Corrosion Products in Cement-Based Materials under Sulfate Partial Soaking Attack

2011 ◽  
Vol 368-373 ◽  
pp. 415-418
Author(s):  
Kun Lin Ma ◽  
Wei Lun Wang ◽  
Guang Cheng Long ◽  
You Jun Xie
Keyword(s):  
Cement Mortar ◽  
Sulfate Solution ◽  
Corrosion Products ◽  
High Concentration ◽  
Chemical Corrosion ◽  
Cement Based Materials ◽  
Dry Zone ◽  
Deterioration Mechanism ◽  
Crystallization Zone ◽  
Wet Zone

The deterioration mechanism of sulfate attack on cement- based materials under partial soaking condition is very complex. This paper investigated the surface morphology, microstructure and corrosion products in different zones of cement mortar under 5% sulfate solution partial soaking condition at 360 d by methods of SEM, EDS and XRD, respectively. Results show that under partial soaking condition, cement mortar are distinguished four zones – soaking zone, wet zone, crystallization zone and dry zone. Corrosion products in soaking zone and wet zone are predominantly ettringite, showing chemical corrosion take place in those zones. Corrosion products in crystallization zone are gypsum and crystals of Na2SO4 and Na2SO4.10H2O, showing both sulfate chemical corrosion in high concentration and physical crystallization attack occur in this zone. However, there is no any corrosion product founded in dry zone.

Sulfate Crystallization Attack on Cement-Based Materials

2008 ◽  
Vol 400-402 ◽  
pp. 89-99
Author(s):  
You Jun Xie ◽  
Kun Lin Ma ◽  
Guang Cheng Long
Keyword(s):  
Salt Solution ◽  
Sodium Sulfate ◽  
Sulfate Solution ◽  
Mineral Admixture ◽  
Experimental Investigations ◽  
Capillary Effect ◽  
Chemical Corrosion ◽  
Factors Affecting ◽  
Cement Based Materials ◽  
Close Relationship

The physical crystallization action of sulfate in cement based material, which often occurs by dry-wet cycle, capillary rising and evaporating action, can damage seriously cement-based materials as compared to chemical corrosion by sulfate. The deterioration mechanism of cement-based materials by sulfate crystallization attack, experimental investigations of the process of sodium sulfate crystallization and the factors affecting the process, and the invading track of salt solution by capillary effect are presented in this paper. Results show that the crystal type and crystallization velocity of sodium sulfate is influenced greatly by relative humidity and ambient temperature. There is a close relationship between invading depth and the porosity of concrete. Addition of mineral admixture to concrete can significantly reduce the invading depth of sodium sulfate solution and thereby enhance the resistance of concrete to sulfate crystallization attack.The profile of invading track of salt solution by capillary effect is similar to the shape of concave parabola.

scholarly journals Effect of Surface Treatment of Polypropylene (PP) Fiber on the Sulfate Corrosion Resistance of Cement Mortar

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3690
Author(s):  
Yanyan Hu ◽  
Linlin Ma
Keyword(s):  
Corrosion Resistance ◽  
Silane Coupling Agent ◽  
Erosion Resistance ◽  
Cement Mortar ◽  
Fiber Surface ◽  
Cement Matrix ◽  
Chemical Corrosion ◽  
Silane Coupling ◽  
Cement Based Materials ◽  
Treated Fiber

Sulfate erosion is one of the most complex and harmful chemical corrosion actions. Following sulfate erosion, concrete expands, cracks, dissolves, peels off, and decreases in strength, which affects the durability of structures. Polypropylene fiber (PP) is widely used in various concrete structures because of its good mechanical properties and chemical corrosion resistance. However, PP fiber has a number of shortcomings, such as a smooth surface, poor hydrophilicity, lack of active groups in the molecular chain, and agglomeration and poor dispersion in cement-based materials. These issues limit its application in cement-based materials. Although the use of a silane coupling agent to modify the surface of PP fiber is effective, the influence of treated PP fiber on the sulfate resistance of cement-based materials is not significant. In this study, a PP fiber treated with a silane coupling agent was used to examine effects of different cement-to-sand ratios (C/S) and dosages of the treated PP fiber on the sulfate erosion resistance of cement mortar. Furthermore, the apparent morphology, mass loss rate, flexural strength, corrosion resistance coefficient, and microstructure of the concrete were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results revealed that the PP fiber became rough after modification. Active groups were introduced on the fiber surface, which were well dispersed in the mortar and formed a good network distribution structure in the cement mortar, thereby slowing the erosion rate of the PP fiber mortar in a sodium sulfate solution. At a C/S ratio of 1:1 and a treated fiber dosage of 0.6%, the treated fiber mortar has exhibited good sulfate resistance. In addition, the monofilament fiber immersion test revealed that a layer of sodium sulfate crystals was deposited on the fiber surface, thereby increasing the roughness of the fiber surface and the pull-out force of the fiber from the cement matrix, this result indicated that the interfacial adhesion between the treated PP fiber and cement matrix was improved, which in turn led to the improvement in the sulfate erosion resistance of the treated PP fiber.

