PERFORMANCE EVALUATION OF FIBER-REINFORCED CONCRETE USING SEAWATER CURING AND PARTIAL SEA SAND REPLACEMENT

Abstract

The growing loss of fresh water and river sands used as aggregate materials for concrete is an increasing environmental problem, especially in coastal areas that have abundant unexploited marine resources. Though several earlier studies have evaluated seawater concrete, replacing river sands with sea sand, and fiber reinforced concrete, very little previous research has evaluated the combined impact of seawater curing, partial replacement of river sand with sea sand, and the addition of glass, steel and carbon fibers to evaluate the overall performance of fiber reinforced concrete made with seawater curing and 20 percent replacement of river sand with sea sand, at a constant fiber content (volume fraction) of 1%, and a target compressive strength of 40 MPa. Eight concrete mixtures were tested for compressive strength (strength when under a compression force), tensile strength (strength when under a tensile or pulling force), flexural strength (strength when bending) and impact energy after post-construction water absorption and ultrasonic pulse velocity at 28 days of curing in both freshwater and simulated sea water environments. Results show that marine cured materials reduced the compressive strength of plain concrete by about 7.6%, as well as adversely affected other mechanical and durability properties; however, fiber reinforcement substantially minimized these negative effects. Steel fiber concrete was the most improved type of fiber concrete, enhancing the compressive strength by up to 16.5%, as well as enhancing the post-crack impact energy more than six times over the control mixture. Carbon fiber reinforced concrete demonstrated superior durability characteristics, Water absorption increased from 3.80% in freshwater-cured plain concrete to 4.25% in marine-cured plain concrete, while fiber-reinforced concrete under marine conditions reduced the value to as low as 3.40% Similarly, ultrasonic pulse velocity decreased from 3.80 km/s to 3.68 km/s in marine plain concrete, whereas fiber-reinforced mixes, particularly steel fiber concrete, achieved values up to 4.11 km/s, indicating improved internal quality. Glass fibers provided moderate improvements in both strength and durability properties, and overall, fiber reinforcement reduced permeability and enhanced crack resistance under marine exposure conditions. These results demonstrated the potential of using seawater to cure fiber-reinforced concrete and using sea sand to replace part of the fine aggregate to provide durable performance and thus support its potential as a viable alternative to traditional materials in coastal areas or where access to resources is limited