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Aggregate is the basic component of concrete, and its shape and surface properties largely determine the mechanical properties and durability of concrete. In order to further study the mesoscopic influence of aggregate shape on concrete interfacial phase, this study focuses on two aggregate shapes, circular and polygonal, and the elastic modulus and hardness of interfacial phase of specimens with different aggregate shapes were obtained by nano-indentation technology, and the mesoscopic component partition was quantified. Based on Gaussian statistical theory, the distribution model of nanomechanical properties of each phase was established, and the influence of aggregate shape on mechanical properties was studied by SEM test. The results show that (1) The width of the interfacial zone of natural rounded aggregate (∼50 μm) is slightly smaller than that of polygonal aggregate (∼60 μm), and the modulus of elasticity and hardness of the interfacial zone corresponding to the rounded aggregate (e.g., interfacial transition zone (E,H) ∼ (23.65 GPa, 0.9 GPa)) are larger than that of the interfacial zone of polygonal aggregate (interfacial transition zone (E,H) ∼ (21.66 GPa, 0.73 GPa)), indicating that the micromechanical properties of the interfacial zone of the circular aggregate are better than those of the polygonal aggregate; (2) The hydration products in the transition zone of the interface of different shapes of aggregates are almost the same, indicating that the influence of the shape of aggregates on the performance of concrete is mainly due to its own geometric characteristics. Based on the findings of the study, the direction of future research can focus on modeling with further refinement of the influence of aggregate shape parameters, such as shape factor and surface roughness, on the performance of concrete, so as to facilitate more accurate prediction and regulation of the performance of concrete. This study provides theoretical references for the design of aggregate proportioning and the simulation technology of fine data values in actual projects, and also provides theoretical basis and technical support for the standardization and performance evaluation of concrete materials.

Coal gangue is a byproduct of coal mining and processing, and according to incomplete statistics, China has amassed a substantial coal gangue stockpile exceeding 2600 large mountains, which poses a serious threat to the ecological environment. Utilizing gangue as a coarse aggregate to produce gangue concrete (GC) presents a promising avenue for addressing the disposal of coal gangue; however, gangue concrete presents several challenges that need to be tackled, such as low strength and poor resistance to repeated loads. In this study, polypropylene fibers (PPFs) were incorporated into gangue concrete to enhance its utilization rate. Uniaxial compressive and repeated loading experiments were then conducted to investigate the uniaxial strength and fatigue properties of polypropylene fiber-reinforced gangue concrete (PGC) with varying gangue substitution rates (20%, 40%, and 60%) and different polypropylene fiber admixtures (0, 0.1%, 0.2%, and 0.3%). The findings indicate that incorporating gangue at a substitution rate of 40% could notably enhance the uniaxial compressive strength of PGC, resulting in a maximum increase of 19.4%. In the repeated loading experiments, the ductility of PGC was enhanced with the incorporation of PPFs, resulting in a reduction of 33.76% in the damage factor and 19.42% in residual strain for PGC-40-0.2 compared to PGC-40-0. A PPF content of 0.2% was found to be optimal for enhancing the fatigue performance of PGC. Scanning electron microscope (SEM) testing proved the improvement effect of polypropylene fiber on gangue concrete from a microscopic perspective. This study provides crucial experimental data and a theoretical foundation for the utilization of gangue concrete in complex stress environments. [ABSTRACT FROM AUTHOR]

The newly filled slurry is generally insufficiently consolidated and thus differs from the natural structural soil generated by deposition in the microstructure. The initial microstructure is gradually formed by deposition and consolidation, which decreases the water content of the slurry, and the corresponding physical and mechanical properties evolve simultaneously. To investigate the changing regularity of the microstructure of the newly filled slurry during consolidation, scanning electron microscopy (SEM) is used to explore the link between the water content and the microstructure. The fractal dimension is also introduced into the quantitative analysis of the variation trend of the slurry microstructure. The results demonstrate that when the water content decreases, the fractal dimension of the solid phase increases while the fractal dimension of the void decreases, indicating that the more orderly the solid phase is, the smaller the void, and the stronger the structure of the slurry in the microstructure. Furthermore, the higher the water content is, the greater the variation in the slurry microstructure during consolidation. [ABSTRACT FROM AUTHOR]

