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

시멘트의 크기 분포 곡선은 다양한 크기의 입자의 비율을 보여줌으로써 시멘트의 섬도를 나타냅니다. 곡선은 가파르게 상승하여 미세 입자의 상당 부분을 나타냅니다. 시멘트 입자의 약 90%는 2.36mils보다 작습니다.
시멘트의 수화는 시멘트 입자의 표면에서 시작됩니다. 시멘트가 미세할수록 표면적이 넓어져 수화 속도가 빨라지고 강도가 발달합니다.
시멘트의 섬세함은 시멘트의 단위 중량당 시멘트 입자의 총 표면적입니다.
Blaine 통기성 테스트는 일반적으로 시멘트의 비표면적을 결정하는 데 사용됩니다.
이를 위해 시멘트가 특정 밀도로 셀에 포장되고 부분적인 진공이 생성되어 시멘트 베드를 통해 일정한 양의 공기가 흡입됩니다. 이를 위해 소요되는 시간을 측정하고 시멘트의 비표면적을 계산합니다.
또한 45미크론 체를 통해 일정한 질량의 시멘트를 건조 체질하고 체에 남아 있는 잔류물의 무게를 측정하면 시멘트의 섬세함을 얻을 수 있습니다.

시멘트의 분말도

수화는 시멘트 입자 표면에서 시작되기 때문에 시멘트의 분말도는 수화 속도에 직접적인 영향을 미칩니다. 분말도는 수화 외에도 작업성, 석고 요구량 및 장기적 특성 등 포함한 콘크리트의 다양한 특성에 필수적인 역할을 합니다. 시멘트의 분말도은 일반적으로 킬로그램당 제곱미터로 측정되는 시멘트의 비표면적으로 표현되며, 이를 측정하는 여러 가지 방법이 있습니다.

비표면적의 직접 측정은 침전 또는 세굴을 통해 수행할 수 있으며, 스토크스 법칙을 사용하여 유체에서 구형 입자의 최종 속도를 찾습니다. 또 다르게 와그너 탁도계를 사용할 수 있으며, 이는 현탁액의 입자 농도를 추정하고, 광 투과를 통해 입자의 표면적을 측정하는 방법입니다.

또한 레아 너스 방법 및 블레인 방법과 같이 공기 투과성 방법이 사용될 수 있습니다. 레아 너스 방법은 시멘트 베드를 통과하는 공기의 압력 강하를 측정하여 베드의 투과성과 연관시키고, 이를 통해 간접적으로 시멘트 단위 질량당 비표면적을 제공합니다. 블레인 방법은 알려진 양의 공기가 일정한 속도로 시멘트 베드를 통과하는 데 걸리는 시간을 기록하여 비표면적을 계산합니다.

시멘트의 크기 분포 곡선은 다양한 크기의 입자의 비율을 보여줌으로써 시멘트의 섬도를 나타냅니다. 곡선이 가파르게 상승하여 ...

Education

교육

JoVE Core

Civil Engineering

토목공학

Unit 1

제1단원

Introduction to Concrete

콘크리트 입문

KEY TERMS AND CONCEPTS

주요 용어 및 개념

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

Concrete is a major construction material used in buildings, bridges, airfields, highways, dams, and silos. It is valued for strength, durability, and versatility in many structural designs. A concrete mix usually includes Portland cement, coarse gravel, fine sand, and water. Concrete can be mixed by hand or made at industrial plants with computer control. The mix has aggregates and a paste made from water and Portland cement. This paste coats the aggregates. Through hydration, a chemical...

portland cement

How Portland Cement Is Made

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...

hydration of cement

Cement Setting and Strength Formation

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 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

Cement Initial and Final Set

Cement setting time describes how cement paste changes from a plastic state to a solid state. This change matters in construction because it sets the window for placing, compacting, and finishing concrete. The first stage is called the initial set. At that point, the paste becomes unworkable. The next stage is the final set. By then, the paste has solidified completely, and further handling can no longer change its shape. Cement strength is still very low at this stage because hydration of...

soundness of cement

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...

types of cement i

Portland Cement Grades and Uses

Portland cement comes in several grades with different properties and uses. Its chemical composition and hydration behavior help determine how it performs in concrete. These differences matter in general construction, fast repairs, large structures, and places where sulfate exposure is a concern. Type I, or Ordinary Portland Cement, is the common choice for general construction. It is used when special properties are not required. This type has moderate sulfate resistance and moderate heat of...

types of cement ii

Special Portland Cements for Durability

Special Portland cements are made for specific building needs, such as added durability, color, or lower cracking risk. One major example is Portland blast-furnace cement. It is made by blending Portland cement clinker with granulated blast-furnace slag, which makes up about 25 to 65 percent of the cement by weight. Portland blast-furnace cement sets at about the same rate and has about the same fineness as ordinary Portland cement, which is Type I cement. Its early strength is lower, but it...

pozzolans

Pozzolans in Stronger Concrete Mixes

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

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 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 Particle Size Changes Behavior

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