Strength and corrosion behavior of mortar mixed and/or cured with seawater with various fly ash replacement ratios

• Main Authors: Lim, Edralin D., Roxas, Cheryl Lynne C., Gallardo, Ronaldo S., Nishida, Takahiro, Otsuki, Nobuaki
• Format: text
• Published: Animo Repository 2015
• Subjects: Mortar—Additives; Fly ash; Seawater; Civil Engineering
• Online Access: https://animorepository.dlsu.edu.ph/faculty_research/3060
• Institution: De La Salle University

The construction industry is one of the largest consumers of freshwater. Ordinary mortar mix requires clean freshwater, a resource which is expected to vastly deplete as a result of global water scarcity. Therefore, the need for an abundant alternative source is necessary-seawater. With this method, not only the environmental issues are addressed, but also the economical aspect of construction projects. Utilization of readily available materials without the need of production or treatment, such as the seawater, would greatly contribute into preventing freshwater scarcity around the world. But the high chloride content of seawater may accelerate corrosion in reinforced concrete structures. Adding reactive inorganic materials like fly ash improves the resistance against chloride penetration. However, the influence of various fly ash replacement ratios on reinforced mortar mixed with seawater needs further studies to determine applicability in the construction industry. This study reports the results of using seawater as mixing and curing water and different fly ash replacement ratios on the properties of reinforced mortars. The compressive strength, corrosion potential, corrosion current density and chloride content were the key means of measurement in determining the effects of seawater. Mortar specimens with 0%, 10%, 20%, 30%, 40%, and 50% fly ash replacement ratios and ordinary Portland cement mixed and cured with seawater and freshwater were prepared. Cylindrical specimens were prepared for compressive strength while rectangular prism specimens of size 4 cm x 4 cm x 16 cm were used for corrosion monitoring. Ten millimeter in diameter round steel bars were suspended in the specimens with constant cover of 5 mm in order to accelerate the corrosion process. In addition, the 20% fly ash replacement specimens were also cured in seawater using full immersion or wet burlaps. Results show that using seawater as mixing water can produce comparable compressive strength as freshwater especially when cured for longer periods. A fly ash replacement ratio of 20%-30% can result to favorable strength values. In terms of corrosion, seawater mixed specimens did not yield a higher corrosion rate so long as it is cured with freshwater at longer curing period. In terms of curing processes, the use of wet burlaps can help achieve high compressive strength, low corrosion potential and low corrosion rate as it resulted to the lowest chloride content among the seawater mixed specimens.