Ceramics-Silikáty 48 (2) 49-58 (2004)

ELECTRICAL PROPERTIES, PHYSICO-CHEMICAL AND MECHANICAL CHARACTERISTICS OF FLY ASH-LIMESTONE-FILLED POZZOLANIC CEMENT

M. Heikal, I. Helmy, H. El-Didamony, F. A. El-Raoof

In this paper fly ash was replaced partially up to fully by limestone dust. The change in the electrical conductivity was reported during setting and hardening after gauging with water. The phase composition was studied by XRD and DTA. Degree of hydration, gel/space ratio, reaction ratio, porosity and mechanical properties as well as free lime content was studied. The results show that the substitution of fly ash by    5-10 wt.% limestone in SRC pastes decreases the conductivity. Increase of limestone content (15 and 20 wt.%), the electrical conductivity increases than sample free from limestone (S.0). 5 wt.% limestone extended the final setting times. On the other side, the increase of limestone content, the final setting times are shortened, this is due to the filling effect of the limestone. The combined water, degree of hydration and the gel/space ratio increase with limestone content. It was shown that the free lime of S.0, S.5 as well as M.0, M.5 increase up to 7 days, and then decreases up to 90 days. On the other hand, the compressive strength and total porosity decrease with limestone content.

Keywords: Fly ash, Limestone, Conductivity, Phase composition, Mechanical properties