Creep Behaviour Of Cylinders Made Of DCBs&FC And Thin-Walled Circular Steel Stub Columns Filled With DCBs&FC

It is indicated that the concrete structural members filled with demolished concreteblocks (DCBs) are new effective approaches of recycling demolished concrete, and ownprofound development potentials. Compare to Recycled aggregate concrete (RAC), concretemade of demolished concrete blocks (DCBs) and fresh concrete (FC), which use large scaledemolished concrete (i.e. blocks or segments) instead of aggregate, is a new economical andenergy-saving way to reuse the demolished concrete. With the purpose perfecting the theorysystem of concrete made of DCBs and FC, three parts of research work are involved in thisdissertation:1. Basic creep tests of3fresh concrete cylindrical specimens,3demolished concretecylindrical specimens and8cylindrical specimens made of DCBs and FC were conducted,test variables are replacement ratio of DCBs and long-term sustained load levels. Test resultsshow that:(1) the basic specific creep of cylinders made of DCBs and FC is larger than boththe fresh concrete and demolished concrete and increases with the increasing of replacementratio;ï¼›(2)The basic creep coefficient of the specimens made of DCBs and FC is close to thatof the fresh concrete and higher than the demolished concrete;(3) The assumption of linearcreep is acceptable for the specimens made of DCBs and FC.2. Based on the two-phase material model, methods for predicting the elastic modulusand basic creep of concrete made of DCBs and FC was proposed, the validity of the methodswas prelimilarily verified by comparing the calculated results with the test results.Thefindings show that:(1) Elastic modulus of concrete made of DCBs and FC is lower than notonly the upper bound provided by Voigt model but also the lower bound provided by Reussmodel.(2)The predicted value calculated using Counto model is lower than the test results.(3)Formula based on Counto model can be used to predict elastic modulus of concrete madeof DCBs and FC with a good accuracy.(4)The methed based on calibrated Counto model isadequate to predict basic creep of concrete made of DCBs and FC.3. Nine thin-walled circular steel tube stub columns filled with DCBs and FC weresubjected to long term sustained axial loads and the method proposed in chapter3was used topredict the creep of the specimens and compared with experimental result. It can be seen that: (1) Under the same load level, creep of thin-walled circular steel tube stub columns filled withDCBs and FC is close to the creep of thin-walled circular steel tube stub columns filled withFC.(2)Creep of the core concrete in thin-walled circular steel tube is lower than the sealedplain concrete, the stabilization of the CFST specimens is earlier.(3)A comparison of resultscalculated using the proposed models showed generally good agreement with the test result.