When slabs and beams are to be monolithic with the supporting walls and columns, what can we do to ensure that the concrete will really be monolithic?
The concrete used in the top two or three feet of the walls and columns should have the lowest slump that can be adequately vibrated and particular care should be taken to fully consolidate the surface. The concrete in the walls and columns should be allowed to settle as long as possible (about one to three hours) before placing concrete in the top fillets, slabs and beams but all work should be completed while it is still possible for a running vibrator to penetrate it of its own weight. The surfaces should be protected during this time from having dirt blown or swept onto them. After the fillet, beam and slab concrete are placed the vibrator should be made to penetrate and revibrate the concrete in the tops of the walls and columns.