etc. However, its poor water resistance limits the engineering application as a building material. The existing researches mainly focus on improving the short-term durability and water resistance, but few focus on long-term durability of MOC. In this paper, phosphoric acid-modified MOC samples with an age of 2–16 years from China and the Netherlands were collected. Their phase composition and microstructure characteristics were studied, which is of practical engineering significance for the modification of MOC. The results indicate that MOC modified by phosphoric acid would be decomposed and carbonated, and water in the ambient where MOC exposed to is the main factor. MOC exposed to humid environment presents a loose and porous morphology, but shows dense matrix with drying shrinkage cracks in dry air condition. MOC exposed to the air shows good carbon capture ability. The carbonated wood-MOC shows lower porosity than fresh wood-MOC paste. Carbonation phase on the surface of MOC products is beneficial to the internal structure and stability of MOC matrix. Besides, MOC is an environmentally friendly material. The manufacture of MOC requires less energy compared to ordinary Portland cement and shows good carbon neutralization potential under service life.

Basic magnesium sulfate cement (BMSC) is a kind of air hardening cementitious material with the advantages of high strength, light weight, fire resistance, low alkalinity. However, the durability of the main binding phase (phase 5) of BMSC should be verified. In this work, the flexural strength of BMSC boards with ages between 0.25 years and 11years was investigated. The phase composition and microstructure of BMSC samples, including BMSC boards and the sample of BMSC beam-column joint that hydrates at low temperature were studied. The results reveal that the flexural strength of glass fiber-reinforced BMSC boards is higher than that of ordinary BMSC specimens, and the higher the content of phase 5 is, the greater the flexural strength is. Phase 5 within BMSC boards exposed to the air shows good environment durability, and the change of its content shows little relationship with the service age of BMSC. The phase composition of BMSC samples with long ages still predominantly consists of phase 5, and the microstructure of BMSC remains dense. Besides, the incorporation of air entraining agent can effectively improve the pore distribution of BMSC and generate numerous capillary pores, which may benefit the frost resistance of BMSC. Additionally, even at low temperatures (around 0 C), BMSC concrete can be hardened to achieve the design strength and fly ash can be dissolved in the matrix of BMSC to form new gel phases.

Magnesium oxychloride cement recycled concrete (MOCRC) has the advantages of low carbon emissions and energy savings. To better understand the rebar corrosion problem in MOCRC under a salt lake environment, this paper presents the investigation of rebar corrosion behavior in MOCRC, as well as the difference of protective influence between single and double protective methods. During the investigation, the concrete surface strengthening materials and rebar type selection were selected as protective methods, and an electrochemical test based on linear polarization method and Tafel method was introduced. According to the time-varying characteristics of corrosion current density and mass loss of rebar in different specimens, a time-varying model of corrosion current density of rebar was established. The results show that the B values of corroded hot-rolled plain steel (HS), corroded HS with self-developed coating (CS), uncorroded CS, and uncorroded stainless steel (SS) were 28, 34, 41, and 45 mV, respectively. Also, the rebar type selection has far better protective influence than the concrete surface strengthening materials, and the double protective method was better than the single protective method. Besides, it was noticed that the time-varying characteristic of rebar corrosion in MOCRC conformed to the logarithmic-type time-varying model, which has an upward trend in the earlier stage and exponential-type time-varying model with a downward trend in the later stage. Finally, this study presents a profound investigation for the reinforcement corrosion in low-carbon and energy-saving building MOCRC structures.

Adding mineral admixtures is a green, economic and effective way of improving the properties of magnesium oxysulfate cement (MOSC). Based on MOSC modified with low-calcium fly ash (L-FA), high-calcium fly ash (H-FA) and granulated blast-furnace slag (G-BS), the effects of L-FA, H-FA and G-BS and silica fume (SF) double mixing on the properties of MOSC were studied by characterising the compressive strength, water resistance, hydration heat, hydration products and micropore structure characteristics. The modification mechanism of the mineral admixtures was also investigated. The results showed that L-FA, G-BS and SF double mixing optimised the hydration product composition and the micropore structure of the MOSC, thus improving its compressive strength and water resistance. The hydration reaction rate of MOSC and 5.1.7 phase content in the hydration products was increased by H-FA and SF double mixing, but the micropore structure was not further optimised, which is why the water resistance of MOSC with H-FA and SF was not improved. The research results enrich the basic theory of mineral admixtures for improving the properties of MOSC and provide theoretical guidance for practical applications.

Ethylene glycol (EG) deicer and propylene glycol (PG) deicer were frequently used as the aircraft de-icing fluids in cold region. In this paper, the icing pressure (Ip), icing volume expansion rate (ΔVP), freezing point (T0) and under-cooling (△T) of aircraft deicers with different concentrations were investigated, and the above indicators of aircraft deicers were also compared with that of water and NaCl deicers. The results showed that the icing volume expansion of deicers was the direct cause of icing pressure. During the cooling process, values of Ip and ΔVP firstly increased sharply, then slowly, and finally became stable. The stabilized values of Ip and ΔVP decreased with concentration. The stabilized Ip value of EG deicer was slightly higher than that of 3.5% NaCl deicer and far greater than 3.5% PG deicer. Of all the tested deicers, the stabilized ΔVP value of NaCl deicer was the highest and that value of EG deicer was close to that of PG deicer. The results further confirmed the feasibility of using impulse of icing pressure as the indicator to evaluate the freeze-thaw deterioration to concrete.

