A concrete mattress is a fabric form, fixed to the seabed and pumped full of concrete underwater, where it cures into a thin, continuous slab. A sealed alternative to rock armour for scour and erosion protection, installed without heavy marine plant.
If rock armour is your reference point, three things are worth understanding first. The variants further down make sense once these do.
A woven fabric envelope is fabricated on land to the geometry of the structure, lowered to the seabed by divers, and pump-filled with a fluid micro-concrete from the surface. The fabric retains the sand and cement while excess water escapes; internal ties hold the top and bottom faces together so the slab cures to a controlled, even thickness.
Propeller and thruster wash, currents and wave action strip the seabed at berths, revetments, piers and pipelines, undermining the structures above. A sealed concrete mattress armours the bed so the energy passes over a continuous slab instead of mobilising the ground beneath it.
Rock armour is a sound default where there is depth and room for it. Where there is not, a mattress does the same job as one interlocked apron at a fraction of the thickness, sealed at every edge, and installable beneath a live piled deck without stopping the works above.
Installation is carried out underwater, without heavy marine plant. Divers position and connect the panels; the concrete is pumped and controlled from the surface, with our engineers supervising on site.
Step 01
The woven envelope is cut and sewn on land to the exact geometry of the berth, flat panels for quay walls, sleeves around pile clusters, tapers for sloped beds.
Step 02
Fluid micro-concrete is pumped from the quay or deck through filler sleeves. The porous fabric holds the solids; excess water passes through. No batching at the seabed.
Step 03
The concrete sets inside the envelope as a controlled-thickness slab. Adjacent panels are joined with zipped shear joints, forming a single slab over large areas.
Same insitu technique, six forms tuned to the loading. We specify the right one for your structure; the ranges below are starting points, not a menu.
Constant Thickness
The default mattress: slabs of even-thickness plain concrete, filled to full thickness on slopes and uneven surfaces. Woven 5 m wide, with zipped shear joints locking panels into a single slab over large areas.
Quay walls · piled revetments · bridges
A CT mattress with prefabricated open holes providing porosity in wave zones. Water releases through the holes during wave run-down, avoiding uplift pressure; hole size and frequency are designed to the location.
Revetment slopes · wave heights to 2–3 m
Constant Thickness Bulk
A two-layer porous fabric with internal fabric thickness columns, producing plain slabs up to 1.2 m thick. Made bespoke for the required height and volume, for breaking-wave protection and heavy bed protection.
Caisson breakwaters · wave walls · temporary tunnelling protection
Flexible
A CT mattress with a grid pattern of reduced thickness, letting the slab flex and follow ground that settles after installation, for slopes and beds of hydraulic fill that are slow to compact.
Hydraulic fill · settlement-prone slopes and beds
Jute Open Hole
An open-hole mattress tailored from natural jute fibre that decays after the concrete cures, leaving a surface that silts in and supports vegetation and habitat, for environmentally sensitive schemes.
Riverbanks · green revetments · wave heights to 1–1.5 m
A double-layer fabric woven together at regular intervals to form filter points that act as weep holes in service, relieving uplift from behind the slab while retaining fines. Supplied in panels typically 3 m wide.
Revetments and slopes with high groundwater or wave pumping
Adjacent panels are zip-connected along their top and bottom edges by divers. When the panels are pump-filled, concrete fills the connection and cures into a ball-and-socket shear joint.
Shear transfers across every joint, so whichever variant is specified, the finished protection behaves as a continuous interlocked apron, not as individual units.
The image below shows both systems on adjacent berths at the same port. The table summarises where each one earns its place.
← Rock armour
Concrete mattress →
Rock figures are the equivalent specification for Al Faw Grand Port: 1.8 m armour, 1.0 m underlayer, 0.8 m filter — around 430,000 m³ of imported rock avoided across 120,000 m². Rock armour remains a sound specification on greenfield sites with depth to spare.
The mattress is not a proprietary black box. Its design basis is in the open literature, the same papers your reviewers can read.
Hydraulic research underpinning scour prediction and bed-protection design at marine structures.
Three generations of Proserve engineers on propeller action, berth scour and concrete-mattress design.
Berth scour assessment and protection designed to current PIANC guidance for propeller and thruster loading.
PIANC
PIANC
ICE
The application family overview: the problem, the comparison with rock armour, and the research.
ExploreSealed protection at vertical walls. 220–300 mm, installed from the quay side.
ExploreSlope protection beneath piled decks. 220/150 mm, installed under the completed deck.
ExploreAn in situ concrete mattress is a woven fabric formwork laid on the seabed and pump-filled with micro concrete, curing into a continuous concrete apron that protects against scour and erosion.
Proserve mattresses conform to the seabed and connect into a sealed system around walls, piles and edge details. Standard types give filled thicknesses of roughly 115–575 mm, woven in panels commonly 5 to 7.5 m wide.
Divers roll out the fabric formwork on the seabed, connect the panels, and the mattress is pump-filled with micro concrete from the quayside, no marine plant or heavy lifting is needed.
The woven fabric holds the fluid concrete in place and protects it from washout while it cures into one continuous slab. With suitable training, installation is possible in low visibility and even black water.
For many marine structures, yes. An in situ concrete mattress is up to seven times thinner than equivalent rock armour, installs from the quayside without marine plant, and forms a single sealed apron that conforms to the seabed.
Rock relies on individual stones staying put, and usually needs topping up over time. Rock armour still has its place, but where clearance, access or maintenance matter, the mattress is often the more practical build.
Quality is controlled through Proserve’s Marine Quality Control System: a Flowcone fluidity test on every concrete batch, strength samples taken in test socks, and sonar surveys of the seabed before laying.
During filling, pre-pour checks are signed off and fill rates are monitored throughout. As-built records are produced for the owner’s future inspection and maintenance.
Proserve mattresses are installed by the contractor and their divers, with training and on-site support from Proserve’s engineers throughout the project.
Proserve provides installation guides, filling plans and training presentations, and runs demonstration fillings before live work starts. On large projects, engineer visits continue at regular intervals, typically every 10,000 m² installed. Divers new to the technique are trained first.
Download the design guide and check it against your own numbers, or send the basics of your section and we’ll come back with an indicative quantity and budget.