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Copyright of Journal of Engineering Geology / Gongcheng Dizhi Xuebao is the property of Journal of Engineering Geology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Basalt fiber is a promising reinforcement agent for loess engineering. In this study, unconfined compressive tests facilitated with the digital image correlation (3D-DIC) method were carried out on basalt fiber–reinforced loess to obtain the deformation images and surface strain fields at different loading moments. The reinforcement mechanism of samples with different fiber contents and fiber lengths was interpreted from the microstructure obtained by scanning electron microscope (SEM). Results showed that the stress–strain curves of fiber-reinforced samples are all strain-softening. The curves of unconfined compressive strength (UCS) versus fiber length or fiber content manifest an overall inverted U-shaped pattern. The optimal reinforcement effect was observed at a fiber content of 0.6% and a fiber length of 12 mm. The failure strain, plasticity ratio, and energy absorption capacity of samples vary with fiber content or fiber length like that of the UCS. Fracture of unreinforced loess was noted, characterized by brittle failure, while the reinforced loess exhibits bulging failure with ductile characteristics. The surface strain field shows that the maximum axial strain varies with fiber content and fiber length in contrast to the strength. The deformation of the sample is more uniform under the optimal fiber condition, and the effect of fiber content is significantly greater than that of fiber length. SEM images indicate that the fibers are more uniformly distributed in the soil at lower fiber contents and smaller fiber lengths. Otherwise, significant entanglement or agglomeration will occur, resulting in the creation of weak surfaces in the soil. [ABSTRACT FROM AUTHOR]

Coal gangue is a byproduct of coal mining and processing, and according to incomplete statistics, China has amassed a substantial coal gangue stockpile exceeding 2600 large mountains, which poses a serious threat to the ecological environment. Utilizing gangue as a coarse aggregate to produce gangue concrete (GC) presents a promising avenue for addressing the disposal of coal gangue; however, gangue concrete presents several challenges that need to be tackled, such as low strength and poor resistance to repeated loads. In this study, polypropylene fibers (PPFs) were incorporated into gangue concrete to enhance its utilization rate. Uniaxial compressive and repeated loading experiments were then conducted to investigate the uniaxial strength and fatigue properties of polypropylene fiber-reinforced gangue concrete (PGC) with varying gangue substitution rates (20%, 40%, and 60%) and different polypropylene fiber admixtures (0, 0.1%, 0.2%, and 0.3%). The findings indicate that incorporating gangue at a substitution rate of 40% could notably enhance the uniaxial compressive strength of PGC, resulting in a maximum increase of 19.4%. In the repeated loading experiments, the ductility of PGC was enhanced with the incorporation of PPFs, resulting in a reduction of 33.76% in the damage factor and 19.42% in residual strain for PGC-40-0.2 compared to PGC-40-0. A PPF content of 0.2% was found to be optimal for enhancing the fatigue performance of PGC. Scanning electron microscope (SEM) testing proved the improvement effect of polypropylene fiber on gangue concrete from a microscopic perspective. This study provides crucial experimental data and a theoretical foundation for the utilization of gangue concrete in complex stress environments.

The precision and reliability of test findings are closely related to the uniformity of remolded loess samples. Although many methods to evaluate the uniformity of remolded loess have been proposed, they have not been widely accepted, due to the many defects. Therefore, it is necessary to explore the evaluation method and index of the uniformity of remolded loess samples in laboratory tests. In this paper, variations in shear strength and microscopic properties along the sample height were examined using the direct shear test and scanning electron microscopy (SEM) test. The feasibility and reliability of employing shear strength as an indicator to assess the uniformity of remolded loess samples were confirmed based on the test results. The results showed that the shear strength and shear strength parameters decreased from top to bottom along the sample height, and that the difference in the shear strength and shear strength parameters between the top and the bottom of remolded loess samples increased with the increase in the sample height. The variation tendency of the shear strength and shear strength parameters altered when the height–diameter (H/D) ratio exceeded 0.97. The SEM test results revealed that as the sample height increased, the disparity in microstructure and pore distribution in various portions of remolded loess samples became more apparent. The effect of sample height on the uniformity of remolded loess samples was mostly attributable to the variation in coating thickness and the content of clay particles on the surface of coarse particles, induced by a reduction in compactness from the top to the bottom of samples. The coefficient for evaluating the uniformity of the remolded loess sample was defined as the ratio of the shear strength at the top to that at the bottom of the remolded sample, and 0.8 was chosen as the threshold value. The shear strength reflected the uniformity of remolded loess samples as accurately as the microscopic test parameters. Furthermore, the direct shear test is the most classic and widely used laboratory test, with a low cost, easy accessibility, short test cycle, simple data processing and low environmental requirements, which provides another feasible method to evaluate the uniformity of remolded loess. [ABSTRACT FROM AUTHOR]

