掺粉煤灰高性能桥用混凝土变形性能研究

Study on the deformation properties of the high performance concrete with fly ash used in bridge

结合南京长江第二大桥的工程建设 ,对掺粉煤灰高性能混凝土变形性能进行了试验研究 .混凝土力学性能试验依据GBJ81— 85进行 ,收缩试验依据GBJ82— 85进行 ,徐变试验依据JTJ2 70— 98进行 ,自生收缩试验方法 (除不加载外 )同徐变试验 .试验结果表明 ,掺I级粉煤灰和高效减水剂的C5 0高性能混凝土不但具有良好的工作性能和力学性能 ,还可提高混凝土抵抗弹性变形、收缩变形和徐变变形的能力 .与同强度等级未掺粉煤灰的混凝土相比较 ,掺入质量分数为 1 2 %～ 2 4%的I级粉煤灰 ,取代 1 0 %～2 0 %的硅酸盐水泥 ,其后期强度和抗压弹性模量增大 ,干燥收缩和徐变降低 .通过分析研究 ,还得出不同粉煤灰掺量及配比的C5 0高性能混凝土徐变计算公式 。

For the application in the Second Bridge of Nanjing Yangze River, the deformation properties of high performance concrete with fly ash were investigated.Mechanical properties, shrinkage and creep tests were conducted according to the standards of GBJ81-85, GBJ82-85, and JTJ270-98 respectively. Test of autogenous shrinkage (except non loaded) was performed in same way as creep test. The test results show that C50 high performance concrete incorporated with both grade Ⅰ fly ash and high efficient water reducing agent not only has better workability and mechanical properties, but also show higher resistance to elasticity deformation, shrinkage deformation and creep deformation. A concrete with 12%-24% gradeⅠ fly ash as the substitution of 10%-20% portland cement was tested compared with the reference concrete of same strength but without fly ash. The results show that with fly ash the concrete has higher later stage strength and compressive elastic modulus, lower drying shrinkage ratio and less creep. Based on the experimental results, a formula is developed to calculate the creep of C50 high performance concrete with different proportion of fly ash.