Cementitious materials are well acknowledged as one of the most adaptable materials for immobilizing heavy metals. Belite calcium sulfoaluminate cement (BCSA), one of the low-carbon alternative binders to cement with superior properties regarding chemical resistance and mechanical properties, is found with a desirable capability for waste immobilization. In this study, BCSA was used for Co(II) immobilization with a dosage of up to 2.5% by weight of BCSA. The results showed that Co(II) could promote the hydration of BCSA pastes, specifically accelerated the hydration of ye'elimite. More hydration products could be generated in the Co(II)-doped BCSA pastes, leading to the construction of a denser microstructure. The compressive strength of BCSA pastes would be slightly improved when BCSA was used for Co(II) immobilization, and the electrical resistivity would decrease. In terms of Co(II) immobilization, BCSA cement exhibited a desirable capacity for Co(II) immobilization. The majority of the Co(II) could be immobilized within the first 100 min of mixing BCSA with Co(II) solutions. The immobilization degrees of Co(II) in hardened BCSA pastes could approach about 99.99% after 7d. The acquired results indicated that BCSA cement is effective for Co(II) immobilization. Therefore, BCSA has a low-carbon advantage with superior strength development over time and prospective capacity of heavy metals immobilization.

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As an industrial by-product containing pozzolanic components, recycled ferronickel slag (FNS) has the potential to be supplementary cementitious materials (SCMs) to reduce the massive carbon footprint of the cement industry, however, the main limitation of ferronickel slag as SCMs is the low hydration rate at an early age. In this study, the pozzolanic activity property results indicate that if the proportion is more than 10 %, FSN can hardly participate in the cement hydration reaction during the early stage, even the mechanical strength of FNS-mortar decreases obviously with the higher proportion of ferronickel slag. Therefore, mechanical grinding and steam curing at an early age are applied to promote the reaction activity of the recycled ferronickel slag tailing in this study. Compared with standard curing, the compressive strength of hardened FNS-cement paste with steam curing at 60 °C or 80 °C increased by 8.2 % or 33.8 %, and the connected porosity decreased by 18.9 % or 17.3 %. And MgO in the ferronickel slag exists as Mg₂SiO₄ in raw materials and enters the C-S-H gel with the formation of M-S-H gel during the secondary hydration stage. This study provides a theoretical basis for solid waste-based concrete and promotes the recycling, conservation, and resources of solid waste in building materials.

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In this study, the impact of water-to-cement (w/c) ratios of belite calcium sulfoaluminate cement (BCSA) on the hydration kinetics and the electrochemical impedance spectroscopy (EIS) parameters is studied. According to the analysis of classic hydration measurements, such as calorimetry tests, chemical shrinkage content, and chemically bound water content, it can be concluded that a higher w/c ratio clearly accelerates the hydration of BCSA cement paste. The electrical resistivity of BCSA0.35 cement paste is more than 4.5 times that of BCSA0.45 and BCSA0.5, due to the gradually densified micropore structure blocking the electrical signal transmission rather than the free charged-ion content. The porosity of BCSA0.5 is 27.5% higher than that of BCSA0.35 and 7.8% higher than that of BCSA0.45, which proves the resistivity is clearly related to the variation in microstructure, especially for the porosity and pore size distribution. The novelty of this study is the linear regression with logarithm terms of electrical resistivity and classic hydration parameters such as chemical shrinkage, cumulative hydration heat, and chemically bound water is established to extend the classical expression of cement hydration degree. It indicates that the electrochemical impedance spectroscopy can be taken as a nondestructive testing measurement to real-time monitor the cement hydration process of cement-based materials.@en

This publication presents the results of a design lab that explores landscape-based design approaches for adaptive urban transformation in fast urbanizing deltas. While using design as a research strategy landscape architecture principles are explored that ensure water safety and inclusive socio-ecological design. The projects as presented here explore water resilient industrial transformation, flood protection, socio-spatial integration and the reintegration of urban villages in the Pearl River Delta. There are also two sheer projects with similar approach applied in Beijing and Jakarta. This lab is connected to the NWO-NSFC-EPSRC funded project ‘Adaptive Urban Transformation’ and a collaboration of Delft University of Technology, South China University of Technology and The University of Sheffield. The lab contributes to the project with design workshop participation, MSc-thesis and publications. www.adaptiveurbantransformation.com@en