Fine gray powder made up of compounds of lime, aluminium, silica and iron oxide. A type of hydraulic cement. According to information available, the name "Portland Cement" is more of a generic title referring to a family of cements rather than a particular product. Name is apparently derived from the fact that the cargo resembles the colour of Portland Stone when hard i.e., limestone from the Isle of Portland, Dorset, Southern England.Also, it is also a finished product when grounded cement is mixed with gypsum, the latter acts as a retardant to prevent the cement from setting too quickly when in touch with water. According to the IMSBC Code for "cement", it becomes fluid when aerated (i.e.,exposed to chemical reaction of air) or disturbed significantly, producing a very minimal angle of repose. Once loading is completed, de-aeration starts almost immediately and the product settles into a stable mass. Cement contracts about 12% from state of aeration to non-aeration.
|