scholarly journals Behavior of Alkali-Activated Fly Ash through Underwater Placement

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6865
Author(s):  
Zarina Yahya ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
Long-yuan Li ◽  
Dumitru Doru Burduhos Nergis ◽  
Muhammad Aiman Asyraf Zainal Hakimi ◽  
...  
Keyword(s):  
Fly Ash ◽  
Fine Particles ◽  
Sodium Hydroxide Solution ◽  
Setting Time ◽  
Composition Analysis ◽  
Surrounding Water ◽  
Conventional Concrete ◽  
Dry Conditions ◽  
Underwater Concrete ◽  
Alkali Activated

Underwater concrete is a cohesive self-consolidated concrete used for concreting underwater structures such as bridge piers. Conventional concrete used anti-washout admixture (AWA) to form a high-viscosity underwater concrete to minimise the dispersion of concrete material into the surrounding water. The reduction of quality for conventional concrete is mainly due to the washing out of cement and fine particles upon casting in the water. This research focused on the detailed investigations into the setting time, washout effect, compressive strength, and chemical composition analysis of alkali-activated fly ash (AAFA) paste through underwater placement in seawater and freshwater. Class C fly ash as source materials, sodium silicate, and sodium hydroxide solution as alkaline activator were used for this study. Specimens produced through underwater placement in seawater showed impressive performance with strength 71.10 MPa on 28 days. According to the Standard of the Japan Society of Civil Engineers (JSCE), the strength of specimens for underwater placement must not be lower than 80% of the specimen’s strength prepared in dry conditions. As result, the AAFA specimens only showed 12.11% reduction in strength compared to the specimen prepared in dry conditions, thus proving that AAFA paste has high potential to be applied in seawater and freshwater applications.

Experimental Study on Alkali-Activated Slag-Lithium Slag-Fly Ash Environmental Concrete

2011 ◽  
Vol 287-290 ◽  
pp. 1237-1240
Author(s):  
Lan Fang Zhang ◽  
Rui Yan Wang
Keyword(s):  
Experimental Study ◽  
Compressive Strength ◽  
Fly Ash ◽  
Setting Time ◽  
Alkali Activated Slag ◽  
Percent Increase ◽  
Compressive Strength Of Concrete ◽  
Activated Slag ◽  
Lithium Slag ◽  
Alkali Activated

The aim of this paper is to study the influence of lithium-slag and fly ash on the workability , setting time and compressive strength of alkali-activated slag concrete. The results indicate that lithium-slag and fly-ash can ameliorate the workability, setting time and improve the compressive strength of alkali-activated slag concrete，and when 40% or 60% slag was replaced by lithium-slag or fly-ash, above 10 percent increase in 28-day compressive strength of concrete were obtained.

scholarly journals Effect of calcium-rich compounds on setting time and strength development of alkali-activated fly ash cured at ambient temperature

2018 ◽  
Vol 9 ◽  
pp. e00198 ◽  
Author(s):  
Prinya Chindaprasirt ◽  
Tanakorn Phoo-ngernkham ◽  
Sakonwan Hanjitsuwan ◽  
Suksun Horpibulsuk ◽  
Anurat Poowancum ◽  
...  
Keyword(s):  
Fly Ash ◽  
Ambient Temperature ◽  
Setting Time ◽  
Strength Development ◽  
Alkali Activated

scholarly journals Alkali-Activated Hybrid Concrete Based on Fly Ash and Its Application in the Production of High-Class Structural Blocks

Crystals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 946
Author(s):  
Oriana Rojas-Duque ◽  
Lina Marcela Espinosa ◽  
Rafael A. Robayo-Salazar ◽  
Ruby Mejía de Gutiérrez
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Flexural Modulus ◽  
Setting Time ◽  
Modulus Of Rupture ◽  
Strength Development ◽  
Block Type ◽  
High Class ◽  
Structural Blocks ◽  
Alkali Activated

This article reports the production and characterization of a hybrid concrete based on the alkaline activation of a fly ash (FA) of Colombian origin, which was added with 10% Portland cement (OPC) in order to promote the compressive strength development at room temperature. The alkali-activated hybrid cement FA/OPC 90/10 was classified as a low heat reaction cement (type LH), according to American Society of Testing Materials, ASTM C1157; the compressive strength was of 31.56 MPa and of 22.68 MPa (28 days) at the levels of paste and standard mortar, respectively, with an initial setting time of 93.3 min. From this binder, a hybrid concrete was produced and classified as a structural type, with a compressive strength of 23.16 MPa and a flexural modulus of rupture of 5.32 MPa, at 28 days of curing. The global warming potential index (GWP 100), based on life cycle analysis, was 35% lower than the reference concrete based on 100% OPC. Finally, its use was validated in the manufacture of a solid block-type construction element, which reached a compressive strength of 21.9 MPa at 28 days, exceeding by 40.6% the minimum strength value established by the Colombia Technical Standard, NTC 4026 (13 MPa) to be classified as high class structural blocks.

