The Effect of Chloride Ions on the Resistance of Concretes Containing Aerogel Under Sodium Sulfate Attack

Author(s):  
Mehdi Soleimanirad ◽  
Hamid Rahmani
1994 ◽  
Vol 370 ◽  
Author(s):  
D.P. Bentz ◽  
Nicos. S. Martys ◽  
P. Stutzman ◽  
M. S. Levenson ◽  
E.J. Garboczi ◽  
...  

AbstractX-ray microtomography can be used to generate three-dimensional 5123 images of random materials at a resolution of a few micrometers per voxel. This technique has been used to obtain an image of an ASTM C109 mortar sample that had been exposed to a sodium sulfate solution. The three-dimensional image clearly shows sand grains, cement paste, air voids, cracks, and needle-like crystals growing in the air voids. Volume fractions of sand and cement paste determined from the image agree well with the known quantities. Implications for the study of microstructure and proposed uses of X-ray microtomography on cement-based composites are discussed.


Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4095
Author(s):  
Fang Liu ◽  
Tonghuan Zhang ◽  
Tao Luo ◽  
Mengzhen Zhou ◽  
Kunkun Zhang ◽  
...  

In order to study the deterioration and mechanism of dry–wet cycles and sulfate attack on the performance of concrete in seaside and saline areas, the deterioration of compressive strength of concrete with different water cement ratios under different erosion environments (sodium sulfate soaking at room temperature and coupling of dry–wet cycling and sodium sulfate) was studied here. At the same time, ICT (industrial computed tomography) and NMR (nuclear magnetic resonance) techniques were used to analyze the internal pore structure of concrete under different erosion environments. The results show that the compressive strength under different erosion environments increases first and then decreases, and the dry–wet cycle accelerates the sulfate erosion. With the increase of dry and wet cycles, larger pores are filled with erosion products and developed into small pores in the early stage of erosion; in the later stage of erosion, the proportion of larger pores increases, and cracks occur inside the sample. In the process of sulfate soaking and erosion, the smaller pores in the concrete account for the majority. As the sulfate erosion continues, the T2 spectrum distribution curve gradually moves right, and the signal intensity of the larger pores increases.


Géotechnique ◽  
2014 ◽  
Vol 64 (8) ◽  
pp. 673-679 ◽  
Author(s):  
Y. YI ◽  
C. LI ◽  
S. LIU ◽  
A. AL-TABBAA

2011 ◽  
Vol 250-253 ◽  
pp. 22-27 ◽  
Author(s):  
Chang Cheng Li ◽  
Yan Yao ◽  
Ling Wang

Cement-limestone powder pastes added with 10% magnesium sulfate, sodium sulfate, and calcium sulfate respectively were stored in water at (5±2) °C to accelerate thaumasite formation. The pastes were inspected visually at intervals. And the formation of thaumasite was identified and confirmed by X-ray diffraction (XRD), infrared spectroscopy (IR), and nuclear magnetic resonance spectroscopy (NMR). The results show that internal adding sulfate in cement-limestone powder paste is an efficient way to accelerate thaumasite formation, and the accelerated effect is magnesium sulfate> sodium sulfate> calcium sulfate. Cement-limestone paste containing 10% magnesium sulfate totally turns into grey-white mushy materials after 6 months immersion, and products are mainly thaumasite and gypsum. In addition, the amount of thaumasite increases along with time of internal sulfate attack in 15 months. XRD, IR, and NMR are powerful and reliable tools for identification of thaumasite in cement-based materials.


2016 ◽  
Vol 827 ◽  
pp. 275-278
Author(s):  
Martin Vyšvařil ◽  
Markéta Rovnaníková

The degradation of concrete due to ingress of sulfate ions from the environment plays an important role in the durability of concrete constructions, especially in sewage collection systems where concrete sewer pipes are exposed to sulfates from waste water and from biogenic activity of bacteria. During this process the pH of the surface of concrete sewer pipes is reduced and it may lead to the steel depassivation and results in the corrosion of steel reinforcement. Damage due to sulfate interaction can result in the cracking and softening, with loss of strength of concrete. This paper is focused on the sulfate attack on fine-grained concrete where the effect of one-year contact of 0.5% H2SO4, and 5% Na2SO4 on changes of pH and content of sulfates in 7 types of concrete has been analyzed. It was found that after one year of sulfate attack on concrete, significant growth of content of sulfates is observed in the lowermost layer of the samples. Samples treated by 5% Na2SO4 contain slightly more sulfates in the upper layers than samples treated by sulfuric acid. The reduction in pH of aqueous leaches occurred in all layers of the samples. However, even in the lower layers of the samples, the reduction of pH below 9.5 did not turn up (except for SRS sample), and thus the conditions for the depassivation of reinforcement were not met.


2018 ◽  
Vol 71 (4) ◽  
pp. 531-542
Author(s):  
Laís Cristina Barbosa Costa ◽  
João Mário Roque Escoqui ◽  
Thais Mayra Oliveira ◽  
Leonardo Goliatt da Fonseca ◽  
Michèle Cristina Resende Farage

2020 ◽  
Vol 70 (337) ◽  
pp. 212
Author(s):  
L. R. Santillán ◽  
F. Locati ◽  
Y. A. Villagrán-Zaccardi ◽  
C. J. Zega

The effect of recycled concrete aggregate (RCA) on concrete performance against external sulfate attack (ESA) is not yet fully known. In this paper, recycled aggregate concretes (RAC) with 0, 50, 75 and 100% of RCA contents were evaluated after 10 years of exposure immersed in 50g/l sodium sulfate solution. Sulfate ingress profiles were obtained by wet chemical analyses and FRX. Also, the mineralogy of the ingress profile was evaluated by thermogravimetric analyses. Finally, microcracking development in samples was evaluated by optical fluorescent microscopy image analysis. Although RAC showed a slight increase in sulfate ingress, due to its higher porosity (about 30% higher SO3 content near the surface for 50% or higher replacement ratio than control concrete), a dense new matrix still allows a good performance of RAC to external sulfate attack with even 100% RCA content.


2008 ◽  
Vol 35 (11) ◽  
pp. 1210-1220 ◽  
Author(s):  
Seung-Tae Lee ◽  
Dae-Wook Park ◽  
Ki-Yong Ann

This paper presents a detailed experimental study on the sulfate attack of mortar specimens with or without silica fume exposed to sulfate and sulfate–chloride solutions (with the same concentration of SO42– ions) up to 510 d. The overall aim of the study is to investigate the beneficial effect of chloride ions on sulfate attack. In addition, the role of silica fume and water–binder ratio (w/b) in resisting sulfate attack is also reported. To qualitatively assess the performance of mortar specimens exposed to test solutions, visual examination and compressive strength and expansion tests were carried out. X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP) techniques were also used to evaluate the products formed by hydration and chemical reaction and the change of porosity for paste samples. Results indicated that the presence of chloride ions in sulfate environments mitigated the deterioration of ordinary Portland cement mortar specimens, especially with a higher w/b, due to sulfate attack. It seems that the mitigating effect of chloride ions on sulfate attack is attributable to the increased solubility of sulfate products in the chloride-bearing sulfate solution, and the chemical binding of the ions to form Friedel’s salt.


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