A Comparison between the Shrinkage behaviour of Two Stage Concrete Incorporating Pump and Gravity Methods

Two Stage concrete or Perplaced Concrete is a type of concrete that is different from conventional concrete. It is made by first placing the coarse aggregates inside the formwork and then injecting the grout from the top (gravity method) or underneath (pump method) to make a uniform microstructure. Although application of Two Stage concrete is not as widespread as normal concrete due to its method of placement and essential need for skilled man force, it is a very good alternative for many structural purposes including pier construction, dams, retrofitting old structures and repair work. Also, it has improved mechanical properties due to its higher amount of coarse aggregates inside the matrix. This study provides two methods for casting prepacked concrete specimens and a comparison between the shrinkage values of the two proposed methods is presented. It was concluded that the shrinkage values of the pump method was lower than the gravity method and hence, the pump method was a more efficient method of placement compared to gravity method.

Keywords:

Two Stage concrete , grout , injection , pump , gravity