Investigation into viability of using two-stage (pre-placed aggregate) concrete in Irish setting

Abstract

Two-stage (pre-placed aggregate) concrete (TSC) consists of coarse aggregate, which is first deposited into the formwork, and grout, which is later pumped into the formwork from the bottom up to bind the stone together into a monolith. During the course of this study the formation of grout for two stage concrete was investigated using readily available 5 mm sand mixed in a slow speed paddle mixer. Silica fume and a superplasticizer were used in the mix to see if the necessary stability and fluidity could be achieved without the use of a specialized plant, essentially to see if TSC could be produced on a small scale using native Irish aggregates. A much higher degree of sedimentation was recorded during testing than was expected. As a result, the use of 5 mm sand and a slow speed mixer in combination were found to be not conducive to the successful production of TSC grout, without further research and testing.