دانلود رایگان مقاله لاتین پتاسیم خاکستر ژئوپلیمر سنتز از سایت الزویر
عنوان فارسی مقاله:
رفتار فشاری سدیم و پتاسیم فعال خاکستر ژئوپلیمر سنتز در دمای بالا: مطالعه مقایسه ای
عنوان انگلیسی مقاله:
Compressive behaviour of sodium and potassium activators synthetized fly ash geopolymer at elevated temperatures: A comparative study
سال انتشار : 2016
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مقدمه انگلیسی مقاله:
1. Introduction
Many reinforced concrete (RC) structures experience fire during their service life. The mechanical properties and stiffness of concrete decrease significantly due to exposure to elevated temperatures during fire. This reduction in strength is associated with the dehydroxylation of Ca(OH)2 between 400 and 500 °C and continuous dehydration of Calcium Silica Hydrate (CSH) from 105 °C in cement matrix in concrete. The difference in thermal expansion/contraction between cement paste and aggregates cause significant cracking in the concrete, which also contributes to the reduction in mechanical strengths and stiffness of concrete. In addition thermal gradient in concrete also contributes to its poor performance at elevated temperatures. Geopolymer is a new construction material which has gained its popularity in recent years due to its environment friendliness and excellent mechanical, durability and fire resistant properties in severe environment. Geopolymer is first introduced by Davidovits [1] and is generally synthetized by reacting aluminate and silicate bearing source materials with alkali activator. The hardening mechanism for geopolymers essentially involves the poly-condensation reaction of geopolymeric precursors, usually alumina-silicate oxides, with alkali polysilicates yielding a polymeric silicon-oxygen-aluminium framework. Due to this inorganic framework, geopolymers are intrinsically fire resistant and have been shown to have excellent thermal stability with very little gel structural degradation up to 700–800 °C, which is the most significant advantage of geopolymer over cement based binder as the latter breakdown due to dehydration of its hydrates at elevated temperatures. Extensive researches have been conducted to study various mechanical and durability properties of geopolymer. Significant efforts have also been made by many researchers to study the effect of elevated temperatures on mechanical properties of geopolymer. However, most of the studies were on different geopolymers which were made by different types of source materials and alkali activators, e.g. fly ash activated by sodium based alkali activators [2–5], fly ash activated by combined sodium and potassium based activators [6–8], combined fly ash and slag activated by sodium based activator [9], metakaolin activated by combined sodium and potassium based activators [10], etc. Among all above source materials the class F fly ash is rich in silica and alumina and low in calcium oxide, which enables its higher stability at elevated temperature in fire than others. Moreover, it is cheaper, easily and widely available than other source materials. This paper presents the effects of sodium and potassium based activators on the compressive strength and damage behaviour of fly ashgeopolymer at various elevated temperatures of 200, 400, 600 and 800 °C. The effects of silicate to hydroxide ratios for both sodium and potassium based activators on the compressive strengths and physical changes like the mass loss, volumetric shrinkage, cracking behaviour at above elevated temperatures are also evaluated. X-ray diffraction (XRD) and thermogravimetric analysis (TGA) are also used to support the observed physical behaviour and strength properties.
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کلمات کلیدی:
Compressive strength of fly-ash-based geopolymer concrete at ... onlinelibrary.wiley.com/doi/10.1002/fam.2240/abstract by FUA Shaikh - 2015 - Cited by 19 - Related articles Feb 12, 2014 - Compressive strength of fly-ash-based geopolymer concrete at elevated temperatures ... by sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solutions. ... Similar behaviour is also observed at 800 °C, where the compressive ... The compressive strength in the latter increased at 600 and 800 °C. The ... Geopolymer, Green Chemistry and Sustainable Development Solutions: ... https://books.google.com/books?isbn=2951482000 Joseph Davidovits - 2005 - Artificial minerals ... concrete, the utilisation of the material in structural members, and the long-term behaviour. ... slag etc., yield higher compressive strength when compared to those synthesised from ... A combination of sodium or potassium silicate and sodium or potassium hydroxide has been widely used as the alkaline activator, with the ... Geopolymer Binders: A Need for Future Concrete Construction - Hindawi https://www.hindawi.com/journals/isrn/2013/509185/ by K Srinivasan - 2013 - Cited by 8 - Related articles Jun 6, 2013 - A similar reaction is observed in the case of potassium silicate added to potassium hydroxide solution. ... mixed alkali activator of sodium hydroxide and sodium silicate solution. It was reported that a high compressive strength can be obtained ... The linear elastic behavior of the matrix could not be affected ... Geopolymers: Structures, Processing, Properties and Industrial ... https://books.google.com/books?isbn=1845696387 J L Provis, J S J van Deventer - 2009 - Technology & Engineering For materials activated with potassium silicate, compressive strength was ... of alkali-activated fly ash materials with Na-containing activators was lower than that of ... a growing tendency; this behaviour can be attributed to the solidifying melt. The Effect of Different Parameters on the Development of ... - NCBI - NIH https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4228731/ by RH Kupaei - 2014 - Cited by 7 - Related articles Oct 28, 2014 - The result revealed that a maximum compressive strength of 32 MPa .... alkaline activators of NaOH, potassium hydroxide (KOH), and sodium silicate of ... different characteristics and behavior for them, compared to the use of ... [PDF]Effect of Sodium Hydroxide Concentration and Alkaline Ratio on the ... sphinxsai.com/2014/vol6pt4/3/(2446-2450)Jul-Aug14_.pdf on the Compressive Strength of Slag Based Geopolymer ... hydroxide with sodium silicate or potassium hydroxide with potassium silicate11-12. ... GGBS requires an Alkaline Activator Solution (AAS) to form Geopolymerization reaction. .... Strength Behaviour and Hydration Products, Cement and Concrete Research., 2000, ...
