Concrete Admixture Types
Glass Fibers
Glass fibers are chopped strands of glass recognizable by being straight are added to the concrete in amounts ranging from one to five percent by volume. This increases the overall strength and crack resistance of the concrete by creating a web of overlapping and intertwining glass fibers. Similar to how steel holds concrete together but on a much smaller and much more dynamic method
The latest technology in self supporting concrete uses a very high concentration of glass fibers creating a complex matrix of supporting fibers. Though self supporting concrete can not be achieved with entry level concrete mixes made at home, adding fibers to the concrete mix dramatically enhances the strength and resiliance to cracking of the concrete.
Fiberglass
Fiberglass is more common and easier to find than glass fibers, the fiberglass is recognizable as being curly and having a somewhat fluffy texture by comparison to the rigid and straight chopped glass fibers. Fiberglass ingrained concrete will also be stronger than regular concrete against cracks but less so than glass fibers. Additionally the use of fiberglass will often result in a furry texture in the finished concrete making them unsuitable for some situations.
Liquid Acrylic
Liquid acrylic is a white concrete additive with a similar appearance to milk. This additive is used in small quantities typically one to five percent of the amount of water, or liquid volume, that you are using in your mix. Acrylic increases the overall bond strength, smooth workability of the concrete as well as acting as a retarder that will somewhat delay the initial set time of the mixed concrete.
Bonding Agent / Glue
Bonding agent or glue is the same consistency and has the same smell as regular white household glue. Sold as concrete bonding agent this paste will make the concrete stickier and is ideal for using in mixes where you will be adding new concrete to old concrete. Use as one to three percent by liquid volume in a concrete mix, or mix only with cement powder and water to make a concrete slurry paste that you will use as a bonding layer in between old and new concrete.
Fly Ash
Fly Ash is a gray powder by-product of industrial manufacturing fly ash is a very fine powder that when used in small amounts can help to increase the overall density and ultimately the strength of concrete. Fly ash for concrete mixing is very difficult to find in many areas of the world.
Silica Fume
Silica fume is available in a more dense and less dense form, silica fume is a ultra fine powder that can dramatically increase the overall density and strength of concrete. The size of the grains requires a ventilator mask to be worn when working with silica fume as they can cause damage to your lungs. Though available, silica fume can be incredibly difficult to locate in smaller than commercial quantities.
Air Entrainer
Air entrainer acts essentially like a mild soap the air entrainer additive creates small bubbles in the concrete which allow for moisture expansion during freezing temperatures. Concrete in subzero conditions without air entrainer will have a tendency to spall, shale, crack and break prematurely.
Proceed to the section on Specialty Concrete Mixes