Sulfuric Acid Attack on Various Types of Fine Grained Concrete

2015 ◽  
Vol 1100 ◽  
pp. 101-105
Author(s):  
Martin Vyšvařil ◽  
Markéta Rovnaníková
Keyword(s):  
Sulfuric Acid ◽  
Acid Corrosion ◽  
Sulfate Attack ◽  
Steel Reinforcement ◽  
Acid Attack ◽  
Sewer Pipes ◽  
Sulfate Ions ◽  
Fine Grained ◽  
Ph Values ◽  
Sulfuric Acid Corrosion

Sulfate corrosion is one of the major threats for durability of concrete constructions and it becomes a major destructor in sewage collection systems where the concrete sewer pipes are exposed to sulfates from wastewater as well as from biogenic activity of bacteria. During this process the pH of the surface of concrete sewer pipes is reduced and it may lead to steel depassivation and results in the corrosion of this steel reinforcement. This paper is focused on the sulfate attack on fine grained concrete where the effect of 0.5% sulfuric acid, simulating biogenic sulfuric acid corrosion, on changes of pH and content of sulfates in various types of concrete has been investigated. After 3 and 6 months of the corrosive treatment, the content of sulfate ions and pH values in several layers of specimens were determined. It was found that the sulfate ions penetrate into concrete to the maximum depth of 20 mm and the pH of the aqueous leaches of particular layers of the samples was reduced to 11.4 at the most. Thus, the conditions for the depassivation of reinforcement were not met. The GL and GBFS concrete samples showed the least changes of their pH and therefore they had the best resistivity to the six months sulfate attack.

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.

Sulfate Attack on Different Types of Concrete in Media Simulating Sewer System

2016 ◽  
Vol 714 ◽  
pp. 122-127
Author(s):  
Martin Vyšvařil ◽  
Markéta Rovnaníková ◽  
Patrik Bayer
Keyword(s):  
Waste Water ◽  
Sulfuric Acid ◽  
Sewage Water ◽  
Sulfate Attack ◽  
Acid Attack ◽  
Bottom Part ◽  
Sewer Pipes ◽  
Fine Grained ◽  
Different Types ◽  
One Year

The degradation of concrete due to ingress of sulfate ions from the environment plays an important role in the durability of concrete constructions. Microbiologically induced concrete corrosion (MICC) damages especially sewage collection systems. The most rapid cases of deterioration always occur in areas with elevated H2S concentrations, moisture, and oxygen in the atmosphere. During the MICC, 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 a sulfate interaction can result in a cracking and softening, with a loss of strength of concrete. The formation of ettringite (AFt) from gypsum (forming by reaction of sulfate anion with calcium hydroxide) and C3A via monosulfate (AFm) is the main chemical reaction of sulfate attack on concrete. Ettringite and gypsum have considerably larger volume than initial compounds, which leads to increased pressure in concrete. This paper is focused on the sulfate attack on fine-grained concrete where the effect of 0.5% sulfuric acid, simulating MICC, and a solution simulating sewage water has been investigated on changes of the pH, content of sulfates and the porosity in various types of concrete. The aim of this study is to compare the changes in different types of concrete during the sulfate attack in two kinds of medium represented the bottom part of pipelines (waste water) and the sewer crown (0.5% H2SO4). It was found, that after 1 year in 0.5% H2SO4, a visible degradation of surface occurs in all investigated types of concrete. Samples over the year in waste water became dark. Concentration of sulfates in all studied types of concrete increased six times at least after one year sulfuric acid attack and also the reduction of the pH of their aqueous leaches was determined. The solution simulating sewage water did not cause such changes.

One-Year Sulfate Attack on Various Types of Fine Grained Concrete

2015 ◽  
Vol 1124 ◽  
pp. 313-318
Author(s):  
Martin Vyšvařil ◽  
Markéta Rovnaníková
Keyword(s):  
Sulfuric Acid ◽  
Acid Corrosion ◽  
Surrounding Medium ◽  
Mineralogical Composition ◽  
Sulfate Solution ◽  
Xrd Analysis ◽  
Sewage Water ◽  
Sulfate Attack ◽  
Fine Grained ◽  
Ph Decrease

