FACTORS AFFECTING THE WORKABILITY AND STRENGTH OF ALKALI-ACTIVATED HIGH CALCIUM FLY ASH CONCRETE

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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A Mix Design Procedure for Alkali-Activated High-Calcium Fly Ash Concrete Cured at Ambient Temperature

Advances in Materials Science and Engineering ◽

10.1155/2018/2460403 ◽

2018 ◽

Vol 2018 ◽

pp. 1-13 ◽

Cited By ~ 13

Author(s):

Tanakorn Phoo-ngernkham ◽

Chattarika Phiangphimai ◽

Nattapong Damrongwiriyanupap ◽

Sakonwan Hanjitsuwan ◽

Jaksada Thumrongvut ◽

...

Keyword(s):

Compressive Strength ◽

Fly Ash ◽

Design Methodology ◽

Design Procedure ◽

Mix Design ◽

Fly Ash Concrete ◽

High Calcium ◽

High Calcium Fly Ash ◽

Alkaline Activator ◽

Alkali Activated

This research focuses on developing a mix design methodology for alkali-activated high-calcium fly ash concrete (AAHFAC). High-calcium fly ash (FA) from the Mae Moh power plant in northern Thailand was used as a starting material. Sodium hydroxide and sodium silicate were used as alkaline activator solutions (AAS). Many parameters, namely, NaOH concentration, alkaline activator solution-to-fly ash (AAS/FA) ratio, and coarse aggregate size, were investigated. The 28-day compressive strength was tested to validate the mix design proposed. The mix design methodology of the proposed AAHFAC mixes was given step by step, and it was modified from ACI standards. Test results showed that the 28-day compressive strength of 15–35 MPa was obtained. After modifying mix design of the AAHFAC mixes by updating the AAS/FA ratio from laboratory experiments, it was found that they met the strength requirement.

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Alkali-Activated Controlled Low-Strength Material Utilizing High-Calcium Fly Ash and Steel Slag for Use as Pavement Materials

Journal of Materials in Civil Engineering ◽

10.1061/(asce)mt.1943-5533.0003798 ◽

2021 ◽

Vol 33 (8) ◽

pp. 04021178

Author(s):

Thanakorn Chompoorat ◽

Thanakit Thepumong ◽

Peem Nuaklong ◽

Pitcha Jongvivatsakul ◽

Suched Likitlersuang

Keyword(s):

Fly Ash ◽

Steel Slag ◽

Pavement Materials ◽

High Calcium ◽

High Calcium Fly Ash ◽

Strength Material ◽

Low Strength ◽

Controlled Low Strength Material ◽

Alkali Activated

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Fresh Properties and Early Compressive Strength of Alkali-Activated High Calcium Fly Ash Paste

Lecture Notes in Civil Engineering - Proceedings of the 4th Congrès International de Géotechnique - Ouvrages -Structures ◽

10.1007/978-981-10-6713-6_49 ◽

2017 ◽

pp. 497-507

Author(s):

Eslam Gomaa ◽

Simon Sargon ◽

Cedric Kashosi ◽

Mohamed ElGawady

Keyword(s):

Compressive Strength ◽

Fly Ash ◽

Fresh Properties ◽

High Calcium ◽

High Calcium Fly Ash ◽

Alkali Activated

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Experiment and Micro-Mechanism Study on Mechanical Properties and Durability of High-Calcium Fly Ash Concrete

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.480-481.59 ◽

2011 ◽

Vol 480-481 ◽

pp. 59-65

Author(s):

Shuang Xi Li ◽

Tuan She Yang ◽

Zhi Ming Wang ◽

Quan Hu

Keyword(s):

Mechanical Properties ◽

Fly Ash ◽

Frost Resistance ◽

Strength Development ◽

Hydration Reaction ◽

Optimal Dosage ◽

Fly Ash Concrete ◽

Low Calcium ◽

High Calcium ◽

High Calcium 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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