# Carbon Dioxide Uptake by Brazilian Cement-Based Materials
## 1 Introduction
### General Background on the Carbonation as a Stage in the Decarbonization Roadmaps
In particular, [PERSON] and [PERSON] [15] modeled the effects of climate change on the porosity of Portland cement paste. [PERSON] et al. [16] found that the carbon dioxide uptake per mass of cement paste reached 22-26% after a 28-day carbon dioxide curing. Also, the total porosity decreased as a result of the reduction in the pores volume with diameters less than 50 nm. [PERSON] et al. [17] found promising results in the cement paste powder generated in the recycling process of concrete, which is a material composed mainly of hydrated cement, and was subjected to carbonation. [PERSON] et al. [18] found that the addition of polypropylene fibers enhanced the CO2 uptake of cement-based materials subjected to the CO2-curing process. According to [PERSON] et al. [19], the use of eggshell powder added to the Portland cement under carbonation-curing conditions improved the mechanical characteristics and durability of the cement-based materials. Furthermore, [PERSON] and [PERSON] [20] reported that the use of biochar with LC3 binders could enhance the environmental benefits of Portland cement. [PERSON] et al. [21] assessed the impact of cement kiln dust (CKD) on the carbon dioxide uptake of concrete. Two CKDs with different fineness were used as a cement constituent (0-60%) in two mortar mixes (water/binder ratios of 0.5 and 0.425). Mortar specimens were subjected to accelerated carbonation curing for 12 h. The global carbon dioxide uptake in CKD mixes was less than those of the control mixes. However, the relative carbon dioxide uptake, given as a percentage of the cement content, was higher in mixes made with the finer CKD at the higher water/binder ratio. Accordingly, it was concluded that the replacement of cement by CKD promoted a reduction in the carbon dioxide uptake of mortars. [PERSON] et al. [22] studied the effect of accelerated carbonation on the properties of precast concretes made with natural and recycled aggregates. Natural aggregates were replaced by recycled aggregates and two carbonation conditions were used: accelerated carbonation (5% CO\({}_{2}\)) and natural carbonation (atmospheric carbon dioxide). The accelerated carbonation increased the density, the compressive strength, and the carbon dioxide capture, which was 525% higher compared to curing under natural carbonation. Therefore, carbon curing is a promising technology to mitigate the effects of climate change. Consequently, the effective CO\({}_{2}\) sink process of precast concrete elements was suggested. [PERSON] et al. [23] evaluated the carbon dioxide uptake of the U.S. pavement network for 30 years (2020-2050) during its use and end-of-life stage. Their study showed that 5.8 million tons of carbon dioxide can be taken up by concrete pavements in the U.S. Furthermore, stockpiling the crushed concrete at the end-of-life period could raise the carbon uptake to 11.8 million tons for 30 years (2020-2050). Therefore, concrete stockpiling is a cost-effective method of carbon dioxide abatement ($25-$100/ton of carbon dioxide). By contrast, [PERSON] et al. [24] forgot the beneficial effect of concrete carbonation and albedo in their critical review on carbon-neutral cities. In the target category of \"built environment and community structure\", the use of recycled materials in infrastructure is mentioned as an action. Nevertheless, in the target category of \"carbon sinks, sequestration and biodiversity\", the authors included \"Increasing carbon stock of forest and other green areas in city area\", but omitted the reference to the high albedo of the concrete pavements, which has been studied extensively in several cities [25; 26], and also did not discuss concrete carbonation. Since cities have geographically bounded areas, which restrict the potential for development of land-based carbon sequestration, a more significant role for other types of carbon dioxide uptake is expected, such as the use of some carbonatable cement-based materials. Furthermore, the use of materials of high albedo in buildings and pavements should be taken into account.