Precast Kerb Installation Guidelines
The guidelines below are largely based on SANS 1200MK, the official South African Standard for the installation of precast concrete kerbs.
As SANS 1200MK was last updated in 1983, we have also included key points from the British standard for the installation of precast concrete kerbs.
The following is stipulated in SANS 1200MK:
- Trenches for kerbs and channels shall be excavated to the correct depth.
- Bedding material is to be crushed stone, cinders, slag, sand or other approved porous material having a maximum particle size if 13,2mm.
- This bedding material should be placed on a compacted subbase (90% of modified AASHTO.)
- Units shall be laid with joints not exceeding 10mm.
- 3:1 sand cement mix will be used to joint the kerbs. The ends of the units will be well moistened before jointing. Joints will be covered and kept moist for 40 hours after installation.
- Provision shall be made for expansion joints at least every 20m.
- Expansion joints will be filled with a suitable sealant.
- After grouting the kerb joints, the kerbs shall be backed with concrete with a strength of 15MPa.
- The backfill behind the kerbs needs to be compacted to 90% of modified AASHTO.
The British Standard stipulates:
- The subbase should extend to behind the kerbs to be installed.
- Kerbs should be installed on a concrete bed which is on top of the subbase mentioned above.
- Kerbs should be backed by concrete and not only haunched with concrete behind their joints.
Bosun recommends the following:
As the British guidelines suggest, it is common practice in South Africa to use a concrete foundation for precast concrete kerbs. This is recommended by Bosun.
It is important to fill expansion joints with a suitable sealant in order to prevent bedding and jointing material of segmented paving behind the kerbs seeping out of empty expansion joints.
Precast kerbs are commonly installed in combination with cast in situ channels. Bosun recommends the use of precast channels which eliminates many issues caused by cast in situ channels.
However, if channels are cast in situ, precast kerbs should be covered in order to protect them against concrete splatter. It is also recommended to protect kerbs against asphalt splatter.
Kerbs generally weigh in excess of 100kg per unit. Bosun actively promotes the use of specialist handling tools in order to protect workers on site.
These tools are available from www.cretesol.co.za