مروری بر مکانیزمهای عملکرد فوقروانکنندههای پلیکربوکسیلاتاتر در رفتار رئولوژیکی و فرایند هیدراتاسیون سیمان
محورهای موضوعی : پلیمرها در انرژی و کاربردهای بهداشتی و محیطی
عاطفه نژادابراهیم
1
*
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محسن نجفی
2
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محمدحسین باقری
3
1 - دانشگاه صنعتی قم
2 - عضو هیئت علمی گروه مهندسی پلیمر دانشگاه صنعتی قم
3 - دانشگاه صنعتی قم
کلید واژه: فوقروانکنندههای پلیکربوکسیلاتاتری, کاهش آب, بتن, رئولوژی, حفظ اسلامپ, ساختار شیمیایی,
چکیده مقاله :
فوقروانکنندههای پلیکربوکسیلاتاتری بهعنوان نسل پیشرفتهای از افزودنیهای شیمیایی بتن، نقش بسیار مهمی در بهبود ویژگیهای رئولوژیکی، افزایش سیالیت، کاهش نسبت آب به سیمان و در نهایت ارتقای مقاومت مکانیکی و دوام بتن دارند. طی سالهای اخیر، استفاده از این ترکیبات به دلیل امکان کنترل دقیق ساختار مولکولی و تنظیم خواص عملکردی، رشد قابلتوجهی داشته است. مطالعات متعدد نشان دادهاند که عملکرد این فوقروانکنندهها به عواملی همچون نوع مونومرهای مورد استفاده، نسبت آنها، وزن مولکولی نهایی، طول و چگالی زنجیرههای جانبی و شرایط واکنش وابسته است. در این مقاله، پیشرفتهای اخیر در زمینه طراحی و سنتز این پلیمرها، تأثیر آنها بر ویژگیهای فیزیکی، شیمیایی و رئولوژیکی سیستمهای سیمانی و نقششان در فرایند هیدراتاسیون مورد بررسی جامع قرار گرفته است. از مهمترین مکانیسمهای عملکرد این مواد میتوان به دافعه الکترواستاتیکی، ممانعت فضایی، تخلیه فشاری، افزایش ترشوندگی و پراکندگی یکنواخت ذرات سیمان اشاره کرد. حضور گروههای عاملی نظیر کربوکسیلات و زنجیرههای پلیاتری در ساختار پلیمر باعث ایجاد تعادل بهینه میان جذب سطحی و پایداری پراکندگی میشود. همچنین، تغییر در طول و چگالی زنجیرههای جانبی، تنظیم توزیع وزن مولکولی، افزایش بار منفی و بهبود سازگاری با انواع سیمان از مهمترین روشهای ارتقای عملکرد این افزودنیها محسوب میشود. در مجموع، درک ارتباط بین ساختار شیمیایی و رفتار رئولوژیکی بتن، راه را برای توسعه افزودنیهای کارآمدتر و پایدارتر هموار میکند.
polycarboxylate ether (PCE) superplasticizers, as the advanced generation of chemical admixtures for concrete, play a crucial role in improving rheological properties, enhancing fluidity, reducing the water-to-cement ratio, and ultimately increasing the mechanical strength and durability of concrete. In recent years, the use of these compounds has grown significantly due to the ability to precisely control their molecular structure and tailor their functional properties. Numerous studies have shown that the performance of PCE superplasticizers depends on factors such as the type and ratio of monomers used, final molecular weight, length and density of side chains, and reaction conditions.
This review provides a comprehensive discussion of recent advances in the design and synthesis of PCE polymers, their influence on the physical, chemical, and rheological characteristics of cementitious systems, and their role in the hydration process. The main mechanisms involved include electrostatic repulsion, steric hindrance, pressure release, enhanced wetting, and uniform dispersion of cement particles. The presence of functional groups such as carboxylates and polyether side chains in the polymer structure establishes an optimal balance between surface adsorption and dispersion stability. Moreover, modification of side-chain length and density, adjustment of molecular weight distribution, increased negative charge density, and improved compatibility with various types of cement are among the key strategies for enhancing their performance. Overall, understanding the relationship between chemical structure and rheological behavior paves the way for the development of more efficient and sustainable admixtures for next-generation concrete systems.
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