بررسی ریزساختاری تأثیر فلز سنگین سرب بر زمان گیرش سیمان

نوع مقاله : پژوهشی اصیل (کامل)

نویسندگان
صدیقه قاسمی
پیمان همامی
جعفر کیوانی
گروه مهندسی عمران، دانشکده فنی و مهندسی، دانشگاه خوارزمی، تهران، ایران
10.22034/24.4.21
چکیده
آلاینده­های حاوی فلز سنگین سرب همواره از منابع اصلی آلودگی محیط‌زیست در طی دهه­های گذشته است. فعالیت­های انسانی و صنعتی به‌طور مستقیم یا غیرمستقیم باعث ورود مقادیر انبوهی از آلاینده­های مبتنی بر سرب به سطح خاک و آب زیرزمینی شده است. تکنیک تثبیت و جامد­سازی (S/S) توسط سیمان، با کاهش قابل‌توجه تحرک و حلالیت سرب در خاک، ابزار مؤثری برای تصفیه خاک­های آلوده به سرب است. از سوی دیگر آلاینده فلز سنگین سرب بر روی زمان گیرش سیمان تأثیرگذار است و زمان گیرش به طور مستقیم بر کارایی ترکیبات سیمان تأثیرگذار است. بر این اساس فهم اندرکنش سرب و سیمان حائز اهمیت است. در این راستا هدف پژوهش حاضر بررسی تأثیر فلز سنگین سرب بر زمان گیرش و اندرکنش ریزساختاری سرب و سیمان است. بدین منظور محلول نیترات سرب با غلظت­های kg/cmol-solid 500 و 250، 100، 50، 25، 10، 0 به سیمان افزوده شد. بررسی اثر فلز سنگین سرب بر فرایند هیدراتاسیون و زمان گیرش خمیر سیمان توسط آزمایش­های زمان گیرش، پراش پرتو ایکس (XRD) و تصاویر میکروسکوپ الکترونی روبشی (SEM) و میزان تراوش و آبشویی آلودگی (TCLP) مورد تجزیه‌وتحلیل آزمایشگاهی قرار گرفته است. بر اساس نتایج حاصل از پژوهش،‌ رسوب و کمپلکس شیمیایی فلز سنگین سرب به شکل Pb(OH)2 و Pb-C-S-H منجر به تعویق هیدراتاسیون سیمان و افزایش زمان گیرش اولیه و نهایی خمیر سیمان و تثبیت و جامد­سازی آلاینده فلز سنگین سرب شده است. با افزودن kg/cmol-solid 25 نیترات سرب زمان گیرش اولیه سیمان از 65 دقیقه به 155 دقیقه افزایش یافته است. نتایج ریز­ساختاری نشان داد سیمان در فرایند تثبیت و جامد­سازی (S/S) فلز سنگین سرب تا غلظت cmol/kg-solid 100 به خوبی عمل کرده و میزان آلاینده برای خاک در حد مجاز است.

کلیدواژه‌ها

موضوعات

عنوان مقاله English

Investigation of the Microstructural Impact of Heavy Metal Lead on Cement Setting Time

نویسندگان English

Sedigheh Ghasemi
PEYMAN HOMAMI
Jafar Keyvani
Department of Civil Engineering, Faculty of Engineering, Kharazmi University, Tehran. Iran.
چکیده English

Heavy metal pollutants containing lead have consistently been major sources of environmental contamination over the past decades. Human and industrial activities have directly or indirectly led to the introduction of substantial amounts of lead-based pollutants into soil and groundwater. The Solidification/Stabilization (S/S) technique using cement, by significantly reducing the mobility and solubility of lead in soil, serves as an effective tool for remediating lead-contaminated soils. Conversely, the heavy metal pollutant lead significantly affects the setting time of cement, and the setting time directly impacts the efficiency of cementitious compounds. Consequently, understanding the interaction between lead and cement is of paramount importance. In this regard, the present study aims to investigate the influence of the heavy metal lead on the setting time and microstructural interaction of lead and cement. To achieve this, lead nitrate solution with concentrations of 0, 10,25,50, 100, 250 and 500 kg/cmol-solid, was added to cement. The effect of lead on the hydration process and setting time of cement was examined through setting time tests, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) images, and leachability analysis (TCLP). According to the research results, the precipitation and chemical complexation of the heavy metal lead in the form of Pb(OH)2 and Pb-C-S-H delayed the cement hydration process, extended the initial and final setting times of cement paste, and immobilized and solidified lead pollution effectively. By adding 25 kg/cmol-solid lead nitrate, the initial setting time of cement increased from 65 minutes to 155 minutes. Microstructural results demonstrated that cement effectively interacted with heavy metal lead up to a concentration of 100 cmol/kg-solid during the Solidification/Stabilization (S/S) process, keeping pollutant levels within permissible limits for soil.

کلیدواژه‌ها English

Heavy Metal Lead
setting time
Solidification/Stabilization
Cement
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مهندسی عمران مدرس
دوره 24، شماره 4
مهر و آبان 1403
صفحه 21-34