Experimental Study On Mechanical Properties Of Steel Fiber Reinforced Concrete With Expanding Agent

Eexpanding agent is a kind of additive which can effectively reduce the autogenous shrinkage of concrete.Adding expanding agent in concrete,the expansion of the expanding agent in its hydration hardening process can compensate or even offset the autogenous shrinkage of the concrete,which avoids cracks caused by the autogenous shrinkage of concrete.However,the influence of expanding agent on the mechanical properties of concrete is still controversial,which restricts the popularization and application of expanding agent.Steel fiber reinforced concrete is a composite material composed of concrete as based material and steel fiber as reinforcing material.Steel fibers distributed in random directions in steel fiber reinforced concrete have the effect of cracking,strengthening,and toughening,making steel fiber reinforced concrete have a wide range of engineering applications.Although the research of steel fiber reinforced concrete is mature,there is still less research on the performance of steel fiber reinforced concrete mixed with expandive agent.For example,in the aspect of axial compression performance,the research of steel fiber reinforced concrete with expanding agent is still not systematic enough.Besides,in terms of the bonding properties between reinforcing steel and concrete,the combined effects of expanding agent and steel fiber on bonding performance are rarely reported.Therefore,it is necessary to carry out experimental study on the axial compression and bonding properties of steel fiber reinforced concrete mixed with expandive agent,which will provide guidance for the engineering application of steel fiber reinforced concrete mixed with expandive agent.In this dissertation,axial compression test and steel bar pull out test were carried out with water cement ratio,expanding agent content and steel fiber content as control variables.Based on the test results,the effects of water,expanding agent contents and steel fiber contents on the axial compression and bonding properties of concrete were discussed.This dissertation completes the following contents:(1)To investigate the effects of water to cement raio,content of expanding agent and content of steel fiber on the mechanical properties of compression of concrete,a series of concrete expanding agent and/or steel fiber was produced for axial compression test.The results of the test are as follows: 1)When the water to cement ratio increased,axial compressive strength and toughness reduced significantly.But the water to cement ratio has no significant effects on elastic modulus,poisson's ratio and specific toughness.2)The contents of expanding agent has an important effect on specific toughness,the expanding agent content increased,and specific toughness increased significantly.But expansive contents have no significant effects on axial compressive strength,elastic modulus,poisson's ratio and toughness.3)When steel fiber contents increased,toughness increased significantly.But steel fiber contents have no significant effects on axial compressive strength,elastic modulus,poisson's ratio and specific toughness.(2)To investigate the effects of water,content of expanding agent and content of steel fiber on the bond properties between steel reinforced bar and concrete,a series of concrete expanding agent and/or steel fiber was produced for steel reinforced bar pull out test.The results of the test are as follows: 1)As the water to cement ratio increased,bond strength decreased significantly,and bond stiffness increased but not significant.2)As the expansive contents increased,bond stiffness increased significantly,and bond strength increased but not significantly.3)As the steel contents increased,bond strength and bond stiffness increased significantly.4)Expanding agent and steel fiber have synergistic effects on bond strength and bond stiffness.