为进一步研究冻融过程中醋酸钙镁除冰液对混凝土的冻融破坏机理,本文配置不同质量浓度的醋酸钙镁除冰液,进行其在低温下的结冰压力实验;制备硅酸盐水泥混凝土和抗硫酸盐水泥混凝土,进行其在水冻和醋酸钙镁除冰液盐冻环境下的冻融实验;同时对冻后的混凝土表层物相进行X射线衍射实验,使用扫描电子显微镜实验分析混凝土内部微观结构变化.实验结果表明:水的结冰压力稳定值最高,醋酸钙镁除冰液的Ip值随着除冰液浓度的升高而降低.混凝土在水中和醋酸钙镁除冰液中的冻融损伤主要是由内部的冻融微裂纹和外部剥落引起.20％粉煤灰掺量下,普通硅酸盐水泥混凝土的抗冻性明显优于抗硫酸盐水泥混凝土;醋酸钙镁除冰液对混凝土存在冻融破坏和化学腐蚀破坏作用,但短期的冻融循环过程中醋酸钙镁除冰液对混凝土的破坏现象依旧比水轻.

Magnesium oxysulfate (MOS) cement is a promising low-carbon and high-performance cement. Basic research on the MgO-MgSO4-H2O system is of great significance for further optimizing the properties of MOS cement. In this study, through the qualitative hydrolysis test of the Mg2+(MgSO4)-OH--H2O system and the test and charac-terization of the composition of the hydration products and microstructure of the MgO-MgSO4-H2O system, the relationship between the composition of the hydration products of the MgO-MgSO4-H2O system and the molar ratio of raw materials and the mechanism of chemical additives were investigated. The results show polynuclear complexes [MgP(OH)q(H2O)r]2p-q in the MgO-MgSO4-H2O system. The main group of hydration products of MOS cement without chemical additives, which is the 3.1.8 phase, is formed by the transformation of the unstable 1.1.5 phase through the 5.1.3 phase. However, chemical additives can change the hydration reaction processes of MOS cement through buffering and complexation, which causes the main hydration products of MOS cement to change to the 5.1.7 phase. The 5.1.7 phase is a metastable phase (or stable phase) formed by the transformation of the unstable 1.1.5 phase through the 3.1.8 phase.

Acetate-based deicers are frequently used as airport pavement de-icing fluids in cold regions. In this study, the ice pressure (Ip), icing volume expansion rate (Delta PV), freezing point (T0), and undercooling degree of acetate-based deicers were investigated. The above mentioned indices were also compared with that of water and NaCl deicers. The results showed that the cooling process and ice crystal growing process of acetate-based deicers could be divided into five stages. Additionally, the stabilised values of Ip and Delta PV decreased with the deicer concentration increases. Furthermore, the impulse concept of ice pressure (IPI) was proposed to evaluate the frost damage of concrete caused by deicers. The Ip, Delta PV , and T0 values of calcium magnesium acetate (CMA) deicer with different Ca/Mg mole ratios (i.e. 1/1, 0.91, 7/3, and 3/7) were tested in the ice pressure test. The value of CMA deicer with 3/7 Ca/Mg mole ratio was the lowest. However, the Ip values of CMA deicers with 0.91 Ca/Mg and 1/1 Ca/Mg mole ratios were the highest. Among all the tested acetate-based deicers, CMA deicers had the lowest values of Ip, Delta PV, and IPI. Moreover, the CMA deicer with 3Ca/7Mg mole ratio was recommended for deicing airport pavements to reduce the concrete frost deterioration caused by acetate-based deicers. In this study, we investigated the physical properties of acetate-based deicers, quantitatively analysed the destructive power of deicers in a freeze-thaw test, and studied the cause of freeze-thaw deterioration of concrete. Overall, this study provides a theoretical method for exploring new deicers.

The rapid freeze-thaw test about ordinary Portland cement concrete (PCC) was performed in the deicers of water, 3.5% ethylene glycol, 3.5% NaCl and 3.5% calcium magnesium acetate (CMA). The ice pressure (I-P) of deicer was tested, and the concept of the ice pressure impulse (IPI) was proposed. A crack density model was employed to describe the freeze-thaw damage process of concrete. Results indicated that the freeze-thaw damage of PCC in CMA deicer was the mildest. The I-P value of water was the highest but its IPI value was the lowest. The freeze-thaw microcracks inside concrete was induced by the I-P of deicer restrained in concrete pores. The freeze-thaw crack density decreased with the relative depth of specimen. The value of superficial critical crack density was 0.85 similar to 0.88, when the exterior mortar of concrete began spalling. The value of central critical crack density was 0.32 similar to 0.34, when the interior freeze-thaw failure of concrete occurred.

