مدلسازی ترمودینامیکی حمله سولفاتی خمیر سیمان سخت‌شده حاوی سرباره و بررسی تاثیر محلول‌های سولفاتی مختلف

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانشیار دانشکده مهندسی عمران، دانشگاه تربیت دبیر شهید رجایی

2 دانشگاه تربیت دبیر شهید رجایی

چکیده

نفوذ یون‌های سولفات به داخل مواد سیمانی منجر به تشکیل فازهایی همچون گچ و اترینگایت می‌شود که انبساط و خرابی بتن را به دنبال دارند. در این مقاله از مدل‌سازی ترمودینامیکی، برای درک بهتر رفتار خمیر سیمان سخت شده طی حمله سولفات خارجی، استفاده‌شده است. این مدل بر اساس روش به حداقل رساندن انرژی آزاد گیبس می‌باشد. با کمک این مدل‌سازی علاوه بر بررسی نوع و حجم فازهای تشکیل‌شده طی حمله‌ی سولفاتی، عوامل تأثیرگذار بر آن همچون نوع و غلظت محلول‌های سولفاتی مختلف، شیمی سیمان، اثر سرباره و درصد بهینه جایگزینی آن موردمطالعه قرارگرفته است. نتایج مدل-سازی نشان می‌دهد که در میان محلول‌های سولفاتی، محلول سولفات منیزیم اثر خرابی بیشتری دارد؛ تجزیه ژل سیلیکاتی نیز که عمده مقاومت در نمونه را تأمین می‌نماید با توجه به میزان گچ و بروسیت تولیدی و همچنین حفظ تعادل برای بالا بردن pH، در این محلول بیشتر اتفاق می‌افتد. در مورد سرباره، جایگزینی زیر 40 درصد به علت افزایش فازهای مضر مانند منوسولفات و اترینگایت مطلوب نیست و در بالای 60 درصد جایگزینی عملکرد مناسبی از خود نشان داده است. به‌طور‌کلی نتایج حاصل از این مدل‌سازی با مطالعات و نتایج آزمایشگاهی که ریزساختار را بررسی نموده‌اند تطابق خوبی دارد.

کلیدواژه‌ها


عنوان مقاله [English]

Thermodynamic modeling of sulfate attack on hardened cement paste containing slag and investigation of the effect of various sulfate solutions

نویسندگان [English]

  • Amir Tarighat 1
  • yaghout modarres 2
1 Associate Professor, Faculty of Civil Engineering, Shahid Rajaee Teacher Training University
2 Shahid Rajaee Teacher Training University
چکیده [English]

Sulfate attack is a series of physico-chemical reactions between hardened cement paste and sulfate ions. Sulfate ion penetration into the hydrated cement results in the formation of voluminous and deleterious phases such as gypsum and ettringite which are believed to cause deterioration and expansion of concrete. However, there is no direct relationship between Ettringite or solids formation during sulfate attack and amount of expansion. Concrete deterioration due to sulfate attack depends on many parameters, however, in experimental studies, the implementation of the parameters and obtaining the results in a short time are too difficult. Therefore, the significance of theoretical and software modeling along with experimental studies, reducing the time and cost, increases insight of the obtained results. Thermodynamic modeling, in this paper, is employed according to the method of minimizing Gibbs free energy in order to have better understanding of the external sulfate attack on the cement paste; It is done by the GEM software which is able to calculate the stable phase as a function of reactants, temperature and pressure.
Type and volume of phases formed during the sulfate attack and factors affecting that such as sulfate solution with different concentrations were studied using the thermodynamical modeling. Hardened cement paste at 20 ° C and water-cement ratio of 0.5 were assumed in the modeling. Potassium/Sodium/Magnesium sulfates, among other sulfate solutions, with concentrations of 4, 44, 50, and 60 grams per litre were used. Since the slag systems generally exhibit appropriate behaviour in the high level of substitution, slag substitution up to 80 percent is examined. A replacement rate of slag lower than 40 percent, due to the increase of deleterious phases such as monosulfate and ettringite, is not optimum, however, the function of the slag replacement rate above 60% is satisfactory. According to the type and volume of formed products in sulfate solutions, we can conclude that magnesium sulfate solution has higher deterioration effect. Generally, the results correspond to existing studies agree with the experimental results.

کلیدواژه‌ها [English]

  • Sulfate attack
  • Modeling
  • Thermodynamic
  • Portland Cement
  • Slag

 

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