Development of Non-Autoclaved Aerated Concrete by Alkali Activated Phosphorus Slag

2011 ◽  
Vol 250-253 ◽  
pp. 1147-1152 ◽  
Author(s):  
Xiao Jun Jiang ◽  
Yan Yun ◽  
Zhi Hua Hu
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Bulk Density ◽  
Sodium Silicate ◽  
Setting Time ◽  
Liquid Sodium ◽  
Molar Ratio ◽  
Autoclaved Aerated Concrete ◽  
Aerated Concrete ◽  
Alkali Activated

The feasibility of manufacturing non-autoclaved aerated concrete using alkali activated phosphorus slag as a cementitious material was investigated in this paper. Liquid sodium silicate with various modules (the molar ratio between SiO2 and Na2O) was used as alkali activator and a part of phosphorus slag was replaced with fly ash which was used to control the setting time of aerated concrete. The influences of the fly ash, curing procedure, modulus of sodium silicate solution and concentration of alkalis on the compressive strength and bulk density of non-autoclaved aerated concrete have been studied. Moreover, the types of the hydration products were investigated using XRD and SEM. The results indicate that: the compressive strength of aerated concrete was influenced by concentration of alkalis obviously. The compressive strength of 11.9MPa and the bulk density of 806kg/m3 were obtained with an activator of 1.2 modulus of sodium silicate and 6% concentration of alkalis under the circumstance of 60°C curing for 28 days.

scholarly journals Evaluation of the Hydration Characteristics and Anti-Washout Resistance of Non-Dispersible Underwater Concrete with Nano-SiO2 and MgO

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1328
Author(s):  
In Kyu Jeon ◽  
Byeong Hun Woo ◽  
Dong Ho Yoo ◽  
Jae Suk Ryou ◽  
Hong Gi Kim
Keyword(s):  
Compressive Strength ◽  
Fine Particles ◽  
Setting Time ◽  
Peak Time ◽  
Nano Sio2 ◽  
Setting Times ◽  
Slump Flow ◽  
Compressive Strength Test ◽  
Underwater Concrete ◽  
Hydration Characteristics

In this paper, the effect of nano-SiO2 (NS) and MgO on the hydration characteristics and anti-washout resistance of non-dispersible underwater concrete (UWC) was evaluated. A slump flow test, a viscosity test, and setting time measurement were conducted to identify the impacts of NS and MgO on the rheological properties of UWC. The pH and turbidity were measured to investigate the anti-washout performance of UWC mixes. To analyze the hydration characteristics and mechanical properties, hydration heat analysis, a compressive strength test, and thermogravimetric analyses were conducted. The experimental results showed that the fine particles of NS and MgO reduced slump flow, increased viscosity, and enhanced the anti-washout resistance of UWC. In addition, both NS and MgO shortened the initial and final setting times, and the replacement of MgO specimens slightly prolonged the setting time. NS accelerated the peak time and increased the peak temperature, and MgO delayed the hydration process and reduced the temperature due to the formation of brucite. The compressive results showed that NS improved the compressive strength of the UWC, and MgO slightly decreased the strength. The addition of NS also resulted in the formation of extra C–S–H, and the replacement of MgO caused the generation of a hydrotalcite phase.

scholarly journals Mechanical properties of fly ash and blast furnace slag based alkali activated concrete using high silica modulus activator

2021 ◽  
Vol 309 ◽  
pp. 01202
Author(s):  
G.V.V. Satyanarayana ◽  
Kaparaboina Greeshma
Keyword(s):  
Blast Furnace ◽  
Fly Ash ◽  
Blast Furnace Slag ◽  
Setting Time ◽  
High Strength ◽  
Cementitious Materials ◽  
Split Tensile Strength ◽  
High Silica ◽  
Furnace Slag ◽  
Alkali Activated

