A novel packing-coupled stress-strain model for confined concrete

To develop low carbon footprint concrete (LCFC) with less CO2 emissions, various minerals (limestone, metakaolin) and industrial waste by-product (fly ash (FA), silica fume (SF), slag) were used to replace cement partially. By optimizing the packing structure, cost-effective, sustainable LCFC with superior strength, workability and durability performances could be achieved. Research studies on fiber-reinforced polymer (FRP) confined LCFC showed that the peak stress, strain at the peak stress and post-peak branch of confined LCFC was far different from that of confined conventional concrete (with cement as the cementitious material only) with the same concrete strength and confinement scheme. To look at this problem more scientifically, this paper conducted experimental and analytical studies about the stress-strain curves of FRP-confined LCFC. A total of 45 concrete column specimens consisting of 15 unconfined concrete and 30 FRP-confined concrete were tested under uni-axial compression. The studied parameters were the thickness of FRP, water- and FA/SF-to-cementitious material ratios. Based on the test results, a novel packing-coupled stress-strain model for confined LCFC has been proposed and verified.