EFFECT OF CEMENT DUST COMPOSITION AND FLY ASH INCORPORATION ON THE PHYSICAL PROPERTIES AND STRENGTH OF BLENDED CEMENT

In this study tests were conducted with two types of blended cement; one was cement kiln dust
with ordinary Portland cement (CKD-OPC) and the other was a combination of cement kiln dust
and fly ash with OPC (CKD-FA-OPC). Three CKDs having different chemical compositions were
collected kom three different plants and mixed with OPC to produce blended cement 5 to 50% of
CKD. One of these CKDs, which satisfy the best performance in CKD-OPC blends, was used as
an activator to fly ash in CKD-EA-OPC blends. In these blends the total waste materials
(CKD+EA) were used as a partial replacement of 5, 10,15 and 20% of the cement content, and the
CKD and'FA wewcombined at different ratios; where the percentage of CKD to the total waste
' ' materials wtis 0, 30, 50 and 70%. The blends were tested for their water requirements for normal
consistency,setting times, soundness and compressive strength at 7 and 28 days age. Resdts of
'' these ?;& were compared to those of OPC. It was found that the CKD with lower contents of
bimi&l'b~ides (SO3, K20, Na20, Cl- and kee CaO) could be used in the production of blended
cement with quantities up to 35% of the cement content. The physical properties of these blends
were very close to those of OPC, and their compressive strengths were adequate. Also, when
a proper CKD to FA ratio was used; the akalis kom CKD activated the hydration of FA and
leading to a blend with satisfactoly performance. CKD-FA-OPC blends with 90% OPC and not
more than 5% FA had physical properties and strength comparable to those of OPC.