بررسی مقاومت سطحی بتن خود متراکم تحت تاثیر جمع شدگی و سولفات منیزیم با به کارگیری آزمون "پیچش"

نوع مقاله : علمی - پژوهشی

نویسندگان

1 استاد، دانشکده فنی و مهندسی، دانشگاه بین المللی امام خمینی (ره)، قزوین، ایران

2 کارشناس ارشد، دانشگاه بین المللی امام خمینی (ره)، قزوین، ایران

3 دکتری سازه، دانشکده فنی و مهندسی، دانشگاه بین المللی امام خمینی (ره)، قزوین، ایران

چکیده

با توجه به اهمیت جمع شدگی در صنعت بتن، تحقیقات زیادی در ارتباط با این موضوع انجام شده است. از آنجا که بتن خود متراکم از روانی بسیاری برخوردار است، بسیاری بر این عقیده هستند که جمع شدگی بتن خود متراکم باید بیش از جمع شدگی بتن معمولی مورد توجه قرار گیرد. همچنین سولفات ها از عوامل شایع مخرب بتن در اکثر مناطق ایران به خصوص در مناطق جنوبی کشور که بتن در معرض آب دریا (حاوی ترکیبات سولفاتی) قرار دارد، می باشند. از آنجا که مقدار خشک شدگی در سطح یک قطعه بتنی با شدت بیشتری نسبت به اعماق آن اتفاق می افتد و دوام سازه بتنی، بستگی شدیدی به مقاومت و نفوذ پذیری لایه سطحی آن دارد، لذا در این مقاله از آزمون "پیچش" که در برابر تغییرات سطحی بتن، حساسیت خوبی از خود نشان می دهد، جهت بررسی تاثیر جمع شدگی و سولفات منیزیم بر مقاومت سطحی بتن های خود متراکم استفاده شده است. سپس تغییر طول نمونه ها به همراه افت وزنی آن ها ارائه گردید. در انتها نیز با به کارگیری آزمون "پیچش" تاثیر سولفات منیزیم و تغییر طول نمونه ها بر مقاومت سطحی مورد ارزیابی قرار گرفت. نتایج حاصله بیانگر این می باشد که در اثر جمع‌شدگی ناشی از خشک‌شدن، بتن معمولی در مقایسه با نمونه‌های خودمتراکم، کاهش بیشتری در مقاومت سطحی از خود نشان می‌دهد. کاهش مقاومت بتن معمولی در اثر جمع‌شدگی در حدود 4/18 درصد ‌شده است که این کاهش در مقایسه با نمونه بتن خودمتراکم با 45 درصد خاکستر بادی 34/1 برابر، در مقایسه با نمونه بتن خودمتراکم با 35 درصد خاکستر بادی 35/1 برابر و در مقایسه با نمونه بتن خودمتراکم با 25 درصد خاکستر بادی 37/1 برابر می‌باشد.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Evaluation of surface strength of self-compacting concrete under shrinkage and magnesium sulfate using "twist-off" method

نویسندگان [English]

  • Mahmood Naderi 1
  • mohamadreza nasiri 2
  • Ali Saberi Vaezaneh 3
1 Professor, Department of Civil Engineering, Engineering Faculty, Imam Khomeini International University, Qazvin, Iran
2 Master, Department of Civil Engineering, Imam Khomeini International University, Qazvin, Iran
3 Ph.D , Department of Civil Engineering, Imam Khomeini International University, Qazvin, Iran
چکیده [English]

Concerning the importance of shrinkage in the concrete industry, much research is being performed on this subject. Since the self-compacting concrete has high consistency, many researchers believe that the shrinkage of self-compacting concrete should be more attended than the shrinkage of plain concrete. Sulfates are among the common reasons for concrete destruction in most areas of Iran especially in the southern areas, where the concrete is subjected to seawater (which includes sulfate compounds). Since the amount of drying is higher in the surface of a concrete piece than its depth and the durability of the concrete structure highly depends on the strength and permeability of its surface layer, this paper applied a “Twist-off” test (which shows proper sensitivity against the surface change of concrete) to investigate the effect of shrinkage and magnesium sulfate on the surface strength of self-compacting concretes. Then, the change in the length of samples was presented together with their weight drop. In the end, by using the “Twist-off” test, the effect of magnesium sulfate and the length change of samples on the surface strength was evaluated. The results represent that the plain concrete, compared to the self-compacting ones, shows more reduction in the surface strength due to the effect of drying shrinkage. The reduction in strength of plain concrete is 18.4% by shrinkage that is 1.34 times of the self-compacting concrete with 45% fly ash, 1.35 times of the self-compacting concrete with 35% fly ash, and 1.37 times of the self-compacting concrete with 25% fly ash. For the self-compacting samples curing in magnesium sulfate solution, the 3-day and 7-day surface strengths were reduced by the increase of fly ash percentage, while the 28-day surface strength was increased.

