Myths and Realities

Myth 1 :

Ordinary Portland Cement (OPC) with high compressive strength makes the structure durable

Reality 1 :

OPC with high compressive strength comes with high heat of hydration and large quantities of free lime which affect the durability of concrete

Myth 2 :

Higher the quantity of cement, higher is the strength and higher is the durability

Reality 2 :

Quantity of cement must be determined as per the mix design and hence must be optimal

Myth 3 :

Residential construction requires concrete with high compressive strength like M40 grade and above

Reality 3 :

Residential construction does not require high grade concrete unless specified. M20 grade of concrete is normally sufficient

Myth 4 :

Use of blending material like Fly Ash is not needed in concrete

Reality 4 :

Blending materials like Fly Ash are required from durability perspective as they convert surplus free lime into C-S-H gel and reduce heat of hydration

Myth 5 :

Fly Ash is inert and does not enhance any of the properties of concrete

Reality 5 :

Fly Ash is not inert and in fact has pozzolanic properties that get activated in the presence of Calcium Hydroxide to form compounds possessing cementitious properties. It also densifies the cement paste making it impermeable