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

Gli acidi che interagiscono con il calcestruzzo dissolvono la pasta cementizia idrata, portando a un materiale ammorbidito e strutturalmente indebolito.
L'acidità rompe il calcestruzzo quando il pH dell'acqua scende al di sotto di 6,5 e il deterioramento accelera se il livello di pH scende al di sotto di 4,5.
L'acqua con 15-60 parti per milione di anidride carbonica, come l'acqua ghiacciata sciolta, può degradare il calcestruzzo. L'acqua torbosa con oltre 60 parti per milione di anidride carbonica è altamente corrosiva.
Le acque reflue domestiche, anche se alcaline, corrodono le fognature, soprattutto con il caldo, quando i batteri anaerobi trasformano i composti solforati in idrogeno solforato, che viene ossidato dai batteri anaerobici in acido solforico.
Anche la velocità di diffusione degli ioni idrogeno attraverso il gel di cemento influenza la velocità di attacco, soprattutto dopo che l'idrossido di calcio è stato disciolto e lavato via.
Gli attacchi dell'idrossido di calcio possono essere prevenuti stabilizzandolo con silicato di sodio diluito, che forma silicati di calcio nei pori del calcestruzzo.
L'applicazione di trattamenti superficiali come pece di catrame di carbone, vernici bituminose o di gomma e resine epossidiche si è dimostrata efficace per gli attacchi acidi generali.

attacco da acidi nel calcestruzzo

Quando gli acidi entrano in contatto con il calcestruzzo, innescano una reazione chimica che dissolve la pasta di cemento idratata. Questo processo porta all'ammorbidimento e all'indebolimento strutturale del calcestruzzo. Questo problema è comunemente osservato in ambienti come camini, fognature e ambienti industriali. La gravità del danno aumenta quando il pH dell'acqua che interagisce con il calcestruzzo scende sotto 6,5. In particolare, un pH inferiore a 4,5 può causare danni significativi al calcestruzzo.


 La velocità con cui gli ioni idrogeno si diffondono attraverso il gel di cemento influisce anche sulla velocità di attacco acido, particolarmente evidente dopo che l'idrossido di calcio nel calcestruzzo è stato sciolto e lavato via. Inoltre, l'acqua con livelli di anidride carbonica tra 15 e 60 parti per milione, come l'acqua ghiacciata sciolta, può degradare il calcestruzzo, mentre l'acqua torbosa con oltre 60 parti per milione di anidride carbonica può essere altamente corrosiva, riducendo eventualmente il pH a circa 4,4.


 Anche le acque reflue domestiche possono corrodere il calcestruzzo nelle fognature, in particolare in condizioni di caldo quando i batteri anaerobici convertono i composti di zolfo in idrogeno solforato. Per prevenire questi tipi di attacchi acidi, è utile stabilizzare l'idrossido di calcio con silicato di sodio diluito, che forma silicati di calcio protettivi nei pori del calcestruzzo. Oltre a questo, trattamenti superficiali come pece di catrame di carbone, vernici di gomma o bituminose e resine epossidiche si sono dimostrati efficaci nel combattere generici attacchi da acido nel calcestruzzo.

Attacco da acidi nel calcestruzzo

Gli acidi che interagiscono con il calcestruzzo dissolvono la pasta cementizia idrata, portando a un materiale ammorbidito e strutturalmente indebolito.
L'acidità rompe il ...

Education

Didattica

JoVE Core

Civil Engineering

Ingegneria Civile

Unit 1

Unità 1

Permeability of Concrete

Permeabilità del calcestruzzo

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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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a. Construct an evidence-based explanation of continental drift, basing conclusions on comparisons of coastlines, fossils, ages of rocks, climate, and magnetic patterns.

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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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c. Develop and interpret a model of Earth's internal structure and composition, including inner core, outer core, asthenosphere, lithosphere, mantle, and crust.

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d. Analyze data to interpret seismic activity and assess the risk of volcanic eruptions and earthquakes in Alabama and other areas in the United States.

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Concrete Damage from Low pH Water

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