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Effect of recycled concrete powder on the rheological properties of cement paste: New findings
Cement and Concrete Composites ( IF 10.8 ) Pub Date : 2024-11-28 , DOI: 10.1016/j.cemconcomp.2024.105873
Tian Li, Rita Nogueira, Jorge de Brito, Paulina Faria, Jiaping Liu

Recycled concrete powder (RCP) influences cement paste's rheology, but the mechanisms remain unclear. This paper intends to fill this gap by employing a new method for measuring water absorption, the minimum water requirement method, an organic carbon analyser, and a laser particle size analyser. The cementitious material's water absorption (W), packing density (φm), water reducer adsorption (Qad), and particle size distribution are determined. Results show that, as the RCP's content increases from 0 % to 25 %, the cementitious material's W, φm, Qad, volume fraction, and average particle size increase by 21.7 %, 0.9 %, 26.2 %, 1.4 %, and 30.6 %, respectively. Consequently, the particle's surface covered by the water reducer (θ) and distance (H) decrease by 26.5 % and 32.6 %, respectively, resulting in an increase in the paste's yield stress (τ0) and plastic viscosity (ηpl) by 1946.6 % and 45.3 %, respectively. Based on an existing yield stress model, RCP affecting τ0 can be attributed to changes in the particle system's colloidal and contact interactions. A decrease in H increases colloidal interactions. Conversely, an increase in φm and a decrease in fine particle content reduce contact interactions. Colloidal interactions are more significant, thus τ0 increases. Based on the functional expression for the ηpl developed here, RCP affecting ηpl can be attributed to changes in hydrodynamic interactions and contact interactions. A decrease in H increases hydrodynamic interactions. An increase in φm combined with a decrease in fine particle content decrease contact interactions. Additionally, an increase in Qad reduces pore solution's viscosity. Hydrodynamic interactions are more significant, thus increasing ηpl.

中文翻译:


再生混凝土粉对水泥浆流变性能的影响:新发现



再生混凝土粉末 (RCP) 会影响水泥浆的流变性,但机制尚不清楚。本文旨在通过采用一种新的吸水率测量方法、最低需水量法、有机碳分析仪和激光粒度分析仪来填补这一空白。测定胶凝材料的吸水率 (W)、堆积密度 (φm)、减水剂吸附率 (Qad) 和粒度分布。结果表明,当 RCP 含量从 0 % 增加到 25 % 时,胶凝材料的 W、φm、Qad、体积分数和平均粒径分别增加了 21.7 %、0.9 %、26.2 %、1.4 % 和 30.6 %。因此,减水剂覆盖的颗粒表面 (θ) 和距离 (H) 分别减少了 26.5 % 和 32.6 %,导致浆料的屈服应力 (τ0) 和塑性粘度 (ηpl) 分别增加了 1946.6 % 和 45.3 %。根据现有的屈服应力模型,影响 τ0 的 RCP 可归因于颗粒系统的胶体和接触相互作用的变化。H 的减少会增加胶体相互作用。相反,φm 的增加和细颗粒含量的降低会减少接触相互作用。胶体相互作用更显著,因此 τ0 增加。根据此处开发的 ηpl 的功能表达,影响 ηpl 的 RCP 可归因于流体动力学相互作用和接触相互作用的变化。H 的减少增加了流体动力学相互作用。φm 的增加与细颗粒含量的降低相结合,减少了接触相互作用。此外,Qad 的增加会降低孔隙溶液的粘度。流体动力学相互作用更重要,因此增加了 ηpl。
更新日期:2024-11-28
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