Complementary use of thermogravimetric analysis and oven to assess the composition and bound CO2 content of recycled concrete aggregates

Abstract

The carbonation of recycled concrete aggregates (RCA) has emerged as a possible significant carbon sink to mitigate the increase of CO2 concentration in atmosphere and global warming. A reliable determination of bound CO2 content is thus needed to optimize carbonation processes but there is no real consensus on the existing quantification methods, mainly based on thermal decomposition of calcium carbonate. With the aim of developing a relevant quantification method of bound CO2 during the carbonation of RCA, an experimental study based on the combination of two main techniques – thermogravimetric analysis (TGA) and high-temperature oven – was performed at different scales: paste, mortar, and concrete. XRD analyses allowed highlighting the overlaps between the decomposition of portlandite and calcium carbonate polymorphs during linearly increasing temperatures. Oven and TGA with isothermal steps were found to provide consistent and complementary data on RCA composition and their bound CO2 content from initially dried specimens.