I.The role of mineral powder
The main chemical components of the mineral powder are the CaO, SiO2, Al2O3, Fe2O3, and so on.
Mineral powder to fill roles in asphalt mixture in order to reduce the voids of asphalt concrete, sometimes referred to as filler, reduce the dosage of cement hydration, improve work performance, reduce the heat of hydration, mineral powder and the asphalt together form the asphalt cement and improves the strength and stability of asphalt concrete.
Content of mineral powder is represent by filler to bituminous ratio, the higher proportion of filler to bituminous ratio, the high-temperature rut resistance of asphalt concrete is usually stronger,the filler to bituminous ratio is relatively small, would benefit the low temperature crack resistance of the concrete. Concrete mixed with ultra-fine ore powder to slow the hydration of cementitious material, prolong the setting time of concrete, the nature is good for transport and construction of concrete in high temperature season.
II. Asphalt concrete with mineral powder fineness regulations
JTGF40-2004－ «the technical code for construction of Highway» for the asphalt pavement of asphalt concrete powder fineness, particle size distribution provides as follows:
For highways, arterial roads: ore particle size less than 0.6mm , should be take amount of 100%, less than 0.15mm should 90%-100%, less than 0.075mm should 75%-100%.
For other highway: ore particle size should be less than 0.6mm should take 100%,less than 0.15mm should take 90%-100%, less than 0.075mm should take 70%-100%.
Note: Please refer to «the technical code for construction of Highway».
III. The recommendation of facility :
GK new Raymond mill, LM series vertical mill.
IV. Industry knowledge :
- More fine mineral powder in asphalt concrete is not the better.
Particle size has standards to follow, not the finer the better. Generally the pass rate for 90-100% should less than 0.15mm .
Powder particle size too small, on one hand will consume high power, low economical performance , on the other hand is applied in the pavement of the road which will make the mixture is too hard, easy to crack.
- why the mixture of asphalt concrete recovery “powder” is not recyclable in the highway in the construction?
(1) the highway use mineral powder is alkaline, and recycling mineral powder is not all.
(2) mineral powder fineness required by 0.075mm, and the content more than 75%, recovery is difficult to reach without stability.
(3) mineral powder with limestone or lava rock in the Foundation rock of finely ground pure mineral powder, while the collection contains a certain soil and other impurities.
(4) mineral powder density requirement of not less than 2.5T/M3, but the standard of recovery and can not up to .
(5) water content of the ore requires not more than 1%, but the recycled is more moisture.
3.What are the application of limestone powder and granulated blast-furnace slag powder respectively in asphalt concrete ? What are the standards?
Limestone powder materials belonging to inert admixture used in asphalt pavement, to improving the asphalt viscosity and strength, can also be used in the railways and road construction, and play a role in filler .
High activity of blast furnace slag powder, ground granulated blast furnace slag powder can be completely or partially replacing lime stone powder, reduce oil stone ratio of asphalt mixture, completely replace the mixture air voids when the smallest, highest stability, good ductility at low temperature, good affinity with the asphalt.