Bituminous Concrete is required to lay any asphalt road like BM, DBM, BC etc with Quality control specifications like temperature, aggregate, JMF limits. We described temperature control of asphalt mix, aggregate quality, JMF limit and frequency test on Asphalt road.
What are the specification required for laying Bituminous concrete.
QUALITY CONTROL ROLE IN ASPHALT ROAD CONSTRUCTION
1. Temperature of Asphalt mix in Asphalt road construction procedure
|Production||140 – 160 degree celcius|
|laying||minimum 130 degree celcius|
|rolling||minimum 80 degree celcius|
|Production||145 – 165 degree celcius|
|laying||minimum 135 degree celcius|
|rolling||minimum 85 degree celcius|
|Production||150 – 165 degree celcius|
|laying||minimum 140 degree celcius|
|rolling||minimum 90 degree celcius|
|Production||160 – 170 degree celcius|
|laying||minimum 150 degree celcius|
|rolling||minimum 100 degree celcius|
2. Thickness of Asphalt mix Layer as a DBM
The thickness of single Asphalt mix layer as a Dense bituminous macadam shall be minimum 50 and maximum 100 mm.
3. Quality of Coarse Aggregate for Asphalt mix
Coarse aggregate, which are going to be used in Asphalt mix must be clean, hard, durable and free from dust and organic impurities.
Here we are describing important specific limits for aggregate physical strength to
be used in DBM.
Fine aggregate, which is going to be used in asphalt mix should be between 2.36 mm and 0.075 mm in size. It must be crushed rock not river sand. Fine aggregate shall be clean, hard, durable and free from dust and organic impurities.
Some important quality of Fine aggregates for Asphalt mix
1. Sand equivalent value shall be not less than 50.
2. Plasticity index shall not be more than 4.
5. Quality of Mineral Filler for Asphalt mix
As a mineral filler we can use Cement, Hydrated lime or Rock dust in Asphalt mix.
Mineral filler shall be fulfill these gradation requirement
6. Gradation Limit for Aspahlt mix as a Dense bituminous macadam ( DBM ) in Asphalt road construction procedure
As per nominal aggregate size gradation result shall be fall in these limit –
* Nominal aggregate size is the largest sieve size on which any of the aggregate particle is retained.
** These bitumen content has given based upon 2.7 aggregate specific gravity, If you are using aggregate which has more specific gravity than 2.7 than bitumen content can be reduced proportionally.
7. Requirements of the Asphalt Mix in Asphalt road construction
8. Voids in Mineral Aggregate in Asphalt Mix
9. Permissible Variation in Actual Mix from JMF “Job Mix Formula”
Field density of Asphalt mix layer as a Dense bituminous macadam shall not be less than 92 % of the density we got on the date of laying based on Theoretical maximum specific gravity ( Gmm ).
11. Frequency Test / Control Test on DBM Asphalt Road in Asphalt road construction
|Test Description||Number of Test|
|Aggregate Impact value / Abrasion value||one test / 350 cum of aggregate / Source|
|Flakiness and Elongation Index||one test / 350 cum of aggregate / Source|
|Soundness test||one test / Source|
|Water absorption test||one test / Source|
|Sand equivalent test||one test / Source|
|Plasticity index||one test / Source|
|Polished stone value||one test / Source|
|Mix Gradation||one set of individual and mixed agg / 400 tonnes(minimum-2)|
|Marshal stability and void test||Three test / 400 tonnes (minimum 2)|
|Binder content||one test / 400 tonnes (minimum 2)|
|Rate of spread of mix||Every 5th truck|
|Density of compacted layer||One test per 700 sq.m.|