Preparation of an Early Strengthening Agent for Concrete under Low-Temperature Conditions and Evaluation of Its Reaction Mechanism

Bao, Junwei,Ren, Qifang,Sun, Lei,Ding, Yi,Oh, Won-Chun Materials Research Society of Korea 2021 한국재료학회지 Vol.31 No.4

To solve the common problems of concrete preparation in low-temperature environments, calcium formate (C₂H₂O₄Ca), anhydrous sodium sulfate (Na₂SO₄), triethanolamine (C₆H₁₅O₃N), calcium bromide (CaBr₂), and triisopropanolamine (C₉H₂₁NO₃) are selected as early strength agents and mixed with C40 concrete in different dosages under low-temperature environments of 5 ℃ and 10 ℃ to develop a high-efficiency low-temperature compound early strength agent based on the effect of single-doped early strength agents. The effects of the compound early strength agent on the early strength of the concrete, the cement paste setting time, and cement fluidity at 5 ℃ and 10 ℃ are investigated, and the corresponding reaction mechanism is discussed from the perspective of micro-products. The best compound early strength agent ratio is found to be 2 % of calcium formate + 0.08 % of TEA (C₆H₁₅O₃N). The compound early strength agent effectively promotes the formation of hydration products, such as Ca(OH)₂ and C-S-H gel. In comparison with the control group, the strength of the concrete cured for 18 h, 1 d, 3 d, and 7 d under simulated natural conditions at 5 ℃ increases by 700 %, 540 %, 11.4 % and 10 %, respectively, whereas at 10 ℃, the corresponding values are 991 %, 400 %, 19.6 % and 11 %, respectively. The strength of the concrete at each age is close to the normal temperature standard of the curing strength. The addition of the compound early strength agent causes a reduction in cement fluidity and initial and final setting times, and also yields a good effect on the porosity of the early concrete.

Efficient degradation of imidacloprid in wastewater by a novel p-n heterogeneous Ag2O/BiVO4/diatomite composite under hydrogen peroxide

Jing Chen,Qifang Ren,Chunshan Xu,Bin Chen,Shaohua Chen,Yi Ding,Zhen Jin,Wanmi Guo,Xinyu Jia 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.123 No.-

In this study, Ag2O/BiVO4/diatomite composite with p-n heterojunction structure was synthesized bysimple hydrothermal method with diatomite as carrier. It was found that under the action of hydrogenperoxide (H2O2), the imidacloprid (IMD) could be effectively degraded by the composite. Systemic evaluationswas conducted on effects of pH value, catalyst dosage, H2O2 concentration, initial IMD concentration,and anion on how effeciently this new photocatalytic composite can degrade IMD. The results showthat the p-n heterojunction formed between the two contact surfaces of Ag2O nanoparticle and BiVO4promotes the charge transfer between the interfaces, inhibits recombination of electrons and holes,and thus significantly improves the catalytic performance. The stability and reusability of Ag2O/BiVO4/diatomite composites were tested with ICP experiment and cyclic experiment. Active substancecapture experiment and ESR reveal the photocatalytic reaction mechanism and confirm that superoxideradical (O2), hydroxyl radical (OH), and h+ can promote the degradation of IMD. The degradation productsand the intermediates of IMD were identified through LC-MS, on a basis of which the possible transformationpathway was proposed. In situ synthesis of p-type Ag2O and n-type BiVO4 heterojunctioncomposites has opened a new direction for photocatalytic degradation of organic pollutants.

3D Architectures of LaVO₄:Eu³⁺ Microcrystals via an EG-assisted Hydrothermal Method: Phase Selective Synthesis, Growth Mechanism and Luminescent Properties

Ding, Yi,Zhang, Bo,Ren, Qifang,Zhang, Qicai,Zha, Weiwei,Li, Xin,Chen, Shaohua,Oh, Won-Chun The Korean Ceramic Society 2017 한국세라믹학회지 Vol.54 No.2

In this article, pure $m-LaVO_4:Eu^{3+}$ and $t-LaVO_4:Eu^{3+}$ nanocrystals were prepared by an EG-assisted hydrothermal method with regular shapes. A series of controlled experiments showed that the pH value of a mixed solution, the volume ratio of $EG/H_2O$ and the dosage of the doped $Eu^{3+}$ all had an important effect on the sizes and shapes of the final products. Furthermore, the constitutional unit of the products changed from 0D to 2D with an increase in the EG dosage. The PL results showed that $t-LaVO_4$ doped with $Eu^{3+}$ ions had better luminescence properties than $m-LaVO_4$ due to its special structure. All of these results not only expand our understanding of the luminescence properties of lanthanide orthovanadates, but they also elucidate the principles of the crystal growth.

