Structural performance of construction and demolition waste-based geopolymer concrete columns under combined axial and lateral cyclic loading

Construction and demolition waste (CDW) has reached severe environmental and economic dimensions due to its large volume among all solid waste, highlighting the importance of local actions to manage, recycle, and reuse CDW. Ductile demountable connections are necessary to disassemble and reuse the concrete structural members and fast assembly of precast structures in seismic regions without generating waste. In this study, the seismic performance of CDW-based reinforced geopolymer concrete columns has been investigated. Six 1/2scaled columns (half of which were demountable and the other half monolithic) were experimentally tested under reversed cyclic lateral displacement excursions, considering three different levels of constant axial loading to determine failure mechanisms, load-displacement responses, ductilities, energy dissipation capacities, stiffness degradation relations, and curvature distributions. The obtained test results were used to determine the performance of CDW-based geopolymer concrete columns and compare the performances of the demountable connection with the monolithic connection. The test results showed that the novel demountable connection for precast concrete frames exhibited better seismic performance in terms of maximum lateral load capacity, initial stiffness, energy dissipation capacity, and maximum curvature than their monolithic counterparts. Besides, increasing the axial compression ratio on the columns caused an increase in lateral load capacity, energy dissipation capacity, energy dissipation ratio, and initial curvature stiffness; however, it decreased the ductility. Finally, the capacity pre-dictions of current codes, i.e., TS500 and ACI318, were conservative when compared with experimental results.