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

새로운 시멘트 페이스트가 굳으면 유체 상태에서 고체 덩어리로 전환되어 겔 워터, 모세관 물 및 결합 수와 같은 다양한 형태의 물을 가둡니다.
시멘트 겔의 공극 내에 갇혀 있는 겔 물은 일반적으로 시멘트 겔의 총 부피의 약 28%를 차지합니다.
건조 시멘트 덩어리의 약 23%는 수화 과정에서 발생하는 다양한 제품과 관련된 결합된 물로 구성됩니다.
시멘트 페이스트에 수화에 필요한 것보다 많은 물이 있는 경우 과도한 물은 원래 시멘트 부피의 약 18.5%를 차지하고 종종 물로 채워지는 모세관 공극을 형성합니다.
시멘트 페이스트의 전체 부피에 대한 겔과 모세관 기공의 결합된 부피의 비율은 시멘트 페이스트의 총 다공성을 결정합니다.
물 대 시멘트 비율은 과도한 물이 더 많은 모세관 기공을 생성하여 다공성을 높이고 잠재적으로 더 약한 경화 시멘트 페이스트로 이어지기 때문에 중요한 요소입니다.
적절한 경화는 지속적인 수분 공급을 허용하여 다공성을 줄일 수 있으며, 이는 모세 혈관 모공을 수분 제품으로 채웁니다.

콘크리트의 다공성

Porosity in Cement Paste

콘크리트의 다공성은 구조 내부의 공극을 측정하는 것입니다. 이러한 공극은 강도와 ​​내구성에 상당한 영향을 미칩니다. 물과 시멘트가 상호 작용하면 수화라는 화학 반응이 일어나 반고체 상태의 페이스트를 생성합니다. 이 페이스트에는 시멘트 건조 질량의 약 23%를 차지하는 결합수와 시멘트 겔 부피의 약 28%를 차지하는 겔수가 포함되어 있는데, 이는 겔 공극이라고도 알려진 미세한 공극을 채웁니다.


 혼합물에서 시멘트에 대한 물의 균형은 중요합니다. 이는 수화의 정도와 경화된 콘크리트의 다공성과 강도에 영향을 미칩니다. 이상적인 수화 공정에서 고체 수화 생성물이 차지하지 않는 여분의 공간은 모세관 공극을 형성하여 원래 시멘트 부피의 약 18.5%를 차지합니다. 콘크리트가 경화됨에 따라 지속적인 수화는 모세관 공극을 수화 생성물로 채워 재료의 밀도를 높일 수 있습니다.


 완전한 수화와 최적의 강도를 위해 경화 과정은 신중하게 관리해야 합니다. 이를 통해 추가 수화가 가능해지고 모세관 공간을 보다 안정적인 수화 제품으로 채워 다공성을 줄이고 결과적으로 페이스트를 농축할 수 있습니다. 이 세심한 과정은 환경 및 기계적 열화에 덜 취약한 내구성 있고 고품질의 콘크리트를 얻는 데 필수적입니다.

새로운 시멘트 페이스트가 굳으면 유체 상태에서 고체 덩어리로 전환되어 겔 워터, 모세관 물 등과 같은 다양한 형태의 물을 가둡니다.

Education

교육

JoVE Core

Civil Engineering

토목공학

Unit 1

제1단원

Strength of Concrete

콘크리트 강도

KEY TERMS AND CONCEPTS

핵심 용어 및 개념

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

Concrete tensile strength is limited by tiny cracks inside the material. The cement paste itself can be much stronger in theory than it is in practice. In real concrete, the measured strength can be up to a thousand times lower than the theoretical value. These small cracks help explain that gap. When a load is applied, stress rises at the crack tips. This idea is described by Griffith's theory of brittle fracture. In brittle materials, cracks can grow quickly once the stress at their tips...

behavior of concrete under compressive load

behavior-of-concrete-under-compressive-load

Concrete Failure Patterns Under Compression

Concrete failure patterns under compression show how the material responds to different kinds of direct stress. These patterns help explain concrete’s structural integrity. Under uniaxial compression, where force acts in one direction, cracks often form parallel to the load. These parallel cracks come from local tensile stress, which is pulling stress that appears perpendicular to the compression direction. As uniaxial loading continues, angled cracks may also appear. These cracks are linked...

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...

total voids in concrete

Concrete Voids and Strength

Concrete voids affect both strength and permeability. They include gel water, capillary pores, and entrapped air. In hydrated cement paste, gel water is held within the cement hydration products. Physically entrapped or adsorbed water also supports the hydration process. As cement hydrates, the space needed for the products from a cubic centimeter of cement is estimated to double. Capillary pores are the open spaces left inside the hydrated paste. Their size depends mainly on the...

pore size distribution

Concrete Porosity and Durability

Concrete porosity and durability depend strongly on pore size distribution in hardened cement paste. Capillary pores are much larger than gel pores, and in partially hydrated cement paste they form a connected network that lowers strength and raises permeability. Higher permeability makes concrete more vulnerable to freeze-thaw damage and chemical attack. The risk also depends on the water-to-cement ratio. A higher ratio can leave more space for capillary pores to remain open. As cement...

microcracking in concrete

How Concrete Cracks Before Failure

Concrete can develop tiny cracks before any outside load is applied. These microcracks usually form at the boundary between coarse aggregate and hydrated cement paste. They often result from small volume changes caused by stress-strain differences, heat, and moisture movement. At first, these microcracks stay stable. They usually do not grow much until the concrete reaches about 30 percent of its ultimate strength. As the load rises, the material can begin to change more quickly. When...

