scholarly journals EXPERIMENTAL EXPLANATION OF COMPACTING EFFECT ON HYDRATION PHASES AND STRENGTH DEVELOPMENT MECHANISM DERIVED FROM POZZOLANIC REACTION OF FLY ASH

2007 ◽  
Vol 63 (1) ◽  
pp. 52-65 ◽  
Author(s):  
Takeshi YAMAMOTO ◽  
Tsutomu KANAZU
Keyword(s):  
Fly Ash ◽  
Pozzolanic Reaction ◽  
Strength Development ◽  
Hydration Phases ◽  
Development Mechanism

Fly-Ash Concretes of 50% of the Replacement Ratio to Reduce the Cracking in Concrete Structures

2013 ◽  
Vol 405-408 ◽  
pp. 2665-2670 ◽  
Author(s):  
Ming Jie Mao ◽  
Qiu Ning Yang ◽  
Wen Bo Zhang ◽  
Isamu Yoshitake
Keyword(s):  
Fly Ash ◽  
Concrete Structures ◽  
High Volume ◽  
Pozzolanic Reaction ◽  
Strength Development ◽  
Early Age ◽  
Replacement Ratio ◽  
Fly Ash Concrete ◽  
Massive Concrete ◽  
Normal Strength

Fly-ash concrete used in massive concrete structure has superior advantages to reduce hydration heat. On the other hand, the fly-ash concrete has negative property of low strength development at early age because pozzolanic reaction of fly-ash activates at mature age, such as after 28 days. To investigate these characteristics of fly-ash used in concrete, the present study discusses thermal cracking possibility of fly-ash concrete by using FE analysis software. The present study employs prediction formulae proposed by Zhang and Japanese design code in the simulations. The objects in this study are normal strength concrete mixed of fly-ash up to 50% of replacement ratio to cement. The comparative investigations show that temperature effect is more significant than strength development at early age. Based on the analytical study, high volume fly-ash concretes of 30-50% of the replacement ratio can be concluded as effective and useful materials to reduce the cracking possibility in massive concrete structures. Keywords-Fly-ash concrete; Early Age, Prediction Formulae for Strength; Thermal Stress Analysis

Beneficiation of Waste Fly Ash and Phosphogypsum— The Development of a New Material

2021 ◽  
Vol 47 (1) ◽  
pp. 70-81
Author(s):  
Tebogo Mashifana ◽  
Felix Okonta ◽  
Freeman Ntuli
Keyword(s):  
Fly Ash ◽  
Citric Acid ◽  
Chemical Composition ◽  
Detrimental Effect ◽  
Pozzolanic Reaction ◽  
Building Construction ◽  
Strength Development ◽  
Material Strength ◽  
Minimum Requirements ◽  
New Material

Waste phosphogypsum (PG) was treated with citric acid, oxalic acid, sodium carbonate and sodium bicarbonate to reduce the contaminants in the material and render the material applicable for other applications. The chemical composition revealed that the material was laden with contaminants such as fluorides and phosphorous which have a detrimental effect on the development of material strength. Citric acid was the best leaching reagent to reduce the radionuclides in PG and it was selected as the leaching reagent to treat PG. The chemical composition of both the raw PG and treated PG showed that there was insufficient pozzolans in the materials to trigger the pozzolanic reaction for strength development. Therefore the PG had to be stabilized with fly ash and lime. The optimum mix ratio of the raw PG composite that yielded the highest UCS was made up of 50% raw PG and 30% FA, while 30% treated PG and 50% FA yielded the highest strength. The variation in strengths between the raw and treated PG was due to differences in the microstructure of the materials and the particle size distribution. The strength obtained met the minimum requirements for the material to be used in bulk as building construction elements.

Evidence for Minimal Pozzolanic Reaction in a Fly Ash Cement During the Period of Major Strength Development

1988 ◽  
Vol 136 ◽  
Author(s):  
Sidney Diamond ◽  
Qizhong Sheng ◽  
Jan Olek
Keyword(s):  
Fly Ash ◽  
Plain Concrete ◽  
Pozzolanic Reaction ◽  
Strength Development ◽  
Inert Material ◽  
Microscope Examination ◽  
Intimate Contact ◽  
Cement Pastes ◽  
Minimal Evidence ◽  
Water Contents

