Technical Note on the Determination of Free Lime (CaO) in Fly Ash

1984 ◽  
Vol 43 ◽  
Author(s):  
Scott Schlorholtz ◽  
Turgut Demirel
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Recent Work ◽  
Technical Note ◽  
Fly Ashes ◽  
Major Drawback ◽  
Free Lime ◽  
Chemical Test ◽  
Lime Content

AbstractMany fly ashes contain free lime (CaO) and periclase (MgO) [1,2]. These two compounds, when present in excessive amounts, are known to cause soundness problems in portland cement [3,4]. Recent work [5] has indicated that the autoclave expansion of portland cement-fly ash pastes is related to the concentration of CaO and MgO in a given paste, free lime typically being more detrimental than periclase. The purpose of this technical note is to briefly discuss two methods that are currently available for determining the free lime content of fly ash, and to suggest a supplement to the autoclave test (described in ASTM C 151). The major drawback of the autoclave test is that it requires approximately two days to complete and therefore it would be helpful to have a quick chemical test that could be used to indicate the soundness properties of a given fly ash.

scholarly journals Lightweight masonry block without Portland cement

2021 ◽  
Vol 26 (5) ◽  
pp. 945-953
Author(s):  
Paki Turgut ◽  
Mehmet Can Alas ◽  
Muhammed Arif Gurel
Keyword(s):  
Thermal Conductivity ◽  
Fly Ash ◽  
Portland Cement ◽  
Chemical Properties ◽  
Waste Materials ◽  
Fly Ashes ◽  
Free Lime ◽  
The World ◽  
Belt Conveyors ◽  
Lightweight Masonry Block

ABSTRACT Huge amounts of fly ash - a substance that does not conform to the ASTM C618 classification due to its chemical properties - have been abandoned in landfills around the world, despite their self-cementing property. It has not been used in concrete making applications due to its large amounts of free lime and sulfate contents. The fly ash in these plants is dumped in landfills, causing serious environmental hazards. Fly ash is disposed to the landfills by belt conveyors after being humidified with water. Therefore, the fly ashes humidified in the landfill areas are hydrated in nature. This hydration is further intensified in landfills by rain and snow. Thus, the free lime content of fly ash decreases due to its long hydration process. In this work, the lightweight masonry blocks were produced by mixing normal and hydrated fly ashes or normal, hydrated fly ash and lime without Portland cement. The compressive strength, water absorption, sorptivity, density, porosity, and thermal conductivity values of the samples produced were determined. The results obtained from these tests showed that lightweight masonry blocks could be produced by using these waste materials in building applications.

Low Cement/High Fly Ash Concretes: Their Properties and Response to Chemical Admixtures

1987 ◽  
Vol 113 ◽  
Author(s):  
V. H. Dodson
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Calcium Hydroxide ◽  
Pozzolanic Reaction ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Fly Ashes ◽  
Chemical Admixtures ◽  
Reaction With Water

ABSTRACTIn practice, the amount of fly ash added to portland cement concrete varies depending upon the desired end properties of the concrete. Generally, when a given portland cement concrete is redesigned to include fly ash, between 10 and 50% of the cement is replaced by a volume of fly ash equal to that of the cement. Sometimes as much as twice the volume of the cement replaced, although 45.4 kg (100 lbs) of cement will only produce enough calcium hydroxide during its reaction with water to react with about 9 kg (20 lbs) of a typical fly ash. The combination of large amounts of certain fly ashes with small amounts of portland cement in concrete has been found to produce surprisingly high compressive strengths, which cannot be accounted for by the conventional “pozzolanic reaction”. Ratios of cement to fly ash as high as 1:15 by weight can produce compressive strengths of 20.7 MPa (3,000 psi) at I day and over 41.4 MPa (6,000 psi) at 28 days. Methods of identifying these “hyperactive” fly ashes along with some of the startling results, with and without chemical admixtures are described.

Characterization of Canadian fly ashes and their relative performance in concrete

1987 ◽  
Vol 14 (5) ◽  
pp. 667-682 ◽  
Author(s):  
G. G. Carette ◽  
V. M. Malhotra
Keyword(s):  
Fly Ash ◽  
Setting Time ◽  
Air Entrainment ◽  
Relative Performance ◽  
Hardened Concrete ◽  
Freezing And Thawing ◽  
Fly Ashes ◽  
Wide Range ◽  
Pozzolanic Properties

Eleven Canadian fly ashes were characterized and evaluated for their relative performance in concrete. Characterization included the determination of mineralogical composition, chemical composition, physical characteristics, and pozzolanic properties. The relative performance of each fly ash in concrete was evaluated through determination of the following properties of fresh and hardened concrete: slump, air content, bleeding, setting time, strength, modulus of elasticity, drying shrinkage, creep, and freezing-and-thawing resistance.The results indicate a wide range of chemical, physical, and pozzolanic properties for the fly ashes investigated. In spite of this, all the fly ashes studied are shown to be suitable for use in concrete. They affect, however, the properties of fresh and hardened concrete in different ways, and this should be taken into account when proportioning concrete containing these fly ashes. Key words: fly ash, concrete, pozzolanic activity index, bleeding, setting time, air-entrainment, strength, creep, shrinkage, freezing and thawing.

