Road joints
Contents |
[edit] Introduction
Joints are formed in concrete slabs as part of the process of constructing rigid paving for roads. Joints are discontinuities in the pavement slab that are necessary to allow for expansion, contraction and warping. Rigid paving consists of a reinforced or unreinforced insitu concrete slab laid over a thin granular base course. The rigidity and strength of the pavement enables the loads and stresses to be distributed over a wide area of the subgrade.
Joints are spaced depending on a range of factors:
- The amount of reinforcement used.
- The proposed traffic intensity.
- The slab thickness.
- The frictional restraint of the subgrade.
- The temperature at which the concrete is laid.
Joints comprise a filler which separates the slabs, and a sealing compound which is used to fill the top 25 mm of the joint to prevent the entry of water and grit. Suitable jointing materials include impregnated fibre board, cork, sheet bitumen, and rubber. The joint sealing compound must have good adhesion to concrete, extensibility without fracture, resistance to flow in hot weather, and durability.
A system of dowel bars in introduced between slabs to prevent slab movement and ensure load-transfer. Dowel bars are positioned at mid-depth of the slab at centres of 300 mm. The diameter of the bar usually ranges from 20-30 mm but varies with the slab thickness. A plastic sleeve 100 mm-long is inserted on one end of the dowel to allow free movement of the slab. The sleeve should contain a pad of compressible material at the end.
[edit] Types of road joints
There are a number of different types of joints:
[edit] Expansion joint
These are provided along the transverse direction to allow the expansion and contraction of a concrete slab due to temperature and subgrade moisture variation. They are intended to prevent potentially damaging forces accumulating within the slab itself or surrounding structures. Maximum spacing of expansion joints range from 25-27 m in jointed reinforced concrete slabs, and from 40 m (for slabs <230 mm thick) to 60 m (for slabs >230 mm thick) in unreinforced concrete.
[edit] Contraction joint
These are also known as ‘shrinkage’ joints and are provided along the transverse direction to allow for contraction or shrinkage of the slab during the curing process. Maximum spacing of contraction joints ranges from 12-24 m in reinforced slabs, and from 4-5 m in unreinforced slabs.
[edit] Construction joint
Construction joints are provided whenever the construction work stops temporarily. They can be either along the transverse or longitudinal direction.
[edit] Warping joint
Warping joints are provided along the longitudinal direction to prevent warping of the concrete slab due to temperature and subgrade moisture variation.
[edit] Related articles on Designing Buildings
- Bituminous mixing and laying plant.
- Code of Practice for Ironwork Systems Installation and Refurbishment.
- Highway drainage.
- Joint v connection.
- Kerbs.
- Overview of the road development process.
- Pavement.
- Road construction.
- Runway construction.
- Settlement.
- Types of road and street.
[edit] External references
- ‘Introduction to civil engineering construction’ (3rd ed.), HOLMES, R., The College of Estate Management (1995)
Featured articles and news
The 5 elements of seiri, seiton, seiso, seiketsu and shitsuke.
Shading for housing, a design guide
A look back at embedding a new culture of shading.
The Architectural Technology Awards
The AT Awards 2025 are open for entries!
ECA Blueprint for Electrification
The 'mosaic of interconnected challenges' and how to deliver the UK’s Transition to Clean Power.
Grenfell Tower Principal Contractor Award notice
Tower repair and maintenance contractor announced as demolition contractor.
Passivhaus social homes benefit from heat pump service
Sixteen new homes designed and built to achieve Passivhaus constructed in Dumfries & Galloway.
CABE Publishes Results of 2025 Building Control Survey
Concern over lack of understanding of how roles have changed since the introduction of the BSA 2022.
British Architectural Sculpture 1851-1951
A rich heritage of decorative and figurative sculpture. Book review.
A programme to tackle the lack of diversity.
Independent Building Control review panel
Five members of the newly established, Grenfell Tower Inquiry recommended, panel appointed.
Welsh Recharging Electrical Skills Charter progresses
ECA progressing on the ‘asks’ of the Recharging Electrical Skills Charter at the Senedd in Wales.
A brief history from 1890s to 2020s.
CIOB and CORBON combine forces
To elevate professional standards in Nigeria’s construction industry.
Amendment to the GB Energy Bill welcomed by ECA
Move prevents nationally-owned energy company from investing in solar panels produced by modern slavery.
Gregor Harvie argues that AI is state-sanctioned theft of IP.
Experimental AI housing target help for councils
Experimental AI could help councils meet housing targets by digitising records.
BSRIA Occupant Wellbeing survey BOW
Occupant satisfaction and wellbeing tool inc. physical environment, indoor facilities, functionality and accessibility.