Activation Energy of Alkali-Silica Reactionin CFBC Fly Ash Geopolymer Mortars

2017 ◽  
Vol 882 ◽  
pp. 77-82 ◽  
Author(s):  
Chang Seon Shon ◽  
Dongoun Lee
Keyword(s):  
Activation Energy ◽  
Fly Ash ◽  
Cement Mortar ◽  
Alkali Silica Reaction ◽  
Fluidized Bed Combustion ◽  
Binding Properties ◽  
Different Temperatures ◽  
Naoh Solution ◽  
Cfbc Fly Ash ◽  
High Sulfate

The utilization of fly ashes produced by circulated fluidized bed combustion (CFBC) has been limited in construction application due to their inherent high sulfate and carbon contents although CFBC fly ash exhibits very good binding properties without requiring any supplementary activator. This study reports alkali silica reaction (ASR) behavior of CFBC fly ash geopolymer mortars in terms of activation energy using a modified ASTM C 1260/C 1567. Two different strengths of NaOH solution were used to test reactive and potentially reactive aggregates in the presence of CFBC fly ash. The other variables included a longer test period of 3 months and three different temperatures, namely 60°C, 70°C, and 80°C. It was observed that there was no significant expansion in CFBC fly ash based geopolymer mortar regardless of variation of temperature and alkalinity of test solution. Activation energy of CFBC fly ash geopolymer for ASR was higher than that of plain cement mortar irrespective of strength of NaOH solution.

scholarly journals Utilization of low sulfur fly ash from circulating fluidized bed combustion burner as geopolymer binder

2020 ◽  
Vol 22 (2) ◽  
pp. 94-100
Author(s):  
Antoni Antoni ◽  
Stacia Dwi Shenjaya ◽  
Maria Lupita ◽  
Samuel Santosa ◽  
David Wiyono ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Fluidized Bed ◽  
Water Demand ◽  
Circulating Fluidized Bed ◽  
Fluidized Bed Combustion ◽  
Naoh Solution ◽  
Cfbc Fly Ash ◽  
Low Sulfur ◽  
Circulating Fluidized Bed Combustion

Circulating fluidized bed combustion (CFBC) is a newer type of burner that employ a circulating process to burn fuel effectively. CFBC burning process is gaining more popularity due to its compact size, high efficiency and lower burning temperature compared to the pulverized coal combustion (PCC) burner. The CFBC burner produces fly ash with different physical properties compared to the PCC burner, i.e. the fly ash is not rounded, and required higher water content for comparable workability. The CFBC fly ash also has a high sulfur content that is detrimental for hardened concrete. Due to its drawbacks, the CFBC hardly used as cementitious material and geopolymer precursor. This study focuses on comparing variations in the concentration of NaOH solution and variations in the ratio of alkaline activators to the setting time and compressive strength of geopolymer mortars on a new class of CFBC fly ash, which have low sulfur content. The concentrations of NaOH solution were 6M, 8M, 10M, and 12M, while the alkaline activator ratios used were 3.0, 2.5, 2.0, 1.0, and 0.5. It was concluded that the low sulfur CFBC fly ash has a potential to be utilized as geopolymer precursor, however, with a shortcoming in its high water demand. The CFBC fly ash used in this study resulted in a geopolymer matrix with good compressive strength and stability. The water demand varies with the fly ash sampling time shows the challenges in the utilization of the fly ash. The highest mortar’s compressive strength, 33.4 MPa at 90 days was achieved at NaOH concentration of 8M and ratio of sodium silicate solution to sodium hydroxide solution of 2.5 with excellent stability.

scholarly journals Effect of Elevated Temperature on Engineering Properties of Ternary Blended No-cement Mortar

2018 ◽  
Vol 206 ◽  
pp. 02008
Author(s):  
Harry Hermawan ◽  
Ta-Peng Chang ◽  
Herry Suryadi Djayaprabha ◽  
Hoang-Anh Nguyen
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Elevated Temperatures ◽  
Circulating Fluidized Bed ◽  
Cement Mortar ◽  
Strength Loss ◽  
Pulse Velocity ◽  
Engineering Properties ◽  
Fluidized Bed Combustion ◽  
Cfbc Fly Ash

