Impact of nano-TiO2 addition on the reduction of net CO2 emissions of cement pastes after CO2 curing

This investigation aims to study the effect of nano-TiO2 addition on CO2 uptake of cement paste during CO2 curing. Cement paste mixtures with different percentages of nano-TiO2 (0%, 0.5%, 1%, 2%), and two different types of curing (normal curing (NC) at 23 degrees C and 50% RH, and CO2 curing (CC) that includes a 12-h curing in a chamber with 20% of CO2) were studied. Compressive strength, X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), and an estimation of the net CO2 emissions were performed for each studied mixture and curing condition. All samples were tested at 48 h. Results showed that the optimum percentage of nano-TiO2 in terms of compressive strength is lower for CO2 curing samples than for NC samples. XRD and TGA results exhibited that the use of nano-TiO2 promotes the CO2 capture during the CO2 curing. Since nano-TiO2 reduces the size of CH, it increases the CH surface area. This may enhance the CH reactivity with the CO2, producing an increase in the CO2 uptake. Results also showed that not considering the effect of nano-TiO2 on compressive strength and promotion of CO2 capture would highly overestimate the net CO2 emissions of cementitious materials with nano-TiO2. It highlights the importance of selecting an adequate functional unit for the analysis.

Automated summary

This study found that the addition of nano-TiO2 can enhance CO2 uptake of cement paste during CO2 curing, but the optimal effect on compressive strength varies. Selecting an adequate functional unit for analysis is crucial for accurate assessment.