The CORE-LOC™ unit
The CORE-LOC™ unit was developed in 1996 by the US Corps of Engineers (USA) with the initial objective of repairing armour facings made with Dolos units. Since then, the unit has been widely used as a main protection system for maritime structures. As is the case with all CLI armour units, it has a high stability coefficient and a high porosity ratio derived from its shape as well as from the associated placing techniques.
It can be used on structures of all types on sites exposed to moderate waves, from coastal defences in shallow water to large structures. This is a technology with minimal maintenance costs since these structures are normally intended to withstand the design wave without sustaining damage. CLI is the exclusive distributor of this technology in a certain number of countries.
Practical aspects of CORE LOC™ units
1. A simple formwork principle based on:
- Two steel symmetrical half-shells that are assembled for easy concrete casting through the top.
- Simple fabrication, avoiding the need for leading-edge technologies.
- A proven shape ensuring seamless stripping.
2. Concrete strength specifications that are simple and open to the continuous improvements being made to this technology
The concrete used for CORE-LOC™ units is a simple mass concrete that is by its very essence less costly than the high-performance concretes. The specifications for producing this concrete are brief, to leave the project players free to choose the concrete characteristics best suited to their project.
As stated in the specifications, CLI has confirmed on the basis of experience that the following characteristic strength values give a safety factor that is sufficient for the construction phases and during the working life of the structure:
| CORE-LOC™ | For all unit sizes |
| Concrete class required | C35/45 |
| Tensile strength Fctm | 3.5 MPa |
| Minimum strength for form stripping Fck Cyl | 10 MPa |
| Minimum strength for handling Fck Cyl | 25 MPa |
| Minimum strength for placing Fck Cyl | 35 MPa |
3. Unit fabrication
Fabrication of CORE-LOC™ units is a simple process calling on methods that are either highly rudimentary or, conversely, highly sophisticated. With the traditional fabrication method, the following parameters are adopted:
- Minimum area required to fabricate one unit: 1.65C² (where C = CORE-LOC™ unit height).
- Fabrication of one unit per day and per mould.
4. Storage and handling
- Forklifts can be used to transport the units. For some very large units, handling equipment such as cranes and slings will be required.
- Units can be stored with precautions on one or two levels depending on their size, on levelled ground with a sufficient bearing capacity.
- Minimum area required to store 10 units on one level: 5.2C² (where C = CORE-LOC™ unit height).
5. Unit placing
CORE-LOC™ units are placed using a grid that defines their theoretical target position in order to ensure easier placing. According to the feedback we have received, this ensures that the packing density required by the technique is obtained. Today, DGPS / GPS RTK-type positioning systems are systematically used. Unit keying is achieved easily thanks to the random orientation of the units. The unit placing speed is determined by the resources used, which must take the weather conditions at the site into account. The use of a hydraulic shovel and a special grab can double the standard output of a cable crane.
Placement rate (using cable cranes) – monthly average
| Unit sizes | Average placing time per unit |
| Small | 5 to 8 min |
| Medium | 8 to 10 min |
| Large | 10 to 15 min |
Higher rates can be obtained using a “custom” method.
Using the CORE-LOC™ technology in association with technical assistance geared to the construction site makes it possible to:
Control and reduce the cost of building the facing, by using a well-proven technology.
Reduce environmental impacts by limiting the footprint of the structure.
Control and reduce the volumes of materials required, especially concrete.
Minimise risks and construction times, enabling the structure to be put into service more quickly.
Significantly reduce the costs of inspecting and maintaining the structure throughout its working life.
