Name: how aggregate form changes concrete
Uploaded: 2024-09-12T16:16:39.000Z
Duration: 1 min 25 s
Channel: JoVE

굵은 골재의 모양은 두 가지 특성으로 정의됩니다: 가장자리와 모서리의 날카로움 또는 각도를 나타내는 roundness와 구형도가 구형과 얼마나 닮았는지를 측정합니다.
간단한 게이지를 사용하여 거친 골재의 모양은 길이가 다른 치수보다 상당히 크면 길쭉한 모양으로, 두께가 다른 치수에 비해 작으면 벗겨지거나, 길쭉한 것과 벗겨지기 쉬운 것으로 식별할 수 있습니다.
굵은 골재의 표면 질감은 일반적으로 모 물질의 질감과 힘이 작용하는 정도에 따라 거칠거나 매끄러운 것으로 분류됩니다.
갓 부서진 암석은 날카로운 모서리와 거친 질감으로 각이 져 있습니다. 시간이 지남에 따라 풍화를 통해 모서리가 분해되어 아각도 입자를 형성합니다.
또한, 이러한 입자가 풍화제에 의해 운반됨에 따라 모서리가 마모되어 부드러운 질감의 둥근 입자가 됩니다. 
마지막으로, 굵은 응집체의 모양과 표면 질감은 조밀한 구성으로 포장하는 용이성에 영향을 미칩니다.
각지고 거친 질감의 골재는 둥글고 부드러운 질감보다 압축하기가 더 어렵습니다.

굵은 골재의 모양과 질감

골재 모양은 모서리와 모서리의 상대적인 날카로움이나 둥글기 기준으로 분류됩니다. 이 분류에는 둥근 모양, 각진 모양, 길쭉한 모양, 조각난 모양 등과 같은 범주가 포함되며, 각각 특정한 특징을 가지고 있습니다. 마모로 완전히 모양이 잡힌 둥근 골재는 강이나 해안 자갈의 전형인 반면, 분쇄석과 같이 각진 골재는 잘 정의된 모서리를 가지고 있습니다. 길쭉하고 조각난 골재는 콘크리트의 작업성과 강도를 감소시킬 수 있으므로 바람직하지 않습니다.

골재의 질감은 매끄러운 것에서 거친 것까지 다양한 표면 특성을 말합니다. 질감은 골재와 시멘트 사이의 결합에 영향을 미칩니다. 물에 의한 풍화나 세립질 암석의 파손으로 인해 발생하는 매끄러운 질감은 콘크리트 혼합 시 물의 양이 적게 필요할 수 있습니다. 반면, 파쇄석이나 석회암과 같은 거친 질감을 가진 골재는 시멘트와의 결합이 더 잘되지만 필요한 물의 양이 증가할 수 있습니다. 골재의 표면 질감에는 유리질, 과립질, 벌집질 및 결정질 형태도 포함될 수 있습니다.

골재의 포장 효율성은 모양과 질감에 의해 영향을 받습니다. 각이 지고 거친 골재는 둥글고 매끄러운 골재에 비해 포장 효율은 낮지만, 콘크리트에서 잠재적으로 기계적 결합이 더 강할 수 있습니다.

굵은 골재의 모양은 두 가지 특성으로 정의됩니다 : 가장자리와 모서리의 선명도 또는 각도를 나타내는 진원도와 ...

Education

교육

JoVE Core

Civil Engineering

토목공학

Unit 1

제1단원

Aggregates and Water

골재 및 용수

KEY TERMS AND CONCEPTS

주요 용어 및 개념

Shape and Texture of Coarse Aggregate

how aggregate form changes concrete

Aggregate form affects how concrete mixes, packs, and bonds. Coarse aggregate is classified by the sharpness or roundness of its edges and corners. The main shapes are rounded, angular, elongated, and flaky. These shapes help show how the particles will behave in concrete.

Rounded aggregates are fully shaped by attrition, which means they have been worn down by rubbing and impact. River gravel and seashore gravel are common examples. Angular aggregates, such as crushed rock, have clear edges and corners. Elongated and flaky aggregates are less desirable because they can lower the workability and strength of concrete.

