Nano-silica (NS) and micro-silica (MS) are both effective in improving the strength and durability of concrete, but their combined effect on a particular performance attribute may not be the same as the sum of their respective individual effects. In this research, the individual and combined effects of NS and MS on the carbonation and sorptivity of concrete were studied by conducting carbonation and water absorption tests of concrete mixes with different cement, NS, MS and water contents, and SEM imaging of the microstructural changes due to the addition of NS and/or MS. Then, the cementing efficiencies of NS and MS in carbonation resistance and sorptivity were assessed in terms of cementing efficiency factors (CEFs). It was found that the CEFs of NS were higher than those of MS, and, more importantly, were at least 48% higher when co-added with MS due to microstructure densification arising from the successive filling of voids by the superfine MS and then the ultrafine NS. Hence, for improving the durability of concrete, it is better to co-add NS and MS so as to exploit their synergistic effects.

纳米二氧化硅（NS）和微二氧化硅（MS）均可有效提高混凝土的强度和耐久性，但它们对特定性能属性的综合作用可能与各自作用的总和不同。在这项研究中，通过进行不同水泥，NS，MS和水含量的混凝土混合物的碳化和吸水率测试以及微观结构变化的SEM成像，研究了NS和MS对混凝土碳化和吸水性的单独和联合作用。由于添加了NS和/或MS。然后，根据固井效率因子（CEF）评估了NS和MS在抗碳化性和吸附性方面的固井效率。发现NS的CEF高于MS的CEF，更重要的是，当与MS共同添加时，由于超细MS和超细NS依次填充空隙而引起的微观结构致密化，因此它们至少高48％。因此，为了提高混凝土的耐久性，最好共同加入NS和MS，以发挥它们的协同作用。