The role of temperature in the thaumasite formation under the immersion of magnesium sulfate solution

2021 ◽  
pp. 1-28
Author(s):  
Surong Luo ◽  
Zhen Wang ◽  
Qingnan Gong ◽  
Dehui Wang
Keyword(s):  
Magnesium Sulfate ◽  
Cement Mortar ◽  
Energy Dispersive Spectrometer ◽  
Sulfate Solution ◽  
Corrosion Products ◽  
Limestone Powder ◽  
Direct Reaction ◽  
X Ray Diffraction ◽  
Magnesium Sulfate Solution

To clarify the role of temperature in the thaumasite formation of cement mortar under magnesium sulfate solution at two different temperature, the corrosion products and microstructure of cement-based materials with different amounts and particle sizes of limestone powder (LP) were quantitatively analyzed by Fourier Transform Infra-Red (FTIR), thermogravimetric analysis (TGA), X-ray Diffraction (XRD), Scanning Electronic Microscopy (SEM) and Energy Dispersive Spectrometer (EDS). At 5oC, the main corrosion product of cement mortar was gypsum and thaumasite. At 20°C, the main corrosion products of cement mortar were gypsum and ettringite. When the temperature increased from 5°C to 20°C, the contents of ettringite, thaumasite and gypsum changed from 0.3%, 12.3% and 64.6% to 4.6%, 0% and 57.0%, respectively. The formation of thaumasite was the combination of direct reaction with ettringite transformation. The incorporation of LP accelerated the corrosion of mortars, and the change coefficient of compressive strength of mortars decreased from 100% to 47.3% when its content increased from 0% to 30%. Low temperature and incorporation of finer limestone powder enhanced the corrosion of magnesium sulfate solution.

scholarly journals Effect of Hydrogen Nanobubbles on the Mechanical Strength and Watertightness of Cement Mixtures

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1823
Author(s):  
Won-Kyung Kim ◽  
Young-Ho Kim ◽  
Gigwon Hong ◽  
Jong-Min Kim ◽  
Jung-Geun Han ◽  
...  
Keyword(s):  
Mercury Intrusion Porosimetry ◽  
Cement Mortar ◽  
Stable State ◽  
Pozzolanic Reaction ◽  
Hydration Reaction ◽  
High Concentration ◽  
Mercury Intrusion ◽  
Electron Microscope Analysis ◽  
Mixing Water ◽  
Cement Mixtures

This study analyzed the effects of applying highly concentrated hydrogen nanobubble water (HNBW) on the workability, durability, watertightness, and microstructure of cement mixtures. The number of hydrogen nanobubbles was concentrated twofold to a more stable state using osmosis. The compressive strength of the cement mortar for each curing day was improved by about 3.7–15.79%, compared to the specimen that used general water, when two concentrations of HNBW were used as the mixing water. The results of mercury intrusion porosimetry and a scanning electron microscope analysis of the cement paste showed that the pore volume of the specimen decreased by about 4.38–10.26%, thereby improving the watertightness when high-concentration HNBW was used. The improvement in strength and watertightness is a result of the reduction of the microbubbles’ particle size, and the increase in the zeta potential and surface tension, which activated the hydration reaction of the cement and accelerated the pozzolanic reaction.

