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Carbonation-cementation of recycled hardened cement paste powder

机译：再生硬化水泥浆粉的碳化-胶结

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Well-hydrated cement paste powder was prepared to imitate recycled hardened cement paste powder. Compacted blocks were formed with the powder, and subjected to carbonation at different CO2 pressures. The effects of water/powder (w/p) ratio and compacting pressure in block preparation, and the CO2 pressure on the carbonation degree and compressive strength of the carbonated blocks were studied. The mineral compositions, microstructures and pore structures of the carbonated blocks were analyzed by XRD, SEM and MIP. The results show that the hardened cement paste powder in the blocks is able to re-cement and produce high level strength by carbonation. In the CO2 pressure range of 0.050-0.40 MPa, the higher the CO2 pressure was, the higher the carbonation degree and compressive strength of the blocks at all the carbonation times. Carbonated blocks with the compressive strength as high as 62.6 MPa were prepared by carbonation in 0.4 MPa CO2 for 24 h. The calcium hydroxide, calcium silicate hydrates and the un-hydrated beta-C2S in the hardened cement paste powder were almost fully carbonated in 24 h. There was no new well-crystallized mineral other than the three polymorphs of calcium carbonate, mainly calcite, formed during the carbonation. The microstructures became more compacted due to the filling of the pores by CaCO3 and the other carbonation products such as low calcium silicate hydrates, companied with the decrease of the porosity and the pore sizes. (C) 2018 Published by Elsevier Ltd.
机译：制备水合良好的水泥浆粉以模仿回收的硬化水泥浆粉。用粉末形成压实的块，并在不同的CO 2压力下进行碳化。研究了水/粉（w / p）比和压实压力在砌块制备中的影响，以及CO2压力对碳酸化砌块碳化程度和抗压强度的影响。用XRD，SEM和MIP分析了碳酸盐岩块体的矿物组成，微观结构和孔隙结构。结果表明，砌块中的硬化水泥浆粉能够通过碳化作用重新粘结并产生高水平强度。在0.050-0.40 MPa的CO2压力范围内，CO2压力越高，在所有碳化时间段的碳化程度和抗压强度越高。通过在0.4 MPa的CO2中碳化24 h，制备抗压强度高达62.6 MPa的碳化块。硬化水泥浆粉中的氢氧化钙，硅酸钙水合物和未水合的β-C2S在24小时内几乎完全被碳酸化。除了在碳酸化过程中形成的碳酸钙的三种多晶型物（主要为方解石）以外，没有新的结晶良好的矿物。由于CaCO3和其他碳酸化产物（如低硅酸钙水合物）填充了孔隙，同时孔隙率和孔径减小，因此微观结构变得更加致密。 （C）2018由Elsevier Ltd.发布

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