scholarly journals Influence of Potassium-Based Alkaline Electrolyzed Water on Hydration Process and the Properties of Cement-Based Materials with Fly Ash

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6956
Author(s):  
Zexin Yu ◽  
Zixi Xie ◽  
Tianyu Zhang ◽  
Gongbing Yue ◽  
Haibao Liu ◽  
...  
Keyword(s):  
Fly Ash ◽  
Cement Hydration ◽  
Ph Value ◽  
Hydration Process ◽  
Hydration Reaction ◽  
Electrolyzed Water ◽  
Ordinary Water ◽  
Fly Ash Concrete ◽  
Cement Based Materials ◽  
Alkaline Electrolyzed Water

Alkaline electrolyzed water, a kind of clean green water with excellent characteristics such as high activity, strong alkalinity, high ion penetrating ability, electrical charge, and good molecule adsorption, was significant to the resource utilization of industrial fly ash waste. This paper studies highly active potassium-based alkaline electrolyzed water′s impact, compared with ordinary water, on the cement hydration process using microstructural methods such as a hydration heat test, differential thermal analysis, X-ray diffraction (XRD) pattern, and Scanning electron microscope (SEM) image analysis. Fly ash cement-based materials were first prepared with alkaline electrolyzed water as the mixing water. The alkaline electrolyzed water’s influence on fly ash paste workability and the mechanical properties of fly ash mortar for varying fly ash proportions were ratified. Then alkaline electrolyzed water with the best pH value was selected to prepare fly ash concrete, and its durability was studied. The test results showed that it is feasible to increase the utilization rate of fly ash by using alkaline electrolyzed water. Furthermore, it promoted the process of cement hydration, increased the rate of the hydration reaction, and the promotion effect increased with the increase in pH value of the alkaline electrolyzed water, and also promoted the effective decomposition of the vitreous shell of fly ash to stimulate its early activity. Concurrent tests with ordinary water paste showed that the water requirement for normal consistency and setting time with alkaline electrolyzed water paste were significantly less. Alkaline electrolyzed water also solved the problem related to the low early strength of fly ash mortar. Furthermore, using alkaline electrolyzed water with an optimum pH value of 11.5 to prepare fly ash concrete effectively reduced concrete′s carbonation depth and carbonation rate and lessened the chloride ion migration coefficient.

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

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.

Research on the Variation of pH Value of the Ordinary Concrete and Fly Ash Concrete in the Carbonation Process

2011 ◽  
Vol 374-377 ◽  
pp. 1934-1937 ◽  
Author(s):  
Guang Zheng Qi ◽  
Di Tao Niu ◽  
Cheng Fang Yuan ◽  
Fu Zhen Duan
Keyword(s):  
Fly Ash ◽  
High Performance ◽  
Ph Value ◽  
Economic Benefits ◽  
Carbonation Depth ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Ordinary Concrete ◽  
Fly Ash Concrete ◽  
Carbonation Process

The accelerated carbonation test was carried out for the ordinary concrete and fly ash concrete. Influences of water-cement ratio, carbonation age and fly ash content on pH value were researched. The results show that carbonation depth, including incomplete carbonized zone, can be effectively reduced by reducing water-cement ratio. So lower water-cement ratio means high performance of resistance of carbonate. The use of fly ash can optimize concrete pore morphology, it’s beneficial for anti-carbonation. However, It disadvantageous to anti-carbonation because of less carbonation material. By taking appropriate mixture of fly ash we can not only enhance the anti-carbonation ability of concrete, but also reduce the use of cement to get well economic benefits.

Effect of High-Calcium Fly Ash on Activity Index and Hydration Process of Phosphorous Slag Powders

2016 ◽  
Vol 873 ◽  
pp. 105-109
Author(s):  
Cai Yu Li ◽  
Lin Yang ◽  
Jian Xin Cao ◽  
Qiu Mei Liu
Keyword(s):  
Fly Ash ◽  
Activity Index ◽  
Ash Content ◽  
Hydration Process ◽  
Hydration Reaction ◽  
High Calcium ◽  
High Calcium Fly Ash ◽  
Phosphorous Slag

Effect of the dosage of high-calcium fly ash and fineness of phosphorous slag powders on activity index of phosphorous slag powders was explored. The hydration samples of phosphorous slag powders with high-calcium fly ash content were analyzed using XRD, DSC-TG and SEM. The results showed that activity index of phosphorous slag powders increased and then decreased with the dosage of high-calcium fly ash increasing. When the dosages of high-calcium fly ash were 15%-20%, activity indexes of phosphorous slag powders were above 1. With fineness of phosphorous slag powders increasing with ranges from 370 to 440 m2·kg-1, activity indexes of phosphorous slag powders increased with ranges from 1.028 to 1.174. High-calcium fly ash accelerated the hydration reaction of phosphorous slag powders, and promoted the increase in the strength of phosphorous slag powders glue-sand.

