Sitework
Installation Instructions For Heavy Duty Applications
The following installation procedures are for guidance only, and the person or organisation responsible for the structural design of the adjacent works should satisfy themselves of the suitability of any details for their particular situation.The following notes apply to the use of ALTHON GRC Channels, GRC Forma D400 Lids and Precast Lids.
Installation of Channels
1. Excavate trench to line and level, having due regard for the size of the channel unit to be installed.
2. Ensure that there is a firm foundation to the bottom of the trench; otherwise seek expert geotechnical advice. Place 150mm minimum concrete grade ST4 in the bottom of the trench. If aggressive chemical conditions exist in the soil or ground waters, an enhanced concrete to suit must be specified.
3. Starting at the outfall end, lower the first channel unit onto the ST4 bedding, then dry joint successive units. Alternatively, depending on the ground conditions, a trowel grade mastic can be used between adjacent units. Line and level the units with laser or other appropriate technique using the minimum solid packing under
the channel.
4. Place ST4 grade concrete backfill surround to the channel, tamped or rammed as necessary to fill all voids, and finishing with a haunch 125mm to 250mm from the top level of the channel as shown in Figure 4.
Installation of Forma Lid Unit
1. Bed the GRC lid liners into the channel rebates, using Althon High Strength Bedding Mortar. The bedding should be for the full width of the rebate and continuous along the channel.
2. Place the ALTHON supplied pre-fabricated reinforcement cages over the FORMA Lid Unit; the transverse bottom bars sit on the GRC ribs, (see diagram) of the FORMA Lid.
3. The longitudinal bars in the cages are to be lapped by a length of 40 x the diameter of the bars and firmly wired together.
4. Top up the channel surround using paving quality concrete Applicationsand then cast the in-situ reinforced concrete lids to the widths specified in Table 1. If greater widths are required, the designer must provide details of the reinforcement etc to ensure correct performance of the lids.
5. Ensure that the lid concrete is fully compacted, care being exercised to avoid damage to the GRC lid liners.
6. Care must also be exercised to prevent concrete spillage down the pre-formed slots that could block the slots or the channels. Plastic caps are supplied for this purpose.
7. Appropriate curing regimes should be adopted depending on the climatic conditions to ensure full strength development in the concrete before traffic is allowed on the lids.
Movement Joint
1.Transverse movement joints with 10mm thickness of compressible material through both the in-situ lids and the concrete surrounding the channel should be provided at approximately 10.0m intervals, unless the hard standing designer specifies otherwise.2. The exposed joint on the top surface must be sealed with grey polysulphide sealant, applied in accordance with the manufacturers’ instructions.
Rodding Positions - Forma D400
Silt Pits should be positioned at the head of each run for rodding purposes.Installation of HB, EHB or XHB Lid Unit
1. Bed the lid on the Channel Unit using Althon High Strength Bedding Mortar.
2.Top up the Channel surround using paving quality concrete ensuring that the concrete fills all voids on the underside of the lid.
3. An expansion/contraction joint should be placed parallel to each side of the lid unit at a minimum distance of 500mm.
Rodding Positions - HB/EHB/XHB Lids
Lid Units with cast in rodding eyes should be positioned at the head of each run for rodding purposes.
Althon Bedding Mortar
Althon Bedding Mortar is a fully pre-mixed dry-pack and only requires the addition of water on site. It should be applied in a thickness of 10-15mm between the top rebate of the Althon Channel and Lid Unit. Althon Bedding Mortar achieves exceptional bonding strength without shrinkage. Althon Bedding Mortar is available in 25kg poly tubs and usage rates are as follows:
Forma D400 Lids – 1 Tub per 10m of channel. All other Lids – 1 Tub per 5m of channel.
Download Althon Bedding Mortar datasheet
Download Althon Bedding Mortar Health & Safety datasheetInstallation Instructions For Standard Applications
Installation Method for Channel and Lids.
1. Excavate trench to line and level, having regard to the size of unit to be installed.2. Concrete the bottom of the trench with 75mm minimum thickness ST4 concrete on firm foundation.
3. Starting at the outfall end, lower the unit carefully onto an ST4 bed.
4. Dry joint successive channel units. Depending on ground conditions mastic can be used to seal joints on
engineers recommendations.
5. Align channels by using laser or similar instrument.
6. Concrete surround to top level of channel rebate and allow to cure.
7. Bed lid on to channel with class 1 mortar with 10-15mm bed ensuring that the bedding is on both levels of rebate.
8. Bring up road base and finished pavement to sides of lid, or over lid where appropriate.
