The properties of the ordinary Portland cement (OPC) mortar having a water–cement (w/c) proportion of 0.450 and cement/sand ratio of 1:2 are altered by replacing cement with 25% fly ash and adding 2% colloidal nanosilica separately and in a combined form. The changes were studied experimentally. Cured specimens at different ages were subjected to compressive strength test, split tensile test, and durability tests such as sorptivity, water absorption, and chloride penetration. The impact of the addition of colloidal nanosilica on the permeability of the mortar matrix, estimated by the coefficient of absorptivity, was computed by performing a water absorption test for 60 min. It was observed that in the initial curing regime, fly ash expansion causes a decrease in strength and an increase in water permeability. The addition of 2% colloidal nanosilica proves to be advantageous in the hardened OPC and fly ash mortar as it increases the materials characteristic strength by conferring it a dense microstructure. Nanosilica in the cement matrix with and without fly ash assists the rapid growth of hydrated products by creating additional nucleation sites and improving the durability properties of the material as anodic polarization decreases under impressed voltage. The microstructure was analyzed by SEM and found to have the refinement of a pore structure and densification of binding gels in the colloidal nanosilica -incorporated samples.

水灰比（w / c）为0.450，水泥/砂比为1：2的普通波特兰水泥（OPC）砂浆的性能可以通过用25％的粉煤灰代替水泥并分别添加2％的胶体纳米二氧化硅来改变并结合在一起。通过实验研究了这些变化。对不同年龄的固化样​​品进行抗压强度测试，劈裂拉伸测试以及耐久性测试，如吸水性，吸水率和氯化物渗透率。通过进行60分钟的吸水率测试，计算了通过吸收系数估算的胶体纳米二氧化硅的添加对砂浆基体渗透性的影响。观察到，在初始固化过程中，粉煤灰膨胀导致强度降低和透水性增加。事实证明，添加2％的胶体纳米二氧化硅在硬化的OPC和粉煤灰砂浆中是有利的，因为它通过赋予其致密的微观结构来提高材料的特征强度。具有和不具有粉煤灰的水泥基体中的纳米二氧化硅可通过产生额外的成核位点，并随着阳极极化在施加电压下降低而改善材料的耐久性能，从而帮助水合产物快速生长。通过SEM分析微观结构，发现在掺有胶体纳米二氧化硅的样品中具有细孔结构的细化和结合凝胶的致密化。具有和不具有粉煤灰的水泥基体中的纳米二氧化硅可通过产生附加的成核位点，并随着阳极极化在施加电压下降低而改善材料的耐久性能，从而帮助水合产物快速生长。通过SEM分析微观结构，发现在掺有胶体纳米二氧化硅的样品中具有细孔结构的细化和结合凝胶的致密化。具有和不具有粉煤灰的水泥基体中的纳米二氧化硅可通过产生附加的成核位点，并随着阳极极化在施加电压下降低而改善材料的耐久性能，从而帮助水合产物快速生长。通过SEM分析微观结构，发现在掺有胶体纳米二氧化硅的样品中具有细孔结构的细化和结合凝胶的致密化。