Name: testing aggregate impurities in concrete
Uploaded: 2024-11-07T14:48:25.000Z
Duration: 1 min 25 s
Channel: JoVE

천연 모래에는 시멘트의 수화를 방해하는 부패한 식물 물질과 같은 유기 불순물이 포함될 수 있습니다.
유기물의 존재를 감지하기 위해 비색 테스트가 수행되며, 이는 골재를 포함하는 용액의 색상으로 판단할 수 있습니다. 용액이 어두울수록 용액의 유기물이 높아집니다.
돌을 파쇄하여 얻은 점토, 미사 및 분쇄기 먼지와 같은 미세한 불순물은 골재를 코팅하고 시멘트 페이스트와의 접착 불량을 초래합니다.
또한 미세한 불순물이 있으면 젖을 표면적이 증가하여 혼합, 배치 및 마무리에 더 많은 물이 필요합니다. 이 과도한 물은 건조 수축 및 균열 가능성을 증가시킵니다.
습식 체 방법은 굵은 응집체에서 미세한 불순물의 존재를 측정하는 데 사용됩니다. 
미세한 골재에 과도한 염분이 있으면 강철 보강재가 부식되고 공기로부터 수분을 흡수하여 콘크리트에 백화가 발생합니다.
셰일과 같은 저밀도 물질의 존재와 점토 덩어리, 석탄 또는 목재와 같은 골재의 부드러운 개재물은 하중에 의해 분해되어 콘크리트에 구멍과 팝아웃을 유발할 수 있습니다.

집합체 내의 유해 물질

골재의 유해 물질은 콘크리트의 품질과 내구성에 해로울 수 있습니다. 이러한 물질에는 시멘트 수화를 방해하고 일반적으로 모래에 존재하는 양토와 같은 유기 불순물이 포함됩니다. 이는 골재와 시멘트 페이스트 사이의 양호한 결합을 방해합니다. 유기 불순물은 비색 검사를 사용하여 감지할 수 있으며, 교반 후 용액의 어두움은 유기 함량 수준을 나타냅니다.


 또 다른 유형의 불순물은 골재 입자를 코팅하고 시멘트 페이스트와의 결합을 약화시킬 수 있는 점토와 미세 물질입니다. 골재의 점토와 실트 함량은 종종 침전법 또는 습식 체질법을 사용하여 평가합니다. 해양 환경의 염분도 유해 물질로 간주되며, 특히 질량 기준 6% 이상인 경우 콘크리트에 매립된 보강재의 부식으로 이어집니다. 소금 함량을 줄이기 위해 골재를 깨끗한 물로 씻는 것이 좋습니다.


 마지막으로, 셰일, 석탄 또는 운모와 같이 내구성이 없거나 물을 흡수하는 입자가 포함된 골재는 콘크리트 분해로 이어질 수 있습니다. 미국 재료 시험 협회(ASTM) C 33-03은 골재에서 이러한 건전하지 않은 입자에 대한 허용 수준을 설정합니다. 적절한 테스트와 표준 준수는 건설에 사용되는 골재의 품질을 보장하고 콘크리트 구조물의 무결성과 수명을 보호하는 데 매우 중요합니다.

천연 모래에는 시멘트의 수화를 방해하는 부패한 식물 물질과 같은 유기 불순물이 포함될 수 있습니다.
비색 테스트는 ...

Education

교육

JoVE Core

Civil Engineering

토목공학

Unit 1

제1단원

Aggregates and Water

골재 및 용수

KEY TERMS AND CONCEPTS

주요 용어 및 개념

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 aggregate is commonly measured by sedimentation or wet-sieve methods. Salts from marine environments are another concern, especially when they exceed 6% by mass. These salts can cause corrosion in steel reinforcement inside concrete, so washing aggregates with fresh water is recommended to lower the salt content.

Some aggregates contain unsound particles such as shale, coal, or mica. These materials may be non-durable or absorb water and can lead to concrete damage over time. ASTM C 33-03 sets limits for these particles, so testing and following standards help protect the strength and service life of concrete structures.

Testing Aggregate Impurities in 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

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

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...

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 organic matter, clay, salts, and unsound particles in aggregate are tested, and why they matter for concrete strength and durability.

Testing Aggregate Impurities in 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

Testing Aggregate Impurities in Concrete

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