Experimental Study on Axial Compressive Load-Bearing Performance of RC Short Columns Strengthened by All-Light Ceramsite Concrete

Abstract

Previously conducted studies have established that all-light ceramsite concrete has the characteristics of light weight and high strength. It is a good material for strengthening and has a good application prospect when strengthening existing RC columns by the enlarged cross-section method. Additionally, a good combination of new-to-old concrete is crucial to the best performance of RC columns strengthened by the enlarged section method. Therefore, to investigate more comprehensively the axial compression reinforcement effect of RC short columns strengthened with all-light ceramsite concrete, one unreinforced short column, one RC short column strengthened by ordinary concrete, and four RC short columns strengthened by all-light ceramsite concrete with different interface treatments were produced. Moreover, axial pressure tests were conducted on them. The findings showed the following: (i) Short-column specimens strengthened by all-light ceramsite concrete had obvious ductile damage characteristics. (ii) The type of bonding surface greatly affected the strengthening effect. The order of ultimate load-bearing capacity improvement was post-installed rebar + epoxy resin interface agent, epoxy resin interface agent, post-installed rebar, and chiseling. (iii) When post-installed rebar + interface agent was used, the epoxy resin interface agent played the primary role during the pre- and mid-loading period. The post-installed rebar started to function only in the mid- and late-loading period. (iv) Strain growth of the existing longitudinal bar and strengthening longitudinal bar was not synchronized in the late-loading period. The strain in the existing longitudinal bar grew rapidly and nonlinearly, while the strengthening longitudinal bar still grew linearly. (v) The calculation formula in specification GB50367-2013 is also applicable to ceramsite concrete, and the correction factor can still be 0.8. When the interface treatment method is post-installed rebar + epoxy resin interface agent, the correction factor can be 0.9.