Effects Of Seawater On The Compressive, Flexural And Split Tensile Strength Properties Of Reinforced Concrete

Background: Reinforced concrete is a heterogeneous mixture of cement, aggregates, potable water and steel used for various construction purposes, such as buildings, highways, bridges and water retaining structures. However, increase in subsea construction projects, especially in Nigerian coastal areas now warrant understanding the effects of seawater on reinforced concrete. Also, the increasing scarcity of freshwater in Nigerian coastal areas is now pushing construction workers to settle for saline water. Therefore, this study investigated the applicability of seawater as alternative to freshwater in concrete mixing and curing for construction, especially subsea construction activities, thereby addressing an existing research gap. Materials and Methods: The impacts of seawater were examined on the compressive, flexural and split tensile strengths of fresh and hardened concrete. Seawater samples from Suntan Beach, Badagry, Lagos State, were characterized at Central Research Laboratory of Bells University of Technology. Preliminary tests on cement and aggregates were conducted at Structures and Materials Laboratory of the same university. Production and curing of concrete specimens using both freshwater and seawater were done in four phases such as Freshwater (FF), Freshwater/Seawater (FS), Seawater/Freshwater (SF) and Seawater/Seawater (SS), with strength measurements conducted at 7, 14, and 28 days of curing respectively. Results: Seawater characterization results showed significant presence of salts and oxides. Slump test results showed seawater reduced workability of concrete compared with freshwater. Results of compressive and flexural tests at 28 days ranged between 19.26 and 20.74 Mpa (SS and SF), while split tensile values were 3.1 for FS and 5.1 Mpa SS respectively, at 28days. Conclusion: The study concludes that seawater negatively affected compressive and flexural strengths, but positively affected flexural strength. Therefore, admixtures which will protect compressive and flexural strengths are recommended when using seawater for construction