Retardation Effects in the Hydration of Cement-Fly Ash Pastes

1984 ◽  
Vol 43 ◽  
Author(s):  
Michael W. Grutzeck ◽  
Wei Fajun ◽  
Della M. Roy
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Solid Phase ◽  
Heat Of Hydration ◽  
Type I ◽  
Fly Ashes ◽  
Solution Composition ◽  
Early Hydration ◽  
High Calcium ◽  
Phase Characterization

AbstractThe hydration of high-calcium and low-calcium fly ash-cementmixtures was investigated to determine the effect of fly ash upon the hydration of a Type I portland cement, and to determine the associated mechanisms of hydration. When blended with portland cement, both fly ashes retarded the early hydration process, the high-Ca more so than the low-Ca. Analyses of solution compositions and calorimetric (heat of hydration) measurements were made. The retardation and hydration effects are discussed in terms of solution composition data and solid phase characterization. The hydration effects were interpreted and compared with the results of previous work.

Fly Ashes Used For Blended Portland Cement: Effect Of Grinding on Cement Quality

1988 ◽  
Vol 136 ◽  
Author(s):  
Erik Stoltenberg-Hansson
Keyword(s):  
Particle Size ◽  
Fly Ash ◽  
Specific Gravity ◽  
Portland Cement ◽  
Large Scale ◽  
Void Content ◽  
Strength Increase ◽  
Fly Ashes ◽  
Laser Method ◽  
Air Void

ABSTRACTTests have been performed with Class F fly ashes used for the production of interground 20% fly ash cement. Unground and ground fly ashes were mixed with a reference high fineness Portland cement and tested for strength in mortar (ISO/CEN method). The fly ashes were also tested for chemical composition, bulk density and specific gravity, fineness (Blaine) and particle size distribution (laser method). There are considerable variations in the specific weights of the asdelivered fly ashes. It is shown that even a small amount of grinding increases the specific gravity significantly, and improves and homogenizes the particle size distributions, resulting in higher strength. The strength increase corresponds to the decrease in air void content.Intergrinding of fly ash and clinker in large scale mills reduces the power consumption, giving the same 28-day strength as mixed fly ash cement with higher fineness.

Effect of free lime content on properties of cement–fly ash mixtures

2013 ◽  
Vol 38 ◽  
pp. 829-836 ◽  
Author(s):  
Krittiya Kaewmanee ◽  
Pitisan Krammart ◽  
Taweechai Sumranwanich ◽  
Pongsak Choktaweekarn ◽  
Somnuk Tangtermsirikul
Keyword(s):  
Fly Ash ◽  
Free Lime ◽  
Lime Content

Evolution of Lime and Microstructural Development In Fly Ash-Portland Cement Systems

1989 ◽  
Vol 178 ◽  
Author(s):  
Joseph A. Larbi ◽  
Jan M. Bijen
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Dilution Effect ◽  
Pozzolanic Reaction ◽  
Microstructural Development ◽  
Inert Material ◽  
Interfacial Region ◽  
Interfacial Zone ◽  
Fly Ashes ◽  
Intimate Contact

AbstractThe evolution and distribution of calcium hydroxide, CH, and the development of microstructure during the hydration of three low-calcium fly ash-Portland cement blends with water-solids ratio (w/s) of 0.40 have been investigated. During the first month of hydration, the CH content of the blends was found to be relatively higher than the plain mix, if a dilution effect due to replacement of cement by an inert material is taken into account. After 28 days of hydration the CH content in the blends began to decrease. SEM observations of specimens revealed the occurrence of large, well-crystallized CH plates in intimate contact with some of the fly ash particles at younger ages and even after six months of aging. The study also showed that the chemistry of the pore solution in contact with the hydrating cement system and the characteristics of the fly ashes, such as the glass content and the fineness of the ash particles seem to exert major influences on the rate of evolution of CH in the fly ash blends. Semi-quantitative X-ray diffraction analyses performed on specimens cast against polypropylene plastic plates used to “model coarse aggregates” showed reduction in the thickness of the interfacial zone for the fly ash-Portland cement pastes from about 60μm to less than 15μm within one month of hydration. In the case of the plain Portland cement paste no significant change was observed. The degree of orientation of CH crystals within the interfacial region also was significantly affected by the fly ashes, although by this age of hydration the CH data showed little or no evidence of pozzolanic reaction.

