Cement types — identification of white cement Portland cement manufactured from pure white chalk and clay and essentially free from iron oxide pigments is commonly called:
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AQuick-setting cement
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BRapid-hardening cement
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CWhite cement
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DLow-heat Portland cement
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EPortland pozzolana cement
Answer
Correct Answer: White cement
Explanation
Introduction / Context:Different cements are formulated to achieve specific color or performance objectives. When architectural aesthetics call for light or colored finishes, a special low-iron formulation is used to produce a white product.
Given Data / Assumptions:
- Raw materials: very low iron and manganese content to avoid gray coloration.
- Manufacturing controls to prevent contamination from kiln and grinding media.
- Application focus: decorative concrete, terrazzo, tiles, and colored mortars.
Concept / Approach:The absence of coloring oxides (primarily Fe2O3) yields a white clinker which, when ground with gypsum, becomes white cement. Performance is comparable to ordinary Portland cement, but color control is paramount; white pigments can be added without muddying.
Step-by-Step Solution:
Select high-purity limestone (chalk) and kaolin with minimal iron.Use kiln refractories and grinding media that do not introduce dark contaminants.Grind clinker with gypsum and test for whiteness index and strength.Verification / Alternative check:Colorimetric tests (whiteness index) and chemical analysis confirm low iron content; compressive strength tests verify structural suitability.
Why Other Options Are Wrong:
- Quick-setting and rapid-hardening cements (A/B): defined by setting/strength characteristics, not color.
- Low-heat cement (D): formulated for mass concrete to limit temperature rise; again not color-driven.
- PPC (E): blended with pozzolana, typically gray.
Common Pitfalls:Assuming white cement is always weaker or only decorative; it can meet structural grades but is more expensive due to stringent raw materials and processing.
Final Answer:
White cement