scholarly journals Chloride-Induced Corrosion of Steel in Alkali-Activated Mortars Based on Different Precursors

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5244
Author(s):  
Antonino Runci ◽  
Marijana Serdar
Keyword(s):  
Fly Ash ◽  
Chloride Solution ◽  
Corrosion Behaviour ◽  
Tap Water ◽  
Visual Assessment ◽  
The Sustainable Development ◽  
One Year ◽  
The Stability ◽  
By Products ◽  
Alkali Activated

The low environmental impact and high long-term performance of products are becoming imperative for the sustainable development of the construction industry. Alkali-activated materials (AAMs) are one of the available low-embodied-carbon alternatives to Portland cement (OPC). For their application in the marine environment or where de-icing salts are used, it is of utmost importance to demonstrate their equal or better performance compared to OPC. The aim of this study was to compare the corrosion behaviour of the steel in AAMs based on different regionally available by-products with the behaviour of the steel in OPC. The by-products used were fly ash, slag, silica fume, and iron-silica fines. The corrosion process of each system was monitored by the corrosion potential and polarisation resistance during exposure to tap water and chloride solution over a period of almost one year. Certain AAMs showed a higher resistance to chloride penetration compared to OPC, which was attributed to the smaller number of capillary pores and higher gel phase precipitation. The same corrosion resistance compared to OPC was achieved with alkali-activated fly ash and alkali-activated slag mortars. The stability of the systems in tap water and chloride solution was confirmed by the visual assessment of the steel surface at the end of the test period.

Mechanical Properties of Mortars Prepared by Alkali Activated Fly Ash Coming from Different Production Batches

2015 ◽  
Vol 244 ◽  
pp. 140-145 ◽  
Author(s):  
Matej Špak ◽  
Pavel Raschman
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Construction Materials ◽  
Chemical Properties ◽  
Raw Material ◽  
Fly Ashes ◽  
Coal Burning ◽  
Alkali Solutions ◽  
One Year ◽  
Alkali Activated

Fly ash is a well utilizable secondary raw material for the production of alkali activated construction materials. It is a significant alumina-silicates source suitable for the chemical reaction resulting in hardened composites. Physical and chemical properties of fly ashes as a co-product of coal burning mainly depend on characteristics of coal, burning temperature and combustion conditions. High variability of the properties of fly ash causes an uncertainty in the properties of alkali activated mortars. Time behaviour of the composition of the fly ash produced in a heating plant located in Košice, Slovakia as well as leaching behaviour of both alumina and silica from particular batches during one-year period was documented. Leaching tests were carried out using the distilled water and alkali solutions with three different concentrations. Both compressive and tensile strengths of alkali activated mortars were measured, and the correlation between the mechanical properties of hardened mortars and the chemical composition of fly ashes as well as their leaching characteristics was investigated.

scholarly journals Corrosion Behaviour of a New Low-Nickel Stainless Steel Reinforcement: A Study in Simulated Pore Solutions and in Fly Ash Mortars

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
M. Criado ◽  
S. Fajardo ◽  
J. M. Bastidas
Keyword(s):  
Stainless Steel ◽  
Fly Ash ◽  
Lower Cost ◽  
Electrochemical Impedance ◽  
Corrosion Behaviour ◽  
Nickel Content ◽  
Alkaline Solutions ◽  
Humidity Measurements ◽  
Evolution With Time ◽  
Alkali Activated

The present paper studies the corrosion behaviour of a new lower-cost type of austenitic stainless steel (SS) with a low nickel content in alkaline-saturated calcium hydroxide solution (a simulated concrete pore (SCP) solution) with sodium chloride (0.0%, 0.4%, 1.0%, 2.0%, 3.0%, and 5.0% NaCl) and embedded in alkali-activated fly ash (AAFA) mortars manufactured using two alkaline solutions, with and without chloride additions (2% and 5%), in an environment of constant 95% relative humidity. Measurements were performed at early age curing up to 180 days of experimentation. The evolution with time of electrochemical impedance spectroscopy was studied.Rctvalues obtained in SCP solution or in fly ash mortars were so high that low-nickel SS preserved its passivity, exhibiting high corrosion resistance

scholarly journals Mechanical Properties, Microstructure, and Chloride Content of Alkali-Activated Fly Ash Paste Made with Sea Water

