Furthermore, CSA concrete exhibits a higher capillary absorption capacity than OPC concrete, which results in chloride accumulation on its surface. However, the diffusion capacity of chloride in CSA concrete is significantly lower than that in OPC concrete.The enhancement of the durability of sulfoaluminate cement (CSA) in marine environments is of great importance. To this end, an investigation was carried out involving the placement of CSA concrete in the tidal zone of Zhairuoshan Island, Zhoushan, China, and subjected to a 20-month marine tidal exposure test. The comparison was made with ordinary Portland cement (OPC) concrete to evaluate the effectiveness of the former. The test findings indicate that the compressive strength of both types of concrete is reduced by seawater dry-wet cycling, and the porosity of the surface concrete is increased. However, the compressive strength of CSA concrete is observed to be more stable under long-term drying–wetting cycles. When the ettringite in the CSA surface concrete is decomposed due to carbonization and alkalinity reduction, its products will react with Ca Therefore, CSA cement represents an important aspect of green development in the cement industry.Calcium sulfoaluminate cement (CSA) is a cementitious material produced from raw limestone, bauxite, and calcium sulfate . CSA raw clinker ,4. Meanw clinker ,6. Moreo4A32S), and gypsum (C3A·3C3) [3A·C2S reacts with water to form calcium silicate hydrate gel (C-S-H) and portlandite (CH). Subsequently, the reaction between portlandite, aluminum hydroxide, and gypsum results in the formation of ettringite [The main mineral constituents of CSA cement are ye’elimite (Cde (AH3) . Meanwhi’elimite ,9. C2S rtringite . CSA cemtringite , resultitringite .In the marine environment, the degradation of concrete structures is caused by multiple physical and chemical factors such as various agents in seawater, including sulfate ions, magnesium ions, and chloride ions, etc., carbonation, freeze-thaw damage, the scouring of waves and floating objects and microbial attachment, etc. ,16,17,18It is widely acknowledged that CSA concrete exhibits superior performance in freeze-thaw environments compared to OPC concrete owing to its lower porosity and the inclusion of more coarse pores ,22. It hFor this study, the chemical composition presented in To conduct the compression and chloride penetration tests in the marine environment, the 100 × 100 × 100 mm cubic concrete samples were prepared. After the concrete was molded for 6 h, the molds were removed and placed in a standard curing room with a temperature of 20 ± 2 °C and a relative humidity of 98 ± 2% for 28 days. To achieve one-dimensional chloride penetration, all sides of the concrete samples, except one, were coated with epoxy resin after 21 days of curing. The samples were then left to dry for 3 days, followed by applying epoxy resin to one side for a day and an additional 3 days of drying. This process was completed within the 28 days of standard curing; then, the concrete samples were transported to Zhairuoshan Island and placed in the tidal zone for the marine exposure test. Some samples remained in the standard curing room as control samples.The samples were placed in the tidal zone at the Material Corrosion Field Observation and Research Station of Zhejiang University, in Zhairuoshan Island, Zhoushan, Zhejiang Province  as shown in The compressive strength of the concrete samples was measured in triplicate using a YAW-3000B computer-controlled electro-hydraulic pressure testing machine  with a loading rate of 0.5 MPa/s. The strength values were obtained after a specified period of either standard curing or marine tidal exposure tests.The concrete samples, with a thickness of 30 mm, were ground into powder using an HDM-1A concrete grinding machine . The grinding process involved grinding every 1 mm of the first 6 mm of the sample’s thickness and every 2 mm for the remaining thickness. To ensure accuracy, powder samples were collected from two identical samples. The collected powders were passed through a 0.16 mm square hole sieve and then stored in sealed bags for the free chloride concentration test. The free chloride concentrations were measured using a rapid chloride ion content analyzer . Prior to measurement, 2 g of powder was dissolved in 20 g of deionized water, and the mixture was shaken vigorously for 10 min and left to stand for 24 h.To prepare for the mercury intrusion porosimetry test, the surfaces of the concrete samples, ranging from 0–10 mm, were crushed to a particle size of 2–3 mm  and preserved in alcohol. The samples were subsequently dried at 60 °C for 2 days and tested using an Auto Pore 9500 injection apparatus .To conduct X-ray diffraction analysis, the 2 mm-thick concrete surface samples were ground into <0.16 mm powders. The analysis used a D8 advance instrument  with Cu Kα (λ = 1.54 Å) radiation, operating at 40 kV voltage and 40 mA current in Bragg-Brentano geometry. The samples were scanned in the 2θ range of 5–89° at a scan rate of 0.02°.For the TGA analysis, the samples were prepared the same way as for the XRD analysis. The analysis was conducted using an SDT Q600 instrument  with a temperature increment of 10 °C/min in a nitrogen atmosphere, ranging from 25 to 1000 °C. After derivation, the DTG curves were obtained, showing peaks corresponding to the decomposition of various hydration phases.2 in the atmosphere or the conversion of ettringite due to alkalinity and temperature. Moreover, the long-term trends in compressive strength development for CSA and OPC concrete under marine tidal exposure differ, with the former showing an increase in strength up to 8 months, followed by stabilization, and the latter exhibiting a peak at 2 months, followed by a gradual decline. These findings suggest that CSA concrete may offer superior performance in terms of compressive strength under marine tidal exposure. This will be explained in further microstructural analysis.The pore structures of the concrete surface after marine tidal exposure for 2 months were investigated. The cumulative pore volume and the pore size distribution of the concrete surface are presented in The total chloride content includes free chloride, mainly resulting in steel corrosion due to its penetration, accumulation, and bound chloride. The X-ray diffraction (XRD) patterns of concrete surface samples from marine tidal exposure at varying durations are presented in Further, it can be observed from 3, as well as the decarbonation process of calcite. The weight loss at temperatures of 80–110 °C can be attributed to the decomposition of ettringite, while the weight loss at temperatures around 130–140 °C can be assigned to the dehydration of AFm. Furthermore, the presence of AH3 is confirmed by the weight loss at approximately 220–270 °C, whereas the decomposition of Friedel’s salt occurred at temperatures between 300–380 °C, and the decomposition of calcite (CaCO3) occurred around 600–700 °C.The thermogravimetric-differential thermogravimetric (TG-DTG) curves of concrete samples containing calcium sulfoaluminate (CSA) subjected to marine drying–wettingexposure tests for 2, 4, 12, and 20 months were presented in 2+ and SO42+ in seawater to regenerate ettringite. Additionally, the disappearance of AFm at 12 months may be related to the formation of Friedel’s salt between AFm and chloride ions.Observations from the TG-DTG curves of the 2mon-M phase compared to the 2mon-S phase reveal a significant decrease in ettringite content, an increase in calcium carbonate content, and the appearance of an endothermic peak of AFm. With the marine tidal exposure test, it can be observed from the TG-DTG curves as well as the mass loss table that ettringite content gradually decreased until 4 months, while the content of AFm and calcium carbonate gradually increased. This can mainly be attributed to the decomposition of ettringite. After 4 months, ettringite content began to increase, calcium carbonate content began to decrease, and AFm disappeared, as seen in 12mon-M and 20mon-M. The presence of Friedel’s salt was also found in 12mon-M and decreased greatly in 20mon-M. The above phenomenon can be attributed to the gradual weakening of the decomposition of ettringite with exposure time and the decomposed product of ettringite reacting with Ca2 in the atmosphere reacts with ettringite to produce calcite, AH3, and gypsum. The carbonization process causes a decrease in alkalinity within the concrete pore solution, which reduces the stability of ettringite and leads to its conversion into AFm and gypsum [The compressive strength of CSA concrete exhibits a gradual increase with exposure to marine tidal zone until it reaches a state of stability after 12 months. In contrast, the strength of OPC concrete tends to decrease slowly after 2 months. The increase in strength of CSA concrete is primarily attributed to the continuous hydration of unhydrated cement particles, leading to the formation of hydration products such as ettringite and aluminum glue that fill in gaps within the concrete . The pord gypsum ,40. Furt42− in seawater with the hydration products such as hydrated aluminates in OPC concrete, resulting in the formation of gypsum and ettringite, which in turn lead to an increase in concrete pores and cracks. Moreover, chlorides can bind to the surface of pores, predominantly on C-S-H and other hydrated cement phases, or react with C3A to form Friedel’s salt, which can also contribute to the expansion and cracking of concrete over time [Pores larger than 200 nm in OPC concrete are observed to increase significantly after marine drying–wetting cycles, thereby accelerating the transmission of chloride on the concrete surface. This phenomenon is primarily caused by the reaction of SOver time ,42.2+ and SO42− can regenerate ettringite and fill the concrete surface without damaging the concrete, thereby retarding the deterioration caused by the drying–wetting cycles. In addition, CSA concrete has a limited ability to bind chloride, and even if Friedel’s salt forms, it is highly unstable in the pore solution system of CSA concrete. The low alkalinity and high sulfate content make Friedel’s salt prone to decomposition [The adaptability of the expansion process to the strength development of the concrete is the key factor in determining whether the delayed ettringite expansion will adversely affect the concrete. CSA concrete exhibits strong strength and adaptability to the expansion of ettringite. Thus, during the drying–wetting cycles, the decomposition products of ettringite in seawater rich in Caposition ,44. UndeThe compressive strength of CSA concrete and OPC concrete is susceptible to degradation under the marine drying–wetting cycles. However, it is notable that the compressive strength of CSA concrete exhibits greater stability under prolonged marine drying–wetting cycles;The corrosion mechanism of seawater on the two types of concrete varies under the influence of the marine drying–wetting cycles. OPC concrete is vulnerable to expansion and cracking due to the production of ettringite or Friedel’s salt resulting from the reaction of ions in seawater and its hydration products. On the other hand, in CSA concrete, carbonization and low alkalinity result in the decomposition of ettringite, which then reacts with seawater ions to generate ettringite suitable for its strength development;The penetration mechanism of chloride in the two types of concrete is distinct under the influence of marine drying–wetting cycles. The capillary absorption on the surface of CSA concrete is more pronounced, leading to chloride accumulation, while the interior remains relatively dry, resulting in slower chloride ion diffusion. Additionally, there is no convection zone in CSA concrete.In the long-term service of concrete in the marine environment, especially in the tidal zone, stable strength and relatively low chloride content are very important. This research reveals the potential of using CSA cement in a marine environment.


