Strength and durability of marine cement-based mortar modified by colloidal nano-silica with epoxy silane for low CO2 emission

The heavy use of marine concrete consumes a large amount of cement increasing CO2 emission. Improving the strength and durability of marine concrete is an effective strategy to reduce CO2 emission. This study aimed to introduce colloidal nano-silica (CNS) and epoxy silane modified colloidal nano-silica (M-CNS) to improve the mechanical performance and durability of High Sulfate Resistance Portland cement. Meanwhile, the CNS and M-CNS were incorporated to marine cement mortar, and the aggregation of CNS, and the hydration mechanism and micro-mechanism of the mortar were investigated. The results indicated that the workability, mechanical properties and durability of marine cement samples were enhanced with M-CNS addition. When adding 1 wt% M-CNS with grafting rate of 15% (M-CNS1), the chloride diffusion coefficient was reduced by 9.49% and the porosity was reduced by 18.84%. In addition, the compressive strength of cement mortar with M-CNS1 increased by 10.42%, 28.71% and 10.49% compared with blank specimens after curing for 3-, 7- and 28-days. The improvements in strength and durability indicate that M-CNS has a promising application for reducing CO2 emissions by marine concrete industry.