Effects of Polyoxymethylene Fiber on Mechanical Properties of Seawater Sea-Sand Concrete with Different Ages

Workability and mechanical properties of the seawater sea–sand concrete (SWSSC) were similar to those of ordinary concrete made with freshwater and river sand, which had a wide application in structures. Since the polyoxymethylene (POM) fiber performed the outstanding alkali resistance and durability, POM fibers were added in SWSSC in this study to enhance the mechanical properties. Moreover, the mechanical properties of concrete during the early age have significant effects on the construction phase. The experiment, including 96 test specimens, was conducted to clarify effects of POM fibers on mechanical properties of SWSSC with different ages. The cube compressive, axial compressive, splitting tensile, and flexural tests of NF and POM0.6 SWSSC were conducted. Based on test results, the predictive equations were proposed to quantify relations between concrete age and mechanical properties of NF and POM0.6 SWSSC. Effects of the concrete age on ratios f(tT)/f(cT) and f(fT)/f(cT) were investigated and quantified through proposed equations. Failure performances of NF and POM0.6 SWSSC specimens with different ages were analyzed. The microstructure of POM0.6 SWSSC specimens was observed, and the reinforcing mechanism of POM fibers was further explained.