Name: cement hydration heat and strength gain
Uploaded: 2024-09-12T16:16:35.000Z
Duration: 1 min 29 s
Channel: JoVE

La reacción del cemento con el agua para producir productos de hidratación libera calor, conocido como calor de hidratación.
Inicialmente, la generación de calor es rápida debido a la hidratación de aluminatos y silicatos en el cemento. A medida que los productos de hidratación recubren los silicatos, se produce un aumento gradual a medida que los silicatos restantes reaccionan después de la disolución del recubrimiento, seguido de una disminución y una eventual estabilización a medida que la hidratación se ralentiza.
Los compuestos del cemento contribuyen a su calor de hidratación; C3A es el que más contribuye y el C2S el que menos.
En el caso del cemento Portland, alrededor del cincuenta por ciento del calor total se libera entre uno y tres días, alrededor del setenta y cinco por ciento en siete días y casi el noventa por ciento en seis meses.
El C-S-H formado durante la hidratación de los silicatos en el cemento contribuye a su resistencia.
Teniendo en cuenta la variación en la resistencia del cemento hidratado con el tiempo, la hidratación de C3S contribuye más al desarrollo de la fuerza durante las primeras cuatro semanas, mientras que la hidratación del C2S contribuye a la fuerza ganada a partir de entonces.
Sin embargo, alrededor de un año, la hidratación de C3S y C2S contribuye igualmente a la ganancia de fuerza.
Por el contrario, la hidratación de C3A y C4AF contribuye poco a la fuerza.

No se han declarado conflictos de interés.

resistencia y calor de hidratación

Strength and Heat of Hydration

La hidratación del cemento es una reacción exotérmica en la que se genera calor a medida que el cemento se hidrata. Este calor de hidratación es fundamental para el desarrollo de la resistencia del cemento. La velocidad a la que se genera este calor afecta el aumento de temperatura, ya que la mayor parte del calor se libera al principio del proceso de hidratación, la mitad en los primeros tres días y aproximadamente el 75 % en la primera semana.

El calor de hidratación de cada compuesto de cemento es significativo; por ejemplo, el aluminato tricálcico (C_3A) y el silicato tricálcico (C_3S) son los que más contribuyen a este proceso. La Tabla 1 resume el calor de hidratación de compuestos de cemento como C_3S, C_2S, C_3A y C_4AF. Ajustar las proporciones de estos compuestos puede controlar la velocidad y la cantidad total de calor liberado durante la hidratación del cemento. 

Tabla 1. Calor de hidratación de los compuestos de cemento


<div style="text-align: center; display: flex; align-items: center; justify-content: center;">
<table style="text-align: center;" border="1">
 <tbody>
 <tr>
 <td>Compuesto</td>
 <td>Calor de hidratación (J/kg)</td>
 </tr>
 <tr>
 <td>C_3A</td>
 <td>867</td>
 </tr>
 <tr>
 <td>C_3S</td>
 <td>502</td>
 </tr>
 <tr>
 <td>C_4AF</td>
 <td>419</td>
 </tr>
 <tr>
 <td>C_2S</td>
 <td>260</td>
 </tr>
 </tbody>
</table>
</div>

El desarrollo de la resistencia del cemento hidratado está influenciado principalmente por los compuestos silicato tricálcico (C_3S) y silicato dicálcico (C_3S). El C_3S contribuye significativamente a la resistencia durante las primeras cuatro semanas posteriores a la hidratación, mientras que el C_2S desempeña un papel más crucial en las ganancias de resistencia a largo plazo, especialmente después del primer año. Después de un año, ambos compuestos, cuando se consideran en términos de masa por masa, contribuyen por igual a la resistencia general del cemento.

Resistencia y calor de hidratación

La reacción del cemento con el agua para producir productos de hidratación libera calor, conocido como calor de hidratación.
Inicialmente, la generación de calor es rápida ...

Education

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Civil Engineering

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Unit 1

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Introduction to Concrete

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KEY TERMS AND CONCEPTS

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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 contribute more heat than others. Tricalcium aluminate, or C3A, and tricalcium silicate, or C3S, are the main contributors. Table 1 shows the heat of hydration for C3A, C3S, C4AF, and C2S. Their values are 867 J/kg, 502 J/kg, 419 J/kg, and 260 J/kg, respectively. By changing the amounts of these compounds, it is possible to control both the rate and the total heat released.

Strength development depends mostly on tricalcium silicate, C3S, and dicalcium silicate, C2S. C3S is important for early strength during the first four weeks after hydration. C2S becomes more important for long-term strength gain, especially after the first year. After one year, both compounds contribute equally to cement strength on a mass-for-mass basis.

Cement Hydration Heat and Strength Gain

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Portland cement is the main binding material in concrete. It is made from finely ground ingredients that include lime, iron, silica, and alumina. These materials give cement the properties it needs to hold concrete together. The raw ingredients come from several common natural sources. Lime is obtained mainly from limestone, marble, marl, seashells, and clays. Those same clays can also supply iron and alumina. Silica is sourced from sand, chalk, and bauxite. Making Portland cement starts by...

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Cement setting and strength formation begin when water is added to cement particles. The main reaction is called hydration. During hydration, the anhydrous cement compounds react with water and form new solids that help harden the material. Hydration can happen by two main paths: through-solution and topochemical. In through-solution, anhydrous compounds dissolve into their parts, hydrates form in the liquid, and then they come out of a supersaturated solution. In topochemical hydration,...

strength and heat of hydration

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...

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Cement Expansion Tests for Soundness

Cement soundness is the ability of cement paste to keep its volume after it sets. If cement is unsound, it can expand later and damage a structure. This problem can come from free lime, magnesia, and calcium sulfate in the cement. Free lime hydrates very slowly. As it reacts, it can expand and cause unsoundness. It is also hard to detect because it intercrystallizes with other compounds in the cement structure. Magnesia can also react with water. It forms crystals that may disrupt the cement...

strength of cement

Cement Strength Tests and Standards

Cement strength is measured with standard tests that use mortar, not neat cement paste. Cement paste alone is hard to shape into specimens that give consistent and reliable results. For that reason, the test samples are usually made with cement and sand. For compressive strength, ASTM C 109-05 uses a cement-sand mix ratio of 1:2.75 and a water/cement ratio of 0.485. The mixture is cast into 2-inch cubes and cured in saturated lime water at 23°C until testing. This method measures how well the...

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Pozzolans are siliceous or aluminous materials used with Portland cement to improve concrete performance. They react with the calcium hydroxide formed during cement hydration. This reaction helps increase strength and durability. The usefulness of a pozzolan is measured by its pozzolanic activity. One common test is the strength activity index from ASTM C 618-93. It compares the compressive strength of cement mixtures made with and without pozzolan. Fly ash is a common artificial pozzolan. It...

key terms and concepts

Learn how cement hydration releases heat, raises temperature, and drives strength gain. See how C3A, C3S, and C2S affect early and long-term strength.

Cement Hydration Heat and Strength Gain | 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

Cement Hydration Heat and Strength Gain

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