Durability of concrete covering layer of spillways

Abstract

Covering layer - 30 - 40 mm concrete surface layer, protecting reinforcement from corrosion and its condition shows the durability of whole construction. Due to environmental impacts (freezing-thawing cycles, abrasive effects of waterborne sill, sand, gravel, rocks, ice, wave beat and etc.) some deteriorations of the spillways (hereinafter - SW) take place, which influence negatively not only some SW, but after their failure the danger arises for the reliability, durability and safety of the hydroscheme in general. In Lithuania there are 617 ponds evaluated as potentially dangerous hydraulic structures. If dangerous defects and deteriorations are not repaired in time, a big technical and ecological loss may occur. The purpose of these investigations based on field research is to establish actual quantities of compression strength of concrete used in the spillways, the depth of pitting on the surfaces of structures, actual functioning period of structures and their interrelationship with main durability indices. In 1998-2009 we investigated the mean compression strength and the depth of pitting of the cement coarse -grained without additives concrete covering layer of 15 shaft spillways in Lithuania's earth dams. By means of investigated values of concrete compression strength, actual functioning period of a structure, average depth of pittings and using established average deepening speed of a pitting in a structure v, durability of spillways covering layer can be evaluated by time (T30mmand T40mm), which equals to reinforcement uncover of reinforced concrete structure. Using estimated durability indicies T30mm and T40mm for designed reinforced concrete spillways, there is a possibility to choose such strength concrete, that during the intended period the reinforcement of these constructions wouldn't uncover. The data of investigations published in the article is given for improvement in designing ... [et.al]