Abstract: Restrained shrinkage behavior of ultra high performance concrete (UHPC) incorporating different HCSA expansion agent dosages (0%, 3%, 6%) without thermal curing was investigated by ring test, including three parts: (1) direct tensile stress-strain test of UHPC; (2) free shrinkage test of UHPC according to GB/T 50082; (3) restrained ring-test of UHPC according to ASTM C1581. The results indicated that three types of UHPC all achieved ultimate tensile strain higher than 3 000με. The 28 d free shrinkage values of three types of UHPC were 1 005.6με, 600.0με, 462.2με respectively, which converted into residual strain, elastic tensile strain and plastic tensile strain under ring restraint whose values were 700.4με, 437.9με, 389.9με, respectively. None of the three kinds of UHPC shows a crack wider than 0.01 mm both in the direct tensile test before a tensile strain of 1 000με and in the ring test. The plastic tensile deformation mechanism of UHPC based on the direct tensile test and acoustic emission (AE) analysis method shows that the tensile stress-strain curves of the three kinds of UHPC all have the strain-hardening properties and their plastic deformation presents in the form of multiple cracks smaller than 0.01 mm in the ring test. Adding HCSA expansion agent can effectively reduce the tensile stress of UHPC and influence of UHPC on the structure.
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2017, Vol. 31 
