Early-age performance of self-compacting concrete under stepwise increasing compression

Increasing compression during early-age hydration significantly influences the performances of concrete in underground structures, for example, when self-compacting concrete (SCC) is backfilled for tunnel support. Knowledge regarding the properties of backfilled SCC is important for predicting structural risks, especially in deep-buried tunnels. In this paper, a dedicated oedometric test (confined undrained uniaxial compression) device is proposed, via which stepwise increasing compression can be applied to SCC from an early age. The strain, stress, and resistivity of specimens are measured using the apparatus. The strength, chloride permeability, and microscopic images were acquired after the oedometric test. The results indicate that early-age compression increases the oedometric modulus and results in a higher creep. Compression results in the compaction of the matrix; however, it produces defects at the aggregate–matrix interface. Various compression rates and loading ages are investigated to reveal the effect of the compression history on SCC performance.