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Guojun Ke,Wengui Li,Ruyi Li,Yuelin Li,George Wang 한국콘크리트학회 2018 International Journal of Concrete Structures and M Vol.12 No.7
The effects of different contents and particle sizes of waste glass powder on alkali–silica reaction (ASR) expansion of cementitious composite bar were investigated in this study. Waste glass powder with particle size less than 300 ㎛ exhibits an excellent mitigation effect on ASR expansion. With larger content and smaller particle size, the mitigation effect of waste glass powder on ASR expansion gradually increases. The mitigation effect of waste glass powder with particle size ranging from 38 to 53 ㎛ and 20% by weight of cement seems relatively better than that of fly ash. When the waste glass powder content reaches 30%, the mitigation effect is still effective and almost the same as that of fly ash. However, the waste glass powder with particle size larger than 300 ㎛ presents negative mitigation effect on ASR expansion when the replacement rate is larger than 30%. On the other hand, the waste glass powder and calcium hydroxide (CH) further react, and produce more calcium–silicate–hydrate gels, which apparently reduce the amount of CH. Moreover, the increasing content of waste glass powder results in a lower pH value in the pore solution of cementitious composite.
Guojun Pan,Ke Yang,Yantao Ma,Xia Zhao,Kui Lu,Peng Yu 대한화학회 2015 Bulletin of the Korean Chemical Society Vol.36 No.5
C-6 and C-8 monobromo flavonoids are important building blocks for the synthesis of flavonoid natural products and their derivatives. Bromination of suitably alkylated flavonoids with N-bromosuccinimide in dichloromethane (DCM), followed by deprotection with BCl3, gives either a C-6 or a C-8 monobromo flavonoid in high yield and with high regioselectivity, depending on the protection pattern of the C-5 and C-7 OH groups. The mild and neutral conditions are particularly useful for the regioselective bromination of acid-labile substrates.