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1467
Author(s):  
Salman Siddique ◽  
Jeong Gook Jang
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Sea Water ◽  
Tap Water ◽  
Pure Water ◽  
Degree Of Polymerization ◽  
29Si Nmr ◽  
Water Based ◽  
Ft Ir ◽  
Alkali Activated

The aim of the present study is to investigate the potential of sea water as a feasible alternative to produce alkali-activated fly ash material. The alkali-activated fly ash binder was fabricated by employing conventional pure water, tap water, and sea water based alkali activating solution. The characteristics of alkali-activated materials were examined by employing compressive strength, mercury intrusion porosimetry, XRD, FT-IR, and 29Si NMR along with ion chromatography for chloride immobilization. The results provided new insights demonstrating that sea water can be effectively used to produce alkali activated fly ash material. The presence of chloride in sea water contributed to increase compressive strength, refine microstructure, and mineralogical characteristics. Furthermore, a higher degree of polymerization on the sea water-based sample was observed by FT-IR and 29Si NMR analysis. However, the higher amount of free chloride ion even after immobilization in sea water-based alkali-activated material, should be considered before application in reinforced structural elements.

Influence of Industrial By-Products on Shrinkage of Alkali-Activated Slag

2014 ◽  
Vol 1000 ◽  
pp. 137-140
Author(s):  
Vlastimil Bílek Jr. ◽  
Lukáš Kalina ◽  
Eva Bartoníčková ◽  
Tomáš Opravil
Keyword(s):  
Fly Ash ◽  
Partial Replacement ◽  
Cement Kiln ◽  
Hydration Products ◽  
Fluidized Bed Combustion ◽  
Alkali Activated Slag ◽  
Activated Slag ◽  
Kiln Dust ◽  
By Products ◽  
Alkali Activated

One of the highest shortages of alkali-activated slag (AAS) is high shrinkage, both autogenous and drying. One of the possibilities of lowering the shrinkage is partial replacement of slag by suitable admixtures, which can act for example through the forming of expansive hydration products. In this study, 0–50 % of slag was replaced by by-pass cement kiln dust and fluidized bed combustion fly ash. Promising results were obtained especially in the case of fly ash. By using admixtures at higher dosages compressive strengths were reduced.

scholarly journals Steel Corrosion Behavior in Light Weight Fly-Ash Based Alkali Activated Mortars

2021 ◽  
Vol 11 (4) ◽  
pp. 1908
Author(s):  
Giulia Masi
Keyword(s):  
Corrosion Resistance ◽  
Fly Ash ◽  
Pore Solution ◽  
Tap Water ◽  
Steel Corrosion ◽  
Steel Structures ◽  
Solution Chemistry ◽  
Light Weight ◽  
Steel Corrosion Resistance ◽  
Alkali Activated

Alkali activated materials as possible sustainable alternative to cementitious binders showed competitive performances in terms of mechanical and durability properties and high temperature stability. For this reason, light weight fly-ash based mortars have already been optimized as passive fire protective coating for steel structures. However, a lack of information about the durability of these innovative systems in terms of steel corrosion resistance is still present. Thus, this study aims at investigating the durability of steel coated with a 20-mm thick light weight mortar layer in a neutral environment (tap water) and in presence of chloride-containing solution (0.2 M NaCl). In addition, the influence of pore solution chemistry and pH was discussed through electrochemical testing in leachate pore solution and NaOH aqueous solutions at different concentrations. It was found that almost complete protection ability of light weight mortar was obtained when coated steel is exposed to neutral solution for 60 days, while in presence of chlorides, steel is more susceptible to corrosion already after 40 days of exposure. In addition, the developed open porosity of the light weight mortars, it was found that pH and the chemistry of the pore solution in contact with steel strongly influenced the steel corrosion resistance.

New Test Method for Assessing the Carbonation Front in Alkali-Activated Fly Ash/Slag Pastes

2018 ◽  
Vol 761 ◽  
pp. 148-151
Author(s):  
Marija Nedeljković ◽  
Yi Bing Zuo ◽  
Kamel Arbi ◽  
Guang Ye
Keyword(s):  
Fly Ash ◽  
Color Change ◽  
Pore Solution ◽  
Polarized Light ◽  
Test Method ◽  
Environmental Scanning ◽  
X Ray Diffraction ◽  
Carbonation Reaction ◽  
One Year ◽  
Alkali Activated

