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The use of recycled aggregate obtained from the crushing of construction solid waste can not only save natural sand and gravel resources, but also promote the recycling of construction solid waste. The quality of recycled aggregate determines the performance of recycled aggregate concrete. There are many factors affecting the quality of recycled aggregate, and the strength of parent concrete is one of the important influencing factors. The article takes strength of parent concrete as the research object, and summarizes its influence law on the properties of recycled aggregate and recycled aggregate concrete. Different strengths of parent concrete affect the quality and content of recycled aggregate adhesive mortar, which in turn affects the properties of recycled aggregate and recycled aggregate concrete. When the strength of parent concrete increases, the quality and content of adhesive mortar are improved. While the quality of adhesive mortar is improved, the properties of recycled aggregate and recycled aggregate concrete are strengthened. The increase in the content of adhesive mortar deteriorates the physical properties of recycled aggregate, increases the porosity and water absorption of recycled aggregate, but strengthens the internal curing effect of concrete, which contributes to the mechanical properties of recycled aggregate concrete. Using microscopic analysis, it is found that different strength of parent concrete make a difference in the content of hydration products in the interfacial transition zone of recycled aggregate concrete, which has an impact on the mechanical properties of concrete. The article provides a theoretical basis for further grading and utilization of recycled aggregate. [ABSTRACT FROM AUTHOR]

In this study, we synthesized two new two-dimensional (2D) covalent organic frameworks (COFs), COF-TA and COF-DP, by combining 4-connected D2h-symmetric and 2-connected non-centrosymmetric C2-symmetric building blocks. Unlike the typical sql topology, these COFs exhibit an unconventional kgm topology characterized by a favorable anti-parallel stacking arrangement, which results in a lower energy configuration. Notably, COF-DP, with its unique D–A–D structural motif and photosensitive properties, demonstrates a narrow band gap and excellent photothermal conversion capabilities, making it a promising material for photothermal imaging applications. [ABSTRACT FROM AUTHOR]

Nano-SiO2 (NS) is widely used in cement-based materials due to its excellent physical properties. To study the influence of NS content on a cement paste and the interfacial transition zone (ITZ), cement paste samples containing nano content ranging from 0 to 2% (by weight of cement) were prepared, and digital image correlation (DIC) technology was applied to test the mechanical properties. Finally, the optimal NS content was obtained with statistical analysis. The mini-slump cone test showed that, with the help of superplasticizer and ultrasonic treatment, the flowability decreased continuously, as the NS content increased. The DIC experimental results showed that NS could effectively improve the mechanical properties of the cement paste and the ITZ. Specifically, at the content level of 1%, the elastic modulus of cement paste and ITZ was 20.95 GPa and 3.20 GPa, respectively. When compared to that without nanomaterials, the increased amplitude was 73.50% and 90.50%, respectively. However, with the further increase in NS content, the mechanical properties decreased, which was mainly caused by the agglomeration of nanomaterials. Additionally, the NS content did not exhibit a significant effect on the thickness of the ITZ, and its value was maintained at 76.91–91.38 μm. SEM confirmed that NS would enhance the microstructure of both cement paste and ITZ. [ABSTRACT FROM AUTHOR]