Name: special portland cements for durability
Uploaded: 2024-09-12T16:16:36.000Z
Duration: 1 min 22 s
Channel: JoVE

טחינה משולבת של קלינקר מלט פורטלנד עם סיגים מגורענים של תנור פיצוץ, תוצר לוואי של תהליך ייצור הברזל, מייצרת מלט סיגים.
זה יכול לשמש לבניית מבנים גדולים שנועדו להתנגד להתקפה של כלורידים וסולפטים.
מלט לבן, העשוי מגיר וחמר חרסינה המכיל פחות כמויות של ברזל ותחמוצות מנגן, הוא בעל צבע לבן ייחודי וניתן להשתמש בו ליצירת חזיתות עם אסתטיקה מעולה.
הוספת פיגמנטים צבעוניים שאינם מזיקים לבטון עם מלט לבן מייצרת מלט צבעוני.
צמנטים נרחבים, כגון סוגים K, M ו- S, מיוצרים על ידי שילוב של מלט פורטלנד עם חומר מרחיב ומייצב. זה מונע סדיקה של התכווצות באמצעות התרחבות מבוקרת עקב היווצרות אטרינגיט מוקדמת במהלך ההתקשות.
מלט פורטלנד מאומן באוויר משתמש בכמויות קטנות יותר של חומרים דוחפי אוויר כדי ליצור מיליוני בועות אוויר מיקרוסקופיות בתוך מטריצת המלט.
זה מספק חללים למים להתרחב כאשר הם קופאים, ומונע סדקים הנגרמים על ידי מחזורי הקפאה-הפשרה. 
מלט פורטלנד עמיד למים משלב חומרים דוחי מים, ומבטיח שמבנים החשופים ללחות מוגנים מפני חדירת מים.

לא הוכרז על ניגוד עניינים.

סוגי צמנט ii

Types of Cement II

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צמנט פורטלנד בתוספת סיגי כבשן מיוצר על ידי ערבוב קלינקר צמנט פורטלנד עעם סיגי כבשן מותכות, שמהוות 25% עד 65% ממשקל הצמנט. למרות הדמיון לצמנט פורטלנד רגיל (סוג I) מבחינת עדינות וזמני התקשות, חוזקו המוקדם נמוך יותר, אך הוא משיג חוזק דומה בהמשך. הוא מתאים במיוחד למבני בטון מסיביים ולסביבות ימיות בשל חום ההידרציה הנמוך שלו והתנגדותו המעולה לסולפטים.

צמנט פורטלנד לבן וצבעוני משמשים בעיקר כאשר השיקולים האסתטיים הם בעלי חשיבות עליונה, כגון לוחות קיר מסך טרומיים, לוחות חזיתיים, רצפות טרצו, טיח, שכבות גימור וטיח לריצוף. צמנטים אלו יקרים יותר בשל דרישות ייצור מחמירות למניעת זיהומים והשגת אחידות צבע.

צמנט מתפשט מתרחב במהלך תקופת ההתקשות המוקדמת כדי לפצות על התכווצות הייבוש. ישנם שלושה סוגים זמינים: K, M ו-S, הנבדלים בעיקר בהרכבם הכימי. סוג K מיועד לשליטה כללית בהתכווצות, סוג M מיועד לעמידות בפני סולפטים, וסוג S מיועד לחשיפה גבוהה לסולפטים. כל סוג נועד למזער סדקים על ידי פיצוי על השפעות ההתכווצות. סוג זה מתאים למצבים בהם יש צורך במינימום שינוי בנפח כדי למנוע סדקים.

צמנט פורטלנד עמיד למים כולל תוספים כמו סטיארט סידן או סטיארט אלומיניום, המעורבבים לתוך קלינקר צמנט פורטלנד במהלך הטחינה, מה שמשפר את עמידות הצמנט בפני חדירת לחות.

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סוגי צמנט II

טחינה משולבת של קלינקר מלט פורטלנד עם סיגים מגורענים של תנור פיצוץ, תוצר לוואי של תהליך ייצור הברזל, מייצרת מלט סיגים.
ניתן להשתמש בו כדי ...

Education

JoVE Core

Civil Engineering

הנדסה אזרחית

Unit 1

יחידה 1

Introduction to Concrete

מבוא לבטון

KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

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 reaches similar strength later on. It is useful for mass concrete structures and marine environments because it gives off less heat during hydration and resists sulfate better.

White and colored Portland cements are used when appearance matters most. They are common in precast curtain-wall panels, facing panels, terrazzo floors, stucco, finish-coat plaster, and tile grout. These cements cost more because they must be made with careful control to avoid impurities and keep the color uniform.

Expansive cement is made to expand during early hardening so it can offset drying shrinkage. This helps reduce cracking when minimal volume change is important. Three types are available: K, M, and S. Type K is used for general shrinkage control, Type M is made for sulfate resistance, and Type S is for high sulfate exposure.

Waterproof Portland cement is another special type. It includes additives such as calcium stearate or aluminum stearate mixed into the Portland cement clinker during grinding. These additives improve the cement’s resistance to moisture penetration.

Special Portland Cements for Durability

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 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...

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 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

Explore Portland blast-furnace, white and colored, expansive, and waterproof cements, and see how each type supports strength, appearance, and moisture resistance.

Special Portland Cements for Durability | JoVE K12

JoVE Core Civil Engineering provides a foundational exploration of essential construction materials in civil engineering, focusing on bricks, stones, steel, wood, and concrete through easy-to-understand animated videos. This collection covers the properties, manufacturing processes, and practical applications of these materials. Additionally, the accompanied science-in-action videos demonstrate the research experiments performed in laboratories.

civil engineering

Special Portland Cements for Durability

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