In this paper, concretes of different grades were exposed to five different CO2 concentration levels (2, 10,
20, 50 and 100% by volume) using accelerated carbonation test methods. The relationship between the
depth of concrete carbonation and CO2 concentration was investigated. The diffusion mechanisms of
CO2 gas in concrete were analysed through the scanning electron microscopy (SEM) observations.
Experimental results showed that, under the same carbonation age, the increase of carbonation depth
was found to be high when concrete samples were exposed to low CO2 concentrations (i.e. 2–20%);
and low when the samples were exposed to high CO2 concentrations (i.e. 50–100%). The reason for this
is mainly due to the microstructure change caused by concrete carbonation, which makes the surface
layer denser thus lowering the rate of CO2 diffusion into concrete. SEM results showed that carbonation
decreased the porosity of concrete by clogging up the pores and reducing the pore sizes. It is believed that
the diffusion mechanisms of CO2 into concrete under high and low CO2 concentration levels would be
different.
 
In this paper, concretes of different grades were exposed to five different CO2 concentration levels (2, 10,20, 50 and 100% by volume) using accelerated carbonation test methods. The relationship between thedepth of concrete carbonation and CO2 concentration was investigated. The diffusion mechanisms ofCO2 gas in concrete were analysed through the scanning electron microscopy (SEM) observations.Experimental results showed that, under the same carbonation age, the increase of carbonation depthwas found to be high when concrete samples were exposed to low CO2 concentrations (i.e. 2–20%);and low when the samples were exposed to high CO2 concentrations (i.e. 50–100%). The reason for thisis mainly due to the microstructure change caused by concrete carbonation, which makes the surfacelayer denser thus lowering the rate of CO2 diffusion into concrete. SEM results showed that carbonationdecreased the porosity of concrete by clogging up the pores and reducing the pore sizes. It is believed thatthe diffusion mechanisms of CO2 into concrete under high and low CO2 concentration levels would bedifferent.
การแปล กรุณารอสักครู่..