The shrinkage of core concrete during construction is the key reason for the separation of steel pipes and core concrete. Utilizing expansive agents during cement hydration is one of the main techniques to prevent voids between steel pipes and core concrete and increase the structural stability of concrete-filled steel tubes. The expansion and hydration properties of CaO, MgO, and CaO + MgO composite expansive agents in C60 concrete under variable temperature conditions were investigated. The effects of the calcium–magnesium ratio and magnesium oxide activity on deformation are the main parameters to consider when designing composite expansive agents. The results showed that the expansion effect of CaO expansive agents was predominant in the heating stage (from 20.0 °C to 72.0 °C at 3 °C/h), while there was no expansion in the cooling stage ; the expansion deformation in the cooling stage was mainly caused by the MgO expansive agent. With the increase in the active reaction time of MgO, the hydration of MgO in the heating stage of concrete decreased, and the expansion of MgO in the cooling stage increased. During the cooling stage, 120 s MgO and 220 s MgO resulted in continuous expansion, and the expansion curve did not converge, while 65 s MgO reacted with water to form brucite in large amounts, leading to its lower expansion deformation during the later cooling process. In summary, the CaO and 220 s MgO composite expansive agent in the appropriate dosage is suitable for compensating for the shrinkage of concrete in the case of a fast high-temperature rise and slow cooling rate. This work will guide the application of different types of CaO-MgO composite expansive agents in concrete-filled steel tube structures under harsh environmental conditions. Concrete-filled steel tubes, as composite structures, can enhance the performance of concrete and steel. It has a higher bearing capacity, stability, and economic benefit when compared to the individual components; hence, it is frequently utilized in large bridge structures ,2,3. MatDecreasing the shrinkage or causing the slight expansion of the concrete in the steel pipe could be crucial to preventing the separation of the steel pipe and concrete. Utilizing expansive agents during cement hydration is one of the main techniques to prevent voids between the steel pipe and core concrete and increase the structural stability of concrete-filled steel tubes . In cemeSince the temperature of concrete changes during the construction process, the performance of concrete at room temperature cannot reflect its application performance in the actual building. For example, for a steel tube filled with C50~C80 concrete with a large pipe diameter, the central temperature of core concrete can reach 50~60 °C. Due to heat dissipation to the environment, the concrete will undergo a rapid temperature drop after reaching the temperature peak. For example, during the construction of the Zangmu Bridge in Tibetan areas in China, the average temperature drop rate of the core concrete reached 3 °C/d after the temperature rise, which created a big challenge and required building non-void concrete-filled steel tubes. Thus, studying the effect of an expansive agent exposed to the actual temperature history is more valuable for engineering applications.Furthermore, utilizing a single type of expansive agent to compensate for the shrinkage deformation of concrete in different stages is not sufficient. Liu et al.  designedThis work investigates the deformation performance of C60 concrete mixed with different contents of a CaO expansive agent, MgO expansive agent, and CaO-MgO composite expansive agents under the condition of a simulated temperature history. The temperature variation process used in this work was first monitored for a part of the core concrete in the steel tubes of the Zangmu Bridge in Tibet in China. This temperature history could be suitable for simulating the deformation performance of concrete under the typically closed condition of the harsh plateau environment. Afterward, a reasonable amount of a calcium oxide and magnesium oxide composite expansive agent was mixed with concrete and poured into tubes. The effect of the CaO-MgO ratio of the composite expansive agent on the concrete was investigated by testing its deformation performance by using an SBT-CDMI wireless monitoring system, and the activity time of MgO on the deformation was considered. Finally, the hydration products and microstructures of cement pastes with different types of expansive agents were also studied. These findings will guide the use of CaO-MgO composite expansive agents in concrete-filled steel tubes and other non-shrink concrete.The cement used in this study was ordinary Portland cement 42.5, which was produced by Conch Cement Plant, and conformed to the Chinese standard GB175-2007 . Fly ashThree MgO expansive agents with different active reaction times  were prepared by calcining magnesite in a suspension kiln. The 65 s, 120 s, and 220 s MgO expansive agents were calcined from magnesite powder (particle size ≤ 160 μm) at 800 °C, 950 °C, and 1050 °C, respectively, in a suspension kiln. The citric acid method was used to determine the active reaction time of the MgO expansive agent . The act2 and CaO. The primary mineral of the CaO expansive agent is CaO, containing a small amount of CaSO4.The XRD patterns of MgO expansive agents and CaO expansive agents are shown in Replacing a portion of the cement with fly ash can reduce the amount of heat released in concrete, the adiabatic temperature rise in concrete, and the autogenous shrinkage of concrete, which decreases the risk of concrete cracking, particularly in concrete containing a large amount of fly ash. Therefore, fly ash was used in this design for its application in concrete-filled steel tubes. The added content of MgO was selected according to T/CECS 10082—2020 Calcium and Magnesium Oxides Based Expansive Agent for Concrete .The test was conducted using a temperature and humidity environment simulation test chamber for concrete made by Nanjing Huanke Testing Equipment Co., Ltd., Nanjing, China., to simulate the temperature history of a C60 concrete-filled steel tube. The temperature and humidity environment simulation test chamber for concrete is shown in The C60 concrete in the PVC pipe was in a state of absolute humidity. The concrete deformation recorded by the wireless monitoring system was mainly caused by autogenous volume deformation and temperature deformation. The temperature history of the concrete was mainly controlled by the environmental temperature change in the test chamber. Firstly, the test chamber was started, and the initial temperature inside the chamber was controlled at (20.0 ± 1.0) °C. After 20 h at a constant temperature, the test chamber was heated up to (72.0 ± 1.0) °C at 3 °C/h, then cooled down to (30.0 ± 1.0) °C at 3 °C/d, and then cooled down to (20.0 ± 1.0) °C at 0.7 °C/h. After the temperature fell to (20.0 ± 1.0) °C, the test chamber was turned off. The temperature of concrete varied with the external environment. The temperature variation process used in this work was first monitored for a part of the core concrete in the steel tubes of the Zangmu Bridge in Tibet in China. Its typical temperature history can be used to simulate the deformation performance of concrete embedded in large-diameter tubes under the closed condition of the harsh plateau environment.Samples were placed at a constant temperature of 20 °C about 24 h before the experiment. Then, 10.0 g of the expansive agent was weighed and put into an ampoule bottle, and 10 mL of water was injected into the bottle with a syringe. Then, the paste was stirred quickly and evenly and put into the test channel of a TAM AIR isothermal calorimeter. The hydration and cumulative heat release rates were tested for 3 consecutive days.To prevent the influence of components such as sand and gravel aggregate on the analysis of experimental results, the experiment was conducted with a cementitious material paste specimen. The expansive agent replaces the fly ash in an equal amount and does not replace the cement. The cement paste specimen was made according to a water–binder ratio of 0.29. After the paste sample was stirred evenly, it was poured into a 100 mL plastic test tube shown in . The plaThe micromorphology of cement paste with the expansive agent was characterized by SEM. The samples were processed as follows: cutting the two ends of the hardened paste in the plastic bottle to 5 mm, crushing the rest into small pieces, putting them into anhydrous ethanol for dehydration for 24 h shown in , drying The autogenous volume deformation and temperature history of C60 concrete with 0%, 6%, and 8% CaO expansive agents under simulated variable temperature conditions are shown in The deformation process of C60 concrete with 0%, 6%, and 8% CaO expansive agents in the cooling stage is depicted in 2 crystals will result in the volume expansion of concrete, especially with higher amounts of the CaO expansive agent. Details are provided in The hydration of the CaO expansive agent in concrete to form Ca(OH)As further demonstrated by the above experimental results, the expansion effects of 6% and 8% CaO expansive agents