How do you encase steel beams in concrete?

Answer 1

When designing composite members, one first needs to consider the properties necessary of the beam, in response to the expected loading. Basically, what will the beam experience? Is it flexural loads, or compressive/axial forces? The loading will greatly influence how the steel moves with the concrete as they are bonded together, and whether or not some bonding grout or other bonding agents are needed.

There are many ways you can encase a steel beam in concrete, but let's assume one case: you have a beam that will take mainly flexural loads and that you want the steel beam to be fully encased by the concrete (no steel showing on the outside, in other words). What I would do is install formwork to encase the conecrete on a suitable, hard surface. Then, after having selected the right steel section for the beam, I would drill small holes in the beam flanges in order to attack galvanized anchors/wires. These can be placed anywhere you like, as long as there are not too many of them. These anchors, typically two on each side of the beam's total length, could be attached to cables or chains that are, in turn, attached to hoists or engine-mounts that can lower the beam carefully into the desired position inside the concrete formwork. Make measurements for how low the steel beam should sit in the concrete, and doublecheck your measurements: after this, there's no turning back. Add concrete to the mix and, if you have concrete vibrators, use them to allow for proper concrete mix settlement and extraction of air bubbles from the mix. This will also ensure a good bond between the concrete and the steel. Then, let the concrete set for 5-7 days and store it in a humid room or location (humid, not wet/rainy). Lastly, remove formwork and cut the wires/anchors that are sticking out of the concrete. I would put some appropriate sealant on these locations, as they can be sites for water infiltration in the concrete. Their inner portions cannot be removed at this point. So there you have it, my approach to encasing steel beams in concrete.