This study explores ascorbic acid (AA) as a green, multipurpose admixture to improve the eco-efficiency of metakaolin (MK) blended cement mortar. The AA can be simply added into a mortar mix at a very small dosage to function as a hydration retarder, a water reducer, a strength enhancer, an autogenous shrinkage reducer, and a corrosion inhibitor for reinforcing bars. With four hydroxyl groups, AA can be adsorbed on the surface of cement particles, leading to slower hydration rate of cement and better dispersion of its hydration products. Both the porosity and small capillary pores of mortar are drastically reduced by the addition of AA. This leads to not only significant increase of compressive strength of MK blended cement mortar, but also significant reduction in the autogenous shrinkage. An accelerated corrosion test validated the corrosion resistance of reinforcing bar embedded in mortar by adding AA. This study broadens the range of molecules and polymers for interaction with cement and provides a new pathway for developing next the generation of chemical admixtures for concretes.

本研究探索抗坏血酸（AA）作为一种绿色、多用途外加剂，以提高偏高岭土（MK）混合水泥砂浆的生态效率。AA可以以非常小的剂量简单地添加到砂浆混合物中，作为缓水剂、减水剂、强度增强剂、自收缩减少剂和钢筋腐蚀抑制剂。AA具有四个羟基，可以吸附在水泥颗粒表面，从而减缓水泥的水化速度，使其水化产物分散得更好。AA的加入使砂浆的孔隙率和小毛细孔都大大减少。这不仅导致MK掺混水泥砂浆的抗压强度显着增加，而且自收缩也显着减少。加速腐蚀试验验证了添加AA的埋入砂浆中的钢筋的耐腐蚀性能。这项研究拓宽了与水泥相互作用的分子和聚合物的范围，并为开发下一代混凝土化学外加剂提供了新途径。