were predominantly reflected in the heating stage, while there was no expansion in the cooling stage. The CaO expansive agent might have been consumed by hydration in the early high-temperature heating stage. So, there was almost no expansion in the cooling stage. With the increase in the amount of the CaO expansive agent, the expansion deformation of concrete in the heating stage increased, and consequently, the internal expansion stress of concrete increased. C60 concrete with the 8% CaO expansive agent triggered higher expansion stress in the heating stage, which led to the augmentation of concrete creep in the cooling stage. Accordingly, the expansion amount with the 8% CaO expansive agent appeared to shrink back in the cooling stage.As revealed by the above experimental findings, the distinction in the expansion effects of CaO expansive agents at distinct dosing levels was primarily reflected in the heating stage. For C60 concrete structures, CaO expansive agents could only compensate for the early autogenous shrinkage of concrete. The autogenous volume deformation and temperature history of C60 concrete with 0%, 4% 65 s MgO, and 4% 120 s MgO expansive agents subjected to a simulated temperature history are displayed in The expansion curves of 4% 65 s MgO and 4% 120 s MgO expansive agents in the cooling stage are shown in As demonstrated by the above experimental findings, in this temperature history, CaO expansive agents can only compensate for the early concrete shrinkage and store early expansion stress and have no expansion compensation effect in the cooling stage. If CaO expansive agents are employed to increase the amount of concrete expansion, there would be an increment in concrete creep during the cooling stage. Using the single admixtures of MgO expansive agents, C60 concrete with the 4% 65 s MgO or 4% 120 s MgO expansive agent was in a shrinkage state at 24.5 d after the initial setting time and had not reached the expansion or non-shrinkage state. If the experiment raises the amount of MgO to realize the objective of non-shrinkage, the workability of concrete will be seriously decreased, leading to the formation of cavities between the steel pipe and concrete. The experiments of single MgO expansive agents also show that with this temperature history, the activity reaction time of MgO increases, the hydration of MgO in the concrete heating stage decreases, and the expansion of MgO in the cooling stage rises.Whether the delayed expansion of MgO could be employed to compensate for the shrinkage of concrete during the cooling stage and realize the compensation for shrinkage deformation in concrete remains for the complete process to be determined. For the sake of selecting suitable CaO and MgO composite expansive agents to compensate for the shrinkage of C60 concrete in the whole process, the expansion deformation laws of expansive agents with 2% MgO  and 6% CaO composite were compared and analyzed.The volume deformation and temperature history of C60 concrete with 0%, 6% CaO, and 6% CaO + 2% MgO expansive agents under simulated variable temperature are depicted in The deformation process of C60 with 0%, 6% CaO, and 6% CaO + 2% MgO expansive agents in the cooling stage is depicted in The autogenous volume deformation and temperature history of C60 concrete with 0%, 6% CaO + 2% 65 s MgO, and 6% CaO + 4% 65 s MgO expansive agents under simulated variable temperature conditions are shown in The deformation process of C60 concrete with 0%, 6% CaO + 2% 65 s MgO, and 6% CaO + 4% 65 s MgO expansive agents at in cooling stage is depicted in As revealed by the experimental results, the CaO expansive agent has the advantages of a fast hydration rate, large expansion deformation, and a certain amount of expansion stress in concrete in the heating stage. In the cooling stage, concrete-filled steel tubes can achieve a microexpansion or non-shrinkage state by using the delayed expansion property of the MgO expansive agent. The hydration rate of longer-sintered MgO is higher. For the temperature history used, 2% 65 s MgO did not show significant expansion in the cooling stage, while expansion compensation could also be produced in the cooling stage when 65 s MgO expansive agent doping was increased to 4.0%. Under these temperature conditions, 220 s MgO with low activity demonstrated superior compensation for the cooling shrinkage. The expansion performance of 220 s MgO compounded with CaO and MgO composite expansive agents demonstrated strong temperature sensitivity, which is suitable for compensating for the shrinkage of C60 structural concrete with a high-temperature rise and slow cooling rate.The exothermic courses of hydration of distinct expansive agents in pure water are demonstrated in 2 minerals. After being cured under variable temperature conditions, as shown in 2 crystals appeared in the cement paste after adding the CaO expansive agent. As the content of the CaO expansive agent increased, the content of Ca(OH)2 generated by hydration also increased. As can be seen in 2 generated by the hydration of the CaO expansive agent. Microcracks were not observed in the cement paste containing the 4% CaO expansive agent. The reason for this could be that the crystallization pressure of Ca(OH)2 crystals generated by the 4% CaO expansive agent in the cement paste does not exceed the tensile strength of the cement paste [After being cured under variable temperature conditions, as shown in nt paste .2 with a hexagonal plate structure formed by the hydration of the CaO expansive agent. The energy spectrum test results of EDS Spot 2 in the microscopic picture of the cement paste with the 6% CaO expansive agent show that the hexagonal plate material consists of Ca(OH)2 crystals [crystals  2 generated by the hydration of the CaO expansive agent. In the cement paste with the 4% MgO expansive agent, no obvious microcracks were found, whereas microcracks appeared in the cement paste with the 6% CaO and 2% 220 s MgO expansive agent.The microscopic analysis shows that the CaO expansive agent can produce a large number of hexagonal plate Ca(OH)As mentioned above, different types of expansive agents have different hydration and expansion characteristics. In actual projects, the autogenous shrinkage and temperature-fall-induced shrinkage generated in C60 concrete in the early and middle hydration stages are large, with a wide temperature variation range. The large expansion of concrete should be compensated. In addition, the later autogenous shrinkage and temperature-fall-induced shrinkage of concrete are smaller, and microexpansion is needed to compensate for them, thus inhibiting their shrinkage to stabilize the expansion precompression stress formed in the early stage. Finally, shrinkage-free concrete should be achieved in all hydration stages.The CaO expansive agent is beneficial to early expansion, while the MgO expansive agent can achieve middle- and late-age expansion; thus, a potentially good method to realize shrinkage-free concrete throughout the whole process is to design multicomponent expansive agents with CaO and MgO compounds.In this study, the influence of the temperature history of core concrete in a steel tube arch on the expansion of C60 concrete with specific-activity MgO and CaO expansion components in certain proportions, a single CaO expansive agent, and a single MgO expansive agent in C60 concrete was investigated. The experimental results showed that the expansion effect of CaO expansive agents was predominantly reflected in the heating stage, while there was no expansion in the cooling stage. The reason for this is that CaO expansive agents completely reacted in the heating stage of this temperature history of C60 core concrete in a steel tube arch, according to microthermal experimental results. Moreover, the microscopic morphology showed that the expansion energy of the CaO expansive agent is larger. Microcracks appeared in the cement paste with the 6% CaO expansive agent. Liu et al.  found thFollowing the actual temperature history of concrete, selecting the proper activity of MgO expansive agents and the ratio of CaO and MgO in multicomponent expansive agents could compensate for concrete shrinkage throughout the whole process. Zhao et al.  also fouUtilizing appropriate expansive agents during cement hydration is one of the main techniques to compensate for concrete shrinkage and prevent voids and debonding between the steel pipe and core concrete in concrete-filled steel tubes. In this work, calcium oxide and magnesium oxide composite expansive agents were designed with different calcium/magnesium ratios and various types of MgO activities with different calcination temperatures and times. Their expansion and hydration properties in C60 concrete under variable temperature conditions were investigated, with the aim of simulating the real construction process. Subsequently, the effect of the calcium–magnesium ratio and magnesium oxide activity on deformation was analyzed. The main conclusions are summarized as follows:(1) The expansion effects of 6% and 8% CaO expansive agents were predominantly reflected in the heating stage (from 20.0 °C to 72.0 °C at 3 °C/h), while there was no expansion in the cooling stage . The CaO expansive agent was hydrated in the early high-temperature heating stage, resulting in almost no expansion in the cooling stage. With the increase in the amount of the CaO expansive agent, the expansion deformation of concrete in the heating stage increased, and consequently, the internal expansion stress of concrete increased.