粉煤灰对微膨胀碱活性骨料混凝土的影响

Effects of Fly-ash on Micro Expansion Concrete with Alkali-active Aggregate

为探究碱活性骨料在大体积混凝土工程应用的可行性,进行了混凝土中粗骨料的碱硅酸反应抑制试验、抗压强度试验、自生体积变形试验和快速冻融试验。结果表明：对所研究骨料掺加30%粉煤灰和3%~5%的轻烧氧化镁能有效抑制骨料碱硅酸反应;粉煤灰使碱活性骨料混凝土前期强度降低,后期强度提升较快,而3%~5%的轻烧氧化镁对强度影响不明显;粉煤灰会降低轻烧氧化镁产生的自生体积膨胀,但不改变轻烧氧化镁这一特性;粉煤灰对碱活性骨料混凝土抗冻性有不利影响,而轻烧氧化镁能改善混凝土抗冻性。因此,合理的粉煤灰和轻烧氧化镁掺量能使碱活性骨料在大体积混凝土中的应用成为可能。

For the engineering application of alkali-active aggregate in mass concrete,the alkali-silica reaction inhibition test,compressive strength test,autogenous volume deformation test and the fast freeze-thaw test using alkali-active aggregate with different dosage of fly ash,light-burned Mg O were carried out. The tests showed that： alkali-silica reaction is effectively restrained when the fly-ash content is 30% and light-burned Mg O content is 3% ~ 5%; Fly-ash make concrete early strength reduced,the late strength increased fast,and the amount of 3% ~ 5% light-burned Mg O dosage has little impact on the strength;light-burned Mg O autogenous volume deformation will be reduced by hydration of fly-ash,but fly-ash cannot change this characteristics of light-burned Mg O; fly-ash has adverse effects on frost resistance of concrete,and light-burned Mg O can improve the frost resistance of concrete. So,the reasonable dosage of fly-ash and light-burned Mg O make the alkali-active aggregate concrete possible be applied in the mass concrete.