Cement

Infobox on Cement
Example of Cement
Facts
Origin	-
Stowage factor (in m3/t)	-
Humidity / moisture	-
Ventilation	-
Risk factors	-

Cement

Description

Grey dusty cargo.

In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together.

Cement used in construction is characterized as hydraulic or non-hydraulic. Hydraulic cements (e.g., Portland cement) harden because of hydration chemical reactions that occur independently of the mixture's water content; they can harden even underwater or when constantly exposed to wet weather. The chemical reaction that results when the anhydrous cement powder is mixed with water produces hydrates that are not water-soluble. Non-hydraulic cements (e.g., lime and gypsum plaster) must be kept dry in order to retain their strength.

The most important use of cement is the production of mortar and concrete—the bonding of natural or artificial aggregates to form a strong building material that is durable in the face of normal environmental effects.

Concrete should not be confused with cement because the term cement refers to the material used to bind the aggregate materials of concrete. Concrete is a combination of a cement and aggregate. Check temperature before loading as may have recently been in a kiln.

Cement is shipped in bulk or, alternatively, in 50 kg paper sacks or one to two tonne polypropylene bags. Bagged cement for export is packed in multi-ply bags with up to five layers, one of which can be made from a damp-proof or water-proof material. Kraft paper sacks have a gummed seal which effectively guarantees water tightness. Cement deteriorates with age because of absorption of moisture and/or carbon dioxide from the air. The deterioration may not affect the appearance of the cement, but can, over a long period of time, significantly reduce its performance. Sugar should never be stored over cement as sugar contamination seriously affects the setting and hardening performance.

Bulk cement in specially designed vessels will present few problems provided that holds are initially dry and properly closed and condensation does not occur. If moisture reaches the cement, a hard crust or lumps will result and must be discarded. Over a normal voyage period the powder will be perfectly usable even if a crust has formed. Stowage factor for bulk cement is 0,61-0,64 m3/t.

Bagged cement when stowed should be protected from water or damp and preferably stowed on a flat surface to prevent splitting and breakages. The use of pallets and shrink wrapping helps in this respect. If bags have been badly wetted by the ingress of sea water or by heavy rain, hard lumps may develop, usually at the corners of the bags. The powdered cement not affected by water may be sound and usable.

Softer lumps formed without contact with water (airset cement) or cement compacted by its own weight when stacked high or on an exceptionally long shipping period (packset cement) are usable provided that the lumps are not too hard. The normal test involved crushing between the finger and thumb. The powder from split bags should be carefully swept up, excluding paper dunnage or extraneous matter, and rebagged. Extra empty bags are usually provided for the purpose. Rebagged cement is usable for all but the most critical work. Cement clinker is the semi-manufactured material, usually very hard grey granules between 1 and 20 mm in diameter. It is substantially unaffected by water but should be kept dry to avoid caking. Contamination with sea water will increase the chloride content of the clinker and the cement produced from it.

Full information on this product is in the process of completion.