scholarly journals Investigating the Role of Fly Ash and Silica Fume in the Cement Hydration Process

2016 ◽  
Vol 9 (1) ◽  
pp. 134-145
Author(s):  
Lucas Suarez ◽  
Taher M. Abu-Lebdeh ◽  
Miguel Picornell ◽  
Sameer A. Hamoush
Keyword(s):  
Fly Ash ◽  
Silica Fume ◽  
Cement Hydration ◽  
Hydration Process

Reaction Products in Fly Ash Concrete

1984 ◽  
Vol 43 ◽  
Author(s):  
Mark D. Baker ◽  
Joakim G. Laguros
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Calcium Hydroxide ◽  
Setting Time ◽  
Heat Of Hydration ◽  
Hydration Process ◽  
Reaction Products ◽  
Fly Ash Concrete ◽  
Xrd Studies ◽  
One Year

AbstractThe setting and strength gaining process of PC concrete containing Class C high lime fly ash were related to the reaction products identified using XRD and SEM. Four fly ash concrete mixes (20, 30, 40, and 50 percent replacement of cement by fly ash) and similar paste mixes were compared to control mixes for curing periods up to one year. Setting time and early compressive strength were adversely affected by the addition of fly ash. Beyond one week all of the fly ash concrete mixes gained strength at a faster rate than the corresponding control mixes. XRD studies suggest that the retardation mechanism may be associated with the high levels of ettringite formed early in the hydration process and its conversion to monosulfoaluminate. A decrease in the level of calcium hydroxide, typical of pozzolanic activity, was not in evidence. SEM micrographs of fly ash spheres in concrete at the various stages of hydration reveal an intricate crystal framework. A simple heat of hydration test is presented which helps explain the strength gains observed.

High Performance Concrete with High Volume Fly Ash

2006 ◽  
Vol 302-303 ◽  
pp. 470-478 ◽  
Author(s):  
Jian Hua Wu ◽  
Xin Cheng Pu ◽  
Fang Liu ◽  
Chong Wang
Keyword(s):  
Fly Ash ◽  
High Performance ◽  
High Performance Concrete ◽  
Ph Value ◽  
High Volume ◽  
Volume Stability ◽  
Fly Ash Concrete ◽  
High Volume Fly Ash ◽  
Large Dosage ◽  
Technical Measures

The emphasis of this paper is how to increase the 3-day and 28-day strength of high volume fly ash concrete. By some technical measures, such as improving the initial pozzolanic activity (3 day) of fly ash and decreasing the ratio of water to binding material and increasing the total dosage of binding materials, a concrete with the ratio of fly ash to binding materials between 50 %-70 % can be made. The fluidity of the concrete mix with large dosage of fly ash is very good and the strength at 3 day and 28 day are more than 42.5 MPa and 85 MPa respectively. By determining the pH value and the calcium hydrate content of the paste with large dosage of fly ash and accelerated carbonation test, it is shown that the resistance of the concrete to carbonization has been improved. The concrete with large dosage fly ash has good volume stability.

scholarly journals High-volume Fly Ash Concrete for Pavements Findings: Volume 1

2021 ◽  
Author(s):  
Aniruddha Baral ◽  
◽  
Jeffrey Roesler ◽  
M. Ley ◽  
Shinhyu Kang ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Air Entrainment ◽  
High Volume ◽  
Mix Design ◽  
Hydration Reaction ◽  
Index Test ◽  
Fly Ash Concrete ◽  
High Volume Fly Ash ◽  
Foam Index

