As you already imagined on your mind, you can simply say that mass concrete is a very large quantity of concrete for construction purpose.
You know that, when you need to construct a large mass construction, you need to look into their chemical aspects not only their physical aspects. The amount of heat generation during the hydration of these large mass construction should be within the limit.
When the minimum cross-sectional dimensions of a solid concrete exceed 2 to 3 feet or cement content exceeds 364kg/m³, the quantity of heat generated also need to be considered to avoid cracking.
What is Mass Concrete?
Mass concrete is a large volume of a cast in place concrete with dimensions large enough to require that measures be taken to cope with the generation of heat and attendant volume change to minimize cracking.
These types of cracking in mass concrete effects in excessive shrinkage, loss of durability, loss of structural integrity etc…
You know that the hardening of concrete takes place during the hydration of cement. The hydration of cement is an exothermic reaction. Exothermic reaction means during hydration, cement releases heat in very vast amount.
The concrete has very low thermal conductivity, hence the temperature at the core portion of mass concrete will be more than the surface of the concrete. The surface of the concrete is open to atmosphere.
The inner core of concrete may raise its temperature to 60-degree Celcius. Therefore a huge difference in temperature will be created between inside and outside of the concrete This leads to the formation of thermal stress in concrete.
Uses of Mass Concrete
Mass concrete is widely used for large construction purposes such as
- Metro Railway
- Coloums of high rise buildings.
How to avoid thermal stress or cracks in mass concrete?
You just have read that, the temperature gradient between the inner core and outside surface is the major reason for the development of cracks.
You can use hot water during the curing of mass concrete. When using hot water at the surface of the mass concrete, there will be a small difference in temperature between the inner core and outside only surface. This reduces cracking of mass concrete.