Behavior of SCC confined in short GFRP tubes

While there is abundant research information on ordinary concrete confined in FRP tubes, there is little data on the behavior of self-consolidating concrete (SCC) under such condition. Because of the usually higher total shrinkage and lower coarse aggregate content of SCC compared to that of ordinary concrete, its composite performance under confined conditions needs special investigation. SCC confined in FRP tubes can have unique structural applications. For instance, cast-in-place deep foundations such as drilled shaft piles are often subjected to two sources of problems. First, the integrity and uniformity of the cross-sectional area of these structural elements cannot be assured using normal concrete because of limited accessibility and visibility during construction. Cavities and soil encroachments leading to soil and air pockets can jeopardize the load-bearing capacity of such piles. Second, corrosion problems of steel reinforcement in deep foundations have been costly, requiring annual repair costs of more than $2 billion in the US alone. SCC, which is able to consolidate under its self-weight without vibration, can be cast into GFRP envelopes that act as corrosion-resistant reinforcement to offer an alternative pile construction method that addresses both challenges cited above. To demonstrate the concept, this paper presents results of a laboratory investigation on the behavior of SCC confined in short GFRP tubes and subjected to axial and transverse load, including the effect of using expansive cement and shrinkage-reducing admixtures to enhance the GFRP tube-SCC interfacial contact.