Reducing Weight in Suspended Concrete Floors

Suspended concrete floors are found in storey buildings. The self-weight of concrete without additional live loads is great but buildings where the spans are large, weight reduction is done to avoid buckling of the floor. Buckling is where the concrete sags at the middle. The concrete is laid the same way but hollow blocks are added to reduce weight. The blocks are hollow in the middle and the reinforcements are laid in between them then concrete is added and vibrated to hold them together. The top concrete is about seventy six millimeters (three inch) thick.

The suspended concrete floor hollow blocks are either clay or concrete blocks. The blocks are two hundred to two hundred and fifty millimeters thick. The blocks that are at the beginning and at the end of a row are blocked on one side to avoid concrete from flowing inside the blocks. The ceilings from this kind of floors are flat and the ordinary down stand beams are not visible from below the slab soffits. These floors are ideal over big rooms like lounges, dinning and offices.

When the suspended slab form work is ready, the laying of the hollow blocks commences. The external beams are then laid into the forms. The internal beams for this kind of floors are laid within the slab thickness. These beams will span from the external ones across the room to the other end. The beams are also laid where walls are to be built on the slab. The hollow blocks are then laid on the form work in between the beams. They are arranged in rows of nine hundred millimeters wide with a spacing of a hundred millimeters in between the rows.

Once the hollow blocks are laid, the gaps in between are fitted with reinforcements. This bars span from the end beams and they are to hold the concrete together. A mesh fabric is then laid on top of the hollow blocks. After this is done concreting work commences. The concrete should be well vibrated to ensure the blocks are held tightly together. The concreting is done normally and is leveled and made smooth. Curing is done for twenty one days before stripping off the form work to pave way for plaster work.

Fundi Mjanja.