دانلود رایگان مقاله انگلیسی تاثیر پلیمر های اتیلن اکساید الکل بر کاهش جمع شدن خمیر سیمان - الزویر 2018

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عنوان فارسی

تاثیر پلیمر های اتیلن اکساید الکل بر کاهش جمع شدن خمیر سیمان

عنوان انگلیسی

Role of alcohol-ethylene oxide polymers on the reduction of shrinkage of cement paste

صفحات مقاله فارسی

0

صفحات مقاله انگلیسی

12

سال انتشار

2018

نشریه

الزویر - Elsevier

فرمت مقاله انگلیسی

PDF

نوع مقاله

ISI

نوع نگارش

مقالات پژوهشی (تحقیقاتی)

رفرنس

دارد

پایگاه

اسکوپوس

کد محصول

E8940

رشته های مرتبط با این مقاله

مهندسی عمران

گرایش های مرتبط با این مقاله

سازه

مجله

تحقیقات سیمان و بتن - Cement and Concrete Research

دانشگاه

Graduate School of Environmental Studies - Nagoya University - Japan

کلمات کلیدی

انقباض، C-S-H، مخلوط ، عامل کاهش دهنده انقباض

doi یا شناسه دیجیتال

https://doi.org/10.1016/j.cemconres.2018.05.017

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چکیده

ABSTRACT

Concrete drying shrinkage is a major practical problem, but it can be ameliorated by means of “shrinkagereducing agents” (SRAs). Water vapor sorption isotherms and low temperature DSC measurements suggest that alcohol-ethylene oxide polymers (AEOPs) with a better hydrophilic-lipophilic (HL-) balance are present in mesopores in which water molecules evaporate from 75% RH to 40% RH. Short-term drying shrinkage measurements show that the better HL-balanced AEOPs reduce irreversible shrinkage, which occurs mainly from 75% RH to 40% RH during the first drying. Based on the similarity between corresponding RH regions, it is concluded that the better HL balanced AEOP in relevant meso-pores hinders agglomeration of C-S-H during the first desorption to mitigate the irreversible shrinkage and reduce the first drying shrinkage.

نتیجه گیری

5. Conclusions

A series of alkyl-ethylene oxide polymers (AEOPs) synthesized with controlled variations of their main structural elements was investigated by a wide range of techniques to determine their effect on the drying behavior of well-hydrated white cement pastes. The following conclusions have been reached:

1) AEOPs can subtly change the shape of water vapor sorption isotherms, displacing the kink in the desorption branch from around 35% RH (for DEG) and 40% RH (for the plain paste) up to about 75% RH in the extreme case. Displacement of the kink to higher RH roughly correlates with a greater degree of shrinkage reduction, with an optimum at about 70% RH. This mechanism might be explained by the increase of critical vapor pressure due to the presence of better hydrophilic-lipophilic balance AEOPs in mesopores connecting to necking pores causing cavitation. This apparent optimal kink position corresponds with the use of the two most effective shrinkage-reducing AEOP molecules, C4-EO-2 and C8-EO-20, both of which gave only about half the drying shrinkage of the control paste. These molecules apparently have the best balance between the hydrophobic alkyl group and the hydrophilic poly-EO chain.

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