1. Introduction to Reinforced Concrete Structural
Lecture (1-2) Part (2)
Introduction to Reinforced Concrete Structural
DR: Ahmed Afifi
Ass. Teacher: Ahmed Said

2. 2- Source:
a- Natural aggregate: The natural sands and gravels are the product of
weathering and the action of running water, while the stone sands and
crushed stones are reduced from natural rock by crushing and screening
of quarried material.
b- Artificial aggregate: are usually produced for some special purposes,
for example: burned expanded clay aggregate for making lightweight
concrete.
Some artificial aggregates are a by-product of industrial process such as
blast furnace slag.
3- Unit weight:
a- Normal weight aggregate: It is usually the natural aggregate for which
the unit weight is between (1500 to1800)kg/m3.

3. b- Lightweight aggregate: It can be artificial or natural.
The artificial lightweight aggregates are produced as both coarse and fine materials. They have a lower density due to increase in porosity which results in an overall lowering of the concrete strength ceiling. Lightweight aggregates are not as dense as normal weight aggregates ( unit weight less than 1000 kg/m3) and because their elastic modulus is lower, produce concrete with a lower elastic modulus and a higher creep and shrinkage. Lightweight aggregates can be of natural sources such as Pumic ( a volcanic rock).
c- Heavyweight aggregate: Where concrete of a high density is required, in radiation shielding for example, heavyweight aggregates can be used.
The unit weight can be larger than 1800 kg/m3. Concrete densities of kg/m3 are obtained by using Barytes (a barium sulphateore). Even greater concrete densities are obtained using lead shot - around 7000 kg/m3.

5. 4-Admixtures:
Theyare chemicalsthat canbe added tothe concreteimmediately before orduring
mixingandsignificantlychangeits fresh,early ageorhardened state toeconomic or
physicaladvantage.

6. Properties of concrete

7. Concrete Compressive Test.

11. Concrete tension Test