Name: how cement particle size changes behavior
Uploaded: 2024-09-12T16:16:36.000Z
Duration: 1 min 15 s
Channel: JoVE

La curva de distribución de tamaño del cemento indica su finura al mostrar la proporción de partículas de diferentes tamaños. La curva se eleva abruptamente, lo que indica una porción significativa de partículas finas. Alrededor del 90 por ciento de las partículas de cemento son más pequeñas que 2,36 milésimas de pulgada.
La hidratación del cemento se inicia en la superficie de las partículas de cemento. Cuanto más fino es el cemento, mayor es la superficie, lo que conduce a una hidratación más rápida y un desarrollo de la fuerza.
La finura del cemento es el área superficial total de las partículas de cemento por unidad de peso del cemento.
La prueba de permeabilidad al aire de Blaine se usa comúnmente para determinar el área superficial específica del cemento.
Para esto, el cemento se empaqueta en una celda a una densidad específica y se crea un vacío parcial, lo que hace que se extraiga un volumen definido de aire a través del lecho de cemento. Se mide el tiempo necesario para esto y se calcula el área superficial específica del cemento.
Además, el tamizado en seco de una masa definida de cemento a través de un tamiz de 45 micras y la medición del peso del residuo retenido en el tamiz da la finura del cemento.

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finura del cemento

La finura del cemento influye directamente en la velocidad de hidratación, ya que la hidratación comienza en la superficie de las partículas de cemento. Además de la hidratación, la finura del cemento es vital para varias propiedades del hormigón, entre ellas la trabajabilidad, el requerimiento de yeso y el comportamiento a largo plazo. La finura del cemento se representa en términos de la superficie específica del cemento, que normalmente se mide en metros cuadrados por kilogramo, y existen varios métodos para esta determinación.

La medición directa de una superficie específica se puede realizar a través de la sedimentación o la elutriación, utilizando la ley de Stokes para encontrar la velocidad terminal de partículas esféricas en un fluido. Otro método implica el turbidímetro de Wagner, que estima la concentración de partículas en una suspensión y mide el área superficial de las partículas a través de la transmisión de luz.

Además, se utilizan métodos de permeabilidad al aire como el método de Lea y Nurse y el método de Blaine. El método de Lea y Nurse mide la caída de presión del aire que fluye a través de un lecho de cemento, relacionándola con la permeabilidad del lecho, que indirectamente proporciona el área superficial específica por unidad de masa de cemento. El método Blaine registra el tiempo que tarda un volumen conocido de aire en pasar a través del lecho de cemento a una velocidad constante, lo que también permite calcular el área de superficie específica.

Finura del cemento

La curva de distribución de tamaño del cemento indica su finura al mostrar la proporción de partículas de diferentes tamaños. La curva sube abruptamente, indicando ...

Education

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JoVE Core

Civil Engineering

Ingeniería Civil

Unit 1

Unidad 1

Introduction to Concrete

Introducción al concreto

KEY TERMS AND CONCEPTS

TÉRMINOS Y CONCEPTOS CLAVE

Fineness of Cement

how cement particle size changes behavior

Cement particle size changes how cement behaves in concrete. Finer cement has more surface area, so hydration starts faster at the particle surface. This affects the rate of hardening and also influences workability, gypsum requirement, and long-term behavior.

Cement fineness is usually described by its specific surface area. This is the total surface area of cement particles per unit mass, and it is often measured in square meters per kilogram. Several methods can be used to determine it, depending on the test setup.

Some methods measure the surface area directly. Sedimentation and elutriation use Stokes' law to calculate the terminal velocity of spherical particles in a fluid. The Wagner turbidimeter is another direct approach. It estimates particle concentration in a suspension and uses light transmission to measure particle surface area.

Other methods use air flow through a cement bed. The Lea and Nurse method measures the pressure drop of air and links it to bed permeability, which gives the specific surface area indirectly. The Blaine method measures how long a known volume of air takes to pass through the cement bed at a constant rate. That time is then used to calculate specific surface area.

How Cement Particle Size Changes Behavior

how-cement-particle-size-changes-behavior

concrete

Concrete Materials and Reinforcement

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portland cement

How Portland Cement Is Made

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strength and heat of hydration

Cement Hydration Heat and Strength Gain

Cement hydration produces heat and builds strength at the same time. Hydration is an exothermic reaction, which means it releases heat as cement reacts with water. That heat of hydration is a key part of how cement develops strength. Most of the heat is released early in the process. About half is given off in the first three days, and about 75% is released in the first week. The rate of heat release also affects how much the temperature rises during hydration. Some cement compounds...

fineness of cement

Cement particle size changes how cement behaves in concrete. Finer cement has more surface area, so hydration starts faster at the particle surface. This affects the rate of hardening and also influences workability, gypsum requirement, and long-term behavior. Cement fineness is usually described by its specific surface area. This is the total surface area of cement particles per unit mass, and it is often measured in square meters per kilogram. Several methods can be used to determine it,...

setting time of cement

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soundness of cement

Cement Expansion Tests for Soundness

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Cement Strength Tests and Standards

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key terms and concepts

Explore how cement particle size affects hydration, workability, gypsum requirement, and long-term behavior. Learn the main methods used to measure specific surface area.

How Cement Particle Size Changes Behavior | 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

How Cement Particle Size Changes Behavior

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