Fresh water makes up a very small fraction of total available water in earth. One major challenge for marine infrastructure is the shortage of fresh water for making concrete. To save fresh water, sea water can be used for mixing in concrete.

This study focuses on the mechanism and microstructure characteristics of seawater based cementitious system. Firstly, the early age properties and mechanism of seawater cement paste samples was investigated. The seawater samples showed faster setting time and increased hydration rate. Rate of increase of hydration increases the dispersion of particles from cement increasing the hydration product formation. Molecular dynamics simulation was performed on C(N)ASH gel to, study the interactions of sodium and calcium atom in gel system.

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Fresh water makes up a very small fraction of total available water in earth. One major challenge for marine infrastructure is the shortage of fresh water for making concrete. To save fresh water, sea water can be used for mixing in concrete.

This study focuses on the mechanism and microstructure characteristics of seawater based cementitious system. Firstly, the early age properties and mechanism of seawater cement paste samples was investigated. The seawater samples showed faster setting time and increased hydration rate. Rate of increase of hydration increases the dispersion of particles from cement increasing the hydration product formation. Molecular dynamics simulation was performed on C(N)ASH gel to, study the interactions of sodium and calcium atom in gel system.

Secondly, the properties of seawater cement paste samples are investigated. Different samples made with different percent of salt and pozzolans are tested for compressive strength properties, thermal loss, X-ray diffractogram crystals and microstructures & morphology. ²⁹ Si and ²⁷Al NMR test was conducted on seawater cement paste samples to know the structure and atomic co-ordination of the seawater system. The study revealed that seawater cementitious system has no peaks of Q⁴ and Q³ and Al is present in tetrahedral and octahedral co-ordination.

Thirdly, the durability of pozzolans seawater system was investigated by storing the samples in corrosive solutions for 6 months. Based on the observations, seawater samples made with slag and fly ash binders showed superior performance in corrosive solution. The LC2 sample suffered the maximum weight loss of 13.5% in sulphate solution. The properties of seawater samples improved when pozzolans were added to the system.

Lastly, studies were performed on geopolymer seawater cementitious system. The performance of geopolymer in seawater was comparatively better. But the samples were affected by excessive carbonation, which was also the case for Portland cement samples made with seawater.

In conclusion, seawater can be used for making concrete only in the case when freshwater is not available. Future and further studies should be carried on diffusion mechanism and transportation properties of these system.