In some cases, sites that need erosion control are difficult to reach or submerged under water. With this in mind, Terraforce recently developed pre-assembled inter-linked Terracrete mats, that can be installed by crane.
The mats are produced using a wet cast method with custom designed Terracrete moulds that are made of durable, non-stick Polyethylene and weigh between 2 and 3 kg each. The moulds are then drilled (with a long drill) with 10 mm holes at predetermined positions, to accommodate 10 mm steel rods with handles.
Next they are filled with a relatively dry 35 Mpa. concrete mix (cube strength) on a vibrating table, the steel rods are withdrawn, and the mould box is turned over on a smooth surface, and de-moulded. Finally the finished block is pressed lightly with a 400 x 400 mm plywood pallet to even out the top surface and close off any hairline cracks that may have formed due to deforming.
After curing for 21 days, the blocks are ready for testing and should achieve 25 Mpa. crushing strength and are ready to be assembled into a mat, using two 2mm steel or stainless steel wires, threaded through the horizontal holes.
Mat size may vary, from 1,6 x 2,7m to 1,9 x 3,5m approximately, depending on site conditions and nature of lifting gear available. The blocks can also be wired together after placement, if necessary.Refer to TERRANeWS 12/2005 – Erosion Control on Sloping Bank Profile.