99超碰中文字幕在线观看-天天干天天日天天舔婷婷-我看操逼的好看的女人的-日本一二三四五区日韩精品

 文獻名： Effects of core-shell polycarboxylate superplasticizer on the fluidity and hydration behavior of cement paste

 

作者： Shengli Chen^a,b, Shenmei Sun^a, Xiaolong Chen^a, Kaihong Zhong^a, Qiang Shao^a, Haijun Xu^a, Jiangxiong Wei^b

a    Department of Building Materials, Guangzhou Institute of Building Science Co., Ltd., Guangzhou Municipal Construction Group Co., Ltd., Guangzhou, Guangdong 510440, People's Republic of China

b    School of Materials Science and Engineering, South China University of Technology, Guangzhou, Guangdong 510641, People’s Republic of China

 

摘要：Polycarboxylate superplasticizer nanomicelles (nano-PCEs) with a core-shell structure were prepared via aqueous emulsion copolymerization in one pot. The shells are constructed with hydrophilic segments of poly(acrylic acid)-co-poly(isobutenyl polyethenoxy ether) (PAA-co-PHPEG), offering the water-reducing performance and stability for nano-PCEs. The cores are self-assembled with hydrophobic segments of polystyrene-co-poly(hydroxyethyl acrylate) (PS-co-PHEA), endowing nano-PCEs with good loss resistant of fluidity for cement pastes. The chemical structure of nano-PCEs was verified by the nuclear magnetic resonance spectrum (1H NMR) and fourier transform infrared spectroscopy (FTIR), and the 16−48?nm diameter of nano-PCE nanomicelles was determined by dynamic laser scattering (DLS) and transmission electron microscopy (TEM). Compared with comb PCEs, the cement paste containing nano-PCEs exhibited better fluidity retention of three hours by mini-slump measurements, lower hydration heat and more delayed hydration heat evolution by isothermal calorimetry tests. Furthermore, the hydrolysis and adsorption behavior of nano-PCEs in alkaline cement pastes were deduced, and a working mechanism of nano-PCEs was theoretically explained. This new type of superplasticizer nanomicelles can be used as a long time rheology modifying agent in fresh cementitious systems.