The freeze–thaw cycling damages the soil structure, and the shear performance of soil are degraded. A series of tests on lime–soil(L–S) and fiber–lime–soil(F–L–S), including freeze–thaw test, the triaxial compression test, nuclear magnetic resonance (NMR) test and scanning electron microscope (SEM) test, were completed. The test results showed that fiber reinforcement changed the stress–strain behavior and failure pattern of soil. The cohesion and internal friction angle of soil gradually decreased with the increase of freeze–thaw cycles (F–T cycles). The pore radius and porosity of soil increased, while the micro pore volume decreased, and the small pore volume, medium pore volume and large pore volume increased, and the large pore volume had a little variation after 10 F–T cycles. The number of pores of F–L–S was less than L–S, demonstrating that the addition of fiber helped to reduce the pore volume. The interweaved fibers limited the development and the connection of cracks. By means of the spatial restraint effect of fiber on the soil and the friction action between fiber and soil, the shear performances and freeze–thaw durability of F–L–S better were than that of L–S. • The shear performances and freeze–thaw durability of soil were improved because of adding fiber. • The microstructure of the same sample was tested under freeze–thaw cycles by NMR test. • The effect of fiber reinforcement under freeze–thaw cycling was evaluated by triaxial compression test, NMR and SEM tests. [ABSTRACT FROM AUTHOR]

• PGS has superior resistance to high temperatures and seawater intrusion. • Rheology improvement mechanism of PGS under high-temperature was revealed. • Viscosity increasing mechanisms of PGS in seawater slurries are analyzed. An eco-friendly and effective slurry additive is needed to prepare an appropriate slurry for submarine slurry shield tunneling to control favorable rheological behavior and infiltration characteristics under high temperature and seawater intrusion. In this study, the corn PGS was selected as an additive to alleviate the deterioration in the physical properties of slurries caused by high temperature and seawater intrusion. The effects of different high-temperature environments and seawater intrusion rates on the deterioration of the slurry rheological properties and the variations in slurry flow patterns after adding different proportions of PGS were investigated via a series of experiments on slurry mixing proportions. In addition, the rheological improvement mechanism of PGS under a high-temperature environment and seawater intrusion was revealed respectively, and the morphology of the seawater slurry with PGS was observed via SEM tests. The results indicated that there is a remarkable rising-temperature thinning characteristics of Na-bentonite slurry when the temperature increases from 25 ℃ (room temperature) to 75 ℃, but the variation in temperature hardly changes the flow pattern of the seawater slurries. Compared to the seawater slurry with CMC, more than 0.2% PGS additive can alleviate the thinning phenomenon of seawater slurry caused by high temperatures rise and improve the viscosity of Na-bentonite slurries under seawater intrusion more effectively, which has superior resistance to high temperatures and seawater intrusion during the seabed slurry shield tunneling. The findings of this study could provide references for the preparation and selection of slurries used in submarine slurry shields in the future. [ABSTRACT FROM AUTHOR]

The arch expansion of cement stabilised base materials has become increasingly serious due to the current design guideline, typical climate and geological environment in the west of China. This research systematically investigated the influence of different factors on temperature expansion and also salt expansion of the cement stabilised base course through laboratory-scale slab tests and microscopic tests. Optimised gradation type of aggregate and other design indexes were proposed. The radial basis function network (RBFN) was used to establish a predication model of the amount of arch expansion. The micro-mechanism of arch expansion was further detailed by scanning images. The test results showed that the temperature expansion occurred most significantly during 20°C to 40°C and the optimised gradation could alleviate the arch expansion effectively. In the range of 20°C to 30°C, the arch expansion of cement stabilised materials was dominated by temperature expansion, and the expansion was mainly salt expansion between −10°C and 0°C. It is suggested that reasonable prevention measures should be taken considering different environmental factors by the inhibition weight 1/di, and thus the most effective preventing methods of arch expansion would be taken. [ABSTRACT FROM AUTHOR]

