Sea sand (also known as Offshore or Marine Sand) has found application in coastal areas in many countries. In Asia, where coastal areas are rich in sea sand, sea sands are already in wide use in local concrete construction. These sands however have excess chlorides due to their deposition in saline water and hence need treatment before being used.
These sands are generally suitable for making concrete for base and sub-base and tests have shown that even reinforced concrete could be made from them. But the construction industry is extremely reluctant to accept it.
While sea sand has various advantages such as:
The main reasons why it is not acceptable for concrete making is the presence of sea shells and chloride content.
It has been argued that shell content has no adverse effect on the strength of concrete as such but the workability is reduced. Further investigations have shown that shells above 5mm does effect workability to some extent but those below 5mm show no significant reduction. In this context therefore sea sand is not prohibitive for concrete.
As regards chloride content there are various views and the standards also differ considerably on the extent of chlorides content in sea sand. It is however certain that chloride affects the durability of concrete structures by attacking the reinforcements and corroding it. Chloride in concrete could be from cement, aggregates, water and even from the admixture. It is the overall effect that is important and not the fine aggregate alone. Chloride content not only corrodes the reinforcements in concrete but also causes efflorescence due to oozing out of salts from the concrete. Hence chloride content needs to be controlled within limits.
CFlo wet processing systems through the process of wet sizing, attrition scrubbing, classification and washing can help reduce the chloride content to desirable levels. Our range of sea sand washing plants can treat sea sand for production of both concrete sand and plaster sand (depending on feed gradation) as per BS 882:1992 specification. Water recovery in the system is lower than usual, as a good part of the water needs to be rejected due to chloride build up. Chloride rich silt obtained post washing may be bagged and used as eco-friendly fertilizer and wastewater can be processed through Reverse Osmosis process before its release to the atmosphere.