This paper aims to examine the engineering properties of ternary blended no-cement mortar which subjected to the various elevated temperatures exposure. The mortars were produced by mixing ground granulated blast furnace slag (S), Type-F fly ash (F) and circulating fluidized bed combustion (CFBC) fly ash (C). The water-to-binder ratio was fixed at 0.40 and the CFBC fly ash content was fixed at 15 wt.% of the mixture that acts as the main activator. The specimens were exposed to the elevated temperatures ranging from 200°C to 800°C. The mass loss, compressive strength, and ultrasonic pulse velocity were determined before and after exposure to the elevated temperatures. The obtained results showed after exposed to high temperature, the mortar weight reduction was discovered in the range of 6.0–8.7% when temperature rose from 200°C to 600°C, and decreased significantly up to 12.4% as temperature reached 800°C. The major strength loss occurred after 600°C with the residual compressive strength approximately at 44.2%. At 200°C, increased strength was found on SFC mixture and when temperature rose to 400°C, the specimens still can resist the load reliably with the strength loss less than 8.0%. Consequently, SFC mortar generates good durability and heat resistance below 400°C.

Utilization of Circulating Fluidized Bed Combustion (CFBC) Fly Ash and Coal-Fired Fly Ash in Portland Cement

2014 ◽  
Vol 629-630 ◽  
pp. 306-313 ◽  
Author(s):  
Mao Chieh Chi ◽  
Ran Huang ◽  
Te Hsien Wu ◽  
Toun Chun Fou
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Fluidized Bed ◽  
Building Materials ◽  
Circulating Fluidized Bed ◽  
Setting Time ◽  
Fluidized Bed Combustion ◽  
Initial Setting Time ◽  
Cfbc Fly Ash ◽  
Circulating Fluidized Bed Combustion

Circulating fluidized bed combustion (CFBC) fly ash is a promising admixture for construction and building materials due to its pozzolanic activity and self-cementitious property. In this study, CFBC fly ash and coal-fired fly ash were used in Portland cement to investigate the pozzolanic and cementitious characteristics of CFBC fly ash and the properties of cement-based composites. Tests show that CFBC fly ash has the potential instead of cementing materials and as an alternative of pozzolan. In fresh specimens, the initial setting time of mortars increases with the increasing amount of cement replacement by CFBC fly ash and coal-fire fly ash. In harden specimens, adding CFBC fly ash to replace OPC reduces the compressive strength. Meanwhile, CFBC fly ash would results in a higher length change when adding over 30%. Based on the results, the amount of CFBC fly ash replacement cement was recommended to be limited below 20%.

Chemical Properties and Reactivity of CFBC Fly Ash

2016 ◽  
Vol 722 ◽  
pp. 132-139 ◽  
Author(s):  
Tomáš Váchal ◽  
Rostislav Šulc ◽  
Tereza Janků ◽  
Pavel Svoboda
Keyword(s):  
Thermal Properties ◽  
Fly Ash ◽  
Circulating Fluidized Bed ◽  
Chemical Properties ◽  
Total Content ◽  
Calorimetric Measurement ◽  
Fluidized Bed Combustion ◽  
Cfbc Fly Ash ◽  
Circulating Fluidized Bed Combustion ◽  
Methods Of Measurement

This paper describes chemical properties of fly ash from Circulating fluidized Bed Combustion (CFBC). There are shown thermal properties of fly ash using calorimetric measurement and the total content of calcium oxide CaO was determined. This paper describes the methods of measurement for determining these properties including granulometric measurement and chemical analysis. Also there were described and evaluated properties of fly ash and the reactivity of the fly ash was compared.

Influence of Mechanically-Treatment on Physical-Chemical Properties of Circulation Fluidized Bed Combustion Fly Ash

2012 ◽  
Vol 509 ◽  
pp. 181-188 ◽  
Author(s):  
De Yu Chen ◽  
Yun Yan ◽  
Yuan Zheng Liu ◽  
Meng Huang
Keyword(s):  
Fly Ash ◽  
Fluidized Bed ◽  
Water Demand ◽  
Fine Particles ◽  
Chemical Properties ◽  
Fluidized Bed Combustion ◽  
Volume Stability ◽  
The Matrix ◽  
Cfbc Fly Ash ◽  
Grinding Time

The comprehensive performance, such as water demand, hydration heat, expansion, and self-hardening of circulation fluidized bed combustion (CFBC) fly ash ground by the laboratory mill were studied in this paper. Results show that the percentage of fine particles and fluidity of CFBC fly ash increased with grinding time. However, the water demand at normal consistency of the CFBC ash decreased with grinding time. The hydration exothermic rate of the paste has been accelerated and the time of reaching the volume stability has been shortened. Meanwhile, the compressive strength of the paste and the content of ettringite in the matrix increased with the curing time in the early age, but reversed later.

