
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
