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

시멘트와 물의 반응으로 수분 공급 제품을 생성하면 수화 열로 알려진 열이 방출됩니다.
처음에는 시멘트에 알루미네이트와 규산염이 수화되어 있기 때문에 발열이 빠릅니다. 수화 제품이 규산염을 코팅함에 따라 급격한 감소가 뒤따르고, 코팅이 용해된 후 잔류 규산염이 반응함에 따라 점진적으로 증가하고, 수화가 느려짐에 따라 감소하고 결국 안정화됩니다.
시멘트의 화합물은 수화열에 기여합니다. C3A가 가장 많이 기여하고 C2S가 가장 적게 기여합니다.
포틀랜드 시멘트의 경우 총 열의 약 50%가 1일에서 3일 사이에, 약 75%가 7일 동안에, 거의 90%가 6개월 내에 방출됩니다.
시멘트에서 규산염이 수화되는 동안 형성된 C-S-H는 시멘트의 강도에 기여합니다.
시간이 지남에 따라 수화 시멘트의 강도 변화를 고려할 때 C3S의 수화는 처음 4주 동안 강도 개발에 더 많이 기여하는 반면 C2S의 수화는 그 이후에 얻은 강도에 기여합니다.
그러나 약 1년이 지나면 C3S와 C2S의 수분 공급이 근력 향상에 동등하게 기여합니다.
대조적으로, C3A 및 C4AF의 수화는 강도에 거의 기여하지 않습니다.

강도와 수화열

Strength and Heat of Hydration

시멘트의 수화반응은 시멘트가 수화되면서 열이 생성되는 발열 반응입니다. 수화열은 시멘트의 강도 발달에 중요합니다. 열이 생성되는 속도는 온도 상승에 영향을 미치며, 대부분의 열은 수화 과정 초기에 방출되는데, 절반은 처음 3일 이내에 방출되고, 약 75%는 첫 주 이내에 방출됩니다.

각 시멘트 화합물의 수화열은 중요합니다. 예를 들어, 삼알루미늄칼슘(C_3A)과 삼규산칼슘(C_3S)이 이 과정에 가장 많이 기여합니다. 표 1은 C_3S, C_2S, C_2A, C_4A와 같은 시멘트 화합물의 수화열을 요약한 것을 나타냅니다. 이러한 화합물의 비율을 조정하면 시멘트 수화 중에 방출되는 열의 속도와 총량을 관리할 수 있습니다.

표 1. 시멘트 화합물의 수화열

<div style="text-align: center; display: flex; align-items: center; justify-content: center;">
<table style="text-align: center;" border="1">
 <tbody>
 <tr>
 <td>화합물</td>
 <td>수화열(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>

수화된 시멘트의 강도 발달은 주로 삼규산칼슘(C_3S)과 이규산칼슘(C_3S)의 영향을 받습니다. C_3S는 수화 후 처음 4주 동안 강도에 상당히 기여하는 반면, C_2S는 특히 1년 이후 장기 강도 증가에 더 중요한 역할을 합니다. 1년 후에 두 화합물은 질량 대 질량 기준으로 시멘트의 전체 강도에 동등하게 기여합니다.

시멘트와 물의 반응으로 수분 공급 제품을 생성하면 수화 열로 알려진 열이 방출됩니다.
처음에는 열 발생이 빠릅니다.

Education

교육

JoVE Core

Civil Engineering

토목공학

Unit 1

제1단원

Introduction to Concrete

콘크리트 입문

KEY TERMS AND CONCEPTS

주요 용어 및 개념

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

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 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

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,...

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

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 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

Cement Hydration Heat and Strength Gain

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