Effect of recycled powder on the yield stress of cement paste with varied superplasticizers  

作　　者：Zhen Li Cheng Yu Min Qiao Weixiao Xie Jinyao Yu 

机构地区：[1]Jiangsu Research Institute of Building Science CO.,Ltd.,Nanjing 210008,China [2]State Key Laboratory of High Performance Civil Engineering Materials,Jiangsu Sobute New Materials Co.,Ltd.,Nanjing 211103,China [3]School of Material Science and Engineering,Southeast University,Nanjing 211189,China

出　　处：《Low-carbon Materials and Green Construction》2023年第1期307-321,共15页低碳材料与绿色建造（英文）

基　　金：supported by a Youth Program of National Natural Science Foundation of China(Grant No:52008190).

摘　　要：The influence of superplasticizer on the yield stress of cement pastes with recycled powder(RP)was examined in the study.Four superplasticizers were used to obtain the similar fluidity by adjusting the dosage.The results show that the 10%RP decreases the yield stress of paste compared to the reference paste at the same fluidity,but 20%and 30%RP increases the yield stress,ranging from 11 to 599%.The superplasticizer with adsorptive group of phosphate-type minimizes the yield stress of paste than that of polycarboxylate-type,but it made a significant increment in yield stress as the incorporating of RP increased.Besides,the polycarboxylate superplasticizer with the higher molecular weight of side chain and charge density led to lower yield stress.Based on the Yodel model,the yield stress of paste with RP was analyzed by the polymer adsorption and particle packing density of particles to reveal the influence of RP with different superplasticizers on the colloidal interaction and contact network among the particles.The packing density of particles with recycled powder was a little higher than the reference paste,but the higher fraction of fine particles made a stronger PSD effect,which improved the particle contact interaction.On the other hand,due to the higher polymer adsorption of recycled powder than cement,especially for superplasticizer with phosphate group,the average surface coverage was increased,which extended the separation distance,so that colloidal interaction among particles was weaken.本文通过调整四种不同减水剂的掺量,研究在相近的流动度条件下,再生微粉对水泥浆体屈服应力的影响。结果表明:当再生微粉掺量为10%时,浆体的屈服应力低于基准浆体,但是当再生微粉掺量提高至20%和30%时,浆体的屈服应力高于基准浆体11%-599%。相对于羧酸基减水剂,膦酸基减水剂使浆体的屈服应力最低,但是随着再生微粉掺量的增加,浆体的屈服应力增幅明显增大。同时,在几种羧酸基减水剂中,具有更高分子量和电荷密度的侧链能适当降低浆体的屈服应力。将外加剂吸附和颗粒堆积密度数据代入Yodel模型中,分析不同减水剂作用下,水泥与再生微粉复掺体系中胶体相互作用和颗粒“接触”相互作用的变化,以此揭示再生微粉对浆体屈服应力的影响机制。虽然再生微粉掺入略微增加了堆积密度,但是由于再生微粉粒径分布中细颗粒的比例较高,使颗粒的PSD效应显著增强,即接触颗粒的数量和有效体积分数有所提高,由此增加了颗粒与接触的相互作用。另一方面,减水剂掺量的增加,提高了颗粒的平均表面覆盖率,增加了平均表面到表面的分离距离,显著削弱了胶体间相互作用,比较之下膦酸基减水剂的削弱效果更为明显。

关 键 词：Recycled powder Yield stress SUPERPLASTICIZER Polymer adsorption Packing density 

分 类 号：O64[理学—物理化学]