Icing pressure testing was conducted to investigate the icing pressure (I-p) of chloride-based deicers and discuss the relation between I-p and the freeze-thaw deterioration of concrete induced by chloride deicers. During the icing pressure test, when the solution transformed from the liquid to the solid phase, under cooling occurred, and the heat of the liquid-solid phase transformation was released. The I-p of chloride deicers and water reached a plateau near -30 degrees C. The stable I-p value of water was the highest of that of the chloride solutions followed by that of 3.5% NaCl; the Ip of 3.5% CaCl2 was slightly higher than that of 3.5% MgCl2. The concept of the I-p cumulative effect with time (S) was first proposed to determine the freeze-thaw destruction induced by chloride-based deicers. The durable life of the concrete exposed to chloride-based deicers decreased with the S of the deicers, and the mass loss of the concrete increased with the S of the deicers. (C) 2019 Elsevier Ltd. All rights reserved.

The major aimed at investigating the mechanism of the freeze-thaw damage to high performance concrete (HPC) under ethylene glycol (EG) deicer. In this study, three types of HPC were prepared, as well as the reference concrete (OPCO). Tests were performed to evaluate the ice-formation pressure (I-p), determine the impact of rapid freeze-thaw cycles, study the microstructure, and evaluate the compression strength of the HPC and OPCO. The results yielded suggested that the I-p, and the concentration of the EG solution had a strong linear correlation. The I-p of EG solution decreased with its concentration. The freeze-thaw deterioration of OPCO in 3.5 wt% EG was greater than that of HPC, and the EG did not come into any chemical reaction with concrete hydration product. In this study, HPC blended with 20 wt% fly ash and 0.1% polypropylene fibre addition showed superior frost resistance. This could provide theoretical guidance for the concrete frost-resistance design. (C) 2018 Published by Elsevier Ltd.

On the basis of freeze-thaw damage theories ,the freeze-thraw damage pattern and feature of ordinary Portland concrete (OPC) were studied under the aircraft de-icer with ethylene glycol .The micro-phase compositions of specimens were analyzed by X-ray diffractometer ,microstructure was observed by scanning electron microscopy and Micro area element was analyzed by energy dispersion X-ray .The main results were remarked as follows :The frost resistance of concrete under the action of lower concentration of EG was more serious than that of water ,while the freezing and thawing damage in higher concentration of ethylene glycol was slightly lower than that of water .The lower concentration of aircraft deicing fluid results in more serious damage to the concrete .The freeze-thaw damage of OPC with low concentration of ethylene glycol was mainly the surface spalling failure ,and the mass loss reached the standard of failure firstly .However ,when immersed in high concentration of ethylene glycol ,the freeze-thaw damage of OPC was that the relative dynamic elastic modulus first came up to the failure stand ,which was mainly embodied in severe spalling at the ends .In a whole ,the freezing and thawing damage was a physical damage mechanism .No new substances were formed during the freezing and thawing experiment in EG . The hydrated calcium silicate gel and crystal of calcium hydroxide were not changed in cement .The freez-ing thawing damage mechanism of OPC in EG solution was the same as that in water ,which was mainly dominated by the freezing pressure .

The present study uses the dynamic modulus of elasticity as the damage variable and derives an equation that can be used to determine the freeze-thaw fatigue damage in concrete under water and deicing salt freeze-thaw conditions based on the mechanical fatigue damage theory. The present study derives a model for predicting the service life of concrete subjected to freeze-thaw cycles under different freeze-thaw systems. Accumulative model is also presented for predicting the service life of concrete subjected to freeze-thaw cycles under a combination of different freeze-thaw systems in natural environmental conditions; this model uses the fatigue damage accumulation theory along with the fact that the mechanism of freeze-thaw damage in concrete is the same in the natural freeze-thaw environment as it is under standard laboratory rapid freeze-thaw conditions. The equation for determining the freeze-thaw fatigue damage in concrete and the model for predicting the service life of concrete subjected to freeze-thaw cycles are verified based on a large amount of test data. The relationship between the number of freeze-thaw cycles concrete undergoes under laboratory condition and natural environmental conditions is recalculated. In addition, applying the cumulative model for predicting the service life of concrete subjected to freeze-thaw cycles under natural environmental conditions is discussed. The results show that the curves of the freeze-thaw fatigue damage for different types of concrete obtained from the proposed equation have the same trends and are in good agreement with the curve of the measured relative dynamic modulus of elasticity. Furthermore, the relative errors between the values calculated from the model for predicting the service life of concrete subjected to freeze-thaw cycles and the values measured under different cooling rates are less than 3%; this result indicates that the model for predicting the service life of concrete subjected to freeze-thaw cycles and its cumulative model can satisfactorily predict the natural fatigue life of concrete subjected to freeze-thaw cycles in an actual freeze-thaw environment. The analysis and calculation of the measured laboratory condition and natural environmental conditions data shows that the ratio of the standard fatigue life of concrete subjected to freeze-thaw cycles under rapid laboratory freeze-thaw conditions to the natural fatigue life of the same concrete subjected to freeze-thaw cycles in the actual environment is approximately 1:8–1:9, instead of the previously reported range of 1:10–1:15.