Microwave absorption and photocatalytic activity of MgxZn1−x ferrite/diatomite composites

Guo Wanmi,Wang Sulei,Ren Qifang,Jin Zhen,Ding Yi,Xiong Chun-Yu,Li Jinpeng,Chen Jing,Zhu Yuelei,오원춘 한국세라믹학회 2022 한국세라믹학회지 Vol.59 No.2

Mg x Zn 1−x ferrite/diatomite composites were synthesized by a two-step combination process (hydrothermal method and mechanical mixing method). The products were characterized by X-ray diff raction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR), UV–visible absorption spectrum (UV–Vis), X-ray photoelectron spectroscope (XPS), and microwave vector network analyzer. The photocatalytic results showed that the degradation rate of Rhodamine B (RhB) was 50–90% after 90 min of visible light. At 2–18 GHz frequency, when the Mg–Zn ratio increases to 0.8, the refl ection loss of a single MgxZn 1−x ferrite reaches − 7.23 dB at 8.75 GHz frequency in 3.5 mm thickness while the ratio is 0.2, the refl ection loss at 10.23 GHz reaches − 4.07 dB. The photocatalytic performance of Mgx Zn 1−x ferrite /diatomite composite for the degradation of RhB and its microwave absorption performance as absorbent are studied. The importance of developing new functional coatings to improve human environment is discussed.

Study on the Waterproofing Performance of FGD Gypsum Building Products from Inorganic-Organic Composite Additives

Ding, Yi,Fang, Youchun,Ren, Qifang,Fang, Hui,Zhang, Qicai,Oh, Won-Chun Materials Research Society of Korea 2015 한국재료학회지 Vol.25 No.11

In this article, poly methyl triethoxy silane was compounded with an inorganic waterproof admixture at a certain ratio to improve the performance of gypsum products; a new type of high-efficiency compound water-proofing additive was also investigated. Furthermore, the waterproof mechanism and the various properties on the hardened gypsum plaster were investigated in detail by XRD and SEM. The results show that the intenerate coefficient of gypsum plaster increased to more than 0.9; the water absorbing rate decreased to less than 10 %. Both the bending strength and the compressive strength of gypsum plaster increased by various degrees. The intenerate coefficient reached a maximum value of 0.73 and the strength of the samples showed almost no change when 5% cement alone was added. In this new type of the high-efficiency compound with waterproof additive, the optimal technological parameters for formulas were obtained to be: 5% cement, 18 % mineral powder, and 0.8% poly methyl triethoxy silane, to compound gypsum plaster. Meanwhile, the production of high performance gypsum as a building material has become possible.

Application Research on Mechanical Strength and Durability of Porous Basalt Concrete

Zhu, Yuelei,Li, Jingchun,Zhu, He,Jin, Long,Ren, Qifang,Ding, Yi,Li, Jinpeng,Sun, Qiqi,Wu, Zilong,Ma, Rui,Oh, Won-Chun Materials Research Society of Korea 2022 한국재료학회지 Vol.32 No.3

Porous basalt aggregate is commonly used in roadbed engineering, but its application in concrete has rarely been studied. This paper studies the application of porous basalt in concrete. Porous basalt aggregate is assessed for its effects on mechanical strength and durability of prepared C50 concrete; because it has a hole structure, porous basalt aggregate is known for its porosity, and porous basalt aggregates can be made full of water through changing the content of saturated basalt; after full-water condition is achieved in porous basalt aggregate mixture of C50 concrete, we discuss its mechanical properties and durability. The effects of C50 concrete prepared with basalt aggregate on the compressive strength, water absorption, and electric flux of concrete specimens of different ages were studied through experiments, and the effects of different replacement rates of saturated porous basalt aggregate on the properties of concrete were also studied. The results show that porous basalt aggregate can be prepared as C50 concrete. For early saturated porous basalt aggregate concrete, its compressive strength decreases with the increase of the replacement rate of saturated aggregate; this occurs up to concrete curing at 28 d, when the replacement rate of saturated basalt aggregate is greater than or equal to 40 %. The compressive strength of concrete increases with the increase of the replacement rate of saturated aggregate. The 28 d electric flux decreases with the increase of the replacement rate of saturated aggregate, indicating that saturated porous basalt aggregate can improve the chloride ion permeability resistance of concrete in later stages.