Texture describes the surface of the aggregate. It can range from smooth to rough, and it affects how well the aggregate bonds with cement. Smooth textures may form from water weathering or from the breakage of fine-grained rocks. They may also need less water during mixing.

Rough textures give better bonding with cement, but they may increase water demand. Crushed basalt and limestone are examples of rough-textured aggregates. Surface textures can also be glassy, granular, honeycombed, or crystalline. Aggregate packing depends on both shape and texture. Angular and rough particles pack less efficiently, but they can create stronger mechanical interlock in concrete than rounded and smooth particles.

How Aggregate Form Changes Concrete

unsoundness of aggregate due to volume change

unsoundness-of-aggregate-due-to-volume-change

Aggregate Durability in Freeze-Thaw Cycles

Aggregate durability can decline when volume changes damage the particles. Freezing and thawing, thermal change, and wetting and drying all place stress on aggregates. When unsound aggregates break down under these conditions, they can contribute to scaling, pop-outs, and cracking in concrete. Some aggregates are more vulnerable than others. Porous flints, cherts, and aggregates that contain clay minerals are especially prone to this kind of damage. Their internal structure can make them...

deleterious substances in aggregate

Testing Aggregate Impurities in Concrete

Aggregate impurities can lower the quality and durability of concrete. Organic matter, such as loam in sand, can interfere with cement hydration and weaken the bond between the aggregate and the cement paste. Organic impurities are often checked with a colorimetric test. In this test, the darkness of the solution after agitation shows the level of organic content. Clay and fine material can also coat aggregate particles and reduce the bond with the cement paste. The amount of clay and silt in...

sieve analysis and grading curves

Aggregate Size Testing with Sieve Grading

Aggregate size testing with sieve grading measures the particle size distribution of aggregate materials. It starts with a dried sample of aggregate that is weighed first. The sample is then sorted through a stack of square-opening sieves arranged from largest opening on top to smallest opening below. The sieve stack is shaken or vibrated so the particles move through the openings by size. After a set time, the material left on each sieve is weighed. That weight is then written as a percentage...

fineness modulus

Fineness Modulus from Sieve Analysis

Fineness modulus is a numerical index used to describe how coarse or fine aggregate particles are. For sand, it is found from sieve analysis using a standard set of ASTM sieves. The result helps show whether the sample is finer or more coarse. To calculate fineness modulus, first record the weight of aggregate retained on each sieve and in the pan at the bottom. Then find the cumulative weight retained on each sieve. Next, express each cumulative weight as a percentage of the total sample...

types of aggregate grading

Aggregate Grading for Strong Concrete Mixes

Aggregate grading describes the particle size distribution in a sample of aggregate. It is important for making a concrete mix that has enough strength, reasonable workability, and minimal segregation. The right grading also helps concrete stay economical. There are four main types of aggregate gradation: well-graded, uniformly graded, gap-graded, and open-graded. Each type has a different pattern on a gradation curve, which shows how particle sizes are spread across sieve sizes. These...

maximum size of aggregate

How Aggregate Size Affects Concrete Mix

Aggregate size affects how concrete is mixed, placed, and strengthened. The maximum size of aggregate is defined by the sieve aperture that retains 15 percent or more of the particles in the sample. This size choice helps determine the concrete’s water demand, workability, and final strength. Larger aggregate particles reduce the surface area that must be covered by cement paste. As a result, they can lower the water needed in the mix. When the desired workability and richness are kept, this...

quality of water

Water Standards for Concrete Mixing

Water standards for concrete mixing help control strength and durability. Potable water is usually preferred. Even so, it should not contain too much sodium or potassium, because these salts can weaken concrete integrity. Water quality is judged by impurities such as dissolved solids, chlorides, and sulfates. The pH value is ideally between 6 and 8. Slightly acidic natural water may still be acceptable if it does not contain harmful organic matter or algae. Limits for these impurities depend...

