Study on Carbon Absorption Capacity and Pore Structure Evolution of Concrete Under Bending Load

In order to study the carbon absorption capacity of concrete under load， X-ray diffraction（XRD）， therrmogravimetry（TG） and mercury intrusion porosimetry（MIP） were used to explain the influence of different carbonization treatment time and load level on the mechanics and carbon absorption capacity of concrete.The grey entropy analysis method was used to analyze the effect of different pore structures on the CO₂ uptake of concrete. The results show that the CO₂ uptake in the compressive zone of concrete under different load levels increases first and then flat with the increase of carbonization time.In the early stage of carbonization treatment， the number of the most probable pore size and macropores of concrete increased， and the CO₂ uptake increases. In the middle stage of carbonization treatment， the most probable pore size decreases， and the CO₂ uptake tends to be gentle. In the later stage of carbonization treatment， the porosity decreases， the pore tortuosity increases， and the CO₂ uptake tends to be gentle. The order of influence on the CO₂ uptake of concrete is pore tortuosity > most probable pore size > porosity. When the concrete under the combined action of load and carbonization treatment is at a higher load level， the connectivity of concrete pores and the amount of CO₂ uptake increase. The number of large pores in the compressive zone of concrete under 60 % load level increases with the increase of carbonization treatment time， and its carbon absorption capacity is the best. The order of influence on the CO₂ uptake of concrete is macropore > large pores > gelpores > medium pores.