A useful construction article on Raft or Mat Foundation
Raft or Mat Foundations are useful when soils contain low bearing strength and therefore weighty structural loads should be typically supported with them. Besides, if there is a chance that the structure may collapse because of being developed in mining area or unpredictable behaviour of its sub-soil water condition, raft or mat foundations are the best choices.
Raft or Mat Foundations offers a cost-effective solution to complicated site conditions, where development process is not convenient for pile foundation and separate column footing turns out to be unfeasible.
Raft or mat foundations contain dense reinforced concrete slab that covers the whole area of the bottom of the structure same as a floor. The slab is reinforced with bars located at right angles to each other both adjacent bottom and top face of the slab.
Often it is required to bear the extreme column load by organizing inverted main beams and secondary beams which are formed monolithically with the raft slab.
Construction Process: The raft slab is usually developed for a span of 30 cm. to 45cm. on all the sides of the exterior walls of the structure as such the range of excavation is partially over the area of the structure itself.
The excavation is developed to the desired depth and the complete excavated area is compacted perfectly. When this surface becomes dry, its base is ready to lay the raft or mat slab. All the essential protections should be taken throughout the reinforced concrete construction which are strictly complied with and further construction will commence only once the curing of the raft is completely finished.