The use of concrete blocks in building solid structures has been in practice for decades. Concrete blocks offer a different option than poured concrete and are frequently used in foundations and walls. Concrete blocks are made of concrete poured and shaped into a mold. They generally have 2 hollow cells in each block. The blocks are generally 16 inches long, 8 inches deep and 8 inches high, though there are other variations available. They are typically stacked either perpendicularly or staggered to contribute to their stability.
Frequently, rebar and poured concrete are used to reinforce the strength of concrete blocks. Here you will find information on how to put rebar columns between concrete blocks.
Step 1 - Locate Power and Gas Lines
You will need to have your local utility company come out to locate any underground power lines to ensure that they are not damaged or interfered with during the building process. Rebar is frequently driven into the ground, and it could be deadly to drive it into a buried power or gas line. Know before you dig (or in this case, drive) your rebar where the utility lines are.
Step 2 - Start the Column
First, you will need to start the concrete block column. Mix the mortar according to package directions. Put down ½ inch of mortar onto the surface that you will be building the column. For a column 16 inches by 16 inches, you will use two cinder blocks per layer. Make sure the base is level. Set the bottom two blocks on the mortar. Add more mortar on top of those two blocks, and add another layer of concrete blocks, positioning them perpendicular to the first layer.
Step 3 - Install Rebar
By installing rebar in the openings of the concrete blocks, you will be providing additional stability and durability to the structure. The length of rebar that is chosen will depend largely on the size of the project. You should have a rebar that runs the majority of the height of the structure. You can install additional rebar as you build though, staggering the lengths of rebar and overlapping lengths. So if you can not find a 30-foot piece of rebar, don't worry. Drive the rebar into the ground after starting the first couple of layers. If you are building the column on a concrete slab, do not worry about this yet.
Step 4 - Fill Spaces
Mix the concrete according to package directions. You do not want the concrete too soupy, but you also do want it to be pourable. Once you have reached a good consistency, pour the concrete into the "cells" that are created by the spaces in the concrete blocks as they are stacked. The concrete will naturally fall around the rebar if it is driven into the ground. If you have not yet added rebar, let the concrete set up for a little while (don't let it cure completely), then drive the rebar into the soft concrete until it reaches the slab below. Pour concrete in layers, and add rebar as needed, overlapping heights of rebar by at least 1 foot (for short structures), and up to 3 feet for structures higher than 15 feet.