桥塔用内养护高强度抗裂混凝土性能研究

对比了页岩陶砂、粉煤灰黏土复合陶粒、浮石粉3种内养护材料对高强度混凝土的工作性能、力学性能和早期抗裂性能的影响,并结合桥塔混凝土结构进行了抗裂性验算。结果表明:随着内养护材料掺量的增加,不同龄期混凝土的抗压强度有所降低,但降幅不大,水胶比0.24时,每种内养护材料体积掺量控制在20%以内可满足C60混凝土强度要求;掺入3种内养护材料均可显著提高混凝土的早期抗裂性能,其中浮石粉的抗裂效果最好。结合沪通长江大桥主塔(高330 m,壁厚大多超过1.5 m)混凝土结构,针对收缩与温度应力引起的开裂问题进行了有限元抗裂性能分析,结果表明,浮石粉掺量20%的低收缩混凝土拉应力在容许范围内,开裂风险小。

Study on Performance of High Strength Crack Resistant Concrete with Internal Curing for Bridge Pylons

The influences of three kinds of internal curing materials,including shale pottery sand,fly ash clay composite ceramsite and pumice powder,on the working performance,mechanical performance and early crack resistance of high strength concrete were compared,and the crack resistance of bridge pylon concrete structure was checked.The results show that with the increase of the content of internal curing materials,the compressive strength of concrete at different age decreases,but the decline range is not large,when the water binder ratio is 0.24,the volume content of each internal curing material should be controlled within 20%,which can meet the strength requirements of C60 concrete.Adding three internal curing materials can significantly improve the early crack resistance of concrete and the effect of pumice powder is the best.Based on the concrete structure of the main pylon in the Shanghai-Nantong Yangtze River Bridge with 330 m height,where most of the wall thickness is more than 1.5 m,the finite element crack resistance analysis was carried out for the crack caused by shrinkage and temperature stress.The results indicate that the tensile stress of low shrinkage concrete with 20%pumice powder is within the allowable range and the risk of crack is small.