Effect of Pozzolanic Materials on Setting Time and Properties of Fresh Concrete

The paper presents the result of an experimental investigation carried out on the effect of pozzolanic materials on six properties of fresh concrete including initial setting, final setting, bleeding, density, slump, and slump loss. Four pozzolanic concrete containing Silica Fume, Zeolite, Metakaolin (high reactive), and Fly Ash were compared in rheological properties with each other and with a control concrete containing no pozzolanic materials. In this study, the water to binder ratio is fixed to 0.47 for all mixtures, but owing to different pozzolanic materials, initial slumps were different in all mixtures. The addition of pozzolanic materials is based on the normal amount of usage of these materials in industrial concreting. The replacement of cement in each mix design is 7.5%, 10%, 15% and 10% by weight for Silica Fume, Zeolite, Fly Ash and Metakaolin, respectively. Results show that utilizing Fly Ash increases the workability and delays the hardening of concrete, which will result in less early age’s shrinkage. Beyond this, use of pozzolans like Silica Fume, Zeolite, and Metakaolin could be assumed as a catalyst which accelerates hardening of concrete and eventuates in more early age’s shrinkage

Keywords:

Fresh concrete , Slump , Setting , Bleeding , Pozzolan