The Diffusion of Chloride Ions in Fly Ash/Cement Pastes and Mortars

1986 ◽  
Vol 86 ◽  
Author(s):  
R. I. A. Malek ◽  
D. M. Roy ◽  
P. H. Licastro
Keyword(s):  
Fly Ash ◽  
Electrical Potential ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Basic Material ◽  
Type I ◽  
Fly Ashes ◽  
Cement Pastes ◽  
High Calcium ◽  
Class F

ABSTRACTFly ashes having three distinctly different levels of calcium, designated low-calcium (Class F), intermediate-calcium (Class F/C), and high-calcium (Class C) comprised the basic material for the present study. Pastes and mortars were made out of the three types of fly ashes and one type of cement (Type I) at various levels of replacement as well as different water/solid ratios (w/c). Chloride ion diffusion was measured by applying an electrical potential across cured cylindrical samples and measuring the amount of current passed in a certain period of time (proportional to amount of Cl− passed in this time). Other supportive measurements were made, e.g., porosity and pore size distribution, water permeability and surface area. The Cl− ion diffusivities were correlated with the chemical composition of fly ash (FA), mix proportioning, and water permeabilities of the tested hardened pastes or mortars.

The Diffusion of Chloride Ions in Fly Ash/Cement Pastes and Mortars

1986 ◽  
Vol 85 ◽  
Author(s):  
R. I. A. Malek ◽  
D. M. Roy ◽  
P. H. Licastro
Keyword(s):  
Fly Ash ◽  
Water Permeability ◽  
Electrical Potential ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Basic Material ◽  
Fly Ashes ◽  
Cement Pastes ◽  
High Calcium ◽  
Class F

ABSTRACTFly ashes having three distinctly different levels of calcium, designated low-calcium (Class F), intermediate-calcium (Class F/C), and high-calcium (Class C), comprised the basic material for the present study. Pastes and mortars were made using cement and one of three types of fly ashes at various levels of replacement and water-solid ratios. Chloride ion diffusion was measured by applying an electrical potential across cured cylindrical samples and measuring the amount of current passed in a certain period of time (proportional to amount of CE” passed in this time). Other supportive measurements were made, e.g. porosity, pore size distribution, water permeability and surface area. The Cl− ion diffusivity was correlated with the chemical composition of fly ash, mix proportion, and water permeability of the hardened paste or mortar.

The Permeability of Chloride Ions in Fly Ash-Cement Pastes, Mortars and Concrete

1987 ◽  
Vol 114 ◽  
Author(s):  
R. I. A. Malek ◽  
D. M. Roy
Keyword(s):  
Fly Ash ◽  
Electrical Potential ◽  
Chloride Ion ◽  
Ionic Species ◽  
Cylindrical Sample ◽  
Chloride Ions ◽  
Test Scheme ◽  
Chloride Permeability ◽  
Experimental Conditions ◽  
Cement Pastes

ABSTRACTFly ash-cement pastes are known to develop fine pore structures that may retard the transport of ionic species. The rapid chloride permeability technique for studying the Cl− ion diffusion in hydrated fly ash/cement pastes, mortars and concrete was used. The technique applies an electrical potential across a cylindrical sample and measures the charge passed in a certain period of time. The results obtained on pastes and mortars cured for 28 days were reported previously and contrasted with those of neat cement pastes and mortars. The present paper reports more extensive studies made to examine the chloride permeabilities of pastes and mortars cured for up to 90 days. In addition, the effect of variable fly ash contents was examined. Concrete samples were included in the test scheme and the data were compared with pastes and mortars. Two important factors controlling the test results are discussed: first the mix design and curing conditions; second the experimental conditions during Cl− permeability measurements. In the second factor, the amount and rate of heat build up and the chloride ion concentrations are compared with the current passed. In addition, measuring current versus resistivity are critically discussed in terms of the voltage-current varistic characteristics of cement matrices.

The Permeability of Chloride Ions in Fly Ash-Cement Pastes, Mortars and Concrete

1987 ◽  
Vol 113 ◽  
Author(s):  
R. I. A. Malek ◽  
D. M. Roy
Keyword(s):  
Fly Ash ◽  
Electrical Potential ◽  
Chloride Ion ◽  
Ionic Species ◽  
Cylindrical Sample ◽  
Chloride Ions ◽  
Test Scheme ◽  
Chloride Permeability ◽  
Experimental Conditions ◽  
Cement Pastes

ABSTRACTFly ash-cement pastes are known to develop fine pore structures that may retard the transport of ionic species. The rapid chloride permeability technique for studying the Cl- ion diffusion in hydrated fly ash/cement pastes, mortars and concrete was used. The technique applies an electrical potential across a cylindrical sample and measures the charge passed in a certain period of time. The results obtained on pastes and mortars cured for 28 days were reported previously and contrasted with those of neat cement pastes and mortars. The present paper reports more extensive studies made to examine the chloride permeabilities of pastes and mortars cured for up to 90 days. In addition, the effect of variable fly ash contents was examined. Concrete samples were included in the test scheme and the data were compared with pastes and mortars. Two important factors controlling the test results are discussed: first the mix design and curing conditions; second the experimental conditions during Cl- permeability measurements. In the second factor, the amount and rate of heat build up and the chloride ion concentrations are compared with the current passed. In addition, measuring current versus resistivity are critically discussed in terms of the voltage-current varistic characteristics of cement matrices.

