When asking question please do write about what exactly you are looking for;
there are many types of admixture available in markets and n number of brands too.
What is called admixture
flyash, microsilica and ricehusk ash etc. also called as admixture
admixture are those material which enhance the property of concrete.
Chemical admixture -
they are basically of 2 types base on their base material
SNF low to high - this are basic admixture which enhance the properties of concrete for little time say 1 hour to 3 hour - effect is not constant as the coating of such materials tends to break and allow the entry of water in cement (time of breaking depends on the quality of admixture)
PCE - this are the other admixture which do not allow to get break the layer of it on cement till specified time and after that time it breaks by self. this are high end admixture used where the travelling time required is more or in special concretes like scc.
We need to select the admixture base on the basic requirement of site.
Type of property enhancer in those admixture are listed below
workability enhancement by reducing water content (this have water reduction capability)
This are plasticisers and comes with varying range depends on your need.
Retarder - this do retardation of setting of concrete thus improves the workability and increase setting time of concrete.
Accelerators - this type of admixture enhance the setting properties, which are used where you want the concrete to be get set faster ( this type of admixture added in concrete generally before placing concrete in situ)
VMA - viscosity modifier use in special type of concretes.
There are lot of categories of admixture listing them here will not be useful to you.
I request you to post what you are looking for, we will try to answer your question.