INTRODUCTION 
This report presents a method for placing fresh concrete in situ at 
ocean depths as great as 20,000 ft. The method integrates existing 
hardware systems that are used daily by the concrete construction industry 
and offshore oil industry. The concrete materials are handled, mixed 
and conveyed on a surface vessel using conventional equipment. A drill 
pipe suspended from the surface vessel is used to transport the concrete 
to the seafloor. The pipe is handled, positioned and stabilized using 
techniques employed on drill ships. The concrete flows down the pipe 
under the force of gravity while the descent rate is controlled by 
friction. No valves or constrictions are used in the pipeline for flow 
control as these techniques may cause blockage in the line. By properly 
selecting the diameter of the pipe for particular concrete mixes and by 
assuring that the pipeline remains full at all times, it appears that 
concrete can be placed reliably at deep ocean depths. 
The proposed method would greatly extend the state-of-the-art 
capability to place concrete in the deep ocean. Presently available 
methods provide the following capabilities: concrete can be placed on 
the seafloor or in open forms in water depths to about 400 feet; grouts, 
which are cement slurries or cement-sand slurries, can be placed underwater 
in open forms to similar depths; also grouts can be placed underwater at 
much greater depths, thousands of feet, but only if placed in confined 
spaces where the flow can be controlled by back pressure, as in an oilwell. 
In general, for most structural applications concrete is superior to 
grout and costs less. Concrete, which contains larger aggregates than 
grout, has better structural properties, is heavier and in some cases 
can be placed without forms which would result in major cost savings. 
A modest development effort is required to validate certain engi- 
neering assumptions in the proposed concrete placement method. One 
basic assumption is that a proper mix design can be obtained such that 
the concrete will have the proper friction head loss properties while in 
the pipeline and coherent mounding behavior when discharged from the 
pipeline. Another assumption is that friction values for a given mix 
design can be determined by laboratory tests prior to an operation so 
that the pipe can be sized properly. These and other assumptions will 
be discussed in more detail. Validation of these items is considered to 
be a low risk research effort. 
Advancing the technology to place concrete on the seafloor will 
considerably expand the Navy's capabilities to perform ocean engineering 
tasks. Several potential applications and the benefits of this new 
capability are discussed in the next section. 
