Excavator has done its magic. Within a few hours there is a 4 ft hole covering the whole area of our plot. The piles of soil on the sides have gone quite high. Now is the time for some Soil Compaction.
You can read more about Excavation in our previous blog post here.
Wait! Why do we need to Compact the soil?
Good question. Because your Soil Testing Report says so.
The density of soil particles plays a vital role in creating a solid Raft Foundation. Compaction makes sure that there is no air between the soil particles, and that they are as arranged as compact as possible.
Soil compaction gains more importance if your plot is Cutting. In a filling plot, land is filled artificially. This leaves the soil having more air between the soil particles. If it is not compacted properly, there are chances that it will get compact over time. Soil getting compact after the building is constructed is very dangerous and the building might collapse because of it. We don’t want that do we? Better safe then sorry!
Soil Compaction on our Plot
After the excavation, a thin layer of sand and gravel is added at the top of the soil. Now a bulldozer comes to the site. Remember the water boring we did before the excavation? Turns out It is required before we could start the soil compaction. Now our builder and his team starts spraying water over the land (which is now a mixture of soil, sand and gravel) and bulldozer starts rolling over the water sprayed area. Bulldozer moves slowly to make sure that its weight is removing the air between soil particles as much as possible. The more gravel disappears into the soil, the better soil compaction is. See the images from our site below:
Now that the soil is satisfactorily compact, work for the day is finished. Tomorrow’s we’ll com back for the next step.
Building a Raft Foundation
Raft foundation is a concrete slab sitting at the base of a building. Raft, together with the compact soil underneath it, provide stability to the building against earth quakes and other natural disasters.
If soil is already compact, why do we need a concrete foundation?
While Soil Compaction makes sure that the soil will not collapse in all or any part of the plot, foundation is a bit different. Foundation Raft distributes the weight of the building on the whole area of plot. Compact soil gives the Raft a solid ground to sit on and Raft provides a solid base to the building.
Foundation raft is a 9 inch concrete slab supported by a complex structure of steel rods. Steel rods are placed on the ground at 90 degrees angle and concrete is pored on them. The concrete is leveled by the construction team. The concrete gets solidified very quickly so the task is normally divided in to sections. Pore concrete on a smaller area, level it, move on to adjacent area, and so on.
Leveling the liquid concrete is interesting to watch, and it looks very shiny too. See the gallery below.
Now the first part of Raft foundation is complete. We are going to let it rest for the night. Next step will be the building of Brick foundation.
More on that later.
