Effect of concrete preconditioning method on accelerated carbonation rate

Abstract

Several methods have been proposed for the accelerated carbonation test of concrete, but there is no consensus on the best procedure for preconditioning the specimens. Thus, this study aims to assess the effects of four preconditioning methods - ISO 1920-12:2015, EN 13295:2004, XP P 18-458:2008 and RILEM TC 116-PDC:1999 - on the accelerated carbonation test. Four different concrete mixtures were used to ensure variations in mechanical strength and porosity. The specimens were subjected to accelerated carbonation in a chamber with 3% CO2, 65% RH and 23 °C for 14, 28 and 42 days, so that a database of 1536 carbonation measurements was produced. Internal and surface moisture of the concrete were measured at various stages throughout the experiment. Statistical analysis revealed that the preconditioning method significantly impacted the concrete’s carbonation rate - Fcalc (126.68) ≫ Ftab (2.61), with p-value ≅ 0. Preconditioning affected the concrete’s moisture content at the beginning of the process, and inverse linear relationships were found between concrete surface moisture and carbonation depth (0.85 ≤ R2 ≤ 0.99). The study points to the usefulness of the surface moisture technique to monitor specimens during carbonation tests, and it concluded that XP was the best among the four methods studied.