Name: concrete damage from sulfate exposure
Uploaded: 2024-11-07T14:48:45.000Z
Duration: 1 min 29 s
Channel: JoVE

황산염 공격을받은 콘크리트는 일반적으로 뚜렷한 희끄무레한 외관을 나타내며, 종종 가장자리와 모서리에서 먼저 눈에 띄고 나중에는 균열 및 박리가 발생합니다.
콘크리트의 균열은 향상된 투과성으로 인해 황산염이 함유된 물이 구조물에 침투할 수 있습니다.
침투된 황산염은 황산칼슘과 설포알루미네이트를 형성하며, 이는 더 많은 공간을 차지하여 경화된 콘크리트가 팽창하고 부서지게 하여 팽창하는 슬래브에 의해 가해지는 측면 압력으로 인한 건물 벽의 이동과 같은 문제를 일으킵니다.
토양 또는 지하수는 나트륨, 칼륨, 마그네슘, 암모늄 및 황산칼슘과 같은 황산염의 일반적인 공급원으로, 콘크리트와 접촉할 때 손상을 입힙니다.
황산염 공격에 대한 콘크리트의 내성에 대한 실험실 테스트에는 나트륨 또는 황산마그네슘 용액 또는 이 둘의 조합에 샘플을 담그거나 대체하여 습윤 및 건조하는 작업이 포함됩니다.
충격은 시편의 강도 손실, 팽창, 체중 감소 또는 육안 검사로 측정됩니다.
황산염 내성 시멘트를 사용하거나 수화 시멘트 페이스트에서 수산화칼슘을 줄이고 물-시멘트 비율이 낮은 고밀도 콘크리트를 타설하면 황산염 공격에 대한 콘크리트의 방어력이 향상됩니다.

콘크리트에 대한 황산염 공격

Sulfate Attack on Concrete

콘크리트에 대한 황산염 공격은 모서리와 가장자리에서 시작하여 균열과 박리를 동반하는 희끄무레한 변색이 특징인 열화 과정입니다. 이 현상은 황산염이 경화된 콘크리트의 구성 요소와 반응하여 대체 물질보다 더 많은 공간을 차지하는 황산칼슘 및 설포알루미네이트와 같은 화합물을 형성하여 콘크리트가 팽창하고 파괴될 때 발생합니다.


 토양, 지하수 또는 산업 유출물과 같은 출처의 황산염은 콘크리트에 침투하고, 그 반응으로 석고와 에트링가이트가 생성됩니다. 이 반응은 석고가 트리칼슘 알루미네이트와 반응하여 플래시 세팅을 방지하는 시멘트 제조와 유사합니다. 그러나 경화된 콘크리트에서는 이 반응이 구조적 손상으로 이어질 수 있으므로 바람직하지 않습니다.


 황산염 공격에 대한 저항성은 일반적으로 콘크리트 샘플을 황산염 용액에 담가서 테스트하는 중요한 측면입니다. 이 방법을 사용하면 강도 감소, 팽창 및 중량 감소와 같은 시편의 변화를 관찰할 수 있습니다. 시각적 검사도 손상을 식별하는 데 귀중한 도구입니다. 황산염 저항 시멘트 및 블렌드 시멘트와 같이 낮은 삼칼슘 알루미네이트 함량의 시멘트를 사용하면 콘크리트의 황산염 공격에 대한 저항성을 크게 향상시킬 수 있습니다. 황산염 공격에 대한 콘크리트의 내구성은 또한 낮은 투과성을 위한 낮은 물-시멘트 비율을 달성하는 데 달려 있으며, 이는 손상 가능성을 줄이는 데 중요한 요소입니다.

황산염 공격을받는 콘크리트는 일반적으로 뚜렷한 희끄무레한 모양을 나타내며, 종종 가장자리와 모서리에서 먼저 눈에 띄며 나중에는 ...

Education

교육

JoVE Core

Civil Engineering

토목공학

Unit 1

제1단원

Permeability of Concrete

콘크리트의 투수성

KEY TERMS AND CONCEPTS

주요 용어 및 개념

concrete damage from sulfate exposure

Concrete damage from sulfate exposure starts with a whitish discoloration, often first seen at the edges and corners. As the attack continues, the concrete can crack and spall. This deterioration happens when sulfates react with hardened concrete and create new compounds that take up more space than the materials they replace.

