Q.
a. What is meant by aggregates? Describe how the type, quality and grading of aggregates can affect the strength of concrete. (10 marks)
b. Explain how the method of batching, placing, compacting and curing influenced the strength of concrete. (15 marks)
(25 marks, 2018 Q6)
A.
a) Similar question was asked in
Construction aggregate, or simply "aggregate", is a broad category of coarse to medium grained particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates. Aggregates are the most mined materials in the world. Aggregates are a component of composite materials such as concrete and asphalt concrete; the aggregate serves as reinforcement to add strength to the overall composite material.
Wikipedia "aggregates"
Type, proportions, grading and quality of aggregates
Functions of Coarse aggregate:
· Coarse aggregate makes solid and hard mass of concrete with cement and sand.
· It increases the crushing strength of concrete.
· It reduces the cost of concrete, since it occupies major volume.
Requirements: Coarse aggregate used may be crushed stone, gravel and broken bricks.
Crushed stone: It is an excellent coarse aggregate provided. It is obtained by crushing granite, sand stone and close grained lime stone.
Crushed granite chips are commonly and advantageously used in reinforced cement concrete.
Broken bricks well burnt and over burnt bricks are broken into suitable size and used as aggregate. It should be well watered before its use. Broken bricks are used as aggregate for concrete in foundations and under floors.
But generally crushed stone is only used as coarse aggregate.
b) Exact repeat of 2013 Q6b.
Ref:
Earlier post.