Sorptivity and mechanical properties of fiber-reinforced concrete made with seawater and dredged sea-sand

The use of seawater and sea-sand as raw materials in concrete production has been gaining increasing attention due to the rapid depletion of freshwater and normal sand resources. On the other hand, partially replacement of cement with industrial waste materials such as ground granulated blast furnace slag (GGBS) and fly ash (FA) can considerably reduce CO2 emissions due to the reduced consumption of cement. In this paper a high strength concrete by using seawater (SW) and dredged sea-sand (DSS) was developed and the effect of the addition of different type and percentage of fibers on its properties was investigated. Two different types of synthetic fibers, namely polypropylene (PP) and polyvinyl alcohol (PVA), with volume fractions of 0.1, 0.2, 0.3, and 0.5% were used for reinforcement. In all the concrete mixes cement was partially substituted with GGBS. Fresh concrete properties including slump, air content and fresh concrete density and mechanical properties, including compressive strength, elastic modulus, splitting tensile and flexural strength were examined. A series of durability tests were also conducted to determine absorption and sorptivity behavior of plain and fiber-reinforced seawater seasand (SWSS) concrete. According to the results, SW and DSS increased the early-age compressive strength of concrete by 11% and reduced the long-term strength by 10%. Incorporation of PP and PVA fibers respectively decreased (up to 12%) and increased (up to 10%) the compressive strength of SWSS concrete. Addition of both types of PP and PVA fibers changed the compression behavior of SWSS concrete from brittle to ductile mode of failure. The results also showed that the SW, DSS and different type and percentage of fibers had nearly no effect on the elastic modulus of concrete. Incorporation of PP and PVA fibers resulted in an increase of 17% and 23% splitting tensile strength compared to plain SWSS concrete. It was observed that using SW and DSS in concrete results in a considerable reduction in water absorption and sorptivity of concrete. Water absorption and sorptivity were further reduced with addition of the PP fibers. According to the results, fiber-reinforced SWSS concrete can be used specially in remote areas where freshwater and normal sand are inaccessible, and a level of cracking resistance is required. (C) 2020 Elsevier Ltd. All rights reserved.