IMPACT OF HEAT TREATMENT METHOD AND MILLET POD TYPE ON REAL DENSITY AND POZZOLANIC ACTIVITY INDEX BY ASH RESISTANCE

Artificial pozzolans derived from agricultural by-products are generally obtained by heat treatment. The thermal treatment method used and the type of waste influence the quality of the final product. The aim of this study was to measure the actual density and pozzolanic activity index of millet pod ash produced in three different ways. Ash A is produced by direct calcination of the husks from which the millet seeds are removed (without the stalk). Ash B is obtained by burning and then calcining the millet husks. Ash C is produced by direct calcination of the millet straw (husks + stalks). The actual density was determined in accordance with standard NF EN 1097-6. The pozzolanic activity index by resistance was measured on the basis of the recommendations of American standard ASTM-C618. For the ashes A, B and C produced, we respectively obtained true densities of 2.256 g/cm3 2.150 g/cm3 and 2.033 g/cm3. The pozzolanic activity indices per strength obtained were 0.42, 0.23 and 0.70 respectively. These results showed that the ash produced from direct calcination of raw millet waste (straw) had the best reactivity and the lowest density. It is therefore well suited to the production of low-density cementitious matrix composites.