Calcium Flakes

When added to wet concrete (actually added into the water before adding to concrete mix for best results) will substatially increase the rate at which the concrete begins to set up. This would be common in cold weather or sub zero concrete applications to help avoid having the water in the concrete freeze before it had a chance to activate the cement chemical reaction.

As this chemical reaction occurs, heat is generated from the concrete and by using calcium to force the chemical reaction to happen faster, greater amounts of heat are generated. This assists the concrete to further resist the effects of sub zero temperatures.

Liquid Acrylic

Acrylic is a retarder, meaning that it slows the initial set time of concrete. This is the opposite effect of calcium flakes. This would be used for applications where you need additional time to place, work and finish the concrete before it sets up. Additionally liquid acrylic will change slightly the working feel of the concrete giving it a smoother and stickier overall consistancy. Acrylic also helps to increase the finished strength of concrete and is a common ingredient in specialty and engineered concrete mixes.

Liquid acrylic concrete admixture is not to be confused with concrete bonding agent. Liquid acrylic is viscous similar to milk where concrete bonding agent is very similar in texture and smell to white wood glue. Acrylic is not a good choice for bonding concrete.

Water Reducers & Plastisizers

Water reducers, sometimes called plasticisers or superplasticisers are used in concrete to reduce the amount of water required in a concrete mix while still achieving sufficient slump for whatever the concrete application is. The logic behind this is that the more water that you add while mixing concrete, the weaker the finished product concrete will be.

This is a very serious concern since a small amount of water can dramatically reduce the strength. This means if you need a concrete with a high enough slump to flow into forms with minimal vibration then you would need to add enough water to completely compromise the strength of the mix. By adding water reducers you can have a concrete mix that has a high slump, which means watery, without actually adding enough water to reduce the strength of the mix.

Glass Fibers

Glass fibers are added to concrete mixes to increase the strength of the concrete. In the same way that adding steel grids or mesh inside of concrete will increase the finished strength, adding glass fibers into the mix increases the strength without the need for steel grids. There are two main kinds of reinforcing fibers which are glass fibers and fiberglass. Fiberglass looks like clumps of curly hair stuck together, each piece being about .5 to 1 inch long. They need to be seperated as they tend to clump together in the mix.

They can also give the concrete a somewhat "hairy" finished look as the fine fiberglass hairs will stick out from the finished concrete. These can be burned off with a torch or heat gun after the concrete has cured. Glass fibers are much harder to find and are more expensive than fiberglass. Glass fibers are chopped strands of glass and are easily recognizable over fiberglass as chopped glass fibers are completely straight. Glass fibers significantly increase the strength of a concrete mix and fiberglass somewhat increases the strength of concrete.

Coloring agents & Pigments

Coloring agents that are added directly to the concrete mix are called integral colors. This allows you to have a concrete that will look good long into the future which is the main concern with topical coloring systems in concrete. If you stain or paint a concrete a vivid color and then it chaps or cracks a little, the gray concrete underneath with stand out with stark contrast to the topical color. With an integral color even chips or cracks in the concrete will be the same color as the exposed finished surface allowing the concrete to look better for longer.

The limitations of coloring agents and pigments is that it is impossible to match one batch of concrete to the next as there are many variables that impact the final color of an integral mix concrete. It is strongly recommended that you mix enough concrete in a single mix to cover the entier area you are working on to ensure consistant color throughout your concrete project. Due to the size and scope of this, most integral color concrete projects should use ready mix concrete so that you can have all the concrete you need in a single batch mix.

Proceed to the Concrete Aggregates section