What are the best steps for bituminous patch repair work?
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Patches are the worst enemy of bituminous road and irritate the road users.
Following are some modern methods for patch repairing:
Generally, a bituminous patch repair work or surface treatment (BST), also known as a seal coat or chip seal, which is a thin protective wearing surface that is applied to a pavement or base course. It can provide all of the following:
a) A waterproof layer to protect the underlying pavement.
b) Increased skid resistance.
c) A filler for existing cracks or raveled surfaces.
d) An anti-glare surface during wet weather and an increased reflective surface for night driving.
A bituminous patch repair work contains the following steps:
1. Surface preparation:- Surface defects, such as potholes, are repaired and the existing surface is cleaned (e.g., by a street sweeper).
2. Asphalt material application:- Typically, an asphalt emulsion is applied from a spray truck to the surface of the existing pavement.
3. Aggregate application:- A thin aggregate cover (only one stone thick) is spread over the asphalt material before it has set. The aggregate usually has a uniform gradation.
4. Aggregate embedding:- A roller (usually a pneumatic tire roller) is used to push the aggregate into the asphalt material and seat it firmly against the underlying pavement. Generally, about 50 percent of each aggregate particle should be embedded in the asphalt material after final rolling. About 70 percent of each aggregate particle will be embedded after several weeks of traffic. It is common to place an aggregate “chokestone” on top of the uniformly graded larger aggregates after embedment. Chokestone is essentially a finer aggregate gradation (e.g., less than 12.5 mm (1/2 inch)) used to make a more dense aggregate matrix at the level of embedment. This more dense matrix helps prevent excessive aggregate loss due to traffic.
Steps of bituminous Pavement repair:
Stage 1: preparation of the cold mix
Stage 2: repairing a pothole
One of ways to repair patch is:
A cut-off saw with dust suppression slices through the old bitmac. The bottle feeds water to the blade to ensure dust is tuned to a slurry. Pumping the bottle recharges the pressure which keeps the water flowing.
Next, a breaker (jackhammer) is used to break up the old surfacing, which is dug out & disposed of safely. The exposed sub-base has been tidied up & compacted.
So now a layer of base macadam is spread out & levelled. The base course (aka binder course) has a chunky 20mm agg for strength.
It is raked out to a level which will allow 25mm of surface course to cover it. Any spilled loose materialis swept off the existing surface & then the roller is brought in to smooth & compact the bitmac.
Note: Water is dripped onto the roller drum so that the bitmac doesn’t stick on it.
It is imp to ensure thorough compaction to minimize later settlement.
Once the base is compacted, the surface course (wearing course) can be added.
For trafficked areas, generally 25mm thk layer is used of the surface course. The surface layer is finer, using 6mm or 10mm hard agg’s to give an even surface & that evenness depends on the skill & dexterity of the rake-hand.
The barrowman brings in hot macadam & places it where directed by the rake-hand who use the rake to spread the material to where its needed, & to level it out. Turning the rake upside down helps to achieve an even & smooth finish & then once again, loose material is swept off the existing surface to prevent it being crushed & damaging the old macadam.
The roller is brought back & used with NO vibration on the first passes, as this helps compact the surface without causingit to stretch. Again, water on the drum prevents the mac sticking to the roller.
Once all the surface has been rolled, the vibration can be switched on to ensure good consolidation. 6-8 passes over each part of the new surface should be adequate
The best steps for bituminous patch repair work are as follows :-
– Clean the patches and debris.
– Make the affected surrounding clean.
– Spray the binder coat at the bottom of patches.
– Fill the patch with asphalt and aggregate.
– Then cover with asphalt binding material.
– Edge seal to repair work.
Bitumen roads can be repaired by