On request Althon can provide detailed installation instructions for all of our precast concrete headwalls.
Installation of Althon precast headwalls is fast, efficient and drastically reduces the need to pour concrete near an open watercourse.
Headwall Installation Guidelines
- Ensure that first or last spigot/butt or socket/butt pipe that is to be fitted to the Headwall is in position and free from backfill.
- Dig out the bank of the watercourse to take the size of the headwall making sure that the Headwall will not protrude into the path of the water flow. The angle of the excavation to the rear of the Headwall should be roughly the same as the existing bank profile.
- Dig out sufficient size trench to take the toe along the front of the foundation.
- Line toe foundation with Geotextile then place selected, uniformly graded granular fill in the base and compact well. Lift Toe into position and level then fill around the toe with selected, uniformly graded granular fill and compact well. Insert supplied threaded rod into the sockets cast into the top of the toe.
- Line the base of the rest of excavation with Geotextile then place a minimum bed of 150mm Class 6A* Selected Well Graded Granular Material on the base & compact well, especially around the back of the toe, then a 50mm blinding layer of sharp sand. Lift Headwall into position, over the end of the pipe & locate over threaded rod protruding from the toe and level. Place washer over threaded rod in recess in Headwall apron and tighten nut. Fill recess with high strength non-shrink grout.
- The pipe should be flush with the front of the back wall if fitting grating or flap valve, or protruding by 50mm if not.
- Shim the pipe until it is central within the opening then fill void with sand cement mortar or high strength non-shrink grout.
- If flap valve or grating is supplied, this will need to be removed before the pipe is inserted and sealed into place. Then reinstall using stainless steel fixing bolts into cast in sockets. (When bolting flap valves against headwall, use a good quality sealant but do not over tighten bolts or distortion may occur resulting in the valve not seating correctly.
- Backfill pipe section first then backfill all around Headwall with as dug material. Make good at front of toe with as dug material ensuring river bank is returned to its original profile. It may be necessary to provide protection in front of the toe, please refer to engineers’ recommendation.
*Manual of Contract Documents for Highway Works: Volume 1 (MCHW1), Specification for Highway Works, Series 600 (Nov 09)
Rapid-Lift Lifting Anchors
Althon headwall and toes which are fitted with Rapid-Lift lifting anchors. The Althon Rapid-Lift system allows the headwalls and toes to be offloaded, transported and located in their final position without the need for any specialised lifting equipment. Standard lifting hooks and chains can be used with the lifting points. The minimum chain leg length for all units is 1500mm.
Lifting Instructions and Equipment for Standard Range Precast Headwalls
Althon headwalls fitted with lifting points and supplied with RD20 threaded lifting loop or RD20 premium swivel lifting eye. Lifting operations must take place on a suitable area of flat and level hard standing. Chains should be left as long as is practically possible in order to minimise the side loading. Chains should be adjusted accordingly to ensure an even lift. Carefully lift the unit until the chains are under tension, if it doesn’t sit level, lower it back to the ground and adjust the chains accordingly, repeat process until you achieve an even lift.
RD20 Threaded Lifting Loop
The Threaded Lifting loop must be fully threaded into the lifting socket prior to commencing a lifting operation. It is imperative that the two mating surfaces are parallel to each other.
RD20 Premium swivel lifting eye
The premium swivel lifting Eye is screwed into the lifting socket. The threaded portion should be turned in until the large base plate makes full and tight contact with the concrete surface. This ensures that no bending of the threaded section occurs during the lifting process. It is imperative that the two mating surfaces are parallel to each other. Once engaged fully the Swivel Lifting Eye can turn in any direction against the base plate, thus ensuring the correct direction of inclined lifting force. Please note that Swivel Lifting Eye should not be utilised to rotate units about the socket axis.
Althon Precast Concrete Headwall Safety Sheet
Althon Limited manufacture pre-cast concrete headwalls using:
6-14mm aggregate, 0/4 Sharp sand, Portland cement BS EN 197-1 Cem 1 52.5 and Cryso Fluid Premia 205 Varit Superplasticiser
When units have been manufactured and cured they are in a chemically inert state but the following information should be considered:
- It is advisable to wear toe cap safety footwear when handling any concrete products. Please refer to your company Safety Policy for specific details on manual handling.
- When cutting masonry grinding discs or drilling with masonry drill bits it is necessary to wear eye protection and a dust mask. It is also recommended to wear ear protection during either of these two processes.
- Due to some units having sharp edges it is advisable to wear protection gloves when handling Althon products.
- When fitting or removing some of the larger accessories it is necessary to use a mechanical system to prevent risk of back injury.
Maintenance of Headwalls
With respect to the maintenance of any exposed surfaces of concrete components, only routine (Annual) cleaning may be necessary with a power washer and possibly some mild detergent to any exposed surfaces to maintain appearance; however all sites are unique and environmental impact of cleaning should be taken into account. Where cleaning is required and environmental conditions prevent mild detergent, using clean water and a power washer/ stiff brush should suffice. Concrete units are often expected to "weather" and some coverage will help them to blend into their environment.
If damage to the structure of any pre-cast concrete components occurs we recommend their replacement not repair. If there is minor damage to corners during their normal life by grass cutting equipment etc. then repair with an epoxy compound such as 'Mason Mate 0868PR380 Polyester Resin'
To dispose of any Pre-Cast concrete components the preferred method is to recycle the material by crushing and grading, but if the quantity is too small to be cost effective then disposal in conventional landfill is acceptable as all the concrete components are inert with regard to having any environmental impact.
Maintenance of Galvanised Grates and Handrails
Annual/bi-annual visual checks are basic recommendations. If gratings are in a water course subject to a higher level of debris/weed, then more regular checks may be required. Clearing of debris/weeds from the grate will ensure no disruption to the flow, or backing up of the water course. Handrails should also only require a visual inspection - annually or at the same time as the headwall and grates.
If you require any assistance or more information please contact us by phone on 01603 488700 or by email email@example.com