Common defects - bituminous roads:
Cracks can be filled with a bitumen emulsion. Wide cracks can be filled with premix sand asphalt.
If an overlay is to be laid on a cracked surface, it is necessary to ensure that the cracks do not travel upwards in the newly laid material. For this purpose, a Stress Absorbing Membrane (SAM) layer or a Stress Absorbing Membrane Interlayer (SAMI) is used. SAM is an application of polymer modified bitumen and covering it with aggregate chips. SAMI is similar to SAM but is followed by an overlay. SAMI can consist of polymer modified bitumen or bitumen impregnated geotextile.
When cracks are extensive, it is preferable to treat the area with a fog seal or slurry seal. The fog seal consists of spraying a bitumen emulsion followed by blinding with graded grit of size 3 mm and lower sizes. A slurry seal is a mixture of fine aggregate, Portland cement filler, bitumen emulsion and additional water, mixed in a mobile mixer and laid to a uniform thickness of 1.5 mm - 5 mm and rolled.
When the surface of the bituminous carpet is loose or has got oxidized, it is necessary to renew the surface by a thin course, consisting of surface dressing, premix carpet, mix- seal surfacing and a semi-dense carpet, depending upon the traffic and importance of the road. The renewal is done once in 3 to 5 years. The renewal helps in restoring the riding quality.
If the surface becomes fatty, a sprinkling of coarse sand or fine chippings and rolling will help.
If the surface becomes very smooth and slippery and has lost its skid-resistance properties, an application of surface dressing can restore its anti-skid properties.