ELASTICITY, CREEP & SHRINKAGE – Modulus of elasticity – Dynamic modulus of elasticity – Posisson’s ratio – Creep of concrete – Factors influencing creep – Relation between creep & time – Nature of creep – Effects of creep – Shrinkage – types of shrinkage.

1. Presented by:
MOOD NARESH
ASST.PROF
PETW

44. •Water is measured by its volume and it is specified as no
of litres per bag of cement. The further increase or
decrease in water to be mixed, depends on the quantity of
water present in sand and coarse aggregates, due to
Hygroscopic action or any other reason.
•The water present in aggregates should be subtracted
from the total quantity of water required for the mix to get
the desired quantity of water needed. Similarly, if
aggregates are dry and are likely to absorb water, extra
water should be added to maintain the water content in the
mix.
Water-Cement ratio
The ratio of the volume of water to the volume of cement
used to form concrete is termed as water-cement ratio.

45. Optimum Water content
This is the most suitable amount of water required for a given
proportion of materials to gain its maximum strength.
If the water content is below the optimum water content, the
process of setting of cement will not be completed properly.
Thus, there will be a decrease in the strength of concrete.
Similarly, if the water content is above the optimum water
content, the workability of concrete will increase but the
strength will decrease.
From studies and experiments, it is found that if the water is
increased by 10% above the optimum water content the
strength of concrete reduces by 15%, and the increase in 50%
water content reduces the strength of concrete by 50%.

46. Abram's Law
Abram’s law states that the strength of concrete mix entirely depends on the water-cement ratio. The increase in water-
cement ratio decreases the strength of the mix i.e. 'the strength of concrete is inversely proportional to the water-
cement ratio'.
Abram’s Law is a special case of general rule formulated by FERET with his experience and experiments.
Where,
S = Compressive Strength of concrete
A & B are empirical constants
(w/c) is water-cement ratio
[Note] Duff Abrams suggested empirically the values for A as 14000 and B as 7 in F.P.S. system and A as 984
and B as 7 in M.K.S. units.

53. https://www.constructioncivil.com/nondestructive-testing-of-
concrete/#gsc.tab=0