Resistance to Sulfate Attack and Chemo-Damage-Transport Model of Sulfate Ions for Tunnel Lining Concrete under the Action of Loading and Flowing Groundwater

2021 ◽  
Author(s):  
Qiang Fu ◽  
Mengxin Bu ◽  
Dan Li ◽  
Wenrui Xu ◽  
Jiaqi He ◽  
...  
Keyword(s):  
Transport Model ◽  
Sulfate Attack ◽  
Tunnel Lining ◽  
Sulfate Ions

scholarly journals Deterioration Process of Concrete Exposed to Internal Sulfate Attack

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1336 ◽  
Author(s):  
Weifeng Chen ◽  
Bei Huang ◽  
Yuexue Yuan ◽  
Min Deng
Keyword(s):  
Compressive Strength ◽  
Sulfate Attack ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Great Loss ◽  
Sulfate Ions ◽  
Coarse Aggregates ◽  
Deterioration Process ◽  
One Year ◽  
Internal Sulfate Attack

Damage to concrete structures with gypsum-contaminated aggregate occurs frequently. Aggregates in much of the southern part of China are contaminated with gypsum. Therefore, in this study, the effects of using different quantities of gypsum-contaminated aggregate on the expansion and compressive strength of concrete were investigated over a period of one year. Two groups of concrete were designed with the gypsum-contaminated aggregate containing different parts of fine and coarse aggregate, respectively. The SO3 contents were 0%, 0.5%, 1%, 1.5%, 3%, 5%, and 7% by weight of aggregate. X-ray diffraction (XRD), thermogravimetry (TG), and differential scanning calorimetry (DSC) were used to analyze the change in mineral composition over time. The microstructure was also studied by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The results showed that significant expansion and great loss in compressive strength did not occur in concrete if the content of SO3 lay below 1.5% and 3% in fine and coarse aggregates, respectively. The concentration of sulfate ions in concrete was not enough to form new a phase of gypsum. During the process of internal sulfate attack, the content of gypsum decreased and the content of ettringite increased. Ettringite was the main reason for the expansion damage of concrete. Additionally, the fracture mode of internal sulfate attack on concrete was the crack extension from gypsum to paste; finally, the aggregate separated from the paste.

Effect of Erosion Damage on Diffusion of Sulfate Ions in Concrete

2011 ◽  
Vol 243-249 ◽  
pp. 4683-4686 ◽  
Author(s):  
Chao Sun ◽  
Jian Kang Chen
Keyword(s):  
Differential Equation ◽  
Diffusion Equation ◽  
Numerical Method ◽  
Nonlinear Diffusion ◽  
Damage Evolution ◽  
Sulfate Attack ◽  
Nonlinear Diffusion Equation ◽  
Second Law ◽  
Sulfate Ions ◽  
Erosion Damage

Based on Fick’s second law and the damage evolution due to sulfate attack, a new model is proposed to analyze the diffusion of sulfate ions in concrete. The relation between erosion damage and erosion time, as well as the concentration of sulfate ions is firstly investigated by virtue of the ultrasonic experimental results. Furthermore, the damage evolution is treated as the increase of porosity, and a new nonlinear differential equation on the diffusion of sulfate ions is established by substituting such an increasing porosity into Fick’s law. The nonlinear diffusion equation is then solved by numerical method. It is found that the erosion damage can significantly affect the diffusion of sulfate ions in concrete.

Study of Fine-Grained Composites Exposed to Sulfuric Acid and Sodium Sulfate

2016 ◽  
Vol 827 ◽  
pp. 275-278
Author(s):  
Martin Vyšvařil ◽  
Markéta Rovnaníková
Keyword(s):  
Waste Water ◽  
Sulfuric Acid ◽  
Sodium Sulfate ◽  
Sulfate Attack ◽  
Sewer Pipes ◽  
Sulfate Ions ◽  
Fine Grained ◽  
One Year ◽  
Corrosion Of Steel ◽  
Loss Of Strength

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.

scholarly journals Evaluation of external sulfate attack (Na2SO4 and MgSO4): Portland cement mortars containing fillers

2020 ◽  
Vol 13 (3) ◽  
pp. 644-655 ◽  
Author(s):  
D. J. DE SOUZA ◽  
M. H. F. MEDEIROS ◽  
J. HOPPE FILHO
Keyword(s):  
Portland Cement ◽  
Linear Expansion ◽  
Sulfate Attack ◽  
Hardened Cement ◽  
X Ray Diffraction ◽  
Limestone Filler ◽  
Sulfate Ions ◽  
X Ray ◽  
Cement Mortars ◽  
Physical And Chemical

