Mix Design of Concrete and Asphalt
Concrete and Asphalt
Learning Objectives:
- Understand the basic composition of concrete, including cement, aggregates, water, and admixtures.
- Learn the fundamental properties of concrete, such as compressive strength, tensile strength, workability, and durability.
- Comprehend the role of reinforcement, such as steel bars or mesh, in enhancing the tensile strength and ductility of concrete.
Concrete:
Concrete is a composite material composed of cement, aggregates (sand and gravel), water, and often admixtures. Cement acts as the binder that holds the mixture together, while aggregates provide strength and durability.
Properties of Concrete:- Compressive Strength: The ability of concrete to withstand axial loads (compression) without failing.
- Tensile Strength: Concrete is weak in tension, and reinforcing steel (rebar) is often added to improve tensile strength.
- Workability: The ease with which concrete can be mixed, placed, and finished.
- Durability: The resistance of concrete to environmental factors like moisture, freeze-thaw cycles, and chemical attack.
Asphalt:
Asphalt consists of bitumen (a sticky, black, and highly viscous liquid or semi-solid form of petroleum) and aggregates. Aggregates provide strength and stability to the asphalt mixture, while bitumen acts as the binding and waterproofing agent.
Properties of Asphalt:- Flexibility: Asphalt is a flexible pavement material, capable of withstanding heavy loads and thermal expansion.
- Adhesion: Bitumen has good adhesion properties, allowing it to bond well with aggregates.
- Temperature Sensitivity: The properties of asphalt can be significantly affected by temperature, with viscosity changing as temperature changes.
Asphalt- Concrete Joint, Estabiano, CC BY-SA 4.0, via Wikimedia Commons
Solved Example: 9128-01
If fineness modulus of sand is 2.5, it is graded as:
A. Very fine sand
B. Fine sand
C. Medium sand
D. Coarse sand
Correct Answer: B
Solved Example: 9128-02
Bulking of sand occurs in the moisture content of:
A. 3%
B. 5%
C. 10%
D. 12%
Correct Answer: B
Solved Example: 9128-03
The aggregate impact value of the aggregate used in:
A. Building concrete is less than 45
B. Road pavement concrete is less than 30
C. Runway concrete is less than 30
D. All the options are correct
Correct Answer: D
Solved Example: 9128-04
Which of following is not a function of sand in mortar?
A. Providing strength
B. Reducing the consumption of cement
C. Reducing shrinkage
D. Reducing the setting time
Correct Answer: A
Solved Example: 9128-05
Which of the following aggregates gives maximum strength in concrete?
A. Rounded aggregate
B. Elongated aggregate
C. Flaky aggregate
D. Cubical aggregate
Correct Answer: D
Solved Example: 9128-06
Give an example for flaky shape of aggregate.
A. Pit sand
B. Crushed rock
C. Blown sand
D. Laminated rock
Correct Answer: D