Trapping of Chloride Ions in Cement Pastes Containing Fly Ash

1985 ◽  
Vol 65 ◽  
Author(s):  
D. M. Roy ◽  
R. I. A. Malek ◽  
M. Rattanussorn ◽  
M. W. Grutzeck
Keyword(s):  
Fly Ash ◽  
Chloride Ion ◽  
Exchange Chromatography ◽  
Chloride Ions ◽  
Emission Spectrometry ◽  
Type I ◽  
Cement Pastes ◽  
Plasma Emission Spectrometry ◽  
Mechanisms Of Formation ◽  
Sufficient Concentration

ABSTRACTChloride ions, when present at sufficient concentration in the concrete pore fluid, may be associated with corrosion of the reinforcing steel even in normally passivative environments. The effectiveness of fly ash containing pastes in trapping chloride ions was studied. A paste was prepared containing 30% low-calcium fly ash and 70% type I cement, with mixing water (50% by weight) containing 0.4% C1− with respect to the solid. Samples were cured at 25°C and 38°lC at 95% R.H. At designated times extending over a six-month period, the pore fluids were expressed from the hardened pastes using a squeezing cell designed for this purpose. Special precautions were taken to avoid carbonation of the fluids; contact with the atmosphere was minimized. The expressed fluids were analyzed by DC plasma emission spectrometry for cations and by automated selective ion exchange chromatography for anions. Other studies (XRD, thermal analysis) were carried out to identify the compounds formed and determine their mechanisms of formation. Investigations indicated that the mechanism of trapping chloride ion is partly chemical and partly physical through adsorption on the surface of fly ash particles (initially physical and subsequently chemical).

scholarly journals Durability Assessment of Concrete with Class-F Fly Ash by Chloride Ion Permeability

2019 ◽  
Vol 8 (4) ◽  
pp. 8831-8836
Keyword(s):  
Fly Ash ◽  
Chloride Ion ◽  
Pozzolanic Reaction ◽  
Chloride Ions ◽  
Permeability Test ◽  
Reaction Products ◽  
Chloride Permeability ◽  
Cement Pastes ◽  
Rapid Chloride Permeability ◽  
Class F Fly Ash

This paper discusses on Rapid Chloride Permeability Test investigations on penetration of chloride ions included with replacement of cement by flyash material. By weigth of cement, the fly ash content is replaced from 0% to 60%. Concrete mixes with different binder content varies from 350, 400 and 450 kg/m3 were proportioned with different water binder(w/b) ratios = 0.4, 0.45 and 0.50. Specimens were casted and tested for 28 days. For all the combinations, RCPT was carried out and the charge passed through the specimens was noted. Rapid Chloride Permeability Test value of concrete without fly ash was found to be more than the concrete with fly ash. The Rapid Chloride Permeability Test values are found to be decreased if the percentage of flyash increases. The reason could be the pozzolanic reaction products (CSH) fill the pores between the cement pastes and cause a denser concrete matrix, resulting in better durability. Hence, it can be suggested that the fly ash concrete up to 50% replacement can be used for variety of applications.

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.

Electrokinetic Phenomena and Surface Characteristics of Fly Ash Particles

1984 ◽  
Vol 43 ◽  
Author(s):  
R. I. A. Malek ◽  
D. M. Roy
Keyword(s):  
Fly Ash ◽  
Surface Characteristics ◽  
Ionic Species ◽  
Point Of Zero Charge ◽  
Fly Ashes ◽  
Electrokinetic Phenomena ◽  
Zeta Potentials ◽  
Low Calcium ◽  
High Calcium

AbstractThe zeta-potentials of two fly ashes were studied (high-calcium and low-calcium). It was found that they possess a point of charge reversal at pH = 10.5 to 12. The point of zero charge (low-calcium fly ash) was found to be at pH = 5. Furthermore, it shifted to more acidic values after the fly ash is aged in several calcium-containing solutions. The surficial changes that could happen when mixing fly ashes with cement and concrete were further evaluated by aging fly ashes in different solutions: Ca(OH)2, CaSO4·2H2O, NaOH and water solutions. Information from analyses for different ionic species in the solutions and characterization of the solid residues (XRD and SEM) was used in tentative explanations for the different behavior of the two types of fly ash in cementitious mixtures and concrete.

