Utilization of fly ash-portland cement binary systems to control alkali-silica reaction

Çelen, Ahmet Ziya
The highly alkaline pore solution of the portland cement concrete is not an ideal environment for certain reactive aggregates with poorly-crystalline or amorphous silica phases. In this environment, these aggregates partially or completely disintegrate resulting in formation of a hydrophilic, amorphous gel mainly composed of alkalis and water from the pore solution of the hydrated cement matrix and silica from the aggregates. The newly formed alkali-silica reaction (ASR) gel can expand by absorbing huge amounts of water irreversibly, becoming a significant problem if the gel is confined in a matrix such as hardened cement paste. Expansion of the gel can result in localized internal stresses that cannot be relieved by movement of the ASR gel into to the present voids of the matrix leading to extensive micro-cracks in the concrete. Eventually, ASR can cause critical loss of stiffness, impermeability and strength of concrete. The focus of this thesis is evaluating the ASR performance of portland cement/fly ash binary mortars. For this purpose, a total of 13 fly ashes with a wide range of chemical and mineralogical composition are selected from the leading thermal power plants in Turkey (Tunçbilek, Çatalağzı, Afşin Elbistan, İçdaş, Kemerköy, Yatağan and Yeniköy). The ASR performance of such a variety of Turkish fly ashes has not been investigated at this level before. An in-depth analysis of the impact of chemical and mineralogical differences of the fly ashes on the ASR performance of binary Portland cement/fly ash mortars are also conducted.


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Alkali-silica reaction (ASR) is a chemical deterioration process which arises in concrete due to reactive aggregate from its constituent, sufficient alkalis from cement or external resources and humidity about 85%. ASR gel, formed by the reaction, absorbs water and expands so that it causes expansion and cracking in concrete. ASR has detrimental effects on mechanical properties of concrete. Therefore, ASR which is a long and a constantly progressive reaction may become a threat to the safety of concrete str...
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The alkali-silica reaction (ASR) produces an expansive gel that may cause cracking and displacement in concrete structures. Steel microfibers ranging from 1% to 7% by volume of cement mortar were incorporated to reduce the expansion and cracking. All specimens contained 5% of opal by weight of fine aggregates. The samples were cast and tested according to ASTM C-1260. A considerable reduction in expansion was observed for all steel microfiber-reinforced mortar specimens compared to the control specimens wit...
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Mchugh, A.j.; Yılmaz, Levent (American Chemical Society; 1986-09-01)
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Extension of the chemical index model for estimating Alkali-Silica reaction mitigation efficiency to slags and natural pozzolans
Mahyar, Mandi; Erdoğan, Sinan Turhan; Tokyay, Mustafa (2018-08-10)
Supplementary cementitious materials (SCMs) can mitigate alkali silica reaction (ASR) but the level of cement replacement required is difficult to estimate for a particular SCM. The Chemical Index Model was recently proposed to estimate the relation between mortar expansion and the chemical compositions of cement and fly ash but has not been tested extensively for use with other SCMs. This study uses natural pozzolans and blast furnace slags, in addition to fly ashes, with two portland cements and a reactiv...
Effect of reinforcement and pre-stressing force oın ASR expansion
Musaoğlu, Orhan; Turanlı, Lütfullah; Sarıtaş, Afşin; Department of Civil Engineering (2012)
Alkali Silica Reaction in concrete is a chemical deterioration process occurring between alkalis in cement paste and reactive aggregates. ASR increases expansion and cracking as well as other durability problems such as freezing and thawing. It is most probable that concrete structure will collapse unless mechanical, mineral, or chemical preventive measures are taken against ASR or this problem is realized and solved in the design stage of the concrete structure or later on. Rather than ordinary preventive ...
Citation Formats
A. Z. Çelen, “Utilization of fly ash-portland cement binary systems to control alkali-silica reaction,” Thesis (M.S.) -- Graduate School of Natural and Applied Sciences. Civil Engineering., Middle East Technical University, 2019.