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Replacing cement with industrial by-products is an important way to achieve carbon neutrality in the cement industry. The purpose of this study is to evaluate the effect of eggshell powder on cement hydration properties, and to evaluate its feasibility as a substitute for cement. The substitution rates of eggshell powder are 0%, 7.5%, and 15%. Studying the heat of hydration and macroscopic properties can yield the following results. First: The cumulative heat of hydration based on each gram of cementitious material falls as the eggshell powder content rises. This is a result of the eggshell powder's diluting action. However, the cumulative heat of hydration per gram of cement rises due to the nucleation effect of the eggshell powder. Second: The compressive strengths of ES0, ES7.5, and ES15 samples at 28 days of age are 54.8, 43.4, and 35.5 MPa, respectively. Eggshell powder has a greater negative impact on the compressive strength. The effect of eggshell powder on the speed and intensity of ultrasonic waves has a similar trend. Third: As the eggshell powder content increases, the resistivity gradually decreases. In addition, we also characterize the microscopic properties of the slurry with added eggshell powder. X-ray Diffraction (XRD) shows that, as the age increases from 1 day to 28 days, hemicaboaluminate transforms into monocaboaluminate. As the content of the eggshell powder increases, FTIR analysis finds a slight decrease in the content of CSH. Similarly, thermogravimetric (TG) results also show a decrease in the production of calcium hydroxide. Although the additional nucleation effect of eggshell powder promotes cement hydration and generates more portlandite, it cannot offset the loss of portlandite caused by the decrease in cement. Last: A numerical hydration model is presented for cement–eggshell powder binary blends. The parameters of the hydration model are determined based on hydration heat normalized by cement mass. Moreover, the hydration heat until 28 days is calculated using the proposed model. The strength development of all specimens and all test ages can be expressed as an exponential function of hydration heat. [ABSTRACT FROM AUTHOR]

On September 12, 2016, an ML 5.8 earthquake occurred near Gyeongju City in the southeastern part of the Korean peninsula. Two representative major faults, the Yangsan Fault (YSF) and Ulsan Fault (USF), are close to the earthquake hypocenter. However, the actual location of the hypocenter was reported to be outside of these fault zones. To identify an earthquake-generating fault and analyze its precise mechanism, it is necessary to understand the deep geological structure of the fault system. In this study, an audio-magnetotelluric (AMT) survey was conducted to analyze the subsurface structure of the fault system and geological characteristics in the Gyeongju area of Korea. AMT data were acquired from 301 stations around the earthquake epicenter and processed using robust processing with the remote reference technique. Inversion profiles were designated as either parallel (N-S) or perpendicular (E-W) to the regional fault strikes. The geoelectrical structure was obtained using two-dimensional (2-D) inversions of the joint set of transverse electric (TE) and transverse magnetic (TM) modes. The vertical sections along the E-W and N-S profiles that passed through the epicenter distribution contain a low resistivity zone at a depth of 2–3 km. The horizontal section of the resistivity distribution confirms that a high resistivity zone is located around the epicenter distribution. In contrast, a low resistivity zone is located at the center of the epicenter distribution. The high resistivity zone is located in the Yucheon Group (pyroclastic rocks) and granites, which are located on the western part of the YSF. In contrast, the low resistivity zone was observed in the alluvium to the northwest. The Hayang Group (clastic sedimentary rocks) and granites are located between the YSF and USF, and the observed high resistivity zone is coincident with the location of the granites. Paleogene and Neogene sediments distributed on the eastern part of the USF contained low resistivity zones. Compared with a magnetic anomaly map, the pattern of the magnetic anomalies is similar to that of the resistivity. This indicates that the resistivity model presented in this study is consistent with the geological characteristics of the study area. [ABSTRACT FROM AUTHOR]

Blended cement is commonly used for producing sustainable concretes. This paper presents an experimental study and an optimization design of a low-CO2 quaternary binder containing calcined clay, slag, and limestone using the response surface method. First, a Box–Behnken design with three influencing factors and three levels was used for the combination design of the quaternary composite cement. The lower limit of the mineral admixtures was 0%. The upper limits of slag, calcined clay, and limestone powder were 30%, 20%, and 10%, respectively. The water-to-binder ratio (water/binder) was 0.5. Experimental works to examine workability and strength (at 3 and 28 days) were performed for the composite cement. The CO2 emissions were calculated considering binder compositions. A second-order polynomial regression was used to evaluate the experimental results. In addition, a low-CO2 optimization design was conducted for the composite cement using a composite desirability function. The objectives of the optimization design were the target 28-day strength (30, 35, 40, and 45 MPa), target workability (160 mm flow), and low CO2 emissions. The trends of the properties of optimal combinations were consistent with those in the test results. In summary, the proposed optimization design can be used for designing composite cement considering strength, workability, and ecological aspects. [ABSTRACT FROM AUTHOR]

Ni-rich ternary oxide cathode (LiNi0.8Co0.1Mn0.1O2, NCM) is highly promising candidate for lithium-ion batteries (LIBs) due to its relatively large specific capacity and high energy density. Nevertheless, intrinsic structural/chemical instability and unwanted side reactions on the surface during charge/discharge, leading to rapid capacity fading and inferior cycle performance, severely impeded its commercialization. Herein, we demonstrated an interfacial/surface dual modification strategy, one of the most important techniques for fabricating LiNi0.8Co0.1Mn0.1O2, NCM cathode materials via Li2SnO3 surface coating and Sn4+ gradient doping. The electrochemical results deliver that the Sn dual-modified NCM exhibits the highest discharge capacity of 86.5% at 6.0 C and superior initial discharge capacity of 177.8 mAh g−1. In addition, Sn-modified NCM811 cathode shows an improved reversible capacity of 144.9 mAh g−1 and excellent electrode kinetics after 200 cycles. The dual modification strategy proposes a novel approach that can accelerate commercialization by simultaneously alleviating the surface instability and bulk structural degradation of Ni-rich cathode materials for state-of-the-art LIBs. [ABSTRACT FROM AUTHOR]