High-volume fly ash concrete (HVFAC) has improved durability and sustainability properties at a lower cost than conventional concrete, but its early-age properties like strength gain, setting time, and air entrainment can present challenges for application to concrete pavements. This research report helps with the implementation of HVFAC for pavement applications by providing guidelines for HVFAC mix design, testing protocols, and new tools for better quality control of HVFAC properties. Calorimeter tests were performed to evaluate the effects of fly ash sources, cement–fly ash interactions, chemical admixtures, and limestone replacement on the setting times and hydration reaction of HVFAC. To better target the initial air-entraining agent dosage for HVFAC, a calibration curve between air-entraining dosage for achieving 6% air content and fly ash foam index test has been developed. Further, a digital foam index test was developed to make this test more consistent across different labs and operators. For a more rapid prediction of hardened HVFAC properties, such as compressive strength, resistivity, and diffusion coefficient, an oxide-based particle model was developed. An HVFAC field test section was also constructed to demonstrate the implementation of a noncontact ultrasonic device for determining the final set time and ideal time to initiate saw cutting. Additionally, a maturity method was successfully implemented that estimates the in-place compressive strength of HVFAC through wireless thermal sensors. An HVFAC mix design procedure using the tools developed in this project such as the calorimeter test, foam index test, and particle-based model was proposed to assist engineers in implementing HVFAC pavements.

Effects of micro-environmental climate on the carbonation depth and the pH value in fly ash concrete

2018 ◽  
Vol 181 ◽  
pp. 309-317 ◽  
Author(s):  
Cai-feng Lu ◽  
Wei Wang ◽  
Qing-tao Li ◽  
Ming Hao ◽  
Yuan Xu
Keyword(s):  
Fly Ash ◽  
Ph Value ◽  
Carbonation Depth ◽  
Fly Ash Concrete

Effect of Shrinkage Reducing Admixture on Shrinkage and Crack Properties of Cement Based Materials

2019 ◽  
Vol 814 ◽  
pp. 387-392
Author(s):  
Yan Yao ◽  
Hao Wu ◽  
Ling Wang ◽  
Rui Jun Gao
Keyword(s):  
Calcium Hydroxide ◽  
Temperature Rise ◽  
Cement Hydration ◽  
Adiabatic Temperature ◽  
Hydration Heat ◽  
Hydration Process ◽  
Cement Pastes ◽  
Adiabatic Temperature Rise ◽  
Cement Based Materials ◽  
Shrinkage Reducing Admixture

In order to improve the dimensional stability of cement based materials, the effects of shrinkage reducing admixture (SRA) dosage on the shrinkage and crack properties of cement based materials were investigated. The hydration process of the cement pastes was tracked and monitored by hydration calorimeter and adiabatic temperature rise apparatus respectively. The action mechanism of SRA on hydration process of the cement based materials was characterized by differential scanning calorimeter (DSC). The shrinkage and crack results show that the ability of resist cracking of concrete can be effectively improved by SRA. The results of hydration calorimeter and adiabatic temperature rise indicate that the appear time of hydration temperature peak at early age was delayed and the development of hydration heat changed gently at later period by doped SRA. The results of DSC show that the release amount of hydration heat and the production of early calcium hydroxide can be delayed by SRA, however, there has no effects of SRA on the formation of cement hydration products like calcium hydroxide at the later period.

scholarly journals Effect of Nano-Magnesium Oxide on the Expansion Performance and Hydration Process of Cement-Based Materials

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3766
Author(s):  
Yuxun Ye ◽  
Yanming Liu ◽  
Tao Shi ◽  
Zhuojun Hu ◽  
Lei Zhong ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Fly Ash ◽  
Cement Paste ◽  
Hydration Process ◽  
Obvious Effect ◽  
Continuous Precipitation ◽  
Long Term Stability ◽  
Cement Based Materials

Many scholars are concerned about the effect of nano-MgO as an expansion agent on the performance of cement-based materials at an early age, but over a long period less attention is paid to expansion stability and mechanical properties. This article examines the influence of nano-MgO on the long-term consistency, fluidity, expansion stability, hydration, and mechanical properties of 30% fly ash cement-based materials and improves research into nano-MgO as an expansion agent. Expansion performance, flexural and compressive strength, and stability after boiling and autoclave treatment were tested for specimens mixed with a 2, 4, 6, 8 and 10% cementitious material mass of nano-MgO. X-ray diffraction (XRD) and scanning electronic microscopy (SEM) were employed to study their hydration process and microstructure. The results showed that nano-MgO had an obvious effect on the consistency, fluidity and expansion performance of cement paste. After curing in water for 365 days and autoclaving thereafter, the hydration of nano-MgO was relatively complete. The volumetric expansion pressure of the magnesium hydroxide (Mg(OH)2) crystals and the crystallization pressure generated after their continuous precipitation were the main reasons for the expansion of the slurry. Nano-MgO improved the microstructure of cement paste and significantly enhanced its long-term flexural strength and compressive strength. When the content of nano-MgO was less than 10%, the cement with 30% fly ash had good long-term stability with the potential to compensate for the shrinkage of large-volume concrete.

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