Influence of Milling on some Chemical Properties and Reactivity of CFBC Fly Ash

2018 ◽  
Vol 760 ◽  
pp. 73-80 ◽  
Author(s):  
Tomáš Váchal ◽  
Rostislav Šulc ◽  
Tereza Janků ◽  
Pavel Svoboda
Keyword(s):  
Fly Ash ◽  
Chemical Analysis ◽  
Circulating Fluidized Bed ◽  
Chemical Properties ◽  
Total Content ◽  
Calorimetric Measurement ◽  
Fluidized Bed Combustion ◽  
Cfbc Fly Ash ◽  
Circulating Fluidized Bed Combustion ◽  
Methods Of Measurement

This paper describes influence of milling on chemical properties of fly ash from Circulating fluidized Bed Combustion (CFBC). Specific properties of fly ash was determined using calorimetric measurement. It was determined heat properties and total content of calcium oxide CaO. The following methods of measurement were also performed: granulometric measurement and chemical analysis. The ash properties of non-milled and milled ashes were also described and evaluated and the ash reactivity was compared.

Grindability of CFBC Fly Ash and High Temperature Fly Ash

2016 ◽  
Vol 722 ◽  
pp. 100-107
Author(s):  
Rostislav Šulc ◽  
Martin Vašák ◽  
Jaromír Poláček
Keyword(s):  
High Temperature ◽  
Fly Ash ◽  
Power Plant ◽  
Circulating Fluidized Bed ◽  
Physical And Mechanical Properties ◽  
Physical Parameters ◽  
Fluidized Bed Combustion ◽  
Particle Size Analyzer ◽  
Cfbc Fly Ash ◽  
Circulating Fluidized Bed Combustion

This article presents the results of fly ash from Circulating fluidized Bed Combustion (CFBC) and high temperature fly ash (defined in EN 450-1) with modified physical parameters by grinding. For this treatment was used the mechanical mill. In this case were used two fly ashes. The first sample was from Tisová power plant (CFBC fly ash) and the second one from Počerady power plant (high temperature fly ash). The modified samples were tested for the effect of grinding time on its grindability and granulometry. For testing of samples was used laser diffraction with particle size analyzer and the grindability was determined. The reason for this step was found more stable and better material which achieves better physical and mechanical properties. The first step is mechanical treatment of fly ash’s granule.

Effect of alkali silica reaction on the mechanical properties of aging mortar bars: Experiments and numerical modeling

2018 ◽  
Vol 28 (2) ◽  
pp. 291-322 ◽  
Author(s):  
M Pathirage ◽  
F Bousikhane ◽  
M D’Ambrosia ◽  
M Alnaggar ◽  
G Cusatis
Keyword(s):  
Mechanical Properties ◽  
Fracture Energy ◽  
Alkali Silica Reaction ◽  
Particle Model ◽  
Computational Framework ◽  
Free Expansion ◽  
Discrete Particle Model ◽  
Different Temperatures ◽  
Naoh Solution ◽  
Crushed Aggregate

Alkali silica reaction and its effect on concrete and mortar have been studied for many years. Several tests and procedures have been formulated to evaluate this reaction, particularly in terms of aggregate reactivity. However, the data given in the literature concerning the mechanical properties of concrete and mortar are scattered and very little information is available for some properties such as fracture energy. In this study, the mechanical behavior of mortar was evaluated and monitored, under normal and accelerated environmental conditions. Fracture energy, compressive strength and tensile strength were measured for mortar specimens, casted with highly reactive Spratt crushed aggregate, at two different storage temperatures (23℃ and 80℃) and at two different alkali concentrations (immersed in water and in 1 N NaOH solution). Moreover, free expansion tests (according to ASTM C1260) and petrographic observations were performed, in order to relate them to the evolution of the mechanical properties of mortar. Results show a decrease of the mechanical properties associated with specimens at 80℃ in alkali solution and that the deterioration due to alkali silica reaction is counter-balanced by the strengthening of mortar resulting from the hydration process. A multi-physics computational framework, based on the Lattice Discrete Particle Model is then proposed. Numerical simulations based on a complete calibration and validation with the obtained experimental data capture the behavior of mortar subjected to the complex coupled effect of strength build-up and alkali silica reaction at different temperatures and alkali contents.

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