Name: concrete impact resistance in real use
Uploaded: 2024-11-07T14:48:31.000Z
Duration: 1 min 21 s
Channel: JoVE

핸들링하는 동안 프리캐스트 콘크리트 요소에 갑작스러운 하중이나 의도하지 않은 충격을 견디는 기계의 경우 충격이나 콘크리트 기초로 콘크리트 말뚝을 지면에 박는 것을 고려하십시오.
콘크리트는 이러한 충격을 견딜 수 있는 충분한 강도를 가져야 합니다. 콘크리트의 충격 강도를 평가하려면 반복적인 충격에 대한 저항과 에너지를 흡수하는 능력을 결정하는 것이 포함됩니다.
특히, 콘크리트가 반동을 나타내지 않기 전에 견디는 충격의 수는 심각한 손상을 나타냅니다.
충격 강도는 더 각진 모양과 더 거친 표면을 가진 거친 골재를 사용하는 혼합물에서 증가하며, 이는 굽힘 강도와의 관계를 나타냅니다.
콘크리트의 충격과 압축 강도는 골재 유형과 저장 조건에 따라 관련이 있으며 다양합니다. 예를 들어, 물에 저장된 콘크리트는 건조한 조건에서 저장된 콘크리트보다 충격 강도가 낮습니다.
최대 골재 크기와 골재를 더 낮은 포아송 비율과 더 낮은 탄성 계수로 줄이면 콘크리트의 충격 강도를 향상시킬 수 있습니다.
적절한 충격 강도를 위해 콘크리트 혼합물에서 입방 야드당 670파운드 미만의 시멘트 함량을 사용하는 것이 좋습니다.

콘크리트의 충격 강도

Impact Strength of Concrete

콘크리트의 충격 강도는 말뚝 박기의 경우나 충격 하중을 받는 기계 기초를 지지할 때 재료가 가해지는 힘을 견딜 수 있는 능력을 반영하는 중요한 척도입니다. 또한 프리캐스트 콘크리트 구성 요소를 취급할 때 우발적인 손상을 방지하는 데 필수적입니다. 충격 강도는 콘크리트의 반복적인 충격에 대한 저항성과 에너지 흡수 용량을 관찰하여 평가합니다. 콘크리트에 상당한 손상이 발생했다는 주요 지표는 콘크리트가 타격을 받은 후에 반동하지 않는 경우입니다.


 콘크리트 혼합물의 배합은 충격 강도에 영향을 미치며, 더 각지고 표면이 거친 굵은 골재는 충격 강도를 증가시킵니다. 이러한 혼합물은 더 강한 결합을 나타내며 압축 강도보다는 재료의 굽힘 강도에 더 많은 기여를 하는 것으로 여겨집니다. 콘크리트의 보관 조건에 따라 충격 강도가 달라질 수 있으며, 일반적으로 습한 조건은 건식 보관에 비해 강도를 떨어뜨립니다.


 충격 강도를 향상시키려면 최대 골재 크기가 더 작으며, 탄성 계수와 포아송 비율이 낮은 골재를 선택해야 합니다. 또한 최적의 충격 강도를 위해 시멘트 함량이 입방미터당 355.97킬로그램을 초과하지 않는 콘크리트 혼합물을 사용하는 것이 좋습니다. 이러한 조정을 통하여 콘크리트는 발생할 수 있는 동적이며 잠재적으로 손상을 줄 수 있는 힘에 대해 더 탄력적으로 만들 수 있습니다.

갑작스러운 하중이나 의도하지 않은 충격을 견디는 기계의 경우 충격이나 콘크리트 기초로 콘크리트 말뚝을 지면에 박는 것을 고려하십시오.

Education

교육

JoVE Core

Civil Engineering

토목공학

Unit 1

제1단원

Strength of Concrete

콘크리트 강도

KEY TERMS AND CONCEPTS

핵심 용어 및 개념

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 being struck. That response shows how much impact energy the material can take before it fails.

The concrete mix has a strong effect on impact strength. Coarse aggregates that are more angular and have rougher surfaces usually increase impact strength. These mixes suggest a stronger bond and are thought to contribute more to flexural strength, which is resistance to bending, than to compressive strength alone.

Storage conditions also matter. Concrete kept in wet conditions usually has lower impact strength than concrete stored dry. Impact resistance can be improved by using a smaller maximum aggregate size and aggregates with a lower modulus of elasticity and Poisson’s ratio. For the best result, the mix should also use no more than 670 pounds of cement per cubic yard.

Concrete Impact Resistance in Real Use

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

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...

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 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 concrete impact resistance is affected by mix design, aggregate shape, storage conditions, and cement content in pile driving and machinery foundations.

Concrete Impact Resistance in Real Use | 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

Concrete Impact Resistance in Real Use

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