Sustainable seawater-sea sand concrete incorporating metakaolin, micro-silica, and nano-silica: mechanical-durability performance and life cycle assessment

Abstract

The utilization of seawater and sea sand (SWSS) in concrete production offers sustainable alternatives to depleting freshwater and river sand resources, yet elevated chloride content compromises durability and limits widespread adoption. This study systematically evaluates the mechanical properties, durability characteristics, and environmental impacts of SWSS concrete incorporating metakaolin, micro-silica, and nano-silica at 7.5 % cement replacement. Five concrete mixtures were fabricated and assessed through compressive strength testing at 7, 14, 28, and 91 days, alongside tensile strength, water absorption, rapid chloride permeability, and electrical resistivity measurements at 91 days. Cradle-to-gate life cycle assessment quantified environmental burdens across multiple impact categories. Results demonstrated that supplementary cementitious materials (SCMs) substantially enhanced performance of SWSS concretes, with 7.5 % nano-silica incorporated concrete achieved maximum compressive strength of 93.9 MPa, while 7.5 % micro-silica incorporated SWSS concrete exhibited lowest chloride permeability of 413 coulombs. Environmental analysis revealed 7.5 % micro-silica SWSS concrete achieved optimal sustainability with 10.1 % global warming potential reduction (346.8 kg CO ₂ -eq/m ³ ) relative to control concrete (385.7 kg CO ₂ -eq/m ³ ), while 7.5 % nano-silica incorporated SWSS concrete demonstrated superior mechanical-durability performance but elevated environmental impact. These findings indicate, strategic SCMs incorporation produces high-perormance, environmentally-efficient concrete that exceeds traditional benchmarks for marine applications.