Concrete casting

The first thing prior to casting is to thoroughly clear the formworks from dust, oil, etc. This should be done not only to ensure the building’s strength but also to set a technical-social example, in other words to set an example of professional behavior for all people working in the building site.

Concrete’s casting must be done directly from the pump’s hose end. The concrete must be poured inside the slab’s formwork in vertical and not horizontal layers. This happens because in case concreting has to be stopped for a long period of time, when it is resumed the new con-crete will not bind with the old one and a horizontal joint will be created. On the other hand, when concrete fills the formwork parallel to the thickness axis, a potential stop in casting will lead to the creation of a vertical joint.

The boom’s hose end should be around 0.50 m above the formwork of the element to be casted. An exception can be made for regular columns and shear walls, where it can be up to 2.50 m above the bottom. In cases where columns or shear walls have a relatively large height e.g. 5.0 m, concreting must be done by one of the following ways:a) The boom’s hose end is positioned in an adequate depth inside the column’s formwork,b) Extra pipes are placed from the upper part of the column to an adequate depth and con-crete is poured through them with the use of a special funnel.c) Openings with adequate size are created e.g. around the middle of the formwork and the concrete is casted through them (technically challenging procedure).

The (a) and (b) procedures are more practical but they require a certain amount of space. For example when using the boom’s hose end this space must have a diameter around 180 mm and when using the extra pipes this diameter is decreased to 160 mm. The required space can be provided only if columns’ casting is performed separately from the rest of the elements. This means that concreting should not be done simultaneously in columns, beams and slabs with the use of one unified formwork. In earthquake prone regions simultaneous concreting should be avoided for one more reason: columns have a large amount of stiffness and therefore they are used for securing the position of formworks and scaffolds in cases of seismic events both during the casting and the curing process of the beams’ and slabs’ concrete.