بررسی اثر ناهمواری و انحراف از گونیایی قالب های مکعبی بر نتایج مقاومت فشاری بتن

نوع مقاله : مقاله پژوهشی

نویسندگان

1 کارشناس ارشد راه و ترابری، دانشگاه زنجان

2 استادیار مرکز تحقیقات راه، مسکن و شهرسازی

3 عضو هیئت مدیره شرکت فهاب بتن

4 بازرس انجمن بتن ایران

چکیده

یکی از عوامل تاثیرگذار بر نتایج آزمون تعیین مقاومت فشاری بتن که عموماً در پروژه‌های عمرانی و تحقیقاتی به آن توجه کافی نمی-شود، کیفیت قالب آزمونه‌ها است. در این تحقیق، تاثیر کیفیت شش نوع قالب مکعبی با ابعاد 150*150*150 میلی‌متر شامل دو نوع قالب فولادی و چهار نوع قالب پلاستیکی بر نتایج مقاومت فشاری بتن (در محدوده 17 تا 67 مگاپاسکال) شامل پانزده طرح مخلوط در سنین مختلف بررسی شد. مشاهده‌شد که اختلاف بین متوسط کمترین و بیشترین نتایج مقاومت فشاری برای قالب‌های مورد بررسی به طور متوسط به مقدار 18درصد بوده‌است که نشان‌می‌دهد کیفیت قالب آزمونه‌ها بر مقاومت فشاری بتن میتواند بسیار قابل‌توجه باشد. در این مقاله، به منظور کمی‌سازی کیفیت قالب‌های مورد بررسی، دو پارامتر انحراف از گونیایی قالب و ناهمواری قالب تعریف شد. با انجام برازش خطی از نتایج به‌دست‌آمده، رابطه‌ای تجربی با دقت بالا برای تخمین اثر این دو پارامتر قالب بر ضریب کاهش مقاومت فشاری بتن ارائه شد. این رابطه نشان میدهد که هرچه انحراف از گونیایی قالب و ناهمواری آن بیشتر شود، مقدار ضریب کاهنده تاثیر کیفیت قالب بر مقاومت فشاری بتن کوچکتر می‌گردد.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Investigation on Effect and Flatness and Perpendicularity deviation of Cubic Molds on Concrete Compressive Strength Results

نویسندگان [English]

  • Ali Zolghadri 1
  • Babak Ahmadi 2
  • Babak Froutan Mehr 3
  • Mohsen Tadayon 4
1 M.S.C.E in Highway and Transportation Engineering, University of Zanjan, Zanjan, Iran
2 Assistant Professor, Road, Housing & Urban Development Research Center, Tehran, Iran
3 Member of the Board of Directors, Fahab Beton Company, Tehran, Iran
4 Inspector of the Iranian Concrete Institute , Hamedan, Iran
چکیده [English]

One of the influential factors on concrete compressive strength results, which is often neglected in construction and research projects, is the quality of specimen molds. In this study, the effect of six types of 150 mm×150 mm×150 mm cubic molds, including two types of steel molds and four types of plastic molds, on compressive strength (17 MPa to 67 MPa) results of fifteen concrete mixtures at different ages were investigated. It was found that using the worst of the studied molds led to an 18% reduction of the measured compressive strength compared to the best one. These results show that the effect of mold on compressive strength of concrete can be very considerable. This issue can result in incorrect mixture design and an inaccurate measurement of concrete strength produced in construction projects and hence, legal and technical disputes among the sides involved in construction projects. In addition, in this paper, to quantify the quality of the studied molds, two parameters of flatness and perpendicularity deviation were defined. Through applying a linear regression for the obtained results, an empirical formula with high accuracy was presented to predict the effect of the two parameters of molds on the concrete compressive strength reduction factor. This formula indicates that the reduction factor decreases when perpendicularity deviation and flatness deviation values increase.

کلیدواژه‌ها [English]

  • Perpendicularity Deviation
  • Flatness Deviation
  • Compressive Strength
  • Concrete Molds
  • Quality Effect