water cement ratio

Concrete Strength and Water Balance

Concrete strength depends on the balance between water and cement in the mix. This water-cement ratio is the weight of water compared with the weight of cement. It affects strength, durability, and how well concrete resists environmental stress. Abrams’ law shows that less water usually makes stronger concrete. Water is still needed for hydration, which is the chemical process that binds water and cement. It also helps the mix stay workable and compactable. Some water must be absorbed into the...

aggregate cement ratio

How Mix Ratio Changes Concrete Strength

The aggregate cement ratio changes how concrete performs. It is the weight of aggregate divided by the weight of cement in a concrete mix. This ratio affects strength, workability, and durability, so it is an important part of concrete design. A higher aggregate cement ratio makes the mix leaner. Lean mixes have less cement paste to coat and lubricate the aggregate, so they can be harder to work with. At the same time, they may increase strength because the concrete has less total porosity, or...

transition zone

Concrete Transition Zone and Its Porosity

The concrete transition zone is the thin region where aggregate meets cement paste. It has more pores than the surrounding material, so it is usually weaker at first. The bond around the aggregate comes mainly from Van der Waals forces, which are weak attraction forces between particles. When concrete is compacted, this zone often has a higher water-cement ratio near the aggregate. That extra water can form thin water films around the coarse aggregate. These films increase porosity and help...

relation between tensile strength and compressive strength of concrete

relation-between-tensile-strength-and-compressive-strength-of-concrete

Concrete Strength Testing: Tension vs. Compression

Concrete strength testing compares tensile strength and compressive strength. These two properties are related, but they do not rise at the same rate. Tensile strength usually grows more slowly than compressive strength, so the balance between them changes as concrete gets stronger. Several factors affect tensile strength measurements. The test method, specimen size and shape, aggregate texture, and moisture content can all change the result. Direct tension tests are difficult to perform...

fatigue strength of concrete

Concrete Fatigue Under Repeated Loads

Concrete fatigue describes how concrete can weaken or fail when loads are applied again and again, even when each load is below the material’s strength limit. This property matters because it affects the durability and service life of concrete structures. In materials science and engineering, fatigue is a key reason concrete may not last as long as expected under real use. Concrete can fail in two main ways through fatigue. Static fatigue, also called creep rupture, happens under a constant...

impact strength of concrete

Concrete Impact Resistance in Real Use

Concrete impact resistance matters when a material must handle repeated blows and sudden loads. It is important during pile driving, where concrete piles are driven into the ground. It also matters for machinery foundations that experience impulsive loads and for precast concrete parts that can be damaged during handling. Impact strength is measured by checking how well concrete absorbs energy from repeated impacts. A major sign of serious damage is when the concrete does not rebound after...

abrasion resistance of concrete

Concrete Wear Tests and Surface Durability

Concrete wear tests show how well a surface can stand up to abrasion and long-term use. Abrasion is the wearing away of a material by rubbing, scraping, or contact with moving solids. This property matters because concrete surfaces can lose material under vehicle traffic or when solids carried in water brush against them. The transcript describes three tests used to measure concrete abrasion resistance. In the revolving disc test, three plates rotate against the concrete, and silicon carbide...

reinforcements in concrete

Steel Bars in Concrete Structures

Steel bars in concrete structures help the material carry both compression and tension. Concrete is strong when it is squeezed, but it is weak when pulled. Rebar, or reinforcing steel bars, is placed inside the concrete to handle those tensile forces. Steel is a practical choice because it has a similar coefficient of thermal expansion to concrete. That means both materials expand and contract in a similar way as temperature changes. The steel used for reinforcement is usually made by a...

fiber reinforced concrete

Concrete Strength with Added Fibers

Fiber-reinforced concrete is concrete that includes added fibers to improve strength and durability. It uses hydraulic cement with fine or coarse aggregates, plus separated, non-continuous fibers mixed through the material. These fibers can come from steel, glass, and polymers, as well as natural sources such as sisal and cellulose or manufactured sources such as polypropylene and Kevlar. Steel fibers are often preferred because they are strong and tough. They help concrete resist cracking and...

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

Ferrocement is a construction material made from dense layers of mesh or fine rods covered fully in cement mortar. It is a form of reinforced concrete, but it uses mesh instead of the larger steel bars found in standard reinforced concrete. This structure gives ferrocement its thin, flexible form. The material is built from wire meshes and a mortar made of cement and sand. The mortar is usually mixed in a 1:2 or 1:3 ratio. The water-to-cement ratio is kept between 0.40 and 0.45. This helps the...

non-destructive tests for concrete strength

non-destructive-tests-for-concrete-strength

Concrete Strength Checks Without Breaking It

Concrete strength can be checked without fully breaking the material. Two common methods are the rebound hammer test, also called the Schmidt hammer test, and the penetration resistance test, also called the Windsor Probe test. Both are used to estimate the strength of existing concrete. The rebound hammer test measures the hardness of the concrete surface and gives an indirect clue about strength. A spring-driven mass moves inside a tubular housing and strikes a plunger against the concrete.

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 offers a foundational exploration of essential construction materials such as bricks, stones, steel, wood, and concrete, along with fluid mechanics topics like flow over immersed bodies, open channel flow, and dimensional modeling. It also covers key surveying concepts, including leveling, traverse adjustments, curve design, topographic mapping, and geospatial technologies (GPS & GIS). Science-in-action videos showcase laboratory research on materials, fluids, and surveying practices in real-world engineering systems.

civil engineering

How Cement Curing Changes Porosity

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