Improving bond strength in RCC dams

Expanding applications of “roller compacted concrete” (RCC) in modern dam engineering necessitates clear understanding about its engineering properties and behavior under different loading conditions. Due to the existence of numerous horizontal construction joints in RCC dams body one of prime requirements for a reliable and safely designed structure is obtaining sufficient bond strength at layers interfaces. In order to improve uniform stress distribution across construction joints as well as increasing water tightness, polymer modified slurries was proposed to be studied in a laboratory investigation program. Specimens were fabricated in two layers using crushed alluviums as aggregate having a MGS of 25.4 mm and Type II Portland cement. The polymer-modified slurry was made of Styrene Butadiene Resin (SBR). Experimentation covers practical range of polymer content and water/cement ratio in mix designs of the slurry. To measure specimens bond strength, a direct shear apparatus specially developed for the program was employed. Observations indicate that: a) Increasing polymer content of the slurry, within a range of 0 up to 11.4 per cent (by cement weight or 0.4 ≥ P/C ≥ 0 ) improves bond strength; this improvement being a function of age and water/cement ratio. b) Decreasing water/cement ratio of the slurry from 0.8 to 0.5, as a practical minimum, increases the index of bond strength improvement. c) Applying polymer modified slurries as a joint binder, does not have a noticeable effect on compressive strength of specimens, but reduces overall permeability.

Keywords:

RCC , Bond strength , Polymer slurry , Concrete dams