含二水石膏水泥的细度测定

Determination of Finepess for Cements Containing Gypsum

用透气法测定含多量二水石膏水泥的比表面积之极差达200～700cm^2/g,用XRD和OM分析了原因。在110℃烘样过程中,烘样温度、时间、设备和相对湿度的不大变化造成二水石膏不同程度的脱水,石膏颗粒表面开裂和粉化状况不一,引起对气流阻力不同和比表面积测定值的增加及波动。用负压筛测这类水泥的细度精确度好,不需烘样,也没有堵筛现象,文中给出了工作参数。本文还描述了石膏脱水特征,并指出磨细脱水石膏对水泥比表面积大小有令人注目的影响。

The extreme deviation of specific surface determination for cements with much gypsum using the air permeability method can be as high as 200～700 cm^2/g. The reason for that is studied with XRD and OM. During the sample drying at 110℃, a small change in drying temperature, time, relative humidity and drying apparatus causes gypsum dehydrating to different degrees, gypsum surface cracking and partical splitting in different states, which produce bigger and varied resistance to the air flow through the sample layer, thus the specific surface determined increases and varies. The fineness determination using the air-stream sieve is pre- cise and need not dry cement samples. The characteristic for gypsum dehydration is described. It is noted that the ground and dehydrated gypsum has striking contribution to the specific surface of a gypsum-containing cement.