Bio admixtures are functional molecules used in building products to optimize material properties. They include natural or modified biopolymers, biotechnological and biodegradable products. Concrete and dry-mix mortars (e.g. wall plasters or tile adhesives) represent two major applications for bio admixtures. Examples of bio products used in concrete are lignosulfonate, sodium gluconate, pine root extract, protein hydrolysates and Welan gum; and in dry-mix mortar methyl hydroxypropyl cellulose, hydroxypropyl starch, guar gum, tartaric acid, casein, succinoglycan and Xanthan gum. In a number of applications, bio admixtures compete well with synthetic admixtures. Sometimes, they are indispensable in the formulation of certain building products. Their market share is expected to increase because of technological advances, particularly in the field of microbial biopolymers, and because of the growing trend to use naturally based or biodegradable products in building materials.