(2) The expansion deformation in the cooling stage was mainly caused by the MgO expansive agent. The 120 s MgO and 220 s MgO expansive agents resulted in continuous expansion during the cooling stage, and the expansion curve did not converge. The 220 s MgO expansive agent produced more expansion than 120 s MgO. During the heating process of the concrete, the majority of 2% 65 s MgO reacted with water to form brucite in large amounts, leading to its lower expansion deformation in the later cooling process. With the increase in the active reaction time of MgO, the hydration of MgO in the heating stage of concrete decreased, and the expansion of MgO in the cooling stage increased.(3) The construction and building temperatures show a remarkable influence on the expansion performance of CaO and MgO composite expansive agents. In actual projects, the temperature history of concrete varies immensely from structure to structure on account of many factors, such as the material, environment, and structural dimensions. In accordance with the actual temperature history of concrete, selecting the proper activity of MgO and the ratio of CaO to MgO could compensate for concrete shrinkage throughout the whole process. The CaO and 220 s MgO composite expansive agent shows strong temperature sensitivity, which is suitable for compensating for the shrinkage of concrete in the case of a fast high-temperature rise and a slow cooling rate.This work will guide the application of different types of CaO-MgO composite expansive agents in concrete-filled steel tube structures. More work should be conducted in the future to build a theoretical model of temperature effects on different components of the expansive agent to guide engineering projects.


Preoperative differentiation between IgG4-related orbital disease (IgG4-ROD) and orbital mucosa-associated lymphoid tissue (MALT) lymphoma has a significant impact on clinical decision-making. Our research aims to construct and evaluate a magnetic resonance imaging (MRI)-based radiomics model to assist clinicians to better identify IgG4-ROD and orbital MALT lymphoma and make better preoperative medical decisions.MR images and clinical data from 20 IgG4-ROD patients and 30 orbital MALT lymphoma patients were classified into a training  or validation set . Radiomics features were collected from T1-weighted (T1WI) and T2-weighted images (T2WI). Student’s t-test, the least absolute shrinkage and selection operator (LASSO) and principal component analysis (PCA) were conducted to screen and select the radiomics features. Support vector machine (SVM) classifiers developed from the selected radiomic features for T1WI, T2WI and combined T1WI and T2WI were trained and tested on the training and validation set via five-fold cross-validation, respectively. Diagnostic performance of the classifiers were evaluated with area under the curve (AUC) readings of the receiver operating characteristic (ROC) curve, and readouts for precision, accuracy, recall and F1 score.Among 12 statistically significant features from T1WI, four were selected for SVM modelling after LASSO analysis. For T2WI, eight of 51 statistically significant features were analyzed by LASSO followed by PCA, with five features finally used for SVM. Combined analysis of T1WI and T2WI features selected two and four, respectively, for SVM. The AUC values for T1WI and T2WI classifiers separately were 0.722 ± 0.037 and 0.744 ± 0.027, respectively, while combined analysis of T1WI and T2WI classifiers further enhanced the classification performances with AUC values ranging from 0.727 to 0.821.The radiomics model based on features from both T1WI and T2WI images is effective and promising for the differential diagnosis of IgG4-ROD and MALT lymphoma. More detailed radiomics features and advanced techniques should be considered to further explore the differences between these diseases. Lymphoproliferative disorders are one of the common etiologies that can occur in the orbital space. In an epidemiological survey in Japan, mucosa-associated lymphoid tissue extranodal marginal zone B-cell lymphoma (MALT lymphoma) was the most common subtype of lymphoproliferative diseases, and IgG4-related ophthalmic disease (IgG4-ROD) ranked second .Orbital MALT lymphoma is a low-grade, non-Hodgkin lymphoma subtype, with a low incidence that accounts for only 1% of all non-Hodgkin lymphomas. However, it is one of the most common adult primary orbital tumors, accounting for 55% of orbital malignancies . Common Due to the non-specific clinical manifestations of MALT lymphoma and IgG4-ROD, differential diagnosis of these two conditions based on serum IgG4 levels and clinical manifestations alone can be challenging , 10. SevHowever, by maximizing the value of acquired images, improving the quantification of image features to fully interpret the image information, and combining with clinical evaluations, it is possible to provide clinicians with more powerful imaging evidence to identify the two diseases, and to guide the selection of more reasonable and efficient treatment for patients.With increasing digitalization in medicine, artificial intelligence and machine learning has become crucial in this era of big data. Similar to the process of human learning, machine learning can summarize and filter large amount of data to extract the most representative features , 17. RadHowever, as far as we know, radiomics studies to differentiate IgG4-ROD from orbital MALT lymphoma are rare. Considering previous studies have shown that MRI is an effective method for precise visualization of lesions in these two orbital diseases, we seek to determine whether radiomics analysis can improved the differential diagnosis of IgG4-ROD and orbital MALT lymphoma.The research is a retrospective cross-sectional study approved by the institutional review board of Shanghai Changzheng Hospital. Written consent from patients were waived.All patients were diagnosed and treated at the Department of Ophthalmology, Shanghai Changzheng Hospital from 2015 to 2021. No history of other orbital diseases, tumors or previous surgeries were present in the patient cohort. The inclusion criteria for orbital MALT lymphoma was extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue confirmed by postoperative histopathology and pathologically IgG4 staining less than diagnostic criteria for IgG4-ROD. The inclusion criteria for IgG4-ROD was based on the 2020 Japanese diagnostic criteria for IgG4-related diseases [All imaging was performed using a 3.0-T MR equipment (Achieva 3.0T (TX) DS MR system, Philips Healthcare) with imaging parameters shown in Table Using an open-source python package, Pyradiomics (version 3.0.1), 107 radiomics features were extracted from patients’ MR images. These features were selected to represent the lesions and used for radiomics and differential diagnosis by the following analyses. Student’s t-test was first carried out to screen out statistically insignificant imaging features. Then the least absolute shrinkage and selection operator (LASSO) algorithm, which is effective in reducing overfitting and improving the prediction accuracy, was used to identify the optimal features. The regularization parameter (λ) was tuned by the minimum criteria and features were selected using a 10-fold cross-validation method. Radiomics feature weightage maps were drawn using the most important features with non-zero coefficient. In addition, principal component analysis (PCA) was also conducted to further limit the number of radiomics features that would be used to train the predictive model to avoid overfitting caused by redundant features. Finally, four features from T1WI, five from T2WI, and six from combined T1WI and T2WI analyses were selected to construct the predictive models.https://www.r-project.org).The radial basis function (RBF) kernel was used for SVM. The parameters were optimized with respect to the training set. The five-fold cross-validation (CV) method (repeated 10 times) was used to train and test the classifiers and the area under the receiver operating characteristic (ROC) curve was used to evaluate their prognostic performance. The entire analytical procedure was accomplished with open-source packages, including Scikit-learn, matplotlib, numpy, pandas and graphviz in Python 3.7.11; PCA was conducted with the R statistical software . The values of precision, accuracy, recall and the F1 score were calculated to evaluate the performance of the diagnosis model. All data with P < 0.05 was considered statistically significant.Statistical analyses were performed with the SPSS  and R statistical software  analysis, 16 from gray-level run-length matrix (GLRLM) analysis, 16 from gray-level size zone matrix (GLSZM) analysis, 14 from gray-level differential matrix (GLDM) analysis and five from neighborhood gray tone difference matrix (NGTDM) analysis . The intTo identify statistically significant T1WI imaging features between the two diseases