影响混凝土Cl^-导电量诸因素的分析

Analysis of the factors influencing the charge passed of concrete

本文利用ASTMC1202标准,测量了不同水灰比下掺与不掺矿物质混合材的混凝土6小时总导电量,并对影响混凝土导电量的因素进行了具体分析。试验表明:随水灰比的增加,混凝土导电量明显增加;掺加不同种类的矿物质混合材会降低混凝土导电量,其中硅灰(SF)效果优于粉煤灰(FA),粉煤灰的效果又优于沸石(NZ),而矿渣掺量小于30%时导电量不会降低。存在离析和泌水时,表层混凝土导电量明显高于底层,且各向异性使得混凝土在垂直方向上的导电量各不相同;同时,烘干状态混凝土的电导也各不相同,我们称之为干态电导。这说明对掺加矿物质超细粉后混凝土抗CI-渗透性的评价不应仅以导电量为标准,应结合混合材的种类和掺量、混凝土干态电导及由于离析和泌水造成的各向异性等情况进行具体分析。

The charge passed of concrete with different water/binder ratio and different kind of mineral admixtures were measured according to ASTM C1202,and the factors influencing the value analyzed.It is shown that the charge passed data increased considerably with the increase of W/B ratio,while the incorporation of different mineral powder may decrease the data,except that the slag powder,with a dosage of less than 30%,increased the value slightly.Among the minerals involved,the effect of the silica fume(SF) is better than that of fly ash(FA),and FA better than natural zeolite(NZ).For segregation and bleeding concrete,the charge passed of the superficial part is much higher than that of the inner one's,and the existence of anisotropy brings difference in the perpendicular directions.In the mean time,the fundamental conductivity,the conductivity of concrete in drying state,is also diferent when different minerals were added.As a result,the evaluation of chloride diffusivity of mineral-incorporated concrete with charge passed data may gives misleading result,and the types of mineral powder,the fundamental conductivity,as well as the anisotropy cused by bleeding and segregation should all be taken into consideration.