In expansive soil regions, engineering geological disasters frequently occur in wet–dry (WD) environments, which are inseparable from the degradation of soil shear strength and structural damage. This study attempts to assess the underlying mechanisms of shear strength degradation and micro- and mesoscale damage to expansive soil under WD cycles. Recompacted specimens were subjected to several WD cycles, then triaxial shear, nuclear magnetic resonance, and scanning electron microscopy tests were performed. Moreover, the influence of the WD cycles on the shear strength of expansive soil was evaluated. The state-of-the-art image processing and analysis techniques were combined to quantitatively investigate the evolution of the soil micro- and mesostructural characteristics. The results reveal that the deterioration of soil shear strength is primarily embodied in the initial 3 WD cycles, and is mainly due to the severe loss of cohesion (about 51.69%) during this period. Soil meso-cracks were formed under the combined effects of swelling potential and tensile stress, which mainly occurred in three stages: initiation stage (1–2 cycles); propagation stage (3–4 cycles); equilibrium stable stage (5–6 cycles). Indeed, the strength and average width of cracks were increased to varying degrees, which degraded the structural integrity of the soil. In addition, the microstructure of the soil was deeply affected by WD cycles; the total volume of pores increased significantly, the particles roundness decreased marginally, and an isotropic particles orientation was achieved as a whole with local preferential orientation (depolarization). The deterioration of shear strength of the expansive soil may be attributed to alterations in humidity, which causes the clay minerals in the soil to swell and shrink repeatedly, thereby yielding the irreversible fatigue damage of microstructure and propagation of meso-cracks. This work sheds light on the properties of shear strength evolution and mechanisms of structural damage in expansive soils in semi-arid regions. [ABSTRACT FROM AUTHOR]

The bypass of subway tunnels in soft soil areas is usually constructed by the artificial freezing method due to the waterproof property and high strength of frozen soil. The thawing settlement and deformation of silty clay under subway vibration loading is becoming a major issue. The Shanghai subway lines cross vertically and horizontally, of which the deepest station reaches 33.1 m. With the rapid development and utilization of underground space, the depth of subway excavation will become increasingly deeper. Under subway vibration loading, the dynamic characteristics and microstructures of deep clay should be investigated. In this paper, a series of scanning electron microscopy (SEM) tests and mercury intrusion porosimetry (MIP) tests were carried out to study the microscopic parameters of deep silty clay subjected to two freezing–thawing cycles under cyclic loading. The freezing–thawing soil produced higher axial strain than that of the unfrozen soil with the same loading. After freeze–thaw cycling, the soil particles show the phenomenon of agglomeration. As the pore diameter increases, the pore shape coefficient decreases gradually from 0.45 to 0.85. Under similar vibration loading, the anisotropy of the frozen–thawed clay increases as the freezing temperature decreases. The fractal dimension obtained by SEM tests is between 1.25 and 1.33. There is an approximate linear relationship between the axial strain and the fractal dimension. In MIP tests, there exists a bottleneck effect in the process of mercury intrusion. The pore volume and pore diameter of the freezing–thawing soil increase with decreasing freezing temperatures and freezing–thawing cycles, respectively. The thermal fractal model is applicable to the fractal characteristics of silty clay. The results can provide a reference for the design and construction of deep-buried subway tunnels in soft soil areas. [ABSTRACT FROM AUTHOR]

The precision and reliability of test findings are closely related to the uniformity of remolded loess samples. Although many methods to evaluate the uniformity of remolded loess have been proposed, they have not been widely accepted, due to the many defects. Therefore, it is necessary to explore the evaluation method and index of the uniformity of remolded loess samples in laboratory tests. In this paper, variations in shear strength and microscopic properties along the sample height were examined using the direct shear test and scanning electron microscopy (SEM) test. The feasibility and reliability of employing shear strength as an indicator to assess the uniformity of remolded loess samples were confirmed based on the test results. The results showed that the shear strength and shear strength parameters decreased from top to bottom along the sample height, and that the difference in the shear strength and shear strength parameters between the top and the bottom of remolded loess samples increased with the increase in the sample height. The variation tendency of the shear strength and shear strength parameters altered when the height–diameter (H/D) ratio exceeded 0.97. The SEM test results revealed that as the sample height increased, the disparity in microstructure and pore distribution in various portions of remolded loess samples became more apparent. The effect of sample height on the uniformity of remolded loess samples was mostly attributable to the variation in coating thickness and the content of clay particles on the surface of coarse particles, induced by a reduction in compactness from the top to the bottom of samples. The coefficient for evaluating the uniformity of the remolded loess sample was defined as the ratio of the shear strength at the top to that at the bottom of the remolded sample, and 0.8 was chosen as the threshold value. The shear strength reflected the uniformity of remolded loess samples as accurately as the microscopic test parameters. Furthermore, the direct shear test is the most classic and widely used laboratory test, with a low cost, easy accessibility, short test cycle, simple data processing and low environmental requirements, which provides another feasible method to evaluate the uniformity of remolded loess.

