Name: concrete damage from low ph water
Uploaded: 2024-11-07T14:48:46.000Z
Duration: 1 min 21 s
Channel: JoVE

K12 Standards

Alabama Course of Study Science

9-12

Earth and Space Science

Earth's Systems

9-12.ESS.2.4.b

Acid Attack on Concrete

Los ácidos que interactúan con el hormigón disuelven la pasta de cemento hidratada, lo que da lugar a un material reblandecido y estructuralmente debilitado.
La acidez descompone el hormigón cuando el pH del agua cae por debajo de 6,5, y el deterioro se acelera si el nivel de pH cae por debajo de 4,5.
El agua con 15 a 60 partes por millón de dióxido de carbono, como el agua helada derretida, puede degradar el concreto. El agua con turba con más de 60 partes por millón de dióxido de carbono es altamente corrosiva.
Las aguas residuales domésticas, aunque alcalinas, corroen las alcantarillas, especialmente con el calor, cuando las bacterias anaeróbicas convierten los compuestos de azufre en sulfuro de hidrógeno, que es oxidado por las bacterias anaeróbicas en ácido sulfúrico.
La velocidad de difusión de los iones de hidrógeno a través del gel de cemento también influye en la tasa de ataque, especialmente después de que el hidróxido de calcio se ha disuelto y lavado.
Los ataques de hidróxido de calcio se pueden prevenir estabilizándolos con silicato de sodio diluido, que forma silicatos de calcio en los poros del hormigón.
La aplicación de tratamientos superficiales como brea de alquitrán de hulla, pinturas de caucho o bituminosas y resinas epoxi ha demostrado ser eficaz para los ataques ácidos generales.

ataque ácido al hormigón

Cuando los ácidos entran en contacto con el hormigón, inician una reacción química que disuelve la pasta de cemento hidratada. Este proceso provoca el ablandamiento y el debilitamiento estructural del hormigón. Este problema se observa con frecuencia en entornos como chimeneas, alcantarillas y entornos industriales. La gravedad del daño aumenta a medida que el pH del agua que interactúa con el hormigón desciende por debajo de 6,5. En particular, un pH inferior a 4,5 puede provocar daños importantes en el hormigón.

La velocidad a la que se difunden los iones de hidrógeno a través del gel de hormigón también afecta la velocidad del ataque ácido, especialmente después de que el hidróxido de calcio del hormigón se haya disuelto y lavado. Además, el agua con niveles de dióxido de carbono entre 15 y 60 partes por millón, como el agua helada derretida, puede degradar el hormigón, mientras que el agua con turba con más de 60 partes por millón de dióxido de carbono puede ser altamente corrosiva y posiblemente reducir el pH a alrededor de 4,4.

Incluso las aguas residuales domésticas pueden corroer el hormigón de las alcantarillas, especialmente en condiciones cálidas, cuando las bacterias anaeróbicas convierten los compuestos de azufre en sulfuro de hidrógeno. Para evitar este tipo de ataques ácidos, es beneficioso estabilizar el hidróxido de calcio con silicato de sodio diluido, que forma silicatos de calcio protectores en los poros del hormigón. Además de esto, los tratamientos de superficie como la brea de hulla, las pinturas bituminosas o de caucho y las resinas epoxi han demostrado ser eficaces para combatir los ataques ácidos generales.

Ataque ácido al hormigón

Los ácidos que interactúan con el hormigón disuelven la pasta de cemento hidratada, lo que da lugar a un material reblandecido y estructuralmente debilitado.
La acidez rompe el ...

Education

Educación

JoVE Core

Civil Engineering

Ingeniería Civil

Unit 1

Unidad 1

Permeability of Concrete

Permeabilidad del hormigón

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

concrete damage from low ph water

Concrete damage from low pH water happens when acids react with the hydrated cement paste. This reaction dissolves the paste, so the concrete becomes softer and weaker. The problem is often seen in chimneys, sewers, and industrial settings.

The amount of damage depends on how acidic the water is. When pH falls below 6.5, the attack becomes more severe. A pH below 4.5 can cause major concrete damage. The rate of damage also depends on how fast hydrogen ions move through the cement gel. This effect is especially important after calcium hydroxide has dissolved and been washed away.

