Peihua Zhong,Zhangli Hu,Michele Griffa,Mateusz Wyrzykowski,Jiaping Liu,Pietro Lura
This paper examines the mechanisms of desorption within cement pastes for superabsorbent polymers (SAP) with different sorption kinetics: retentive and non-retentive (self-releasing). Despite the different behavior in solution, both SAP types mitigated the autogenous shrinkage of cement pastes. 1 H NMR and X-ray tomography showed that the cavities formed by both SAP types were saturated until 9–11 h after mixing, while the entrained water in the cavities redistributed to the cement matrix afterwards. In particular, the non-retentive SAP might have rapidly released the absorbed water, but the released water stayed in the original cavities. Therefore, the behavior of the SAP in the pore solution may not completely determine their internal curing performance in cement pastes. In particular, the initial absorption that forms the solution-filled cavities might be more important than whether the SAP are able to retain the solution for extended periods of time or not.
Knowing the reactivity of recycled brick powder (RBP) is fundamental for its correct and efficient utilization. In this work, the dissolution behavior of RBP in NaOH solution and the degree of reaction in cement matrix were studied to investigate the reactivity of RBP. The results revealed that the main active species of RBP, Si and Al, showed obvious lasting dissolution with a significant non-steady state dissolution stage, indicating that the reaction proceeds slowly. The dissolution mechanism controlled by the phase boundary reaction, with activation energies of 82.74 kJ/mol and 75.79 kJ/mol for Si and Al dissolution, respectively, further confirmed this finding. The strength activity index, thermogravimetric analysis , selective dissolution, BSE-IA-Mapping and MAS NMR all confirmed reactivity of RBP. Additionally, reaction rims were observed around RBP particles in cement paste . The low Ca/Si and Ca/Al ratios and their significant increases in a direction from the particle boundary to the paste demonstrate that the rim was a hybrid phase composed of the original RBP components and the reaction products.
危险品化学品经营许可证（带存储）