ABSTRACTStrengths developed in fly ash concretes usually equal or exceed that of similar plain concrete after a few months, with much of the response usually attributed to “pozzolanic” reaction between ash and secondary calcium hydroxide (CH). The CH contents of pastes made with five different fly ashes were determined by DTA for periods up to six months. The CH contents found did not decrease notably over the period, and were substantially identical to that expected for plain cement pastes diluted with the same amount of inert material as the amount of fly ash used. Scanning electron microscope examination of the pastes showed only minimal evidence of reaction even up to 1 year of age, although many fly ash grains were in intimate contact with CH. Non-evaporable water contents of the fly ash pastes were substantially higher than expected at each age, suggesting that the fly ash promoted more complete cement hydration or that the hydration products formed bound substantially greater amounts of water than plain cement paste ordinarily does.

Evidence for Minimal Pozzolanic Reaction in a Fly Ash Cement during the Period of Major Strength Development

1988 ◽  
Vol 137 ◽  
Author(s):  
Sidney Diamond ◽  
Qizhong Sheng ◽  
Jan Olek
Keyword(s):  
Fly Ash ◽  
Plain Concrete ◽  
Pozzolanic Reaction ◽  
Strength Development ◽  
Inert Material ◽  
Microscope Examination ◽  
Intimate Contact ◽  
Cement Pastes ◽  
Minimal Evidence ◽  
Water Contents

AbstractStrengths developed in fly ash concretes usually equal or exceed that of similar plain concrete after a few months, with much of the response usually attributed to “pozzolanic” reaction between ash and secondary calcium hydroxide (CH). The CH contents of pastes made with five different fly ashes were determined by DTA for periods up to six months. The CH contents found did not decrease notably over the period, and were substantially identical to that expected for plain cement pastes diluted with the same amount of inert material as the amount of fly ash used. Scanning electron microscope examination of the pastes showed only minimal evidence of reaction even up to 1 year of age, although many fly ash grains were in intimate contact with CH. Non-evaporable water contents of the fly ash pastes were substantially higher than expected at each age, suggesting that the fly ash promoted more complete cement hydration or that the hydration products formed bound substantially greater amounts of water than plain cement paste ordinarily does.

scholarly journals Resilient performance of expansive subgrades stabilized with nanosized and activated fly ash

2021 ◽  
Author(s):  
Frank Ikechukwu Aneke ◽  
Mohamed Mostafa Hassan
Keyword(s):  
Fly Ash ◽  
Resilient Modulus ◽  
Morphological Changes ◽  
Expansive Soils ◽  
Pozzolanic Reaction ◽  
Exchange Capacity ◽  
Degree Of Saturation ◽  
Strength Development ◽  
High Plasticity ◽  
Test Result

Subgrades across arid and semi-arid region are known for its random swelling, with high plasticity due to moisture infiltration of the pavement structures. Subgrades materials are significantly influenced by the cahnges in degree of saturation, which is unavoidable. Studies in the past, have reported several positive results on the stabilization of expansive soils with additives like lime, cement, fly ash, etc. In this study, resilient performance of expansive subgrades treated with 0.5%, 1.0%, 1.5% and 2.0% of nanosized and activated fly ash (NFA and AFA) is presented. Series of cation exchange capacity tests, zero swelling tests (ZST) and resilient modulus (M_R ) tests were performed to study the effects of NFA and AFA on resilient modulus (M_R) and swelling index of the subgrades material respectively. Scanning electron microscopy (SEM) tests was conducted to evaluate the morphological changes in the subgrades, and compounds responsible for resilient strength development. The result showed that, NFA and AFA inclusions in the treatment of expansive subgrades caused an increase in resilient strength and decrease in swelling stress to a limiting stabilizer content of 0.5% and 1.0% beyond which, the resilient modulus values increased triggering a significant decrease in swelling stress. The test result revealed that the reduction was caused by the pozzolanic reaction between the stabilizers and available moisture required for full completion of pozzolanic process. Based on the test result, nano-fly ash exhibite high potential in improving resilient strength and reducing swelling stress to 58.7% and 63% respectively on the average compared to activated fly ash. This study suggest a feasible solution to improve the quality and performance of expansive subgrades.

