A Consideration on the Mechanisms of Improvement in Compressive Strength of Concretes Using both Classified Fine Fly Ashes and Limestone Aggregates
Tohru HASHIMOTO, Yuji SHIRANE, Haruka TAKAHASHI and Kazuyuki TORII
Abstract:In the Hokuriku district, ready-mixed concrete plants using both classified fine fly ashes and limestone aggregates have been steadily increasing in order to produce a highly durable concrete against ASR and chloride attack problems. Therefore, in order to investigate on the mechanisms of improvement in compressive strength of concretes using both classified fine fly ashes and limestone aggregates, the development of compressive strength in concretes with and without classified fine fly ashes and limestone aggregates was respectively tested. Then, the specimens of 4 cases of a combination of the concretes were examined by means of mercury porosimeter, polarization microscope and scanning electron microscope. As the result of tests, it was confirmed that the limestone aggregate and its powder contributed the increase in compressive strength of concretes, due to the refinement in the texture of cement pastes and the reduction of interfacial transition zone around aggregates mainly at early ages until 7days, also that classified fine fly ashes contributed them mainly at late ages after 7days, in which both beneficial effects were complementary at both early and late ages. Key Words:Classified fine fly ash, Limestone aggregate, Compressive strength, Microstructure, Interfacial transition zone, Pozzolanic reaction