3 research outputs found
Shrinkage and Mitigation Strategies to Improve the Dimensional Stability of CaO-FeO<sub>x</sub>-Al<sub>2</sub>O<sub>3</sub>-SiO<sub>2</sub> Inorganic Polymers
No full textVolumetric stability is an important aspect of the performance of building materials, and the shrinkage of CaO-FeOx-Al2O3-SiO2-rich inorganic polymers (IPs) has not been thoroughly investigated yet. Hence, this paper describes the outcome of a study conducted to investigate ways to minimize their shrinkage using different curing regimes. Two different slags were used as case studies to assess the robustness of the developed mitigation strategies. IP pastes and mortars were cured at (i) room condition, (ii) in slightly elevated temperature (60 °C for 2 d) and (iii) in a water-saturated environment. The reaction kinetics and formed products were examined on IP pastes, while mortars were made to characterize the 28 d pore structure, autogenous shrinkage, drying shrinkage, and strength development. The results showed that the precursors' reactivity and curing conditions severely affect shrinkage mechanisms and magnitude. Volumetric changes in the plastic stage can be related to the precursors' reactivity but drying shrinkage was the driving mechanism affecting the volumetric stability of all IP mortars. Understanding the effect of a precursor's composition and curing conditions on shrinkage is fundamental to develop proper mitigation strategies and to overcome one of IPs' main technical drawbacks.sponsorship: This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 721185. G. Beersaerts would like to thank the support from the Center for Resource, Recovery, and Recycling (CR3). https://wp.wpi.edu/cr3/ (European Union|721185, Center for Resource, Recovery, and Recycling (CR3))status: Publishe
Modifying the pore size to minimise shrinkage by curing and using reactive and non-reactive additives in Fe-rich inorganic polymer mortars
No full textInorganic polymers (IPs) are binding materials that can be formed by alkali activating reactive Fe-rich slags; with mechanical properties comparable to those of Ordinary Portland Cement (OPC) based systems. However, IPs durability properties, such as shrinkage, is so far poorly investigated. Therefore, the current research focuses on determining the autogenous and drying shrinkage behaviour of Fe-rich IP mortars and its associated driving forces. IP were produced with an activating solution of a 1.7 SiO2/K2O molar ratio and 65 wt% H2O. IP mortars at ambient curing conditions exhibit an autogenous expansion and a high drying shrinkage, which must be reduced to avoid cracks and to meet durability criteria. In order to reduce the expansion and the drying shrinkage, 2-Methyl-2.4-Pentanediol (2M) and ground granulated blast furnace slag (GGBFS), were introduced to the mixture and sealed curing was performed at ambient or at an elevated temperature. The 2M additive reduces the drying shrinkage with 80% and modified the pore size distribution in such a way that a higher porosity was achieved, while the mechanical properties remained similar. Heat curing of IP mortars with 2M has no significant effect on the drying shrinkage. The introduction of GGBFS in IPs, cured at ambient conditions, had lower autogenous shrinkage but negatively affect the drying shrinkage due to the formation of a finer pore structure. Heat curing, on the other hand, reduces the drying shrinkage significantly and improves the mechanical properties considerably. Current research provides an insight in different pathways to reduce drying shrinkage while maintaining adequate mechanical properties
Immobilisation of uranium-contaminated liquid waste in an alkali-activated material (AAM) and subsequent leaching behaviour
No full textWe present a two-step procedure for treating contaminated liquid waste generated during the processing of uranium, specifically residual uranium-contaminated liquid after precipitation. After precipitating U(IV) as sodium diuranate under alkaline conditions, the resulting solution was solidified by immobilising it in an alkali-activated material. Static leaching tests indicated excellent material stability in water. Exposing the material to aggressive chemical conditions (nitric acid) resulted in slow and incomplete dissolution of uranium (and of structural elements) from a thin superficial layer with further passivation. Characterisation of the solid phase was performed to assess the stability of the alkali-activated material under the tested conditions.The authors would like to thank Sarah Nourry and Christophe Nourry for their support, Tobias Hertel and Yiannis Pontikes (SREMat) for their help in the production of the slag, Britta Bergfeldt for conducting the XRF measurements in the lab for bulk analysis at the Institute for Technical Chemistry KIT. This work was realised with the collaboration of the European Commission Joint Research Centre under the Collaborative Doctoral Partnership Agreement No 35342