Carbon dioxide in water can also harm concrete. Water with 15 to 60 parts per million of carbon dioxide, such as melted ice water, can degrade concrete. Peaty water with more than 60 parts per million can be highly corrosive. It may lower the pH to about 4.4.

Sewage can also corrode concrete in sewers. Warm conditions make this worse. In that setting, anaerobic bacteria convert sulfur compounds into hydrogen sulfide. To limit acid attack, calcium hydroxide can be stabilized with diluted sodium silicate, which forms protective calcium silicates in the concrete pores. Surface coatings such as coal-tar pitch, rubber or bituminous paints, and epoxy resins can also help protect concrete.

Concrete Damage from Low pH Water

permeability of concrete

Concrete Durability and Water Penetration

Concrete durability depends partly on how easily water and gases can move through it. This property, called permeability, is important for judging water-tightness and resistance to chemical attack in concrete structures. Permeability is measured with comparative lab tests. In a typical test, the sides of a concrete specimen are sealed, water pressure is applied to the top surface, and the amount of water that passes through is measured. The test is often run for about ten days until a steady...

sulfate attack on concrete

Concrete Damage from Sulfate Exposure

Concrete damage from sulfate exposure starts with a whitish discoloration, often first seen at the edges and corners. As the attack continues, the concrete can crack and spall. This deterioration happens when sulfates react with hardened concrete and create new compounds that take up more space than the materials they replace. Sulfates may enter concrete from soil, groundwater, or industrial effluents. Inside the concrete, they can form calcium sulfate and calcium sulfoaluminate. The reaction...

effect of sea water on concrete

Seawater Damage and Concrete Durability

Seawater can damage concrete by changing its chemistry, increasing porosity, and lowering strength. In marine settings, concrete is exposed to dissolved salts and repeated wetting, so its durability depends on how much water can enter the material. One major form of damage is the breakdown of ettringite and gypsum, two concrete minerals that can dissolve in seawater. As these materials are lost, the concrete becomes more porous. Salt can also crystallize inside pores, especially above the...

acid attack on concrete

Concrete damage from low pH water happens when acids react with the hydrated cement paste. This reaction dissolves the paste, so the concrete becomes softer and weaker. The problem is often seen in chimneys, sewers, and industrial settings. The amount of damage depends on how acidic the water is. When pH falls below 6.5, the attack becomes more severe. A pH below 4.5 can cause major concrete damage. The rate of damage also depends on how fast hydrogen ions move through the cement gel. This...

alkali aggregate reaction in concrete

How Moisture Cracks Alkali-Reactive Concrete

Alkali-aggregate reaction in concrete can weaken a structure when siliceous minerals in the aggregate react with alkaline hydroxides from cement. The reaction makes an alkali-silica gel, which pulls in water and swells. As the gel expands inside the rigid cement paste, it creates pressure that can crack and disrupt the concrete. The damage comes from both osmotic hydraulic pressure and the swelling of the solid reaction products. Particle size also matters. Fine siliceous particles can cause...

corrosion of reinforcement

Why Concrete Can Fail Around Rebar

Steel reinforcement in concrete can corrode when its protective environment changes. Fresh concrete is highly alkaline because of calcium hydroxide, with a pH of about 13. That high pH helps form a passive iron oxide layer on the steel surface, which slows corrosion. Over time, carbonation, chloride ingress, and cracking can weaken this protection. Concrete contains hydrated cement paste with salts, and it acts as an electrolyte. Different areas of the steel then behave as anodic and cathodic...

key terms and concepts

Learn how acids, carbon dioxide, and sewage can weaken concrete, and how sodium silicate and protective coatings help reduce acid attack.

Concrete Damage from Low pH Water | JoVE K12

JoVE Core Civil Engineering provides a foundational exploration of essential construction materials in civil engineering, focusing on bricks, stones, steel, wood, and concrete through easy-to-understand animated videos. This collection covers the properties, manufacturing processes, and practical applications of these materials. Additionally, the accompanied science-in-action videos demonstrate the research experiments performed in laboratories.

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Acids interacting with concrete dissolve the hydrated cement paste, leading to a softened and structurally weakened material.
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Concrete Damage from Low pH Water

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