Use of non-destructive tests to explain manifested pore structure changes in cryogenic concrete

The pore structure serves as a transport medium for external agents that cause concrete deterioration and controls the main properties of concrete. This work utilized non-destructive tests to explain pore structure changes in concrete assessed for direct liquefied natural gas (LNG) containment. It sought to investigate concrete mixture designs that are least susceptible to internal damage during cryogenic cooling. Concrete specimens were prepared using limestone and trap rock as coarse aggregates and river sand as fine aggregate. The effect of air-entrainment was also considered. Microcracking in the concrete specimens was monitored using coupled acoustic emission (AE) sensors during cryogenic cooling and warming. While proton nuclear magnetic resonance (NMR) measurements and x-ray computed tomography (XRCT) imaging were conducted on the specimens before and after the temperature swings. The manifestation of pore structure changes was assessed using water and 'chloride permeability' tests. Significant microcracking and changes in NMR porosity and mean pore size, and CT-calculated porosity corresponded to changes in water permeability trend but not 'chloride permeability' trend. Air entrainment caused a reduction in chloride penetrability. The results show the utility of the non-destructive tests in explaining pore structure changes in cryogenic concrete and identifies the damage-resistance potential of the concrete mixtures.