Questions and Answers
What is cement?
Hydraulic cements can set and harden with the presence of water.
True
Non-hydraulic cements can set and harden under water.
False
What is Portland cement named after?
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Who produced Portland cement and when?
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The word 'cement' originates from the Ancient Roman term _____ caementicium.
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Which of the following is a common raw material used to manufacture Portland cement?
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Name one of the industrial by-products listed as a raw material for Portland cement.
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What are the two major classifications of aggregates by source?
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What are the three major groups of rocks that natural aggregates come from?
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Igneous rocks are formed from the solidification of molten rock.
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Metamorphic rocks are always formed from sediments.
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Which of the following is an example of a sedimentary rock?
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The process by which metamorphic rocks are formed is called ______.
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What are the two basic types of metamorphic rocks?
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What is the specific gravity range of natural aggregate?
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What are the functions of aggregates in concrete?
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Coarse aggregate is larger than ______.
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Which process is used to remove deleterious material from aggregates?
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Study Notes
Common Structural Materials in Construction
- High-rise buildings predominantly use steel and concrete.
- Commercial buildings utilize mainly concrete, sometimes steel.
- Residential structures typically involve wood along with concrete.
- Highway pavements are primarily asphalt and concrete.
- Bridges are constructed primarily with concrete, supplemented by steel.
- Airport pavements favor concrete over asphalt.
- Canal linings are primarily made of concrete, with some asphalt.
- Dams consist largely of concrete and soil.
- Tunnels are predominantly built with concrete, employing steel as well.
- Sidewalks mainly consist of concrete with some asphalt.
- Flooring options often include wood alongside concrete.
- Foundations are primarily constructed from concrete and soil.
Overview of Cement
- Cement is a binder used in construction, setting and hardening to adhere materials.
- Hydraulic cement can set and harden when mixed with water, e.g., Portland cement.
- Non-hydraulic cements, like lime, require air to harden and cannot set underwater.
Portland Cement
- Produced by pulverizing clinker, which primarily consists of hydraulic calcium silicates and calcium sulfate.
- Named after the Isle of Portland due to its resemblance to local building stone when hydrated.
- Invented in 1824 by Joseph Aspdin from a heated mixture of limestone and clay, earning a British patent.
Historical Context of Cement
- The term "cement" originates from the Ancient Roman term "opus caementicium," referring to masonry similar to modern concrete.
- Early concrete was a mixture of crushed rock and burnt lime, later enhanced with volcanic ash and pulverized brick to create hydraulic binders.
Raw Materials for Portland Cement
- Common sources include:
- Calcium: Aragonite, calcite, limestone, marl, shale.
- Iron: Ore, mill scale (industrial by-product).
- Silica: Sand, marl, shale.
- Alumina: Clay, aluminum ore.
- Sulfate: Gypsum, refuse (industrial by-product).
Properties of Portland Cement
- Size important for passing a #200 sieve, which indicates fineness for performance in mixes.
Aggregate Overview
- Aggregates are granular materials or rocks used in concrete or asphalt mixtures.
- Composed of cement paste, coarse aggregates, and fine aggregates.
Classification of Aggregate
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By Source:
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Natural:
- Result from weathering (e.g., sand, gravel) or crushing (e.g., crushed stone).
- Derived from three major rock groups: igneous, sedimentary, and metamorphic.
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Artificial:
- By-products of industrial processes (e.g., slag from blast furnaces).
- Manufactured for specialized purposes.
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Natural:
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By Mineral Composition
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By Size:
- Coarse aggregate: larger than No. 4 sieve (4.75 mm or 3/16”).
- Fine aggregate: smaller than No. 4 sieve.
Igneous Rocks
- Formed from molten rock either above or below the earth's surface.
- Extrusive: Cooled quickly on the surface, resulting in small crystals or amorphous glass; typically dark-colored and fine-grained.
- Intrusive: Formed below the surface with slow cooling, allowing large crystals to develop; e.g., granite.
Sedimentary Rocks
- Formed from the disintegration of existing rocks and deposition of sediments (e.g., sandstone, limestone, shale).
- Weathering processes lead to the breakdown and transport of rock materials.
Metamorphic Rocks
- Results from the transformation of igneous or sedimentary rocks under heat and pressure.
- Characterized as hard and dense; examples include quartz and marble.
- Two types:
- Foliated: Layered or banded due to heat and pressure.
- Non-foliated: Lack layered appearance.
Functions of Aggregate in Concrete
- Contribute to economical use of materials.
- Increase strength and durability of concrete structures.
- Help reduce shrinkage and expansion.
Characteristics of Aggregates
- Should be hard, strong, and durable.
- Must be free of organic impurities.
- Should exhibit low alkali reactivity with cement.
- Proper gradation is essential for optimal performance.
Aggregate Beneficiation Processes
- Washing: Removes fine particle coatings from aggregates.
- Heavy Media Separation: Utilizes an artificial heavy liquid for separation based on density; lighter particles float, allowing removal.
- Jigging: Applies upward pulses of air or water to separate organic impurities from aggregates.
Terminology
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Mass Measurements:
- A: mass of the oven-dry sample in air (g).
- B: mass of saturated surface-dry sample (g).
- C: apparent mass of saturated sample in water (g).
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Absorption: Increase in mass due to water absorption by aggregate's pores, expressed as a percentage of dry mass.
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Average Absorption Value: Calculated from the individual size fractions and their mass percentages.
Density of Water
- Essential for calculating absorption and density of aggregates at specific temperatures.
Additional Notes
- Understanding the properties and classification of aggregates is crucial for effective concrete mix design and application in construction.
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Description
Test your knowledge on various structural materials used in construction, such as concrete, steel, and asphalt. This quiz covers the applications of these materials in different types of structures like buildings, bridges, and highways. Challenge yourself to identify which materials are best suited for each type of structure.
