POZZOLANIC REACTION AND STRENGTH DEVELOPMENT OF CEMENT PASTE AND MORTAR USING FLY ASH

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

Download Full-text

A study on pozzolanic reaction of fly ash cement paste activated by an injection of alkali solution

Construction and Building Materials ◽

10.1016/j.conbuildmat.2015.06.046 ◽

2015 ◽

Vol 94 ◽

pp. 28-34 ◽

Cited By ~ 16

Author(s):

Phuong Trinh Bui ◽

Yuko Ogawa ◽

Kenichiro Nakarai ◽

Kenji Kawai

Keyword(s):

Fly Ash ◽

Cement Paste ◽

Pozzolanic Reaction ◽

Alkali Solution

Download Full-text

Effect of internal alkali activation on pozzolanic reaction of low-calcium fly ash cement paste

Materials and Structures ◽

10.1617/s11527-015-0703-6 ◽

2015 ◽

Vol 49 (8) ◽

pp. 3039-3053 ◽

Cited By ~ 7

Author(s):

Phuong Trinh Bui ◽

Yuko Ogawa ◽

Kenichiro Nakarai ◽

Kenji Kawai

Keyword(s):

Fly Ash ◽

Cement Paste ◽

Pozzolanic Reaction ◽

Alkali Activation ◽

Low Calcium

Download Full-text

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

The Journal of Solid Waste Technology and Management ◽

10.5276/jswtm/2021.70 ◽

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.

Download Full-text

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

MRS Proceedings ◽

10.1557/proc-136-281 ◽

1988 ◽

Vol 136 ◽

Cited By ~ 2

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.

Download Full-text

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

MRS Proceedings ◽

10.1557/proc-137-437 ◽

1988 ◽

Vol 137 ◽

Cited By ~ 3

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.

Download Full-text