复掺矿物掺合料混凝土抗氯盐侵蚀与抗冻性试验研究

Effects of compound mineral admixture on chloride corrosion resistance and frost resistance of concrete

为研究矿物掺合料对混凝土耐久性能影响,分别对单掺粉煤灰、双掺粉煤灰和硅灰、三掺粉煤灰、硅灰和矿渣微粉3种情况下混凝土抗压强度、电阻率、氯离子扩散系数以及抗冻性能进行了试验研究。此外,通过对试件进行电镜扫描,揭示了矿物掺合料对混凝土微观结构的影响。结果表明:矿物掺合料可以改善混凝土孔结构,提高密实性。掺入矿渣微粉混凝土3 d抗压强度略低,但7、28 d强度增长明显,28 d强度分别比单掺和双掺试件提高3.80%、43.29%;硅灰和矿渣微粉均能显著提高混凝土抗氯离子渗透能力,双掺和三掺混凝土试件氯离子扩散系数分别比单掺试件降低69.16%、83.13%;硅灰可以提高混凝土抗冻性,双掺混凝土比单掺抗冻耐久性系数提高3.86%;同时混凝土电阻率和氯离子扩散系数之间存在线性负相关关系。在冻融循环过程中,混凝土动弹性模量与质量损失和动弹性模量损失均存在负相关性。

In order to study the effect of mineral admixtures （ fly ash, silica fume, and slag powder ） on the durability of concrete, the compressive strength, resistivity, chloride diffusion coefficient and frost resistance of the three kinds of concrete were tested and analyzed. The mineral admixture was mixed into concrete separately or in combination.In addition,the effect of mineral admixtures on microstructure of concrete was revealed by scanning electron microscope.The results show that mineral admixtures can improve the pore structure and compactness of concrete.The early compressive strength of concrete mixed with slag powder was slightly lower, but the strength increased significantly in the 7 and 28 days,the compressive strength of concrete at 28 days increased by 3.80% and 43.29% compare with single or double doped concrete.Silica fume and slag powder can significantly reduce the chloride diffusion coefficient of concrete.Double doped and three-doped concrete chloride diffusion coefficient respectively decreased by 69.16% and 83.13% than the single doped.Silica fume can improve the frost resistance of concrete, and the durability of concrete is improved by 3.86% than the single doped with fly ash.lt is found that the chloride diffusion coefficient and resistivity have good linear negative correlation.There is a negative correlation between the dynamic elastic modulus and mass loss of concrete during the freezing and thawing cycles, there is also a negative correlation between the dynamic elastic modulus and dynamic elastic modulus loss of concrete.