Name: how portland cement is made
Uploaded: 2024-09-12T16:16:35.000Z
Duration: 1 min 21 s
Channel: JoVE

מלט פורטלנד, המרכיב המקשר בבטון, מופק מחומרים גירניים, עשירים בחומרי סיד וארגילקון, המכילים סיליקה, אלומינה ותחמוצת ברזל.
חומרי הגלם נמחצים במגרסות ומאוחסנים בממגורות. לאחר מכן הם עוברים פרופורציה ומתקדמים לטחינה ונטחנים לאבקה.
בתהליך הערבוב היבש, האבקה מעורבבת יבש, מעורבבת ומאוחסנת בממגורות. לחלופין, בערבוב רטוב, האבקה מעורבבת עם מים ליצירת תרחיץ, מעורבבת ומאוחסנת באגנים.
לאחר מכן התערובת מועברת לכבשן סיבובי, ומחוממת לייצור קלינקר, אשר לאחר מכן מקורר ומאוחסן.
מאוחר יותר, כמות קטנה של גבס מתווספת לקלינקר ומועברת לטחינה כדי להיכתש לאבקת מלט פורטלנד דקה.
מלט פורטלנד מורכב בעיקר מארבע תרכובות עיקריות: טריקלציום סיליקט, דיקלציום סיליקט, טריקלציום אלומינייט וטטרקלציום אלומינופריט.
בהתבסס על השונות במרכיבים אלה, מלט פורטלנד מסווג לסוגים שונים, כאשר מלט פורטלנד רגיל, הידוע גם בשם סוג I, הוא הנפוץ ביותר.

לא הוכרז על ניגוד עניינים.

צמנט פורטלנד

Portland Cement

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צמנט פורטלנד הוא מרכיב הכרחי בבטון, המשמש כחומר מקשר המיוצר מחומרים טחונים דק, הכוללים סיד, ברזל, סיליקה ואלומינה. סיד מופק בעיקר מאבן גיר, שיש, חוואר, צדפים וחרסית, המספקות גם ברזל ואלומינה, בעוד שסיליקה מקורה בחול, גיר ובוקסיט. ייצור מודרני של צמנט פורטלנד הוא מקור משמעותי לפליטת פחמן דו חמצני, ולכן מתבצע מחקר לצמצום תכולת הפחמן בבטון באמצעות חומרים משלימים כמו תוצרי לוואי תעשייתיים, כגון סיגי כבשן ברזל, אפר פחם ועשן סיליקה.

תהליך הייצור כולל ריסוק מרכיבים אלה, ואחריו שימוש בשיטה רטובה או יבשה להכנת המלט. בתהליך היבש, חומרי גלם נטחנים לאבקה, מערבבים ומחממים בכבשן, בעוד שהתהליך הרטוב כולל ערבוב של חומרים טחונים עם מים ליצירת עיסה לפני החימום. הכבשן הפועל בטמפרטורות גבוהות של בין 1426.67°C עד 1648.89°C מעלות צלזיוס, הופך את החומר לקלינקר, אשר לאחר מכן מתקרר ונטחן עם כמות קטנה של גבס ליצירת אבקה דקה. הגבס המוסף מסייע לשלוט בזמן ההתקשות של המלט.

צמנט פורטלנד מועבר בעיקר בכמויות גדולות באמצעות רכבת או משאיות גדולות ונמכר בטונות. כמויות קטנות יותר נארזות בשקים, שבדרך כלל שוקלים 42.64 קילוגרם ומכילים כ-0.03 מטרים מעוקבים של מלט.

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מלט פורטלנד, המרכיב המחייב בבטון, מיוצר מחומרים גירניים, עשירים בחומרי סיד וארגילקון, המכילים סיליקה, ...

Education

JoVE Core

Civil Engineering

הנדסה אזרחית

Unit 1

יחידה 1

Introduction to Concrete

מבוא לבטון

KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

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 crushing the ingredients and then preparing them by either a wet or dry method. In the dry process, the materials are ground into powder, mixed, and heated in a kiln. In the wet process, the ground materials are mixed with water first to form a slurry, which is then heated.

The kiln reaches very high temperatures, between 2600 and 3000 degrees Fahrenheit. At that heat, the material changes into clinker. The clinker is cooled and ground again with a small amount of gypsum to make a fine powder. Gypsum helps control how fast the cement sets.

Portland cement production also has an environmental cost because it is a major source of carbon dioxide emissions. For that reason, researchers look for ways to reduce the amount used in concrete by adding supplementary materials. Examples include industrial by-products such as iron furnace slag, fly ash, and silica fume. Portland cement is usually shipped in bulk by rail or large trailers and sold by the ton. Smaller amounts are sold in bags that usually weigh 94 pounds and contain one cubic foot of cement.

How Portland Cement Is Made

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

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 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...

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

Learn how Portland cement is produced from limestone, silica, and other raw materials, then heated, ground with gypsum, and shipped in bulk or bags.

How Portland Cement Is Made | 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

How Portland Cement Is Made

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