RESEARCH ON THE ALKALI-ACTIVITY OF THE NATURAL AGGREGATES FROM YI CHANG CHANNEL SEGMENT OF YANGTZE RIVER

摘要

The Yangtze River is the largest river in China. The sandstone of some channel segments are excellent natural concrete aggregates, which have rational particle size distribution and a good physical and chemical property. The active aggregates from the storehouse of Yichang channel segment of Yangtze River are mainly flint, rhyolite, secondly tuff and volcanic breccia. By the methods of geologic, petrographical, physical and chemical method, motar bar length method and rapid method, the natural aggregates of Yichang channel segment are investigated, and it is confirmed they contains flint, rhyolite, tuff and other active aggregates. The conclusions from geologic, petrographical, physical and chemical method and rapid method are consistent. By mortar bar length method, the long-term age result of the natural aggregates shows that when the alkali content in cement reaches 0.78%, the expansion rate of mortar sample with 5-year age will beyond 0.1%, which is the harmful value limit. Because of the importance of the concrete engineering, and considering the safety and durability of engineering, it is very important to control the alkali content in cement or add some fly ash when using the natural aggregate of Yichang channel segment of Yangtze River.