In the construction of runways, roads and buildings invovling the costing of concrete slab form provision must be made to accomodate the expansion and contraction which occurs with seasonal variations in temperature.
In tropical countries these variations may be considerable. It is of utmost importance to use correct joint filling and sealing compounds to preserve the life and eveness of the surface.
Normal practise in runway & road construction is to provide both longitudinol and transvers expansion joints of 12mm, 18mm, or 25mm width between butting slabs of reinforced concrete of designed intervals, and at intersections with other construction i.e. bridges, level crossing etc.
2' x 4' or 4' x 4' in 12mm / 18mm / 25mm thickness.
The expansion joints between the slabs must fulfill the following functions:
(a) Permit free movement of the concrete slabs in expansion & contraction.
(b) Provide a water proof seal which will at all times prevent the percolation of surface water downwards, thereby adversely affecting the bearing properties of the subrade.
(c) Resist entry of foreign matter in to the joint space thereby avoiding interference with the free movement of the slabs under expansion & thus preventing damage to the slab.