Effect of Thermal Environment at Early Age on Hydration Phases Composition and Strength Development of Concrete Containing Fly Ash

2010 ◽  
Vol 168-170 ◽  
pp. 582-588
Author(s):  
Feng Chen Zhang ◽  
De Jian Shen ◽  
Ji Kai Zhou ◽  
Zhong Hua Li
Keyword(s):  
Tensile Strength ◽  
Fly Ash ◽  
Thermal Environment ◽  
Ash Content ◽  
Splitting Tensile Strength ◽  
Curing Temperature ◽  
Strength Development ◽  
Early Age ◽  
Mass Concrete ◽  
Hydration Phases

Cement hydration at early age is sometimes in a certain thermal environment probably caused by hydration heat of mass concrete as well as cement productions curing at high temperature. And phases composition and strength development in thermal environment are commonly different from those in normal curing conditions. Phases composition and strength development of concrete containing different fly ash content curing in different thermal environment are studied in this paper. Experimental results show that compressive strengths of concrete with 0.3 water to binder ratio increase with the increase of curing temperature. Splitting tensile strength of concrete not containing any fly ash curing at about 50 is the highest among those curing at temperature between 40 and 80 . For concrete with different fly ash content, splitting tensile strengths increase approximately with the increse of curing temperature. Dehydration of ettringite and formation of monosulfate solid solution and AFm at higher temperature perhaps relate to the development of concrete splitting tensile strength along with different curing temperature. Adding fly ash to binder, curing temperature at which hydration phases change occurs is raised, which helps to explain that splitting tensile strengths of concrete with different fly ash content decrease little with the increase of curing temperature between 60 and 80 .

Strength Development and Microstructural Investigation of Calcium Carbide Residue and Fly Ash Prepared with Optimized Alternative Green Binders

2021 ◽  
Vol 904 ◽  
pp. 429-434
Author(s):  
Papantasorn Manprom ◽  
Phongthorn Julphunthong ◽  
Pithiwat Tiantong ◽  
Tawat Suriwong
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Raw Materials ◽  
Extended Period ◽  
Calcium Carbide ◽  
Pozzolanic Reaction ◽  
Strength Development ◽  
Chemical Compositions ◽  
Microstructural Investigation ◽  
Calcium Carbide Residue

The development of new environmentally friendly binder from calcium carbide residue and fly ash wastes were investigated in this study. The key point of this work is difference to several previous investigations in that the optimized mixture proportion of the raw materials were calculated based on their chemical composition and their reaction. The compressive strength development over the curing age was also compared with reference mortar created with OPC binder. Mortar cubes were cast from the mix containing the calcium carbide residue and fly ash, at the optimized ratio. The compressive strength of the mortar was then monitored over an extended period: at 56 days it was 10.66 MPa, which is approximately 47% of the reference mortar. The morphologies and chemical compositions of the developed mortar showed the presence of spherically shaped of unreacted fly ash powder particles embedded in a cement C–S–H gel resulting from the pozzolanic reaction of raw materials.

The Effect of Curing Time on Compressive Strength of Composite Cement Concrete

2012 ◽  
Vol 204-208 ◽  
pp. 4105-4109 ◽  
Author(s):  
Md. Alhaz Uddin ◽  
Mohammed Jameel ◽  
Habibur Rahman Sobuz ◽  
Noor Md. Sadiqul Hasan ◽  
Md. Shahinul Islam ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Cement Content ◽  
Pozzolanic Reaction ◽  
Strength Development ◽  
Ambient Conditions ◽  
Cement Concrete ◽  
Composite Cement ◽  
Compressive Strength Development ◽  
Curing Condition

The effect of curing condition of five different composition of Portland composite cement (PCC) and ordinary Portland cement (OPC) were investigated in this study. Compressive strength development of five different concrete types has been investigated in terms of cement content and curing duration. From the experimental observation, it is found that the early age strength of concrete made with PCC is lower than that of concrete made with OPC due to the presence of fly ash in PCC which is responsible for the pozzolanic reaction. The continued pozzolanic activity of fly ash contributes to increase strength gain at later ages at continued curing condition. It is also found that drying ambient conditions reduction of the strength potential of concrete made with PCC because the secondary (pozzolanic) reaction fails to contribute to the development of strength.

Study on Strength Development of High Strength Concrete Containing Alccofine and Fly-Ash

2012 ◽  
Vol 2 (3) ◽  
pp. 102-104 ◽  
Author(s):  
Suthar Sunil B ◽  
◽  
Dr. (Smt.) B. K. Shah Dr. (Smt.) B. K. Shah
Keyword(s):  
Fly Ash ◽  
High Strength Concrete ◽  
High Strength ◽  
Strength Development ◽  
Strength Concrete
Sign in / Sign up

Export Citation Format

Share Document