groups, a Student’s t-test was carried out, which identified 12 features in the training image set. To enhance the prediction accuracy and avoid overfitting, we performed the LASSO regression for T1WI images Fig. A. FittinSVM prediction models were constructed using the features described in Table Differential diagnosis between IgG4-ROD and orbital MALT lymphoma have always been a difficult clinical problem. In this study, for patients with orbital eye diseases, contrast-enhanced MRI, which were not included for radiomics analysis, are less commonly used compared to routine T1WI and T2WI. IgG4-ROD and orbital MALT lymphoma have also been shown to have some differential features in T1WI and T2WI. Thus, we focused our attention on T1WI and T2WI, which were selected for this study to determine whether radiomics analyses can extract more information that will assist physicians with the differential diagnosis of IgG4-ROD and orbital MALT lymphoma.Previously, infraorbital nerve enlargement was observed in IgG4-ROD frequently , while iThe usage of radiomics in differential diagnosis of IgG4-ROD and orbital MALT lymphoma embodies several advantages. First, as there are few published studies that distinguish IgG4-ROD from orbital Malt lymphoma, this research may shed some light on the differential diagnosis of these diseases through radiomics analysis of MR images. Second, quantitative information extracted from MR images instead of qualitative description of these images will reduce human error in diagnosis. Lastly, objective digital features and repeatable experimental results may help young clinical ophthalmologists to correctly diagnosis these two different conditions and select the appropriate treatment.There are inevitably some limitations in this study. First, the regions of interest were manually drawn, which were time consuming and may be prone to error. Thus, future studies should focus on performing automated segmentation of the lesions. Second, the limited sample size from a single center is likely to create biases within this study. Although we have restricted the number of optimal features used to construct the predictive models to avoid overfitting, the study can benefit from larger sample size and independent validation data sets. Extensive optimization and validation, involving multi-center studies, will improve the generalizability of our research.To improve the differential diagnosis of IgG4-ROD and orbital MALT lymphomas, we have extracted several important radiomics features from T1WI and T2WI MR images. The radiomics models that were generated from these features showed promising predictive values and may provide useful guidance for clinical decision-making. More detailed radiomics features and advanced techniques should be explored to further improve the differential diagnosis of IgG4-ROD and orbital MALT lymphomas.


X-ray crystallography is the most reliable method for structure elucidation and absolute configuration determination of organic molecules based on their single-crystal forms. However, many analytes are hard to crystallize because of their low melting points (an oily state at room temperature) or conformational flexibility. Here, we report the crystallization of a macrocycle, CTX[P(O)Ph] (host), which is a cyclotrixylohydroquinoylene (CTX) derivative, with 26 oily organic molecules (guests), which is applied for the structural determination of the guest with X-ray crystallography. With the aid of the host, CTX[P(O)Ph], the guest molecules were well-ordered with full occupancy in crystal structures. In most cases, at least one guest structure without any disorder could be observed; solvent masking was not necessary for the single crystal X-ray structural analysis, and thus the structures of the guests could be successfully determined, and the absolute configuration could be assigned reliably for chiral guests with this method. The crystallization mechanism was further discussed from theoretical and experimental perspectives, suggesting that the negative electrostatic potential surface of CTX[P(O)Ph] and noncovalent interactions between the host and guest were crucial for the ordered arrangements of the guest. CTX[P(O)Ph], a censer-shaped macrocycle, was used as a host to crystallize with oily guest organic molecules. Their well-ordered crystal structures and absolute configurations were described unambiguously by single-crystal X-ray diffraction. In contrast, thanks to the anomalous scattering,2 single-crystal X-ray diffraction (SCXRD) can assign absolute configuration reliably. However, not all molecules are compatible with the SCXRD method. For example, oily samples are challenging to solidify or crystallize at room temperature. In addition, the SCXRD method also does not work well for molecules that have too flexible structural moieties or are liable to form precipitates, resulting in the formation of an amorphous powder instead of high-quality single crystals.When a novel organic compound is synthesized and purified successfully, the first thing to do is to determine its structure and absolute configuration if it is chiral; this is always a significant task, whether the researchers are chemists, pharmacists, or material scientists. Compared with various analytical methods, such as nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry, single-crystal X-ray crystallography provides direct evidence to support molecular structure information, and thus, in most cases, the results obtained are more definitive.3 The most famous one may be the “crystalline sponges (CSs)” method developed by the Fujita group. Small organic guest molecules are absorbed into the pores or channels of porous metal–organic frameworks (MOFs); the absorption is driven by strong π–π, CH–π, and charge–transfer interactions between guest molecules and the electron-deficient π-plane of MOFs.4 The orderliness is transferred from the crystalline networks (host molecules) to the pores, and finally, to the guest molecules so that the guest molecules become well-ordered and can be observed by SCXRD. The absolute configuration of the guests can also be well-defined because of the anomalous scattering of the heavy atoms in the networks.5 In addition, the CSs method can be performed with SCXRD analysis at nanogram to microgram scales of the guests, which allows this method to be combined with liquid chromatography4 or gas chromatography6 and ensures its application in studying complex samples and samples available in small amounts. The Yaghi group also used MOFs to determine the structure of a series of guest molecules.7 Coordination bonds were introduced between the MOFs and guest molecules to anchor the guests and further ensure their ordered arrangement. The chirality of the MOF backbone provides a reference for the assignment of the absolute configuration of the guests. Apart from MOFs, hydrogen-bonded frameworks, which are another kind of porous crystalline network, constructed by guanidinium and organosulfonate ions, are capable of encapsulating a range of guest molecules into the pores to elucidate their structure.8 In addition, non-network structures, such as supramolecular macrocycles9 and metal-macrocycles10 with inherent cavities and large organic molecules generating channels when packing9 can also form co-crystals or clathrates with various guest molecules. For instance, tetraaryladamantanes developed by the Richert group have been used as crystallization chaperones to determine the absolute configuration of chiral molecules.11 In general, the suitable sizes and shapes of pores or cavities are indispensable in the design of host molecules suitable for the crystallization with guests because they can accommodate guest molecules, and more importantly, help orient the guests into an array in a periodic manner. However, there are some problems in such systems. For instance, only some fraction of the cavities are occupied by the guest molecules, while the other part remains vacant or is accommodated by residual solvent molecules. Some guest molecules have two or more different orientations in the pores. As a result, in some cases, the guest molecules were partially or even totally disordered,9 or their occupancy was considerably lower than 100%,10 which greatly hindered molecular structure and the determination of its absolute configuration.Recently, several strategies have been proposed to help study molecules that pose challenges in obtaining single crystals and address the limitations discussed above.13 In the packing mode of the crystal structures of the guest molecules@CTX[P(O)Ph], the guest molecules are present in the layers or channels formed by the assembly of the host molecules, and no hydrogen-bonded framework is found. Therefore, the crystal structures in this work are clathrates. As a macrocycle, CTX[P(O)Ph] could trap the guest molecules above its cavity through host–guest interactions, which lowered the guest molecules' degrees of motion freedom and induced them to form an array in a uniform fashion. On the other hand, different from traditional macrocycles that have high symmetry and well-defined cavities, such as pillararene14 and cucurbituril,15 the small size of the cavity of CTX[P(O)Ph] was a censer-like shape that could not fully