کلیدواژه‌ها [English]

  • Shrinkage
  • SCC
  • Twist off
  • Sulfate
  • Surface Strength

مراجع

[1] C.I. Goodier, Development of self-compacting concrete, P. I. Civil Eng. Str. B 156 (4) (2003) 405–414.
[2] A. Leemann, P. Lura, R. Loser, Shrinkage and creep of SCC–The influence of paste volume and binder composition, Constr. Build. Mater. 25 (5) (2011) 2283–2289.
[3] Y. Dang, J. Qian, Y. Qu, L. Zhang, Z. Wang, D. Qiao, X. Jia, Curing cement concrete by using shrinkage reducing admixture and curing compound, Constr. Build. Mater. 48 (2013) 992–997.
[4] M.J. Oliveira, A.B. Ribeiro, F.G. Branco, Combined effect of expansive and shrinkage reducing admixtures to control autogenous shrinkage in selfcompacting concrete, Constr. Build. Mater. 52 (2014) 267–275.
[5] M. Naderi. “New Twist-Off Method for the Evaluation of In-Situ Strength of Concrete”, Journal of Testing and Evaluation/Citation, 35(6). (2005).
[6] A. Saberi Varzaneh, and M. Naderi. Determination of Compressive and Flexural Strengths of In-situ Pozzolanic Concrete Containing Polypropylene and Glass Fibers Using "Twist-off" Method. Modares Civil Engineering Journal (M.C.E.J). Vol.20, No.5, Oct. (2020).
[7] M. Naderi, A. Smaili, and A. Saberi Varzaneh. Assessment of the application "twist-off" method for determining the in situ compressive and flexural strengths in the fiber concrete. Journal of Structural and Construction Engineering (JSCE) Accepted paper. (2021).
[8] A. Saberi Varzaneh. and M. Naderi. Determination of Shrinkage, Tensile and Compressive Strength of Repair Mortars and Their Adhesion on the Concrete Substrate Using "Twist‑off" and "Pull‑off" Methods. Iranian Journal of Science and Technology, Transactions of Civil Engineering. Published online (2020).
[9] A. Saberi Varzaneh, and M. Naderi. Investigation of In-situ compressive strength of Fiber-Reinforced Mortar and the Effect of Fibers on the Adhesion of Mortar/Steel. Advanced design and manufacturing technology. Accepted (2021).
[10] A. Saberi Varzaneh, and M. Naderi. NUMERICAL AND EXPERIMENTAL STUDY OF SEMI-DESTRUCTIVE TESTS TO EVALUATE THE COMPRESSIVE AND FLEXURAL STRENGTH OF POLYMER-MODIFIED MORTARS AND THEIR ADHESION TO THE CONCRETE SUBSTRATE. Revista Română de Materiale / Romanian Journal of Materials, 50(4), (2020) 537 – 544.
[11] F.M. Kilinckale. The effect of MgSO4 and HCl solutions on the strength and durability of pozzolan cement mortars, Cem. Concr. Res. 27 (12) (1997) 1911–1918.
[12] J. Zelic, I. Radovanovic, D. Jozic, The effect of silica fume additions on the durability of Portland cement mortars exposed to magnesium sulfate attack, Mater. Technol. 41 (2) (2007) 91–94.
[13] G.G. Liu, J. Ming, X.W. Zhang, A.B. Ma, Study on the durability of concrete with mineral admixtures to sulfate attack by wet-dry cycle method, Adv. Mater. Res. 295–297 (2011) 165–169.
[14] N. Ghafoori, M. Najimi, H. Diawara, M.S. slam, Effects of class F fly ash on sulfate resistance of Type V Portland cement concretes under ontinuous and interrupted sulfate exposures, Constr. Build. Mater. 78 (2015) 85–91.
[15] G.G. Liu, J. Ming, X.W. Zhang, A.B. Ma, Study on the durability of concrete with mineral admixtures to sulfate attack by wet-dry cycle method, Adv. Mater. Res. 295–297 (2011) 165–169.
[16] Q. Nie, C. Zhou, X. Shu, Q. He, B. Huang, Chemical, mechanical, and durability properties of concrete with local mineral admixtures under sulfate environment in Northwest China, Materials 7 (5) (2014) 3772–3785.
[17] P.K. Acharya, S.K. Patro, Acid resistance, sulphate resistance and strength properties of concrete containing ferrochrome ash (FA) and lime, Constr. Build. Mater. 120 (2016) 241–250.
[18] L. Jiang, D. Niu, Study of deterioration of concrete exposed to different types of sulfate solutions under drying-wetting cycles, Constr. Build. Mater. 117 (2016) 88–98.
[19] A. Benli, M. Karatas, E. Gurses. Effect of sea water and MgSO4 solution on the mechanical properties and durability of self-compacting mortars with fly ash/silica fume. Construction and Building Materials 146 (2017) 464–474.
[20] K. Samimi, A. Shirzadi Javid. Magnesium Sulfate (MgSO4) Attack and Chloride Isothermal Effects on the Self‑consolidating Concrete Containing Metakaolin and Zeolite. Iranian Journal of Science and Technology, Transactions of Civil Engineering. (2020). https://doi.org/10.1007/s40996-020-00398-6.
[21] M. Maes, F. Mittermayr, N De Belie. The influence of sodium and magnesium sulfate on the penetration of chlorides in mortar. Mater Struct 50(2) (2017) 153.
[22] A. Neville. The confused world of sulfate attack on concrete. Cem Concr Res 34(8) (2004) 1275–1296.
[23] M. Santhanam. Studies on sulfate attack – mechanisms, test methods and modeling. PhD Dissertation Purdue University, West Lafayette, Indiana, USA. (2001).
[24] ASTM C136-01, “Standard Test Method for Sieve Analysis of Fine and Coarse Aggregates”, American Society for Testing and Materials, (2001).
[25] EFNARC, Specification and Guidelines for Self-Compacting Concrete. ISBN 0 9539733 4 4. (2002).
[26] ASTM C 426-70, Drying Shrinkage of Concrete Masonry Units, Section 4, Volume 04.05, ASTM Committee C-15 (2007).

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سابقه مقاله

  • تاریخ دریافت: 27 فروردین 1400
  • تاریخ بازنگری: 25 آبان 1400
  • تاریخ پذیرش: 27 آبان 1400

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