Rearch On Performance Of Ultra High Secondary Pumping C50Concrete In Mi River Bridge Continuous Rigid Frame Bridge

The Mishui river extra-large bridge,which is the key control project of whether the Yan-Ru highway can be opened to traffic smooth,is an extra large type bridge across deep river valleys and Mishui River. In order to guarantee the bridge constructed and opened to traffic successfully, the linear complying with the design requirements, the bridge deflection ranging within the control values of the specification and aiming at series of problems such as the deflection of long-span prestressed concrete continuous rigid frame bridge is too large at home and abroad, combining with the key technology and actual situation of the Mishui river extra-large bridge, and guaranteeing the super durability and long life of Mishui river extra-large bridge, the research on C50prestressed high performance concrete creep effect of the Mishui river continuous rigid frame extra-large bridge has important guiding significance and engineering application value. The main research contents and results are as follows:1) The research on the configuration optimization technology of C50pumping high performance concrete:according to the result of the mix proportion optimal designing of C50high performance concrete, the study intends to select three groups mix proportions (fly ash,slag and composite admixture of them) and a baseline group of C50high performance concrete (only cement for binding materials), contrasted testing the workability, mechanical strength, creep properties and drying shrinkage performance. According to the test results, put forward to the effective measures and methods of reducing creep deformation of high secondary pumping C50high performance concrete;2) The test results show that the slump value of the concrete of baseline group is185mm, and the slump value of the concrete added mineral admixture may reach205mm.It explains that the carboxylic acid high efficiency water reducing agent,adopted in the study,has good dispersion effect on the mixture of cement, fly ash and mineral powder has good dispersion effect, can effectively improve the workability of high performance concrete added mineral admixture, making it satisfy the construction requirement of the secondary pumping concrete. In addition, the specimens of concrete with binding material only mixed slag have a slight bleeding phenomenon when mixing and vibration; and the rest specimens have no bleeding phenomenon;3) That adding mineral admixture to concrete has improved the creep performance of concrete effectively, in which the effect of the single mixing mineral slag is the best; the creep deformation of350d ages concrete with single mixing fly ash, mineral slag and double mixing concrete mixing is lower than the base concrete by28.4%,43.1%and36.3%respectively; the creep degree of70d ages concrete with single mixing fly ash, slag and double mixing concrete mixing is lower than the base concrete by35.3%,58.3%and48.6%respectively; the creep coefficient of70d ages concrete with single mixing fly ash, mineral slag and double mixing is lower than the base concrete by36.9%,36.9%and45.9%respectively.4) From the perspective of the results of the drying shrinkage test, The addition of mineral admixture has reduced the drying shrinkage of concrete effectively; Compared with fly ash, slag has a better effect on the reduction of C50high performance concrete shrinkage; The contraction deformation of different mixing proportion of concrete increases along with the age growth, and the early deformation developed rapidly while the late deformation developed flatly. The shrinkage and creep of concrete increase rapidly in the early28days,and slow gradually later;5) Admixtures improve the internal pore structure and characteristics of cement, reducing the aperture in (20±3)℃, relative humidity of (60±5)%under ambient conditions, concrete admixtures than pure cement water evaporation Concrete slow, that smaller drying shrinkage deformation; performance concrete creep lower primarily due to admixture of the accession of hardened paste structure is more compact.6) C50high performance concrete cracking performance results showed that after mixing fly ash or slag concrete cracking performance has been significantly improved, crack resistance of fly ash and slag, fly ash concrete than single or Slag effect is more significant. This suggests that adding admixtures, effective mitigation and suppression of the creep of concrete, thus effectively improving the crack resistance of concrete.