Cement & Concrete Materials Flashcards
What are some advantages of concrete as a building material? (6)
- raw materials readily available
- concrete does not rot or burn
- very strong building material
- relatively low cost
- no form of its own; almost limitless architectural potential
- can be used for a variety of purposes
What are the three main ingredients of concrete? (3)
- aggregates
- water
- portland cement
What kinds of aggregates are used in concrete, and what portion of the concrete do they make up? (3)
- fine aggregate
- coarse aggregate
- make up the majority of the mix and provide the structural mass of the concrete
What kind of water is used in concrete, and how does it help the concrete? (2)
- as a general rule, if it is okay to drink, it can be used to make concrete
- initiates the chemical process of cement hydration and causes the concrete mix to harden over time
Why is Portland cement significant, and how does it help the concrete? (2)
- most expensive part of concrete
- the “glue” that binds the aggregates
How do the ingredients of concrete come together to form a solid mass?
once hardened, aggregate particles are surrounded by the hydrated cement paste forming a solid mass having unique structural properties
What is Portland cement made of and where can raw materials be sourced? (2)
- primarily calcium carbonates and silicates and lesser amounts of compounds of aluminum, iron, and magnesium
- raw material can be extracted from many sources
How is Portland cement manufactured? (5)
- calcareous rock and argillaceous rock are crushed
- crushed raw materials are finely ground and blended together using dry or wet processes
- blended raw material is heated in a rotating kiln oven to melting point 2500-3000 degrees, allowing chemical reaction to form clinker
- clinker is cooled and mixed with gypsum
- blended material is ground to required fineness to produce Portland cement
How is a Portland cement grain structured?
composed of various types of crystalline phases surrounded by continuous calcium aluminoferrite phases
What are the five cement types according to ASTM C150?
- I: Normal
- II: Moderate Sulfate Resistance
- III: High Early Strength
- IV: Low Heat of Hydration
- V: High Sulfate Resistance
90% of U.S. manufactured cements are…
Type I, Type II, or Type I/II, meaning that the cement meets all the requirements of both types
Describe the role of water and the requirements it must meet in cement manufacturing. (6)
- essential ingredient
- combines chemically with the cement as the concrete hardens
- water must be free of contaminants; water that is potable is acceptable for use in concrete
- water-cement ratios range from .4-.55 by cement weight
- the quantity of water in the concrete mix must be controlled as closely as any other ingredient
- adding unnecessary water weakens the concrete
What is the water/cement ratio, and what does it determine? Provide an example. (3)
- the water to cement ratio largely determines the strength and durability of the concrete when it is cured properly
- the w/c ratio refers to the ratio of the weights of water and cement used in the concrete mix
- for example, a w/c ratio of .5 means that for every 100 lbs of cement used in the concrete mix, 50 lbs of water is added
What are aggregates?
a combination of crushed stone and natural sand with various properties to achieve balance between workability of fresh concrete and strength of hardened concrete
What are a couple important limits on coarse aggregate size, and what is the typical size range for them? (3)
- largest aggregate should pass easily between reinforcing bars and fit easily into the formwork
- largest aggregate size should not exceed 3/4 of the clear space between reinforcing bars, 1/3 the depth of a slab
- 3/4 to 1.5 inch is common size for most concrete
