The microstructure and nano-mechanical performance of concrete in coastal ultra-deep mine engineering environments

Abstract

This research reports on the microstructure and nano-mechanical performance of different hardened pastes exposed to simulated coastal underground environments. The structure and density of the calcium (aluminium) silicate hydrate [C-(A)-S-H] phases in the hardened pastes were explored by nuclear magnetic resonance (NMR), backscatter electron (BSE) detector and nano-indentation. The results indicate that the average main chain length and C-A-S-H ratio of C-(A)-S-H in reactive powder hardened paste under 60℃ corrosion conditions for 420 days (RPHP-SE2) reached 7.19 and 47.39%, respectively. The two values were much higher than those of high-performance hardened paste (HPHP) under equivalent conditions. Meanwhile, the C-(A)-S-H in RPHP-SE2 had the densest gel structure and highest nano-mechanical strength, which is beneficial to macroscopic mechanical properties and durability. RPHP can dissipate environmental energy and enhance its strength. The results are of great significance to ensure the safety of deep mines as the deeper depths of the earth are explored.