Experimental and numerical studies on axial compression performance of low-porosity non-dispersive underwater concrete columns

Non-dispersive underwater concrete (NDC) is extensively used in underwater engineering. This study firstly proposed a novel low-porosity NDC. Secondly, the effect of slenderness ratio, porosity, and concrete strength grade on the axial compression performance of low-porosity NDC columns are investigated. Finally, a novel calculation method for determining the axial bearing capacity of low-porosity NDC columns is proposed by modifying the stability coefficient and introducing the hydraulic pressure influence coefficient. Experimental and numerical results showed that the novel NDC's porosity and maximum pore diameter are respectively 61.8 % and 80 % lower than that of ordinary NDC. In addition, compared with the ordinary NDC column, the low-porosity NDC columns had denser crack distribution and narrower crack width in failure; the peak load was 32.8 % higher and relevant axial compression displacement was 2.59 % lower; the slenderness ratio and concrete strength were the main factors affecting the axial bearing capacity of the low-porosity NDC columns, which is similar to the rule of ordinary concrete columns; the effect of hydraulic pressure on the low-porosity NDC columns was small. Furthermore, compared with conventional axial bearing capacity calculation approaches, the proposed method correlated strongly with the experimental results.