testing water quality

Water Tests for Concrete Performance

Water tests for concrete performance help determine whether an uncertain water source is safe to use in cement and mortar. The main checks compare the water against de-ionized or distilled water benchmarks. Engineers look at both setting time and the compressive strength of mortar made with the test water. Standards set clear limits for these results. ASTM C1602 requires setting times to stay within 90 minutes of the control. BS 3146:1980 allows a 30-minute change in initial setting, while BS...

aggregates classification

Aggregate Types by Size, Weight, and Source

Aggregate types are grouped by size, petrographic characteristics, weight, and source. These categories help describe how different aggregates are identified and used in concrete. Size is one of the most common ways to classify them. Based on particle size, aggregates are either coarse or fine. Coarse aggregates are particles that do not pass through ASTM sieve No. 4. Fine aggregates are the particles that do pass through that sieve. Petrographic classification looks at shared mineral features.

shape and texture of coarse aggregate

Aggregate form affects how concrete mixes, packs, and bonds. Coarse aggregate is classified by the sharpness or roundness of its edges and corners. The main shapes are rounded, angular, elongated, and flaky. These shapes help show how the particles will behave in concrete. Rounded aggregates are fully shaped by attrition, which means they have been worn down by rubbing and impact. River gravel and seashore gravel are common examples. Angular aggregates, such as crushed rock, have clear edges...

bonding and strength of aggregate

How Aggregate Shape Affects Concrete Bond

Aggregate shape and surface texture affect how well concrete holds together. Rough, angular aggregates usually bond more strongly with the cement matrix than smooth, rounded ones. This stronger adhesion can help produce high-strength concrete. Angular aggregates also have a larger surface area. That gives the cement paste more area to grip, which improves the bond. Bond quality is hard to measure directly, and there is no single test that is accepted everywhere. A broken concrete sample can...

toughness and hardness of aggregate

Testing Aggregate Impact and Abrasion

Aggregate toughness and hardness are important for concrete used on pavement surfaces and industrial floors that must carry heavy loads. Toughness means an aggregate can resist failure from impact. Hardness means it can resist wear.

specific gravity of aggregate

Aggregate Pore Effects on Specific Gravity

Aggregate specific gravity depends on the pores inside the material. These pores may be permeable or impermeable, so the same aggregate can be described in more than one way. For this reason, specific gravity is grouped into bulk or gross specific gravity, apparent specific gravity, and absolute specific gravity. Bulk or gross specific gravity uses the mass of aggregate in the saturated surface-dry state. It is compared with the total volume of the aggregate, including both the solids and the...

bulk density of aggregate

How Aggregate Size Affects Bulk Density

Bulk density describes the mass of aggregate that fills a unit volume, including the empty spaces between particles. Those void spaces remain because aggregate particles cannot be packed so tightly that every gap disappears. In practice, bulk refers to the total volume of both the particles and the spaces around them. This measurement matters when aggregates are batched by volume. It also helps convert materials measured by mass into a volume-based quantity. Natural mineral aggregates such as...

porosity and absorption of aggregate

Aggregate Pore States and Water Uptake

Aggregate contains pores of different sizes, and those pores may be sealed inside the particle or open to the surface. Open pores let water enter the aggregate. Because aggregate makes up about three-quarters of concrete by volume, its porosity strongly affects the porosity of the finished concrete. Aggregate can also be described by its moisture state. When water fills every pore, the material is saturated and surface-dry. If it sits in dry air, some water evaporates and the aggregate becomes...

moisture content and bulking of aggregate

moisture-content-and-bulking-of-aggregate

How Aggregate Moisture Affects Concrete Mixes

Aggregate moisture affects concrete mixing by changing how much water must be added to the batch. Moisture content is the water coating the outside of aggregate that is in a saturated and surface-dry state. The total water in moist aggregate includes both moisture content and water absorption. When aggregates sit in stockpiles or are exposed to rain, they can take in moisture. That extra water must be counted during concrete batching so the water-to-cement ratio stays correct. The moisture...

key terms and concepts

Learn how rounded, angular, flaky, and rough or smooth aggregates affect concrete workability, bonding, packing, and strength in civil engineering.

How Aggregate Form Changes Concrete | 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 Aggregate Form Changes Concrete

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