Cement is a major dry bulk cargo, with global seaborne trade of approximately 60 to 80 million tonnes per year of finished cement plus a similar volume of cement clinker and supplementary cementitious materials. Cement seaborne trade flows principally from large producing regions including Northern Asia (China, Vietnam, Thailand, Pakistan, Iran), the Mediterranean (Türkiye, Greece, Spain), and the Middle East (UAE, Saudi Arabia) to markets in Africa, the Americas, and the Pacific that have insufficient domestic production. The cargo is regulated under the International Maritime Solid Bulk Cargoes Code (IMSBC) and is classified Group C: not liquefiable, no chemical hazard, but with handling requirements driven by dust emission, moisture sensitivity, and the powder’s high flowability.
Schedule structure
The IMSBC Code provides separate schedule entries for cement product cargoes:
- Cement (calcined Portland cement and similar finished cementitious binders). Group C.
- Cement clinker (the unmilled intermediate product). Group C with separate handling considerations.
- Cement copper (a metallurgical by-product, unrelated to construction cement; mentioned here only to avoid confusion).
This article covers finished cement; cement clinker is covered in a separate IMSBC schedule article.
Cargo properties
Portland cement is a fine grey powder produced by grinding cement clinker with a small percentage of gypsum. Particle size distribution is centred around 5 to 30 micrometres, much finer than alumina or other typical bulk powders. The bulk density of cement as loaded is approximately 1.3 to 1.5 tonnes per cubic metre, with a stowage factor of approximately 0.7 to 0.8 cubic metres per tonne.
The principal handling concerns for cement are:
- Moisture sensitivity: cement begins to hydrate on contact with liquid water, forming hard lumps that are difficult to discharge and are commercially unacceptable. The cargo holds must be clean, dry, and weather-tight, and bilge wells must be inspected and dried before loading.
- Dust generation: cement dust is fine, alkaline, and a respiratory hazard. Loading and discharge operations require dust suppression at all transfer points and dust collection systems on the shiploader, conveyor, and unloader.
- High flowability: cement is highly flowable and may run out through small hatch gaps, ventilator openings, or bilge well leakage points. Hatch and seal integrity is critical.
- Compaction during voyage: cement compacts under ship motion to bulk densities approaching 1.6 tonnes per cubic metre, which can complicate discharge if the unloader is not capable of breaking up compacted material.
Bulk cement carriers
A significant portion of cement seaborne trade moves on dedicated cement carriers — specialised vessels equipped with fully enclosed loading and pneumatic discharge systems. These vessels are generally in the 5,000 to 30,000 deadweight tonne range and feature multiple compartments, integral conveyor and screw discharge systems, and pneumatic blowers that fluidise the cement and inject it into shore silos via flexible discharge hoses. The discharge rate of a bulk cement carrier is typically 300 to 800 tonnes per hour, slower than grab discharge of conventional bulk carriers but with no dust emission and direct delivery to shore silos.
Conventional bulk carriers also carry cement, particularly on long routes from Asia to West Africa, the Caribbean, and Pacific island states where receiving terminals do not have dedicated cement infrastructure. Discharge in such cases is by grab-fitted shore cranes with covered hopper systems to limit dust emission.
Loading procedures
Cement is loaded by enclosed shiploaders with dust filtration. The cargo is delivered from shore silos via pneumatic or screw conveyor systems and discharged into the hold through the loader spout. Loading rates of 800 to 2,000 tonnes per hour are typical depending on shore equipment.
Critical pre-loading checks include:
- Hold cleanliness: complete absence of moisture, prior cargo residues, salt, or oil. Holds are typically washed and dried, and bilge wells are inspected and dried.
- Hatch cover integrity: comprehensive water test of hatch covers, seals, and access hatches.
- Bilge well operation: bilge well alarms tested and verified.
- Ventilation closures: all hold ventilators sealed against rain ingress.
Cement that contacts liquid water during loading or voyage forms hard hydrate lumps that significantly degrade product value and may render the entire shipment commercially unacceptable. Many cement charter parties impose strict dryness warranties and provide for cargo claims if moisture damage is found at discharge.
Voyage handling
During the voyage the cargo is generally not ventilated. Hatch covers remain closed and sealed. Hold atmosphere may be monitored for humidity if the voyage crosses humid tropical zones, though direct moisture-prevention measures (sealed hatches, sealed ventilator openings) are typically sufficient.
Discharge
Pneumatic discharge from a dedicated cement carrier proceeds at controlled rates under operator supervision. Conventional bulk-carrier discharge by grab and covered hopper proceeds at slower rates with greater attention to dust suppression. Receiving ports typically have shore silos with capacity matched to the discharge rate, and the cement is then distributed inland by tanker truck or rail wagon for use in concrete production.
Comparable cargoes
Cement shares many handling characteristics with alumina (both Group C, both fine flowable powders) but differs in moisture sensitivity (alumina is moisture-tolerant; cement is moisture-reactive) and in the increased prevalence of dedicated cement carrier vessels.