Calculation of Loose Thickness from Expected Compacted Thickness of Bituminous layers

In SSR items of Bituminous layers such as DBM, BM, BC and OGC etc. are given in terms of Compacted thickness, as we know these layers need to be rolled by which its resultant thickness reduces.

here  thing is to be noted that there are chances that after immediate rolling by roller, the compacted thickness may further compacted by Traffic over the road surface and hence both compactions need to be considered.

Calculator to be used is as follows-

Step 1:- Calculate Initial Void ratio (For loose /Un-compacted material)

    It can be calculated in lab, lets assume initial void as 60%

Step 2:- Decide Compacted thickness of layer to be Achieved

    This value is taken from SSR item description 

    lets assume as 50 mm

step 3:- Expected quantity to be filled by filler material

    This depends on binder quantity or dosage, 

    lets take it 25%

step 4:- Assumed compaction due to Vehicular Live Load, which will be applied on compacted thickness

    Assume as 10%

step 5:- Calculation for loose thickness factor

        It can be calculated using formula below

$$\text{Loose Thk factor}=\left({1-Q_f}\over {v_i}\right) + {C_{LL}}\times \left({1-Q_f}\over {v_i}\right)$$

        Q_f = Quantilty of filler materials in %

        V_i = initial void ratio

        C_LL = Assumed compaction due to Live Load traffic

Loose thickness factor for above values = 1.375

step 6:- Calculation of Loose thickness

    Loose thk = Loose thk factor X Compacted thk

    Loose thk = 1.375 X 50 = 68.75 mm

Note:- In step 4, we have assumed 10% FUTURE compaction due to Vehicular live load, does that mean we have to specify some % deductions to be made from quanity of work in running account bills to account for future settlment in road layers.

Suggestions or Improvements will be appreciated 👍