Because of its good stability, high strength and low permeability, granite is considered as an ideal surrounding rock for geological disposal of high-level radioactive waste, which is also the main candidate surrounding rock for high-level radioactive waste disposal project in China. Rock mechanics is one of the important problems for site selection, design, construction and operation of geological repository. It is of great theoretical and practical value to study the failure law of rock from the microcosmic aspect, to link the microcosmic failure morphology characteristics with the mechanical mechanism of rock macro fracture failure, and finally to establish a bridge between microcosmic failure mechanism and macro fracture analysis of rock. We carried out uniaxial compression test, triaxial compression test under different confining pressures, Brazilian splitting test and direct tensile test for the deep granite from the core of No. BS28 hole in Beishan area with depth of 560–680 m. SEM and EDS was carried out for the fracture surface under different test conditions. The macro and micro failure characteristics of granite under different test conditions are analyzed: It is basically the splitting failure phenomenon dominated by tensile failure after the uniaxial compression test, while the failure of the triaxial test specimen are basically all form a large inclined failure surface which show the shear failure phenomenon. It shows obvious brittle tensile failure under direct tensile test, while not simply tensile failure under Brazil split test. The micro structure and mineral composition of rocks are closely related to their macro mechanical properties. Due to the existence of other impurities, Beishan granite has a certain degree of discreteness, and because of the different composition, its fracture presents different forms. These studies provide the necessary basis for the design and construction of the geological disposal of high-level radioactive waste. [ABSTRACT FROM AUTHOR]

Geopolymer concrete as a green concrete has attracted great attention among scientists to reduce cement consumption and emissions. This study examines the use of recycled aggregates in geopolymer concrete as a substitute for coarse aggregates. To assess the mechanical performance, compressive strength, tensile strength, and flexural strength were measured for 20 mixing designs and their relationships with suitable convergence were obtained. The scanning electron microscope (SEM) images taken from the samples made with the highest and lowest resistance showed that the formation of hardened geopolymer gel depends on the concentration of chemical solutions. The results of the freezing and thawing cycle and mass loss of samples showed that the compressive strength of the geopolymer concrete had not decreased significantly and had a good durability in these conditions. [ABSTRACT FROM AUTHOR]

To study the effect of carbon nanofibers on the durability of concrete, the freeze-thaw cycle test, penetration test and carbonization test of carbon nanofiber reinforced concrete with carbon nanofibers with different volume (0.1%, 0.2%, 0.3%, 0.4%, 0.5%) were carried out. In addition, the microscopic modification mechanism of carbon nanofibers to concrete durability was further investigated by SEM test. The results show that the carbon nanofibers could improve the micro-morphology of concrete through fiber bridging and pore filling, significantly improving the durability of concrete. When the content of carbon nanofibers was 0.3%, the frost resistance, impermeability and anti-carbonization performance of carbon nanofiber reinforced concrete were the best. When the number of freeze-thaw cycles was the same, as the amount of carbon nanofibers increased, the mass loss rate and compressive strength loss rate of concrete decreased first and then increased. The seepage height and relative permeability coefficient of concrete decreased first and then increased with the increase content of carbon nanofibers. Under the same carbonization age, the carbonation depth of concrete decreased first and then increased with the increase content of carbon nanofiber. Frost resistance, impermeability and anti-car bonization performance of carbon nanofiber reinforced concrete with 0.5% of carbon nanofibers were still better than that of plain concrete. [ABSTRACT FROM AUTHOR]

