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## Cement and Concrete Composites

Volume 123, October 2021, 104160

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

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https://doi.org/10.1016/j.cemconcomp.2021.104160
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## Highlights

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  This study evaluates the effect of nano-TiO2 addition on CO2 uptake during CO2 curing.

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  Four nano-TiO2 dosages and two curing types (normal and CO2 curing) are analyzed.

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  Optimum nano-TiO2 level regarding compressive strength is lower in CO2 cured samples.

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  Nano-TiO2 increases the early CO2 uptake of cement paste cured with CO2.

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  Nano-TiO2 decreases the net CO2 emissions of both normal and CO2 cured cement paste.

## Abstract

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 °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.

## Keywords

CO2 capture
Cement paste
CO2 emissions
TiO2 nanoparticles
CO2 curing
TGA

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