Acid (usually by phosphoric acid) activation of aluminosilicate precursors provides a new group of inorganic materials with promising chemical and thermal stability. The three mixtures in system metakaolin – phosphoric acid were prepared; they differed in Al/P molar ratio (1, 1.5, 2). Compressive and bending strength were determined in the age of 1 week; the 1 day 60 °C curing was applied. The highest compressive strength reached sample with Al/P ratio 1.5, what falls within the range found in literature. The porosity of the samples increased with the increasing Al/P ratio, thus there was not any simple relationship between strength and porosity. It implies that Al/P ratio influenced not only porosity and pore size distribution, but also the nature of activated cementing product.