Review of the genus Cnemaspis Strauch, 1887 (Sauria: Gekkonidae) in Sri Lanka with the description of five new species

Zootaxa ◽  
2007 ◽  
Vol 1490 (1) ◽  
pp. 1-63 ◽  
Author(s):  
L. J.MENDIS WICKRAMASINGHE ◽  
D. A.I. MUNINDRADASA
Keyword(s):  
New Species ◽  
Sri Lanka ◽  
Morphometric Analysis ◽  
Mountain Region ◽  
Geographical Isolation ◽  
Morphological Comparison ◽  
Type Series ◽  
Dry Zone ◽  
High Degree ◽  
Wet Zone

Five new species of geckos are described from Sri Lanka by morphological comparison and morphometric analysis leading to review the genus Cnemaspis in the country. The type series of these species were identified from following localities: C. alwisi and C. kumarasinghei from the intermediate zone, C. retigalensis from the dry zone, C. molligodai from the lowland wet zone and C. samanalensis from the mountain region of the wet zone in the country. The high degree of endemicity (90%) shown by Cnemaspis in Sri Lanka could be attributed to geographical isolation. In addition, the taxonomic issue of C. jerdonii scalpensis is discussed and the species C. scalpensis is errected.

Separation of Heavy Metal Ions from the Solution Obtained by Leaching Low-Grade Pyrolusite with Pyrite and H2SO4

2013 ◽  
Vol 773 ◽  
pp. 283-288
Author(s):  
Xing Zou ◽  
Xiang Quan Chen ◽  
Hai Chao Xie ◽  
Xiao Dan Qiu
Keyword(s):  
Heavy Metal ◽  
Metal Ions ◽  
Heavy Metal Ions ◽  
Separation Efficiency ◽  
Ph Value ◽  
Sulfate Solution ◽  
Ion Concentration ◽  
Manganese Sulfate ◽  
Low Grade ◽  
High Concentration

The manganese sulfate solution leached from low-grade pyrolusite with pyrite and H2SO4 contains heavy metal ions of high concentration, influencing the quality of the final products of manganese compounds and causing manganese ions not to be electrolyzed. The present study was focused on the separation of Co, Ni and Zn ions from the leached solution with BaS. By controlling the pH value at 5.0-6.5, temperature at 50-60°C, reaction time at 15 min and mixing velocity at 78 rpm, the heavy metal ions could be separated effectively. Under the above optimized conditions, the ion concentration of Co, Ni, and Zn in the solution was reduced to 0.06 mg.L-1, 0.27mg.L-1 and 0.01mg.L-1, and the separation efficiency was 99.72%, 99.18% and 99.9% respectively. The obtained pure solution meets the demands of manganese electrowinning.

scholarly journals The Effect of Silica Sand Proportion in Laser Scabbling Process on Cement Mortar

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1914
Author(s):  
Tam-Van Huynh ◽  
Youngjin Seo ◽  
Dongkyoung Lee
Keyword(s):  
Cement Mortar ◽  
Silica Sand ◽  
Construction Sites ◽  
Power Laser ◽  
Concrete Repair ◽  
X Ray ◽  
Micro Cracks ◽  
Wide Range ◽  
Cement Based Materials ◽  
Composition Changes

Cement mortar composite has a wide range of applications on construction sites, including masonry, plastering and concrete repair. In construction sites, scabbling process is a method to remove from a few millimeters to several centimeters of defect concrete surfaces. As a result, it is essential to investigate the scabbling characteristics for cement mortar with different silica sand proportion in laser scabbling process. In this study, 5 types of cement mortar with different silica sand proportions in mixing were fabricated and scabbled by using a high-density power laser beam. The effects of silica sand proportion in color changing and penetration depth of the samples after laser scabbling process were studied. Furthermore, the generation of micro-cracks and pores were observed by using scanning electron microscopy (SEM). In addition, chemical composition changes between processed zone and non-processed zone were also evaluated by Energy Dispersive X-ray (EDX) analysis. The results of this study are expected to provide valuable knowledge in understanding of the laser scabbling process for cement-based materials.

Corrosion of Hot-Dip Galvanized Containment Installations: A Potential Cause for Thermal-Hydraulic Effects After LOCA in PWR?