Sulfates may enter concrete from soil, groundwater, or industrial effluents. Inside the concrete, they can form calcium sulfate and calcium sulfoaluminate. The reaction also produces gypsum and ettringite, which expand and disrupt the hardened structure.

This process is related to the role of gypsum during cement manufacture. There, gypsum reacts with tricalcium aluminate to help prevent flash set. In hardened concrete, the same kind of reaction becomes harmful and can weaken the structure.

Engineers test sulfate resistance by immersing concrete samples in sulfate solutions. They then look for strength reduction, expansion, and weight loss. Visual inspection is also important because surface changes can help reveal damage.

Concrete can resist sulfate attack better when it uses cement with low tricalcium aluminate content. Sulfate-resisting cement and blended cement are both useful options. A low water-cement ratio also helps by lowering permeability, which reduces the chance of sulfate damage.

Concrete Damage from Sulfate Exposure

permeability of concrete

Concrete Durability and Water Penetration

Concrete durability depends partly on how easily water and gases can move through it. This property, called permeability, is important for judging water-tightness and resistance to chemical attack in concrete structures. Permeability is measured with comparative lab tests. In a typical test, the sides of a concrete specimen are sealed, water pressure is applied to the top surface, and the amount of water that passes through is measured. The test is often run for about ten days until a steady...

sulfate attack on concrete

Concrete damage from sulfate exposure starts with a whitish discoloration, often first seen at the edges and corners. As the attack continues, the concrete can crack and spall. This deterioration happens when sulfates react with hardened concrete and create new compounds that take up more space than the materials they replace. Sulfates may enter concrete from soil, groundwater, or industrial effluents. Inside the concrete, they can form calcium sulfate and calcium sulfoaluminate. The reaction...

effect of sea water on concrete

Seawater Damage and Concrete Durability

Seawater can damage concrete by changing its chemistry, increasing porosity, and lowering strength. In marine settings, concrete is exposed to dissolved salts and repeated wetting, so its durability depends on how much water can enter the material. One major form of damage is the breakdown of ettringite and gypsum, two concrete minerals that can dissolve in seawater. As these materials are lost, the concrete becomes more porous. Salt can also crystallize inside pores, especially above the...

acid attack on concrete

Concrete Damage from Low pH Water

Concrete damage from low pH water happens when acids react with the hydrated cement paste. This reaction dissolves the paste, so the concrete becomes softer and weaker. The problem is often seen in chimneys, sewers, and industrial settings. The amount of damage depends on how acidic the water is. When pH falls below 6.5, the attack becomes more severe. A pH below 4.5 can cause major concrete damage. The rate of damage also depends on how fast hydrogen ions move through the cement gel. This...

alkali aggregate reaction in concrete

How Moisture Cracks Alkali-Reactive Concrete

Alkali-aggregate reaction in concrete can weaken a structure when siliceous minerals in the aggregate react with alkaline hydroxides from cement. The reaction makes an alkali-silica gel, which pulls in water and swells. As the gel expands inside the rigid cement paste, it creates pressure that can crack and disrupt the concrete. The damage comes from both osmotic hydraulic pressure and the swelling of the solid reaction products. Particle size also matters. Fine siliceous particles can cause...

corrosion of reinforcement

Why Concrete Can Fail Around Rebar

Steel reinforcement in concrete can corrode when its protective environment changes. Fresh concrete is highly alkaline because of calcium hydroxide, with a pH of about 13. That high pH helps form a passive iron oxide layer on the steel surface, which slows corrosion. Over time, carbonation, chloride ingress, and cracking can weaken this protection. Concrete contains hydrated cement paste with salts, and it acts as an electrolyte. Different areas of the steel then behave as anodic and cathodic...

key terms and concepts

Learn how sulfate exposure damages concrete, causes whitening, cracking, and spalling, and how resistance is tested and improved with low-permeability cement.

Concrete Damage from Sulfate Exposure | 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 Damage from Sulfate Exposure

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