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

Les acides qui interagissent avec le béton dissolvent la pâte de ciment hydratée, ce qui donne un matériau ramolli et structurellement affaibli.
L’acidité décompose le béton lorsque le pH de l’eau descend en dessous de 6,5, et la détérioration s’accélère si le niveau de pH tombe en dessous de 4,5.
L’eau contenant 15 à 60 parties par million de dioxyde de carbone, comme l’eau glacée fondue, peut dégrader le béton. L’eau tourbeuse contenant plus de 60 parties par million de dioxyde de carbone est très corrosive.
Les eaux usées domestiques, bien qu’alcalines, corrodent les égouts, surtout en cas de chaleur, lorsque les bactéries anaérobies transforment les composés soufrés en sulfure d’hydrogène, qui est oxydé par les bactéries anaérobies en acide sulfurique.
Le taux de diffusion des ions hydrogène à travers le gel de ciment influence également le taux d’attaque, en particulier après la dissolution et l’élimination de l’hydroxyde de calcium.
Les attaques d’hydroxyde de calcium peuvent être évitées en le stabilisant avec du silicate de sodium dilué, qui forme des silicates de calcium dans les pores du béton.
L’application de traitements de surface tels que la poix de goudron de houille, les peintures en caoutchouc ou bitumineuses et les résines époxy s’est avérée efficace pour les attaques acides générales.

attaque acide sur béton

Lorsque les acides entrent en contact avec le béton, ils déclenchent une réaction chimique qui dissout la pâte de ciment hydratée. Ce processus entraîne un ramollissement et un affaiblissement structurel du béton. Ce problème est fréquemment observé dans des environnements tels que les cheminées, les égouts et les environnements industriels. La gravité des dommages augmente lorsque le pH de l'eau interagissant avec le béton descend en dessous de 6,5. En particulier, un pH inférieur à 4,5 peut causer des dommages importants au béton.


 La vitesse à laquelle les ions hydrogène se diffusent dans le gel de ciment a également un impact sur la vitesse d'attaque acide, notamment après que l'hydroxyde de calcium du béton a été dissous et éliminé. De plus, l'eau contenant entre 15 et 60 parties par million de dioxyde de carbone, comme l'eau glacée fondue, peut dégrader le béton, tandis que l'eau tourbeuse contenant plus de 60 parties par million de dioxyde de carbone peut être très corrosive, réduisant éventuellement le pH à environ 4,4.


 Les eaux usées domestiques peuvent également corroder le béton des égouts, en particulier dans des conditions chaudes où les bactéries anaérobies transforment les composés soufrés en sulfure d’hydrogène. Pour prévenir ce type d’attaques acides, il est bénéfique de stabiliser l’hydroxyde de calcium avec du silicate de sodium dilué, qui forme des silicates de calcium protecteurs dans les pores du béton. De plus, les traitements de surface tels que le brai de goudron de houille, les peintures au caoutchouc ou au bitume et les résines époxy se sont avérés efficaces pour lutter contre les attaques acides générales.

Attaque acide sur béton

Les acides qui interagissent avec le béton dissolvent la pâte de ciment hydratée, ce qui donne un matériau ramolli et structurellement affaibli.
L’acidité décompose le ...

Education

Enseignement

JoVE Core

Civil Engineering

Génie civil

Unit 1

Unité 1

Permeability of Concrete

Perméabilité du béton

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

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.

civil engineering

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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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b. Construct an explanation, based on evidence, of tectonic plate movement, types of plate boundaries, and how boundary type relates to specific tectonic features, including mountain ranges, earthquakes, volcanism, volcanic islands, hotspots, mid-ocean ridges, and faults.

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Concrete Damage from Low pH Water

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