Experimental study on bond behavior of new type cement grouted GFRP bolts

Abstract

Bolt is widely used in slope engineering, tunnel, and large cave supporting as well as restoration of engineering structure. It can improve the strength and stability of ground, rock mass, and other structures. The traditional steel bolt has some disadvantages, such as easy corrosion, heavy weight, and difficult operation. Glass fiber reinforced polymer (GFRP) is impervious to chloride ion and low pH chemical attack, and its tensile strength is much larger than steel while with lighter weight. Those advantages make it a better alternative in some fields of engineering. To utilize GFRP bars as rock bolt, some aspects of its behavior, such as bond strength in mortar, bearing capacity, and bond stress distribution along its interface, have to be examined. This paper presents the research on bonding behavior of anchor bolt made of GFRP bar, and concrete block is used to model rock mass in laboratory. The modified pull-out tests were conducted on selected GFRP bars and compared with steel ones that were grouted with mortar in concrete blocks. The diameters of the GFRP test samples are 10, 13, 16 mm respectively, and the steel one is 25 mm. There total 24 samples are tested. The surface of the GFRP bar is sprayed with sand and wound with fibers. The compressive strength of concrete which is used to simulate the rock mass is 58.3 MPa; and the compressive strength of two kinds of mortars are 41.5 and 55.5 MPa, respectively. According to the results, bond characteristics of mortar grouted GFRP rock bolts such as failure modes, bearing capacity, critical bond length, average bond strength, and comparison with steel bolt were evaluated. The research will give a support to the application of GFRP bolt.