Volume 20, Issue 1 (2020)                   IQBQ 2020, 20(1): 0-0 | Back to browse issues page

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1- Young Researchers and Elites club, Science and Research Branch, Islamic Azad University, Tehran, Iran , amirbahador.mk@gmail.com
2- Young Researchers and Elites club, Science and Research Branch, Islamic Azad University, Tehran, Iran
Abstract:   (1096 Views)
Concrete due to its special feature, is the most widely consumed material in the world, after water. But the production process of ordinary Portland cement as a main component of conventional concretes, has major disadvantages such as high amount of carbon dioxide emission and high energy consumption. Therefore, it seems necessary to find an alternative to ordinary Portland cement. In recent years, geopolymer has been introduced as a novel cementing agent and green alternative to the Portland cement which can eliminate the extensive negative of ordinary Portland cement production process. According to the needed engineering characteristics perspective in civil engineering, the geopolymer concretes have better chemical and mechanical properties than the ordinary ones such as high compressive, flexural and tensile strength, rapid hardening, resistance against high heat and firing, low penetration, resistance against salts and acids attacks and low creep. Compressive strength is considered as one of the important characteristics of concrete. In geopolymer concretes, according to the ingredients, several factors have been identified as important parameters affecting the compressive strength like: the type of aluminosilicate source, the molar composition of the oxides present in the aluminosilicate source, the curing regime, the water content, the weight ratio of alkaline activator solution to aluminosilicate source, alkaline activator solution parameters and etc. Hence, in this experimental research, several factors affecting the compressive strength of metakaolin-based geopolymer concrete including: the type of alkaline activator solution, the weight ratio of water to solid material participated in geopolymerization, sodium hydroxide concentration, the weight ratio of alkaline activator solution to aluminosilicate source and sodium silicate to sodium hydroxide weight ratio, were studied. In this regard, geopolymer concrete specimens were made and cured in 80 °C for 24 hours. After curing, specimens were placed in the ambient condition and compressive strength test, were performed. The obtained results indicated that using potassium hydroxide and potassium silicate as an alkaline activator solution, result in higher 28-day compressive strength of geopolymer concrete compare to sodium-based alkaline activator solution. On the other hand, using sodium hydroxide and sodium silicate as an alkaline activator solution, result in higher 3- and 7-day compressive strengths and also, faster hardening compare to potassium-based alkaline activator solution. Furthermore, increasing the weight ratio of water to solid material result in significant decreasing geopolymer concrete compressive strength. Also, 7-and 28-day compressive strength of geopolymer concrete is increases with increase in concentration of sodium hydroxide up to 14 M, but for 16 M, there is no remarkable changes in compressive strength. Besides, increasing sodium hydroxide concentration, causes faster hardening of geopolymer concrete. It is also absorbed that increasing the alkaline activator solution to metakaolin weight ratio result in decreasing geopolymer concrete compressive strength. Moreover, Increasing the weight ratio of sodium silicate to sodium hydroxide up to 1.5 (the optimum ratio), leads to achieve the highest 7-and 28-day compressive strengths of geopolymer concrete, but 7-and 28-day compressive strengths of geopolymer concrete is decreases noticeably, with further increase in weight ratio of sodium silicate to sodium hydroxide ratio up to 3. Compressive strength of geopolymer concrete is increases with increase in curing temperature up to 80 °C, but further increase up to 90 °C, result in decreasing geopolymer concrete compressive strength.
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Article Type: Original Research | Subject: Civil and Structural Engineering
Received: 2019/06/30 | Accepted: 2020/05/6 | Published: 2020/04/29