摘要 :
The strength and shrinkage behaviors of roller-compacted concrete (RCR) with used tire-rubber additive were experimentally investigated by keeping the compressive strengths of all specimens at the level of 40 MPa. Four rubber cont...
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The strength and shrinkage behaviors of roller-compacted concrete (RCR) with used tire-rubber additive were experimentally investigated by keeping the compressive strengths of all specimens at the level of 40 MPa. Four rubber contents were used: 50, 80, 100, and 120 kg/m~3. Test results show that the rubber particles homogeneously distributed in RCR, rubber particle emersion was not observed during vibrating for compaction. The workability of RCR was slightly influenced by replacing portion of sand with the same volume of tire rubber particles. RCR specimen exhibited a ductile failure under compression. In comparison with the control concrete, when the compressive strength was kept constant for RCR, the tensile strength, flexural strength, and ultimate tension elongation increased with the increase of rubber content. The incorporation of tire rubber did not help in reducing the drying shrinkage, on the contrary, a little more drying shrinkage developed in RCR than that in the control concrete.
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摘要 :
The strain monitoring and stress analysis of a new type of post-prestressed tunnel liner were carried out. The instrumentation block of the tunnel liner, with the dimensions of 12.06 m in length, 6 500 mm in diameter, and 650 mm i...
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The strain monitoring and stress analysis of a new type of post-prestressed tunnel liner were carried out. The instrumentation block of the tunnel liner, with the dimensions of 12.06 m in length, 6 500 mm in diameter, and 650 mm in thickness, was post-prestressed with the unbonded tendons, each of which consists of 8 pieces of double-looped strands and the axial spacing of the tendons is 500 mm. Concrete strain meters, rebar meters, load cell and zero-stress meters were installed for the strain monitoring. The tensioning loads were applied incrementally in three cycles (50 percent, 77 percent and 100 percent) at the concrete age of 28 d and the tensioning work lasted for 187.1 h. Strain readings were taken before and after each cycle during tensioning period and at the specified time interval after tensioning period. It is found that concrete creep developed over tensioning period is 30 percent of total strain and 41.5 percent of elastic strain respectively. Prestress force in the unbonded tendon and concrete stress in the liner were evaluated according to the observed strain variations. Both of them are time-dependent, and about 5.3 percent, 8. 3 percent and 9.0 percent of the prestress losses are observed at the age of 1 d, 30 d and 60 d respectively after stressing. The distribution of prestress in the liner is relatively uniform and meets the design requirement.
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