Name: cement strength tests and standards
Uploaded: 2024-09-12T16:16:36.000Z
Duration: 1 min 20 s
Channel: JoVE

압축력에 저항하는 시멘트의 능력은 압축 강도로 알려져 있으며, 굽힘력을 견디는 능력은 굴곡 강도라고 합니다.
시멘트, 표준 모래 및 물을 필요한 비율로 취하여 혼합하여 시멘트 모르타르를 형성합니다.
이 모르타르는 2인치 입방체 표본과 1.5 x 1.57 x 6.3인치 크기의 빔 표본으로 주조됩니다.
이 표본은 탈형될 수 있을 때까지 습한 환경에서 경화됩니다.
탈형된 시편은 테스트할 때까지 석회수에서 추가로 경화됩니다. 표본은 일반적으로 경화 1일, 3일, 7일, 28일 후에 테스트됩니다.
시험에는 압축 시험을 위한 큐브와 굴곡 시험을 위한 빔을 기계에 배치하고 시편이 파손될 때까지 하중을 꾸준히 증가시키는 작업이 포함됩니다.
시편이 파손되는 하중은 시멘트 모르타르의 압축 강도와 굴곡 강도를 계산하는 데 사용됩니다.
마지막으로, 사용되는 시멘트의 종류는 시멘트 모르타르의 압축 강도에 큰 영향을 미칩니다.

시멘트 강도

시멘트 강도 시험은 일관되고 신뢰할 수 있는 시편을 얻는 데 어려움이 있으므로 순수한 시멘트 페이스트에서 직접 수행되지 않습니다. 대신, 일반적으로 시멘트-모래 모르타르 형태로 시험됩니다.

압축 강도 시험의 경우, ASTM C 109-05 표준은 5.08 센티미터 큐브를 만드는 데 시멘트-모래 혼합 비율을 1:2.75로, 물/시멘트 비율을 0.485로 규정합니다. 이러한 큐브는 시험할 때까지 23°C의 포화 석회수에서 혼합, 주조, 경화됩니다. ASTM C 348-02에 설명하는 휨 강도 시험은 3.81 x 3.99 x 16 센티미터 크기의 프리즘을 사용하여 단순 지지한 후에 중앙부에 하중을 가하는 방식입니다. 시멘트의 압축 강도를 결정하는 또 다른 방법은 ASTM C 349-02에 자세히 설명된 수정된 큐브 시험입니다. 이 시험은 휨 프리즘 시험 중 파손된 프리즘의 단면을 사용하여 압축 강도를 시험합니다.

ASTM C150은 시간이 지남에 따라 다양한 유형의 시멘트에 대한 최소 압축강도 값을 규정합니다. 영국 표준 BS EN 196-1: 2005는 시멘트를 강도 등급으로 분류합니다. 예를 들어 일반 시멘트는 N 등급, 빠른 경화 특성을 가진 시멘트는 R 등급입니다.

압축력에 저항하는 시멘트의 능력은 압축 강도로 알려져 있으며, 굽힘력을 견디는 능력은 ...

Education

교육

JoVE Core

Civil Engineering

토목공학

Unit 1

제1단원

Introduction to Concrete

콘크리트 입문

KEY TERMS AND CONCEPTS

주요 용어 및 개념

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 material resists crushing forces.

Flexural strength is tested by ASTM C 348-02. Flexural strength means resistance to bending. The test uses prisms that measure 1.5 x 1.57 x 6.3 inches. The prism is simply supported and loaded at mid-span, which applies force at the center.

Another compressive strength method is the modified cube test in ASTM C 349-02. This test uses sections of the failed flexural prisms to check compression. ASTM C150 also gives minimum compressive strength values for different cement types at different ages. In British Standard BS EN 196-1: 2005, cement is grouped into strength classes such as N for normal and R for rapid hardening.

Cement Strength Tests and Standards

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

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 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 strength is measured with mortar cubes, flexural prisms, and ASTM and British standards used to classify compressive strength.

Cement Strength Tests and Standards | 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 Strength Tests and Standards

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