scholarly journals Influence of Cement Replacement with Fly Ash and Ground Sand with Different Fineness on Alkali-Silica Reaction of Mortar

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1528
Author(s):  
Suwat Ramjan ◽  
Weerachart Tangchirapat ◽  
Chai Jaturapitakkul ◽  
Cheah Chee Ban ◽  
Peerapong Jitsangiam ◽  
...  
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Partial Substitution ◽  
Alkali Silica Reaction ◽  
Inert Material ◽  
Fly Ashes ◽  
River Sand ◽  
Concrete Materials

The alkali-silica reaction (ASR) is an important consideration in ensuring the long-term durability of concrete materials, especially for those containing reactive aggregates. Although fly ash (FA) has proven to be useful in preventing ASR expansion, the filler effect and the effect of FA fineness on ASR expansion are not well defined in the present literature. Hence, this study aimed to examine the effects of the filler and fineness of FA on ASR mortar expansion. FAs with two different finenesses were used to substitute ordinary Portland cement (OPC) at 20% by weight of binder. River sand (RS) with the same fineness as the FA was also used to replace OPC at the same rate as FA. The replacement of OPC with RS (an inert material) was carried out to observe the filler effect of FA on ASR. The results showed that FA and RS provided lower ASR expansions compared with the control mortar. Fine and coarse fly ashes in this study had almost the same effectiveness in mitigating the ASR expansion of the mortars. For the filler effect, smaller particles of RS had more influence on the ASR reduction than RS with coarser particles. A significant mitigation of the ASR expansion was obtained by decreasing the OPC content in the mortar mixture through its partial substitution with FA and RS.

scholarly journals Feasibility of Using Biomass Fly Ash in Cementitious Materials

Proceedings ◽  
2019 ◽  
Vol 34 (1) ◽  
pp. 12
Author(s):  
Jonathan Page ◽  
Laurent Libessart ◽  
Chafika Djelal ◽  
Maurice Gonon ◽  
Issam Laiymani
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Water Demand ◽  
Isothermal Calorimetry ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Wood Biomass ◽  
Fly Ashes ◽  
X Ray ◽  
Biomass Fly Ash

In recent years, numerous studies focused on the development of sustainable cement-based binders through the use of supplementary cementitious materials such slag, fly ash, metakaolin, silica fume, pozzolan, etc. The use of wood biomass for power generation is increasingly common which lead to an important amount of waste produced in the combustion process such as fly ash, which must be transported to landfills for deposition, or used as sludge in farming. Depending on their chemical and physical characteristics, wood biomass fly ashes could be reuse in blended cements as supplementary cementitious material. Different sources of biomass fly ashes have been selected to evaluate their potential for use as a cement replacement. Their chemical and mineralogical compositions, as well as their morphology were first evaluated via X-ray and laser diffraction (XRD), inductively coupled plasma (ICP) and scanning electron microscopy (SEM coupled with energy-dispersive X-ray spectroscopy (EDX). Fly ashes showed variable physicochemical characteristics but some present interesting compositions for the intended use. One fly ash present a high content of CaO and minors of SiO2 and Al2O3. The chemical composition does not allow to categorize this fly ash as a pozzolan material but it may have a latent hydraulic behaviour, which could be interesting as cement substitution. This fly ash has been incorporated into a cement paste by progressive replacement of Portland cement (from 0 to 70%). It has been observed that biomass fly ash has a higher water demand compared to Portland cement. This additional water demand was evaluated by the Vicat consistency test and by an evaporometry method. The setting time and kinetic hydration of the biomass fly ash pastes were also assessed with the standardized Vicat test and by isothermal calorimetry.

A Comprehensive Characterization and Determination of Fly Ashes in Indonesia Using Different Methods

2015 ◽  
Vol 754-755 ◽  
pp. 320-325 ◽  
Author(s):  
Januarti Jaya Ekaputri ◽  
Muhammad Bahrul Ulum ◽  
Triwulan ◽  
Ridho Bayuaji ◽  
Tri Eddy Susanto ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Power Plants ◽  
Ordinary Portland Cement ◽  
Activity Index ◽  
Chemical Characterization ◽  
Fly Ashes ◽  
Physical Chemical ◽  
Comprehensive Characterization

This paper presents an observation on fly ash quality in East Jawa, Indonesia. The ash samples were collected from 16 fly ashes produced by some Indonesian power plants. The samples are majority categorized as class F fly ashes with good pozzolanic characteristics according to the standard. The samples were examined for their physical, chemical and mechanical properties with compression test. The test was conducted by making some mortars and paste containing fly ash as cement replacement in accordance with three methods. The compressive strength results were compared with the control specimens made from ordinary Portland cement to obtain a strength activity index (SAI). The results showed that physical properties of fly ash influenced the mechanical properties of mortars more than those showed by chemical characterization.

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