Axial Compression Performance Of Concrete Columns Confined With Fiber Reinforced Geopolymer Mortar

Geopolymer is a new type of non-cement-based inorganic cementitious material emerging in recent years.Geopolymer has the advantages of fast hardening and early strength,good compatibility with old concrete interface,good high temperature resistance effect and strong corrosion resistance,etc.Therefore,geopolymer is considered as an excellent civil engineering repair and reinforcement material.In order to further explore the diverse development of geopolymers in the field of civil engineering restoration and reinforcement,this paper adopts basalt fiber braided network and short-cut fiber to conduct composite strengthening and toughening of geopolymers according to fiber toughening technology,and forms two kinds of geopolymers composite materials,namely FRGM and HPGM composite materials.This paper first studies the mechanical properties of two kinds of ground polymer composites,and then mainly studies the compression properties of FRGM confined concrete and concrete strengthened by FRGM and HPGM at high temperature.The main research contents of this paper are summarized as follows:1.Uniaxial tensile test was carried out on FRGM composites to study the influence of the strength of geopolymer mortar and the number of basalt fiber braid mesh layers on the tensile properties of FRGM composites.Besides,the axial compression test and flexural test of HPGM composite were conducted to analyze the influence of the type and volume of chopped fiber on the compression and flexural performance of HPGM composite.The results showed that: with the polymer mortar strength increase and basalt fiber woven mesh layers increase,FRGM tensile specimen cracking stress of small growth and limit stress increase dramatically,but fiber utilization ratio of the specimens with the increase of mat layer is gradually reduced,and increase the polymer mortar strength can improve the utilization rate of fiber of specimen;The improvement of the compressive strength and bending strength of short-cut steel fiber is better than that of short-cut PVA fiber.At the same time,with the increase of fiber volume content,the compressive strength of short-cut steel fiber mortar increases limited,while the bending strength of short-cut steel fiber mortar increases significantly.2.Monotone axial compression test and cyclic axial compression test were carried out on FRGM confined concrete to investigate the influence of matrix strength of ground polymer mortar,number of basalt fiber braided mesh layers and loading mode on monotone and cyclic axial compression performance of FRGM confined concrete.The results show that the peak stress,strain,ductility and energy absorption capacity of FRGM confined concrete are increased with the increase of matrix strength of ground polymer mortar and the number of layers of basalt fiber braided net.There is an approximate linear relationship between the plastic strain of FRGM confined concrete and the unloading point strain,and the plastic strain is independent of the strength of the binding action of FRGM reinforced concrete.The stress degradation process of FRGM confined concrete is divided into declining stage and stable stage.The stress degradation rate basically remains unchanged when the dimensionless unloading point strain is greater than 1.4,that is,about 0.9.3.The axial compression test of concrete strengthened by FRGM and HPGM at high temperature was carried out to study the influence of reinforcement method,temperature grade,the number of basalt fiber net layer and the type of short-cut fiber on the axial compression performance of concrete strengthened by FRGM and HPGM at high temperature.The results show that the peak stress increase amplitude of HPGM reinforced specimens is greater than that of FRGM strengthened specimens.The stiffness of specimens strengthened by FRGM has a small increase,while the stiffness of specimens strengthened by HPGM has a significant increase.As the number of layers of fiber braided mesh increases,the displacement ductility coefficient and energy absorption capacity of FRGM reinforced specimens gradually increase,and the displacement ductility coefficient and energy absorption capacity of HPGM reinforced specimens of short-cut steel fiber series are greater than those of short-cut PVA series of specimens.