Carbonation of the pore solution in alkali-activated materials (AAMs) produces alkali and/or alkali-earth carbonates. When the carbonate solubility in the water is very high (case of the most alkali carbonates), it is very hard to determine the carbonation depth in AAMs with the phenolphthalein indicator frequently used in Ordinary Portland Cement (OPC)-based materials. Carbonation gradually decreases the alkalinity of the pore solution, while the color after spraying phenolphthalein changes from colorless to pink when pH< 13 and changes back to colorless when pH< 8.2. The color change with phenolphthalein indicator may still exist in the less alkaline areas where carbonation may have already occurred. Therefore, using the indicator test is likely to underestimate the depth to which carbonation reaction has occurred in AAMs and more complete assessment is required. This study investigates the carbonation front in alkali-activated fly ash (FA) and blast furnace slag (BFS) pastes in natural laboratory conditions. Monitoring carbonation front in the samples after one year of exposure has been carried out under polarized light microscope (PLM), and environmental scanning electron microscope (ESEM). The carbonation products were sharply distinguished from the other constituents of the paste, by their crystallographic and optical characteristics under PLM, and characterized by X-Ray diffraction (XRD).

Fundamentals of Geopolymers and Related Alkali Activated Materials

2014 ◽  
Vol 803 ◽  
pp. 144-147 ◽  
Author(s):  
J. Temuujin ◽  
A. Minjigmaa ◽  
U. Bayarzul ◽  
Ts. Zolzaya ◽  
B. Davaabal ◽  
...  
Keyword(s):  
Fly Ash ◽  
Building Materials ◽  
Raw Materials ◽  
Construction Materials ◽  
Materials Chemistry ◽  
Low Carbon ◽  
Pond Ash ◽  
Sustainable Usage ◽  
By Products ◽  
Alkali Activated

With the increasing rate of depletion of natural raw materials for production of building materials, their sustainable usage is clearly an important topic for consideration. For instance, 1 tonne ordinary Portland cement (OPC) requires 1.7 tonnes of raw materials, 1.0 tonne of coal and 100 kWh of electricity. One tonne of cement emits 0.8 - 1 tonne of CO2 into atmosphere globally contributing ~5% of total manmade carbon dioxide. Therefore, the development of new, sustainable, low carbon footprint construction materials is an important task for materials scientists and civil engineers. One type of binder that is attracting particular attention around the world is alkali-aluminosilicate chemistry based material the so-called geopolymers. In this presentation we will discuss the fundamentals of geopolymer chemistry and the similarities to and differences from conventional alkali activated materials chemistry. Particular attention will be given to our latest results on the preparation of geopolymer type paste and concrete from fly ash. Mechanical activation of fly ash caused a decrease in porosity with a partial amorphisation of the crystalline constituents. Geopolymer type paste prepared from 30 minute milled Darkhan pond ash showed increase in 7 day compressive strengths by 7 times reaching of 15.4 (4.6) MPa. Keywords: Geopolymer binder, alkali-activated materials, coal combustion by products

Corrosion behaviour of a Low Ni austenitic stainless steel in carbonated chloride-polluted alkali-activated fly ash mortar

2014 ◽  
Vol 55 ◽  
pp. 49-58 ◽  
Author(s):  
C. Monticelli ◽  
M. Criado ◽  
S. Fajardo ◽  
J.M. Bastidas ◽  
M. Abbottoni ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Fly Ash ◽  
Austenitic Stainless Steel ◽  
Corrosion Behaviour ◽  
Alkali Activated

Freeze-Thaw Resistance with Sodium Chloride Solution of Fly-Ash Concrete Mixtures

2015 ◽  
Vol 1124 ◽  
pp. 137-144
Author(s):  
Tomáš Váchal ◽  
Rostislav Šulc ◽  
Pavel Svoboda
Keyword(s):  
Fly Ash ◽  
Sodium Chloride ◽  
Chloride Solution ◽  
Sodium Chloride Solution ◽  
Freeze Thaw ◽  
Fly Ash Concrete ◽  
Air Content ◽  
Concrete Mixtures ◽  
Alkali Activated Concrete ◽  
Alkali Activated

This paper describes freeze-thaw resistance with sodium chloride solution of concrete mixtures based on alkali-activated fly ash. There are shown relationships between freeze-thaw resistance with sodium chloride solution and air content in fresh alkali-activated concrete and relationship between freeze-thaw resistance with sodium chloride solution and spacing factor of alkali-activated concrete. Also there is described relationship between air content in fresh mixture and compressive strength of alkali-activated concrete.

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