Name: how cement curing changes porosity
Uploaded: 2024-11-07T14:48:30.000Z
Duration: 1 min 18 s
Channel: JoVE

По мере схватывания свежей цементной пасты она переходит из жидкого состояния в твердую массу, захватывая воду в различных формах, таких как гелевая вода, капиллярная вода и комбинированная вода.
Гелевая вода, которая задерживается в порах цементного геля, обычно составляет примерно 28% от общего объема цементного геля.
Около 23% массы сухого цемента состоит из комбинированной воды, которая связана с различными продуктами, образующимися в процессе гидратации.
Когда в цементной пасте больше воды, чем необходимо для гидратации, избыток воды образует капиллярные поры, которые составляют около 18,5% от первоначального объема цемента и часто заполняются водой.
Отношение совокупного объема гелевых и капиллярных пор к общему объему цементной пасты определяет общую пористость цементной пасты.
Соотношение воды и цемента является решающим фактором, так как избыток воды создает больше капиллярных пор, что приводит к более высокой пористости и потенциально более слабой затвердевшей цементной пасте.
Правильное отверждение может уменьшить пористость, обеспечивая непрерывное увлажнение, которое наполняет капиллярные поры продуктами увлажнения.

Пористость бетона

Porosity in Cement Paste

Пористость бетона — это мера пустот в его структуре. Эти пустоты существенно влияют на его прочность и долговечность. Когда вода и цемент взаимодействуют, химическая реакция, называемая гидратацией, создает полутвердую пасту. Эта паста включает связанную воду, составляющую приблизительно 23% сухой массы цемента, и гелеобразную воду, которая заполняет крошечные пустоты, известные как гелевые поры, составляя около 28% объема цементного геля.

Баланс воды и цемента в смеси имеет решающее значение — он влияет на степень гидратации и, таким образом, на пористость и прочность затвердевшего бетона. В идеальном процессе гидратации дополнительное пространство, не занятое твердыми продуктами гидратации, образует капиллярные поры, составляющие около 18,5% от первоначального объема цемента. По мере затвердевания бетона непрерывная гидратация может заполнять капиллярные поры продуктами гидратации, увеличивая плотность материала.

Для полной гидратации и оптимальной прочности процесс отверждения должен тщательно контролироваться. Это позволяет проводить дополнительную гидратацию, уменьшая пористость путем заполнения капиллярных пространств более стабильными продуктами гидратации и, как следствие, уплотнения пасты. Этот сложно организованный процесс имеет решающее значение для получения прочного, высококачественного бетона, который менее подвержен деградации под воздействием окружающей среды и механических факторов.

По мере схватывания свежей цементной пасты она переходит из жидкого состояния в твердую массу, захватывая воду в различных формах, таких как гелевая вода, капиллярная вода и ...

Education

JoVE Core

Civil Engineering

Unit 1

Раздел 1

Strength of Concrete

Прочность бетона

KEY TERMS AND CONCEPTS

ОСНОВНЫЕ ТЕРМИНЫ И ПОНЯТИЯ

how cement curing changes porosity

Cement curing changes porosity in the hardened paste. Porosity means the void spaces inside concrete. These spaces affect both strength and durability. When water and cement react, hydration forms a semi-solid paste that traps water in different ways.

Some of that water becomes combined water. It makes up about 23% of the cement's dry mass. Other water stays as gel water, which fills very small voids called gel pores. Gel pores account for about 28% of the cement gel volume.

The water-to-cement ratio is important in the mix. It controls how much hydration can happen. That, in turn, affects the porosity and strength of the cured concrete. In an ideal hydration process, the space not filled by solid hydration products becomes capillary pores, which are about 18.5% of the original cement volume.

As concrete cures, hydration can continue. More hydration products can fill the capillary pores and make the material denser. Careful curing helps complete this process and reduces porosity. The result is durable, high-quality concrete that is less likely to break down under environmental and mechanical stress.

How Cement Curing Changes Porosity

tensile strength considerations of concrete

tensile-strength-considerations-of-concrete

How Cracks Limit Concrete Strength

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behavior-of-concrete-under-compressive-load

Concrete Failure Patterns Under Compression

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porosity in cement paste

Cement curing changes porosity in the hardened paste. Porosity means the void spaces inside concrete. These spaces affect both strength and durability. When water and cement react, hydration forms a semi-solid paste that traps water in different ways. Some of that water becomes combined water. It makes up about 23% of the cement's dry mass. Other water stays as gel water, which fills very small voids called gel pores. Gel pores account for about 28% of the cement gel volume. The...

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Concrete Porosity and Durability

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water cement ratio

Concrete Strength and Water Balance

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aggregate cement ratio

How Mix Ratio Changes Concrete Strength

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transition zone

Concrete Transition Zone and Its Porosity

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Concrete Strength Testing: Tension vs. Compression

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Concrete Fatigue Under Repeated Loads

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abrasion resistance of concrete

Concrete Wear Tests and Surface Durability

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fiber reinforced concrete

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prestressed concrete

How Concrete Is Preloaded for Strength

Prestressed concrete is a construction method that preloads concrete so it can handle more stress. High-strength steel strands are stretched before or after the concrete is loaded in service. The goal is to put the concrete into compression. That compression helps balance the tension the structure will face later. By reducing tension, prestressing helps limit cracks in the concrete. It can also let a structure carry greater loads or span longer distances than conventional reinforced concrete.

ferrocement

Ferrocement Mesh and Mortar Design

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non-destructive tests for concrete strength

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key terms and concepts

Learn how hydration, gel water, and capillary pores affect cement paste porosity, strength, and durability as concrete cures.

How Cement Curing Changes Porosity | 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 Curing Changes Porosity

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