بررسی تأثیر حجم کف روی پارامتر‌های نفوذ بتن کفی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشکده مهندسی عمران- دانشگاه صنعتی خواجه نصیرالدین طوسی

2 دانشجوی دکترا دانشکده مهندسی عمران دانشگاه صنعتی خواجه نصیرالدین طوسی

چکیده

در این پژوهش، تأثیر تخلخل ناشی از کف روی پارامتر‌های نفوذ بتن‌های کفی شامل جذب آب و نفوذ یون کلرید، بررسی شده است. پارامتر‌های نفوذ مخلوط‌های بتن کفی با نسبت آب به سیمان 0/5 و میزان کف 20، 35 و 50 درصد، تعیین و با مخلوط پایه فاقد کف در نسبت آب به سیمان برابر مقایسه شده است. همچنین پارامتر‌های نفوذ بتن کفی سازه‌ای با نسبت آب به سیمان 0/4 و حجم کف 20 درصد تعیین و با بتن معمولی با مقاومت برابر مقایسه شده ‌است. نتایج، بیانگر آن است که با افزایش تخلخل کفی، جذب آب و ضریب جذب موئینه کاهش یافته ولیکن ضریب انتشار یون کلرید افزایش می‌یابد. تناقض مشاهده شده، ناشی از نحوه محاسبه نتایج در آزمایش‌های جذب است که به‌ صورت حجم آب جذب ‌شده به‌ ازای حجم کل بتن می‌باشد. با محاسبه حجم آب به ‌ازای حجم خمیر سیمان که فاز نفوذ‌پذیر است، مشخص گردید که مقدار جذب آب با ادغام کف افزایش می‌یابد که مشابه با روند نتایج نفوذ یون کلرید است. افزودن 20، 35 و 50 درصد حجم کف به مخلوط پایه، باعث افزایش جذب آب فاز خمیر سیمان به ‌ترتیب برابر 12، 27 و 50 درصد و افزایش ضریب انتشار یون کلرید به‌ ترتیب برابر 18، 55 و 155 درصد گردید. بررسی ساختار منافذ کفی نشان داد که با افزایش حجم کف، قطر منافذ افزایش و بخشی از آن‌ها با هم ادغام می‌شوند. در عین‌ حال، بتن کفی سازه‌ای، عملکردی مشابه مخلوط پایه داشت و همچنین نسبت به بتن معمولی با مقاومت برابر، نفوذپذیری کمتری از خود نشان ‌داد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Investigation of foam volume on the penetration parameters of foamed concrete

نویسندگان [English]

  • Alireza Bagheri 1
  • Mohammad Mahdi Rastegar 2
1 ِDepartment of Civil Engineering K. N. Toosi university of Technology Tehran Iran
2 Department of civil engineering K. N. Toosi university of technology
چکیده [English]

In this study performance of mixes with w/c ratio of 0.5 and foam contents of 20, 35 and 50%, with regards to absorption, capillary absorption and chloride ingress, were determined and compared to those of a base mix with the same proportions but without foam incorporation. A structural grade foam concrete with w/c ratio of 0.4 and foam content of 20% was also considered together with a conventional concrete of equal strength level. The results show that foam incorporation results in decreased absorption and capillary absorption and increased chloride diffusion. The discrepancy is due to the presentation of absorption results on a total concrete volume basis. By considering these results on paste volume basis, which is the penetrable phase, absorption results show the same trend as the chloride diffusion results. Incorporation of 20, 35 and 50 percent foam into the base mix resulted in increases of 12, 27 and 50 percent in paste absorption and 18, 55 and 155 percent in chloride diffusion values, respectively. Increased foam volume resulted in larger and more connected air voids. Although foamed porosity has a negative effect on penetration characteristics, the structural grade foam concrete with its lower w/c ratio achieved similar levels of performance as the base mix and performed better than the conventional concrete of equal strength level.

کلیدواژه‌ها [English]

  • Foamed concrete
  • Water Absorption
  • capillary absorption
  • POROSITY
  • CHLORIDE DIFFUSION COEFFICIENT
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