scholarly journals State-of-the-Art Report on Alkali Silica Reactivity Mitigation Effectiveness Using Different Types of Fly Ashes

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Enamur R. Latifee
Keyword(s):  
Fly Ash ◽  
State Of The Art ◽  
Oxide Content ◽  
Fly Ashes ◽  
Linear Effect ◽  
Alkali Silica Reactivity ◽  
Rapid Effect ◽  
Different Types ◽  
Class C ◽  
Class F

Use of fly ash by percent replacement of cement is considered as one of the most economical and effective methods for mitigating alkali-silica reaction (ASR) related distress in the concrete. However, fly ash has been proven to be somewhat variable in its effectiveness in inhibiting alkali-silica reactivity, principally because its composition depends on the coal properties from which it is derived. Typically class C fly ashes are not as efficient as class F ashes due to their higher calcium oxide content. Nevertheless, it is important to find out whether the lime content in the fly ash has linear effect on ASR distress mitigation and if the dosage of fly ash is more influential than type of fly ash. This research conducted extensive testing with nine different types of fly ashes with three in each category of fly ashes, class C, class F, and intermediate class. The results indicated that the effect of increased dosage of fly ash on ASR mitigation is linear for both low-lime and high-lime fly ashes and the dosage effect is more significant with rapid effect with high-lime fly ashes compared to low-lime fly ashes.

Available Alkalis in Fly Ash

1985 ◽  
Vol 65 ◽  
Author(s):  
Chau Lee ◽  
Scott Schlorholtz ◽  
Turgut Demirel
Keyword(s):  
Fly Ash ◽  
Calcium Hydroxide ◽  
Fly Ashes ◽  
Class C ◽  
Time Required ◽  
Class F

ABSTRACTThe available alkalis of six Iowa fly ashes, four Class C and two Class F, have been studied as outlined by the procedures listed in ASTM C 311. The purposes of the study were to: (1) assess the significance of the test when it is used to analyze different fly ashes; (2) to investigate the possibility of decreasing the time required to complete the test (it currently requires 28 days for curing). When cured for 28 days at 38 C, the available alkalis were found to be about 60% and 30% of the total equivalent alkalis (equivalent alkalis = %Na20 + 0.658 × %K20) for Class C and Class F fly ashes, respectively. However, more than 85% and more than 40% of the total equivalent alkalis for the Class C and Class F fly ashes, respectively, were mobilized after 5 to 6 months of curing at 38 C. It was concluded that the available alkali test described in ASTM C 311 tends to underestimate the amount of equivalent alkalis present in Class C fly ash-calcium hydroxide mixtures after long periods of time.

scholarly journals A Comparative Study on the Effect of Class C and Class F Fly Ashes on Geotechnical Properties of High-Plasticity Clay

CivilEng ◽  
2021 ◽  
Vol 2 (4) ◽  
pp. 1009-1018
Author(s):  
Salar Shirkhanloo ◽  
Mohammad Najafi ◽  
Vinayak Kaushal ◽  
Mehrdad Rajabi
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Unconfined Compressive Strength ◽  
Geotechnical Properties ◽  
Dry Density ◽  
High Plasticity ◽  
Fly Ashes ◽  
High Plasticity Clay ◽  
Class C ◽  
Class F

Clays generally have a low strength and capacity, and additives are usually used to stabilize them. In recent years, using fly ash to stabilize soil has decreased environmental pollution while also having an economic benefit. The objective of this study is to perform a comparative investigation on the effect of class C and class F fly ashes on geotechnical properties of high-plasticity clay using the Atterberg’s limit, compaction, California Bearing Ratio (CBR), and unconfined compressive strength tests. The results showed that with an increase in the amount of fly ash, there was a decrease in the maximum dry density and an increase in the optimum moisture content. Moreover, an addition of fly ashes of up to 25% caused a reduction of the liquid limit and plasticity index, and an increase in the maximum unconfined compressive strength and CBR. Lengthening the curing time had a positive impact on the unconfined compressive strength of the soil. The soil samples with class C fly ash were seen to possess more efficient geotechnical properties as compared to class F fly ash.

Influence of Cement Composition on Expansions Observed in Standard and Modified ASTM C1260 Test Procedures

2005 ◽  
Vol 1914 (1) ◽  
pp. 53-60 ◽  
Author(s):  
Prasada Rao Rangaraju ◽  
Ketan R. Sompura
Keyword(s):  
Fly Ash ◽  
Mitigation Measures ◽  
Fine Aggregate ◽  
Alkali Content ◽  
Test Procedures ◽  
Alkali Silica Reactivity ◽  
Class C ◽  
Class F Fly Ash ◽  
Different Sources ◽  
Class F

This paper presents the results of a laboratory study conducted to determine the influence of cement composition on the expansions observed in standard and modified ASTM C1260 tests. Also, the effectiveness of selected mitigation measures for alkali—silica reactivity was studied by using a modified ASTM C1260 test. Two different cements with substantially different alkali levels were used in combination with a Class F fly ash and a Class C fly ash. The results obtained from tests with 89 different sources of fine aggregate were analyzed. The results from this study indicate that cement composition has a distinct influence on the expansion levels observed in the ASTM C1260 study. For a majority of the aggregates tested in this study (88%), the use of a specific cement low in alkali content resulted in higher expansion than a cement with a relatively higher alkali content, regardless of the level of reactivity of the aggregate in the standard ASTM C1260 tests. Class F fly ash was found to be more effective than Class C fly ash in reducing the expansions in the modified ASTM C1260 tests. However, the cement used in the mixture influenced the percent reduction in expansion offered by both Class F fly ash and Class C fly ash. The use of low-alkali cement with Class F and Class C fly ashes yielded larger reductions in percent expansion.