accommodate guest molecules and the guest molecule avoid existing in the cavity in low occupancy or disordered form. As a consequence, there was at least one guest molecule without any disorder in most cases, and the occupancy of all guest molecules was 100%. Such a regular alignment was in favor of determining the chemical structure, especially the absolute configuration of oily compounds.Herein, a kind of nonporous phosphorylated macrocyclic host molecule named CTX[P(O)Ph] is reported that can help a range of oily organic compounds crystallize, and thus, aid the elucidation of their structure and absolute configuration . It was 16 Its single-crystal data was collected to originally verify the structure. However, it was found that the solvent molecules  tend to retain the crystal structure. Once the solvent molecules are located in or above the small cavity of CTX[P(O)Ph], the occupancy becomes 100% and no disorder sign is observable. Moreover, DMSO, known as a universal solvent with a high boiling point, could also be used to cultivate the single crystal of CTX[P(O)Ph], simply by dissolving CTX[P(O)Ph] powder in DMSO and leaving it to stand for several days. Such uncommon phenomena drew our attention and encouraged us to explore the application of CTX[P(O)Ph] in crystallization with the guest molecules and for the structural determination of the guests based on X-ray crystallography.The macrocyclic host molecule, CTX[P(O)Ph], was first synthesized in our previous work.17 The crystal structures shown in R1 and wR2 values after refinement. Oak Ridge thermal ellipsoid plot (ORTEP) and the superposition of electron density maps (Fo map) onto the refined results in 12 In GM 1–8 and GM 10–11, the ORTEP showed reasonable thermal vibration, and the superimposed graph illustrated the electron density to be well assigned to the guest structure.At the outset, CTX[P(O)Ph] was used to crystallize with a series of oily organic samples with different functional groups (GM 1–11); these organic samples were used as the target guest molecules to determine their structures.NMR spectroscopy is a powerful approach for structure determination of organic compounds. However, there are still some organic molecules whose structures are difficult to define with NMR spectroscopy. For instance, 4-chloro-3-fluoroanisole (GM 12) and 3-bromo-4-chloroanisole (GM 13) are hard to distinguish from their corresponding isomers (3-chloro-4-fluoroanisole and 4-bromo-3-chloroanisole) with NMR spectroscopy because of the similar electron-withdrawing effect of halogen atoms. They are both challenging to crystalize because of their oily state at room temperature. In contrast, their structures could be well-defined after crystallization with CTX[P(O)Ph] . The halConformationally flexible molecules with long chains are hard to crystallize, which is well known. Some flexible oily guest molecules (GM 14–18) were chosen, and all these structures could be determined finely by this method. Surprisingly, excellent crystal data were accessed for GM 15–18, which exhibited slight or complete lack of disorder and no restraint had to be applied to the guests Table S29. AlthougThe high-quality crystal data above encouraged us to further explore the determination of the absolute configuration of chiral molecules using this method. SCXRD analysis can observe absolute configuration directly. However, it is still a challenging task. Low occupancy or disorder of the guests, insignificant anomalous scattering, and poor data quality can all possibly make it difficult for absolute configuration to be determined definitively. CTX[P(O)Ph], as an achiral host molecule, cannot distinguish enantiomers, and thus, it cannot crystallize selectively with trace impurity of the opposite chirality in a 99% optically pure sample.l-prolinate (GM 25) and R-styrene oxide (GM 26). All crystals existed in a triclinic or monoclinic crystal system. In each crystal structure, two or four independent guest molecules were in the minimal asymmetric unit and all these guest molecules exhibited the same chirality with limited restraints. Flack parameters close to 0 indicate an unambiguous assignment of absolute configuration, and a threshold of 0.1 is commonly used.11 For GM 19–22 and GM 25–26, the flack values calculated using Parsons' method were within the acceptable threshold for credible absolute configuration assignment.18 Inversion tests were carried out for GM 23–24 because their flack values were slightly larger than 0.1.11 Much higher flack values of the opposite chirality after inversion confirmed the correct chirality assignment Ph] enhanced the anomalous scattering effect when chiral guests were absorbed, which is highly important for absolute configuration assignment.To sum up in this section, characteristics, such as the anomalous scattering of phosphorus atoms, regularly ordered guest molecules, full occupancy, and no requirement for the masking of solvents, work together to achieve satisfactory flack values and contribute to credible absolute configuration determination.23 and hydrophilicity as possible key factors (3) and 3-bromo-4-chloroanisole (GM 13 with the largest molecular weight of 221.48 g mol−1). In addition, some smaller molecules, such as menthone and perillyl alcohol, could not crystallize with CTX[P(O)Ph] (Table S31P).24 Guest molecules with moderate hydrophilicity or polar functional groups tended to crystallize with the host. Once the hydrophobic part of the guest molecule was quite large, it preferentially remained in solution instead of being captured by the host. The most hydrophobic test molecule was 2,6-diisopropylaniline (GM 3) with a log P value of 3.18. This phenomenon was also consistent with the fact that CTX[P(O)Ph] could not solubilize in a non-polar oil sample under heating, not to mention crystallization. It should be noted that the success of clathrate crystallization is quite complicated and depends on many properties of the host and guest. Therefore, we could only draw a qualitative inference that very large and hydrophobic molecules probably could not be crystallized with CTX[P(O)Ph].With more and more guest molecules screened, it has been found that some of them could not crystallize with CTX[P(O)Ph], and the host-only crystal is obtained . What ar factors . As showTable S31, which w11In combination with the experimental process and crystal data discussed above, the crystallization mechanism was discussed to gain further insight into it. Because of the extremely rigid structure, CTX[P(O)Ph] could easily form high-quality crystals with the most oily samples after a “heating–cooling” process. In all cases reported here, crystal data could be collected successfully once. We did not encounter a situation in which a host-only crystal structure was obtained initially, and a clathrate crystal structure was achieved later. For example, three independent crystal cultivation and data collections were performed for GM 24 as a representative guest molecule. The crystal data provided similar results with the exact same guest-host ratio. These phenomena demonstrated that the clathrate crystals with CTX[P(O)Ph] were a thermodynamic product. Such thermodynamic stable crystals ensured experimental repeatability and avoided the difficult crystal-picking process that has been reported in the kinetic phenomenon of crystallization with 1,3,5,7-tetrakis  adamantane developed by the Richert group.25 It is important to understand why CTX[P(O)Ph] can act as a kind of host molecule to crystallize with various guests and arrange them in order. We suspected this phenomenon was associated with its unique structure. Apart from the extremely rigid skeleton, three converging P PBM data was replaced with SVG by xgml2pxml:<glyph-data id="z.dbd" format="PBM" resolution="300" x-size="8" y-size="10" xml:space="preserve">00000000000000000000000000000000111111110000000011111111000000000000000000000000</glyph-data><svg xmlns="http://www.w3.org/2000/svg" version="1.0" width="13.200000pt" height="16.000000pt" viewBox="0 0 13.200000 16.000000" preserveAspectRatio="xMidYMid meet"><metadata>Created by potrace 1.16, written by Peter Selinger 2001-2019</metadata><g transform="translate scale" fill="currentColor" stroke="none"><path d="M0 440 l0 -40 320 0 320 0 0 40 0 40 -320 0 -320 0 0 -40z M0 280 l0 -40 320 0 320 0 0 40 0 40 -320 0 -320 0 0 -40z"/></g></svg>O bonds were another feature of CTX[P(O)Ph]. The oxygen atoms on it provided hydrogen bond acceptors to recognize guest molecules. More importantly, they exhibited an electron-rich trend toward the center. The electrostatic potential (ESP) was calculated to understand the clathrate crystallization mechanism of CTX[P(O)Ph] Ph] also showed a negative potential of approximately −1 eV  when its polarity was too low to solvate the host. At this time, CTX[P(O)Ph] would be solvated by benzene rings of another host instead through C–H⋯O interactions in the crystal structure Ph] is a macrocycle, its cavity is too small and shallow to fully accommodate the whole organic molecules . The who[P(O)Ph]  and S31†27 In GM 19, the hydrogen bonds (1.870 and 1.980 Å) and C–H⋯O interactions (2.367 and 2.520 Å) worked together to anchor the guests above the cavity Ph] account for 34.0 and 44.1% of the noncovalent interactions between GM 19 and CTX[P(O)Ph] respectively. In GM 17, only C–H⋯O interactions (2.508 and 2.666 Å) were observed in the crystal structure (−1) and the absence of hydrogen bonds, the host-guest association was similar to the one above with the contributions of noncovalent interaction being 26.5 and 45.3% for PO bonds and the cavity of CTX[P(O)Ph] respectively. Therefore, the guest was forced to form an array in order with the host and its structure could be determined well Ph], GM 17@CTX[P(O)Ph] and GM 9@CTX[P(O)Ph] as examples. An independent gradient model based on the Hirshfeld partition (IGMH) was established to concretize the noncovalent interactions.e cavity . Their cTable S41. The IGMTable S41 clearly Table S41, three ctructure . Despitened well .