Name: concrete durability and water penetration
Uploaded: 2024-11-07T14:48:45.000Z
Duration: 1 min 25 s
Channel: JoVE

La permeabilidad se refiere a la facilidad con la que los líquidos o gases pueden moverse a través del hormigón. Esta característica es relevante para garantizar la impermeabilidad de las estructuras que retienen el líquido y resisten la degradación química.
La permeabilidad del hormigón se evalúa con una prueba básica de laboratorio, en la que se sellan todos los lados, excepto la parte superior de una muestra de hormigón. A continuación, se aplica agua a presión en la superficie superior.
Al alcanzar un estado estacionario, que puede tardar alrededor de diez días, se registra el volumen de agua que ha penetrado a través de un espesor determinado del hormigón durante un período específico.
En el caso del hormigón, que consiste en agregados estándar de peso normal, la permeabilidad está determinada por la porosidad de la pasta de cemento.
La permeabilidad de la pasta de cemento hidratada no solo está determinada por el pequeño tamaño de los poros dentro del gel, sino que también está influenciada por la presencia de poros capilares más grandes.
A medida que avanza la hidratación, la permeabilidad de la pasta de cemento disminuye porque algunos de los espacios originalmente llenos de agua están cerrados.
A proporciones de agua a cemento más bajas, generalmente por debajo de 0.6, la permeabilidad disminuye porque los capilares se segmentan o rompen, impidiendo el flujo de fluido.

permeabilidad del hormigón

Permeability of Concrete

La permeabilidad en el contexto del hormigón se refiere a la facilidad con la que los líquidos o gases pueden atravesar el material. Esta cualidad es crucial para evaluar la impermeabilidad y durabilidad de las estructuras de hormigón y su resistencia a los ataques químicos. La permeabilidad del hormigón se puede determinar mediante ensayos comparativos de laboratorio. Estos ensayos suelen implicar sellar una muestra de hormigón por los lados, aplicar presión de agua a la superficie superior y medir la cantidad de agua que pasa a través de ella, a menudo alrededor de diez días, hasta que se alcanza un estado estable.

La permeabilidad del hormigón no solo está influenciada por la relación agua/hormigón y el grado de hidratación, sino también por la porosidad de la pasta de hormigón, que varía con la distribución del tamaño de los poros. La porosidad capilar juega un papel importante, ya que los capilares segmentados reducen la permeabilidad en comparación con los interconectados. A medida que la pasta de cemento continúa hidratándose, su permeabilidad disminuye debido al cierre de los huecos inicialmente ocupados por el agua. Para un hormigón duradero, es ventajoso tener una relación agua/hormigón más baja, lo que ayuda a lograr una permeabilidad más baja antes.

También se observa que la mezcla de hormigón debe ser densa y utilizar agregados bien calibrados para reducir la permeabilidad. Además, factores como los métodos de curado y el tamaño de los agregados pueden afectar la permeabilidad; el hormigón curado con vapor suele tener una permeabilidad mayor que el curado con humedad, a menos que se lo someta a condiciones de curado específicas, como el curado con niebla, para alcanzar los niveles de permeabilidad bajos deseados.

Permeabilidad del hormigón

La permeabilidad se refiere a la facilidad con la que los líquidos o gases pueden moverse a través del hormigón. Esta característica es relevante para garantizar la impermeabilidad ...

Education

Educación

JoVE Core

Civil Engineering

Ingeniería Civil

Unit 1

Unidad 1

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

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 state is reached.

Several features of the concrete mix affect permeability. The water/cement ratio and the degree of hydration both matter. The porosity of the cement paste also plays a major role. Pore size distribution is important, and capillary porosity can change how easily water moves through the material.

Interconnected capillaries allow more flow than segmented capillaries, which reduce permeability. As cement paste hydrates, its permeability drops because voids that once held water are gradually closed. For more durable concrete, a lower water/cement ratio helps the mix reach low permeability sooner. A dense mix with well-graded aggregate also helps reduce permeability. Curing and aggregate size matter too. Steam-cured concrete usually has higher permeability than moist-cured concrete, although fog curing can be used in some cases to reach low permeability levels.

Concrete Durability and Water Penetration

concrete-durability-and-water-penetration

permeability of concrete

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

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 water moves through concrete, how permeability is tested in the lab, and why mix design and curing affect durability and water-tightness.

Concrete Durability and Water Penetration | 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

Concrete Durability and Water Penetration

Description

Transcript

Tags