Questions and Answers
What is the primary difference between non-hydraulic cements and hydraulic cements?
Non-hydraulic cements set and harden in air only, while hydraulic cements can set and harden both in air and under water.
What is the purpose of adding gypsum to Portland cement?
To prevent the setting of the cement
What is the maximum allowable SO3 content in ordinary Portland cement according to ASTM C150?
3%
What type of compound is calcium hydroxide?
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Why does the presence of a high content of MgO and free lime in cement lead to expansion upon slaking?
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Why is portland cement grayish in color?
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What problem can arise when cement with high alkalies content is used with reactive aggregates in concrete production?
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How is portland cement different from hydraulic lime?
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Which material is NOT considered a cementitious material?
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Why does expansion in hardened concrete lead to cracking?
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What is the total alkali content limit (%Na2O+0.658%K2O=equivalent Na2O) when using cement with reactive aggregates?
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What is the primary role of gypsum in Portland cement production?
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What is the main chemical reaction responsible for the hardening of Portland Cement paste?
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In the manufacturing process of Portland Cement clinker, what are the two main raw materials used?
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What is added to raw materials before they are turned into cement to facilitate the process?
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Which material is combined with cement paste to produce mortar?
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For asphalt construction, what should be done if using clinker as a material?
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'Kaolin' is composed of which chemical elements?
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What is the purpose of adding gypsum to clinker in the manufacturing of cement?
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Which stage involves grinding the burned product, known as 'clinker,' together with some gypsum?
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In which manufacturing process are the raw materials ground wet and fed to the kiln as a slurry?
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At what temperature does the clinker leave the kiln before entering a cooling zone?
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Which step of the cement manufacturing process involves raw meal drying, grinding, and homogenization?
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What is the key difference between the dry and semidry processes in cement manufacturing?
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Which compound is formed during the hydration of Portland cement and releases the most heat?
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Which of the following is NOT classified as one of the five main types of cements covered by TS EN 197-1?
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What are the two most important hydraulic constituents in Portland cement?
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Which compound is NOT considered one of the major compounds in Portland cement clinker?
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What does CEM IV stand for in the classification of cements under TS EN 197-1?
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What is the main difference between CEM II/A-L and CEM II/B-L cements?
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Study Notes
Cement Materials of Construction
- Binders: materials with adhesive properties, including glues (animal or vegetable sources, synthetic polymers), bituminous materials (complex hydrocarbons), and calcium compounds (gypsum, lime, portland cement).
Calcium-Based Binders (Cements)
- Will harden and develop binding properties when mixed with water.
- Include gypsum, lime, and portland cement.
Cementitious Materials
- Gain binding properties upon hydration or reaction with Ca(OH)2 (calcium hydroxide).
- Include non-hydraulic cements (lime, gypsum) and hydraulic cements (hydraulic lime, portland cement).
Portland Cement
- A hydraulic binder produced by intergrinding a small amount of gypsum and portland cement clinker.
- Name derived from its resemblance to Portland stone.
- Normally grayish in color due to iron oxide presence.
- When mixed with water, forms a plastic paste that can be molded into any shape, gaining rigidity and hardening over time.
Properties of Portland Cement
- Contains 30% clay and 70% limestone in cooked form.
- Mixed with gypsum at a rate of 2-6% by weight and thoroughly grinded.
- Used in making mortars and concretes.
Manufacture of Portland Cement
- Main raw materials: limestone (CaCO3) and clay.
- Clays have various amounts of SiO2 (silicon dioxide) and AI2O3 (aluminium oxide); kaolin, pure clay is composed of AI2O3.2SiO2.2H2O.
- Four stages in the manufacture of portland cement: crushing and grinding raw materials, blending, burning the prepared mix in a kiln, and grinding the burned product (clinker) together with gypsum.
Hydration of Portland Cement
- Hydration reactions between cement compounds and water, resulting in the formation of complex compounds.
- Calcium silicates (C2S and C3S) are the most important hydraulic constituents.
Types of Cements Produced in Turkey
- TS EN 197-1 covers 27 standard cements classified into five main types: CEM I (Portland cement), CEM II (Portland composite cement), CEM III (Blast furnace slag cement), CEM IV (Pozzolanic cement), and CEM V (Composite cement).
Chemical Composition of Portland Cement
- Oxide composition: includes C3S, C2S, C3A, and C4AF.
- Gypsum retards quick setting, but excessive gypsum can lead to disruptive expansion.
- ASTM C150 and TS EN 197-1 regulate SO3 content in ordinary portland cement.
- High MgO and free lime content can cause expansion upon slaking.
- Alkalies can react with reactive silica in aggregates, forming alkali-silica gel and causing expansion and cracking.
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