−1). In addition, the small IGMH domains were mainly distributed between the toluene molecule and the side chain of CTX[P(O)Ph] , the space above the cavity of CTX[P(O)Ph] was occupied by the benzene ring of another CTX[P(O)Ph] molecule. Toluene molecules were on the side of CTX[P(O)Ph] and nearly no noncovalent interactions were found between them in the crystal structure , which c[P(O)Ph] . The conTable S32. Due to Table S32, it is oIn summary, clathrate crystals of CTX[P(O)Ph] with various oily guest molecules present an extremely rigid skeleton and thermodynamically stable product that guarantees the facile accessibility of high-quality single crystals. The negative electrostatic potential on the surface, which consists of three converging phosphorus oxygen double bonds and an electron-rich cavity, acted as a site to trap the guest above the cavity just like a host-guest system and orient the guest in a periodic way. This regularly ordered arrangement of guests allowed the observed electron density to closely match the real structure. Therefore, the guest could be refined with 100% occupancy and a few restraints. Solvent masking was not necessary in most cases. As a result, CTX[P(O)Ph] exhibited outstanding crystallization capacity with various oily samples for structure elucidation, including some compounds that pose challenges in determining the structure with NMR spectroscopy. The absolute configuration of the guests could also be defined well with the aid of CTX[P(O)Ph] in the crystal phase. More importantly, different from most multi-component crystallization in which obvious network and porous structures are used to accommodate and arrange the guest, the compounds proposed here are mainly driven by the interactions between the guest and the negative electrostatic potential surface of the host. This clathrate crystallization strategy also provides new ideas for host design for guest structure determination.General information, detailed crystal cultivation conditions, all X-ray crystallographic data, synthetic procedures of new compounds, and theoretical calculations are given in the ESI. CCDC 2251917 (for CTX[P(O)Ph]), 2251918 (for GM 1), 2251919 (for GM 2), 2251920 (for GM 3), 2251921 (for GM 4), 2251922 (for GM 5), 2251923 (for GM 6), 2251924 (for GM 7), 2251925 (for GM 8), 2251926 (for GM 9), 2251927 (for GM 10), 2251928 (for GM 11), 2251942 (for GM 12), 2251943 (for GM 13), 2251929 (for GM 14), 2251930 (for GM 15), 2251931 (for GM 16), 2251932 (for GM 17), 2251933 (for GM 18), 2251934 (for GM 19), 2251935 (for GM 20), 2251936 (for GM 21), 2251937 (for GM 22), 2251938 (for GM 23), 2251939 (for GM 24), 2251940 (for GM 25), 2251941 (for GM 26) contain the ESIJ. Jiao carried out the experimental work, synthesized the host molecules, cultivated all single crystals, solved most of the crystal structures, and conducted the theoretical calculations. Y. Zhao solved other crystal structures. H. Li and W. Xie collected all single crystal data. J. Jiao, C. Lin, and L. Wang co-wrote the paper. C. Lin, J. Jiang, and L. Wang supervised the investigation. All authors discussed the results and commented on the manuscript.There are no conflicts to declare.SC-014-D3SC02995F-s001SC-014-D3SC02995F-s002


Incorporating blast furnace slag into the composition of paving concrete can be one of the cost-effective ways to completely eliminate by-products from the pig iron production process (approximately 70% granulated slag and 30% air-cooled slag). The possibility to reintroduce blast furnace slag back into the life cycle will provide significant support to current environmental concerns and the clearance of tailings landfills. Especially in recent years, granulated and ground blast furnace slag (GGBS) as a substitute for cement and air-cooled blast furnace slag (ACBFS) aggregates as a substitute for natural aggregates in the composition of concretes have been studied by many researchers. But concrete compositions with large amounts of incorporated blast furnace slag affect the mechanical and durability properties through the interaction between the slag, cement and water depending on the curing times. This study focuses on identifying the optimal proportions of GGBS as a supplementary cementitious material (SCM) and ACBFS aggregates as a substitute to natural sand such that the performance at 90 days of curing the concrete is similar to that of the control concrete. In addition, to minimize the costs associated with grinding GGBS, the hydration activity index (HAI) of the GGBS, the surface morphology, and the mineral components were analyzed via X-ray diffraction, scanning electron microscopy (SEM), energy dispersive spectrometry (EDX), and nuclear magnetic resonance relaxometry (NMR). The flexural strength, the basic mechanical property of road concretes, increased from 28 to 90 days by 20.72% and 20.26% for the slag concrete but by 18.58% for the reference concrete. The composite with 15% GGBS and 25% ACBFS achieved results similar to the reference concrete at 90 days; therefore, they are considered optimal percentages to replace cement and natural sand in ecological pavement concretes. The HAI of the slag powder with a specific surface area equivalent to that of Portland cement fell into strength class 80 at the age of 28 days, but at the age of 90 days, the strength class was 100. The results of this research present three important benefits: the first is the protection of the environment through the recycling of two steel industry wastes that complies with European circular economy regulations, and the second is linked to the consequent savings in the disposal costs associated with wastefully occupied warehouses and the savings in slag grinding. Portland cement production requires a significant energy input that contributes to releasing a large amount of carbon dioxide into the atmosphere, about 7% of total global greenhouse gas emissions ,2. The cTherefore, efficient use of renewable and non-renewable raw materials is essential for economic development . MultiplWith the development of high-performance green concrete, GGBS has become an important auxiliary material in cement concrete, also known as the “sixth ingredient” of concrete . The widThe original contribution of this study lies in the detailed analysis of some concretes containing GGBS as supplementary cementitious material (SCM) together with this type of ACBFS as a fine aggregate in order to obtain an ecological and economical material without sacrificing mechanical performances or the durability of the obtained concrete. This work complements the current research, which is mainly concerned with the separate incorporation of GGBS or ACBFS into concrete compositions at 28 days of curing age.The results show the optimal percentages of substituting conventional materials with blast furnace slag whose performances at 90 days of age are similar to those of the control concrete. The HAI of the GGBS was evaluated, and the slag mortars’ microstructure was analyzed via X-ray diffraction, energy dispersive electron microscopy (SEM), and nuclear magnetic resonance (NMR) relaxometry ,33. In aThis research has significant implications for developing slag concrete for road paving. The extension of the reference tests from 28 to 90 days confirms the performance improvement, encouraging its use in the composition of road concretes with slag.The Portland cement -CEM I 42.5R supplied by Romcim Targu-Jiu, CRH Romania Company is defined according to SR EN 197-1 , and the24 determined according to SR EN 1097-6 [River sand and ACBFS in size (0/4) mm were used as fine aggregates according to SR EN 12620 . The oxiN 1097-6  on foundN 1097-6 . The quaN 1097-6  and accoN 1097-6  for crus2/kg and 330 m2/kg, called M II/360 and M III/330. For the specific surface area, the air permeability method (Blaine) was used on cement particles with GGBS below 63 µm in comparison to a reference material sample according to SR EN 196-6 [The amounts of material for the mortar production are listed in EN 196-6 . The 40 EN 196-6 , as seenThe material proportions of the poured concrete in this experiment are listed in 3, and the occluded air content was in the range (5.0 ÷ 6.5)%. The results of the fresh concrete were within the specified limit values, and the compressive strength (fc) already reached the minimum value of 50 MPa at the age of 7 days [The design parameters for the pavement concrete were set for class BcR 5.0, which corresponds to very heavy traffic, commissioning