Highway mineral powder function

The main chemical components of mineral powder are CaO、SiO2、Al2O3 and Fe2O3, etc . Mineral powder are used as tamping or filler in asphalt mixture , it’s able to reduce the voids of asphalt concrete , cut the consumption of cement , improve the workability of concrete, and lower the heat of hydration. Besides, the mixture of mineral powder and asphalt can form asphalt mortar, which can improve the strength and stability of asphalt concrete. Powder-oil ratio is commonly used to represent mineral powder content, the greater the powder-oil ratio, the stronger high temperature rutting-resistance of asphalt concrete ,The smaller the powder oil ratio, the better the low temperature cracking-resistance of concrete. Concrete mixed with grinding fine mineral powder can delay the hydration rate of cementitious materials, prolong the setting time of concrete, this property is favorable for the transportation and construction of concrete in high temperature season.

The highway mineral powder fineness regulations

《Technical specification for construction of highway asphalt pavement》JTG F40-2004 makes provisions on the asphalt concrete mineral powder fineness, namely the particle size distribution, as specified herein.

For highway, arterial highway: mineral powder particle size less than 0.6mm should be 100%, less than 0.15mm should account for 90% - 100%, smaller than 0.075mm should be accounted for 75% - 100%.

For other grade highway, slag powder particle size less than 0.6mm should be 100%, less than 0.15mm should account for 90% - 100%, smaller than 0.075mm should account for 70% to 100%.

Note: see "technical specifications for construction of highway asphalt pavement"

Equipment recommendation

MTW European-type mill

[Application area]: MTW series Europeanism Trapezium mill is widely used in the grinding process of product materials in metallurgy, building materials, chemical industry.

[applicable material] : quartz, feldspar, calcite, talc, barite, fluorite, tombarthite, marble, ceramic, bauxite, phosphate ore, zircon sand , slag , water slag and so on.

LM vertical roller mill

[Application area]: suitable for cement, electric power, metallurgy, chemical industry, mineral industry material mill.

[Suitable material]: cement, coal, feldspar, calcite, talc, fluorite, iron ore, copper, phosphate ore, graphite, quartz, slag, etc.

Small industry knowledge

1. In the asphalt concrete, Isn't mineral powder the finer the better?

The size of the particle size can be followed, not the smaller the better. The general pass rate for particle size>0.15mm should be 90-100%.
Too finely grinded, on the one hand, led to high energy consumption and low economy, on the other hand, make the mixture too hard, as a result, easy to crack when applied to the road.

2 . Why “mineral powder” recycled from asphalt concrete mixing is prohibited in highway construction?

(1) The mineral powder is required alkaline while retrieving powder is not exactly.
(2) The mineral fineness requires a pass rate of 75% for particle size>0.075mm but the recovery is very difficult to achieve and is not stable.
(3) Mineral powder refers to the pure powder grinding from high-hardness rock like limestone or magmatite while the recovery Contains a certain amount of soil and other impurities.
(4) The density of mineral powder should be not less than 2.5t/m3 while the recovery is not up to the standard.
(5) The water content of the mineral powder shouldn’t be more than 1% while the recovery has a big water content, with solid block.

3. What are the functions of limestone powder and blast-furnace slag when applied to asphalt concrete?

Limestone powder belongs to inert mineral admixture in materials science, it’s available in asphalt pavement , improving asphalt viscosity and strength, it can also be used in railway and highway construction, playing the filler role.
High activity of blast furnace slag powder, slag powder can fully or partially replace limestone powder, reduce the bitumen-aggregate ratio of the asphalt mixture. When completely replaced, the void fraction of mixed aggregate reaches minimum and the stability reaches the highest as well as the good low-temperature ductility and affinity for asphalt.
Note: Specifications for Design of Highway Asphalt Pavement（JTGD50-2006）
Technical specification for construction of highway asphalt pavement(JTG F40-2004）