On quality control of mixture of asphalt mixing plant approach

On quality control of mixture of asphalt mixing plant approach

1. quality control of asphalt mixture method

1.1 quality control of raw materials

1.1.1 asphalt

According to road level, climatic conditions, type of road, traffic and select different sizes, summer, high speed, heavy duty, long slope pavements should select the bitumen viscosity and vice versa, cold climate, small traffic volume you can select the viscosity of asphalt. Each batch of asphalt should be carried out according to the technical specifications of Highway asphalt pavement construction, sampling inspection, management of asphalt asphalt should be stored separately from different sources, cannot be intermixed so as to prevent pollution; the storage temperature during not more than 170 ° c, not less than 150 ℃; when stored at low temperatures for a long time.

1.1.2 aggregates

Aggregate asphalt concrete skeleton, is a major factor affecting the strength of asphalt concrete, material selection process, reducing the variability of aggregate gradation, aggregate gradation control key hole is set to Crusher control mesh in order to guarantee the stability of aggregate gradation.

Aggregate shape close to the cube, edges to make mixing asphalt mixture with a good mechanical properties and high temperature stability, so be careful not to use needle-like aggregates. Aggregates the sediment can also affect aggregate and asphalt adhesion performance and the stability of the mixture, so in front of the mixing mixture, to clean the clay aggregates, stacked in the yard of the aggregates to be covered to prevent dust pollution.

1.1.3 mineral powder

Mine powder on asphalt mixed material of aggregate cemented up with important role, is not simple of fill role, in same of asphalt dosage Xia, mine material of surface product more big, formed of asphalt film more thin, structure asphalt share more big, asphalt mixed material stick poly force more strong; so mine powder must is limestone or magma rock in the strong base sex rock mill broken Hou of mine powder, processing Qian to guarantee original stone of clay was clear, save Shi to note waterproof, and moisture.

1.2 proportion control

Proportioning design of asphalt mixture, should follow the provisions of the technical code for construction of Highway asphalt pavement of hot asphalt mixture ratio design of target mixture ratio, production design and production with more than three stages to determine the mineral aggregate gradation optimum asphalt content. Mix design is reasonable, directly affects the quality and service life of asphalt pavement construction.

Mine material of level distribution design to as reduced design level distribution and actual level distribution Zhijian of differences, main through on concrete mixing plant cold material warehouse of belt speed, and cold material of flow for records research, determine motor speed and Shang material flow between of frequency relationship, in production and mix business mixed material Shi, on can better of control in level distribution range within, improve tie than precision, reduced deviation.

1.3 mix temperature control

Asphalt mixture mixing temperature determines the viscosity of bitumen, asphalt has high liquidity at high temperatures to completely wrap aggregates do not appear white. But the mixing temperature is too high, aging of asphalt will be very serious, adhesion of asphalt, asphalt and aggregate adhesion, the lower pavement segregation after the more serious. But if the mixture's temperature is too low, it will affect the spreading and compaction quality, caused by uneven mixing and compaction problems. Hot-mixed asphalt mixture mixing temperature is 130~160℃, which modified asphalt mix temperature should be higher than the average temperature of asphalt mixture mixing to improve 10~20℃, modified asphalt mixture in the storage temperature should be less than 10 ℃, the temperature should be higher than the asphalt temperature of aggregates 10~30℃, material storage silos may not exceed 72 hours.

In addition, it also needs under different weather conditions, different construction adjustment of the exit temperature of the mixture. To compensate for dump trucks, Paver's absorption of heat, generally the first pot storage temperature 10 degrees centigrade higher than normal, at noon or when the construction of higher summer temperatures can be lower than normal temperature 10℃.

1.4 transport and discharge control

From the mixing plant when feeding on the machine to the pallet truck, each discharging a mixture and move the car to reduce the segregation of coarse and fine aggregates, and minimize the storage silo fall falling margins.

When shipping times in half an hour or more, or temperatures below 10 c, the lorry with tarpaulin covered insulation.

In the course of continuous paving, lorry stopping in front of the paver 10-30cm shall not impact paver, lorry unloading process should put it in neutral and push for paving the way forward.

Have segregation or condensation cannot be crushed shell, clumps, and transportation vehicles when discharging the mixture left in car, below the stipulated laying temperature or wet mixture, should be abandoned, and may not be used for road paving.

2. the mixing process of quality testing

2.1 Visual inspection

Mixed staff through the mix observation to check for the appearance of concrete mixing plant exception occurs.

If every day the first few asphalt concrete mix is substandard waste, then check aggregates and asphalt heating fails to reach a specified temperature; staff entering the dryer can be reduced by the aggregate amount, improve the flame temperature to solve the waste problem.

If there is a white material, show that aggregate temperature is too low, mixing time is short, or fine number; the appropriate solution would be to increase aggregate heating temperature, increase the mixing time of mixture, or reduce the number of fines.

If the mixture colour is dark, indicating heating temperature is too high, caused by aging; this should strictly control the heating temperature of the asphalt.

2.2 temperature test

Temperature test of asphalt mixture should be once every half an hour, generally on the wheel with the insertion thermometer measurements, using metal bars from the car side reserve hole into mixture, depth at least 15cm, mixture immediately after contact with the metal rod to measure temperature. If the temperature is too high or too low, to adjust the mixing process.

2.3 sampling experiment

According to the nominal maximum size of aggregate asphalt mixture, fine-grain asphalt mixture sample size of not less than 4kg; particles in asphalt mixture sample size of not less than 8kg coarse-grain asphalt mixture, sample size of not less than 12kg; extra coarse asphalt mixture, sample size of not less than 16kg. Of hot-mix asphalt mixture sample at a time, you must use thermometers to measure temperature, accurate to 1 c.

Asphalt sampling is random, and full representation to check mixing quality, such as asphalt and mineral aggregate gradation for the purpose, one at a time from the mixer or promotion in the sample below, shall not be repeated sampling mixed before use.

Transportation cars take on asphalt mixture sample, which might be charging half of car drive to the car after car, using shovels from different sampling at 3 different heights, then appropriate mixing evenly mixed together with a hand shovel, take out the required number. When the car arrived at the construction site after sampling should be removed after half the car out from different sampling at 3 different heights.

The results after sampling, the substandard Office to find out the specific reason, to remedy the situation.