Very often road making supervisors whose task is to lay bitumen-concrete mix want to know the amount of the mix to order because they do not want to have by the end of the process a truck with cold asphalt without knowing how to get rid of it.
The question is – how to calculate the amount of asphalt?
First of all we should take into account the type of bitumen-concrete mix.
The largest amount – about 25.5kg per 1cm of thickness – will be for stone-mastic asphalt mix (SMAM). This can be explained by the best possible continuous curve of granularmetric composition of SMAM (by a high degree of filling the frame with aggregate grains of different size).
The amount for 1 m2 of color asphalt is 25kg (1cm thick).
The amount for coarse aggregate mix is less – about 24kg per 1cm, because their granularmetric curve is discontinuous, that is the space between large grains is filled with sand, but not with small fractional stone screening dust, as it is in the case of SMAM.
For sand bitumen-concrete mix the amount is 23.5kg, as the density of sand is lower than that of crushed stone.
The above given figures are not precise, they can vary upward or downward in accordance with the type of crushed stone or sand you use, as the density of mineral materials and their strength physical-chemical properties are different due to the place of their extraction (open-cut mine).
Thus if your plan is to surface a road section with a total area 1000 m2, 5cm thick with bitumen-concrete mix of SMA type your calculation shall be according to the simple formula:
25 kg * 5 cm = 125 kg = 0.125 t – the amount of bitumen-concrete mix (bcm) necessary to cover 1m2 of surface.
In our case the surface area is 1000m2, so multiplying this area by 0.125t we obtain 125t of bcm – the desired amount of mix.
It turns out that 1 ton of bitumen-concrete mix is enough to cover 8 square meters of surface, later on, the thickness of the layer increasing, the surface area will decrease.
PS The aim of this article is not to give a conclusive table of the amount of asphalt in relation to the type of mix and thickness of the layer. All we wanted was to show in simple words and using a few figures what the amount of asphalt depends upon and how it can be expressed in rough estimation.I hope we managed to do this.