Hydration and strength development of binder based on high-calcium oil shale fly ash

Low-calcium fly ash is paid much attention for its wide use in engineering, the research and application technology of it are very mature, but as to high-calcium fly ash concrete, the researches on stability, mechanical property and durability of it are very less , The existing researches are still inadequate for practice of engineering. As to this problem, using small shek kip hydropower project as example, the volume stability of high-calcium fly ash concretes with different fly ash dosages are tested, then the optimal dosage of the high-calcium fly ash is determined; based on this, the impacts of high-calcium fly ash on the performance of mechanical properties , impermeability and frost resistance of concrete are studied; Finally, macro performance is analyzed from a micro-mechanism point of view through taking the electron micrograph. As the study shows, the optimal dosage of high-calcium fly ash should be taken as 20% -25%; for the concrete with special requirements, the dosage can be relaxed to 30% when the high-calcium fly ash achieves high quality. The compressive strength of high-calcium fly ash concrete is higher than the low-calcium fly ash concrete. Strength development advantage of high-calcium fly ash concrete reflects at the early age, this advantage takes the trend of weakening as the development of age. Concrete mixed with high-calcium fly ash has good performance in impermeability. The high-calcium fly ash has high activity, the high-calcium fly ash and secondary hydration reaction products can be filled into the pore capillary and cracks of the concrete structure, improving the pore structure, thereby increasing the density of cement paste. High-calcium fly ash concrete has good performance in frost resistance. The destructive effects of freeze-thaw cycles on cement structure has connection with the microstructure of cement and impermeability , the improvement of impermeability avoids the water entering into the concrete, reduces the risk of destruction caused by frost heave.The study on micro-mechanism proves well the macro-phenomena above.

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Influence of Concrete Sludge Addition in the Properties of Alkali-Activated and Non-Alkali-Activated Fly Ash-Based Mortars

Advances in Civil Engineering ◽

10.1155/2021/5534002 ◽

2021 ◽

Vol 2021 ◽

pp. 1-14

Author(s):

Fotini Kesikidou ◽

Stavroula Konopisi ◽

Eleftherios K. Anastasiou

Keyword(s):

Fly Ash ◽

Silicon Oxide ◽

Strength Development ◽

Alkali Activation ◽

Early Age ◽

Fly Ash Concrete ◽

High Calcium ◽

High Calcium Fly Ash ◽

Potential Synergy ◽

Alkali Activated

This study investigated the use of concrete sludge, a by-product of the ready-mix concrete industry, in combination with high-calcium fly ash in binary cementless binders. Concrete sludge was used in substitution rates ranging from 0% to 60% in test fly ash-based mortars to determine potential synergy. The mortars were tested for fresh and hardened properties; workability, viscosity, strength development, open porosity, early-age shrinkage, and analytical tests were carried out. A mortar with 50% fly ash and 50% limestone filler as binders was used for comparison purposes. Furthermore, a series of mortars with fly ash and concrete sludge were alkali-activated in order to determine potential strength gain. In the activated mortars, two fractions of concrete sludge were used, under 75 μm and 200 μm, due to different silicon oxide contents, while one mortar was cured at 40°C to investigate the effect of heating on alkali activation. Results show that sludge contributes to the formation of C-S-H and strength development when used in combination with high-calcium fly ash even at high replacement rates. The alkali activation of fly ash-concrete sludge system contributed to early-age strength development and to early-age shrinkage reduction.

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Interrelationship Analysis of Geopolymer Components Using Pearson Correlation Technique

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.567.417 ◽

2014 ◽

Vol 567 ◽

pp. 417-421 ◽

Cited By ~ 1

Author(s):

Andri Kusbiantoro ◽

Norbaizurah Rahman ◽

Noor Fifinatasha Shahedan

Keyword(s):

Compressive Strength ◽

Fly Ash ◽

Elemental Composition ◽

Setting Time ◽

Source Material ◽

Curing Temperature ◽

Strength Development ◽

Correlation Technique ◽

High Calcium ◽

Geopolymer Binder

Performance of geopolymer based specimens is significantly affected by internal and external aspects. Curing temperature and air humidity are among the prominent external factors that contribute to the alteration of geopolymer properties. Nevertheless, internal component of geopolymer binder also carries essential effect to the hardened geopolymer binder produced. In this research, the study was concentrated on the elemental composition of source material components and their interrelation to the performance of geopolymer binder produced. Different types of fly ash were used as the source material in this research. Low calcium (class-F) fly ash was combined with high calcium (class-C) fly ash to determine the elemental composition effect, particularly SiO2, Al2O3, and CaO to the geopolymer properties. Analysis using SYSTAT statistical software indicated the importance of oxide composition of source material to the geopolymer specimens produced. Initial setting time of geopolymer paste was also possibly important to the compressive strength of geopolymer specimens produced. Nevertheless, final setting time indicated less importance to the compressive strength development of geopolymer binder.