scholarly journals Durability of blended cement against sodium sulphate attack and alkali-silica reaction

2021 ◽  
Author(s):  
Giri Raj Adhikari
Keyword(s):  
Fly Ash ◽  
Silica Fume ◽  
Alkali Silica Reaction ◽  
Sulphate Attack ◽  
Ternary Blends ◽  
Replacement Level ◽  
Fly Ashes ◽  
Study Results ◽  
High Calcium ◽  
High Calcium Fly Ash

Blended cements were studied for their efficacy against sulphate attack and alkali-silica reaction using six different types of fly ashes, a slag, a silica fume and four types of General Use Portland cement of different alkalinity. The study results showed that low calcium fly ash, silica fume and ground granulated blast furnace slag enhanced the sulphate resistance of cement with increased efficacy with the increase in the replacement level. However, slag and silica fume, especially at low replacement levels, exhibited increased rate of expansion beyond the age of 78 weeks. On the contrary, high calcium fly ashes showed reduced resistance to sulphate attack with no clear trend between the replacement level and expansion. Ternary blends consisting of silica fume, particulary in the amount of 5%, high calcium fly ashes and General Use (GU) cement provided high sulphate resistance, which was attributable to reduced permeability. In the same way, some of ternary blends consisting of slag, high calcium fly ash and GU cement improved sulphate resistance. Pre-blending optimum amount of gypsum with high calcium fly ash enhanced the latter's resistance to sulphate attack by producing more ettringite at the early stage of hydration. In the context of alkali-silica reaction permeability was found to be a contributing factor to the results of the accelerated mortar bar test. High-alkali, high-calcium fly ash was found to worsen the alkali silica reaction when used in concrete containing some reactive aggregates. Ternary blend of slag with high calcium fly ash was found to produce promising results in terms of counteracting alkali-silica reaction.

Osmoregulation in the Larva of the Marine Caddis Fly, Philanisus Plebeius (Walk.) (Trichoptera)

1972 ◽  
Vol 57 (3) ◽  
pp. 821-838
Author(s):  
JOHN P. LEADER
Keyword(s):  
Sodium Chloride ◽  
Osmotic Pressure ◽  
Body Surface ◽  
Sea Water ◽  
Electrical Potential ◽  
Chloride Ion ◽  
Chloride Ions ◽  
The Body ◽  
Electrical Potential Difference ◽  
Caddis Fly

1. The larva of Philanisus plebeius is capable of surviving for at least 10 days in external salt concentrations from 90 mM/l sodium chloride (about 15 % sea water) to 900 mM/l sodium chloride (about 150 % sea water). 2. Over this range the osmotic pressure and the sodium and chloride ion concentrations of the haemolymph are strongly regulated. The osmotic pressure of the midgut fluid and rectal fluid is also strongly regulated. 3. The body surface of the larva is highly permeable to water and sodium ions. 4. In sea water the larva is exposed to a large osmotic flow of water outwards across the body surface. This loss is replaced by drinking the medium. 5. The rectal fluid of larvae in sea water, although hyperosmotic to the haemolymph, is hypo-osmotic to the medium, making it necessary to postulate an extra-renal site of salt excretion. 6. Measurements of electrical potential difference across the body wall of the larva suggest that in sea water this tissue actively transports sodium and chloride ions out of the body.

scholarly journals Influence of Fly Ash Additive on the Properties of Concrete with Slag Cement

Materials ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3265 ◽  
Author(s):  
Anna Szcześniak ◽  
Jacek Zychowicz ◽  
Adam Stolarski
Keyword(s):  
Fly Ash ◽  
Chloride Ion ◽  
High Strength ◽  
Experimental Tests ◽  
Chloride Ions ◽  
Strength Increase ◽  
Slag Cement ◽  
Initial Strength ◽  
Chloride Ion Penetration ◽  
The Impact

This paper presents research on the impact of fly ash addition on selected physical and mechanical parameters of concrete made with slag cement. Experimental tests were carried out to measure the migration of chloride ions in concrete, the tightness of concrete exposed to water under pressure, and the compressive strength and tensile strength of concrete during splitting. Six series of concrete mixes made with CEM IIIA 42.5 and 32.5 cement were tested. The base concrete mix was modified by adding fly ash as a partial cement substitute in the amounts of 25% and 33%. A comparative analysis of the obtained results indicates a significant improvement in tightness, especially in concrete based on CEM IIIA 32.5 cement and resistance to chloride ion penetration for the concretes containing fly ash additive. In the concretes containing fly ash additive, a slower rate of initial strength increase and high strength over a long period of maturation are shown. In accordance with the presented research results, it is suggested that changes to the European standardization system be considered, to allow the use of fly ash additive in concrete made with CEM IIIA 42.5 or 32.5 cement classes. Such a solution is not currently acceptable in standards in some European Countries.

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