Effect of grinding on early age performance of high volume fly ash ternary blended pastes with CKD & OPC

Abstract

This study investigated setting times and early age compressive strength of the high volume fly ash (HVFA) blended pastes prepared with ground materials. The pastes consisted of 60% Fly Ash+30% Portland cement (CEM I)+10% cement kiln dust (CKD) and tests were carried out for four different fly ashes. In phase 1, all the constituent binder materials (class F-fly ash, CEMI and CKD) were initially mixed in the relevant proportions and were ground for varying time periods (1, 2 and 4h). In phase 2, the CEM I and CKD were mixed and ground for different time periods (1 and 2h) and then added to the unground fly ash. Both wrapped and submerged curing were used for compressive strength test samples. Overall, grinding of constituents appeared to be largely ineffective at increasing 2day compressive strength although strength enhancements at 28days were generally observed. Paste samples that were made from interground constituents generally achieved higher 28day strengths than corresponding pastes where only the activators were ground, although this was not consistent throughout so further investigation is suggested in this area. Submerged curing is generally less effective in increasing compressive strength than wrapped curing as leaching of CKD is suspected to have occurred.