POZZOLANIC REACTIONS OF 6 PRINCIPAL CLAY-MINERALS - ACTIVATION, REACTIVITY ASSESSMENTS AND TECHNOLOGICAL EFFECTS

Six standard clays, before and after calcination at 3 or 4 temperature s and being mixed with Ca(OH)(2) [CH] in the presence of simulated cem ent pore solution, and with ordinary Portland cement, respectively, we re studied in detail. Chemical compositions of most clays conform well to the requirement in ASTM C 618. Water demand of clay-containing mor tar varies, depending on the crystal chemistry of raw clays, and on th e specific surface area of calcined clays. Measurements of XRD backgro und or alkali soluble Si are rapid methods in evaluation of the pozzol anic activity of clays. Compressive strength of mortars based on the r aw clays is affected by structure of clays. Calcination increases the pozzolanic activity of clays and the compressive strength of the Portl and cement - clay mortars. A close correlation exists between compress ive strength of mortars and particle size distribution of the dehydrox ylated clays. The most common reaction products of clay - CH mixtures are C-S-H-2 and C(4)AH(x), while C(2)ASH(8) and C(3)AH(6) were also de tected with clays rich in Al.