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

Download

index.pdf

Date

2019

Author

Çelen, Ahmet Ziya

Metadata

Show full item record

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Item Usage Stats

140
views

77
downloads

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.

Subject Keywords

Silica., Alkali-Silica Reaction (ASR), Fly Ash, Chemical Composition, Portland Cement.

URI

http://etd.lib.metu.edu.tr/upload/12624486/index.pdf
https://hdl.handle.net/11511/44214

Collections

Graduate School of Natural and Applied Sciences, Thesis

Suggestions

OpenMETU
Core

Reduction in alkali-silica expansion due to steel microfibers Turanlı, Lutfullah; Shomglin, K; Ostertag, CP; Monteiro, PJM (2001-05-01) 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...
Utilization of GGBFS blended cement pastes in well cementing Alp, Barış; Yaman, İsmail Özgür; Akın, Serhat; Department of Cement Engineering (2012) In well cementing, the cement slurry is exposed to the conditions far different than those of ordinary Portland cement (PC) used in construction. After placement, hardened cement paste should preserve integrity and provide zonal isolation through the life of the well. American Petroleum Institute (API) Class G cement is the most common cement type used in various well conditions. Class G cement has a high degree of sulfate resistance which makes it more stable than PC when subjected to the compulsive well c...
Effect of alkali-silica reaction expansion on mechanical properties of concrete Hafçı, Alkan; Turanlı, Lütfullah; Department of Civil Engineering (2013) 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...
Modelling of asymmetric membrane formation Mchugh, A.j.; Yılmaz, Levent (American Chemical Society; 1986-09-01) Asymmetric membranes are generally prepared by the phase inversion techniques, the principal steps of which involve casting a thin film of a homogeneous polymer solution onto a suitable substrate, followed by quenching in a nonsolvent bath to precipitate the membrane film. Since most studies of the process has been concerned with the development of specific preparation recipies, explanations of structure formation have generally been ad-hoc and qualitative. This paper presents the results of recent modellin...
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...

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.