Compressive Behaviors Of Cubic And Cylindrical Specimens Made Of Normal-strength Demolished Concrete Blocks And High-strength Fresh Concrete

Compared with recycled aggregate concrete (RAC), structural members filled withdemolished concrete blocks (DCBs) and fresh concrete (FC) are new effective approaches inrecycling demolished concrete using large scale demolished concrete (DC, i.e. blocks orsegments) instead of aggregate. Some preliminary mechanical and seismic properties and fireresistance performance of specimens made of DCBs and FC have been conducted by ourresearch group. To further improve the theoretical system of composite components made ofDCBs and FC and expand the application scope of DC, the author carried out research on themechanical properties of concrete specimens made of DCBs and high-strength FC underuniaxial compressive loading based on the existing researches. The main achievementsinclude that:Thirty300mm cubic specimens and twenty-four cylindrical specimens (diameter300mm, height600mm) were fabricated using DCBs and high-strength FC (the differencesbetween strength of DC and FC are in the range of40MPa to90MPa). The compressivebehaviors of cubic and cylindrical specimens made of normal-strength DCBs andhigh-strength FC under uniaxial loadings are experimentally studied, and the influences of thestrength of DC, the strength of FC, and the replacement ratio of DCBs on the compressivebehaviors of the specimens are discussed. Predictions of composite concrete strength,modulus of elasticity and peak strain are formulated. Test research results show that:(a) thelarger the difference between the demolished concrete’s strength and the fresh concrete’sstrength is, the more significant influence of the DCBs on the combined compressive strength,modulus of elasticity and peak strain of the specimens;(b) The influence of the DCBs on thecombined compressive strength of the cylindrical specimens is more significant than that onthe combined compressive strength of the cubic specimens;(c) The ratio of the strength ofcubes and cylinders ranges from0.61to0.69for the concrete mix made of normal-strengthDCBs and high-strength FC, and the average value is0.65, which is lower than the ratio forthe conventional high-strength concrete;(d) No monotonic trend being found for the influence of the replacement ratio of DCBs on the peak strain of the cylinders made ofnormal-strength DCBs and high-strength FC;(e) The calculated results using proposedprediction formulas are generally in good agreement with the measured results.Based on the general finite software ABAQUS, numerical simulation on the compressivebehaviors for above specimens filled with DCBs and FC was carried out and compared withtest results. It indicates that:(a) Based on Cohesive Behavior of DCBs and FC in ABAQUS,calculation results agree well with the experimental results.(b) The minimum principalstresses distribute symmetrically in specimens made of FC alone, but the minimum principalstresses distribute asymmetrically in specimens made of DCBs and FC influenced by specificlocations of DCBs;(c) The load ratios shared by DCBs in cubes inside show little change orslight decrease at the beginning and then rapidly rise during loading, but the load ratios sharedby DCBs in cylinder show decrease at the beginning and then rapidly rise and finally declineor remain basically unchanged again during loading.