Concrete shows extensive degradation when exposed to the external sulfate attack, characterized by ingress of sulfate ions from surrounding medium. This process leads to gradual pH decrease, to expansion, cracking, spalling of concrete, and finally to the complete disintegration of the material. Sulfate attack becomes a major destructor in sewage collection systems where the concrete sewer pipes are exposed to sulfates from wastewater as well as from biogenic activity of bacteria. This paper is focused on the sulfate attack on fine grained concrete where the effect of 0.5% sulfuric acid, simulating biogenic sulfuric acid corrosion, 5% sodium sulfate solution and solution simulating sewage water on various types of concrete has been investigated. The concrete specimens were characterized after exposition to corroding media by their mechanical parameters, microstructure and in the case of H2SO4 as the most aggressive corroding solution, the mineralogical composition was also determined by XRD analysis. It was found that the exposition to Na2SO4 solution twofold improved flexural strengths of concrete mixes based on Portland and sulfate-resisting cements. Contrary, the exposition to H2SO4 solution significantly decreased compressive strengths of all types of concrete.

scholarly journals Resistance to Sulfuric Acid Corrosion of Geopolymer Concrete Based on Different Binding Materials and Alkali Concentrations

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7109
Author(s):  
Wei Yang ◽  
Pinghua Zhu ◽  
Hui Liu ◽  
Xinjie Wang ◽  
Wei Ge ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Corrosion Resistance ◽  
Sulfuric Acid ◽  
Fly Ash ◽  
Acid Corrosion ◽  
Geopolymer Concrete ◽  
High Calcium ◽  
High Calcium Fly Ash ◽  
Naoh Solution ◽  
Sulfuric Acid Corrosion

Geopolymer binder is expected to be an optimum alternative to Portland cement due to its excellent engineering properties of high strength, acid corrosion resistance, low permeability, good chemical resistance, and excellent fire resistance. To study the sulfuric acid corrosion resistance of geopolymer concrete (GPC) with different binding materials and concentrations of sodium hydroxide solution (NaOH), metakaolin, high-calcium fly ash, and low-calcium fly ash were chosen as binding materials of GPC for the geopolymerization process. A mixture of sodium silicate solution (Na2SiO3) and NaOH solution with different concentrations (8 M and 12 M) was selected as the alkaline activator with a ratio (Na2SiO3/NaOH) of 1.5. GPC specimens were immersed in the sulfuric acid solution with the pH value of 1 for 6 days and then naturally dried for 1 day until 98 days. The macroscopic properties of GPC were characterized by visual appearance, compressive strength, mass loss, and neutralization depth. The materials were characterized by SEM, XRD, and FTIR. The results indicated that at the immersion time of 28 d, the compressive strength of two types of fly ash-based GPC increased to some extent due to the presence of gypsum, but this phenomenon was not observed in metakaolin-based GPC. After 98 d of immersion, the residual strength of fly ash based GPC was still higher, which reached more than 25 MPa, while the metakaolin-based GPC failed. Furthermore, due to the rigid 3D networks of aluminosilicate in fly ash-based GPC, the mass of all GPC decreased slightly during the immersion period, and then tended to be stable in the later period. On the contrary, in metakaolin-based GPC, the incomplete geopolymerization led to the compressive strength being too low to meet the application of practical engineering. In addition, the compressive strength of GPC activated by 12 M NaOH was higher than the GPC activated by 8 M NaOH, which is owing to the formation of gel depended on the concentration of alkali OH ion, low NaOH concentration weakened chemical reaction, and reduced compressive strength. Additionally, according to the testing results of neutralization depth, the neutralization depth of high-calcium fly ash-based GPC activated by 12 M NaOH suffered acid attack for 98 d was only 6.9 mm, which is the minimum value. Therefore, the best performance was observed in GPC prepared with high-calcium fly ash and 12 M NaOH solution, which is attributed to gypsum crystals that block the pores of the specimen and improve the microstructure of GPC, inhibiting further corrosion of sulfuric acid.

Biogenic sulfuric acid corrosion resistance of new artificial reef concrete

2018 ◽  
Vol 158 ◽  
pp. 33-41 ◽  
Author(s):  
Yu Yang ◽  
Tao Ji ◽  
Xujian Lin ◽  
Caiyi Chen ◽  
Zhengxian Yang
Keyword(s):  
Corrosion Resistance ◽  
Sulfuric Acid ◽  
Acid Corrosion ◽  
Artificial Reef ◽  
Sulfuric Acid Corrosion
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