مراجع

[1].       استاندارد ملی ایران به شماره 1- 1608، بتن سخت‌شده- قسمت 1: شکل، ابعاد و سایر الزامات آزمونه‌ها و قالب‌ها، 1393.
[2].        BS EN 12390-1:2009, Testing hardened concrete. Shape, dimensions and other requirements for     specimens and molds.
[3].       Carrasquillo, P. and R. Carrasquillo, Evaluation of the use of current concrete practice in the production of high strength concrete. Materials Journal, 1988. 85(1): p. 49-54.
[4].       Cusens, A. Strength of concrete test cylinders cast in waxed paper molds. in Journal Proceedings. 1964.
[5].       Day, R., The effect of mold size and mold material on compressive strength measurement using concrete cylinders. Cement, Concrete and Aggregates, 1994. 16(2): p. 159-166.
[6].       Richardson, D.N., Effects of Testing Variables' Effects on the Comparison of Ceoprene Pad and Sulfur Mortar-Capped Concrete Test Cylinders. Materials Journal, 1990. 87(5): p. 489-495.
[7].       Troxell, G. The effect of capping methods and end conditions before capping upon the compressive strength of concrete test cylinders. in Proceedings, American Society of Testing and Materials. 1942.
[8].       Vincent, T. and T. Ozbakkaloglu, Influence of fiber orientation and specimen end condition on axial compressive behavior of FRP-confined concrete. Construction and Building materials, 2013. 47: p. 814-826.
[9].       Ropke, J.C., Concrete problems: causes and cures. 1982.
[10].     Ahmad, S.S. and Y.A. Elmenshawy, Numerical Prediction of Size Effect Factor for Different Compressive Strength Levels. Engineering and Computer Sciences, 2019. 2(6): p. 167-174.
[11].     Li, M., et al., Specimen shape and size effects on the concrete compressive strength under static and dynamic tests. Construction and Building Materials, 2018. 161: p. 84-93.
[12].     Qasim, O.A., A review paper on specimens size and shape effects on the concrete properties. International Journal of Recent Advances in science and technology, 2018. 5(3): p. 13-25.
[13].     Holland, T.C., Testing high strength concrete. Conor. Constr. Conor. Constr., 1987. 32(6): p. 534-536.
[14].     Hester, W.T., FIELD TESTING HIGH-STRENGTH CONCRETES: A CRITICAL REVIEW OF THE STATE OF THE ART. 1980.
[15].     Richardson, D.N., Effects of non-standard concrete cylinder testing techniques. Materials in civil engineering, 1989.
[16].     Madani, H., et al., Effects of Cubic Molds’ Quality on the Compressive Strength and Distortion of Concrete Specimens. Journal of Concrete Structures and Materials, 2020. 5(1): p. 46-69.
[17].     Rezaei, M.J., Mobarakeh, M. , Study the Compressive Strength of Concrete Sampled in Plastic and Cast-Iron Molds, in International Conference on civil engineering, architecture and urban development management in Iran. 2018: Tehran, Iran.
[18].     Otunyo, A. and E. Imo, Evaluation of the effect of various types of moulds on compressive strength of concrete. Scientia Africana, 2018. 17(1).
[19].     Burmeister, R.A. Tests of paper molds for concrete cylinders. in Journal Proceedings. 1950.
[20].     Goldbeck, A.T., Are test cylinders indicative of the true strength of concrete in structures? The Crushed Stone, 1952. 27(2): p. 3-9.
[21].     Howard, E.L., Metal versus paper molds for concrete cylinders. ACI, 1951. 48: p. 98-99.
[22].     Wallace, G.B., Comparison of steel and cardboard molds for fabricating 6-by 12-inch concrete test cylinders. 1950: US Department of the Interior, Bureau of Reclamation, Research and Geology ….
[23].     Henning, N.E., Concrete test molds and concrete capping materials. ACI J., 1961. 32: p. 851-854.
[24].     Price, W.H. Factors influencing concrete strength. in Journal Proceedings. 1951.
[25].     Erntroy, H.C., The effect of some variations in the crushing procedure on the indicated cube compressive strength. , in The Experimental Research of Field Testing of Concrete. 1964, RILEM: Trondheim, Norway. p. 284-308.
[26].     Werner, G. The effect of type of capping material on the compressive strength of concrete cylinders. in Proceedings of ASTM. 1958.
[27].     Davis, H.E., G.E. Troxell, and G.F. Hauck, The testing of engineering materials. 1982.
[28].     ASTM C150 / C150M-15, Standard Specification for Portland Cement., ASTM International, West Conshohocken, PA, 2015.
[29].      آئین‌نامه بتن ایران. نشریه 120 سازمان مدیریت و برنامه‌ریزی کشور، 1379.
[30].      طرح و اجرای ساختمان‌های بتن آرمه، مبحث نهم مقررات ملی ساختمان، 1388.
[31].   BS EN 12390-1:2009, Testing hardened concrete Part 3: esting hardened concrete. Shape, dimensions and other requirements for specimens and moulds.

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سابقه مقاله

  • تاریخ دریافت: 17 فروردین 1402
  • تاریخ بازنگری: 15 مرداد 1402
  • تاریخ پذیرش: 09 آبان 1402

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