كليدواژه :
بتن ژئوپليمري , متاكائولن , مقاومت فشاري , محلول فعالكننده قليايي , سديم , پتاسيم
چكيده لاتين :
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.
