One of the ways to get the active mineral admixtures for dry mixes is kaolin clay baking at temperature of 600-800°С. The reason for application such an additive is that among all modern minerals the most reaction-active towards a lime is metakaolinite. Possibility of application of mixed-layer clays of the Penza region as a structuring additive in lime dry mixes is considered. Differential-thermal analysis of kaolinite clays from various deposits was carried out. The structure of sand-lime specimens was being studied by method of X-ray phase analysis. Efficiency of application of clay that was baked at temperature of 400-500°С is shown. It is indicated that introduction of the clay burned at temperature of 400-550°С in number 10% from mass of a lime promotes durability increase in compression that is 17,85-63%, as a function of technology, temperature of baking and a type of clay.