I just had a concrete column put around the 4 x 4 post on my porch, along with about 85' of balustrades. This is what they used: 'Quikrete' concrete bonding adhesive, 'Lapis Luster' clean-graded-kiln dried Monterey sand and 'Basalite' Type 1-11 cement. (sorry for using brand names, but I just took the information from the bags sitting in my front yard). I don't know the exact mixture other than it was quite stiff. Since the column was put on the existing concrete porch, that was the foundation. The mixture was placed at the bottom and up the sides. After they pressed them together they used two straps, one top and one bottom, to secure and pull the two pieces together. They leveled and straightened the pieces before the straps were tightened all the way. They will be back next week to finish up, so if you like I will watch closely to see how much of each product was used for their mixture.