A Modified Chemical Index to Predict Fly Ash Dosage for Mitigating Alkali-Silica Reaction

2019 ◽  
Vol 8 (1) ◽  
pp. 20190191 ◽  
Author(s):  
Richard Deschenes ◽  
Casey Jones ◽  
Eric R. Giannini ◽  
Micah Hale
Keyword(s):  
Fly Ash ◽  
Alkali Silica Reaction ◽  
Chemical Index

scholarly journals Durability of blended cement against sodium sulphate attack and alkali-silica reaction

2021 ◽  
Author(s):  
Giri Raj Adhikari
Keyword(s):  
Fly Ash ◽  
Silica Fume ◽  
Alkali Silica Reaction ◽  
Sulphate Attack ◽  
Ternary Blends ◽  
Replacement Level ◽  
Fly Ashes ◽  
Study Results ◽  
High Calcium ◽  
High Calcium Fly Ash

Blended cements were studied for their efficacy against sulphate attack and alkali-silica reaction using six different types of fly ashes, a slag, a silica fume and four types of General Use Portland cement of different alkalinity. The study results showed that low calcium fly ash, silica fume and ground granulated blast furnace slag enhanced the sulphate resistance of cement with increased efficacy with the increase in the replacement level. However, slag and silica fume, especially at low replacement levels, exhibited increased rate of expansion beyond the age of 78 weeks. On the contrary, high calcium fly ashes showed reduced resistance to sulphate attack with no clear trend between the replacement level and expansion. Ternary blends consisting of silica fume, particulary in the amount of 5%, high calcium fly ashes and General Use (GU) cement provided high sulphate resistance, which was attributable to reduced permeability. In the same way, some of ternary blends consisting of slag, high calcium fly ash and GU cement improved sulphate resistance. Pre-blending optimum amount of gypsum with high calcium fly ash enhanced the latter's resistance to sulphate attack by producing more ettringite at the early stage of hydration. In the context of alkali-silica reaction permeability was found to be a contributing factor to the results of the accelerated mortar bar test. High-alkali, high-calcium fly ash was found to worsen the alkali silica reaction when used in concrete containing some reactive aggregates. Ternary blend of slag with high calcium fly ash was found to produce promising results in terms of counteracting alkali-silica reaction.

How does fly ash mitigate alkali–silica reaction (ASR) in accelerated mortar bar test (ASTM C1567)?

2013 ◽  
Vol 37 ◽  
pp. 143-153 ◽  
Author(s):  
Seyed M.H. Shafaatian ◽  
Alireza Akhavan ◽  
Hamed Maraghechi ◽  
Farshad Rajabipour
Keyword(s):  
Fly Ash ◽  
Alkali Silica Reaction ◽  
Accelerated Mortar Bar Test ◽  
Bar Test ◽  
Mortar Bar

scholarly journals Alkali-Silica Reaction Resistance and Pore Solution Composition of Low-Calcium Fly Ash-Based Geopolymer Concrete

2020 ◽  
Vol 5 (11) ◽  
pp. 96
Author(s):  
Jiawei Lei ◽  
Jiajun Fu ◽  
En-Hua Yang
Keyword(s):  
Fly Ash ◽  
Pore Solution ◽  
Systematic Investigation ◽  
Alkali Silica Reaction ◽  
Geopolymer Concrete ◽  
Portland Cement Concrete ◽  
Solution Composition ◽  
Low Calcium ◽  
Underlying Mechanisms ◽  
One Year

Low-calcium fly ash-based geopolymer concrete is generally reported to be less vulnerable to alkali-silica reaction (ASR) than conventional ordinary Portland cement concrete. However, the lack of understanding of pore solution composition of the low-calcium fly ash-based geopolymer limits the investigation of the underlying mechanisms for the low ASR-induced expansion in the geopolymer concrete. This study presents a systematic investigation of the pore solution composition of a low-calcium fly ash-based geopolymer over a period of one year. The results show that the pore solution of the fly ash geopolymer is mainly composed of alkali ions, silicates, and aluminosilicates species. The lower expansion of the geopolymer concrete in the current study is most probably due to the insufficient alkalinity in the geopolymer pore solution as the hydroxide ions are largely consumed for the fly ash dissolution.

Effects of Geopolymer Concrete Fly Ash Based on Alkali Silica Reaction (ASR)

2014 ◽  
Vol 567 ◽  
pp. 405-410 ◽  
Author(s):  
Muhd Fadhil Nuruddin ◽  
Siti Nooriza Abd. Razak
Keyword(s):  
Fly Ash ◽  
Chemical Reaction ◽  
Length Change ◽  
Alkali Silica Reaction ◽  
Geopolymer Concrete ◽  
Alkali Silica Reactivity ◽  
Mortar Bar ◽  
Class F Fly Ash ◽  
Strength And Durability ◽  
Standard Limit

Alkali Silica Reaction (ASR) is a chemical reaction which affects both strength and durability of concrete. ASR occurs due to a chemical reaction between alkali oxides presents in the cement paste and reactive silica in aggregate. This reaction could lead to the volume expansion, cracking, loss of strength and potential failure of the concrete. This research aimed to investigate the potential alkali silica reactivity on geopolymer concrete. Specimens were prepared using Class F fly ash as binder while sodium hydroxide and sodium silicate as alkaline activators. ASTM C1260 was adopted to determine potential alkali silica reactivity by measuring the length change of mortar bar as well as the decrease in compressive strength test. Results show that fly ash based geopolymer concrete is less vulnerable to ASR as the expansion of mortar bar is below the threshold of ASTM standard limit which is 0.10% of expansion. In term of strength, the geopolymer concrete did not reduced instead it increased. From the results, it has indicated that both tests ensure that the durability of geopolymer concrete is excellent and can withstand a long life span.

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