Production & placement
Although both wooden and steel moulds can be used to construct the Xbloc® formwork, steel moulds are preferred as they can be used repetitively to produce large numbers of units. Due to the shape of the Xbloc® unit, a relatively simple formwork can be used which is made of a limited number of different steel plates.
Several mould designs have been developed, consisting of either 2 or 3 sections. The choice of casting method can therefore be chosen according to the preference of the contractor for each site. Because of large fill openings in the formwork, pouring and compacting of concrete is straightforward and can be well controlled. In several projects efficient production was achieved by pouring from the concrete mixer in to the mould from an elevated road.
Typically casting turnaround times of 1 Xbloc per mould per day are achieved. In warm climates, with special measures, turnaround times of 2 Xblocs per mould per day can be achieved. This has for instance been done at Bar Beach, Lagos, Nigeria.
At Port of Poti symmetrical mould halves have been used, whereby the mould halves where turned around after striking the mould, for immediate re-use. At other locations concrete with fast strength development has been applied which allows removal of the Xbloc from between the mould halves within 24 hrs after casting.
For Xblocs a concrete grade C25/30 is used with a minimum tensile strength of 2.5 N/mm2 at 28 days (tensile splitting strength)
Handling
In the construction yard the Xbloc® units can be handled with the aid of a fork, a clamp or a sling. Typically wheelloaders equipped with a fork are used.
Storage
The units can be stacked in various ways for storage, for example side by side in a half-brick bond (see photo). The storage pattern can be arranged in 1 to 3 layers, depending upon the capacity of the subsoil. Using this pattern, the required storage area amounts to 0.72 D2 for 1 layer storage and 0.36D2 for 2 layer storage [D = unit height]. It should be noted that this area still allows for some space between the Xbloc units. This faciltates easy removal from storage.
The minimum storage area for single layer storage is 0.59 D2. In this case the Xblocs will be touching each other.
Placement
During placing of the units on the breakwater there are no restrictions on the Xbloc® orientation, only on the packing-density achieved on the slope. The recommended packing-densities can be found in the design table.
Based on several projects the placement rate of Xbloc® armour units lies between 8-25 units/hour. The Xbloc® units can be placed by an excavator or a crawler crane. Xbase® toe units facilitate easy placement of the armour layer.
At Port Oriel, Port of Poti and other Xbloc projects, excellent placement rates have been achieved with the use of an excavator (see photo and videos).
