Mechanical properties of discrete BFRP needles reinforced seawater sea-sand concrete-filled GFRP tubular stub columns

Abstract

This paper proposes a new type of tubular column, which is composed of glass fiber-reinforced polymer (GFRP) tube and discrete basalt fiber-reinforced polymer (BFRP) needles reinforced seawater sea-sand concrete (SWSSC). The discrete BFRP needles, with an aspect ratio of 10.0, were cut from BFRP bar production scrap and mixed into fresh concrete to replace 20% of the coarse aggregates by volume. The axial compression properties and lateral bending properties of the tubular columns were tested. The test variables included the wall thickness of the GFRP tubes (i.e., 3 mm and 4 mm), the type of coarse aggregates (i.e., gravel or coral), and the incorporation of BFRP needles or not. Additionally, unconfined bare columns were tested for comparison. The test results showed that the inclusion of BFRP needles had moderate adverse effects on the peak compressive strength of bare columns: the peak axial stress reduced slightly by 2.5% for gravel concrete and 7.2% for coral concrete, respectively. Besides, for the four types of concrete in this paper, the 3- and 4-mm GFRP tube-confinement increased the peak axial compressive strengths by 23 ~ 52% and 65 ~ 83%, respectively. In addition, the adoption of GFRP tubes was able to improve the bending performance of columns significantly, especially for energy consumption.