Current research on recycled concrete powder (RCP) influencing the cement-based material's rheology primarily focuses on the initial rheology, with limited attention given to long-term rheology (rest time over 60 min). This work investigates RCP influencing the paste's static yield stress evolving with time (10–120 min). Results show that RCP significantly influences the cement paste's static yield stress, increasing it by about 89 times when the incorporation ratio of RCP reaches 25 % and rest time extends to 120 min. According to existing theoretical foundations and models, it is believed that the underlying influencing mechanisms can be elaborated from three aspects: the cementitious particle system's colloidal and contact interactions and the cementitious paste's structural build-up rate. RCP improves the particle system's capacity to adsorb polycarboxylate ether (PCE), lowering the average coverage ratio of the particle surface coated by PCE and the separation distance between particles, thus increasing the initial colloidal interactions. This promotes flocculation and strengthens the colloidal network, raising the paste's static yield stress; RCP increases the particle system's average size, volume fraction, packing density, and hydration degree and decreases particle number and hydrated volume, thus affecting the contact interactions evolution over time. However, the highest incorporation ratio does not result in the highest contact interactions; RCP promotes the paste's early hydration, generating more stable C-S-H. This accelerates the connections between the particles transition from flexible colloidal to rigid bridging, increasing the paste's structural build-up rate, thus raising the linear growth rate of the paste's static yield stress.

中文翻译：

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再生混凝土粉对水泥浆体静屈服应力演变的影响

目前对再生混凝土粉末 （RCP） 影响水泥基材料流变学的研究主要集中在初始流变学上，而对长期流变学（休息时间超过 60 分钟）的关注有限。这项工作研究了 RCP 对浆料静态屈服应力随时间（10-120 分钟）演变的影响。结果表明：RCP 对水泥浆的静态屈服应力有显著影响，当 RCP 掺入率达到 25 %且静置时间延长至 120 min 时，RCP 的静态屈服应力增加了约 89 倍。根据现有的理论基础和模型，认为其影响机制可以从水泥基颗粒体系的胶体和接触相互作用以及水泥基浆体的结构堆积速率三个方面进行阐述。RCP 提高了颗粒系统吸附聚羧酸醚 （PCE） 的能力，降低了 PCE 包被的颗粒表面的平均覆盖率和颗粒之间的分离距离，从而增加了初始胶体相互作用。这促进了絮凝并加强了胶体网络，从而提高了浆料的静态屈服应力;RCP 增加了颗粒系统的平均尺寸、体积分数、堆积密度和水合度，并减少了颗粒数量和水合体积，从而影响了接触相互作用随时间的演变。但是，最高的合并率并不会导致最高的联系人交互;RCP 促进糊状物的早期水合作用，产生更稳定的 CSH。这加速了颗粒之间的连接从柔性胶体过渡到刚性桥接，增加了浆料的结构堆积速率，从而提高了浆料静态屈服应力的线性增长率。