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The Application of Different Curing Models to the Strength Development of High Calcium Fly Ash Geopolymer Incorporating Limestone

Journal of Physics Conference Series ◽

10.1088/1742-6596/1108/1/012087 ◽

2018 ◽

Vol 1108 ◽

pp. 012087

Author(s):

A Wardhono

Keyword(s):

Fly Ash ◽

Strength Development ◽

High Calcium ◽

High Calcium Fly Ash

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The effect of water binder ratio on strength development of class C fly ash geopolymer mortar prepared by dry geopolymer powder

MATEC Web of Conferences ◽

10.1051/matecconf/201925805032 ◽

2019 ◽

Vol 258 ◽

pp. 05032 ◽

Cited By ~ 1

Author(s):

Arie Wardhono

Keyword(s):

Compressive Strength ◽

Fly Ash ◽

Calcium Content ◽

Strength Properties ◽

Strength Development ◽

Effect Of Water ◽

High Calcium ◽

Binder Ratio ◽

Geopolymer Binder ◽

Water Binder Ratio

The use of geopolymer binder as cement replacement material can reduce the amount of carbon dioxide gas produced during the Portland Cement manufacturing process. However, the main issue of geopolymer binder is in the mixing process of sodium silicate and NaOH which requires specialized knowledge and strict supervision. This paper reports the effect of water binder ratio on strength development of fly ash geopolymer mortar using dry geopolymer powder. Fly ash with high calcium content was used as primary material. The dry geopolymer powder was prepared by wet mixing method which was made by drying a mixture of NaOH solution and limestone for 24 hours. The variations of water to binder ratio were 0.30, 0.35, 0.40, 0.45, and 0.50. Strength properties were measured by compressive strength at the age of 7, 14 and 28 days. The results showed that the water binder ratio significantly affect the strength development of geopolymer mortar prepared by dry geopolymer powder. The water binder ratio of 0.40 gives the highest compressive strength of 10.3 MPa at 28 days. This suggests that the use of dry geopolymer powder on geopolymer mortar production can overcome the difficulties of geopolymer mortar mixing on site.

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Effect of High Calcium Fly Ash, Ladle Furnace Slag, and Limestone Filler on Packing Density, Consistency, and Strength of Cement Pastes

Materials ◽

10.3390/ma14020301 ◽

2021 ◽

Vol 14 (2) ◽

pp. 301

Author(s):

Eleftherios K. Anastasiou

Keyword(s):

Fly Ash ◽

Cementitious Materials ◽

Supplementary Cementitious Materials ◽

Strength Development ◽

Ladle Furnace ◽

Limestone Filler ◽

Cement Pastes ◽

High Calcium ◽

High Calcium Fly Ash ◽

Furnace Slag

Environmental considerations and technical benefits have directed research towards reducing cement clinker content in concrete, and one of the best ways to do this is to replace cement with supplementary cementitious materials. High calcium fly ash, ladle furnace slag, and limestone filler were investigated as supplementary cementitious materials in cement pastes, and binary mixtures were produced at 10%, 20%, and 30% cement replacement rates for each material. The water requirement for maximum packing and for normal consistency were obtained for each paste, and strength development was determined at 3, 7, 28, and 90 days for the 20% replacement rate. Furthermore, two ternary mixtures at 30% cement replacement were also prepared for maximum packing density and tested for compressive strength development. The results showed that high calcium fly ash decreased cement paste packing and increased water demand but contributed to strength development through reactivity. Ladle furnace slag and limestone filler, on the other hand, were less reactive and seemed to contribute to strength development through the filler effect. The ternary paste with 70% cement, 20% high calcium fly ash, and 10% limestone filler showed equivalent strength development to that of the reference cement paste.

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