Effect of Partial Replacement of Fly Ash by Metakaolin on Strength Development of Fly Ash Based Geopolymer Mortar

2017 ◽  
Vol 744 ◽  
pp. 131-135 ◽  
Author(s):  
Muhammad Zahid ◽  
Nasir Shafiq ◽  
Mohd Fadhil Nuruddin ◽  
Ehsan Nikbakht ◽  
Asif Jalal
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Sodium Hydroxide Solution ◽  
Base Material ◽  
Sodium Silicate Solution ◽  
Silicate Solution ◽  
Partial Replacement ◽  
Strength Development ◽  
Class C ◽  
Class F

This article aims to investigate the compressive strength variation by the addition of metakaolin as a substitute of fly ash in the fly ash based geopolymer mortar. Five, ten and fifteen percent by weight of fly ash was replaced by highly reactive metakaolin. Two type of fly ashes namely, ASTM class F and ASTM class C were used as a base material for the synthesis of geopolymer mortar. Eight molar sodium hydroxide solution mixed with sodium silicate solution was used as alkaline activator. For optimum geopolymerization, mortar was cured at sixty degree Celsius for twenty four hours duration. Results show different behavior of metakaolin replacement on compressive strength for two different types of fly ash based geopolymer mortar. Improvement in compressive strength was seen by addition of metakaolin in ASTM class F fly ash based geopolymer. On the other hand compressive strength was decreased abruptly in fly ash class C based geopolymer up to certain replacement level.

The Use of FBC Fly Ash in the Preparation of Portland Cement Clinker

2016 ◽  
Vol 722 ◽  
pp. 168-172
Author(s):  
Karel Kulísek ◽  
Dominik Gazdič ◽  
Karel Dvořák ◽  
Marcela Fridrichová
Keyword(s):  
Fly Ash ◽  
Calcium Oxide ◽  
Calcium Silicate ◽  
Raw Material ◽  
Cement Clinker ◽  
Oxide Content ◽  
Fly Ashes ◽  
Portland Cement Clinker ◽  
The Impact ◽  
Fbc Fly Ash

The present work focuses on the use of fluid fly ash for Portland clinker burning. Fluid ashes are carriers of all basic oxides represented in the cement raw meal. However, while the share of hydraulic oxides is in ashes sufficient, there is a significant deficiency in calcium oxide content. Preliminary studies have shown that the combination thereof with calcite as the second essential component of the fluid fly-ashes for the raw material based on Portland clinker burning application, it is necessary to solve a problematic issues. The first one concerns the potential leakage SOx resulting from decomposition of CaSO4 ash into the atmosphere. The second circumstance is the correction tracks raw meal in order to redistribute in the samples prepared under the initial studies, the obtained clinker minerals content in favor of calcium silicate, of them further in favor of alite. The last issue is the evaluation of the impact of fluid utilization of fly ash as a partial raw material bases for reducing CO2 emissions in the Portland clinker burning.

The Diffusion of Chloride Ions in Fly Ash/Cement Pastes and Mortars

1986 ◽  
Vol 85 ◽  
Author(s):  
R. I. A. Malek ◽  
D. M. Roy ◽  
P. H. Licastro
Keyword(s):  
Fly Ash ◽  
Water Permeability ◽  
Electrical Potential ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Basic Material ◽  
Fly Ashes ◽  
Cement Pastes ◽  
High Calcium ◽  
Class F

ABSTRACTFly ashes having three distinctly different levels of calcium, designated low-calcium (Class F), intermediate-calcium (Class F/C), and high-calcium (Class C), comprised the basic material for the present study. Pastes and mortars were made using cement and one of three types of fly ashes at various levels of replacement and water-solid ratios. Chloride ion diffusion was measured by applying an electrical potential across cured cylindrical samples and measuring the amount of current passed in a certain period of time (proportional to amount of CE” passed in this time). Other supportive measurements were made, e.g. porosity, pore size distribution, water permeability and surface area. The Cl− ion diffusivity was correlated with the chemical composition of fly ash, mix proportion, and water permeability of the hardened paste or mortar.

scholarly journals Separation of Cenospheres from Fly Ashes by Floatation Method

2010 ◽  
Vol 13 (1-2) ◽  
pp. 89 ◽  
Author(s):  
L.M. Manоcha ◽  
K.A. Ram ◽  
S.M. Manocha
Keyword(s):  
Fly Ash ◽  
Power Plants ◽  
Thermal Power ◽  
Ceramic Particle ◽  
Composition Analysis ◽  
High Concentration ◽  
Fly Ashes ◽  
Power Station ◽  
Different Types ◽  
Chemical Composition Analysis

Fly-ashes are non-combustible mineral residues which are produced from coal in thermal power plants. Four different types of fly ashes were collected from different power station in Gujarat. Characterization through SEM shows that fly ash contains cenosphere i.e. gas bubble containing ceramic particle independent of their bulk density. Floatation technique was used for the separation of cenosphere from fly ash. Two solvents with extremely different densities were used for the separation of cenospheres. All methods gave approximately yield of less than 1 % cenosphere in fly ash. Color of cenospheres varied from gray to almost white and the value of density range from 0.4 – 0.8 g/cc. Further, chemical composition analysis revealed that cenospheres do not contain any high concentration of hazardous elements.

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