Abstract Normal braces have a high stiffness but are buckling under compressive strength and have very low ductility. To overcome these disadvantages in recent years, a buckling restrained braces system has been used. In this study the optimal percentage of Microstructure, Polypropylene and Hybrid Fibers were determined by using tensile and compressive test, the results exhibited that the highest rate of tensile and compressive strength were occurred in the case of reinforced concrete with polypropylene fibers and the composition of polypropylene and metal fibers as known hybrid fibers compared to the non-fibrous concrete for test specimens containing (0.15–0.3) percent polypropylene fiber and reinforced concrete with the composition of polypropylene and sinusoidal fibers related to test specimens containing (1.5%) metal fibers. Also, the results of scanning electron microscope imaging of concrete core sheaths obtained from fiber concrete in this study showed that fibers play a micro role in concrete. In addition, this research the effect of using optimum amount of fibers in the concrete sheaths in the buckling restrained braces were investigated. For this purpose, 6 samples of buckling restrained braces were made and examined in three modes. Concrete sheaths of buckling restrained braces without fibers, with polypropylene fibers and composition of polypropylene and sinusoidal metal fibers were the three modes. The samples made were then shifted to the intended location and installed in the laboratory under the loading protocol of BD/SAC – 02/97, also by applying the horizontal displacement contained in this protocol, the applied load and the amount of related peripheral displacement were calculated. Backbone, loading cycle-force, horizontal displacement – lateral displacement, push over curve and bilinear behavior model were finally drawn. By examining the results, it is shown that the maximum number of loading cycles, the coefficient of ductility, the energy absorption, and the maximum amount of applied force in the specimen produced by the composition of polypropylene and sinusoidal metal fibers are accrued. [ABSTRACT FROM AUTHOR]

This paper reports the results of an experimental study on fire protection performance of intumescent coatings exposed to three non-standard fire curves. Intumescent coatings were applied to steel plates to make test specimens and, in total, furnace tests were performed on 36 specimens. The effective thermal conductivities of the intumescent coatings were calculated based on the measured steel and furnace temperatures. Scanning electron microscopy (SEM) tests were conducted to give some information on the difference in inner structure of intumescent char. Results of the experimental studies reveal that the fire protection performance of intumescent coating is highly dependent on the heating rate and maximum temperature of the fire condition. Different pore structures of the intumescent chars were obtained when intumescent coatings were subjected to fires with varied heating rates. The reaction steps of intumescent coating underwent depended on the maximum temperature of the fire condition. The consequence of this is changed expansion ratio and inner structure of intumescent char and then different effective thermal conductivity. When subjected to non-standard fire I, the reaction process of intumescent coating was incomplete and no 'honeycomb' pore structure was observed; in comparison, the coating underwent complete reaction process and compact 'honeycomb' pore structure was obtained when exposed to non-standard fire III; the maximum difference for representative values of effective thermal conductivities was up to 48.8%. In addition, due to the peculiar flame retardant mechanism of the intumescent coating, increasing the coating thickness does not always yield insulating property benefit. [ABSTRACT FROM AUTHOR]

SEM tests were conducted on four kinds of typical deep rocks in Meilinmiao Mine, and the micro properties were analyzed. The particles of gritstone are unbroken and particle diameter ranges from 80 μm to 400 μm, and the void between particles is wide. The macroscopic failure of gritstone is caused by breakage of the dung distributed between particles, and potassium feldspars contained in gritstone are not leached. The failure of medium sandstone is caused by micro cracks distributed in sandstone particles, and potassium feldspars are leached seriously, so the pores penetrate each other and there is close hydraulic connection in medium sandstone. The particles of fine sandstone are broken, and the particle diameters range from 60 μm to 300 μm, which determines the pores have good connectivity between particles. The dolomites contained in fine sandstone are corroded, and the micro fracture form belongs to inter-granular fracture. There are no particles and blocks in microstructure of sandy mudstone, but there are diverse micro cracks. The failure of mudstone arises from the extension of micro cracks, and the microstructure is different from the other three kinds of sandstones obviously. [ABSTRACT FROM AUTHOR]

• X-CT was used to investigate steel corrosion and corrosion-induced cracks in MOCC. • Corrosion was generated by using an improved galvanostatic accelerated test. • ITZs plays a guiding role in the formation of corrosion-induced cracks. We investigated corrosion-induced crack formation of magnesium oxychloride cement concrete (MOCC) in saline soil. Accelerated corrosion of steel in MOCC occurred through an improved galvanostatic accelerated test. X-ray computed tomography, used to scan the MOCC after curing for 14 days, revealed surface cracks of 0.11 mm, 0.25 mm, and 0.44 mm. Steel corrosion, corrosion distribution and corrosion-induced cracks were investigated, using scanning electron microscope (SEM) study the interface transition zone of MOCC. Results show a good linear relationship between steel volume loss and an increase in crack width; a good exponential relationship between an increase in corrosion-induced crack volume and an increase in crack width; and a good exponential relationship between steel volume loss and an increase in the volume of corrosion products. Corrosion-induced cracks do not necessarily form in the direction of the corrosion distribution. The product of the interfacial transitional zones (ITZs) is needle-shaped, which causes the formation of a weak surface in the ITZs so that corrosion-induced cracks usually develop along those zones. [ABSTRACT FROM AUTHOR]