Effect of Seawater as Mixing Water on the Mechanical Properties of Mortar and Concrete

Seawater can be used as mixing water and curing water. Although the setting time of cement increased by using seawater, however, it did not significantly affect the mechanical properties of mortar and concrete. In addition, strength of mortar and concrete increase when using seawater as mixing water.One of the requirements in making concrete (both structural and non-structural) is fresh water. However, the data of United Nations and WMO (World Meteorology Organization) predicted around 5 billion people will be in a lack of fresh water at the end of 2025. Hence, the use of fresh water only for primary needs. And it is important for the world of concrete construction to seriously study the possibility of sea water as mixing water in making concrete (hereinafter called seawater concrete) which can minimize usage of fresh water and help the areas that have difficulty fresh water to accelerate development infrastructure by using concrete material. On the other hand, concrete is exposed to seawater will experience some chemical and physical action, such as chemical attack, corrosion of reinforcing bars induced by chloride, etc. The presence and intensity of various forms of chemical and physical attack depend on the location of the concrete to the sea level. The chemical action of seawater on the concrete arises from the fact that seawater contains a number dissolved salts. Some research revealed that mixing concrete using seawater can increase the compressive strength compared to using fresh water. A very interesting phenomenon to be studied experimentally using local materials and cement containing fly ash and slag which is a by-product, so it has indirectly participated maintain the ecosystem and reducing CO2 emissions. A series testing and analysis of qualitative and quantitative was conducted to evaluate the mechanical properties of seawater concrete. This study aims to examine and analyze the feasibility of seawater as mixing water for making concrete, especially for non-structural concrete. \ud The results showed that seawater can be used as mixing water and curing water. Although the setting time of cement become longer by using seawater, however, it did not significantly affect the mechanical properties of mortar and concrete. In addition, strength of mortar and concrete increase when using seawater as mixing water