2016 ◽  
Author(s):  
Holger Kryk ◽  
Ulrich Harm ◽  
Uwe Hampel
Keyword(s):  
Base Material ◽  
Volume Ratio ◽  
Corrosion Products ◽  
Zinc Borate ◽  
Test Facility ◽  
Joint Research ◽  
Surface Water Chemistry ◽  
Chemical Corrosion ◽  
Zinc Surface ◽  
Zinc Corrosion

Generic investigations regarding the influence of corrosion processes of hot-dip galvanized PWR containment installations on strainer clogging as well as on the coolant chemistry and possible resulting in-core effects are carried out within joint research projects of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), TU Dresden (TUD) and Zittau-Görlitz University of Applied Sciences (HSZG). Lab-scale experiments at HZDR and TUD are focused on elucidation of physico-chemical corrosion and precipitation processes as well as resulting clogging effects. Results of generic experiments in a lab-scale corrosion test facility suggest that there is a multi-stage corrosion process. The first stage comprises dissolution of the zinc layer in the coolant forming zinc ions and in turn affecting the coolant chemistry. During the second stage, the base material (steel) corrodes forming insoluble corrosion particles, which can subsequently lead to accelerated clogging of fiber-laden strainers within a few hours. The main influences on corrosion were identified as impact of the coolant jet onto the corroding surface, water chemistry and zinc surface / coolant volume ratio. Furthermore, retrograde solubility of zinc corrosion products in boric acid containing coolants with increasing temperature was observed. Thus, formation and deposition of solid corrosion products cannot be ruled out if zinc containing coolant is heated up during its recirculation into hot downstream components (e.g. hot-spots in core). Corrosion experiments, which included formation of corrosion products at a heated cladding tube, proved that zinc, dissolved in the coolant at low sump temperatures, turns into solid deposits of zinc borates when contacting heated zircaloy surfaces. Due to alternating heating and cooling of the coolant during sump recirculation operation, a cycle of zinc corrosion and zinc borate precipitation may be initiated, which may eventually influence the thermal hydraulics in downstream components during the post-LOCA stage. The results obtained at lab-scale were confirmed by corresponding experiments in semi-technical test facilities of the project partner HSZG. Based on the experimental results, water chemical measures were tested to reduce corrosion and/or zinc borate precipitation effects.

scholarly journals Some of the Wild Life Problems of Ceylon

Oryx ◽  
1959 ◽  
Vol 5 (3) ◽  
pp. 125-137
Author(s):  
R. M. Bere
Keyword(s):  
The South ◽  
Indian Peninsula ◽  
Climatic Regions ◽  
North East ◽  
The North ◽  
South Indian ◽  
Life Problems ◽  
Dry Zone ◽  
Wild Life ◽  
Wet Zone

Topographically Ceylon is a detached portion of the South Indian peninsula. It divides into two climatic regions, known as the Dry and Wet Zones; the latter occupies approximately the south-western quarter of the island. By African standards, dry and wet are relative terms and there may be over 80 inches of rain in the Dry Zone. Even so, rainfall tends to be concentrated and long periods without rain occur. The Wet Zone receives rain during both monsoons, the Dry Zone during the north-east monsoon only. Monsoons sometimes fail and serious droughts are not uncommon.

Experimental Study on the Anti-Cracking Property of Basalt Fiber for Cement-Based Materials

2011 ◽  
Vol 328-330 ◽  
pp. 1351-1354
Author(s):  
Jun Yong He ◽  
Xiao Qing Huang ◽  
Cheng Yu Tian
Keyword(s):  
Experimental Study ◽  
Experimental Research ◽  
21St Century ◽  
Cement Mortar ◽  
Polypropylene Fiber ◽  
Basalt Fiber ◽  
Polyacrylonitrile Fiber ◽  
Plastic Shrinkage ◽  
The World ◽  
Cement Based Materials

Basalt fiber has the advantages of non-pollution and omnipotence, and will be widely used in the 21st Century. Therefore, more and more attention is paid on experimental research on the basalt fiber in the world. First,according to the requirements of the fibers used in the cement-based materials, the contrast testing of the plastic shrinkage between fiber cement mortar and pure mortar was made. The experimental results showed that basalt fiber , polypropylene fiber and polyacrylonitrile fiber can be preliminarily chosen as reinforced fibers in cement-based materials. Finally, taking both characteristics of basalt fiber and the increase of cement-based materials costs into account, it can be drawn that top priority should be given to the basalt fiber rather than to other fibers for cement-based materials.

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