Determination of carbonation resistance of concrete through a combination of cement content and tortuosity

The underlying motivation of the study is to understand the effect of CO2 buffering capacity and pore structure characteristics on the rate of carbonation of concrete. An investigation on the influence of different parameters of concrete on the rate of carbonation of 11 concrete mixes made using PC (Portland cement) and six different SCMs (Supplementary cementitious materials) is presented in this work. Compressive strength and various transport properties (oxygen permeability, porosity, resistivity and sorptivity) of concrete are measured after 28 days of curing. Concrete samples are subjected to accelerated carbonation conditions (2.5% CO2, 60% R.H. and 20 degrees C temperature) for 60 days after the end of the curing and preconditioning period. No notable correlation is observed between the rate of carbonation and measured parameters of concrete. A pragmatic approach to measure the carbonation resistance of concrete is proposed by means of a carbonation resistance factor derived using the tortuosity and cement content of concrete. The carbonation resistance factor could be effectively used to compare concrete mixes containing different SCMs for their carbonation resistance providing an alternative to tedious and timeconsuming carbonation tests.