The alternative to cement is grabbing attention of inventors due to the numerous advantages with their usage. Fly Ash (FA) and Blast furnace slag (BFS) are abundantly available in bi product form. There is heavy problem in disposal and land availability for industries. So many studies are going on to reduce these problems by usage as cementitious materials in concrete adding advantages towards green concrete. It is developed that Alkali activated flyash concrete has high strength, high acid resistance and heat resistance where as Alkali activated slag concrete has rapid setting time, high strength, impermeable and improved fire resistance. In this study FA and BFS are activated with high silica modulus activator with different activator/binder ratios and binder contents. The alkali activated FA-BFS concrete is verified for workability, compressive strength, split tensile strength, and flexural strength.

Roles of Calcium in Geopolymer Containing Paper Mill Sludge Ash

2018 ◽  
Vol 917 ◽  
pp. 311-315 ◽  
Author(s):  
Norbaizurah Rahman ◽  
Andri Kusbiantoro ◽  
Nabilah Mamat ◽  
Khairunisa Muthusamy ◽  
Mohd Mustafa Al Bakri Abdullah
Keyword(s):  
Fly Ash ◽  
Mechanical Strength ◽  
Sodium Hydroxide Solution ◽  
Setting Time ◽  
Sodium Silicate Solution ◽  
Paper Mill ◽  
Curing Temperature ◽  
Paper Mill Sludge ◽  
Degree Of Reaction ◽  
Sludge Ash

High amount of calcium oxide (CaO) in source material is known to positively influence the mechanical strength of fly ash based geopolymer. This study was conducted to investigate the suitability of paper mill sludge ash (PMSA) to partially replace fly ash in geopolymer mortar based on its degree of reaction. Fly ash was activated by a combination of sodium silicate solution and 6 M sodium hydroxide solution. The mixtures were designed to replace fly ash content with PMSA at 5%, 10% and 15% (by weight of fly ash). To observe its effect on the mechanical strength, the specimens were cured in three different temperatures, which are 30°C, 60°C and 90°C for 24 hours. After 24 hours, the hardened specimens were demoulded and placed at room temperature until the testing days. Measurement on fresh geopolymer properties was conducted with setting time and flowability tests, while degree of reaction tests was conducted on the hardened specimen. Based on the results, 5% PMSA demonstrated superior degree of reaction than other mixtures, particularly at higher curing temperature.

scholarly journals Effect of the Sodium Silicate Modulus and Slag Content on Fresh and Hardened Properties of Alkali-Activated Fly Ash/Slag

Minerals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 15 ◽  
Author(s):  
Xiaowei Ouyang ◽  
Yuwei Ma ◽  
Ziyang Liu ◽  
Jianjun Liang ◽  
Guang Ye
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Pore Structure ◽  
Heat Release ◽  
Setting Time ◽  
Heat Evolution ◽  
Reaction Products ◽  
Hardened Properties ◽  
Alkali Activated ◽  
Slag Content

This paper presents the results of an experimental study performed to investigate the effect of activator modulus (SiO2/Na2O) and slag addition on the fresh and hardened properties of alkali-activated fly ash/slag (AAFS) pastes. Four activator moduli (SiO2/Na2O), i.e., 0.0, 1.0, 1.5, and 2.0, and five slag-to-binder ratios, i.e., 0, 0.3, 0.5, 0.7, 1.0, were used to prepare AAFS mixtures. The setting time, flowability, heat evolution, compressive strength, microstructure, and reaction products of AAFS pastes were studied. The results showed that the activator modulus and slag content had a combined effect on the setting behavior and workability of AAFS mixtures. Both the activator modulus and slag content affected the types of reaction products formed in AAFS. The coexistence of N–A–S–H gel and C–A–S–H gel was identified in AAFS activated with high pH but low SiO2 content (low modulus). C–A–S–H gel had a higher space-filling ability than N–A–S–H gel. Thus, AAFS with higher slag content had a finer pore structure and higher heat release (degree of reaction), corresponding to a higher compressive strength. The dissolution of slag was more pronounced when NaOH (modulus of 0.0) was applied as the activator. The use of Na2SiO3 as activator significantly refined the pores in AAFS by incorporating soluble Si in the activator, while further increasing the modulus from 1.5 to 2.0 prohibited the reaction process of AAFS, resulting in a lower heat release, coarser pore structure, and reduced compressive strength. Therefore, in view of the strength and microstructure, the optimum modulus is 1.5.

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