Effect Of Mineral Admixtures And Additives On The Fluidity And Its Loss Of Cement Paste And Cement Mortar

High-performance is the development tendency of modern concrete technology, including the good workability of fresh concrete and the mechanics and durability of hardened concrete. Moreover, concrete structures become larger and taller, which brings on modern construction of mechanisation. So the excellent workability is primary for the construction of concrete structures. The development of modern concrete technique, especially the use of super plasticizer ensures the good workability of concrete. But at the same time, it results in the serious fluidity loss, which is disadvantageous to high-performance of concrete. There is a great deal of research work about controlling slump loss of concrete in the world, with some achievements made. With the favorable character of technique and economy, mineral admixture is a necessity in developing green concrete, which is the most ideal controlling method. But now, the research about improvement of mineral admixture on slump loss is mostly limited to its optimizing chemic elements of cement. On the other hand, as one of the primary elements of concrete, the fluidity of cement paste decides workability of concrete. Therefore, in this study, super plasticizer, retarding admix, air-entraining agent and mineral admixtures are mixed into cement paste and mortar, to research the effect of mineral admixtures and additives on fluidity of them. This will instruct us to apply mineral admixtures and additives more scientifically, to solve the fluidity loss of concrete. The results indicate FDN, polycarboxylic type super plasticizer, retarding admix, air-entraining agent and mineral admixtures can improve evidently fluidity and its loss of cement paste, and that the improvement mechanism of the mineral admixtures and additives are "postponement action", "particle size distribution action"and "sorption". While, owing to the sorption of gravels on additives, the fluidity law of cement mortar with additives is different from paste, but the character of fluidity loss is consistent with cement paste. What's more, fluidity and its loss of cement mortar with mineral admixtures and additives differ from the paste.