Cement is best stored and transported in bulk in closed tanks, 
commonly available in sizes up to 3,000 cubic feet. Cement is readily 
conveyed pneumatically through standardized hoses and pipes at 20 to 40 
psi air pressure. Offshore supply boats are characteristically outfitted 
with several pressurized tanks of up to 1,000 cubic feet each, and 
associated air compressors and piping; additional tanks can be loaded on 
the deck. A large drill ship will have 10,000 to 25,000 cu ft of bulk 
cement storage capacity. 
About three-fourths of the required materials storage weight and 
space capacity is needed for the aggregates of which there will normally 
be at least three sizes: a sand and two sizes of coarse aggregate. 
Established methods for waterborne transport and handling of heavy 
materials will be used. Aggregates will be stored in low rise bins in 
holds or on deck and moved horizontally and vertically by conveyer belts 
and bucket elevators. 
The proposed concreting method requires careful control of the 
concrete properties which depends, in turn, on close control of the 
water content and the salt content of the aggregate. Therefore, covered 
storage is preferred, especially for the sand, to protect it against 
wetting by waves and spray. 
Water tanks and pumps are standard items. Water must be clean and 
not contaminated with oil or other substances. For applications requiring 
large amounts of concrete, the use of seawater as the concrete mix water 
would preclude the need for large water tanks and could be used with 
sufficient prior testing. However, fresh water is usually preferred as 
a mix water since the properties of the fresh concrete are usually 
easier to control. A large drill ship will have 45,000 to 85,000 cu ft 
water storage capacity. 
Batching and Mixing Equipment. A portable central-mix concrete 
plant would be set up on the deck of the ocean platform. The plant 
should have an automatic positive batching and mixing system with operator 
override so that all operations, particularly mix time and discharge 
from the mixer, are under full control of the operator. Cement and 
aggregates would be batched by weight, water by weight or volume so long 
as the method is accurate and dependable and continuously adjusts the 
amount of added water to automatically compensate for variation in the 
water content of the sand. Admixtures will be precisely dispensed 
either wet or dry in a manner to assure uniform distribution throughout 
the mix. The concrete will need to be well mixed; this may require a 
longer than usual mixing time. The mixer will discharge into a holding 
hopper of the pump. 
One of the most important attributes of the overall material handling 
and concrete batching and mixing system is the capability to produce a 
uniform concrete, particularly in terms of density and slump, under 
varying rates of production. 
Concrete Pumping and Transporting Equipment. The concrete pump 
should have a high pressure rating (say 1,000 psi) and a large capacity 
(say 100 cubic yards per hour), but still be capable of operating effi- 
ciently in its low capacity range. 
