Effects of alkali silica/aggregate reaction on concrete structures in Bundelkhand region, central India

Abstract

The Bundelkhand massif covering 26,000 km2area forms the northern segment of Indian shield. It mainly consists of Bundelkhand gneissic complex (3.1 Ga) and granitic complex (2.5 Ga). These gneisses and granitoids are mainly traversed by E-W and NE-SW trending shear zones. Betwa a tributary of Yamuna is marked by number of concrete dams which are major resources of water in this region. The rock fragments of granites, gneisses, migmatites, basic, ultrabasics and metasedimentaries have been used as coarse aggregate for construction of dams. The main constituents of these rocks are strained quartz, altered feldspar and elastic (mica) minerals. The progressive development of reaction rims of alkali-aggregate and silica reactions were observed in three concrete dams; Sukuwa Dukuwa, Kamala Sagar and Saprar dams. The petrological studies of coarse aggregates (deformed gneisses, schist and granites) reveal that the higher percentage of strained quartz (50-60 %), altered feldspar (25-35 %) and elastic (micaceous) minerals with clayey matrix were found most deleterious reactive agents to cause alkali aggregate/silica reactions. It also indicates that the low-alkali cement and supplementary cementing materials have not been used with reactive aggregates to prevent AAR and ASR reactions.