Research On Physical And Mechanical Properties Of The Early Age Concrete And Its Creep Under Tension And Compression

Cracks often occur in the early age curing of concrete,which seriously affects the structural performance.The early age tensile/compressive of creep characteristics of high-strength concrete and its creep stress calculation method are the key to the effective prediction and control of early fractures.The existing creep research results focus on mature concrete,and the scientific research on creep of early age concrete should be further studied.Based on Jiayu Changjiang River Highway Bridge and supported by National Natural Science Foundation of China(project number: 51408218),the physical and mechanical properties of early age concrete and tension/compression creep characteristics were studied in this dissertation.The main contents of this dissertation are as follows:(1)Physical and mechanical properties of concrete were tested and studied.The cubic compressive strength,the prism compressive strength and the elastic modulus of the C40,C50 and C55 concrete in the early age were measured under the standard condition and the site condition after the construction site sampling and the production of concrete specimens.The development law of physical and mechanical properties of early age concrete under different curing conditions was analyzed,in turn,the formula was obtained.(2)The early age of concrete was tested for compression and tensile creep.In the field laboratory,concrete shrinkage,early age tensile and compressive creep tests were carried out.The test parameters include: concrete strength grade,loading age,surface ratio,reinforcement rate,curing temperature,stress ratio and so on.The experimental results were collated and analyzed,and the influence of different parameters on the tensile and compressive creep of concrete in early age was obtained.(3)The tensile and compressive creep characteristics of concrete at early age were analyzed.The tensile and compressive characteristics of early age concrete under the same conditions were compared and analyzed.The applicability of the existing normative model was evaluated based on the experimental data.The critical stress ratio of nonlinear creep under tension and compression was obtained.