Quality Control of Asphalt Concrete

Quality Control of Asphalt Concrete

Asphalt concrete quality is mainly reflected in the stability and flow value of the two indicators, which reflects the asphalt concrete high temperature stability and resistance to deformation capacity, and raw material quality and production process control is closely related. Therefore, to control the quality of the mixture should be from the following aspects.

Quality control of raw materials

Asphalt concrete raw materials include: coarse aggregate, fine aggregate, mineral powder, asphalt and so on.

1. Coarse aggregate Aggregate is a coarse aggregate with a grain size greater than 2.36mm. Frames are formed in asphalt concrete to maintain stability. So its mechanical properties should meet the requirements and have a good shape. Needle sheet content is low, no weathering, no impurities, surface roughness with high internal friction.

2. Fine aggregate Fine aggregate is the size of 0.075 to 2.36 in between the large sand, stone chips and so on. In appearance should be clean, no weathering, no impurities, and have the appropriate particle composition and possible edges and corners to increase the interlocking effect between the particles and reduce the inter-aggregate pore.

3. Asphalt asphalt should be checked before use penetration, ductility, softening point and other indicators are consistent with the technical requirements of traffic asphalt. In the choice of asphalt on the use of asphalt pavement to take into account the high temperature stability and low temperature crack resistance. As the higher the grade number of asphalt, the greater the penetration, the lower the consistency, so according to the different levels of road surface selection of different types of asphalt, the surface layer with a thinner asphalt to improve the surface layer of crack resistance; Thicker asphalt to improve rutting resistance. The wax content should be controlled below 3%, wax content is too high, the pavement of high temperature stability and low temperature crack resistance have an impact, will also affect the adhesion of asphalt.

4. The role of filler The formation of asphalt with asphalt mortar to increase the adhesion of asphalt mixture. Filling with the correct or not, is directly related to asphalt mixture in the free asphalt. If the presence of free asphalt, asphalt will reduce the asphalt mixture of adhesive force, and the phenomenon of pan-oil phenomenon. Filler should meet the fineness requirements, no impurities. In the use of bags of mineral powder occasions, have storage space, rain and moisture, ventilation and drying, to prevent the mineral powder rain damp. Has been caking damp slag firmly can not be used. Sometimes in order to improve the adhesion of asphalt, the need to add additives such as lime, slaked lime must be digested thoroughly, fineness to meet the requirements. Otherwise it will play the opposite effect, affecting the quality of asphalt mixture.

Control of the Primary Distribution of Cold

Cold material with the ratio of the initial allocation is required to calculate the cold storage bin ingredients of the motor speed and the height of the material door to determine the amount of material delivery to meet the continuous production of mixing station needs. If the primary cold distribution is not accurate, there will be expected to be expected and flash phenomenon, affecting the mixing station productivity and quality of the mixture. Test personnel should keep abreast of yard feed situation, timely sampling and screening, analysis of relevant data. According to different raw materials to adjust the primary distribution to ensure that the stability of mixing production and continuity.

Weighing measurement control

After drying, the aggregate is sieved through a vibrating sieve and enters into a hot silo of different particle diameters. Test personnel must be sieved after the screening of aggregate screening, in order to determine the thermal silo of different particle size ratio of the amount of material. Must be stable in the primary cold material when the hot silo screening, in order to ensure the accuracy of screening tests. Through the screening test analysis of the production mix ratio curve should be in the target mix ratio curve within the allowable range, in line with technical standards.

Temperature control

For batch asphalt mixing plant, the heating temperature of asphalt is controlled at 150 ~ 170 ℃, the temperature of aggregate is 10 ~ 20 ℃ higher than that of asphalt, and the factory temperature of the mixture is 140 ~ 165 ℃. If the temperature is not enough there will be flowers, the temperature is too high asphalt will be charred. Asphalt mixture of factory temperature directly affects the quality of paving and rolling. In the production process to always detect the mixture temperature, and notify the operator, in order to adjust according to the actual situation.

Mix the mixture

Mixing in the uniform mixing, requiring all the mineral particles were all wrapped asphalt, there is no uneven package phenomenon, no flower material, no agglomeration or segregation phenomenon. Usually the mixing time of the asphalt mixture is dry mixing for 5 seconds and wet mixing for 45 seconds. SMA mixture required dry mix for 5 seconds, wet mix for at least 60 seconds. The mixing time can not be arbitrarily reduced to increase the productivity. Mixing blades and liner in the mixing tank should be replaced after wear to ensure the orderly flow of the mixture in the mixing tank, even mixing, improve mixing quality of the mixture.

Monitoring of finished materials

Quality inspection personnel for each batch of finished material should be checked, flower material, segregation, temperature is not enough or over-temperature mixture to be discarded. Find the problem in time feedback to the operator, in order to make targeted adjustment processing. Test personnel sampling the mixture every day, according to experimental procedures for experimental analysis, and experimental data feedback to the operator, found the problem in a timely manner to resolve.