Chemical admixtures can be purchased from builders merchants and may be used in DIY work.

The most widely used admixtures are plasticisers which increase the workability (as opposed to mortar plasticisers which entrain air) of the mix without extra water being added and air entrainers that provide frost resistance to at risk exposed concrete. Viscosity modifiers (sbr or acrylic suspensions) are also used especially in repair of smaller areas of concrete.

Admixtures require very careful proportioning during mixing as they are generally only added in very small proportions to the amount of cement and should be used only in accordance with the manufacturers instructions. Small sachets of admixture can be bought from builders merchants to add into DIY concrete mixers.