Mechanical properties and environmental performance of seawater sea-sand self-compacting Concrete

Due to the constituted ingredients are both rich in reserves, seawater sea-sand self-compacting concrete (SWSS-SCC) today has been treated as an ideal material in constructing island and coastal structures. The technique feasibility of applying SWSS-SCC in real engineering has been recognized by investigating the material properties, but its environmental impacts (EIs) has rarely been concerned at current stage. Under such a background, a refined life cycle assessment model of SWSS-SCC was developed in this study based on the China’s latest production data. Life cycle phases considered include extracting and preparing raw materials, component material production, mixing concrete and transportation occurred in the whole processes. After verifying the model, the impacts of several factors like concrete curing method, fly ash incorporation content, sea-sand transportation distance and electricity generation approach, which have never been investigated before, on the energy cost and carbon dioxide equivalent emissions generated in manufacturing SWSS-SCC were discussed. The simulated results showed that: (a) Using seawater and sea-sand slightly increases the concrete’s compressive and tensile strengths. Replacing some cement with fly ash notably decreases the early-age strengths, but curing at 60°C can offset that effect. (b) Replacing fresh water and natural sand by sea-water and sand in Humen Town decreases the production EIs of SWSS-SCC. For this concrete, cement production and raw material transportation are the main contributors to the overall EIs. (c) During producing SWSS-SCC, using electricity generated from clean fuels can effectively reduce the system’s EI, but changing fuel used to fire the cement kiln has little effect. (d) High temperature curing to increase the fly ash content is not environmentally sound. Reducing the mixture’s water to binder ratio is more benefit for incorporating fly ash. (e) From an environmental evaluation view, applying SWSS-SCC is more ecological in island constructions than coastal buildings.