Significance of mix design in pavement

There is a tendency of the Engineer fraternity to increase the compressive and flexural strength of concrete by addition of more cement in the concrete mix. Therefore further calculations like grade of concrete is based on the quantity of cement in the concrete mix. It is generally assumed that   M-40 grade concrete means 400kg of cement.

But because of the advances in admixture the M-40 grade concrete can be achieved by adding 300-350 kg of cement.

Role of flyash in the mix to achieve higher flexural strength

 There is a misconception that addition of flyash deteriorate the concrete properties.That may be true to some extent in construction industry but in pavement addition of 40-50% of flyash in concrete mix help in improvement of flexural strength of the concrete.

What happens to concrete mix   by adding flyash

There is an interfacial zone  exist in between aggregate and cement which controls the properties of concrete .By adding fine and pozzolonic material like flyash it helps concrete to become impervious.

Addition of  flyash and high water reducing admixture  SCC concrete

is achieved

Advantages of flyash addition in concrete mix for pavement

·         Improvement in flexural strength

·         The interfacial zone is impervious

·         The hydration mechanism is modified

Ideal design to achieve M-40 grade pavement quality concrete

Material	Quantity kg per M3
Cement	350-380
Flyash	150-200
Microsilica	10-30
Admixture	4-5
Water	150-180

The result of the above mix

Pothole free road tested for last seven years. No cracks