Natural rubber latex grafted with polyacrylamide (NRL-g-PAM) was employed as the cement admixture for cement pastes. During the preparation of cement pastes, adding NRL-g-PAM improved the homogeneity of freshly prepared cement pastes compared to unmodified NRL. The presence of NRL retarded the hydration of cement, and the retardation was more pronounced with increasing NRL content in the cement pastes. However, the chemical structures of the hydration cement pastes remained unaffected by the presence of natural rubber (NR). Scanning electron microscope (SEM) images of NRL-g-PAM-modified cement pastes revealed the formation of polymeric films in the cement matrix. Beneficially, the polymeric film of NR in the cement pastes enhanced the toughness due to the effective energy absorption of an elastomeric NR. Compared with unmodified cement paste, adding NR-g-PAM improved the flexural strength, which arises from enhanced rubber-cement matrix bonding to compensate for a reduction of cement bonding and cementitious products.

中文翻译：

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以聚丙烯酰胺接枝的天然橡胶乳胶作为水泥外加剂，提高水泥浆的弯曲强度和韧性


聚丙烯酰胺接枝的天然橡胶胶乳 （NRL-g-PAM） 被用作水泥浆的水泥外加剂。在水泥浆的制备过程中，与未改性的 NRL 相比，添加 NRL-g-PAM 改善了新鲜制备的水泥浆的均匀性。NRL 的存在延缓了水泥的水化，并且随着水泥浆中 NRL 含量的增加，这种延迟更为明显。然而，水化水泥浆的化学结构不受天然橡胶 （NR） 存在的影响。NRL-g-PAM 改性水泥浆的扫描电子显微镜 （SEM） 图像揭示了水泥基体中聚合物膜的形成。有益的是，由于弹性体 NR 的有效能量吸收，水泥浆中的 NR 聚合物膜增强了韧性。与未改性的水泥浆相比，添加 NR-g-PAM 提高了弯曲强度，这是由于增强了橡胶-水泥基体粘合而产生的，以补偿水泥粘合和胶凝产品的减少。