Abstract Sulfate attack is a term used to describe a series of chemical reactions between sulfate ions and hydrated compounds of the hardened cement paste. The present study aims to evaluate the physical (linear expansion, flexural and compressive strength) and mineralogical properties (X-ray diffraction) of three different mortar compositions (Portland Cement CPV-ARI with limestone filler and, with a quartz filler, in both cases with 10% replacement of the cement by weight) against sodium and magnesium sulfate attack (concentration of SO4 2- equal to 0.7 molar). The data collected indicate that the replacing the cement by the two fillers generate different results, the quartz filler presented a mitigating behaviour towards the sulfate, and the limestone filler was harmful to Portland cement mortars, in both physical and chemical characteristics.

scholarly journals Estimation of the Occurrence Time of Thaumasite Sulfate Attack on Tunnel Lining Concrete

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Chongbang Xu ◽  
Xiaojing Gao ◽  
Xuefeng Li ◽  
Kaishun Zhang
Keyword(s):  
Reaction Mechanisms ◽  
Concrete Structures ◽  
Experimental Tests ◽  
Sulfate Attack ◽  
Tunnel Lining ◽  
Shanxi Province ◽  
Occurrence Time ◽  
The Past ◽  
Site Investigations ◽  
Highway Tunnel

The thaumasite sulfate attack (TSA) on tunnel concrete structure has been reported increasingly in the past decades. Previous investigations on the formation of thaumasite were focused on identifying the deterioration products and reaction mechanisms, while the occurrence time of TSA on tunnel concrete structures was not reported. A highway tunnel exposed to TSA was reported in the present study. The development of tunnel diseases and results of experimental tests conducted in the tunnel and in the laboratory were analyzed to investigate the occurrence time of TSA on concrete. Results revealed that the thaumasite was formed in a range of 18 to 36 months after the construction of Dugongling tunnel. The preconditions for the formation of thaumasite on tunnel concrete structures are available in Shanxi Province, China, due to the special conditions of stratum lithology and climate. The compositions of corrosion products of lining concrete under TSA varied for site studies and for laboratory tests. Site investigations on TSA on tunnel lining concrete should be paid more attention in further research.

Multi-Phase Modelling of Concrete Affected by Sulfate Attack

2015 ◽  
Vol 784 ◽  
pp. 86-94
Author(s):  
Nicola Cefis ◽  
Claudia Comi
Keyword(s):  
Moisture Content ◽  
Diffusion Model ◽  
Cement Paste ◽  
Fluid Phase ◽  
Sulfate Attack ◽  
Reactive Diffusion ◽  
Solid Skeleton ◽  
Sulfate Ions ◽  
Multi Phase ◽  
Damage In Concrete

This study focuses on the modeling of damage in concrete subject to sulfate attack. The concrete is described as a multiphase material made of a solid skeleton, a fluid phase including water and air and an expanding phase, which exerts a pressure capable of damaging the concrete surrounding the reactive sites. The moisture content is computed through a simplified diffusion model, then a reactive-diffusion model allows for the computation of the expansive products of the reaction occurring between the aluminates of the cement paste and the incoming sulfate ions.

Sulfate Attack on Concrete: Is it real or just a misinterpretation of damage done by biodeterioration?

2013 ◽  
Vol 1612 ◽  
Author(s):  
Luis Emilio Rendon Diaz Miron ◽  
Montserrat Rendon Lara ◽  
Maria Eugenia Lara Magaña
Keyword(s):  
Chemical Interaction ◽  
Holistic Approach ◽  
External Source ◽  
Sulfate Attack ◽  
Salt Crystallization ◽  
Hardened Concrete ◽  
Sulfate Ions ◽  
Chemical Attack ◽  
Physical Attack ◽  
Large Numbers

ABSTRACTAt the present time, no material is known that is completely inert to chemical or biochemical action and immune to weathering damage. Concrete is no exception, but, under what might be considered normal exposure conditions, it has a very long life. Concrete made by the Romans from natural cement is in excellent condition after more than 2000 years of service. The controversies generated by contradictory expert testimonies in several lawsuits involving sulfate attack on concrete, and by the large numbers of recently published papers containing data on the subject, have caused considerable anxiety about sulfate attack mechanisms and the service life of concrete structures. Furthermore, frequently the physical attack by salt crystallization is being confused with the classical sulfate attack, which involves the chemical interaction between sulfate ions from an external source and the constituents of cement paste. In addition, there is also an internal sulfate attack –a chemical attack in which the source of sulfate ions resides in the concrete aggregates or cement–. Additionally, modern concrete as been affected by the products of microorganism metabolism, in particular sulfuric acid, this damage done to hardened concrete is known as concrete biodeterioration and also known as microbiologically induced corrosion of concrete (MICC). Being perhaps this biodeterioration the most important cause of concrete decay and perhaps the true explanation of sulfate attack on concrete. Some of the controversies about sulfate attack are addressed in this article, we have studied the case applying simple considerations concerning concrete composition and flouting at the same time some of the stricter observed paradigms in the cement and concrete industry. It is concluded that a holistic approach is necessary to separate the real causes of sulfate attack on concrete from the imaginary ones.

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