in the system with slip form according to the requirements specified in NE 014  and SR Ef 7 days , see TabGGBS) and the compressive strength of cement mortar (fcC).The hydration activity index (HAI) of GGBS was calculated with Equation (1) as the ratio between the compressive strength of 50:50 slag cement mortar  was performed for phase composition analysis and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM) (EDX) was performed for microstructure analysis. Fragments from the compression test on standard mortar (M I) and mortar with 50% GBS  up to the age of 90 days were examined.XRD patterns were performed on powder samples using a D8 Advance diffractometer  with CuK α1 anode (λ = 1.5418 Å), operating at 40 kV and 35 mA at room temperature. Conventional reference–intensity ratio (RIR) method  was used2 were mounted with carbon tape on an SEM stub.SEM-EDX analysis was performed at room temperature using a scanning electron microscope  with a Quantax EDX XFlash  detector. Samples of ~4 mm2 were extracted from the CPMG series using a numerical Laplace inversion [From intact prismatic samples prepared for standard mortar and mortar with 50% GGBS, a cylindrical sample with a length of 20 mm and a diameter of 9.5 mm was extracted to determine the relative pore size distribution with the NMR relaxometry technique . After dnversion ,55.A total of nine prisms measuring 150 × 150 × 600 mm were cast and left in air for 24 h. They were then preserved in water at a temperature of (20 ± 2) °C until they were 90 days old. According to SR EN 12390-5 , flexuraThe compressive strengths according to SR EN 12390-3  and the Mass loss due to exfoliating in the presence of de-icing agents (3% NaCl) after 56 freeze–thaw cycles according to SR CEN/TS 12390-9  was deteThe volume loss from wear according to SR EN 1338  Figure g and theThe freshly split fragments were sprayed with 1% phenolphthalein solution to determine the carbonation corrosion resistance in accordance with SR CR 12793 .The quality of the concrete was assessed according to the requirements indicated in 3), a 0.1 mol/dm3 (0.1 M) solution, to determine the penetration depth of chlorine (Xd) according to the NT BUILD 492 test [D) were then calculated with the Nernst–Planck Equation (2) [D—Migration coefficient in non-equilibrium state (×10−12 m2/s);V—Applied voltage (V);T—Mean value between initial and final temperature in the anolytic solution, (°C);L—Sample thickness (mm);Xd—Average chlorine penetration depth (mm).Chloride corrosion resistance was evaluated on cylindrical specimens 100 mm in diameter and 50 mm thick using the RPCT test according to ASTM C 1202  Figure . At the 492 test . Chlorintion (2) ,68:(2)D=The correlation between the past electrical charge Q and the penetrability of chlorine ions is presented in The compressive strengths of the standard mortar MI and the test mortars MII/360 and MIII/330 are shown in As can be seen, the highest increase in the compressive strengths from 28 to 90 days was 22.90% for the MIII/330 mortar and 13.62% for MII/360, respectively, while the increase for MI was 7.13%. In For quality control in the production of mortar/concrete samples, the standard deviation has been plotted in 2) as the main crystalline phase, accompanied by albite (NaAlSi3O8), orthoclase K(AlSi3O3), and traces of calcium silicate hydrate (CaH2O4Si). At the age of 90 days, the portlandite and ettringite, which are characteristic of early cement hydration, were not remarked [remarked .The results indicate that replacing cement with 50% GGBS increases the degree of crystallinity from 28 to 90 days, while the degree of crystallinity decreases for the standard mortar, on the degree of reaction of the binder . For theThe decrease in the degree of crystallinity from 28 to 90 days in the MI standard sample indicates a slowing down of the reaction rate of the binder and thus implicitly a slower development of the resistance structure. However, in the slag samples, the continuation of these reactions allows the resistance structure to develop after a longer curing time .The concentration of defects in the crystal structures and the relative solubility of the different minerals also influence the development of the mechanical strength .The XRD results correlate with the rate of increase in the mechanical strengths of the mortars, which is lower for the standard mortar and higher for the slag mortars over the period from 28 to 90 days. The higher increase in compressive strength at 90 days in the slag mortar is supported by an additional cementitious and pozzolanic reaction at a later age, which is influenced by the GGBS ,83,84.On the mortar samples, the SEM technique was used to characterize the structure and elemental composition on the surface of the examined samples. The images of the mortar samples M I, M II/360, and M III/330 aged 90 days  show thaLarger air voids at smaller spacings indicate a more porous surface, and conversely, small pore sizes at larger spacings indicate a more compact surface .At 90 days, the M I standard mortar sample a shows aEnergy-dispersive EDX spectroscopy was used to map the surfaces and identify the elemental composition of the samples previously studied via electron microscopy. The resulting images at 90 days are shown in For the three samples analyzed, the predominant elements at 28- and 90-days-old are Si and Ca. Aluminum was identified in the slag samples MII/360 and M III/330 due to the higher amounts of aluminum present in the GGBS compared to the Portland cement ,94. The In The morphology of the hydrated calcium silicate changes from weakly crystalline fibers to a reticular network . The preThe EDX results correlate with those of the XRD and show the continuation of the hydration–hydrolysis reactions and the development of a strength structure after longer curing times for the slag mortar.The development of the CPMG echo series in the case of the bare mortar samples and cyclohexane-saturated samples at 90 days is shown in A clearer interpretation of these results comes from the numerical Laplace transformation of the CPMG echo trains to reveal the distribution of the relaxation times ,55. Figu2 plotted on the horizontal axis are proportional to the relative pore size, and the values plotted on the vertical axis represent the probability density for a specific relaxation time and are expressed in arbitrary units (a.u.). The probability density indicates the probability with which a given relaxation time is present in the investigated sample. In The values for the transverse relaxation time T2. In the cyclohexane-saturated samples, in 2 compared to the standard sample.It can be seen in 2 relaxation times is similar. The NMR measurements show a lower capillary porosity in the slag samples compared to the standard sample. Fewer capillary pores reduce the damage to the cement stone structure caused by the freeze–thaw phenomenon [The area of Peak 3 corresponding to the capillary pores for the MIII/330 and MII/360 slag samples in enomenon ,102.The evolution of the flexural strengths at 90 days, the compressive strengths of the control kept in the thermostatic chamber, and the loss of compressive strength after 100 freeze–thaw cycles are shown in An increase in flexural strength from 28 to 90 days by 20.72% or 20.26% can be observed for the slag concrete and by 18.58% for the reference concrete a. In theIn The total exfoliated mass S at 56 freeze–thaw cycles, the wear volume loss, and the permeable pore content tested at 90 days of age showed higher performance values than at 28 days, 2, which corresponds to a very good resistance to exfoliation according to SS 13 72 44 [3/5000 mm2) [The cumulative value of the exfoliated mass of the slag samples is lower than that of the reference sample a; S56 is13 72 44 ,65. The 000 mm2)   ,104. The000 mm2) . The rea3). Compared to the reference concrete S0/0, a decrease of 11.14% was observed for sample S15/25 and a decrease of 6.77% for sample S15/50, which indicates a better resistance of the slag concretes to repeated freeze–thaw cycles with deicing agents.The average values of the electrical pass-through charges Q resulting from the rapid chlorine penetration test (RCPT) and the average penetration depth of the chlorine ions measured on three samples are shown in −12 (m2/s) by up to 7.39% (S15/50) compared to the reference concrete  at 90 days of the two composites S15/25 and S15/50 were at the same level or higher than the reference concrete value.The S15/25 composite achieved similar mechanical strengths and volume loss from wear as the reference concrete, but the values were lower for the S15/50 concrete.This study confirms optimum proportions for the S15/25 composite when the Portland cement replacement is 15% GGBS and natural sand is 25% ACBFS. In addition, the use of GGBS with a specific surface area equal to that of Portland cement results in environmentally friendly road concrete with low production costs.The hydration reactions of GGBS as a cement substitute continuate over a longer curing period, so the reference age of 90 days is the appropriate option. This experimental study responds to the desires of the circular economy, and the results can be successfully used to obtain ecological and economical road concretes.