The interaction mechanism among particles in the hydration of composite cements

The increase in the amount and variety of additives in blended composite cements provides advantages in terms of mechanical, ecological and economic features. However, the type and the amount of additive materials in binder (cement) system is limited to such factors as an increase in the need for water and decrease in the rate of strength growth. Therefore, several studies have been conducted to increase the properties and the amount of natural and artificial pozzolans used in blended cements as much as possible with the purpose of no performance losses.The aim of this study was to determine the properties of blended composite cements prepared with different crystal and amorphous pozzolan raw materials and also to compare with reference cement CEM I PÇ 42,5-(OPC) comparatively. To serve this purpose, physical, chemical, mineralogical, microstructural, molecular and electrokinetical experiments were performed for the characterization of reference cement and supplemental pozzolan raw materials. The hydration progress of reference cement and blended composite cement pastes was analyzed by XRD, STA, FT-IR and SEM methods. Furthermore, contact angles and surface tensions were experimentally determined to show the interaction of pozzolan raw materials and reference cement, the properties of reference cements among their particles thermodynamically. The relationship between the properties of reference and blended composite cement pastes and all quantitative data acquired by the characterization of pozzolan raw materials was examined by means of regretion analysis.Data drawn from previous studies showed that the physical properties of pozzolans significantly depend on their molecular structures. The characteristics of molecular structure vary not only in terms of pozzolans being crystalline or amorphous, but also in terms of the presence of chemical elements in their content, which also affects the electrokinetic and ionic properties of pozzolans. In conclusion, the particles with positive charges interact with the particles of negative charges, resulting weak bonds in the beginning and strong bonds in the end.In comparing the 28-days experimental strength results of blended cements to the reference cement, the additions of fly ash, clinoptilolite, natural pozzolan, blast-furnace slag, diatomite and rice husk ash increased the strength values of 12 %, 31 %, 20 %, 20 %, 20 % and 41 % more respectively.Keywords: Pozzolan, Electrokinetics, Molecular Structure, Surface Energy