All About Wet Mix Macadam

John Macadam gave the WMM road construction technique. Lately this method is used as mentioned below.

For Wet Mix Macadam Construction We Utilize Three Materials:

  • Aggregates
  • Screeners
  • Binders


For the development of the Wet Mix Macadam streets, aggregates are utilized as a part of base, second base, and also the course of surface thus they are separated into 3 levels as per their size.

Category 1 – Size 90-40 mm particles.

Category 2 – Size 63-40 mm particles.

Category 3 – Size 50-20 mm particles.

The category 1 aggregates of size 90 mm – 40mm are most favored as the element of material for the second base and category 2 is chosen as the primary base & category 1 is chose as the course for the surface. However, on the off chance that we make use of  WBM as the element for the course of the surface, there are chances that as a result of the scrapes spot with the movement that it gets decayed quickly, hence its a general practice to make use of bituminous for the surfacing.


Aggregates of smaller size are known as screeners are, they are basically of size 12.5 mm/10mm, for category A and category B. Because they have this characteristic of indistinguishable synthetic arrangement form just like aggregates that are coarse.

Keeping in mind the financial planning, non plastic material utilization is recommended, for eg, burnt blocks that are crushed over, gravel, moorum, and so on that results in the material’s liquid as under 20%, PI is below 6.0%.

On the off chance that the crush-able type of aggregates are being used, then the use of screeners may be stopped.


Once after the aggregates are compacted and the materials are screened one by one the coating that is put is called Binders.

As a part of surface course development, the coupling material that consists of a PI of 4% – 9% is made use of. On account of the WBM layers, the course material’s PI is supposed to be below 6% that is utilized with bituminous surfacing as the base course/sub-base.

However, there is no compelling reason to apply the coupling material, on the off chance that screening utilized consists of material that are crushable like soft gravel/moorum, provided the PI value is low.

Road Construction with Wet Mix Macadam:

Aggregates utilized are of smaller sizes, that shifts between 4.75 mm – 20 mm & folios are mixed prior using a mixing plant/mixing machine. After which, for overlaying and compaction they are moved to the construction site.

Since the coupling material is supposed to be of a sound and non plastic material, the PI of the coupling material is low. On the off chance that the PI value is more at that point there are odds of swelling and need for more water maintenance characteristics. Hence the value is ought to be remembered.

Difference of WBM and WMM Road Construction:

Points of difference are mentioned below:

The WMM street are more sturdy.

WMM streets are soon prepared to be finished with layers of Bitumen.

WMM streets are developed at a quicker pace.

Water usage is less in WMM road construction

Stone aggregates utilized as a part of WBM is more in size that changes from 90mm – 20mm contingent on the category.

Materials utilized as a part of WBM are stone aggregates, and as in WMM the material utilized are just stone aggregates & folios.

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